Metabolism, Energy and Thermodynamics
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Questions and Answers

In an endergonic reaction, the energy content of the products is __________ than the energy content of the reactants.

higher

Which of the following best describes the role of exergonic reactions in cells?

  • To provide the energy needed to drive endergonic reactions. (correct)
  • To decrease the overall entropy of the cell.
  • To store energy for later use in anabolic processes.
  • To synthesize complex molecules from simpler ones.

Cellular respiration is an example of an endergonic reaction.

False (B)

What is the primary purpose of energy coupling in cells?

<p>To use the energy released from exergonic reactions to drive endergonic reactions. (C)</p> Signup and view all the answers

Briefly explain how photosynthesis is an example of an endergonic reaction.

<p>Photosynthesis converts light energy into chemical energy stored in glucose. Because energy is absorbed, it is endergonic.</p> Signup and view all the answers

Which of the following statements best describes the first law of thermodynamics?

<p>The total amount of energy in the universe is constant; energy can be converted from one form to another. (D)</p> Signup and view all the answers

Activation energy is only required for endothermic reactions.

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

Define metabolism in your own words.

<p>Metabolism is the sum of all biochemical reactions in a cell or organism.</p> Signup and view all the answers

__________ is the energy held by a body because of its motion.

<p>kinetic energy</p> Signup and view all the answers

According to the second law of thermodynamics, what tends to increase in the universe?

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

A spontaneous change is best described as a change that:

<p>Continues on its own once started under given conditions. (D)</p> Signup and view all the answers

Which of the following is the correct relationship between the energy of a system and its surroundings according to the first law of thermodynamics?

<p>$E_{surroundings} = -E_{system}$ (C)</p> Signup and view all the answers

The amount of energy needed for a chemical/biochemical reaction to start is called __________.

<p>activation energy</p> Signup and view all the answers

In redox reactions, what process occurs when a molecule loses an electron?

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

Oxidation and reduction reactions can occur independently of each other.

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

What is the name of the mechanism that forms ATP directly in an enzyme-catalyzed reaction during cellular respiration?

<p>substrate level phosphorylation</p> Signup and view all the answers

In the reaction NAD+ + 2 e- + 2 H+ → ______ + H+, the missing product is a reduced form of nicotinamide adenine dinucleotide.

<p>NADH</p> Signup and view all the answers

Which of the following coenzymes is involved in the redox reactions of cellular respiration?

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

Which of the following best describes the role of coenzymes like NAD and FAD in cellular respiration?

<p>To transport electrons between reactions (D)</p> Signup and view all the answers

What type of enzyme catalyzes the reaction in substrate level phosphorylation?

<p>ATPase</p> Signup and view all the answers

During substrate-level phosphorylation, what are the reactants required to produce ATP?

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

Glycolysis converts one molecule of glucose into two molecules of ______.

<p>pyruvate</p> Signup and view all the answers

Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate during glycolysis?

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

The 'pay-off phase' of glycolysis is characterized by the consumption of ATP.

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

During the pay-off phase of glycolysis, glyceraldehyde-3-phosphate (G3P) is converted into 1,3-bisphosphoglycerate by which enzyme?

<p>Glyceraldehyde-3-phosphate Dehydrogenase (D)</p> Signup and view all the answers

Which of the following molecules is produced when 2-phosphoglycerate is converted?

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

Which enzyme catalyzes the transfer of a phosphate group from phosphoenolpyruvate (PEP) to ADP, yielding ATP and pyruvate?

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

What two energy-rich molecules are produced during the pay-off phase of glycolysis through reduction?

<p>ATP and NADH</p> Signup and view all the answers

Phosphorylation involves the transfer of a __________ group, usually from ATP, to another molecule.

<p>phosphate</p> Signup and view all the answers

The enzyme 'Phosphoglucose Isomerase' converts fructose-6-phosphate to glucose-6-phosphate.

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

Which molecule is typically the source of the phosphate group in phosphorylation?

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

FADH2 has a higher energy content than NADH.

