Enzyme Kinetics and Thermodynamics Quiz
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Questions and Answers

What does Vmax represent in the Michaelis-Menton equation?

  • The concentration of substrate at which the reaction rate is half maximal
  • The minimum velocity of an enzyme-catalyzed reaction
  • The rate of reaction when the enzyme is at low substrate concentration
  • The maximum rate at which an enzyme can catalyze a reaction (correct)

In the context of enzyme kinetics, what does Km represent?

  • The overall maximum substrate concentration in the reaction
  • The concentration of substrate at which the reaction velocity is 50% of Vmax (correct)
  • The concentration of substrate where the reaction rate is at its peak
  • The rate of reaction at maximum substrate concentration

How is Vmax and Km determined more accurately from experimental data?

  • By creating a Lineweaver-Burk plot using reciprocals of rate and substrate concentration (correct)
  • From a Michaelis-Menton plot directly using reaction rates
  • By observing the rate of reaction at varying temperatures
  • Through genetic sequencing of the enzyme's encoding gene

What can changes in genes cause regarding enzymes?

<p>Variations in the active site leading to altered substrate specificity (D)</p> Signup and view all the answers

What is the significance of natural selection in the evolution of enzymes?

<p>It favors mutated alleles if the new enzyme function is beneficial (C)</p> Signup and view all the answers

What type of energy is associated with the random movement of atoms or molecules?

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

Which law states that energy in an isolated system cannot be exchanged with its surroundings?

<p>First Law of Thermodynamics (A)</p> Signup and view all the answers

What do we call the potential energy available for release in a chemical reaction?

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

In the context of thermodynamics, what is an open system?

<p>A system that exchanges both energy and matter (B)</p> Signup and view all the answers

According to the second law of thermodynamics, what happens during energy transfer?

<p>Some energy is converted to thermal energy and lost as heat (D)</p> Signup and view all the answers

What is the primary function of P680 in Photosystem II?

<p>To absorb light at 680 nm and transfer electrons (A)</p> Signup and view all the answers

Which of the following processes occurs first during linear electron flow?

<p>P680 absorbs a photon and excites an electron (B)</p> Signup and view all the answers

What happens to P680 after it donates an electron to the primary electron acceptor?

<p>It becomes P680+ and acts as an oxidizing agent (A)</p> Signup and view all the answers

During which part of photosynthesis is ATP produced?

<p>Both linear and cyclic electron flow (C)</p> Signup and view all the answers

Which of the following best describes the role of NADP+ in the light reactions?

<p>It is reduced to NADPH by accepting electrons (C)</p> Signup and view all the answers

What characterizes an exergonic reaction?

<p>It generates free energy and occurs spontaneously. (D)</p> Signup and view all the answers

What does a negative value of ΔG indicate about a process?

<p>The process is spontaneous. (D)</p> Signup and view all the answers

How is activation energy (EA) typically supplied to a reaction?

<p>In the form of thermal energy absorbed from surroundings. (C)</p> Signup and view all the answers

What is the role of enzymes in chemical reactions?

<p>They lower the activation energy (EA) required for the reaction. (D)</p> Signup and view all the answers

What change in free energy indicates a nonspontaneous process?

<p>ΔG &gt; 0 (C)</p> Signup and view all the answers

Which equation represents the relationship between ΔG, ΔH, ΔS, and T?

<p>ΔG = ΔH - TΔS (C)</p> Signup and view all the answers

What does a process with zero or positive ΔG signify?

<p>The process is never spontaneous. (C)</p> Signup and view all the answers

What is meant by the transition state in a chemical reaction?

<p>The maximum energy state along the reaction pathway. (A)</p> Signup and view all the answers

What is the function of malate dehydrogenase in fatty acid synthesis?

<p>It converts oxaloacetate to malate using NADH. (D)</p> Signup and view all the answers

Which statement is true about the transfer of energy in biological systems?

<p>Chemical elements essential to life are recycled within ecosystems. (B)</p> Signup and view all the answers

What is a key characteristic of catabolic pathways in cellular respiration?

