Ch. 6 MICRO
In the process of oxidative phosphorylation, the energy of proton motive force is used to generate
ATP
Which of these is not a coenzyme?
ATP
What would happen if ribulose 1,5-bisphosphate (RuBP) were depleted in a cell?
The Calvin cycle would stop.
Fermentation is used as a means of preserving foods. Why would it slow spoilage?
The acids produced inhibit many spoilage organisms.
How would cellulose-degrading bacteria in the rumen of a cow benefit the animal?
They break down cellulose, allowing cows to use the component subunits. Cows do not produce cellulase. Without the bacteria, cows could not digest cellulose.
Explain why sulfa drugs prevent bacterial growth without harming the human host.
They competitively inhibit an enzyme that is unique to microorganisms; human cells lack the enzyme, and therefore are not harmed.
Which of the following statements is false?
convert coenzymes to products
In fermentation, the terminal electron acceptor is
An organic compound
Why do cells secrete hydrolytic enzymes?
Because they cannot bring most macromolecules into the cell. By secreting hydrolytic enzymes they break the macromolecules into their component subunits, which can be transported into the cell.
Explain the function of a coenzyme.
Coenzymes carry molecules or electrons.
Why is the overall ATP yield in aerobic respiration only a theoretical number?
Different prokaryotes have different components to their electron transport chain, and proton motive force can be used for purposes other than ATP generation.
How does the fate of electrons carried by NADPH differ from the fate of electrons carried by NADH?
Electrons carried by NADPH are used in biosynthesis whereas those carried by NADH are passed to the electron transport chain.
Which compound contains more free energy—glucose or oxaloacetate? On what did you base your conclusion?
Glucose. It has less affinity for its electrons (see figure 6.7).
The major pathway(s) of central metabolism are
Glycolysis , the TCA Cycle and the pentose Phosphate pathway
Which energy source, Fe2+ or H2S, would result in the greatest energy yield when O2 is used as a terminal electron acceptor (hint: refer to figure 6.7)?
H2S
Which of these factors does not affect enzyme activity?
Humidity
How does the "investment phase" of glycolysis effect the net yield of ATP in that pathway?
If energy were not spent in the "investment phase" then all four ATPs made in the "payoff phase" could be used for other purposes.
Why is it important for a cell that allosteric inhibition be reversible?
If it were not reversible, then cells would need to synthesize additional enzymes to replace the ones that were inhibited, which would waste energy and take additional time.
With a branched biochemical pathway, why would it be important for a cell to shut down the first step as well as branching steps?
If the cell couldn't do that, and it had sufficient levels of the endproducts of the pathway, then the product of the step before the branch would accumulate.
Why does fermentation supply less energy than respiration?
It does not oxidize glucose completely; the electrons are passed to an intermediate in the breakdown process.
β-carotene is a carotenoid that mammals can use as a source of vitamin A. What is the function of carotenoids in photosynthetic organisms?
It is an accessory pigment that captures the radiant energy.
What is the role of rubisco?
It is the enzyme in the Calvin cycle that joins CO2 to an organic compound.
Explain why glutamate synthesis is particularly important for a cell.
It provides a way for cells to incorporate ammonium into organic material.
In the TCA cycle, the carbon atoms contained in acetate are converted into
LACTIC ACID, GLUCOSE,GLYCEROL AND CO2
What three general products of the central metabolic pathways does a cell require to carry out biosynthesis?
Precursor metabolites, ATP, and reducing power (in the form of NADPH)
What is the end product of glycolysis?
Pyruvate
Which central metabolic pathway generates the most reducing power?
TCA cycle
Which of these pathways gives a cell the potential to produce the most ATP?
TCA cycle
Degradation of fats as an energy source involves all of the following except
TRANSAMINATION
Energy is required to reverse the flow of the electron transport chain. Why would this be so?
The "normal" flow of the electron transport chain releases energy so it makes sense that the reverse would require energy. Reversing the electron transport chain takes electrons from a low-energy substance and transfers them to a higher-energy substance electron.
Electrons carried by NADPH are used in biosynthesis whereas those carried by NADH are passed to the electron transport chain.
They are used in both catabolism and anabolism (amphi means "both kinds").
What is the advantage of having tandem photosystems?
The tandem photosystems can raise the energy level of electrons stripped from water to a high enough level that they can be used to generate ATP.
Explain the process used to degrade fatty acids.
They are degraded using -oxidation, which transfers 2 carbon units from the end of the fatty acid to coenzyme A, forming acetyl-CoA.
Describe the roles of hydrogen sulfide and carbon dioxide in chemolithoautotrophic metabolism.
They are energy sources; prokaryotes oxidize them to harvest energy.
Why would a cell ferment rather than respire?
They ferment if a suitable inorganic terminal electron acceptor is not available, or if they lack an electron transport chain.
How do the methyl-red and Voges-Proskauer tests differentiate between certain members of the Enterobacteriaceae?
They test for fermentation end products, allowing members of the Enterobacteriaceae that use the 2,3 butanediol pathway to be distinguished from those that use the mixed acid pathway.