microbio exam 3
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What is metabolism? What are the two types and how do they work?
- the sum of all chemical reactions within a living organism
- TWO kinds
- Catabolism- the breakdown of complex organic compounds into simpler ones. Releases Energy/Heat
- the building up of complex organic molecules from simpler ones. Requires Energy *Releases heat (small amt)
What is activation energy?
the minimum amount of collision energy required for a chemical reaction
What do you call a substance that speeds up a chemical reaction without being permanently altered? In living cells, what is the term for this?
enzymes are biological catalysts
Identify: substrate, holoenzyme, apoenzyme, coenzyme (or cofactor)
- If the cofactor is an organic molecule, it's called coenzyme.
State what's a protein, and it's activity
Apoenzyme is ________________
Cofactor is the _______________
-Coenzyme is ______________
Holoenzyme is _________________
- Apoenzyme- protein, inactive
- Cofactor - non protein (usually vitamins), activates the apoenzyme
- -Coenzyme- same thing as cofactor, only it's organic (contains carbon)
- Holoenzyme- whole, active enzyme
Names of enzymes usually end in what? How many classes are they grouped in?
- 6 classes, according to type of chemical reaction they catalyze
Name 2 important coenzymes that act as electron carriers in cellular metabolism
- NAD+ nicotinamide adenine dinucleotide
- (aka NADH)
- FAD+ flavin adenine dinucleotide
- (aka FADH)
What are three things that influence enzymatic activity?
- substrate concentration
what are the two types of enzyme inhibitors? Define them!
competitive or non-competitive
competitive- fill the active site of an enzyme & compete w. the normal substrate
noncompetitive- interacts with another part of the enzyme (called the allosteric site) which then alters the shape of active site, therefore substrate can no longer bind.
what is feedback inhibition?
control mechanism that stops the cell from making more substance than what's needed.
The end product can allosterically inhibit the activity of one of the earlier enzymes in the pathway.
what is oxidation?
- the removal of electrons
- often produces energy
what is reduction?
gaining one or more electrons
oxidation & reduction are always coupled, hence it is called ______?
redox reaction (short for oxidation-reduction)
coupled reactions- 1 free energy drives the other. mechanistically joined
What is ATP? What "breaks" off to release energy? What is it called when this group reattaches?
- adenosine triphosphate, the terminal phosphate group.
- Phosphate added = phosphorylation.
ADP + P => ATP
What is cellular respiration? List it's 3 steps
An ATP generating process in which molecules are oxidized and the final electron acceptor is an inorganic molecule.
- 2. Krebs cycle
- 3. ETS
What is glycolysis?
the oxidation of glucose to pyruvic acid (with some production of ATP and energy containing NADH)
What is the start product of glycolysis? What are end results? Does it require oxygen?
- Start: glucose
- End: 2 molecules of pyruvate (or pyruvic acid)
- - net gain of 2 ATP
- - generation of 2 NADH carrier molecules
Does NOT require oxygen
What follows Glycolysis? What does it do with pyruvate?
- the Krebs cycle.
- Takes pyruvate turns it into Acetyl CoA. *This must happen before it enters the cycle, the process is called decarboxylation (b/c pyruvate must lose a CO2)
What are the end products of the Krebs cycle?
Where does the Krebs cycle occur in eukaryotes? and prokaryotes?
CO2, NADH (many), FADH2, & ATP
- eukaryotes- occurs in outer mitochondrial membrane
- prokaryotes- plasma membrane- cytoplasm interphase
In the Krebs cycle, for every 2 Acetyl CoA, what is produced?
2 Acetyl CoA => 4 CO2, 6 NADH, 2 FADH2
Along w. 2 ATP generated by substrate-level phosphorylation
What is substrate level phosphorylation?
ATP is generated when a high-energy Phosphate group is directly transferred from a phosphorylated compound (a substrate) to ADP
What is the Electron Transport System?
a sequence of carrier molecules that are capable of oxidation & reduction. (they can quickly accept electrons & transfer them in cascade fashion)
As electrons pass thru the chain, there's a stepwise release of energy, used to drive the chemiosmotic generation of ATP.
Where does the ETS occur in eukaryotes? and prokaryotes?
ETS occurs in eukaryotes in the INNER membrane of mitochondria
in prokaryotes it is in the plasma membrane
What is FMN? what is it's role in the ETS?
FMN - flavin mononucleotide
It's capable of performing alternating oxidation & reductions. It is the first to accept electrons in the ETS and it (the FMN) quickly transfers them to next molecule Coenzyme Q
List steps/order of ETS (in eukaryotes)
- 1. transfer of e- from NADH to FMN
- (results: NADH is oxidized to NAD+ and FMN is reduced to FMNH2)
- 2.FMNH2 passes 2H+ to other side of membrane & passes 2 e- to Q
- (results: FMNH2 is oxidized to FMN & Q picks up additional 2H+ from surroundings and releases it other side of membrane)
3. Q transfers electrons to cytochromes (carrier molecules that are proteins AND an iron group), eventually forming H2
is the final electron acceptor.
