Photosynthesis and Cellular Respiration: Calvin Cycle, Electron Transport, and Fermentation

What is the Calvin-Benson Cycle?

A process that occurs in the stroma of chloroplasts, where atmospheric CO2 is converted into energy-rich molecules like G3P.

What enzyme is involved in the first major step of carbon fixation?

Rubisco

What is the equation summarizing the Calvin cycle?

3 CO2 + 9 ATP + 6 NADPH -> 1 net G3P + regenerated ADP, Pi, and NADP+.

What are the three phases of the Calvin cycle?

1. Fixation: 3 RuBP + 3 CO2 -> 6 3-phosphoglycerate. 2. Reduction: 6 3-phosphoglycerate + 6 ATP + 6 NADPH -> 5 G3P + 1 G3P. 3. Regeneration: 5 G3P + 3 ATP -> 3 RuBP.

What is photorespiration?

A process where Rubisco oxygenates RuBP, wasting energy produced by photosynthesis.

How does photorespiration affect C3 plants?

It can reduce photosynthetic output by approximately 25%.

What is the primary acceptor of CO2 in C3 pathways?

RuBP (a six-carbon compound).

What is the first stable product in C3 photosynthesis?

3-phosphoglycerate.

What distinguishes C4 pathways from C3 pathways?

C4 pathways use phosphoenol pyruvate as the primary CO2 acceptor and occur in both mesophyll and bundle-sheath cells.

What is the first stable product in C4 photosynthesis?

Oxaloacetic acid.

What is Crassulacean Acid Metabolism (CAM)?

A process that captures CO2 at night and stores it in organic acids for use during the day.

What are the main photosynthetic organs of a plant?

Leaves.

What is the photosynthetic organelle of a plant?

Chloroplast.

What is the role of stomata in plants?

They allow CO2 to enter and oxygen to leave the plant.

What is the structure of a chloroplast?

It has a triple membrane system: outer membrane, inner membrane, and thylakoid membrane.

What evidence supports the Endosymbiotic Theory?

Chloroplasts and mitochondria have their own DNA, bacterial-like ribosomes, divide by binary fission, and have double membranes.

What is the function of thylakoids in chloroplasts?

They are involved in the light reactions of photosynthesis.

Where do the light reactions of photosynthesis occur?

In the thylakoid membranes.

Where does the Calvin cycle take place?

In the stroma of chloroplasts.

What is the main output of the Calvin cycle?

G3P, which can be used to form glucose.

What are the inputs required for the light reactions?

Light, water, NADP+, ADP, and inorganic phosphate (Pi).

What are the outputs of the light reactions?

Oxygen, NADPH, and ATP.

What is the significance of G3P in photosynthesis?

G3P is a small sugar molecule that can be used to synthesize glucose and other carbohydrates.

How do C4 plants minimize photorespiration?

By separating CO2 fixation and the Calvin cycle in different cell types.

What is the role of mesophyll cells in C4 photosynthesis?

They capture CO2 and convert it into a four-carbon compound before delivering it to bundle-sheath cells.

What is the significance of ATP and NADPH in the Calvin cycle?

They provide the energy and reducing power needed to convert CO2 into G3P.

What happens to ADP, Pi, and NADP+ after the Calvin cycle?

They return to the light reactions to be reused.

What is the stroma?

The fluid surrounding the thylakoids in chloroplasts.

What cycle occurs in the stroma?

The Calvin cycle.

What is photolysis?

The splitting of water molecules during photosynthesis, releasing oxygen.

What does Photosystem II do?

It provides electrons for photosynthesis and splits water to release oxygen.

What is the role of NADP+ in photosynthesis?

It is reduced to NADPH during the light reactions.

What is cyclic photophosphorylation?

A process involving only Photosystem I that produces ATP without releasing oxygen.

What is noncyclic photophosphorylation?

A process involving both Photosystem I and II that produces ATP and NADPH and releases oxygen.

What is the active reaction center of Photosystem II?

P680.

What is the active reaction center of Photosystem I?

P700.

What is the main purpose of the electron transport chain in photosynthesis?

To create a proton gradient used to produce ATP.

What is the overall equation for cellular respiration?

C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O.

What is metabolism?

The combination of chemical reactions an organism undergoes to build up or break down materials.

What is ATP?

A molecule that cells use to store and release energy.

What are aerobic processes?

Processes that require oxygen and occur when O2 is available.

What are anaerobic processes?

Processes that do not require oxygen and occur in many single-celled prokaryotes.

What is the significance of the endosymbiotic hypothesis?

It explains the origin of mitochondria and chloroplasts from engulfed bacteria.

What is the role of hydrogen ions (protons) in photosynthesis?

They help create a proton gradient used by ATP synthase to generate ATP.

What happens during the Calvin cycle?

Carbon dioxide is fixed into sugar using ATP and NADPH produced in the light reactions.

What is the function of ATP synthase?

