Biochemistry: Metabolism and Enzymes
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Questions and Answers

What is the correct definition of anabolism?

  • The process of energy release during cellular respiration
  • Transport of nutrients across cell membranes
  • Synthesis of larger molecules from smaller ones (correct)
  • Degradation of larger molecules into smaller ones

Which statement accurately describes enzyme activity?

  • Enzymes can lower the activation energy required for a reaction. (correct)
  • Enzymes are permanently changed after the reactions.
  • Enzymes become integrated into the reaction products.
  • Enzymes are only effective at high temperature ranges.

Which of the following best describes the role of ATP in cells?

  • ATP is mainly involved in storing genetic information.
  • ATP acts as a structural component of cell membranes.
  • ATP serves as the energy currency of the cell. (correct)
  • ATP is primarily used for synthesizing proteins.

What is the primary effect of temperature on enzyme activity?

<p>Enzymes function optimally at a specific temperature range. (A)</p> Signup and view all the answers

In biological oxidation-reduction reactions, what occurs during oxidation?

<p>A substance loses electrons. (A)</p> Signup and view all the answers

How do enzymes interact with their substrates?

<p>Enzymes bind substrates at an active site to facilitate reactions. (B)</p> Signup and view all the answers

Which source of energy is associated with molecular motion?

<p>Thermal (heat) energy (D)</p> Signup and view all the answers

Which of the following statements is NOT true about enzymes?

<p>Enzymes permanently change their structure after reactions. (D)</p> Signup and view all the answers

What is the primary purpose of glycolysis in cellular respiration?

<p>To produce ATP and pyruvate (D)</p> Signup and view all the answers

Where does the Krebs cycle occur within the cell?

<p>Mitochondrial matrix (A)</p> Signup and view all the answers

After glycolysis, what is the next molecule produced that enters the Krebs cycle?

<p>Acetyl-CoA (D)</p> Signup and view all the answers

How many ATP molecules are produced during the Krebs cycle for each molecule of acetyl-CoA that enters?

<p>2 (D)</p> Signup and view all the answers

What is the main function of the electron transport chain in aerobic respiration?

<p>To harness energy from electrons to produce ATP (D)</p> Signup and view all the answers

What is produced during lactic acid fermentation?

<p>Lactate (C)</p> Signup and view all the answers

What is the net gain of ATP from glycolysis?

<p>2 (B)</p> Signup and view all the answers

Which molecule can serve as an alternative electron acceptor during anaerobic respiration?

<p>Nitrate (D)</p> Signup and view all the answers

What is a key difference between aerobic and anaerobic respiration in terms of ATP production?

<p>Aerobic respiration produces significantly more ATP (C)</p> Signup and view all the answers

What is the final electron acceptor in aerobic respiration?

<p>O₂ (C)</p> Signup and view all the answers

During alcoholic fermentation, what are the end products?

<p>Ethanol and CO₂ (C)</p> Signup and view all the answers

What is generated as a waste product during the Krebs cycle?

<p>CO₂ (C)</p> Signup and view all the answers

In which phase of glycolysis is glucose phosphorylated to form fructose-1,6-bisphosphate?

<p>Energy Investment Phase (C)</p> Signup and view all the answers

Why is fermentation important for cells in anaerobic conditions?

<p>It allows glycolysis to continue by regenerating NAD⁺ (C)</p> Signup and view all the answers

What defines the process of catabolism in metabolism?

<p>Larger molecules are broken down into smaller ones, releasing energy. (C)</p> Signup and view all the answers

What role do cofactors play in enzyme function?

<p>They can include metal ions or organic molecules that assist enzymatic reactions. (B)</p> Signup and view all the answers

How do enzymes achieve lower activation energy in chemical reactions?

<p>By positioning substrates in a way that promotes interaction. (D)</p> Signup and view all the answers

What is a characteristic feature of ATP that allows it to serve as the energy currency of the cell?