<p>They release stored energy by breaking down complex molecules. (B)</p> Signup and view all the answers

How is glucose primarily broken down in aerobic respiration?

<p>By utilizing the electron transport chain. (B)</p> Signup and view all the answers

What role do NADH and FADH2 play in cellular respiration?

<p>They donate electrons to the electron transport chain. (C)</p> Signup and view all the answers

What is the primary purpose of oxidative phosphorylation in cellular respiration?

<p>To synthesize ATP through ATP synthase. (B)</p> Signup and view all the answers

Which statement accurately describes redox reactions?

<p>Reduction increases the amount of positive charge. (B)</p> Signup and view all the answers

What distinguishes aerobic respiration from anaerobic respiration?

<p>Aerobic respiration requires oxygen, while anaerobic does not. (D)</p> Signup and view all the answers

Which statement best describes the process of glycolysis?

<p>It converts glucose into pyruvate and produces NADH. (A)</p> Signup and view all the answers

What is formed during fermentation when no oxygen is present?

<p>Ethanol and lactate or other products are generated. (C)</p> Signup and view all the answers

What is the fate of acetyl CoA in cellular respiration?

<p>It enters the citric acid cycle for further oxidation. (A)</p> Signup and view all the answers

How does the electron transport chain contribute to ATP synthesis?

<p>It creates a proton gradient that drives ATP synthase. (B)</p> Signup and view all the answers

What is the primary source of high-energy electrons in cellular respiration?

<p>Organic molecules rich in hydrogen. (D)</p> Signup and view all the answers

Which of the following molecules is a product of cellular respiration?

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

How do living cells primarily obtain energy to perform work?

<p>By consuming organic molecules from other organisms. (C)</p> Signup and view all the answers

What is the primary function of acetyl CoA in the citric acid cycle?

<p>To combine with oxaloacetate and form citrate (C)</p> Signup and view all the answers

How many molecules of ATP are produced per turn of the citric acid cycle?

<p>1 (D)</p> Signup and view all the answers

What is the purpose of chemiosmosis in cellular respiration?

<p>To use the H+ gradient to synthesize ATP (D)</p> Signup and view all the answers

Which complex of the electron transport chain ultimately transfers electrons to oxygen?

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

What happens if oxygen is not available during cellular respiration?

<p>Fermentation or anaerobic respiration occurs (C)</p> Signup and view all the answers

What is the primary product of lactic acid fermentation?

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

During which phase of cellular respiration is most ATP generated?

<p>Electron transport chain (C)</p> Signup and view all the answers

What component of the citric acid cycle is regenerated at the end of the cycle?

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

Which of the following is true about the electron transport chain?

<p>It involves a series of redox reactions (A)</p> Signup and view all the answers

Which component of the ATP synthase facilitates the phosphorylation of ADP to ATP?

<p>F1 unit (D)</p> Signup and view all the answers

What is released as a byproduct of the citric acid cycle?

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

By what mechanism do fermentation processes generate ATP?

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

What is the role of the proton-motive force in cellular respiration?

<p>To power ATP synthesis through ATP synthase (B)</p> Signup and view all the answers

Flashcards

Kinetic Energy

Energy associated with motion

Thermal Energy

Kinetic energy of random atomic/molecular movement

Potential Energy

Energy due to position or structure

Chemical Energy

Potential energy stored in chemical bonds

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First Law of Thermodynamics

Energy cannot be created or destroyed, only transferred or transformed.

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Free Energy

Energy that can do work under a uniform temperature and pressure, like in a living cell.

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Exergonic Reaction

A reaction that releases free energy, making it spontaneous.

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Endergonic Reaction

A reaction that absorbs free energy, making it non-spontaneous, requiring energy input.

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ΔG

The change in free energy during a reaction, indicating spontaneity.

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Activation Energy

The initial energy needed to start a chemical reaction.

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Catalyst

A substance that speeds up a reaction without being consumed by the reaction.

