Mock Flashcards
Process of Krebs cycle
- Acetyl from the link reaction combines with a 4C molecule to form a 6C molecule. CoA returns to link reaction.
- 6C molecule (citrate) is converted to a 5C molecule by decarboxylation and dehydrogenation.
- Series of 4C molecules are formed by dehydrogenation.
- NAD and FAD are reduced and carry electrons and protons (H) to the electron transport chain along mitochondria inner membrane
Products of Krebs cycle
- 2 CoA.
- 2 4C molecules (reused in krebs)
- 4 CO2 (waste.
- 2 ATP nucleotides.
- 6 redNAD and 2 redFAD (transport H atoms to e.t.c)
Does yeast carry out aerobic or anaerobic respiration?
Carries out AEROBIC when enough oxygen in present, but in absence of oxygen, must respire ANAEROBICALLY
Yeast suspension in test tube
Oxygen from the air diffuses into suspension from top, so yeast cells at top of test tube respire aerobically. Towards bottom of test tube, the oxygen can’t diffise to the yeast cells quickly enough so they respire anaerobically
What does dehydrogenase activity do?
Removes hydrogen atoms from intermediates, in both types of respiration, and transfers them to hydrogen acceptors
What happens if an artificial hydrogen acceptor is added to the yeast suspension?
Accept the hydrogen atoms and undergo a colour change as the indicator is reduced.
How do you measure the rate of dehydrogenase activity
Add artificial H acceptor to yeast suspension and the time taken for the methylene blue indicator to change colour is the measure
What colour is methylene blue
Blue when oxidised but colourless when reduced
What are competitive enzyme inhibitors
Molecules which have a similar shape to the substrate so can also bind to the active site
How do competitive enzyme inhibitors work?
Similar shape to substrate so they bind to the active site, preventing the actual substrates from colliding with active site. Less successful collisions occur so rate of reaction is reduced
Where are chloroplasts found in plants
In mesophyll cells and guard cells of leaves
Why are chloroplasts mostly found in the palisade mesophyll?
It’s beneath the transparent upper epidermis of the leaf allowing light to penetrate through
Why is the upper surface of a leaf a darker green than lower surface
There are more chloroplasts so more photosynthetic pigment so more light energy can be absorbed
Distribution of chloroplasts within cells in LOW light conditions
Chloroplasts will spread out to form a sheet to maximise the surface area available to absorb light energy
Distribution of chloroplasts within cells in VERY HIGH light conditions
Chloroplasts align themselves in vertical columns along the cellulose cell wall, turning sideways so that light strikes them edge on, to prevent overexposure and damage.
Where does the light dependent stage occur
In thylakoid membranes of chloroplasts
Three main reactions of light dependent stage
Photolysis, ATP is synthesises, NADP is reduced
What is photolysis
Splitting of water molecules by light to produce hydrogen ions, electrons and oxygen.
How is ATP synthesised in light dependent stage?
From ADP+Pi. Photophosphorylation because light is involved.
How is NADP reduced in light dependent stage?
By hydrogen ions to produce reduced NADP
What is a viable count
Count only living cells which are able to grow into visible colonies on an agar plate
Negative of viable count
Population density may be too high to count so a dilution technique is used
Serial dilution process
- Fill 5 test tubes with 9ml sterile water using a pipette
- Add 1ml of sample into first tube to get 10-1 dilution
- Mix 10-1 dilution thoroughly and pipette 1ml into the second test tube to get 10-2 dilution.
4.Repeat until 10-4 dilution is reached.
How to make serial dilution aseptic
Work close to bunsen, put equipment in autoclave, put neck of water tube in bunsen before pouring
Agar plate from serial dilution process
- Take samples from 10-2, 10-3, 10-4 dilutions and spread on agar plate using sterile spreader.
- Prepare 5 agar plates for each dilution to get the average number of colonies.
- Incubate agar plates for 48-72 hours.
- Count colonies on the plates which have 30-300 colonies.
- Under 30 colonies is unreliable and over 300 colonies will merge together so can’t count reliably.
Phases of bacterial growth
Lag, exponential, stationary, death
What is the lag phase
- only a few individuals present.
- adaptation/preparation for growth.
- Intense metabolic activity
What is the exponential phase
- More individuals available for reproduction.
- Cells begin to divide at a constant rate
What is the stationary phase
Reproductive/growth rate is equal to death rate so graph plateaus.