<p>Energy is stored in the bond between its second and third phosphate groups. (C)</p> Signup and view all the answers

Which of the following best describes the relationship between oxidation and reduction reactions?

<p>Oxidation involves losing electrons, while reduction involves gaining electrons. (B)</p> Signup and view all the answers

Which of the following statements accurately describes the characteristics of enzymes?

<p>Enzymes lower activation energy and can be reused after reactions. (D)</p> Signup and view all the answers

Which form of energy is directly associated with the movement of electrons?

<p>Electrical energy (B)</p> Signup and view all the answers

What is one of the primary functions of enzymes in biological systems?

<p>To act as catalysts for biochemical reactions. (A)</p> Signup and view all the answers

What is the primary purpose of the Krebs cycle during cellular respiration?

<p>To generate high-energy electron carriers (B)</p> Signup and view all the answers

During glycolysis, which molecule is broken down into pyruvate?

<p>Glucose (D)</p> Signup and view all the answers

What are the end products of lactic acid fermentation?

<p>Lactate and NAD⁺ (A)</p> Signup and view all the answers

Which step in the Krebs cycle produces ATP or GTP?

<p>Substrate-level phosphorylation (C)</p> Signup and view all the answers

What occurs in the mitochondrial matrix during cellular respiration?

<p>Krebs cycle and pyruvate decarboxylation (A)</p> Signup and view all the answers

What role do NADH and FADH₂ play in the electron transport chain?

<p>They donate electrons to drive ATP synthesis (C)</p> Signup and view all the answers

In anaerobic respiration, what is the primary purpose of fermentation?

<p>To regenerate NAD⁺ for continued glycolysis (C)</p> Signup and view all the answers

How many molecules of ATP are typically produced from one molecule of glucose through aerobic respiration?

<p>36–38 (C)</p> Signup and view all the answers

What substance is produced as a waste product during the Krebs cycle?

<p>CO₂ (D)</p> Signup and view all the answers

What is the function of acetyl-CoA in cellular respiration?

<p>To initiate the Krebs cycle (B)</p> Signup and view all the answers

How does alcoholic fermentation contribute to biotechnology?

<p>It is crucial for brewing and winemaking processes (A)</p> Signup and view all the answers

In which phase of the Krebs cycle is citric acid formed?

<p>Entering phase with acetyl-CoA (D)</p> Signup and view all the answers

What is the link between the electron transport chain and oxidative phosphorylation?

<p>The ETC generates a proton gradient for ATP synthesis (C)</p> Signup and view all the answers

Flashcards

Metabolism

The sum of all chemical reactions in a cell.

Anabolism

The building-up of larger molecules from smaller ones; biosynthesis.

Catabolism

The breaking-down of large molecules into smaller ones, often releasing energy.

Enzyme

A protein catalyst that speeds up chemical reactions in cells.

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Enzyme Structure/substrate interaction

Enzymes bind to substrates (reactants in an active site, reducing activation energy needed for chemical reactions.)

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Activation Energy

The energy needed for a chemical reaction to start.

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ATP

Adenosine triphosphate; a crucial molecule for energy transfer in cells.

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Oxidation/Reduction

Oxidation is the loss of electrons; Reduction is the gain of electrons. These reactions always occur together.

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Aerobic Respiration

The process by which cells generate energy (ATP) from glucose in the presence of oxygen.

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Glycolysis

The breakdown of glucose into two pyruvate molecules, producing ATP and NADH.

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Pyruvate Decarboxylation

The conversion of pyruvate into acetyl-CoA, producing NADH and CO₂.

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Krebs Cycle

A series of reactions that oxidize acetyl-CoA, generating ATP, NADH, FADH₂, and CO₂.

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Electron Transport Chain

A series of protein complexes in the inner mitochondrial membrane that use electrons from NADH and FADH₂ to generate ATP.

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Oxidative Phosphorylation

The process of producing ATP using the energy of electrons from NADH and FADH₂ to drive ATP synthase.