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

Which of the following best describes the role of FAD in cellular respiration regarding electrons?

<p>It accepts electrons during the Krebs cycle. (A)</p> Signup and view all the answers

List the first two stages of cellular respiration in order.

<p>Glycolysis; Pyruvate oxidation</p> Signup and view all the answers

What is the initial step in glycolysis that prepares glucose for further breakdown?

<p>Breaking it by activating it first (A)</p> Signup and view all the answers

During which stage of cellular respiration is pyruvate further processed?

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

Match each cellular respiration stage with its primary description:

<p>Glycolysis = Initial breakdown of glucose Pyruvate oxidation = Conversion of pyruvate to acetyl-CoA Krebs Cycle = Oxidation of acetyl-CoA to produce energy carriers</p> Signup and view all the answers

The opposite reaction to phosphorylation is called ___________.

<p>dephosphorylation</p> Signup and view all the answers

A typical muscle cell uses approximately 600 million ATP molecules per minute.

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

In oxidative phosphorylation, oxygen acts as the final ___________ of electrons.

<p>acceptor</p> Signup and view all the answers

Briefly describe the role of NADH and FADH2 in oxidative phosphorylation.

<p>harvest energy and transfer it to ATP</p> Signup and view all the answers

What is the primary purpose of cellular respiration?

<p>to generate energy in the form of ATP</p> Signup and view all the answers

Which of the following processes requires oxygen?

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

In which stage of cellular respiration are enzymes most critical?

<p>All stages require enzymes (D)</p> Signup and view all the answers

What is the initial substrate for glycolysis?

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

Where does glycolysis take place in eukaryotic cells?

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

What is the net ATP gain from glycolysis per molecule of glucose?

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

What is the product of during the preparatory phase for each glucose molecule?

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

What is the function of kinase enzymes in cellular respiration?

<p>Addition of a phosphate group (A)</p> Signup and view all the answers

What is the function of dehydrogenase enzymes in cellular respiration?

<p>Electron transfer to NAD+ and FAD (D)</p> Signup and view all the answers

What is the function of decarboxylase enzymes in cellular respiration?

<p>Removal of carbon dioxide (D)</p> Signup and view all the answers

Match the enzyme class with its function:

<p>Kinase = Catalyzes phosphorylation reactions Dehydrogenase = Catalyzes redox reactions Decarboxylase = Catalyzes the removal of CO2</p> Signup and view all the answers

Flashcards

Endergonic Reactions

Reactions where the products have more energy than the reactants.

Exergonic Reactions

Reactions where the products have less energy than the reactants

Photosynthesis

A process where light energy is converted into chemical energy stored in glucose bonds.

Cellular Respiration

The process by which energy from glucose is released and harnessed into ATP.

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Energy Coupling

Using energy released from exergonic reactions to power endergonic reactions.

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Metabolism

The sum of all biochemical reactions in a cell or organism.

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Potential Energy

Energy held by a body due to its position or condition.

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Kinetic Energy

Energy held by a body because of its motion.

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First Law of Thermodynamics

The total energy in the universe is constant; energy can be converted but not created or destroyed.

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Activation Energy (Ea)

The minimum energy required to start a chemical/biochemical reaction.

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Second Law of Thermodynamics

Reactions proceed spontaneously in the direction that increases the entropy (disorder) of the system.

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Entropy

Randomness and chaos in a system.

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Spontaneous Change

A change that, once started, continues on its own under given conditions without a continuous energy supply.

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Phosphorylation

The transfer of a phosphate group, usually from ATP, to another molecule.

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NAD+ role in cellular respiration

NAD+ accepts 2 electrons and 2 hydrogen ions (2H+) to become NADH + H+.

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FAD Role in Cellular Respiration

FAD accepts 2 electrons and 2 hydrogen ions (2H+) to become FADH2.

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Energy Carriers (in cells)

Molecules that carry high-energy electrons.

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Four main stages of cellular respiration

Glycolysis, Pyruvate oxidation, Krebs Cycle, Electron Transport Chain.

