Cycle 5

Question 1

Q: Why don’t isolated mitochondria need chloroplasts or the ER?

Answer 1

A: Because mitochondria can perform respiration independently.

Question 2

Q: What happens when mitochondria are added to an oxygen electrode chamber?

Answer 2

A: Initially, no change in oxygen levels—no substrate, so no electron transport.

Question 3

Q: What are the steps in measuring cellular respiration in isolated mitochondria?

Answer 3

1) Grind up Chlamydomonas (Chlamy) cells

2) Purify and wash intact mitochondria

3) Incubate mitochondria in a buffer

4) Seal the chamber and inject substrates to observe respiration changes

5)Measure the slope of the O₂ concentration graph at 2-minute intervals

Question 4

Q: What happens when NADH is added at t = 2 min?

Answer 4

A: Oxygen consumption increases (positive slope) because NADH provides electrons for the electron transport chain (ETC).

Question 5

Q: What happens when ADP and Pi are added at t = 4 min?

Answer 5

A: The slope increases more—electron transport speeds up because ATP synthase opens when ADP + Pi are available.

Question 6

Q: What happens when an uncoupler is added at t = 6 min?

Answer 6

A: The steepest slope, meaning the highest respiration rate. Protons leak back across the membrane without making ATP.

Question 7

Q: What is respiratory control?

Answer 7

A: The regulation of electron transport (oxygen consumption) based on ADP availability—ETC runs faster when ATP can be made.

Question 8

Q: Why does electron transport slow down without ADP and Pi?

Answer 8

A: ATP synthase is a gated channel—it only opens when ADP + Pi are present to allow protons back across.

Question 9

Q: What role does the Calvin Cycle play in autotrophic growth?

Answer 9

A: It fixes CO₂ to make sugars, using ATP from light reactions.

Question 10

Q: Can ATP leave the chloroplast?

Answer 10

A: No, ATP is used inside the chloroplast, but G3P (glyceraldehyde-3-phosphate) is exported.

Question 11

Q: How does G3P link photosynthesis and respiration? (2)

Answer 11

1) Energy source: Converts to pyruvate, enters the citric acid cycle, leading to oxphos (lots of ATP).
2) Carbon source: Some G3P is used for biosynthesis, contributing to the cell’s mass.

Question 12

Q: Where does Chlamy’s mass come from?

Answer 12

A: From CO₂ in the atmosphere—not ATP!

Question 13

Q: Can Chlamy grow in the dark?

Answer 13

A: Not on glucose (no glucose transporter), but yes on acetate, which enters as Acetyl-CoA.

Question 14

Q: What is TAP medium?

Answer 14

A: A growth medium where A = Acetate, allowing heterotrophic growth.

Question 15

Q: What is mixotrophic growth?

Answer 15

A: Using both photosynthesis (autotrophy) and acetate metabolism (heterotrophy) for faster growth.

Question 16

Mixotrophy: Best of both worlds…light + acetate for _____ growth.

Answer 16

maximal

Question 17

💡 Q: How can photosynthesis be measured in an intact Chlamydomonas (Chlamy) cell?

Answer 17

✅ A: Using gas exchange—by measuring CO2 fixation (decrease in CO2 concentration) or O2 production.

Question 18

💡 Q: Where does CO2 fixation occur in photosynthesis?

Answer 18

✅ A: In the Calvin cycle, within the stroma of the chloroplast.

Question 19

💡 Q: Why is measuring photosynthesis in a whole cell challenging?

Answer 19

✅ A: Because mitochondria in the same cell perform respiration, releasing CO2 and consuming O2, which opposes photosynthesis.

Question 20

💡 Q: Where is O2 produced in photosynthesis?

Answer 20

✅ A: In the light-dependent reactions, within the thylakoid membranes.

Question 21

💡 Q: What are the units for measuring the rate of photosynthesis?

Answer 21

✅ A: μmol CO2 consumed per minute.

Question 21

💡 Q: What does a CO2 analyzer detect when photosynthesis is active?

Answer 21

✅ A: A decrease in CO2 concentration in the air above the culture.

Question 22

💡 Q: What does the Light Response Curve show?

Answer 22

✅ A: How the rate of photosynthesis changes with increasing light intensity.

Question 23

💡 Q: What happens at zero light intensity?

Answer 23

✅ A: Only respiration occurs, producing CO2 at a constant rate (e.g., 8 μmol CO2/min), negative on the graph

Question 24

💡 Q: Why does photosynthesis saturate at high light intensities?

Answer 24

✅ A: The Calvin cycle has a maximum turnover rate, limited by factors like Rubisco and CO2 availability.

Question 25

💡 Q: How can the light-saturated rate of photosynthesis be increased?

Answer 25

✅ A: By increasing Rubisco content or CO2 concentration.

Question 25

💡 Q: What is the light compensation point?

Answer 25

✅ A: The light intensity at which the rate of CO2 fixation equals the rate of respiration (net CO2 exchange = 0).

Question 26

💡 Q: Why is the light compensation point important for plant survival?

Answer 26

✅ A: Below this point, the plant loses carbon and cannot grow.

Question 27

💡 Q: What does an enzyme-substrate reaction curve look like?

Answer 27

✅ A: It increases with substrate concentration until it reaches a maximum rate (Vmax).

Question 28

💡 Q: What is Vmax?

Answer 28

✅ A: The maximum rate of an enzyme-catalyzed reaction.

Question 29

💡 Q: What is Km?

Answer 29

✅ A: The substrate concentration needed to reach ½ Vmax, indicating enzyme affinity.

Question 30

💡 Q: If an enzyme has a low Km, what does that mean?

Answer 30

✅ A: It has a high affinity for its substrate (binds effectively at low concentrations).

Question 31

💡 Q: How does temperature affect enzyme kinetics?

Answer 31

✅ A: Low temperatures slow reactions by reducing molecular collisions, while high temperatures can denature enzymes.

Question 32

💡 Q: What is a competitive inhibitor?

Answer 32

✅ A: A molecule that resembles the substrate and competes for the enzyme's active site.

Question 32

💡 Q: Why might a plant increase enzyme concentration in cold environments?

Answer 32

✅ A: To compensate for slower reaction rates due to reduced molecular collisions.

Question 33

💡 Q: How does a competitive inhibitor affect Km and Vmax?

Answer 33

✅ A: Increases Km (decreases affinity) but does not change Vmax.

Question 34

💡 Q: How can the effect of a competitive inhibitor be overcome?

Answer 34

✅ A: By increasing substrate concentration.

Question 35

💡 Q: What is allosteric regulation?

Answer 35

✅ A: When a molecule binds to a site other than the active site, altering enzyme activity.

Question 36

💡 Q: Why regulate metabolism at the enzyme level instead of transcription/translation?

Answer 36

✅ A: It is much faster and allows for quick adjustments in response to cell needs.

Question 37

💡 Q: What does phosphofructokinase (PFK) do?

Answer 37

✅ A: It is a key enzyme in glycolysis, regulating glucose breakdown.

Question 38

💡 Q: What activates PFK?

Answer 38

✅ A: ADP (indicating low energy and need for ATP production).

Question 39

💡 Q: What inhibits PFK?

Answer 39

✅ A: ATP and citrate (signaling sufficient energy levels).

Question 40

💡 Q: What are some key metabolites that regulate metabolism?

Answer 40

✅ A: ATP, ADP, NAD+, NADH, glucose, pyruvate—acting as allosteric activators or inhibitors.