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The maintenance of a stable equilibrium in the conditions inside the body
What key features do mammalian neurones have?
- Cell Body:
- cytoplasm with large amounts of endoplasmic raticulum and mitochondria ~ for production of neurotransmitters
- Dendrons:Transmit toward cell body
- Split into dendrites
- Axons:Transmit away from cell body
What types of neurone do we have and what do they do?
- Sensory: impulse from sensory receptor to relay or motor neurone, or brain
- Relay: transmit impulses between neurones.
- Motor: impulse from relay or sensory neurone to an effector ~ muscle or gland
What does a sensory neurone look like?
What does a motor neurone look like?
What does a relay neurone look like?
How are some neurones specialised in order to transmit an impulse much faster?
- Myelin sheath
- Made of Schwann cells
- Nodes of Ranvier in between
What are the features of a sensory receptor?
- Specific yo certain type of stimulus
- Act as a transducer ~ convert stimulus to nerve impulse
What type of sensory receptor detect mechanical pressure and are found in the skin?
Describe their structure.
- Pacinian Corpuscles
How do pacinian corpuscles work?
- 1. In resting state it has a resting potential since stretch-mediated sodium ion channels don't let Na+ through
- 2. Pressure applied changing shape of pacinian corpuscle, stretching membrane around neurone
- 3. Sodium ion channels widen and Na+ diffuses into neurone
- 4. Influx changes membrane potential ~ depolarised. Results in generator potential.
- 5. Generator potential creates action potential, passing along neurone.
When is a neurone membrane polarised?
- Resting potential
- Outside is more positive than inside of axon
How is resting potential achieved?
- Sodium-potassium pump
- 3 sodium ions pumped out2 potassium ions pumped in
- Result: more Na+ outside and more K+ inside
- Potassium ions able to diffuse back out via potassium ion channels (down electrochemical gradient)
- Sodium ions (mainly) can't diffuse back in since gated sodium ion channels are shut
- Result: More positive ions outside cell, resting potential across membrane of -70mV
When is a neurone membrane depolarised?
- Stimulus detected by sensory receptor
- Potential difference across membrane reversed
How does an action potential occur?
- 1. Polarised/Resting potenital: Most sodium ions kept out, sodium (Na+) voltage gated ion channels shut.
- 2. Depolarisation: Stimulus triggers some Na+ voltage gated ion channels to open, allowing Na+ ions in down electrochemical gradient. Inside becomes less negative.
- 3. Depolarisation: change in charge triggers more Na+ gated channels to open ~ positive feedback
- 4. Depolarised/Action Potential: Potential difference reaches +40mV voltage gated sodium ion channels close, potassium voltage gated ion channels open.
- 5. Repolarisation: Potassium ions move out, reducing charge, resulting in inside becoming more negative than outside
- 6. Hyperpolarisation & Repolarised: Initially lots of potassium ions move out resulting in more negative than resting state. Voltage gated potassium channels now close. Sodium potassium pump then caused sodium to move out, potassium to move in, and it to return to resting potential
How is an action potential propagated?
- Initial stimulus causes triggered action potential
- First region of axon depolarised
- Once sodium ions are inside the axon, they are attracted by negative charge ahead and concentration gradient ~ diffuse further along
- Depolarisation triggered in next section
What is the period of time after an action potential known as and what is it for?
- Refractory periodVoltage gated sodium ion channels remain closed ~ preventing movement of sodium ions into axon
- Prevents propagation of another action potential either backwards or forwards
- Ensures action potentials are unidirectionalAnd occur as discrete impulses (don't overlap)
Why do myelinated axons conduct faster?
- Depolarisation can only occur at nodes of Ranvier where sodium ions can pass through channels
- Action potential can jump from node to node ~ Saltatory conductionMore energy efficient since repolarisation requires ATP
What other factors affect speed of action potential?
- Axon diameter: bigger axon = faster
- - less resistance to flow of ions in cytoplasm
- Temperature: higher temp = faster
- - ions diffuse faster
- - up to 40°C
What is the all or nothing principle?
- Threshold value must be achieved in order to trigger action potential (which are always the same)
- Stimulus must be large enough to reach this value, or no action potential will occur
- A strong stimulus will produce more frequent action potentials
What are the key features of a synapse?
- Synaptic cleft - space between
- Presynaptic neuronePostsynaptic neuroneSynaptic knob - contains many mitochondria and endoplasmic reticulum for neurotransmitter production
- Synaptic vessicles - contain neurotransmitter released by exocytosis
- Neurotransmitter receptors on postsynaptic membrane
What two types of neurotransmitter are there and give examples?
- Excitatory:Result in depolarisation in postsynaptic neurone
- If threshold is reached an action potential generated
- Result in hyperpolarisation of postsynaptic neurone
- Prevents action potential
- GABA ~ gamma-aminobutyric acid
How is an impulse transmitted across a synapse?
- 1. Action potential reaches end of presynaptic neurone
- 2. Depolarisation causes calcium ion channels to open
- 3. Calcium ions diffuse into knob
- 4. Causing vesicles to fuse with presynaptic membrane, releasing neurotransmitter into cleft
- 5. Neurotransmitter diffuses across cleft
- 6. Binds with receptors on postsynaptic membrane
- 7. Results in sodium ion channels opening
- 8. Sodium ions diffuse in
- 9. Action potential triggered & impulse propagated along axon
- 10. Any neurotransmitter left in cleft is removed
Explain transmission across cholinergic synapses
- Neurotransmitter: acetylcholineHydrolysed by acetylcholinesterase, found also on postsynaptic membrane
- Forms choline & ethanoic acidProducts take back to presynaptic knob to reform neurotransmitter using ATP
What are the roles of synapses?
- Ensure unidirectional impulses~ neurotransmitter receptors only on one side
- Allow one impulse to go to multiple neurones via multiple synapses to create number of simultaneous responsesNumber of neurones can feed to one postsynaptic neurone to create one single result
What is summation and what types are there?
- Released neurotransmiiter must build up in order to reach threshold in some synapses
- Spatial summation:-number of presynaptic neurones connect to one postsynaptic neurone
- -each release neurotransmitter which builds up
- Temporal summaton: -single presynaptic neurone
- -releases neurotransmitter a number of times over short period before it builds up enough
Which two structural systems are the mammalian nervous system organised into?
- Central Nervous System (CNS) ~ brain & spinal cord
- Peripheral Nervous System (PNS) ~ neurones connecting CNS and rest of body
Which two functional systems is the nervous system divided into?