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Glycolysis

The breakdown of glucose.

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Pyruvate Oxidation

Conversion of pyruvate to acetyl-CoA, releasing CO2.

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Krebs Cycle (Citric Acid Cycle)

A series of reactions that extract energy from acetyl-CoA, producing ATP, NADH, and FADH2.

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Redox Reaction

Transfer of electrons between two chemical species.

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Oxidation

Loss of electrons from a molecule; it becomes more positive.

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Reduction

Gain of electrons by a molecule; becomes more negative.

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Paired Redox Reactions

Reactions that occur in pairs; one molecule loses electrons while another gains them.

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Coenzymes (Electron Carriers)

Molecules that assist enzymes in catalyzing redox reactions, carrying electrons.

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NAD+

Nicotinamide adenine dinucleotide; an electron carrier.

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FAD

Flavin adenine dinucleotide; another electron carrier.

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Substrate-Level Phosphorylation

Direct transfer of a phosphate group (Pi) from a substrate to ADP, forming ATP.

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What is Glycolysis?

The process of breaking down glucose into two pyruvate molecules.

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Hexokinase Role

The first step where glucose is phosphorylated to glucose-6-phosphate.

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Phosphoglucose Isomerase

An enzyme that converts glucose-6-phosphate to fructose-6-phosphate.

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Phosphofructokinase (PFK)

Fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate.

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Aldolase Function

Breaks fructose-1,6-bisphosphate into two 3-carbon molecules.

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G3P and DHAP

Glyceraldehyde-3-phosphate and dihydroxyacetone phosphate are created by Aldolase.

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Triosephosphate Isomerase

Converts DHAP into G3P, ensuring both molecules proceed through glycolysis.

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Glyceraldehyde-3-Phosphate Dehydrogenase

G3P is converted into 1,3-bisphosphoglycerate.

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Oxygen's Role

The final electron acceptor in the electron transport chain, essential for ATP production.

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Oxidative Phosphorylation

ATP production that indirectly uses energy from redox reactions involving NADH and FADH2.

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Purpose of Cellular Respiration

To convert the energy stored in food into ATP, which powers cellular activities.

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Aerobic Respiration

Cellular respiration that requires oxygen.

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Anaerobic Respiration

Cellular respiration that does not require oxygen.

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Alcoholic Fermentation

A type of anaerobic respiration that produces ethanol.

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Lactic Acid Fermentation

A type of anaerobic respiration that produces lactic acid.

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Glycolysis Location

The location where glycolysis takes place.

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Net ATP Gain in Glycolysis

The net gain of ATP molecules produced directly during glycolysis, after accounting for the initial investment.

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Kinases

Enzymes that transfer phosphate groups from ATP to other molecules.

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Dehydrogenases

Enzymes involved in redox reactions, transferring electrons.

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Decarboxylases

Enzymes that remove a carbon atom, usually in the form of CO2.

