Flashcard Set

AP Biology: Cellular Energetics

14 cards

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

1
Term
How does an enzyme's active site achieve substrate specificity?
Definition
Through compatible chemical properties (such as charge and hydrophobicity) and a precise physical shape that matches the target substrate.
2
Term
How do enzymes accelerate chemical reactions without changing the overall free energy change (ΔG) of the reaction?
Definition
By lowering the activation energy (Ea) required to reach the unstable transition state.
3
Term
Why does a temperature increase past an enzyme's optimum cause a rapid drop in reaction rate, whereas a temperature decrease does not?
Definition
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
Term
Exergonic cellular processes, such as the hydrolysis of ATP, are linked to endergonic processes through a mechanism known as ___ ___.
Definition
energy coupling
5
Term
What is the evolutionary significance of glycolysis occurring exclusively in the cytosol across all three domains of life?
Definition
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
Term
What is the net yield of ATP and NADH per molecule of glucose oxidized during the process of glycolysis?
Definition
A net yield of 2 ATP (via substrate-level phosphorylation) and 2 NADH.
7
Term
What is the primary metabolic function of the Krebs (Citric Acid) Cycle in cellular respiration?
Definition
To fully oxidize acetyl-CoA, releasing carbon dioxide (CO₂) and transferring high-energy electrons to the coenzymes NAD⁺ and FAD.
8
Term
Describe the spatial model of the mitochondrial electron transport chain. Where are the electron carriers located, and into which space are protons (H⁺) pumped?
Definition
The electron transport carriers are embedded in the inner mitochondrial membrane; they pump protons from the mitochondrial matrix into the intermembrane space.
9
Term
The flow of protons down their electrochemical gradient through the enzyme ___ ___ drives the phosphorylation of ADP to ATP via chemiosmosis.
Definition
ATP synthase
10
Term
If an uncoupling chemical makes the inner mitochondrial membrane permeable to protons, how are ATP synthesis and oxygen consumption affected?
Definition
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
Term
What is the immediate source of electrons used to replace those lost by the chlorophyll a molecules (P680) in Photosystem II?
Definition
Water (H₂O), which undergoes photolysis to release electrons, protons (H⁺), and oxygen gas (O₂).
12
Term
Contrast the spatial direction of proton pumping during chemiosmosis in chloroplasts versus mitochondria.
Definition
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
Term
RuBisCO
Definition
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
Term
Why is the Calvin cycle (light-independent reactions) dependent on the functioning of the light-dependent reactions to produce G3P?
Definition
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.