- Somatic ~ conscious control
- -input: sense organs
- -output: skeletal muscles
- Autonomic ~ subconscious
- -works constantly
- -input: internal receptors
- -output: smooth muscles, glands, cardiac muscle
- -divided into sympathetic & parasympathetic nervous system
What do the sympathetic and parasympathetic nervous systems do?
- Sympathetic:-generally speeds things up
- -'fight or flight'
- -noradrenaline-eg. increase in heart rate
- Parasympathetic:-generally slows things down
- -relaxing responses
- -acetycholine-eg. decrease in heart rate after activity
What are the five main areas of the brain? (needed for course)
- Medulla oblongata
- Pituitary gland
What is the cerebrum?
- Interprets sensory info wrt info stored from previous experiences
- Coordinates all voluntary responses ~ learning, memory, personality, conscious thought
- Some involuntary responses
- Highly convoluted ~ increased SA
- Split into left and right hemispheres
- Outer layer called cerebral cortex
- Sizes of sensory and motor areas proportional to function
What does the cerebellum do?
- Controls unconscious functions such as posture, balance, and non-voluntary movement
- Does not initiate movement, but coordinates it
- Relays info to cerebral cortex for motor control
- Damaged ~ jerky movement
What is the medulla oblongata?
- Contains many important regulatory centres
- Control reflex activities such as ventilation and heart rate ~ (Autonomic control)
- Controls swallowing, peristalsis, coughing
What is the hypothalamus?
- Main control region for autonomic nervous systemTwo centres - sympathetic and parasympathetic
- Controls behaviour patterns ~ feeding, sleeping, aggression
- Monitors blood plasma composition ~ water, glucose (has rich blood supply)
- Produces hormones
- Regulatory centre for temperature
What is the pituitary gland?
- At base of hypothalamus
- Two sections:
- -Anterior pituitary (front) ~ six hormones including FSH
- -Posterior pituitary (back) ~ stores & releases hormones produced by hypothalamus, e.g. ADH
What is the reflex arc?
- Sensory Neurone
- CNS - Relay Neurone
- Motor Neurone
What is the knee-jerk reflex?
- Tap below kneecap
- Leg normally extends once
- Tested by doctors
- Absence of reflex indicates nervous problems
- Multiple oscillation can indicate cerebellar disease
What is the blinking reflex?
- Involuntary blinking of eyelids
- ~ Corneal reflex
- Cornea is stimulated
- Purpose- keep cornea safe
- ~Optical reflex
- Loud sounds and bright light
- Purpose - protect retina and lens
- Doctors test for blink reflex in unconscious patients
- -if present, lower brain stem is functioning so cannot be diagnosed as brain-dead
Why are reflexes important to survival?
- Purpose: prevent or minimise harm to the body
- Prevents brain being overloaded since they are involuntary and brain is not involved
- Don't need to be learned
- Fast reflex arc is short with only two synapses
- Everyday actions eg not falling over
What types of muscle are there?
- Skeletal: movement
- Cardiac: heart
- Smooth: involuntary, found in walls of hollow organs such as stomach, and blood vessels, digestive tract etc.
What are the features of skeletal muscle for the following points?
- Fibre appearance: striated
- Control: conscious
- Arrangement: regular so muscle contracts in one direction
- Contraction speed: fast
- Length of contraction: short
- Structure of fibres: tubular and multinucleated
What are the features of cardiac muscle for the following points?
- Fibre appearance: specialised striated
- Control: involuntary
- Arrangement: cells branch & interconnect for simultaneous contraction
- Contraction speed: medium
- Length of contraction: medium
- Structure of fibres: fainter striations, branched, uninucleated
What are the features of smooth muscle for the following points?
- Fibre appearance: non-striated
- Control: involuntary
- Arrangement: irregular, cells contract in different directions
- Contraction speed: slow
- Length of contraction: relatively long time
- Structure of fibres: spindle shaped, uninucleated
Describe the structure of muscle fibres (skeletal muscles)
- Bundles of muscle fibres enclosed within plasma membrane ~ sarcolemma
- Longer than normal cells
- Many individual embryonic muscle cells fuse together:
- -makes them stronger
- Shared cytoplasm ~ sarcoplasm
- Sarcolemma folds inwards - to spread electrical impulses
- Many mitochondria
- Sarcoplasmic reticulum contains calcium ions throughout fibre
What are myofibrils?
- Within muscle fibres
- Long cylindrical organelles
- Lie parallel
- Made of actin (thinner, two strands twisted together) and myosin (thicker filament, long rod shaped fibres with heads to one side)
Why do myofibrils have a striped appearance?
- Alternating light and dark bands
- Light: region where actin & myosin filaments don't overlap (I-band)
- Dark: presence of thick myosin filaments, edges particularly dark where actin & myosin overlap (A-band)
- Z-line: centre of light band
- -distance between 2 Z-lines is one sarcomere
- -shortens on contraction
- H-Zone: lighter region at centre of dark band
- -only myosin
- -decreases on contraction
How is muscle contraction described?
- Actin and Myosin filaments slide past eachother
- Sliding filament model
What happens during a contraction?
- Light band ~ narrower
- Z-lines ~ closer together
- H-zone ~ narrower
Describe the structure of myosin
- Globular heads, hinged allowing backward/forward movement
- Head has binding sites for actin & ATPTails form the filament
Describe the structure of actin
- Binding sites for myosin heads ~ actin-myosin binding sites
- Resting State: blocked by tropomyosin held in place by protein troponin, cannot slide
- Contraction: actin-myosin cross bridges form
- -myosin heads flex
- -pulling actin filament along myosin filament
- -myosin detaches, head returns to original angle using ATP
- -myosin reattaches further along
During a contraction, what happens at the neuromuscular junction?
- Many neurotransmitter junctions ~ ensure simultaneous contraction
- Motor unit ~ all muscle fibers supplied by one neurone, if strong force is needed many units are stimulated
- Action potential arrives
- Calcium ion channels open and ions move into knob
- Vesicles fuse to presynaptic membrane and release acetylcholine
- Diffuses across cleft & binds to receptors on postsynaptic membrane (sarcolemma)
- Sodium ion channels open causing depolarisation
- Neurotransmitter broken down and recycled
During a contraction, what happens to the sarcoplasm?