4. The extra H+
builds up on one side thus forming an inequality. The extra H then moves thru ATP synthase
(a channel protein).
5. movement of H+
(protons) thru ATP synthase activates this enzyme to combine ADP + P = ATP. This is known as chemoiosmotic theory
(or the proton motive force)
what is chemiosmosis?
a mechanism (ETS) that uses a proton gradient across a cytoplasmic membrane to generate ATP
What is a proton gradient?
the phospholipid membrane is normally impermeable to protons, so when are pumped through, it creates a difference in concentrations of protons on the two sides of a membrane
When is the majority of ATP generated? (which step)
Every NADH = how much ATP?
Every FADH2 = how much ATP?
- NADH yields 3 ATP
- FADH yields 2 ATP
In bacteria where does ETS occur?
in plasma membrane
Overall, what are the start and end products of cellular respiration?
start- sugar/glucose, oxygen, ADP, P
end- CO2, water, ATP
In cellular respiration, prokaryotes (bacteria) generate how much ATP from 1 molecule of glucose? Much much do eukaryotes generate from 1 molecule of glucose?
- Bacteria, 1 glucose= 38 ATP
- Eukaryotes, 1 glucose= 34 ATP *book says 36
this is because some energy gets lost when eukaryotes shuttle the electrons across the mitochondrial membranes that separate glycolysis from the ETS chain. no such separation exists in prokaryotes
What are the physical requirements of microbial growth?
temperature, pH, osmotic pressure
Microorganisms can be grouped by preferred temperature range. What does the following mean?
pyschrophiles- cold loving
pyschrotrophs- cold loving, associated with food spoilage b/c they grow well in refrigerator temps
- mesophiles- moderate temp loving
- thermophiles- heat loving
hyperthermophiles- extreme heat loving (greater than 80o
C, or 176o
what does minimum growth temperature mean?
the lowest temp at which the species will grow
(Each bacterial species grows at a particular temperature)
optimal refers to temp that bacteria grows best
maximum is the highest temp at which growth is possible.
what pH range do bacteria generally grow best in?
grow best in narrow pH range near neutrality (6.5-7.5)
When bacteria is grown/cultured in a lab, what must be added?
(a solution that resists changes in pH when acid or alkali is added to it. Buffers typically involve a weak acid or alkali together with one of its salts)
as bacteria grows, it's waste products tend to be acidic, chemical buffers are added to neutralize the acids & maintain optimal pH range
What is osmotic pressure?
the pressure required to prevent movement of water (no solutes) into a solution containing some solutes.
aka the pressure needed to stop the flow of water across the semipermeable membrane
hypotonic solution equals what for the cell?
hypotonic= water is a plenty in the solution, therefore it moves INTO the cell. If cell wall strong it will swell, if weak it will burst (osmotic lysis)
hypertonic solution equals what for the cell?
hypertonic= less water in solution, therefore it moves OUT OF the cell. cell & cytoplasm shrinks (plasmolysis)
High osmotic pressure (aka hypertonic to cell) has what effect on cells?
removes water from cell. growth of cell becomes limited.
therefore increasing osmotic pressure can stop growth, a form a preservation esp with foods.
Low osmotic pressure (aka hypotonic to cell) what what effect?
water will enter the cell, this leads to lysing
What are the chemical requirements for microbial growth?
sources of carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements (minerals), & organic growth factors
What are obligate anaerobes?
bacteria that are unable to use oxygen for energy-yielding reactions
growth occurs only where there is NO OXYGEN they lack enzymes (e.g. superoxide dismutase or catalase) to neutralize harmful forms of oxygen
microbes that are introduced into a culture medium to initiate growth are called ____?
the microbes that grow & multiply in or on a culture medium are referred to as a culture
what is agar?
a complex polysaccharide derived from marine alda, used as a solidifying agent in culture mediums
what is chemically defined media?
a culture medium in which the exact chemical composition is known
primarily used in lab experimental work
What is complex media?
exact makeup is unknown. usually made up of extracts from yeasts, meats, plants, or proteins.
What is selective media?
designed to suppress growth of unwanted bacteria while encouraging growth of desired bacteria.
What is the streak plate method?
an isolation method used to get pure cultures, as you spread it further apart, the last streak allows bacteria to grow in isolated colonies (insted of on top of one another)
works well if what you're trying to isolate is in large #s compared to rest of sample
What are the 4 phases of growth?