What is the death phase
- death rate greater than growth rate.
- may occur when nutrients are depletes or waste products are at toxic level
Why is ATP seen as a universal energy currency
Because it’s a nucleotide that provides energy for most reactions in all cells
How is energy released from ATP
The terminal bond is broken by hydrolysis, catalysed by ATPase which releases energy
ATP is a means of…
Transferring energy from energy rich compounds who don’t need it (glucose) to cellular reactions where it is needed
Uses of ATP
Active transport, muscle contraction, nerve transmission, endo and exocytosis.
What is chemiosmosis
The flow of protons down an electrochemical gradient through ATP synthetase which provides the potential energy necessary to synthesize ATP by phosphorylation.
Chemiosmosis in chloroplasts
- Protons pumped across the THYLAKOID membrane by proton pumps fuelled by electron energy
- A high concentration of protons build up in THYLAKOID SPACE.
- Protons flow down STALKED PARTICLES CONTAINING ATP SYNTHETASE, down a concentration gradient to provide energy for ATP synthesis.
- Free electrons taken up by a final electron acceptor in STROMA
Chemiosmosis in mitochondrion
- Protons pumped across CRISTA by proton pumps fuelled by electron energy
- A high concentration of protons build up in INTERMEMBRANE SPACE.
- Protons flow down STALKED PARTICLES CONTAINING ATP SYNTHETASE, down a concentration gradient to provide energy for ATP synthesis.
- Free electrons taken up by a final electron acceptor in the MATRIX.
Link of krebs cycle to electron transport chain
By end of krebs, the glucose molecule has been completely oxidised but much of the energy is in the form of H atoms so they’re attached to H carriers and taken to inner membranes of the mitochondria and to electron transport chain. H split into e- and H+
Electron transport chain process
- e- pass along electron carriers within the inner membrane which provides the energy needed to drive proton pumps.
- H ions are pumped into the intermembrane space from the matrix by the proton pump mechanism.
- H ions diffuse back into matrix via stalked particles attached to ATP synthetase.
- electrochemical gradient generated by the flow of H ions through the stalked particles generates energy needed to produce ATP by chemiosmosis
Where does the energy for oxidative phosphorylation come from
As electrons jump from carrier to carrier, energy level drops and is passed to pumps to pump H+. Channel proteins carry H+ down, creating an electrochemical gradient. The flow of charge provides the energy needed.
Size of a population is determined by
Birth rate, death rate, immigration and emigration
Assumptions made when sampling by capture/recapture
- sample represents true population.
- tag doesn’t conder a disadvantage.
- will mix completely randomly when reintroduced.
- no predation or migration
If a tag is to cut a toe off, what are the disadvantages
Open wound will made them more susceptible to infection.
Too scared to mix randomly.
Can’t swim as well so preyed on
What is gram’s stain used for
To classify bacteria by distinguishing between different bacterial cell walls
Gram’s stain process
- Smear actively growing bacteria on a slide.
- Heat fix then stain with crystal violet and dilute iodine.
- Wash slide off with ethanol
- Gram positive retain the stain and show up purple.
- Gram negative loses the stain as it’s washed away with the ethanol.
- Gram negative can be counterstained with a stain such as safranin O (red)
Gram negative bacteria
- thin outer wall of peptidoglycan.
- extra outer membrane with lipoproteins and lipopolysaccharides.
- not stained purple - lipid containing molecules are disrupted by ethanol so violet leaks out of cell.
- counter stain turns cells red.
What does the extra outer membrane on gram negative do?
Protects peptidoglycan from antimicrobial agents like lysozyme and penicillin
Gram positive bacteria
- Thick outer wall of peptidoglycan.
- Stained purple by gram stain protocol - decolourisation stage closes pores in peptidoglycan so violet is retained.
What is a bacillus
Rod shaped single bacteria
What is a cocci
Spherical bacteria which can occur singly, in pairs or in clusters
What is a spirillum
Rigid spiral structure bacteria which is thick, long and moves with flagella
What are density dependent factors
The effect of density dependent factors increase as the density of the population increases. Biotic
Examples of density dependent factors
-Competition
-Predation
-Disease
-Parasitism.
What do density dependent factors do
Limit the maximum size of the population: determine carrying capacity.
Weaken individuals and make them less likely to reproduce successfully.