- Depolarisation of sarcolemma travels into muscle via T-tubules in contact with sarcoplasmic reticulum
- Action potential stimulates release of calcium ions from sarcoplasmic reticulum (channels open)
- Calcium ions bind to troponin causing change in shape
- Pulls tropomyosin away leaving actin-myosin binding sites free
- Actin-myosin bridges form
- Myosin head flexes pulling actin filament along
- ADP bound to myosin head is released
- ATP molecule can now bind to myosin head
- -Causes head to detach from filament
- Calcium ions activate ATPase activity of myosin, hydrolysing ATP to ADP & phosphate
- -releases energy for myosin head to return to original position
- Cycle repeated for as long as muscle is stimulated
Energy supply during contraction
- Hydrolysis of ATP to ADP and phosphate
- Required for:
- -movement of myosin head
- -enable sarcoplasmic reticulum to actively reabsorb calcium ions from sarcoplasm
What are the three main ways ATP is generated?
- Aerobic respiration:
- -regenerated from ADP by oxidative phosphorylation
- -takes place inside mitochondria
- -requires oxygen
- -long periods of low intensity exercise
- Anaerobic respiration:-no oxygen
- -ATP made by glycolysis but pyruvate (also produced) is turned to lactate (lactic acid)
- -builds up resulting in muscle fatigue
- -short periods of high intensity exercise
- Creatine phosphate:-stored in muscle
- -acts as reserve supply of phosphate
- -available immediately to combine with ADP to form ATP
- -generates ATP rapidly
- -but store of phosphate quickly depleated
- -short bursts of vigorous exercise (e.g. tennis serve)
- -creatine phosphate stores replenished while relaxed
What is an endocrine gland?
- Group of specialised cells
- Secrete chemicals ~ hormones
- Directly into bloodstream
(What is an exocrine gland?)
- Secrete chemicals through ducts into organs or to surface of body
- e.g digestive
What happens to the hormone, beginning before secretion?
- Gland stimulated: change in blood concentration of a substance, or as the result of another hormone or nerve impulse
- Hormone secreted
- Diffuses out of blood
- Binds to specific receptors on/in target cells
What two types of hormone are there?
- Steroid hormones:
- -lipid soluble
- -bind to receptors inside target cell (cytoplasm or nucleus)
- -hormone-receptor complex acts as a transcription factor
- -facilitates or inhibits transcription of specific genes
- -e.g oestrogen
- Non-steroid hormones:
- -bind to receptors on target cell surface membrane
- -triggers cascade reaction mediated by second messengers
- -e.g adrenaline
Describe the positioning, structure, and function of the adrenal glands
- Located: top of each kidney
- Surrounded by caspule
- Adrenal cortex: outer region, hormones vital to life ~ e.g cortisol, adolsterone
- Adrenal medulla: inner region, non-essential hormones ~ e.g adrenaline
What hormones doe the adrenal cortex secrete and what are their functions?
- Glucocortinoids: including cortisol and corticosterone
- - cortisol regulates metabolism, regulated blood pressure and cardiovascular function in response to stress
- - corticosterone works with cortisol to regulate immune response, suppress inflammatory reactions
- - release controlled by hypothalamus
- Mineralocortinoids: aldolsterone
- - helps control blood pressure by maintaining salt/water balance
- - release controlled by signals from kidney
- Androgens: small amounts of male & female sex hormones
- - important especially after menopause
What hormones does the adrenal medulla secrete and what are their functions?
- Released when sympathetic nervous system is stimulated ~ during stress
- Adrenaline: increases heart rate ~ blood to muscles & brain
- -raises blood glucose
- Noradrenaline: works with adrenaline
- -increased heart rate
- -widening pupils and airways
- -narrowing of blood vessels to non-essential organs ~ higher blood pressure
What are the two functions of the pancreas?
- Exocrine gland:-produces pancreatic juice
- -produces digestive enzymes ~ amylases, proteases (eg trypsin), lipases
- Endocrine gland:
- -produces insulin and glucagon
- -made by islets of Langerhans
Describe the islets of Langerhans
- α cells (alpha) ~ produce and secrete glucagon
- -larger & more numerous
- β cells (beta) ~ produce and secrete insulin
What word describes the process of glycogen in the liver breaking down to form glycogen
What word describes the production of glucose from non-carbohydrate sources?
What word describes the formation of glycogen from excess glucose?
How does insulin work?
- Released when blood glucose is too high
- Binds to receptors on cell surface membrane (on virtually all body cells)
- Opens glucose transport proteins ~ more glucose enters cells
- Activates enzymes in certain cells to convert glucose to glycogen
- Broken down by enzymes in liver ~ must be secreted constantly when needed
- Lowers blood glucose conc by:-inc rate of absorbtion
- -inc respiratory rate of cells
- -inc rate of glycogenesis
- -inc rate of glucose to fat conversion
- -inhibiting release of glucagon
What type of feedback do falling levels of glucose provide to beta cells?
- Negative feedback
- -insulin drops below point
- -β cells reduce their secretion of insulin
How does glucagon work?
- Released when blood glucose is too low
- Binds to receptors found only on liver and fat cells
- Raises blood glucose by:-glycogenolysis ~ liver breaks down glygocen into glucose and releases into blood
- -reduces amount of glucose absorbed by liver cells
- -gluconeogenesis ~ increasing conversion of amino acids and glycerol into glucose in the liver
How can insulin and glucagon be describes in terms of how they work as a pair?
- antagonistic~ work against each other
Why is the system of maintaining blood glucose said to be 'self-regulating'?
The level of blood glucose is what determines the quantity of insulin and glucagon released.
How is insulin secretion controlled?
- 1. Normal blood glucose levels: ATP-sensitive potassium channels open on plasma membrane of β cells.
- -potassium ions diffuse out
- -inside of cell -70mV potential (wrt outside of cell)
- 2. Blood glucose concentration rises: glucose enters β cell by glucose transporters
- 3. Glucose metabolised inside mitochondria ⇒ production of ATP
- 4. ATP binds to ATP-sensitive potassium channels causing them to close
- 5. Potential difference reduced to -30mV, depolarisation occurs6. Depolarisation causes voltage gated calcium ion channels to open
- 7. Calcium ions enter cell and cause secretory vesicles to release insulin by exocytosis
What types of diabetes are there and what are their key features?
- Type 1:
- -unable to produce insulin
- -β cells of Langerhans don't make it
- -cause unknown ~ no cure
- -possibly autoimmune attack on β cells
- -symptoms develop quickly
- Type 2:
- -β cells do not produce enough insulin
- -OR body does not respond to insulin as it should
- -caused by excess body weight, physical inactivity, excessive overeating of carbs.
- -symptoms develop slowly
How are each types of diabetes treated and managed?
- Type 1:
- -regular insulin injections ~ insulin dependent
- -regularly test body glucose
- -too much insulin can result in hypoglycaemia (very low blood glucose)
- -too little insulin can result in hyperglycaemia (very high BG)
- -both can result in unconsciousness and death
- Type 2:
- -regulate carbs intake through diet
- -match to exercise levels
- -increase exercise
- -weight loss
- -drugs to stimulate insulin production
- -drugs to slow down glucose absorption
- -insulin injections
Where was and is insulin obtained?
