Biology Chapter 6: Metabolism

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Questions and Answers

Which of the following best defines metabolism?

The sum total of all chemical reactions within an organism (correct)

The breakdown of complex molecules into simpler compounds

The absorption of nutrients from food

The process of building molecules using energy

Anabolic reactions release energy by breaking down complex molecules.

False

What type of reaction is photosynthesis?

anabolic

During cellular respiration, glucose is broken down into carbon dioxide and water, releasing energy in the form of _____ .

ATP Signup and view all the answers

Which reactions are considered 'uphill' and require energy input?

Anabolic reactions Signup and view all the answers

What symbol represents the change in free energy?

ΔG Signup and view all the answers

Match the following types of reactions with their characteristics:

Anabolic = Consume energy to build molecules Catabolic = Release energy by breaking down molecules Photosynthesis = An example of an anabolic reaction Cellular respiration = An example of a catabolic reaction Signup and view all the answers

Both anabolic and catabolic reactions require enzymes to catalyze reactions.

True Signup and view all the answers

Which process is exergonic?

Cellular respiration Signup and view all the answers

Photosynthesis is an exergonic reaction.

False Signup and view all the answers

What is the role of ATP in cellular work?

ATP provides energy for cellular processes by coupling exergonic reactions to endergonic reactions. Signup and view all the answers

A catalyst speeds up a chemical reaction by lowering its __________.

activation energy Signup and view all the answers

Match the following terms with their definitions:

Enzyme = A biological catalyst that speeds up reactions Substrate = The specific reactant that binds to an enzyme Active site = The region on the enzyme where the substrate binds Products = The molecules formed after the reaction Signup and view all the answers

Which factor does NOT affect the rate of enzyme action?

Molecular weight of water Signup and view all the answers

Competitive inhibitors bind to sites other than the active site.

False Signup and view all the answers

What is energy coupling?

Energy coupling is the process of using the energy released from an exergonic reaction to drive an endergonic reaction. Signup and view all the answers

In enzymatic reactions, __________ can lead to denaturation.

extremes of pH or very high temperatures Signup and view all the answers

What is an allosteric activator?

A molecule that stabilizes the enzyme in its active form Signup and view all the answers

Enzymes change the value of ΔG in a reaction.

False Signup and view all the answers

What type of inhibition does an end product serve in metabolic pathways?

Feedback noncompetitive inhibition Signup and view all the answers

Each enzyme has an optimal __________ range for activity.

pH Signup and view all the answers

Match the following inhibitors with their characteristics:

Competitive inhibitor = Binds to the active site Noncompetitive inhibitor = Binds to a different site, changing enzyme shape Allosteric inhibitor = Stabilizes the inactive form of the enzyme Allosteric activator = Increases enzyme activity by stabilizing active form Signup and view all the answers

Study Notes

Concept 6.1: Metabolism

Metabolism: The sum of all chemical reactions in an organism; includes catabolism (breaking down molecules to release energy) and anabolism (building molecules, consuming energy).
Catabolic Reactions: Release energy by breaking down complex molecules into simpler ones (e.g., glucose breakdown in cellular respiration).
Anabolic Reactions: Consume energy to build complex molecules from simpler ones (e.g., protein synthesis).
Photosynthesis: Anabolic reaction; uses light energy to synthesize glucose from CO₂ and H₂O.
Cellular Respiration: Catabolic reaction; breaks down glucose to release energy in the form of ATP.
Enzymes: Essential in both catabolic and anabolic reactions; lower activation energy to increase reaction rates.

Concept 6.2: Free Energy and Spontaneity

Free Energy (G): The portion of a system's energy available to do work at constant temperature and pressure.
Change in Free Energy (ΔG): Determines reaction spontaneity; negative ΔG indicates a spontaneous reaction (releasing energy). Positive ΔG indicates a non-spontaneous reaction (requiring energy input).
Cellular Respiration: Exergonic (releases energy, negative ΔG).
Photosynthesis: Endergonic (requires energy input, positive ΔG).

Concept 6.3: ATP and Energy Coupling

ATP (Adenosine Triphosphate): Composed of adenine (nitrogenous base), ribose (five-carbon sugar), and three phosphate groups. The bond between the second and third phosphate groups is often the one broken during hydrolysis.
Energy Coupling: The use of energy released from an exergonic reaction (e.g., ATP hydrolysis) to drive an endergonic reaction (e.g., active transport).

Concept 6.4: Enzymes and Reaction Rates

Catalyst: Substance that speeds up a reaction without being consumed or permanently changed.
Activation Energy (EA): Minimum energy needed to initiate a reaction.
Enzymes: Biological catalysts that lower activation energy, speeding up reactions.
Substrate: The reactant that binds to an enzyme.
Active Site: Region on the enzyme where the substrate binds.
Product: Molecules formed by the reaction.
Enzyme Specificity: Dependent on the three-dimensional shape of the active site precisely fitting the substrate.
Factors Affecting Enzyme Activity:
- Substrate Concentration: Increasing substrate increases reaction rate until the enzyme is saturated.
- pH: Each enzyme has an ideal pH range for optimal activity.
- Temperature: Enzymatic activity increases with temperature until an optimum point is reached; beyond that, high temperatures cause denaturation.
Denaturation: Breakdown of protein structure (hydrogen bonds and ionic interactions) due to extreme conditions affecting enzyme function.
Competitive Inhibitors: Bind to the active site, preventing substrate binding.
Noncompetitive Inhibitors: Bind to a site other than the active site. This changes the enzyme's shape, affecting its activity.

Concept 6.5: Enzyme Regulation

Allosteric Regulation: Molecules bind to regulatory sites altering enzyme activity.
Allosteric Activator: Stabilizes the active form of an enzyme, increasing its activity.
Allosteric Inhibitor: Stabilizes the inactive form of an enzyme, decreasing its activity.
Feedback Inhibition: Method of metabolic control; the end product of a pathway inhibits an enzyme in the pathway to prevent overproduction.

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Description

Explore the key concepts of metabolism through this quiz covering both catabolic and anabolic reactions. Test your knowledge on topics such as photosynthesis, cellular respiration, and the role of enzymes. Understand the principles of free energy and spontaneity as they relate to biological processes.