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What are the five ways of diffusion across cell membranes?
- Passive diffusion through membrane pores
- Passive diffusion through the membrane's hydrophobic layers
- Carrier-mediated diffusion (facilitated diffusion)
- Active Transport
- Endocytosis (phagocytosis, pinocytosis, receptor-mediated endocytosis)
- Exocytosis (secretion)
What is diffusion?
The spontaneous movement of particles (molecules, atoms, ions) from a region of high concentration to a region of low concentration
What is equilibrium?
- When the rate of movement of a substance across a semi-permeable membrane is the same in both directions
- ---> there is no net flow
What is a concentration gradient?
The difference in concentration on either side of a semi-permeable membrane
What is osmosis?
- Diffusion of water (down a conentration gradient)
- ---> no energy required
How much solute moves per unit of time?
What is diffusion through membrane pores?
- Diffusion of a substance down its concentration gradiant through the hydrophobic barrier of a membrane
- Through water channels, aquaporins
- The rate of diffusion is proportional to the concentration gradient
- No energy is required
- Equilibrium occurrs when the concentration gradient is zero
What are aquaporin-1 and porin?
proteins known to form pores in cell membranes
What happens to an animal cell when placed in a hypertonic solution?
It lyses (bursts)
What happens to an animal cell when placed in a hypotonic solution?
Crenation (It shrivels)
What happens to a plant cell when placed in a hypertonic solution?
It is turgid (normal)
What happens to a plant cell when placed in a hypotonic solution?
It is plasmolyzed
What happens to a plant cell when placed in a isotonic solution?
It is flaccid
What are examples of molecules that transport by passive diffusion through membranes?
CO2, O2, N2
What is unique about passive diffusion through the membrane?
only molecules soluable in both water and lipid can pass through because of the hydrophobic layer
What is carrier-mediated or facilitated diffusion?
- Transport specific for particular substances such as amino acids, sugars, vitamins, and minerals (ions) down the concentration gradient
- It requires a membrane transport protein
- No energy required for this
- Equilibrium occurs at zero concentration gradient
How do the membrane transport proteins work in carrier mediated diffusion?
they are either a channel (that can open/close) that the substance flows through, or a protein that takes the substance then "flip flops" and changes fold to move it into the cell
What is active transport?
- Form of transport that requires a membrane transport protein to move particular substances up a concentration gradient
- energy is required to pump these substances up the gradient
- can be up or down concentration gradient
- examples of substances moved by active transported this way are amino acids, sugars, vitamins, minerals (ions)
passive vs active transport pictures
Know the sodium potassium pump
Explain the Na+ K+ pump
- Outside cell: Na+ is high concentration, K+ is low... pump will pump against concentration gradient
- Cytoplasmic Na+ binds to the sodium potassium pump
- Na+ binding stimulates phosphorylation (addion of a phosphate) to ATP
- Phosphorylation causes the protein to change its conformation opening towards the outside of the cell, the shape change releasing Na+ and making a shape to accept the K+
- K+ binds to the protein triggering the phosphate to be released
- Loss of the phosphate changes the conformation back to original Na+ accepting, releasing K+ inside the cell
- Cycle repeats
What are all the membrane protein functions?
- Enzyme activity
- Signal Transduction (recognition by receptor)
- Cell-cell recognition
- Intercellular joining/cell-cell adhesion
- Attachment/adhesion to the cytoskeleton and extracellular matrix
What happens with the proton pump?
- ATP gives the proton pump energy to pump H+ ions (or protons) out of the cell so that they can bind to sucrose and bring it into the cell through the sucrose-H+ cotransporter
- sucrose can later be broken down to make more ATP
What is Cystic Fibrosis?
- An inherited disease that affects the exocrine glands
- it causes the production of abnormally thick mucus, which leads to the blockage of the pancreatic ducts, intestines, and bronchi
- often results in respiratory infection
- 1 in 2500 live births affected
- mild to severe symptoms depending on the specific mutation causing the effect
What are symptoms of cystic fibrosis?