- Originally from pancreas of cows and pigs
- -difficult & expensive
- -could cause allergic reactions
- Now from GM bacteria
- -pure human insulin
- -less likely to cause allergic reaction
- -produced in higher quantities
- -overcomes religious and ethical concerns of using animal products
What potential treatments are there for diabetes?
- Stem cell therapy
- -likely from embryos
- -alternatively using preserved umbilical cord stem cells
- Advantages to the treatment:
- -donor availablility wouldn't be an issue ~ stem cells would produce unlimited source of β cells
- -reduced likelihood of rejection
- -no longer need to inject insulin
What is the flight of fight response and how does it work?
- Body's response to potential danger, preparing it to run or fight
- Threat detected by autonomic nervous system
- Hypothalamus communicates with sympathetic nervous system and adrenal-cortical system
- Sympathetic NS sends impulses to glands and smooth muscle & tells adrenal medulla to release adrenaline & noradrenaline
- Adrenal cortex stimulated by hormone from pituitary gland to produce other hormones to help deal with threat
How does adrenaline work?
- Triggers liver cells to undergo glycogenolysis
- -release glucose
- Second messenger model
- Binds to receptors on liver cell surface membrane
- Triggers chain of reactions inside cell:
- -activates adenyl cyclase (enzyme)
- -which converts ATP to cyclic AMP (on inner surface membrane)
- -cAMP acts as second messenger
- -which activates other enzymes (protein kinases which phosphorylate, hence activating other enzymes) in order to convert glycogen to glucose
How is heart rate controlled?
- Medulla oblongata
- -2 centres linked to SAN: (sino-atrial node)
- -one increases HR via impulses through sympathetic NS (accelerator nerve)
- -one decreases HR via impulses through parasympathetic NS (vagus nerve)
- baroreceptors:-blood pressure
- -present in aorta, vena cava, carotid arteries
- -detect levels of particular chemicals in blood e.g. CO2
- -present in aorta, carotid artery and medulla
How do chemoreceptors register pH of blood?
- If CO2 levels increase, pH decreases (becaue carbonic acid is formed when CO2 and H2O interact)
- When pH is low, response is triggered to increase HR and remove CO2 via exhalation
- When pH rises, frequency of impulses to medulla oblongata is reduced, reducing frequency of impulses sent to SAN, thus reducing HR
How do the baroreceptors influence heart rate?
- Detect pressure changes
- High blood pressue → impulses sent to medulla oblongata to reduce HR→ decreases HR by sending impulses along parasympathetic NS to SAN
- Low blood pressure → impulses sent to medulla oblongata centre to increase HR → impulses sent to SAN via sympathetic neurones
How is heart rate influenced by hormones?
- Adrenaline and noradrenaline affect pacemaker region of heart
- Increase frequency of impulses produced by SAN
What is negative feedback and how does it work?
- Effectors work to restore a change in conditions back to original, reversing initial stimulus
- E.g. temperature control and water balance in body
What is a positive feedback system and how does it work?
- Change in internal environment detected, and effectors stimulated to reinforce the change.
- E.g blood clotting cascade, childbirth
What term describes the maintenance of body temperature?
What processes cause an organism to heat up or cool down?
- Exothermic chemical reactions
- Latent heat evaporation ~ with water
- Radiation ~ to and from organism and surroundings
- Convection ~ heating and cooling by currents of air
- Conduction ~ heating as a result of collision of molecules. Water and ground are good conductors
What are ecto and endotherms?
- Ectotherms:-use surroundings to warm body
- -core body temperature heavily dependent on surroundings
- -invertebrates, fish, amphibians and reptiles
- Endotherms:-Rely on metabolic processes to warm up
- -stable body temperature regardless of surroundings
- -mammals and birds
How do ectotherms regulate their body temperature?
- Basking in the sun
- Orientate body to expose high SA
- Press against warm ground
- Cool down ~ eg find shade
- Physiological: Colour
How do we detect temperature changes?
- Peripheral temperature receptors in skin
- Temperature receptors in hypothalamus
How do endotherms cool down?
- Vasodilation ~ arterioles near skin surface dilate. Vessels directly connecting arterioles and venules constrict. Blood forced through surface capillaries.
- Reducing insulation from hair/feathers
- ~ erector pili muscles relax, avoids trapping air
How do endotherms warm up?
- Vasoconstriction Decreased sweatingRaising body hair/feathers ~ trap a layer of insulating air
- Shivering ~ rapid, involuntary contraction of muscles to produce metabolic heat
What is excretion?
The removal of waste products of metabolism from the body
What are the main waste products in mammals?
- Bile pigments ~ formed from breakdown of old red blood cells in liver, excreted in bile, and colour the faeces
- Nitrogenous waste ~ formed from breakdown of excess amino acids by liver
- (urea for mammals, ammonia for fish, and uric acid for birds)
How is blood supplied to and taken from the liver?
- Hepatic artery: oxygenated blood
- Hepatic portal vein: from the intestines, loaded with products of digestion
- Hepatic vein: removes deoxygenated blood
What are liver cells called and what features do they have?
- Hepatocytes-Large nuclei
- -Prominent Golgi apparatus
- -Lots of mitochondria
What are the areas of the liver called where blood from the hepatic artery and hetatic portal vein mix?
What type of cells are found in the sinusoids and what is their function?
- Kupffer cells
- -resident macrophages
- -ingest foreign particles to protect liver form disease
What main functions does the liver have?
- Carbohydrate metabolism: the store and release of glucose
- Deamination of excess amino acids: the removal of an amine group
- -body cannot store proteins
- -amine group removed → ammonia → urea
- -rest of amino acid fed into cellular respiration or converted into lipids for storage
- Detoxification: liver is the site where many toxins are detoxified & made harmless
- -eg. catalase turns hydrogen peroxide into oxygen and water
- -eg. alcohol dehydrogenase breaks down ethanol into ethanal which is then converted to ethanoate → used to build up fatty acids or cellular respiration
What is the ornithine cycle?
The set of enzyme controlled reactions converting ammonia into urea
Where does bile come from and what happens to it?
- Hepatocytes secrete bile from the breakdown of blood
- -into spaces called canaliculi
- -drains into bile ductules
- -taken to gall bladder
What are the two main roles of the kidneys?
