BackBIO 121 Study Guide: Membranes, Enzymes, Cellular Respiration, and Photosynthesis
Study Guide - Smart Notes
Tailored notes based on your materials, expanded with key definitions, examples, and context.
Q25. Suppose a thistle tube containing a 10% sugar solution is covered at one end by a differentially permeable membrane and is placed in a beaker containing a 5% sugar solution. What will happen to the water?
Background
Topic: Osmosis and Membrane Transport
This question tests your understanding of how water moves across a selectively permeable membrane in response to differences in solute concentration (osmosis).
Key Terms and Concepts:
Osmosis: The diffusion of water across a selectively permeable membrane from an area of lower solute concentration to higher solute concentration.
Differentially permeable membrane: Allows water to pass but not solute molecules (like sugar).
Solute concentration: The amount of dissolved substance (sugar) in a solution.
Step-by-Step Guidance
Identify which solution (inside or outside the thistle tube) has a higher solute concentration. (10% inside, 5% outside)
Recall that water moves from areas of lower solute concentration to higher solute concentration through osmosis.
Consider what happens to water movement when the membrane only allows water, not sugar, to pass.
Think about whether more water will enter or leave the thistle tube, or if there will be no net movement.
Try solving on your own before revealing the answer!
Final Answer: d) More water will enter the thistle tube than leave the thistle tube.
Water moves into the tube because the inside has a higher solute concentration, so osmosis drives water from the 5% solution into the 10% solution.
Q1. Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as _____ is to _____.
Background
Topic: Metabolism (Catabolism vs. Anabolism)
This question tests your understanding of the relationship between catabolic and anabolic pathways and their energy profiles.
Key Terms and Concepts:
Catabolism: Metabolic pathways that break down molecules, releasing energy (often exergonic).
Anabolism: Metabolic pathways that build complex molecules, requiring energy (often endergonic).
Exergonic: Reactions that release energy.
Endergonic: Reactions that require energy input.
Step-by-Step Guidance
Recall the definitions of catabolism and anabolism.
Match catabolism with the type of reaction (exergonic or endergonic) it represents.
Match anabolism with the appropriate reaction type.
Look for the answer choice that pairs these correctly.
Try solving on your own before revealing the answer!
Final Answer: B) exergonic; endergonic
Catabolism releases energy (exergonic), while anabolism requires energy input (endergonic).
Q2. Most cells cannot harness heat to perform work because
Background
Topic: Thermodynamics in Biology
This question tests your understanding of why cells do not use heat energy to do biological work.
Key Terms and Concepts:
Heat energy: Random movement of molecules; not easily harnessed for work in cells.
Uniform temperature: When temperature is the same throughout, heat cannot be used to do work.
Step-by-Step Guidance
Recall the second law of thermodynamics and how energy is transferred in cells.
Consider why heat energy is not useful for cellular work.
Look for the answer that explains the limitation due to temperature uniformity.
Try solving on your own before revealing the answer!
Final Answer: C) temperature is usually uniform throughout a cell.
Without a temperature gradient, cells cannot use heat to do work.
Q3. According to the first law of thermodynamics,
Background
Topic: Laws of Thermodynamics
This question tests your knowledge of the first law of thermodynamics as it applies to biological systems.
Key Terms and Concepts:
First law of thermodynamics: Energy cannot be created or destroyed, only transformed.
Energy conservation: The total energy in a closed system remains constant.
Step-by-Step Guidance
Recall the statement of the first law of thermodynamics.
Eliminate answer choices that mention energy creation or destruction.
Identify the answer that correctly describes energy conservation.
Try solving on your own before revealing the answer!
Final Answer: B) energy is conserved in all processes.
The first law states that energy is neither created nor destroyed.
Q4. Which of the following metabolic processes can occur without a net influx of energy from some other process?
Background
Topic: Metabolic Pathways and Energy
This question tests your ability to distinguish between spontaneous (exergonic) and non-spontaneous (endergonic) metabolic reactions.
Key Terms and Concepts:
Exergonic reaction: Proceeds spontaneously, releases energy.
Endergonic reaction: Requires energy input.
Cellular respiration: Breakdown of glucose to CO2 and H2O is exergonic.
Step-by-Step Guidance
Identify which reactions are exergonic (release energy) and which are endergonic (require energy input).
Recall that ATP synthesis and macromolecule formation are typically endergonic.
Look for the reaction that is catabolic and releases energy.
Try solving on your own before revealing the answer!
Final Answer: B) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
This is the overall equation for cellular respiration, an exergonic process.
Q5. If an enzyme has been inhibited noncompetitively,
Background
Topic: Enzyme Inhibition
This question tests your understanding of noncompetitive inhibition and how it differs from competitive inhibition.
Key Terms and Concepts:
Noncompetitive inhibitor: Binds to an enzyme at a site other than the active site, changing the enzyme's shape.
Substrate: The molecule upon which an enzyme acts.
ΔG (Gibbs free energy): Change in free energy during a reaction.
Step-by-Step Guidance
Recall where noncompetitive inhibitors bind on the enzyme.
Consider whether the inhibitor must resemble the substrate.
Think about whether increasing substrate concentration affects noncompetitive inhibition.
Identify the answer that best describes noncompetitive inhibition.
Try solving on your own before revealing the answer!
Final Answer: E) the inhibitor molecule may be chemically unrelated to the substrate.
Noncompetitive inhibitors bind elsewhere and do not need to resemble the substrate.