1st - Lag phase: little or no cell ÷, however cells are not dormant, metabolic acitivity is developing
2nd - Log phase: cells ÷ and grow, cell reproduction is most active here & generation time plateaus (reaches minimum constant)
3rd - Stationary phase: growth rate slows, # of cell death balances # of new cells. period of equilibrium
4th - Death phase: # of deaths exceeds # of new cells being formed. continues until tiny fraction remains or dies out entirely
What is EMB
Eosin methylene blue
Commonly used for the preparation of EMB agar which is a differential medium. It slightly inhibits the growth of Gram-positive bacteria.
Provides a color indicator marking microbes that ferment lactose (e.g., E. coli) and those that do not (e.g., Salmonella, Shigella).
Organisms that ferment lactose display "nucleated colonies" -- colonies with dark center
What is PEA?
Phenylethyl Alcohol (PEA) Agar
selective medium used to inhibit the growth of Gram negative organisms, USED TO PROVE GRAM POS.
PEA prevents the growth of Gram-negative organisms by disrupting the sturcture of lipids in the Gram-negative membrane.
What is Mannitol salt agar?
growth mediume. It contains a high concentration of salt. Making it selective for gram + bacterium Staphylococci (since levels of salt is unfavorable to most other bacteria.
S. aureus produce yellow colonies with yellow zones, whereas other Staph produce small pink or red colonies with no colour change to the medium.
What is sterilization?
Destruction / removal of all forms of microbial life, including endospores but w/ possible exception of prions
usually done by steam under pressure or sterilizing gas (eg ethylene oxide)
What is commercial sterilization?
sufficient heat treatment to kill endospores of C. botulinum in canned food
more resistant endspores may survive, but will not germinate & grow under normal storage conditions
what is disinfection?
destruction of vegetative pathogens. chemicals disrupts bacterial walls
- may make use of physical or chemical methods
- eg UV radiation, boiling water
What is antisepsis?
destruction of vegetative pathogens ON LIVING TISSUE (eg human skin)
chemical is then called an antiseptic
What is degerming?
removal of microbes from a limited area, such as the skin around an injection site
mostly mechanical removal by an alcohol-soaked swab
what is sanitization?
Tx methods utilized to keep microbe levels @ a safe public health levels (eating & drinking utensils)
eg high temp. washing or dipping into chemical disinfectant
what is an autoclave? how does it function?
moist heat sterilization. the units can increase pressure, which = increase temp.
What is pasteurization?
another method of moist heat sterilization. mild heating, used on specific foods so has not to permanately damage the food item. eg milk
Name some characteristics of Iodine
- oldest antiseptic
- impairs protein synthesis & alters cell membranes
available as tincture- solution in aqueous alcohol OR iodophor- combo of I and organic molecule when I is released slowly
Types of disinfectants:
halogens are? name 2 examples
effective antimicrobial agents. eg iodine--> betadine & chlorine--> many varities, fluorine, bromide *not used
Types of disinfectants:
phenol is what?
carbolic acid. very effective but now rarely used due to it's odor & irritates the skin.
derivatives are phenolics & bisphenols
Name some characteristics of silver?
- heavy metal
- is antiseptic
- exerts antimicrobial activity (referred to as oligodynamic action)
- Silvadene (topical cream for burns)
- some other metals w. antispetic qualities:
- mercury* no longer used b/c toxic
What are antibiotics? What does broad spectrum mean?
- naturally occurring substances that have either bacteriocidal (killing) or bacteriostatic (inhibits growth) properties.
- many are made from Fungus, particularly streptomyces (more than half of whats used today)
broad= affects both gram + and - bacteria
What are the different mechanisms that antibiotics work? And name some examples in each category
- 1. inhibit cell wall synthesis (particularly peptidoglycan, Gram +). the cell wall weakens = lysis
- E.G. Penicillin, ampicillins, vancomycin, they share chemical structure called "B-Lactam ring"
- 2.inhibits protein synthesis- stops translation, aka protein synthesis. Effective against Gram + and Gram -
- E.G. tetracyclines, streptogramins, chlorampenicol
3. Inhibit Nucleic acid synthesis- common group is - Fluoroquinolones (cipro) interferes with enzymes called gyrases which maintain coiled structure of DNA.
- 4. Transcription blockers- common group is rifamycins. They inhibit synthesis of mRNA
- EG rifampin- used in TB & leprosy
5. Inhibits Metabolic Activity- the Sulfonamides (sulfa drugs). Blocks nucleotide biosynthesis
6. Injures Plasma Membrane- Polmyxin B, binds to membranes of Gram - (eg Pseudomonas). Limited to topical use since it also binds eukaryotic cells too
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