AP Biology unit 3 - photosynthesis, cellular respiration, fermentation

PHOTOSYNTHESIS — What is its overall purpose?

Convert light energy into chemical energy stored in sugars.

PHOTOSYNTHESIS — Where does it occur?

In chloroplasts.

PHOTOSYNTHESIS — What are its two stages?

Light-dependent reactions and the Calvin cycle.

PHOTOSYNTHESIS — What are the overall reactants?

Carbon dioxide, water, and light energy.

PHOTOSYNTHESIS — What are the overall products?

Sugar and oxygen.

PHOTOSYNTHESIS — What is the overall equation?

6CO2 + 6H2O + light → C6H12O6 + 6O2.

LIGHT REACTIONS — What is the purpose?

Convert light energy into chemical energy stored in ATP and NADPH.

LIGHT REACTIONS — Where do they occur?

Thylakoid membrane of the chloroplast.

LIGHT REACTIONS — What are the reactants?

Light, H2O, ADP + Pi, and NADP+.

LIGHT REACTIONS — What are the products?

O2, ATP, and NADPH.

LIGHT REACTIONS — Why do they matter?

They supply ATP and NADPH for the Calvin cycle.

LIGHT REACTIONS STEP 1 — What happens at Photosystem II?

Chlorophyll absorbs light, exciting electrons to higher energy levels.

LIGHT REACTIONS STEP 2 — What happens during photolysis?

Water splits to replace lost electrons, releasing electrons, H+, and O2.

LIGHT REACTIONS STEP 3 — What happens in the electron transport chain?

Electrons move through proteins, losing energy; released energy pumps H+ into the thylakoid lumen.

LIGHT REACTIONS STEP 4 — How is ATP made?

H+ flows through ATP synthase into the stroma, powering ADP + Pi → ATP.

LIGHT REACTIONS STEP 5 — What happens at Photosystem I?

Light re-energizes electrons, which help reduce NADP+ to NADPH.

PHOTOSYNTHESIS — What is photolysis?

Light-driven splitting of water that replaces electrons and releases oxygen.

PHOTOSYNTHESIS — Where do H+ ions accumulate during light reactions?

In the thylakoid lumen.

PHOTOSYNTHESIS — Which way do H+ ions flow through ATP synthase?

From the thylakoid lumen into the stroma.

PHOTOSYNTHESIS — What is chemiosmosis?

H+ flows down its electrochemical gradient through ATP synthase to produce ATP.

PHOTOSYNTHESIS — What does chlorophyll do?

Absorbs light energy to excite electrons.

PHOTOSYNTHESIS — What does NADP+ do?

Accepts high-energy electrons and H+ to form NADPH.

PHOTOSYNTHESIS — What does ATP do in the Calvin cycle?

Supplies energy for the reactions.

PHOTOSYNTHESIS — What does NADPH do in the Calvin cycle?

Provides high-energy electrons for reducing carbon compounds.

CALVIN CYCLE — What is its purpose?

Use CO2, ATP, and NADPH to produce G3P.

CALVIN CYCLE — Where does it occur?

Chloroplast stroma.

CALVIN CYCLE — What are its reactants?

CO2, ATP, and NADPH.

CALVIN CYCLE — What are its products?

G3P, ADP + Pi, and NADP+.

CALVIN CYCLE — Why does it matter?

It incorporates inorganic CO2 into organic molecules used to build sugars.

CALVIN CYCLE STEP 1 — What happens during carbon fixation?

RuBisCO attaches CO2 to RuBP; the unstable product splits into two 3-PGA molecules.

CALVIN CYCLE STEP 2 — What happens during reduction?

ATP and NADPH help convert 3-PGA into G3P.

CALVIN CYCLE STEP 3 — What happens to G3P?

Some leaves the cycle and can be used to build glucose and other molecules.

CALVIN CYCLE STEP 4 — What happens during regeneration?

ATP helps regenerate RuBP so the cycle can continue.

CALVIN CYCLE — What does RuBisCO do?

Catalyzes carbon fixation by attaching CO2 to RuBP.

CALVIN CYCLE — What is RuBP?

