Chapter 8 Study Guide – Bio 101: Energy, Enzymes, and Metabolism

Q1a. What is the difference between a catabolic and an anabolic process?

Background

Topic: Metabolism – Catabolism vs. Anabolism

This question tests your understanding of the two main types of metabolic pathways in cells and how they relate to energy transformation.

Key Terms

• Catabolic process: Pathways that break down molecules into smaller units and release energy.

• Anabolic process: Pathways that build complex molecules from simpler ones, requiring energy input.

Step-by-Step Guidance

1. Recall that metabolism includes all chemical reactions in a cell, divided into catabolic and anabolic pathways.

2. Think about whether the process involves breaking down or building up molecules.

3. Consider the energy aspect: does the process release or require energy?

4. Try to give an example of each type (e.g., cellular respiration for catabolism, protein synthesis for anabolism).

Try solving on your own before revealing the answer!

Final Answer:

Catabolic processes break down complex molecules into simpler ones and release energy (e.g., cellular respiration). Anabolic processes build complex molecules from simpler ones and require energy input (e.g., synthesis of proteins from amino acids).

Q1b. What is the difference between kinetic and potential energy?

Background

Topic: Energy Types in Biology

This question is about distinguishing between two fundamental forms of energy relevant to biological systems.

Key Terms

• Kinetic energy: Energy of motion.

• Potential energy: Stored energy due to position or structure.

Step-by-Step Guidance

1. Define kinetic energy and think of examples in cells (e.g., movement of molecules).

2. Define potential energy and consider where it is stored in biological molecules (e.g., chemical bonds).

3. Compare how each type of energy can be transformed in living organisms.

Try solving on your own before revealing the answer!

Final Answer:

Kinetic energy is the energy of motion (e.g., moving molecules), while potential energy is stored energy due to position or structure (e.g., energy stored in chemical bonds).

Q1c. What is the difference between endergonic and exergonic reactions (also, positive vs. negative $\Delta G$)?

Background

Topic: Free Energy and Chemical Reactions

This question tests your understanding of how energy changes during chemical reactions and how to interpret $\Delta G$ (Gibbs free energy change).

Key Terms and Formulas

• Endergonic reaction: Requires energy input; $\Delta G > 0$.

• Exergonic reaction: Releases energy; $\Delta G < 0$.

• Gibbs free energy change ($\Delta G$): $\Delta G = G_{\text{products}} - G_{\text{reactants}}$

Step-by-Step Guidance

1. Recall what $\Delta G$ represents in a reaction.

2. Determine whether energy is absorbed or released based on the sign of $\Delta G$.

3. Associate endergonic with positive $\Delta G$ and exergonic with negative $\Delta G$.

4. Think of examples for each type (e.g., photosynthesis is endergonic, cellular respiration is exergonic).

Try solving on your own before revealing the answer!

Final Answer:

Endergonic reactions absorb energy and have a positive $\Delta G$; exergonic reactions release energy and have a negative $\Delta G$.

Q1d. What is the difference between oxidized and reduced molecules?

Background

Topic: Redox Reactions in Biology

This question is about understanding electron transfer in metabolic reactions.

Key Terms

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

• "OIL RIG": Oxidation Is Loss, Reduction Is Gain (of electrons).

Step-by-Step Guidance

1. Recall the definitions of oxidation and reduction.

2. Think about what happens to a molecule when it loses or gains electrons.

3. Consider examples from cellular respiration (e.g., NAD+ to NADH).

Try solving on your own before revealing the answer!

Final Answer:

Oxidized molecules have lost electrons, while reduced molecules have gained electrons.

Q2. Can energy be created or destroyed? If not, describe what it does instead when flowing through an organism or ecosystem.

Background

Topic: Laws of Thermodynamics

This question tests your understanding of the first law of thermodynamics and energy flow in biological systems.

Key Terms

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed or transferred.

• Energy flow: Movement of energy through organisms and ecosystems.

Step-by-Step Guidance

1. Recall the first law of thermodynamics and what it means for living systems.

2. Think about how energy enters an ecosystem (e.g., sunlight) and how it is transformed (e.g., photosynthesis, cellular respiration).

3. Consider what happens to energy as it moves through trophic levels and is eventually lost as heat.

Try solving on your own before revealing the answer!

Final Answer:

Energy cannot be created or destroyed; it is transformed from one form to another as it flows through organisms and ecosystems, eventually being lost as heat.

Q3. What are the four ways energy consumed by an organism was said to be used in the PowerPoint?

Background

Topic: Energy Utilization in Organisms

This question is about how organisms allocate the energy they consume.

Key Terms

• Energy allocation: The ways organisms use energy for various biological processes.

Step-by-Step Guidance

1. Recall the main categories of energy use in living organisms (e.g., maintenance, growth, reproduction, activity).

2. Think about examples of each category (e.g., maintaining body temperature, building new tissues, movement, producing offspring).

3. Try to list all four ways as discussed in your lecture or textbook.

Try solving on your own before revealing the answer!

Final Answer:

The four ways energy is used by organisms are: maintenance (basic life functions), growth, reproduction, and activity (movement and other actions).

Q4. What has more free energy, a molecule of ATP or a molecule of glucose? Explain.

Background

Topic: Free Energy in Biological Molecules

This question tests your understanding of energy storage in ATP and glucose.

Key Terms

• ATP (adenosine triphosphate): The cell's main energy currency.