To produce ATP from ADP and inorganic phosphate using the proton gradient.

How do plants capture sunlight?

Through chlorophyll in chloroplasts during the light reactions.

What is the relationship between photosynthesis and cellular respiration?

Photosynthesis converts light energy into chemical energy, while cellular respiration releases that energy for cellular use.

What is the importance of the proton gradient in photosynthesis?

It drives ATP production during the light reactions.

What does NADPH carry to the Calvin cycle?

Reducing power needed for sugar synthesis.

What is the main product of cyclic photophosphorylation?

Only ATP is produced.

What is the main product of noncyclic photophosphorylation?

Both ATP and NADPH are produced, along with the release of oxygen.

What happens to glucose during cellular respiration?

Glucose is oxidized to produce CO2, water, and ATP energy.

What is the primary location for most reactions of cellular respiration?

Mitochondria

What are the three main steps of cellular respiration?

Glycolysis, Krebs cycle (citric acid cycle), and Electron transport chain.

Where does glycolysis occur?

In the cytoplasm.

What is the net gain of ATP from glycolysis?

2 ATP molecules per molecule of glucose.

What is produced from one molecule of glucose during glycolysis?

Two molecules of pyruvic acid and two NADH.

What is the role of NAD+ in glycolysis?

It acts as an electron carrier, converting to NADH.

What is the Krebs cycle also known as?

The citric acid cycle.

Where does the Krebs cycle take place?

In the matrix of the mitochondria.

What are the products of one turn of the Krebs cycle?

3 NADH, 1 FADH2, 1 ATP, and 2 CO2.

How many turns of the Krebs cycle are needed for one glucose molecule?

Two turns.

What is the final stage of aerobic cellular respiration?

The electron transport chain.

What is the main function of the electron transport chain?

To use high-energy electrons to convert ADP to ATP.

What process powers ATP production in the electron transport chain?

Chemiosmosis.

What is the role of oxygen in the electron transport chain?

Oxygen accepts electrons and protons to form water.

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

About 36 ATP molecules.

What percentage of energy in glucose is captured as ATP during cellular respiration?

About 36%.

What is the relationship between cellular respiration and photosynthesis?

The products of one process are the reactants of the other.

What are the overall equations for cellular respiration and photosynthesis?

Cell respiration: C6H12O6 + 6 O2 -> 6 CO2 + 6 H2O; Photosynthesis: 6 CO2 + 6 H2O -> C6H12O6 + 6 O2.

What is released as a waste product during the Krebs cycle?

Carbon dioxide (CO2).

What is the role of ATP synthase in cellular respiration?

It synthesizes ATP as protons flow through it during chemiosmosis.

What happens to the remaining energy in glucose after ATP production?

About 64% is released as heat.

What is the significance of the proton gradient in the electron transport chain?

It powers ATP production through chemiosmosis.

What happens to pyruvic acid after glycolysis?

It is converted to acetyl-CoA for the Krebs cycle.

What is the initial molecule formed in the Krebs cycle?

Citrate (citric acid).

What are the energy carrier molecules produced in the Krebs cycle?

NADH and FADH2.

What is the role of the cristae in mitochondria?

It houses the proteins and molecules of the electron transport chain.

How does glycolysis contribute to the Krebs cycle?

It provides pyruvic acid, which is used in the Krebs cycle.

What is the primary function of photosynthesis?

To convert carbon dioxide and water into glucose and oxygen using sunlight.

What is the primary function of cellular respiration?

To convert glucose and oxygen into carbon dioxide, water, and ATP (energy).

What is fermentation?

An anaerobic process of producing ATP from food in the absence of oxygen.

What are the two main types of fermentation?

Alcoholic fermentation and lactic acid fermentation.

Where does fermentation occur in the cell?

In the cytoplasm.

What is produced during alcoholic fermentation?

Ethanol (alcohol) and carbon dioxide.

What is produced during lactic acid fermentation?

Lactic acid.

What is the net ATP yield from glycolysis?

2 ATP.

What is the role of NAD+ in fermentation?

To regenerate NAD+ so that glycolysis can continue.

What happens to pyruvate during lactic acid fermentation?

It is converted into lactic acid.

What happens to pyruvate during alcoholic fermentation?

It is converted into ethanol and carbon dioxide.

What are the three stages of cellular respiration?

Glycolysis, Krebs cycle, and electron transport chain.

What is the main energy currency of the cell?

ATP (adenosine triphosphate).

How many ATP are produced by the electron transport chain?

34 ATP.

What is released when a phosphate group is removed from ATP?

Energy.

What is the waste product of the Krebs cycle that we exhale?

Carbon dioxide (CO2).

What is the process called that produces energy in an animal cell?

Cellular respiration.

What does glycolysis convert glucose into?

2 molecules of pyruvate.

What is the significance of lactic acid buildup during exercise?

It causes a sore/burning sensation in muscles.

What suffix indicates a sugar molecule?

-ose.