A five-carbon molecule that accepts CO2 and is regenerated in the cycle.

CALVIN CYCLE — What is G3P?

A three-carbon sugar used to build glucose and other organic molecules.

CALVIN CYCLE — How much net G3P is made per 3 CO2?

One net G3P molecule.

CALVIN CYCLE — How much ATP and NADPH are needed per net G3P?

9 ATP and 6 NADPH.

CALVIN CYCLE — Does it directly produce glucose?

No. Its direct net sugar product is G3P.

CELLULAR RESPIRATION — What is its purpose?

Break down glucose and transfer its energy into ATP.

CELLULAR RESPIRATION — What are its four stages?

Glycolysis, pyruvate oxidation, citric acid cycle, and oxidative phosphorylation.

CELLULAR RESPIRATION — What are the overall reactants?

Glucose and oxygen.

CELLULAR RESPIRATION — What are the overall products?

Carbon dioxide, water, and ATP.

CELLULAR RESPIRATION — What is its overall equation?

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy captured in ATP.

GLYCOLYSIS — What is its purpose?

Split glucose into two pyruvate molecules and produce ATP and NADH.

GLYCOLYSIS — Where does it occur?

Cytoplasm.

GLYCOLYSIS — What are its reactants?

Glucose, 2 ATP invested, 2 NAD+, and ADP + Pi.

GLYCOLYSIS — What are its products per glucose?

2 pyruvate, net 2 ATP, 2 NADH, and water.

GLYCOLYSIS — Why does it matter?

It begins glucose breakdown, makes ATP, and supplies pyruvate.

GLYCOLYSIS STEP 1 — What happens during energy investment?

cell invests 2 ATP to destabilize glucose

GLYCOLYSIS STEP 2 — What happens when glucose is split?

A six-carbon sugar splits into two three-carbon pyruvate.

GLYCOLYSIS STEP 3 — What happens during oxidation?

Electrons transfer to NAD+, producing NADH.

GLYCOLYSIS STEP 4 — How is ATP produced?

Substrate-level phosphorylation transfers phosphate groups to ADP.

GLYCOLYSIS STEP 5 — What are the final products?

2 pyruvate, 2 NADH, and net 2 ATP per glucose.

GLYCOLYSIS — How much ATP is invested and produced?

2 ATP invested; 4 produced; net gain of 2 ATP.

CELLULAR RESPIRATION — What is substrate-level phosphorylation?

Direct transfer of a phosphate group to ADP to make ATP.

AFTER GLYCOLYSIS — What happens to pyruvate when aerobic respiration continues?

Pyruvate enters the mitochondrial matrix and undergoes pyruvate oxidation.

AFTER GLYCOLYSIS — What alternative pathway can regenerate NAD+?

Fermentation.

FERMENTATION — What is its main purpose?

Regenerate NAD+ from NADH so glycolysis can continue.

FERMENTATION — Where does it occur?

Cytoplasm.

FERMENTATION — What are its two common types?

Lactic acid fermentation and alcoholic fermentation.

LACTIC ACID FERMENTATION — What happens?

Pyruvate accepts electrons from NADH, forming lactate and regenerating NAD+.

LACTIC ACID FERMENTATION — Which organisms use it?

Some bacteria and animal muscle cells when oxygen availability cannot meet demand.

ALCOHOLIC FERMENTATION — What happens?

Pyruvate releases CO2; acetaldehyde accepts electrons from NADH to form ethanol, regenerating NAD+.

ALCOHOLIC FERMENTATION — Which organisms use it?

Yeasts and some microorganisms.

FERMENTATION — Does it produce additional ATP?

No. Glycolysis provides a net 2 ATP per glucose.

FERMENTATION — Why is NAD+ essential?

It allows glycolysis to continue by accepting electrons during glucose breakdown.

FERMENTATION — Does it use the mitochondrial ETC?

No. It occurs in the cytoplasm and does not use the ETC.

PYRUVATE OXIDATION (prep reaction) — What is its purpose?

Convert pyruvate into acetyl-CoA for the citric acid cycle.

PYRUVATE OXIDATION — Where does it occur?

Mitochondrial matrix in eukaryotes.