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Enzyme

A biological catalyst, usually a protein, that speeds up reactions in living organisms.

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How do enzymes affect activation energy?

Enzymes lower the activation energy of a reaction by stabilizing the transition state, making it easier for the reaction to occur.

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Enzyme active site

The specific region on an enzyme where the substrate binds and the catalytic reaction occurs.

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Vmax

The maximum velocity of an enzyme-catalyzed reaction when all active sites are saturated with substrate.

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Michaelis-Menton plot

A graph that shows the relationship between substrate concentration and the rate of an enzyme reaction.

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Lineweaver-Burk plot

A linear transformation of the Michaelis-Menton plot, used to determine Km and Vmax more accurately.

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P680

The reaction-center chlorophyll a of Photosystem II (PS II), which absorbs light best at a wavelength of 680 nm.

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P700

The reaction-center chlorophyll a of Photosystem I (PS I), which absorbs light best at a wavelength of 700 nm.

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Linear electron flow

The primary pathway of electron flow in photosynthesis, involving both photosystems (PS II and PS I) and producing ATP and NADPH using light energy.

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Water splitting

The process by which water molecules are split by enzymes in Photosystem II, releasing electrons that replace those lost by P680.

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P680+

The oxidized form of P680 (reaction-center chlorophyll a of PS II) after losing an electron, which becomes the strongest known biological oxidizing agent.

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Citrate's role in FA synthesis

Citrate, a product of the citric acid cycle, is NOT directly used in fatty acid synthesis. Instead, it's recycled back to oxaloacetate.

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Oxaloacetate to malate

Oxaloacetate is converted to malate by the enzyme malate dehydrogenase, using NADH as a reducing agent.

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Malate's journey

Malate is converted to pyruvate, which can then be transported back into the mitochondria.

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Malate enzyme's role

The enzyme 'malate enzyme' generates NADPH, a vital reducing agent used in fatty acid synthesis.

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Oxaloacetate's inability

Oxaloacetate cannot cross the mitochondrial membrane directly.

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Cellular respiration: What is it?

Cellular respiration is a set of metabolic reactions that break down organic molecules to produce energy (ATP).

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Energy source for cells

Living cells require energy from outside sources like sunlight or food to perform vital functions.

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Types of cellular work

Cellular work includes processes like building molecules, transporting substances across membranes, movement, and reproduction.

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Energy flow in ecosystems

Sunlight is the primary energy source in ecosystems. It's converted into chemical energy by plants, and then flows through food chains.

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Recycling in ecosystems

Essential chemical elements are constantly recycled within ecosystems.

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Photosynthesis role

Photosynthesis uses sunlight to convert carbon dioxide and water into oxygen and organic molecules, providing food for other organisms.

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Cellular respiration: Energy conversion

Cells use the energy stored in organic molecules (from food) to generate ATP, the main energy currency of the cell.

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Catabolic pathways in cellular respiration

Catabolic pathways break down complex molecules into simpler ones, releasing stored energy.

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Redox reactions in cellular respiration

Redox reactions involve the transfer of electrons, a process that plays a vital role in energy release during cellular respiration.

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Fermentation vs. Aerobic respiration

Fermentation is a partial breakdown of sugars without oxygen, while aerobic respiration uses oxygen to extract more energy.

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Pyruvate Oxidation

The conversion of pyruvate (from glycolysis) into acetyl CoA, a key molecule for the citric acid cycle. This involves the removal of a carbon dioxide molecule and the reduction of NAD+ to NADH.

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Acetyl CoA Formation

The joining of a two-carbon fragment from pyruvate with coenzyme A, forming acetyl CoA. This occurs after the oxidation of pyruvate in the mitochondrial matrix.

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Citric Acid Cycle

A series of eight enzymatic reactions that completes the breakdown of glucose by oxidizing the acetyl group of acetyl CoA to carbon dioxide. This process generates ATP, NADH, and FADH2.