- Failure to thrive
- viscous, abnormal gland secretions
- pathological changes in respiratory tract
- shortened lifespan
What protein is defective in cystic fibrosis?
- Cystic Fibrosis Transmembrane Conductance Regulator
Why does the defectiveness of this transport protein cause the symptoms of cystic fibrosis?
Because CFTR helps transport chloride ions which helps control the movement of water in tissues, which is necessary for the production of thin free flowing mucous. If this protein is defective, the chloride ions are not transported and therefore water doesnt flow through, and mucus does not flow, but it builds up and blocks pathways such as in the lungs
What is endocytosis?
- a substance enters a cell without passin through the cell membrane
- movement of membranes requires energy
- ex: an amoeba engulfs a bacteria via phagocytosis
- 3 types
What are the three types of endocytosis?
- Receptor Mediated Endocytosis
What is phagocytosis?
- The cell ingests large objects such as bacteria, viruses, cell remains, etc
- stored in a food vacuole
What is pinocytosis?
- uptake of solutes and single molecules such as proteins
- stored in vesicles
- ex: vesicles form in a cell lining a small blood vessel
What is receptor mediated endocytosis?
- only endocytosis to use a receptor (others can take in anything in the spot they engulf)
- cytoplasm membrane folds inward to form coated pits and proteins or trigger molecules lock into receptors in the plasma membrane and are engulfed after they bind. These inward budding vesicles bud to form cytoplasmic vesicles
- Ex: a coated pit and a coated vesicle form during receptor mediated endocytosis
Explain Endoplasmic Reticulum/Golgi Transport
- Proteins to be exported are made "into" the ER where they are glycosylated (carbohydrates are added)
- The ER pinches off vesicles containing these proteins
- The vesicles move to the golgi
- they pass from inner to outer golgi, undergoing further modifications
- Vesicles carrying these proteins pinch off. Some move to the cell surface where the proteins may be secreted/released
- Membrane bound proteins in golgi vesicles move to the cell membrane when the vesicles fuse with it
What is familial hypercholesterolemia
- a genetic disorder characterized by high cholesterol levels, specifically high levels of low density lipoprotein (LDL-bad cholesterol)
- caused by a defect in chromosome 19
- body is unable to remove LDL
What are symptoms of famalial hypercholesterolemia?
- two types: mild and severe
- fatty skin deposits on hands elbows, knees, ankles, cornea of eye
- cholesterol deposists in eye lids
- chest pain
- heart atttacks early
How is familial hypercholesterolemia treated?
- lifestyle changes, changing what you eat and lowering amount of fat eaten
- medications: statins, bile acid sequesterint resisns
- severe form may need treatment called apheresis (where blood or plasma is removed from the body and special filters remove extra LDL and blood plasma is returned)
What is exocytosis?
- A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane (such as transport of proteins in ER golgi transport)
- secretion of proteines like enzymes, peptide hormones
What do chemical reactions always involve?
- A change in energy
- That change is always downhill (exergonic) or uphill (endergonic)
Can energy be created? Destroyed?
no but energy forms can be interconverted
What is endergonic and exergonic?
- endergonic: (uphill) requires input of energy, such as photosynthesis
- ---> molecules are synthesized (built up)
- exergonic: (downhill) releases energy
- ---> molecules are broken down
Endergonic or exergonic?
1. Meteor lands on your car
2. Hydrolysis of ATP: ATP ADP + Pi
3. Synthesis of ATP : ADP + Pi ATP
4. Synthesis of a protein from amino acids
5. Animal cell breaks down glucose to CO2 & water
6. Transport of Na+ from a region of low concentration to a region of high concentration
7. Plant synthesizes sugars from CO2 & water
8. Oxidiiation of gasoline
9. Explosive burning of hydrogen gas
- 1. exergonic
- 2. exergonic
- 3. endergonic
- 4. endergonic
- 5. exergonic
- 6. exergonic?
- 7. endergonic
- 8. exergonic
- 9. exergonic
What are the 3 principle uses of cell energy?
- Active Transport
All chemical reactions...
require or yeild some energy
What is the reaction that describes the hydrolysis of water into hydrogen gas and oxygen gas? is it endergonic or exergonic? What is the reverse reaction?