Describe the anatomy of the kidneys
- Blood enters via renal artery
- Blood exits via renal vein → inferior vena cava
- The pelvis ~ central chamber where urine collects before passing out down ureter
- The medulla ~ contains tubules of nephrons that form the pyramids of the kidney and the collecting ducts
- The cortex ~ outer layer where blood filtering occurs
Describe the structure of the nephrons with relation to their function.
- Bowman's capsule: contains glomerulus
- Proximal convoluted tubule: first coiled region of tubule
- -found in cortex
- -many substances reabsorbed into the blood
- Loop of Henle: long loop of tubule that creates region of high solute concentration in medulla tissue fluid
- -descending loop travels into medulla
- -ascending loop travels back up to cortex
- Distal convoluted tubule: second coiled/twisted tubule
- -fine tuning of water balance
- -permeability of walls varies dependent on ADH
- -further ion and pH regulation
- Collecting duct: urine passes down it
- -through medulla to pelvis
- -more find tuning of water balance ~ walls sensitive to ADH
- Capillary network: ~ lead into a venule → renal vein
What is the first stage in the removal of nitrogenous waste?
- High pressure in glomerulus since blood enters via wide arteriole and exits through narrower arteriole
- Forces blood out through capillary walls
- Fluid passes through basement membrane ~ made of collagen fibres to act as sieve
- Podocytes act as additional filter ~ wrap around capillaries
What happens after ultrafiltration?
Where does the first part of reabsorption take place?
- Proximal convoluted tubule
- Moves glucose, amino acids, vitamins and hormones back into blood
- 85% sodium chloride and water (Na+ by active transport, Cl- and water passively) and moved back to blood
- Cells lining tubule covered in microvilli ~ increase SA
- Many mitochondria for active transport
How does reabsorption take place in the Loop of Henle?
- The ascending limb of the loop of Henle:
- -impermeable to water
- -very permeable to Na and Cl ions
- -they move out by diffusion in the first part
- -& are actively pumped out in the second part
- -produces high concentration of Na and Cl ions in medulla tissue fluid
- The descending limb of the loop of Henle:
- -lower section permeable to water
- -water diffuses out
- -impermeable to Na and Cl ions
- -no active transport
What happens in the distal convoluted tubule?
- -permeability of walls vary depending on ADH
- -cells have many mitochondria ~ adapted for active transport
- -if body lacks salt ~ Na & Cl ions actively pumped out
- -water may leave to concentrate the urine
- -balances the pH of blood
What happens in the collecting duct?
- Concentration and volume of urine determined
- -water moves out by osmosis as levels of Na ions increase in surrounding fluid
- -permeability of collecting duct to water altered by ADH
Where is ADH produced and what does it do?
- Produced in hypothalamus & stored in posterior pituitary gland
- Increases permeability of distal convoluted tubule and collecting duct to water
- ~ negative feedback
- Osmoreceptors in hypothalamus linked to its release, and detect concentration of inorganic ions
- -short supply of water → high conc of ions
- -excess of water → blood is more dilute → low conc of ions
How does ADH work?
- binds to receptors on tubule cells
- triggers formation of cAMP
- cAMP causes:
- -vesicles in the lining of the collecting duct fuse to cell surface membrane by medulla
- -vesicle membranes contain aquaporins (protein water channels), making the cell surface membrane more water permeable.
- -water moves out of tubule cells into tissue fluid
- The more ADH → more water channels inserted into membrane → more easy for water to leave by diffusion → resulting in small amount of concentrated urine
How are monoclonal antibodies made?
- Antibodies from a single clone of cells produced to target particular cells/chemicals in the body
- 1. Mouse injected with hCG (eg) so it makes appropriate antibody
- 2. B-cells removed from spleen of mouse & fused with myeloma (cancer cell) that divides rapidly
- 3. New cell "hybridoma" reproduces rapidly and makes the antibody which is collected and purified
How does a pregnancy test work?
- 1. Wick soaked in urine from the mother in the morning (highest levels of hCG)
- 2. Test contains mobile monoclonal antibodies attached to small coloured bead, and only bind to hCG.
- 3. If woman is pregnant hCG (from urine) binds forming hCG-antibody complex
- 4. Urine moves up test strip
- 5. 1st window: Immobilised monoclonal antibodies (arranges in line or + shape) bind to hCG-antibody complex, and a colour appears
- 6. Urine continues up test strip to 2nd window
- 7. Line of immobilised antibodies that bind to mobile antibodies regardless of hCG, if colour appears the test is shown to be working
What are anabolic steroids and how are they tested for?
- Used in sport
- Mimic testosterone ~ stimulate growth of muscles
- Excreted in urine ~ gas chromatography and mass spectroscopy
Why might the kidneys fail?
- Infections that damage podocytes and tubules
- High blood pressure ~ damages structure of epithelial cells and basement membreane of Bowman's capsule
- Genetic conditions
What symptoms do infected or damaged by high blood pressure kidneys cause?
- Protein in urine ~ if basement membrane of Bowman's capsule, or podocytes are damaged
- Blood in urine ~ filtering process no longer works
What symptoms are present when the kidneys fail completely?
- Loss of electrolyte balance ~ body unable to excrete sodium, potassium, and chloride ions
- Build up of urea ~ can poison cells
- High blood pressure ~ since kidneys help control blood pressure
- Weakened bones ~ calcium/phosphorus balance in blood is lost
- Pain & stiffness in joints ~ abonormal proteins build up in blood
- Anaemia ~ kidneys stimulate formation of red blood cells
What is used as a measure to indicate kidney disease and how is it done?
- Glomerular filtration rate (GFR)
- Sample of blood measures level of creatinine in blood (breakdown product of muscle)
- Used to give an estimated GFR (eGFR ~ cm3/min)
- If levels increase, kidneys are likely not working properly
- Take into account:
- -age ~ GRF decreases steadily with age
- -gender ~ men usually have more than women due to more muscle mass
How is kidney failure treated?
- -Peritoneal dialysis
How does Haemodyalysis work?
- Dialysis machine
- Blood leaves body into machine
- Flows between partially permeable dialysis membranes
- -mimic basement membranes of Bowman's capsule
- Dialysis fluid
- -normal plasma levels of glucose → no net movement
- -normal plasma levels of mineral ions → excess leaves restoring electrolyte balance
- -no urea → high conc gradient and urea diffuses out
- Blood and dialysis fluid flow in opposite directions → maintain concentration gradients
- Takes 8 hours
- Repeated regularly
- Diet must be managed carefully
How does Peritoneal dialysis work?
- Inside the body ~ making use of natural dialysis membranes found in lining of abdomen (peritoneum)
- At home, normal life while it takes place
- Dialysis fluid introduced using a catheter
- Left several hours
- Fluid drained & discarded
How does a kidney transplant work?
