Chapter 6A
What are the three basic requirements for a cell to function?
A membrane, genetic information, and energy.
When ATP is hydrolyzed, what products are formed?
ADP + Pi (inorganic phosphate)
What part of cellular respiration produces the most ATP?
Oxidative phosphorylation (electron transport chain)
In oxidative phosphorylation, what drives ATP synthase?
The proton gradient across the mitochondrial membrane
What is the main pigment that absorbs light energy?
Chlorophyll
Do weak covalent bonds have more or less potential energy than strong covalent bonds and why?
Less because they are less stable and require more energy to remain intact.
What type of reaction is ATP hydrolysis: exergonic or endergonic?
Exergonic
What molecule acts as the final electron acceptor in cellular respiration and what does it form?
O2 form water
What molecule is regenerated during fermentation that allows glycolysis to continue?
NAD+
What are the reactants and products of photosynthesis?
CO2 + H2O + light into glucose + O2
ΔH = 50 kJ, TΔS = 30 kJ. What is ΔG and what kind of reaction is it?
ΔG = 50 − 30 = +20 kJ Since ΔG > 0, the reaction is endergonic
What type of inhibitor binds at a site other than the active site?
Noncompetitive inhibitor.
What happens during pyruvate oxidation?
Pyruvate is converted to acetyl-CoA, releasing CO₂ and producing NADH
What happens to pyruvate in the absence of oxygen in animals?
It is reduced to lactic acid (fermentation)
What is the “Z scheme”?
A diagram showing electron energy levels as they move from PSII to PSI
ΔG1 = −12 kJ, ΔG2 = +8 kJ, ΔG3 = −6 kJ. What is net ΔG and is this pathway spontaneous?
−10 kJ Since ΔG < 0, the pathway is spontaneous
Why is enzyme regulation important for metabolism?
It ensures energy and resources aren’t wasted, controlling metabolic pathways efficiently.
What are the main products of the citric acid cycle per acetyl-CoA molecule?
3 NADH, 1 FADH₂, 1 ATP, and 2 CO2
How is cellular respiration slowed when the cell has enough energy?
High ATP or NADH levels inhibit key enzymes like PFK-1 (feedback inhibition)
Why must plants have both chloroplasts and mitochondria?
ATP produced in the chloroplast stays there for carbon fixation; mitochondria generate ATP for the rest of the cell’s processes
Explain why cells must constantly obtain and transform energy, even though the total energy in the universe remains constant.
Because energy transformations increase entropy, cells must continually obtain energy to maintain order and perform work despite the universal increase in entropy
How does the lowering of activation energy by a enzyme impact the ΔG and why?
Enzymes only change the reaction rate by providing an alternate pathway; they do not alter the reactants’ or products’ free energies, so ΔG remains unchanged.
What molecule is oxidized and what molecule is reduced during cellular respiration overall and what dp they form?
Glucose is oxidized to carbon dioxide; oxygen is reduced to water.
What are two forms glucose is stored as and where are they found?
Glycogen in animals; starch in plants
Why is Rubisco so inefficient?
It cannot discriminate between O2 and CO2, initiating photorespiration which uses up energy and creates unwanted CO2; it is a slow enzyme in general