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Anaerobic Respiration

The process of generating ATP without oxygen.

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Fermentation

A type of anaerobic metabolic pathway that regenerates NAD⁺, allowing glycolysis to continue.

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Lactic Acid Fermentation

Fermentation that converts pyruvate into lactate (lactic acid) to regenerate NAD⁺.

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Alcoholic Fermentation

Fermentation that converts pyruvate into ethanol (alcohol) and CO₂ to regenerate NAD⁺.

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Photosynthesis

The process by which plants and some other organisms convert light energy into chemical energy (glucose).

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Light-Dependent Reactions

The reactions in photosynthesis that capture light energy and convert it to chemical energy in the form of ATP and NADPH.

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Light-Independent Reactions (Calvin Cycle)

The reactions in photosynthesis that use ATP and NADPH to convert CO₂ into glucose.

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Chlorophyll

The green pigment in plants that absorbs light energy for photosynthesis.

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Carbon Fixation

The process of converting inorganic carbon (CO₂) into organic carbon (glucose) in photosynthesis.

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Lowering Activation Energy

Enzymes facilitate chemical reactions by lowering the activation energy required for the reaction to occur.

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Energy Sources

Different forms of energy used by cells include thermal, radiant, electrical, mechanical, atomic, and chemical energy.

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Redox Reactions

Oxidation is the loss of electrons, and reduction is the gain of electrons. These reactions always occur in pairs, with an electron donor and acceptor.

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ATP (Adenosine Triphosphate)

The primary energy currency of cells, consisting of adenine, ribose sugar, and three phosphate groups. Energy is released when a phosphate group is removed.

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Where does glycolysis occur?

Glycolysis takes place in the cytoplasm of the cell, which is the fluid-filled region outside the nucleus.

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What does glycolysis produce?

Glycolysis breaks down glucose into two molecules of pyruvate, producing a net gain of 2 ATP molecules and 2 NADH molecules.

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What is the input for glycolysis?

The main input for glycolysis is one molecule of glucose, along with two molecules of NAD⁺ and two molecules of ATP.

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How is the Krebs cycle linked to glycolysis?

The pyruvate produced in glycolysis is transported into the mitochondria, where it is converted into acetyl-CoA, which then enters the Krebs cycle.

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What is the purpose of the Krebs cycle?

The Krebs cycle oxidizes acetyl-CoA, generating 2 ATP, 6 NADH, 2 FADH₂, and 4 CO₂ molecules per glucose molecule.

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Where does the Krebs cycle occur?

The Krebs cycle takes place inside the mitochondrial matrix, a fluid-filled space within the mitochondria.

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What is oxidative phosphorylation?

Oxidative phosphorylation is the process where electrons from NADH and FADH₂ are used to generate ATP via the electron transport chain and ATP synthase.

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What is the role of oxygen in aerobic respiration?

Oxygen acts as the final electron acceptor in the electron transport chain, allowing the process to continue and generate a large amount of ATP.

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How much ATP is produced in aerobic respiration?

Aerobic respiration yields a net gain of 36-38 ATP molecules per glucose molecule, depending on the cell type.

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What happens to pyruvate in anaerobic respiration?

In the absence of oxygen, pyruvate is converted into lactate (in animals) or ethanol (in yeast and some bacteria) to regenerate NAD⁺, allowing glycolysis to continue.

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How does fermentation differ from aerobic respiration?

Fermentation is an anaerobic process that generates ATP through glycolysis only, using alternative electron acceptors to regenerate NAD⁺, resulting in less ATP than aerobic respiration.

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What are some examples of fermentation products?

Fermentation produces various products like lactic acid (in yogurt, cheese), ethanol (in alcoholic beverages), and carbon dioxide (in bread-making).

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What is the role of NAD⁺ in fermentation?

NAD⁺ acts as an electron carrier in glycolysis, which is crucial for the process to continue. Fermentation regenerates NAD⁺, enabling glycolysis to produce ATP even in the absence of oxygen.