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Oxaloacetate

A four-carbon molecule that is a key component of the citric acid cycle. It combines with acetyl CoA to start the cycle and is regenerated at the end.

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Electron Transport Chain

A series of protein complexes embedded in the inner mitochondrial membrane that transfer electrons from NADH and FADH2 to oxygen, releasing energy that is used to pump protons (H+) across the membrane.

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Oxidative Phosphorylation

The process of ATP synthesis driven by the flow of protons (H+) across the inner mitochondrial membrane, powered by the electron transport chain. This is the main energy production pathway in cellular respiration.

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Proton-motive force

The energy stored in a proton (H+) gradient across a membrane, such as the inner mitochondrial membrane. This gradient is used to power ATP synthesis in oxidative phosphorylation.

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ATP Synthase

A protein complex embedded in the inner mitochondrial membrane that uses the energy of the proton gradient to synthesize ATP from ADP and inorganic phosphate.

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Anaerobic Respiration

A type of respiration that uses an electron transport chain with a final electron acceptor other than oxygen, such as sulfate, to produce ATP.

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Fermentation

A metabolic process that produces ATP without using an electron transport chain. It involves glycolysis followed by reactions that regenerate NAD+ for continued glycolysis.

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Lactic Acid Fermentation

A type of fermentation that produces lactic acid as a byproduct. This occurs in muscle cells during intense exercise when oxygen is limited.

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Alcohol Fermentation

A type of fermentation that produces ethanol (alcohol) and carbon dioxide as byproducts. This is used by yeasts to produce alcoholic beverages and bread.

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Substrate-Level Phosphorylation

A method of ATP synthesis that occurs directly during glycolysis and the citric acid cycle, where a phosphate group is transferred from a substrate molecule to ADP.

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Chemiosmosis

The coupling of the energetic flow of protons across the membrane (proton motive force) with the synthesis of ATP. It's essentially the process of using energy stored in a proton gradient to drive cellular work.

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How does the electron transport chain generate ATP indirectly?

The electron transport chain powers ATP synthesis indirectly by creating a proton gradient across the inner mitochondrial membrane. This gradient is then used by ATP synthase to generate ATP, a process called oxidative phosphorylation.

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Study Notes

General Chemistry Concepts

  • Matter in the universe is composed of atoms
  • Atoms consist of subatomic particles (neutrons, protons, and electrons)
  • Neutrons and protons form the atomic nucleus
  • Electrons orbit the nucleus
  • Neutron and proton mass are nearly identical and measured in daltons
  • The periodic table displays electron distribution for each element
  • Valence electrons determine chemical behavior
  • Elements with full valence shells are chemically inert

Organization of Atoms

  • Electrons are organized into orbitals
  • An orbital is the three-dimensional space where an electron is found 90% of the time
  • Electron shells have a specific number of orbitals
  • Atoms with incomplete valence shells share or transfer valence electrons with other atoms
  • These interactions form chemical bonds

Chemical Bonds

  • Ionic interactions occur when one atom strips electrons from another atom
  • Charged atoms (ions) form ionic bonds
  • Covalent bonds form when atoms share one or more pairs of valence electrons
  • A molecule consists of two or more atoms held together by covalent bonds
  • Single bonds share one pair of valence electrons
  • Double bonds share two pairs
  • Hydrogen bonds form when a hydrogen atom covalently bonded to a highly electronegative atom is also attracted to another electronegative atom
  • Van der Waals interactions occur when molecules are close together

Biological Molecules

  • Organisms are composed of matter
  • Life's four major classes of biological molecules are carbohydrates, lipids, proteins, and nucleic acids
  • Macromolecules are large molecules that are complex
  • Macromolecules have unique properties arising from the arrangement of their atoms
  • Their processing and synthesis is catalysed by enzymes

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Description

Test your knowledge on enzyme kinetics, including the Michaelis-Menten equation, Vmax, and Km. Delve into thermodynamics concepts like energy transfer and systems. This quiz covers essential principles in biochemistry and photosynthesis processes.

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