Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

3. Energy & Cell Processes

Krebs Cycle

Anatomy & Physiology

3. Energy & Cell Processes

Krebs Cycle

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3:10 minutes

Problem 15

Textbook Question

In the citric acid cycle, an enzyme oxidizes malate to oxaloacetate, with the production of NADH and the release of H+. You are studying this reaction using a suspension of bean cell mitochondria and a blue dye that loses its color as it takes up H+. You set up reaction mixtures with mitochondria, dye, and three different concentrations of malate (0.1 mg/L, 0.2 mg/L, and 0.3 mg/L). Which of the following graphs represents the results you would expect, and why?

Verified step by step guidance

Step 1: Understand the reaction: Malate is oxidized to oxaloacetate, producing NADH and releasing H+. The blue dye loses its color as it takes up H+.

Step 2: Identify the relationship between malate concentration and the rate of reaction: Higher malate concentration should result in a faster reaction rate, leading to more H+ release and faster color loss of the dye.

Step 3: Analyze the graphs: Look for the graph where higher malate concentrations (0.3 mg/L) result in a faster decrease in color intensity over time.

Step 4: Compare the graphs: Graph (a) shows increasing color intensity, which is incorrect. Graph (b) shows decreasing color intensity, but the lines converge, which is not expected. Graph (c) shows decreasing color intensity with the steepest slope for the highest malate concentration (0.3 mg/L), which matches our expectations.

Step 5: Conclude that graph (c) represents the expected results because it shows the fastest color loss for the highest malate concentration, indicating the highest rate of H+ release and dye decolorization.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Citric Acid Cycle

The citric acid cycle, also known as the Krebs cycle, is a series of enzymatic reactions that occur in the mitochondria, where acetyl-CoA is oxidized to produce energy. Key products include NADH, FADH2, and ATP, which are essential for cellular respiration. Understanding this cycle is crucial for analyzing how substrates like malate are metabolized and how energy is generated in cells.

Enzyme Activity and Substrate Concentration

Enzyme activity is influenced by substrate concentration, typically following Michaelis-Menten kinetics. As substrate concentration increases, the rate of reaction increases until it reaches a maximum velocity (Vmax) when all enzyme active sites are saturated. This concept is vital for predicting how varying concentrations of malate will affect the rate of the reaction and the production of NADH in the experiment.

Colorimetric Analysis

Colorimetric analysis involves measuring the intensity of color change in a solution, which can indicate the concentration of a substance. In this experiment, a blue dye that loses color as it takes up H+ is used to monitor the reaction's progress. Understanding how color intensity correlates with the reaction rate allows for the interpretation of the results and the expected graph shapes based on malate concentrations.

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