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What is the purpose of photosynthesis?

Photosynthesis is the process by which plants and some other organisms convert light energy into chemical energy (glucose), which is then used for growth and other life processes.

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Why is photosynthesis important for the energetics of life?

Photosynthesis is essential for the energetics of life because it converts light energy into chemical energy (glucose), providing a source of energy for virtually all living organisms.

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Study Notes

Metabolism

  • Metabolism encompasses all the chemical reactions within a cell.
  • Two types:
    • Anabolism (Biosynthesis): Builds larger molecules from smaller ones, forming cell structures.
    • Catabolism: Degrades larger molecules into smaller ones, usually releasing energy.

Enzymes

  • Enzymes are protein catalysts that accelerate metabolic reactions.
  • They are not consumed or changed by the reaction.
  • They have an active site for substrates.
  • They lower the activation energy, the energy required to start a reaction.
  • Enzyme activity is greatly affected by temperature and pH.
  • They require cofactors (non-protein components) for some functions.

Energy Sources and Transfer

  • Cells utilize various energy forms: thermal (heat), radiant, electrical, mechanical, atomic, and chemical (energy stored in molecular bonds).
  • Oxidation-reduction reactions (redox) are crucial for energy transfer.
    • Oxidation: Loss of electrons.
    • Reduction: Gain of electrons.
    • Redox reactions always occur together.

ATP

  • ATP (adenosine triphosphate) is the cell's primary energy currency, providing readily available energy from the bond between the second and third phosphate groups.
    • It consists of adenine, ribose, and three phosphate groups.

Aerobic Respiration

  • Aerobic respiration, in the presence of oxygen, is the main pathway for ATP production.
  • It includes four key stages:
    • Glycolysis: Breaks down glucose into pyruvate in the cytoplasm.
    • Pyruvate Decarboxylation: Converts pyruvate to Acetyl-CoA in the mitochondrial matrix.
    • Krebs Cycle: Oxidizes Acetyl-CoA, releasing CO₂ and generating electron carriers (NADH, FADH₂).
    • Electron Transport Chain/Oxidative Phosphorylation: Electrons from NADH & FADH₂ power ATP production through ATP synthase.

Glycolysis

  • Input: 1 glucose, 2 ATP, 2 NAD⁺.
  • Output: 2 pyruvate, 4 ATP (net gain 2 ATP), 2 NADH.
  • Steps: Energy investment, cleavage, energy payoff stages.
  • Crucial for linking to Krebs cycle and oxidative phosphorylation.

Krebs Cycle

  • Cycle happens in the mitochondrial matrix.
  • Input: 2 Acetyl-CoA, 6 NAD⁺, 2 FAD, 2 ADP (or GDP).
  • Output: 4 CO₂, 6 NADH, 2 FADH₂, 2 ATP (or GTP).
  • Regenerates oxaloacetate; links to oxidative phosphorylation by providing electron carriers.

Aerobic Respiration Summary

  • Input: 1 glucose, oxygen.
  • Output: CO₂, H₂O, ~36-38 ATP.

Anaerobic Respiration

  • Occurs without oxygen.
  • Different final electron acceptors (e.g., nitrate, sulfate) than oxygen are used.
  • Yields less ATP than aerobic respiration.
  • Sometimes follows glycolysis by fermentation reactions to regenerate NAD⁺.

Fermentation

  • Fermentation regenerates NAD⁺, allowing glycolysis to continue in the absence of oxygen.
  • Different types:
    • Lactic acid fermentation: Produces lactate from pyruvate.
    • Alcoholic fermentation: Produces ethanol from pyruvate.

Photosynthesis

  • Converts light energy to chemical energy in glucose.

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Description

This quiz covers essential concepts in biochemistry, focusing on metabolism and enzymatic functions. It examines both anabolic and catabolic pathways, as well as the role of enzymes as catalysts in cellular reactions. Test your understanding of energy sources and transfer mechanisms.

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