- Single, healthy donor kidney placed within body
- Blood vessels joined and ureter inserted into bladder
- Risk of rejection
- -best match found
- -immunosuppressant drugs
- Transplanted organs don't last forever
Dialysis or Transplant? Pros vs Cons
- +readily available
- -monitor diet carefully
- -expensive long-term
- -eventually damages body
- +free from restrictions
- -shortage of donor organs
- -immunosuppressant drugs
Describe the processes involved for a seed to germinate
- Seed absorbs water
- → embryo activated
- → produces gibberellins ~ evidence suggests gibberellins switch on genes that code for amylases and proteases
- → stimulate production of enzymes that break down food stores in seed
- → embryo plant uses these to produce ATP for building materials
Evidence suggests ABA acts as an antagonistic to gibberellins, and it is the relative levels of both that determine germination
What experimental evidence is there supporting the role of gibberellins in seed germination?
- Mutant varieties that lack the gene to produce gibberellins do not germinate, unless gibberellins are applied to them.
- If gibberellin biosynthesis inhibitors are applied, the seed won't germinate until they are removed
What effects do auxins have on plant growth?
- Stimulate growth of main apical shoot:
- -affect plasticity of cell wall ~ auxins make it stretch more
- -auxins bind to receptors on the cell membrane → fall in pH to about 5
- -optimum pH for enzymes needed to keep cell walls flexible
- -cells expand as they absorb water & vacuoles get bigger
- -auxins are destroyed as the cell matures
- -cell walls return to normal pH & go rigid
- Suppress growth of lateral shoots:
- -"apical dominance"
- -growth in main shoot is stimulated by auxins produced in the tip
- -lateral shoots' growth inhibited as the hormone moves back down the stem
- -further down stem, auxin conc is lower so lateral shoots can grow more strongly
- Promote root growth:
- -low concentrations
- -up to a point, the more auxin, the more the root grows
- -produced in the root tips, and arrives from growing shoots
- -if apical shoot is removed, root growth slows/stops since the amount of auxin reaching the roots is greatly reduced
What experimental evidence is there in support of the role of auxins in apical dominance?
- If apical shoot is removed, there is no source of auxin from the shoot, and lateral shoots grow faster, freed from the apical dominance
- If auxin is artificially applied to the cut apical shoot, apical dominance returns
What do gibberellins do?
- Elongation of plant stems
- -affect the length of the internodes ~ regions between leaves on a stem
- Discovered from a fungus that produced them and affected rice crops making them spindly
Which two terms describe the ways in which plant hormones work together?
- Synergism ~ complementing each other to give a greater response
- Antagonism ~ have opposite effects → their balance controls the response. E.g chemicals that promote and inhibit growth
Why do deciduous plants lose there leaves?
- A point comes during some seasons when the amount of glucose needed for respiration to maintain the leaves, and produce antifreeze products, is greater than the amount of glucose made by photosynthesis
- -more efficient to lose their leaves and remain dormant
How are plants sensitive to daylength sensitivity?
- Sensitive to a lack of light ~ photoperiodism
- Results from a light sensitive pigment phytochrome-exists in two forms ~ Pr & Pft
- -each absorbs different type of light, and their ratio changes depending on levels of light
How does abcission (leaf fall) take place?
- Lengthening of darker periods triggers it
- Less light → auxin levels fall
- Leaves respond by producing ethene (gaseous hormone)
- Base of leaf is abcission zone ~ two layers of ethene sensitive cells
- Ethene causes gene switching in them → causing production of enzymes
- These digest cell walls in outer layer of abcission zone ~ forming separation layer
- Vascular bundles sealed off
- Fatty material deposited in cells on stem side of separation layer
- Forms protective, waterproof scar → keeps pathogens out
- Cells deep in separation zone respond to hormonal cues → retaining water → swelling → putting pressure on to cause leaf to fall off (along with other abiotic facors)
How and why do plants respond to cold temperatures?
- Low temperatures may cause cells to freeze and disrupt their membranes → so they die
- Sustained cold spells and less light suppresses and activates different genes
- Cytoplasm of plant and sap in vacuoles contain solutes that lower freezing point
- Some plants produces molecules that act as antifreeze or ones which protect cells from damage should freezing occur
How is the opening and closing of stomata in response to stress controlled?
- Largely controlled by hormone ABA
- Leaf cells release ABA under abiotic stress → stomata close
- Roots provide early warning system:
- -detect fall in soil water / transpiration
- -produce ABA → transported up plant to leaves
- -binds to stomatal guard cells → causing changes in ionic concentrations of cell, reducing water potential and therefore turgor → stomata close
What physical defences do plants have to herbivory?
Thorns, barbs, spikes, fibrous inedible tissue, hairy leaves
What chemical defences do plants have to protect them from herbivory?
- -bitter taste
- -toxic to insects
- -e.g. found in tea and red wine
- -bitter tasts
- -many act as drugs affecting metabolism and sometimes poisoning
- -e.g caffeine, nicotine, morphine
- -Caffeine toxic to fungi and insects, spreads into the soil preventing germination of other plants
- Terpenoids:-often form essential oils
- -act as toxins to insects and fungi
- -some act as repellents
- -chemicals which affect social behaviors of another organism of the same species
- -e.g if a maple tree is attacked by insects it releases a pheromone which is absorbed by other leaves to make them produce chemicals such as callose
- VOCs ~ volatile organic compounds:
- -similar to pheromones but between two different species
- -eg. cabbages, caterpillar, wasp
Give an example of a plant moving in response to herbivory
- Folding in response to touch
- Mimosa pudica -if leaves are touched they fold and collapse ~ scares larger herbivores and dislodges smaller insects
- -leaf takes 10-12 minutes to recover through movement of potassium ion movement and osmotic movement into particular cells
What type of tropisms are there?
- Photo ~ light
- Chemo ~ chemicals
- Geo (or gravi) ~ gravity
- Thigmo ~ touch
What practical investigations can be done to study phototropisms?
- Germinate and grow seedlings in different conditions. Observe and measure patterns of growth.
- Germinate and grow seedlings under unilateral light with different colour filters to see which wavelengths of light they respond to
- Cover tips of coleoptiles in foil, remove tips, place auxin impregnated agar jelly blocks on decapitated coleoptiles, place auxin impregnated agar blocks on one side only of decapitated coleoptiles
What effects does unilateral light (on one side) have on auxin concentrations and the direction of plant growth?