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Study Notes

  • Metabolism is the sum of all biochemical reactions in a cell or organism.
  • Potential energy is the energy held by a body as a result of its position or condition rather than its motion.
  • Kinetic energy is the energy held by a body because of its motion.
  • The first law of thermodynamics states the total amount of energy in the universe is constant.
  • Energy cannot be created or destroyed, but only converted to one form into another.
  • If a physical system gains an amount of energy, another physical system must lose the same amount of energy.
  • Activation Energy (EA) is the amount of energy needed for a chemical/biochemical reaction to start.
  • All chemical reactions, including exothermic reactions, need activation energy to get started.
  • Activation energy is needed so reactants can move together, overcome forces of repulsion, and start breaking bonds.
  • The energy stored in the chemical bonds in glucose is used.
  • Entropy is randomness and chaos.
  • The universe favors Entropy.
  • Energy and Entropy are needed in all reactions
  • A spontaneous change will, once started, continue on its own under given conditions and does not require a permanent supply of energy.
  • In endergonic reactions, the energy content of products is higher than the energy content of reactants.
  • Photosynthesis is an example where light energy is converted to stored chemical energy in the bonds of glucose (C6H12O6).
  • In exergonic reactions, the energy content of products is less than the energy content of reactants.
  • Cellular respiration is an exergonic reaction.
  • Energy from glucose is released and harnessed into ATP at a controlled rate (enzymatic reactions).
  • Energy coupling is the transfer of energy from one reaction to another to drive the second reaction.
  • Phosphorylation is the transfer of a phosphate group, usually from ATP, to another molecule.
  • The four main stages of cellular respiration are:
    • Glycolysis
    • Pyruvate oxidation (Oxidative carboxylation)
    • Krebs Cycle (Citric acid cycle)
    • Electron transport chain (ETC) and Oxidative phosphorylation (Chemiosmosis)
  • Redox reactions involve the transfer of electrons between two chemicals/molecules.
  • Energy metabolism in cells involves oxidation reactions.
  • Oxidation involves the transfer of an electron from a molecule, which is said to be oxidized, to another molecule, which is said to be reduced.
  • An oxidation cannot occur without a corresponding reduction, meaning they are PAIRED reactions.
  • Many important redox reactions in cells require the presence of coenzymes (electron carriers).
  • The redox reactions of cellular respiration commonly involve the coenzymes (electron carriers).
    • NAD: Nicotinamide adenine dinucleotide
    • FAD: Flavin adenine dinucleotide
  • Substrate level phosphorylation: ADP + Pi → ATP
  • A mechanism forming ATP directly in an enzyme-catalyzed reaction
  • This is called Phosphorylation; the opposite reaction is called 'Dephosphorylation'.
  • A single muscle cell recycles 600 million ATP per minute
  • In living things ATP molecules are continuously recycled.
  • Oxidative phosphorylation produces ATP using oxygen as the last electron acceptor.
    • ATP is formed in-directly
    • Uses redox reactions
    • NADH and FADH2 are used
    • These molecules harvest energy and transfer it to ATP at the end of aerobic cellular respiration.
  • Cellular respiration can be aerobic if it requires O2, or anaerobic if no O2 is required.
  • The four stages of cellular respiration are glycolysis, pyruvate oxidation, Krebs cycle, and the electron transport system (ETC) and chemiosmosis.
  • Glycolysis is the very first step in aerobic and anaerobic respiration, occurring in both prokaryotic and eukaryotic cells in the cytosol.
  • Glycolysis activates glucose and breaks it down into 2 pyruvate (pyruvic acid) molecules in the cytoplasm.
  • Enzymes used in cellular respiration include:
    • Kinase which catalyzes Phosphorylation
    • Dehydrogenase which catalyzes Redox
    • Decarboxylase which catalyzes Decarboxylation
    • Isomerase which catalyzes Isomerization
    • Lyase which catalyzes Cleavage
    • Synthase which catalyzes Synthesis
    • Hydrase which catalyzes Hydration
  • Glycolysis includes two major subphases: a preparatory phase and a pay-off phase.
  • The preparatory substage (phase) is when ATP is consumed to activate glucose; it is also known as the investment phase.
  • The first five steps of the glycolysis reactions make up the preparatory or investment phase and it consumes energy to convert the glucose molecule into two molecules of three-carbon sugar molecule (pyruvate).
  • The second phase of glycolysis is known as the pay-off phase, which is characterized by the production of ATP and reduction of NAD+.
  • 2.2% of energy from glucose is transferred to ATP via Glycolysis.

Glycolysis

  • Glycolysis is the first step of both aerobic and anaerobic respiration that happens in cytosol in both prokaryotic and eukaryotic cells and is a series of biochemical reactions controlled by enzymes.
  • Glycolysis has two subfases:
    • investment (preparatory) phase
    • pay-off phase
  • The rate of pyruvate is determined by the enzymes that are present.

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Metabolism encompasses all biochemical reactions in a cell or organism. The first law of thermodynamics dictates that energy cannot be created or destroyed. Activation energy is essential for starting chemical reactions and the universe favors entropy.

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