• Glucose: A simple sugar used for energy storage and release.

• Free energy ($G$): The energy available to do work.

Step-by-Step Guidance

1. Recall the structure and function of ATP and glucose.

2. Think about which molecule contains more chemical bonds and thus more stored energy.

3. Consider how many ATP molecules can be produced from one glucose molecule during cellular respiration.

4. Use this information to compare their free energy content.

Try solving on your own before revealing the answer!

Final Answer:

A molecule of glucose has more free energy than a molecule of ATP. This is because glucose contains more chemical bonds and can be used to generate many ATP molecules during cellular respiration.

Q5. If a chemical reaction has $\Delta G = 334$, describe whether it is endergonic or exergonic, and whether energy is absorbed or released.

Background

Topic: Gibbs Free Energy and Reaction Types

This question tests your ability to interpret the sign and value of $\Delta G$ for a chemical reaction.

Key Terms and Formulas

• Endergonic reaction: $\Delta G > 0$ (energy absorbed)

• Exergonic reaction: $\Delta G < 0$ (energy released)

• $\Delta G$ is the change in free energy.

Step-by-Step Guidance

1. Look at the value of $\Delta G$ given (334).

2. Determine if this value is positive or negative.

3. Recall what a positive $\Delta G$ means for the reaction (endergonic or exergonic).

4. Decide whether energy is absorbed or released based on the reaction type.

Try solving on your own before revealing the answer!

Final Answer:

Since $\Delta G = 334$ is positive, the reaction is endergonic and energy is absorbed.

Q6. What is the activation energy ($E_a$) of a chemical reaction, and how does an enzyme affect $E_a$?

Background

Topic: Enzyme Catalysis

This question is about understanding how enzymes speed up chemical reactions by affecting activation energy.

Key Terms and Formulas

• Activation energy ($E_a$): The minimum energy required to start a chemical reaction.

• Enzyme: A biological catalyst that speeds up reactions.

Step-by-Step Guidance

1. Define activation energy and its role in chemical reactions.

2. Recall what enzymes do to the activation energy barrier.

3. Think about how lowering $E_a$ affects the rate of reaction.

4. Consider drawing or visualizing an energy diagram with and without an enzyme.

Try solving on your own before revealing the answer!

Final Answer:

The activation energy ($E_a$) is the energy needed to start a reaction. Enzymes lower the activation energy, allowing reactions to proceed faster at lower energy input.

Q7. What is the name of where the substrate binds to an enzyme?

Background

Topic: Enzyme Structure and Function

This question is about enzyme-substrate interactions.

Key Terms

• Substrate: The reactant that an enzyme acts on.

• Active site: The region on the enzyme where the substrate binds.

Step-by-Step Guidance

1. Recall the structure of an enzyme and where the substrate fits.

2. Think about the specificity of this region and its role in catalysis.

3. Remember the term used to describe this binding region.

Try solving on your own before revealing the answer!

Final Answer:

The substrate binds to the enzyme's active site.

Q8. After a chemical reaction, what happens to an enzyme? Is it used in the reaction?

Background

Topic: Enzyme Function and Reusability

This question tests your understanding of how enzymes function during and after catalysis.

Key Terms

• Catalyst: A substance that speeds up a reaction without being consumed.

• Enzyme reusability: Enzymes are not used up in reactions.

Step-by-Step Guidance

1. Recall the definition of a catalyst and how enzymes fit this definition.

2. Think about what happens to the enzyme's structure after the reaction.

3. Consider whether the enzyme can be used again for another reaction cycle.

Try solving on your own before revealing the answer!

Final Answer:

After a reaction, the enzyme remains unchanged and can be reused; it is not consumed in the reaction.

Q9. What environmental variables affect enzyme activity?

Background

Topic: Enzyme Regulation

This question is about the factors that influence how well enzymes function.

Key Terms

• Enzyme activity: The rate at which an enzyme catalyzes a reaction.

• Environmental variables: Temperature, pH, substrate concentration, etc.

Step-by-Step Guidance

1. List the main environmental factors that can affect enzyme activity.

2. Think about how changes in temperature or pH can alter enzyme structure and function.

3. Consider the effect of substrate concentration on reaction rate.

4. Recall any other factors discussed in class or your textbook.

Try solving on your own before revealing the answer!

Final Answer:

Enzyme activity is affected by temperature, pH, substrate concentration, and the presence of inhibitors or activators.

Q10. What are cofactors and enzyme inhibitors, and how do they affect enzyme activity?

Background

Topic: Enzyme Regulation and Function

This question is about molecules that influence enzyme activity, either by helping or hindering their function.

Key Terms

• Cofactor: A non-protein molecule or ion required for enzyme activity.

• Enzyme inhibitor: A molecule that decreases or stops enzyme activity.

Step-by-Step Guidance

1. Define what a cofactor is and give examples (e.g., metal ions, vitamins).

2. Explain how cofactors assist enzymes in catalysis.

3. Define enzyme inhibitors and distinguish between competitive and noncompetitive inhibition.

4. Describe how inhibitors affect enzyme activity.

Try solving on your own before revealing the answer!

Final Answer:

Cofactors are non-protein helpers (like metal ions or vitamins) required for enzyme activity. Enzyme inhibitors are molecules that decrease or block enzyme activity, either by competing with the substrate or by changing the enzyme's shape.