- Light causes the auxin to move to the other side of shoot
- Concentration is higher on the dark side
- Stimulates growth on shady side
- Shoot grows towards the light
What practical investigations can be done to investigate geotropisms?
- Grow shoots in slowly rotating drum (gives equal gravitational stimulus to all sides) and observe that shoot and roots will grow straight
- Grow seeds in vertical petri dishes and observe their directions of growth
How are plant hormones used commercially?
- Control of ripening:
- -fruit harvested when fully formed but not yet ripe
- -cooled, stored and transported
- -ethene applied when needed to ripen batch
- -fruit put on sale to public
- ~ reduces waste and increases window of sale
- Hormone rooting powders and micropropagation:
- -application of auxin to cut stem causes roots to develop
- ~ easier to take successful cuttings (propagation) or perform micropropagation
- Hormonal weedkillers:
- -synthetic auxins can act as weedkillers
- -aimed at type of weed, affect its metabolism and cause it to die
- ~ cheap, low toxicity to mammals, selective
What are the equations of photosynthesis and respiration?
- Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2
- Resiration: C6H12O6 + 6O2 → 6CO2 + 6H2O
What is respiration?
- Process by which organic molecules (such as glucose) are broken down into smaller inorganic molecules (like CO2 and H2O)
- Energy stored in the bonds is used to synthesise ATP
What is the importance of Carbon-Hydrogen bonds?
- Lots of (relatively weak, non-polar) C-H bonds in large molecules such as glucose or lipids
- Broken during respiration to form H2O and CO2 (with relatively strong bonds)
- Releases large amounts of energy
How is ATP primarily synthesised in both respiration and photosynthesis?
- Diffusion of protons from high concentration to low through partially permeable membrane
- Their movement releases energy used in attachment of an inorganic phosphate (Pi) to ADP to form ATP
- Conc gradient created with energy from excited electrons
What are excited electrons?
- Electrons raised to a higher energy level by:
- - absorbing light from Sun in the pigment molecules (eg chlorophyll)
- - released when chemical bonds are broken in respiratory substrate molecules
What is an electron transport chain?
- Made up of series of electron carriers-each with progressively lower energy levels
- -energy released as high energy electrons move down chain
- Energy used to pump protons across membrane
- -producing proton gradient
- -maintained as a result of impermeability of the membrane to H+ ions
- Protons can move back down gradient through hydrophilic membrane channels linked to ATP synthase
- -flow of protons through channel provides energy used to synthesise ATP
Describe the structure of chloroplasts
- Outer and inner membranes
- Membranes form flattened sacs ~ thylakoids
- Thylakoids are stacked to form grana (singular granum)
- Grana joined by membranous channels ~ lamellae
- Light absorbed by pigments embedded within thylakoid membranes
- Fluid enclosed is called stroma & is site of many chemical reactions forming complex organic molecules
What is a photosystem?
- Made up of light harvesting system and reaction centre
- Chlorophyll b, xanthophylls and carotenoids are embedded in thylakoid membranes along with other proteins, together forming the light harvesting system (or antennae complex)
- -absorbs/harvests light energy of different wavelengths and transfers it to the reaction centre
- Chlorophyll a is located in reaction centre
- -where reactions involved in photosynthesis take place
What are the two main stages of photosynthesis?
- Light dependent stage:
- ~light from sun absorbed & used to make ATP
- ~Hydrogen from water used to reduce coenzyme NADP to NADPH (reduced NADP)
- Light independent stage:
- ~Hydrogen from NADPH and CO2 used to build organic molecules
- ~ATP supplies the energy
What happens in non-cyclic photophosphorylation?
(Light Dependent stages)
- Photosystem II (PSII) absprbs light of wavelength 680nm
- Excited electrons released into electron transport chain (ETC)
- ATP produced by chemiosmosis
- Electrons lost from PSII replaced from water molecules broken down using energy from Sun
- Photosystem I (PSI) absorbs light at 700nm
- Releases excited electrons to another ETC again producing ATP by chemiosmosis
- Electrons lost from PSI replaced by those from first ETC
- Electrons from PSI released & accepted with a H+ ion by coenxyme NADP to form NADPH
What is photolysis?
(Light Dependent stages)
- Water molecules split into H+ ions, electrons and Oxygen molecules using energy from Sun
- H2O → 2H+ + 2e- + O2Electrons released from photolysis replace those lost in PSII
- Oxygen is released as a biproduct
- Protons released into lumen of thylakoid ~ increasing concentration gradient ~ when they move back through they drive production of more ATP
- Once they return to stroma they combine with an e- from PSI and NADP to form NADPH
- - this removes H+ from stroma, maintaining concentration gradient
What is cyclic photophosphorylation?
(Light Dependent stages)
- Electrons leaving PSI return to PSI (instead of being used to form reduced NADP)
- -PSI can therefore still lead to ATP production without e- from PSII
- -NO reduced NADP is formed
Where does the light independent stage of photosynthesis occur?
Stroma of chloroplasts
What happens during the Calvin cycle?
(Light Independent stage)
- CO2 enters intercellular spaces within spong mesophyll of leaves by diffusion through stomata
- -diffuses into cells and into stroma of chloroplasts
- Combined with 5-carbon compound ribulose bisphosphate (RuBP):
- -carbon in CO2 is therefore fixed ~ incorporated into an organic molecule
- -Enzyme ribulose bisphosphate carboxylase (RuBisCO) catalyses the reaction
- -unstable 6-carbon intermediate produced
- 6-carbon compound immediately breaks down to form two 3-carbon compounds ~ glycerate 3-phosphate (GP)
- Each GP converted to triose phosphate (TP) using hydrogen atom from NADPH and energy from ATP
- TP (a carbohydrate, 3 carbon sugar) is recycled to regenerate RuBP & is the starting point for synthesis of other biological molecules such as carbohydrates, lipids, proteins and nucleic acids
What three stages can the calvin cycle be summarised as?
- Fixation ~ CO2 fixed (incorporated into organic molecule)
- Reduction ~ GP reduced to TP by addition of Hydrogen from NADPH using energy from ATP
- Regeneration ~ RuBP regenerated from recycled TP
Why is RuBisCO so inefficient?
- It is completely inhibited by oxygen
- - a lot of it is needed to carry out photosynthesis successfully
How is RuBP regenerated and glucose produced?
- 6 turns of calvin cycle per glucose molecule produced
- -production of 12 TP:
- -10 recycled to make 5 more RuBP using energy supplied from ATP
- -2 used to make glucose
What is a limiting factor?
When a factor needed for photosynthesis is in short supply, it reduces the rate of photosynthesis and becomes a limiting factor
How can the rate of photosynthesis be measured using pond weed?
