③ Metabolism (short answers)

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Questions and Answers

Explain how the induced fit model differs from the lock and key model of enzyme-substrate interaction, and why is the induced fit model considered a more accurate representation?

The lock and key model proposes a rigid active site, while the induced fit model suggests the active site changes shape to better accommodate the substrate. Induced fit is more accurate as it accounts for the dynamic nature of enzyme-substrate interactions.

Describe the effect of increasing substrate concentration on the rate of an enzyme-catalyzed reaction, assuming the enzyme concentration remains constant. What eventually happens to the reaction rate, and why?

Initially, increasing substrate concentration increases the reaction rate. Eventually, the reaction rate plateaus because all active sites are occupied and the enzyme is saturated.

Explain how competitive inhibitors affect enzyme activity, and contrast this with the mechanism of action of non-competitive inhibitors.

Competitive inhibitors bind to the active site, preventing substrate binding. Non-competitive inhibitors bind to a different site, altering enzyme shape and reducing activity.

Outline the main difference between aerobic and anaerobic respiration, and explain why aerobic respiration yields a significantly greater amount of ATP.

Aerobic respiration uses oxygen as the final electron acceptor, while anaerobic does not. Aerobic respiration produces more ATP as oxygen facilitates a more efficient electron transport chain. Signup and view all the answers

Describe the role of the electron transport chain (ETC) in cellular respiration and explain how it contributes to the formation of a proton gradient. What is the significance of this gradient?

The ETC transfers electrons and pumps protons across the inner mitochondrial membrane, creating a proton gradient. This gradient drives ATP synthase to produce ATP. Signup and view all the answers

Explain the purpose of fermentation in the absence of oxygen, and provide two examples of different fermentation products along with the organisms that produce them.

Fermentation regenerates NAD+ for glycolysis when oxygen is absent. Examples: lactic acid by animals and some bacteria, ethanol by yeast. Signup and view all the answers

In photosynthesis, what is the role of chlorophyll and other accessory pigments? Explain how they capture light energy and what happens to this energy subsequently.

Chlorophyll and accessory pigments absorb light energy. This energy excites electrons, which are then passed along an electron transport chain. Signup and view all the answers

Describe the key differences between the light-dependent and light-independent (Calvin cycle) reactions of photosynthesis. Where do these reactions occur within the chloroplast?

Light-dependent reactions convert light energy to chemical energy (ATP and NADPH) in the thylakoid membrane. Light-independent reactions use ATP and NADPH to fix CO2 into glucose in the stroma. Signup and view all the answers

Explain the process of carbon fixation in the Calvin cycle and describe the role of the enzyme RuBisCO in this process. What molecule is initially formed after carbon fixation?

Carbon fixation is the incorporation of CO2 into an organic molecule. RuBisCO catalyzes the reaction between CO2 and RuBP. The initial product is a 6-carbon molecule that quickly breaks down into two molecules of 3-PGA. Signup and view all the answers

How does temperature affect enzyme activity? Explain the terms 'optimum temperature' and 'denaturation' in the context of enzyme function.

Enzyme activity increases with temperature up to a point (optimum temperature). Beyond that, the enzyme denatures (loses its shape) and activity decreases. Signup and view all the answers

Explain how pH affects enzyme activity, referencing the impact of pH on the enzyme's structure and active site.

Extreme pH levels disrupt ionic and hydrogen bonds, altering the enzyme's shape and active site, thus affecting substrate binding and catalytic activity. Signup and view all the answers

Describe how feedback inhibition regulates metabolic pathways. Use a specific example to illustrate how this process helps maintain homeostasis.

In feedback inhibition, the end product of a metabolic pathway inhibits an earlier enzyme in the pathway, preventing overproduction. Example: High levels of ATP inhibit enzymes in glycolysis. Signup and view all the answers

Explain the role of coenzymes in enzyme-catalyzed reactions, providing specific examples of coenzymes involved in cellular respiration or photosynthesis.

Coenzymes assist enzymes by carrying electrons or chemical groups. Examples include NAD+ and FAD in respiration, and NADP+ in photosynthesis. Signup and view all the answers

Distinguish between catabolic and anabolic pathways, and provide an example of each in the context of cellular metabolism. How are these pathways linked?

Catabolic pathways break down complex molecules, releasing energy (e.g., cellular respiration). Anabolic pathways build complex molecules, consuming energy (e.g., protein synthesis). They are linked because catabolism provides the energy for anabolism. Signup and view all the answers

Describe the chemiosmotic process in either respiration or photosynthesis, explaining how it couples electron transport to ATP synthesis. What is the specific role of ATP synthase?

Chemiosmosis uses the proton gradient generated by electron transport to drive ATP synthesis. ATP synthase is the enzyme that uses the proton gradient to phosphorylate ADP to ATP. Signup and view all the answers

Explain the significance of the light-independent reactions (Calvin cycle) in photosynthesis, emphasizing the role of carbon dioxide and the regeneration of RuBP.

The Calvin cycle fixes CO2 into glucose, providing the plant with energy. The regeneration of RuBP allows the cycle to continue accepting CO2. Signup and view all the answers

Compare and contrast substrate-level phosphorylation and oxidative phosphorylation in ATP production. In which metabolic pathways does each occur?

Substrate-level phosphorylation directly adds a phosphate to ADP, occurring in glycolysis and the Krebs cycle. Oxidative phosphorylation uses a proton gradient to drive ATP synthase, occurring in the electron transport chain. Signup and view all the answers

Outline the main steps of glycolysis, indicating the inputs and outputs of energy (ATP and NADH) during this process. Where does glycolysis occur within the cell?

Glycolysis breaks down glucose into pyruvate, producing a net gain of 2 ATP and 2 NADH. It occurs in the cytoplasm. Signup and view all the answers

Describe the Krebs cycle (citric acid cycle), explaining its role in oxidizing organic molecules and generating ATP, NADH, and FADH2. Where does this cycle take place in eukaryotic cells?

The Krebs cycle oxidizes acetyl-CoA, producing ATP, NADH, and FADH2. It takes place in the mitochondrial matrix. Signup and view all the answers

Explain how the products of photosynthesis (glucose and oxygen) are utilized in cellular respiration, and conversely, how the products of cellular respiration (carbon dioxide and water) are utilized in photosynthesis. How does this demonstrate interdependence in ecosystems?

Glucose from photosynthesis is used as fuel for respiration, and oxygen is the final electron acceptor. CO2 and water from respiration are used as reactants in photosynthesis. This demonstrates the cycling of matter and energy flow, highlighting interdependence in ecosystems. Signup and view all the answers

Flashcards

Enzymes

Biological catalysts that speed up chemical reactions by lowering activation energy.

Respiration

A catabolic process that breaks down glucose to produce ATP, using oxygen (aerobic) or without (anaerobic).