Flashcard Set14 cards

AP Biology: Cellular Energetics

Unit 3 — enzymes, cellular respiration, and photosynthesis, drilled to AP-exam rigor.

Free to study. No account needed.

How does an enzyme's active site achieve substrate specificity?

Through compatible chemical properties (such as charge and hydrophobicity) and a precise physical shape that matches the target substrate.

1 / 14

All 14 cards

1
How does an enzyme's active site achieve substrate specificity?
Through compatible chemical properties (such as charge and hydrophobicity) and a precise physical shape that matches the target substrate.
2
How do enzymes accelerate chemical reactions without changing the overall free energy change (ΔG) of the reaction?
By lowering the activation energy (Ea) required to reach the unstable transition state.
3
Why does a temperature increase past an enzyme's optimum cause a rapid drop in reaction rate, whereas a temperature decrease does not?
High temperatures disrupt weak intramolecular bonds (like hydrogen bonds), denaturing the active site. Low temperatures only decrease kinetic energy and molecular collision rates without destroying enzyme structure.
4
Exergonic cellular processes, such as the hydrolysis of ATP, are linked to endergonic processes through a mechanism known as ___ ___.
energy coupling
5
What is the evolutionary significance of glycolysis occurring exclusively in the cytosol across all three domains of life?
It indicates that glycolysis evolved in a common ancestor before the evolution of membrane-bound organelles (like mitochondria) and prior to the rise of atmospheric oxygen.
6
What is the net yield of ATP and NADH per molecule of glucose oxidized during the process of glycolysis?
A net yield of 2 ATP (via substrate-level phosphorylation) and 2 NADH.
7
What is the primary metabolic function of the Krebs (Citric Acid) Cycle in cellular respiration?
To fully oxidize acetyl-CoA, releasing carbon dioxide (CO₂) and transferring high-energy electrons to the coenzymes NAD⁺ and FAD.
8
Describe the spatial model of the mitochondrial electron transport chain. Where are the electron carriers located, and into which space are protons (H⁺) pumped?
The electron transport carriers are embedded in the inner mitochondrial membrane; they pump protons from the mitochondrial matrix into the intermembrane space.
9
The flow of protons down their electrochemical gradient through the enzyme ___ ___ drives the phosphorylation of ADP to ATP via chemiosmosis.
ATP synthase
10
If an uncoupling chemical makes the inner mitochondrial membrane permeable to protons, how are ATP synthesis and oxygen consumption affected?
ATP synthesis stops because the proton gradient is destroyed, but oxygen consumption continues (or increases) as the electron transport chain operates at maximum capacity to try to re-establish the gradient.
11
What is the immediate source of electrons used to replace those lost by the chlorophyll a molecules (P680) in Photosystem II?
Water (H₂O), which undergoes photolysis to release electrons, protons (H⁺), and oxygen gas (O₂).
12
Contrast the spatial direction of proton pumping during chemiosmosis in chloroplasts versus mitochondria.
In chloroplasts, protons are pumped from the stroma into the thylakoid lumen; in mitochondria, protons are pumped from the matrix into the intermembrane space.
13
RuBisCO
The enzyme that catalyzes the initial fixation of inorganic carbon dioxide (CO₂) to the 5-carbon sugar ribulose 1,5-bisphosphate (RuBP) in the Calvin cycle.
14
Why is the Calvin cycle (light-independent reactions) dependent on the functioning of the light-dependent reactions to produce G3P?
The Calvin cycle requires the chemical energy of ATP and the reducing power of NADPH, both of which are direct products of the light-dependent reactions.