- Measure rate of oxygen production, carbon dioxide used, or increase in dry mass of plant
- Sodium hydrogen carbonate used to provide CO2
- Leave to equilibrate before taking readings
- Calibrate oxygen sensor to conc of air at 21%
How does decreasing light intensity affect the Calvin Cycle?
- Reduces the rate of light dependent stage
- - reduce quantity of ATP and NADPH produced
- - ATP & NADPH needed to convert GP to TP
- ⇒ concentration of GP increases
- ⇒ concentration of TP decreases
- - Since less TP, concentration of RuBP decreases as it is not regenerated
- (Reverse happens if light intensity is increased)
How does the concentration of CO2 affect the concentrations of the molecules within the Calvin cycle?
- Little CO2
- ⇒ reduced concentrations of GP and TP since less CO2 to be fixed
- ⇒ RuBP concentration increases since it is still being formed from TP but not being used
What is the first stage of cellular respiration?
- -in cell cytoplasm
- -Glucose is split into two pyruvate molecules
What are the main stages of glycolysis?
- Phosphorylation:-2 ATP provide 2 phosphates
- -which attach to glucose
- -form hexose bisphosphate
- Lysis:-destabilises molecule splitting it into 2 TP (triose phosphate) molecules
- Phosphorylation:-phosphate group added to each TP
- -from free Pi ions in cytoplasm
- -forms 2 triose bisphosphate
- Dehydrogenation & formation of ATP:-removal of hydrogen (oxidising) from each
- -H from each combines with 2NAD to form 2 NADH
- -phosphates from each used to produce 4 ATP molecules (2 for each triose bisphosphate)
- -results in 2 pyruvate molecules
What is substrate level phosphorylation?
- Formation of ATP without electron transport chain-transfer of phosphate group from a phosphorylated intermediate (eg triose bisphosphate in glycolysis) to ADP
What is the total yield of ATP during glycolysis?
- 2 ATP
- -since 2 are used at the start
- -4 are produced at the end
What step follows glycolysis in aerobic respiration and how does it work?
- Link Reaction (Oxidative decarboxylation)-mitochondrial matrix ~ pyruvate actively pumped in
- -decarboxylation ~ CO2 removed (& diffuses away/used for photosynthesis in autotrophs)
- -oxidation ~ H removed which combines with NAD to form NADH
- -results in 2-carbon acetyl group which is bound by coenzyme A to form acetylcoenzyme A (acetyl CoA)
- -acetyl CoA delivers acetyl group to Krebs cycle
Which stage follows the link reaction/ oxidative decarboxylation in aerobic respiration?
- Krebs Cycle
- -mitochondrial matrix
- -each cycle results in breakdown of an acetyl group
How does the Krebs cycle work?
- Acetyl group delivered from acetyl CoA
- Acetyl group combines with 4-carbon oxaloacetate to form 6-carbon citrate
- Citrate undergoes decarboxylation and dehydrogenation to form 5-carbon compound (1CO2 and NAD→NADH)
- 5-carbon compound undergoes decarboxylation and dehydrogenation to form 4-carbon compound (1CO2 and NAD→NADH)
- 1 ATP produced by substrate level phosphorylation
- FAD reduced to FADH2
- Another NAD reduced to NADH
- Oxaloacetate regenerated
Why are NAD and FAD both important in respiration and what are their differences?
- Both coenzymes that accept protons and electrons released from breakdown of glucose
- ☆NAD takes part in all stages of respiration, FAD only in Krebs
- ☆NAD accepts 1 H (NADH), FAD accepts 2 H (FADH2)
- ☆NADH oxidised at start of ETC, FADH2 oxidised further along (to release protons & electrons)
- ☆NADH results in synthesis of 3 ATP, FADH2 results in 2 ATP
Which step in aerobic respiration follows the Krebs cycle?
- Oxidative Phosphorylation -membranes of cristae in mitochondria
- -hydrogen atoms in NADH and FADH2 delivered to ETC ~ oxidation
- -hydrogen atoms dissociate into hydrogen ions and electrons
- -the high energy electrons used to synthesise ATP by chemiosmosis down ETC
- -at end of ETC electrons combine with H+ and oxygen to form water ~ aerobic process
What is fermentation?
- A form of anaerobic respiration
- The process by which complex organic compounds are broken down into simpler inorganic compounds without oxygen or an ETC
- -substrate level phosphorylation onl
- -not fully broken down so much less ATP produced
What types of fermentation are there?
- Alcoholic fermentation-yeast
- -end products: ethanol + CO2
- Lactate fermentation
- -animal cells
- -produces lactate (lactic acid)
Describe the process of Lactate fermentation in mammals
- Pyruvate acts as a hydrogen acceptor from NADH
- -forms lactate and NAD
- -catalysed by enzyme lactate dehydrogenase
- NAD used to keep glycolysis going
- -so ATP is still produced by chemiosmosis
- Lactic acid converted back to glucose in liver using oxygen (reason for oxygen debt)
- Cannot occur indefinitely because:
- -amount of ATP produced not enough to maintain vital processes for long time
- -accumulation of lactic acid changes pH, denaturing proteins such as respiratory enzymes and muscles
Describe the process of alcoholic fermentation in yeast
- Pyruvate converted to ethanal
- -removal of CO2
- -catalysed by pyruvate decarboxylase
- Ethanal accepts hydrogen atom from NADH
- -forms ethanol
- -NADH → NAD
- NAD able to act as coenzyme allowing glycolysis to continue
How can respiration rates in yeast be measured?
- Measure rate of CO2 production
- Yeast + respiratory substrate solution (e.g glucose)
- Sealed flask
- Production of CO2 caused coloured liquid in capillary tube to move
- Volume of CO2 calculated based on distance and diameter of tube
How do you calculate the respiratory quotient?
Measured using respirometer
What is the RQ of glucose?
- -6 molecules of oxygen in
- -6 molecules of carbon dioxide produced
Which respiratory substrates store the most energy and has the lower RQ?
- Lipids have highest energy content and low RQ
- Carbohydrates have lower energy content and RQ of 1
What is the RQ value during normal activity vs anaerobic respiration?
- Normal activity: 0.8-0.9
- -since carbohydrates, lipids and some proteins are being used as respiratory substrates
- Anaerobic respiration: above 1.0
How can rate of respiration be calculated?
- -potassium hydroxide solution at bottom absorbs CO2 produced
- -so any change in volume will be due to oxygen uptake
- -left to calibrate
- -coloured fluid added to capillary tube ~ see how far it moves
Describe the structure of mitochondria