PYRUVATE OXIDATION — What are its reactants per glucose?

2 pyruvate, 2 NAD+, and 2 coenzyme A.

PYRUVATE OXIDATION — What are its products per glucose?

2 acetyl-CoA, 2 CO2, and 2 NADH.

PYRUVATE OXIDATION — Why does it matter?

It links glycolysis to the citric acid cycle and captures electrons in NADH.

PYRUVATE OXIDATION STEP 1 — What happens to pyruvate?

Each three-carbon pyruvate loses one carbon as CO2.

PYRUVATE OXIDATION STEP 2 — What happens to the remaining fragment?

It is oxidized, transferring electrons to NAD+ to form NADH.

PYRUVATE OXIDATION STEP 3 — How is acetyl-CoA formed?

Coenzyme A attaches to the remaining two-carbon acetyl group.

PYRUVATE OXIDATION — Does it produce ATP directly?

No.

CITRIC ACID CYCLE — What is its purpose?

Oxidize acetyl groups, release CO2, and produce electron carriers and ATP.

CITRIC ACID CYCLE — Where does it occur?

Mitochondrial matrix.

CITRIC ACID CYCLE — What are its reactants per glucose?

2 acetyl-CoA, 6 NAD+, 2 FAD, and ADP + Pi.

CITRIC ACID CYCLE — What are its products per glucose?

4 CO2, 6 NADH, 2 FADH2, and 2 ATP.

CITRIC ACID CYCLE — Why does it matter?

It releases carbon as CO2 and makes electron carriers for oxidative phosphorylation.

CITRIC ACID CYCLE STEP 1 — What forms when acetyl-CoA enters?

The two-carbon acetyl group combines with four-carbon oxaloacetate to form six-carbon citric acid

CITRIC ACID CYCLE STEP 2 — What happens to citrate (citric acid)?

It is rearranged and progressively oxidized through enzyme-controlled reactions.

CITRIC ACID CYCLE STEP 3 — What happens to carbon during oxidation?

CO2 is released as carbon compounds are oxidized.

CITRIC ACID CYCLE STEP 4 — How are electron carriers produced?

NAD+ and FAD accept electrons, forming NADH and FADH2.

CITRIC ACID CYCLE STEP 5 — How is ATP made?

Substrate-level phosphorylation produces ATP.

CITRIC ACID CYCLE STEP 6 — Why is oxaloacetate regenerated?

It accepts another acetyl group so the cycle can continue.

CITRIC ACID CYCLE — How many turns occur per glucose?

Two turns, because each glucose yields two acetyl-CoA.

OXIDATIVE PHOSPHORYLATION — What is its purpose?

Use electron-carrier energy and a proton gradient to produce most cellular ATP.

OXIDATIVE PHOSPHORYLATION — Where does it occur?

Inner mitochondrial membrane, including the cristae.

OXIDATIVE PHOSPHORYLATION — What are its reactants?

NADH, FADH2, oxygen, ADP, and Pi.

OXIDATIVE PHOSPHORYLATION — What are its products?

About 32-34 ATP, water, NAD+, and FAD.

OXIDATIVE PHOSPHORYLATION — Why does it matter?

It produces most ATP during aerobic respiration.

OXIDATIVE PHOSPHORYLATION STEP 1 — What do NADH and FADH2 do?

Donate high-energy electrons to the electron transport chain.

OXIDATIVE PHOSPHORYLATION STEP 2 — What happens in the ETC?

Electrons move between membrane protein complexes, releasing energy.

OXIDATIVE PHOSPHORYLATION STEP 3 — What is proton pumping?

ETC complexes use released energy to move H+ from the matrix into the intermembrane space.

OXIDATIVE PHOSPHORYLATION STEP 4 — What happens in the intermembrane space?

H+ accumulates, creating a higher proton concentration and electrochemical gradient.

OXIDATIVE PHOSPHORYLATION STEP 5 — What does oxygen do?

It accepts electrons at the end of the ETC and combines with H+ to form water.

OXIDATIVE PHOSPHORYLATION STEP 6 — What happens during chemiosmosis?

H+ flows down its electrochemical gradient through ATP synthase into the matrix.