AP Biology — Cellular Respiration & Photosynthesis

Where does the **Krebs Cycle** occur?

The Krebs Cycle occurs in the **mitochondrial matrix**.

What are the main products of the Krebs Cycle?

**NADH, FADH2, CO2, and ATP** are the main products of the Krebs Cycle.

Where does the **Electron Transport Chain** take place?

The Electron Transport Chain occurs in the **inner mitochondrial membrane**.

What is the role of **oxygen** in cellular respiration?

Oxygen acts as the **final electron acceptor** in the Electron Transport Chain, forming water.

What is **oxidative phosphorylation**?

Oxidative phosphorylation is the process where ATP is formed as electrons are transferred from NADH and FADH2 to oxygen by the Electron Transport Chain.

Define **chemiosmosis** in cellular respiration.

Chemiosmosis is the movement of ions across a semipermeable membrane, down their electrochemical gradient, used to generate ATP.

What is the total ATP yield from one glucose molecule in cellular respiration?

The total ATP yield is approximately **30 to 32 ATP** per glucose molecule.

What is the **Calvin Cycle**?

The Calvin Cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis, using ATP and NADPH to convert CO2 into glucose.

Where does **photosynthesis** occur?

Photosynthesis occurs in the **chloroplasts** of plant cells.

What are the two main stages of photosynthesis?

1. **Light-dependent reactions** 2. **Calvin Cycle (Light-independent reactions)**

What is the primary pigment involved in photosynthesis?

**Chlorophyll** is the primary pigment involved in photosynthesis.

What is the equation for photosynthesis?

$6 CO_2 + 6 H_2O + light \rightarrow C_6H_{12}O_6 + 6 O_2$

What is the role of **NADP+** in photosynthesis?

NADP+ acts as an **electron carrier**, becoming reduced to NADPH during the light-dependent reactions, which is then used in the Calvin Cycle.

Where do the **light-dependent reactions** occur?

Light-dependent reactions occur in the **thylakoid membranes** of the chloroplasts.

What is **photophosphorylation**?

Photophosphorylation is the process of generating ATP from ADP and inorganic phosphate during the light reactions of photosynthesis, using a proton gradient.

What is the significance of the **Z-scheme**?

The Z-scheme is a model describing the energy changes of electrons during the light-dependent reactions of photosynthesis, highlighting the electron flow from water to NADP+.

What are **photosystems**?

Photosystems are complexes of proteins and pigments in chloroplasts that play a crucial role in the light reactions of photosynthesis by capturing light energy.

Differentiate between **C3** and **C4** plants.

C3 plants fix CO2 directly through the Calvin Cycle, while C4 plants fix CO2 into a four-carbon compound first, allowing them to photosynthesize efficiently under high light and temperature.

What is **photorespiration**?

Photorespiration is a process where the enzyme RuBisCO oxygenates RuBP, leading to a loss of energy and carbon, occurring under high oxygen and low carbon dioxide conditions.

What is the **CAM pathway**?

The CAM (Crassulacean Acid Metabolism) pathway is a water-conserving, carbon-fixing process where stomata open at night to collect CO2, which is stored as an acid and used during the day.

Define **substrate-level phosphorylation**.

Substrate-level phosphorylation is the direct synthesis of ATP by transferring a phosphate group to ADP from a substrate, occurring in glycolysis and the Krebs Cycle.

What is the role of **RuBisCO**?

RuBisCO is the enzyme that catalyzes the first major step of carbon fixation in the Calvin Cycle, attaching CO2 to RuBP.

How is **ATP synthase** involved in cellular respiration and photosynthesis?

ATP synthase is an enzyme that synthesizes ATP from ADP and inorganic phosphate, driven by a flow of protons across a membrane, occurring in both mitochondria and chloroplasts.

What is the **Warburg effect**?

The Warburg effect is the observation that cancer cells preferentially use glycolysis for energy production, even in the presence of oxygen, leading to increased lactate production.

What are the **products** of the light-dependent reactions?

The products of the light-dependent reactions are **ATP, NADPH, and O2**.

How are **NADH** and **FADH2** used in the electron transport chain?

NADH and FADH2 donate electrons to the electron transport chain, which are used to pump protons, creating a gradient that drives ATP synthesis.

What is **fermentation**?

Fermentation is an anaerobic process that allows for ATP production without oxygen by regenerating NAD+ through the conversion of pyruvate into lactic acid or ethanol.

What is the **pentose phosphate pathway**?

The pentose phosphate pathway is a metabolic process parallel to glycolysis that generates NADPH and ribose-5-phosphate for nucleotide synthesis.

What is **cyclic photophosphorylation**?

Cyclic photophosphorylation is a process in some photosynthetic organisms where electrons are recycled around photosystem I, producing ATP but not NADPH.

What is the **Q cycle**?

The Q cycle is a component of the electron transport chain in mitochondria that contributes to the proton gradient by transferring electrons between ubiquinol and cytochrome c.

What enzyme catalyzes the conversion of pyruvate to acetyl-CoA?

**Pyruvate dehydrogenase** catalyzes the conversion of pyruvate to acetyl-CoA, linking glycolysis to the Krebs Cycle.

What is the **malate-aspartate shuttle**?

The malate-aspartate shuttle is a biochemical system that transfers electrons from NADH in the cytosol to NADH in the mitochondria, enabling the electron transport chain.

What is the role of **cytochrome c** in the electron transport chain?

Cytochrome c is a small heme protein that transfers electrons between Complex III and Complex IV in the electron transport chain.

What is **chlorophyll fluorescence**?

Chlorophyll fluorescence is the emission of light by chlorophyll molecules during return from excited to non-excited states, used as an indicator of photosynthetic activity.

What is the significance of the **proton gradient** in chemiosmosis?

The proton gradient across a membrane stores potential energy that is used by ATP synthase to synthesize ATP during chemiosmosis.