- H2O + Energy (electrical) ---> H2 + O2
- ---> endergonic
- Reverse reaction: H2 + O2 ---> H2O + Energy(heat, light, sound)
What is delta G?
energy available to do work
What is the equation for all chemical reactions when it comes to a change in energy?
What is the reaction to find the energy released or required?
deltaG= Gproducts- Greactiants
Info about G
G initial is high G final is low. if delta G (final-initial) is less than 0 reaction is exergonic. if greater than 0 its endergonic
What is a sponaneous reaction?
- beginning requirements: more free energy (higher deltaG), less stable, greater work capacity
- In a spontaneous change: the free energy of the system decreases (deltaG<0), the system becomes more stable, te released free energy can be harnessed to do work
- end result: less free energy (lower deltaG), more stable, less work capacity
What are examples of reactions that occur spontaneously?
- Gravitational motion
- Chemical reactions
Are spontaneous reactions ender or exergonic?
- they release energy
What is the structure of ATP
- -O -O -O Adenine
- | | | |
- - O--P---O--P--O--P-----O----Ribose
- || || ||
- -O -O -O
What is the structure of ADP?
same as ATP but one phosphate is detached and plus energy is included
What are the names for ATP and ADP
- ADP: adenosine diphosphate
- ATP: Adenosine triphosphat
Describe change from ADP to ATP and back
- first the phosphate and ADP are in a stable condition, unlikely to change
- then, with the addition of energy, it becomes possible to combine the phosphate and ADP to generate ATP which is highly unstable
- after, separation of a phosphate gives rise to ADP and P again with the release of energy, the same amount of energy that was required to bring P and ADP together. The released energy can do work.
What is the concept of coupling reactions, and why is it important?
- Coupling reactions happens so that one reaction releases the energy to drive another
- Unfavorable reactions are coupled to favorable reactions in our cells
- endergonic and exergonic reactions will couple
What is an example of reactions coupling
- ATP yeilds 100 U energy + ADP + phosphate
- relaxed muscle + 20 U of energy yeilds a contracted muscle
- coupled reaction: relaxed muscle + ATP yeilds contracted muscle +ADP+ Phosphate + 80 U energy released as heat
What is the role of ATP?
- Cells burn (oxidize) nutrients: C6H12O6 [carbohydrate] + O2 ---> CO2 + H2O + E (Energy)
- Energy from oxidation is used to make ATP: E + ADP + P ----> ATP
- Sum of two equations: C6H12O6 + O2 + ADP + P ----> CO2 + H2O + ATP
- Hydrolysis of ATP yeilds energy for cellular work
What is the equation for hydrolysis of ATP?
ATP --> ADP + Pi + 7500 cal/mole
How, where is ATP made?
- Photosynthesis (in chloroplast) --> carbohydrates
- Metabolism (in mitochondria) --> energy
Controlled vs. uncontrolled reaction?
- all at once: explosive, uncontrolled reaction
- ---> fire
- small steps: controlled release of energy for synthesis of ATP
- ---> work is done
Why does metabolism release energy derived from oxidation of bio fuels in small steps rather than all at once?
- stepwise oxidation of sugar allows the energy released to be stored by carrier molecules rather than released as heat
- if released all at once all energy is released as heat and none is stored
How do cells obtain energy?
the oxydation of organic molecules
Difference between oxidation recations and reduction reactions
- Oxidation reactions: release energy and form products with less potential energy
- Reduction reactions: require energy and form products with more potential energy
What do electron carrier molecules do?
- capture the energy from food to power biosynthesis, movement, active transport
- in glycolysis when glucose is oxydized, electron carriers capture the energy
What are the electron carriers in glycolysis? in Citric acid cycle?
- Glycolysis: NADH
- CAC: NADH and FADH2
Where do the electron carriers bring the electrons?
to the electon transport chain
What are the net products of cell respiration?
H2O+ 34 ATP + free electron shuttles (NAD+ and FADH)
Where are the enzymes involved in electron transport and chemiosmosis located?
the inner mitochondrial membrane/ cristae (folds of the inner membrane that increase the inner membranes surface area)
Where does glycolysis occur?
