Glycolysis · Krebs Cycle · Electron Transport Chain · Post-Harvest Physiology
📋 About this quiz
12 questions covering Units 2.2.1–2.2.4
Mix of multiple choice, true/false, and fill-in-the-blank
Instant feedback after each question
Unlimited attempts for practice
Estimated time: 20–25 minutes
QUESTION 1
Where in the plant cell does glycolysis occur?
✅ Correct! Glycolysis occurs in the cytoplasm. It's the first stage of respiration and does not require oxygen. The Krebs cycle occurs in the mitochondrial matrix, and the electron transport chain is in the inner mitochondrial membrane.
QUESTION 2
What is the net ATP yield from one molecule of glucose in glycolysis?
✅ Correct! Glycolysis has an energy investment phase (uses 2 ATP) and an energy payoff phase (produces 4 ATP), for a net gain of 2 ATP per glucose. It also produces 2 NADH.
QUESTION 3
In which part of the mitochondrion does the Krebs cycle occur?
✅ Correct! The Krebs cycle (citric acid cycle) occurs in the mitochondrial matrix—the fluid-filled space inside the inner membrane. The electron transport chain is in the inner membrane itself.
QUESTION 4
For each acetyl-CoA that enters the Krebs cycle, how many NADH are produced?
✅ Correct! Per acetyl-CoA, the Krebs cycle produces 3 NADH (steps 3, 4, and 8), 1 FADH₂ (step 6), and 1 ATP (step 5). Since one glucose produces 2 acetyl-CoA, these numbers double.
QUESTION 5
What is the final electron acceptor in the electron transport chain?
✅ Correct! Oxygen is the final electron acceptor. At Complex IV, electrons are transferred to oxygen, which combines with protons to form water. Without oxygen, the electron transport chain backs up and ATP production stops.
QUESTION 6
The enzyme that uses the proton gradient to produce ATP is called:
✅ Correct! ATP synthase is a rotary motor enzyme embedded in the inner mitochondrial membrane. Protons flow through it from the intermembrane space back to the matrix, driving the phosphorylation of ADP to ATP.
QUESTION 7
True or False: The alternative oxidase pathway in plants produces ATP but generates heat.
✅ Correct! It's False. The alternative oxidase bypasses complexes III and IV, transferring electrons directly to oxygen. This pathway does NOT pump protons, so it produces NO ATP—only heat. It's used for thermogenesis (e.g., in skunk cabbage) and to reduce ROS formation under stress.
QUESTION 8
Which of the following is a climacteric fruit?
✅ Correct! Banana is a climacteric fruit—it shows a dramatic rise in respiration and ethylene production during ripening and can be harvested green and ripened off the plant. Grapes, strawberries, and oranges are non-climacteric.
QUESTION 9
The Q₁₀ temperature coefficient for respiration is typically 2-3. This means:
✅ Correct! Q₁₀ is the factor by which respiration increases for a 10°C temperature rise. A Q₁₀ of 2-3 means that if you increase temperature by 10°C, respiration rate increases 2-3 times. This is why cold storage is so effective!
QUESTION 10
In controlled atmosphere (CA) storage, what gas is typically reduced to 1-3% to slow respiration?
✅ Correct! In CA storage, oxygen is reduced from normal 21% to 1-3%, which slows respiration by limiting the final electron acceptor in the ETC. Carbon dioxide is often increased (1-5%) as well, which further inhibits enzymes.
QUESTION 11
If a fruit in storage has a respiratory quotient (RQ) of 1.2, what substrate is it primarily metabolizing?
✅ Correct! RQ = CO₂ produced / O₂ consumed. Carbohydrates have RQ ≈ 1.0; organic acids have RQ > 1.0 (up to 1.5); fats have RQ < 1.0 (0.7-0.8). An RQ of 1.2 suggests the fruit is metabolizing organic acids, often a sign of senescence or stress.
QUESTION 12
What low-cost technology uses evaporative cooling to reduce storage temperatures in dry regions?
✅ Correct! A zero-energy cooler (or evaporative cooler) uses water evaporation through charcoal or other porous material to cool the interior. It can reduce temperatures by 10-15°C in dry climates, providing low-cost storage for smallholders in Ethiopia and other developing regions.
📊 Section 2.2 Complete!
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Great job! Review the explanations for any questions you missed.
📌 Section 2.2 Complete!
You have completed all units in Section 2.2: Respiration. You should now be able to:
Explain the process and energy yield of glycolysis
Describe the Krebs cycle and its products
Understand how the electron transport chain produces ATP via chemiosmosis
Apply respiration principles to post-harvest storage of fruits and vegetables
Classify fruits by respiration patterns and recommend storage conditions
👉 Next: Module III explores the Biochemical Basis of Productivity & Quality.
Plant Biochemistry for Horticulture · HORT 202 · Dilla University · Last updated March 2026