Week 4 Review

Question 1

What are the major reactants and products of cellular respiration and photosynthesis? What are the major phases of photosynthesis? Which requires light? Which involve electron transport chains (ETCs)? Which phases involve cyclic photophosphorylation?

Answer 1

In cellular respiration, glucose and oxygen produce ATP, CO2, and water.
In photosynthesis, carbon dioxide, water, and light energy produce glucose, water, and oxygen.
- Both of these processes involve electron transport chains, however, only photosynthesis requires light and involves cyclic photophosphorylation

Major Phases of photosynthesis:
Light-dependent reaction (light energy is converted into ATP and NADPH)
Carbon Fixation, which happens in light-independent reaction (ATP and NADPH are used to reduce CO2 to sugar)

Question 2

What is the primary electron acceptor in photosynthesis?

Answer 2

In Cyclic Photophosphorylation (PS 1), electrons are cycled back to chlorophyll

In Non-cyclic photophosphorylation (PS 2), electrons are given to NADP to make NADPH

Question 3

What is the major purpose of each photosystem and Calvin-Benson cycle?

Answer 3

Cyclic Photophosphorylation (PS 1) = make ATP
Non-cyclic photophosphorylation (PS 2) = make NADPH
- To drive the Calvin-Benson Cycle

Calvin-Benson Cycle: uses ATP and NADPH made in light-dependent reaction to break CO2 into glucose
- 3 CO2 -> 1 G3P (the intermediate molecule in glycolysis), which is biosynthesized into carbohydrates (glucose)

Question 4

Describe the biosynthesis of lipids, purines/pyrimidines, and amino acids. How do they relate to phases of catabolism?

Answer 4

Glycolysis is a catabolic process, that breaks glucose into G3P and then into pyruvate

Lipids:
- G3P is used to make glycerol (monomer of lipid)
- Acetyl Co-A is used to make fatty acid (polymer of lipid)
- Glycerol and fatty acids make simple lipids

Nucleotides:
- An intermediate molecule between glucose and G3P is used to make pentose (5C)
- Pentose is used to make purines and pyrimidines
- Somewhere in Kreb’s Cycle, a molecule can be used to make aspartic acid, which can be broken down into purines and pyrimidines

Amino Acids:
- The alternative of glycolysis and organic acids from the Krebs cycle can be put together to make amino acids
- Amination: adding an amine group to pyruvic acid or organic acid of Krebs cycle
- Transamination: new amino acids made with amine group from old amino acids