Where does the citric acid cycle occur?
Where does oxidative phosphorylation occur?
Which processes in respiration require oxygen?
- electron transport chain
what cells in our body use the highest amounts of energy
How does the electron transport chain work?
electrons are transported from carrier molecules like NADH and FADH2 (NADH will become NAD+) to carrier proteins stepwise, and finally to oxygen gas to form water and the energy released from various steps can move protons across the inner mitochondrial membrane to form aproton gradient
What is a proton gradient?
H+ ions or protons enter the stator from the intermembrane spance then enter the rotor. The rotor and internal rod spin around and the catalytic knob combines ADP and Pi to form ATP in the mitochondrial matrix
How does atp synthase use the electrochemical gradient of protons to generate ATP
the etc receives the electrons from the carries and electrons flow through the etc and cause hydrongen to be pumped into the intermembrane space throught the rotor which generates a proton gradient. the atp synthase (along the inner membrane) then allows the protons to flow down their concentration electrochemical gradients back into the matrix. the protons flowing throught the atp synthase generate a mechanical energy which causes the part of the enzyme sticking into the membrane to rotate inside of a stationary head. This mechanical energy is then converted to chemical bond energy needed to combine ADP and Pi in the matrix
What are the 2 phases of photosynthesis
- phase 1: light reactions
- phase2: dark reactions
What are the light and dark reactions of photosynthesis
- light reactions: light energy is harnessed to provide energy carriers to drive the dark reactions
- Dark reactions: energy carriers from light reactions are used to fix carbon dioxide into sugar (glucose)
Whar are all the types of radiation in increasing order?
- Gamma Rays
- x rays
- visible light
What are the wavelengths in nm for red green and blue
What happens with colors of light in photosynthesis?
chlorophyl absorbs red and blue light triggering photosynthesis and defracts green light so we see it
What are the basic steps of photosynthesis?
- light is absorbed by pigment (chlorophyll) in photosystem 1 which exites an electron to a high energy level. it falls back, releasing energy. released energy splits water into electrons protons and o2 as a waste product
- the electrons are passed down an electron transport chain including photosystem 1. in photsyste1 absorbed light aadds more energy to the electron
- during electron transport, released energy is used to pump protons into the lumen (inside) thylakoids, as wellas to synthesize NADPH from HADP. as proteins pass down their electrochemical gradient through atp synthase, atp is generated
What happens in the Calvin cycle?
high energy molecules (atp, and NAD (P) H) are used to reduce co2 to make sugars with oxygen as a biproduct
Where are the checkpoints in the cell cycle and what do they do?
- G1 checkpoint: ensures that DNA is undamaged before its replicated in DNA synthesis
- G2 checkpoint: ensures chromosomes are lined up on equatorial plane before anaphase begins
- M checkpoint(at anaphase): sister chromatids must be pulled in opposite directions
What do p21 and p53 do?
- p21: repair of damaged dna
- p53: signals apoptosis when dna cant be repaired
Why is having 1 normal p53 insufficient for protection from cancer?
bc although one works normal there is more chance that if that one breaks, the other does not function and cells will not go through apoptosis and divide wrong
What happens in interphase?
- 2 N chromosomes
- 1 chromatid per chromosome in G1, 2 in G2
- Dna synthesis
What happens in prophase?
- 2n chromosomes
- 2 chromatids per chromosome
- chromosomes condense
- centrioles move to opposite poles
- spindle forms
- nuclear membrane breaks down
What happens in metaphase?
- 2n chromosomes
- 2 chromatids per chromosome
- Chromosomes line up on equatorial plane
What happens in anaphase?
- 4n chromosomes
- 1 chromatid per chromosome
- Centromere splits to begin anaphase
- chromosome (1 chromatid each) separate to opposide poles along spindle
What happens in telophase
- 4n chromosomes
- 1 chromatid per chromosome
- spindle dissapears
- centrioles divide
- cytokinesis occurs
- nuclear membrane reforms