Biology Chapter on Energy Reactions

Questions and Answers

Describe the difference between exergonic and endergonic reactions and give an example of each.

Exergonic reactions occur when products contain less energy than the reactants; an example is cellular respiration. Endergonic reactions occur when energy is absorbed from the surroundings; an example is photosynthesis.

Define energy coupling and give an example.

Energy coupling occurs when energy from an exergonic reaction is used to facilitate an endergonic reaction; an example is the conversion of ADP and P to ATP (endergonic) and the breakdown of ATP to ADP (exergonic).

Describe how and why negative feedback works.

A metabolic pathway is 'switched off' when an end product inhibits an enzyme earlier in its path; this prevents overproduction of certain substances.

Describe how ATP provides energy for cellular processes and how is ATP regenerated.

ATP provides energy for growth and movement; it is regenerated by the addition of phosphate to ADP. Signup and view all the answers

Describe the catalytic cycle of an enzyme.

The cycle involves lowering activation energy, changing shape to stress substrates, creating a conducive micro-environment, and the active site participating in the chemical reaction. Signup and view all the answers

Write out the summary chemical equation for cellular respiration.

Glucose + 6Oxygen ----> 6Carbon Dioxide + 6Water + ATP Signup and view all the answers

Describe what happens during oxidation and reduction (generally), and give a specific example of each from somewhere in cellular respiration.

Oxidation occurs when a substance loses electrons and reduction occurs when a substance gains electrons; glucose is oxidized during cellular respiration, and oxygen is reduced. Signup and view all the answers

Describe what happens during glycolysis. Include the molecules emphasized in lecture.

Glycolysis breaks down glucose into two pyruvate compounds, releasing two NADH and ATP; molecules involved include glucose and fatty acids. Signup and view all the answers

Describe what happens during pyruvate oxidation and the Citric Acid Cycle. What substance must be present in the mitochondria for these reactions to occur?

Pyruvate oxidation leads to the formation of acetyl-CoA, which enters the Citric Acid Cycle. Oxygen must be present for these reactions to occur. Signup and view all the answers

Describe what happens during the Electron Transport Chain and Chemiosmosis. Explain why these two processes together are called Oxidative Phosphorylation.

Electrons transferred through the chain release energy to pump H+ ions, creating a gradient for ATP synthesis during Chemiosmosis; together, they are called Oxidative Phosphorylation because they involve oxidation reactions to produce ATP. Signup and view all the answers

Describe how lactate formation occurs. Identify the cells of animals in which this process occurs, and explain why it occurs.

Lactate formation occurs in muscle cells during oxygen deficiency; pyruvate is reduced, allowing NADH to regenerate and ATP to be produced through glycolysis. Signup and view all the answers

Identify the various types of organic molecules that can be used for cellular respiration.

Carbohydrates, sugars, glucose, G3P, and pyruvate. Signup and view all the answers

Study Notes

Exergonic vs Endergonic Reactions

Exergonic reactions release energy; products have less energy than reactants.
Example: Cellular respiration, where energy is released from glucose breakdown.
Endergonic reactions absorb energy; products have more energy than reactants.
Example: Photosynthesis, which requires sunlight for energy absorption.

Energy Coupling

Energy coupling involves using energy from an exergonic reaction to drive an endergonic reaction.
Example: ATP formation (endergonic) from ADP and inorganic phosphate, followed by ATP breakdown (exergonic) back to ADP.

Negative Feedback Mechanism

A metabolic pathway is inhibited by its end product to prevent overproduction.
This regulation ensures balanced production of necessary substances in the cell.

ATP and Cellular Energy

ATP powers cellular processes such as growth and movement.
Regeneration of ATP occurs through the addition of a phosphate group to ADP.

Catalytic Cycle of an Enzyme

Energy activation is decreased through the optimal orientation of substrates.
Enzyme shape changes induce strain, leading to transition state formation.
The active site may participate in the reaction but returns to its original configuration post-reaction.

Cellular Respiration Equation

Chemical equation: Glucose + 6Oxygen → 6Carbon Dioxide + 6Water + ATP.
Represents the conversion of glucose and oxygen into energy and by-products.

Oxidation and Reduction in Cellular Respiration

Oxidation: Loss of electrons (e.g., glucose oxidized during respiration).
Reduction: Gain of electrons (e.g., oxygen reduced during aerobic respiration, combines with hydrogen to form water).

Glycolysis Process

Glycolysis breaks one glucose molecule into two pyruvate molecules.
Produces two NADH and ATP molecules per glucose.
Essential for energy production in all living organisms.

Pyruvate Oxidation and Citric Acid Cycle

Pyruvate enters mitochondria; carboxyl group removed as CO2.
Remaining 2-carbon molecule oxidized and attached to CoA, forming Acetyl-CoA.
Acetyl-CoA enters the Citric Acid Cycle, producing NADH and releasing CO2.

Electron Transport Chain and Chemiosmosis

NADH is oxidized, donating electrons to the carrier chain, releasing energy to pump H+ ions.
Oxygen combines with electrons and hydrogen to form water.
Chemiosmosis utilizes H+ gradient to synthesize ATP via ATP synthase, termed oxidative phosphorylation.

Lactate Formation

Occurs in the absence of oxygen, primarily in muscle cells.
Pyruvate is reduced using electrons from NADH, regenerating NAD+ for continued ATP production during glycolysis.

Organic Molecules for Cellular Respiration

Various organic molecules can serve as energy sources, including carbohydrates, which break down into sugars like glucose, further converted to pyruvate.

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Description

This quiz delves into the concepts of exergonic and endergonic reactions, highlighting their differences and examples. It also explores energy coupling, the role of ATP in cellular energy, and the negative feedback mechanisms in metabolic pathways. Test your understanding of these fundamental biochemical processes!