Energy and Enzymes in Biology : Biology Unit 2
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Questions and Answers

Which pigment is primarily responsible for the absorption of violet-blue and red light?

  • Chlorophyll a (correct)
  • Chlorophyll b
  • Carotenoids
  • Accessory pigments

What is the main role of carotenoids in plants?

  • Transport electrons to the electron transport chain
  • Split water molecules during photolysis
  • Absorb blue-green light and protect cells as antioxidants (correct)
  • Act as primary pigments converting light energy

What function does the antenna complex of the photosystem serve?

  • Replenishes the chlorophyll electrons
  • Transfers electrons to the electron acceptor
  • Splits water molecules to release oxygen
  • Captures photons of light and transfers energy (correct)

Which wavelength of light does Photosystem II primarily absorb?

<p>680 nm (C)</p> Signup and view all the answers

What process occurs at Photosystem I to generate NADPH?

<p>Uses high energy electrons to reduce NADP+ (C)</p> Signup and view all the answers

What type of energy is defined as the energy of motion?

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

Which statement accurately describes oxidation in a chemical reaction?

<p>Loss of electrons leading to lower energy (A)</p> Signup and view all the answers

According to the first law of thermodynamics, which of the following is true?

<p>Energy can neither be created nor destroyed (C)</p> Signup and view all the answers

What does a positive ΔG indicate about a chemical reaction?

<p>Energy must be supplied for the reaction (A)</p> Signup and view all the answers

How does the presence of an enzyme affect a chemical reaction?

<p>Decreases the activation energy needed for the reaction (D)</p> Signup and view all the answers

What is indicated by a negative ΔG in a chemical reaction?

<p>The reaction releases energy (B)</p> Signup and view all the answers

What distinguishes exergonic reactions from endergonic reactions?

<p>Exergonic reactions occur spontaneously (C)</p> Signup and view all the answers

Which of the following best describes entropy according to the second law of thermodynamics?

<p>Entropy increases spontaneously over time (C)</p> Signup and view all the answers

What is the final electron acceptor in anaerobic respiration?

<p>Inorganic molecules other than oxygen (C)</p> Signup and view all the answers

Which type of fermentation involves the conversion of pyruvate into lactic acid?

<p>Lactic acid fermentation (B)</p> Signup and view all the answers

What process must fatty acids undergo before entering the Krebs cycle?

<p>Beta-oxidation (A)</p> Signup and view all the answers

Which of the following statements about ATP yield is correct?

<p>Fats yield significantly more energy during respiration than glucose. (A)</p> Signup and view all the answers

What happens to the amino group of amino acids during catabolism?

<p>It is removed through deamination. (C)</p> Signup and view all the answers

Which of the following products can enter the Krebs cycle after catabolism of amino acids?

<p>Alpha-ketoglutarate (D)</p> Signup and view all the answers

Which statement accurately relates photosynthesis and respiration?

<p>The products of photosynthesis serve as the raw materials for respiration. (C)</p> Signup and view all the answers

What is the first step in the catabolism of fats?

<p>Beta-oxidation (B)</p> Signup and view all the answers

What direction does DNA polymerase synthesize the new strand during replication?

<p>5' to 3' (C)</p> Signup and view all the answers

What is the role of single-stranded binding proteins (SSBs) during DNA replication?

<p>To prevent reformation of hydrogen bonds (C)</p> Signup and view all the answers

What distinguishes continuous replication from discontinuous replication?

<p>Only the leading strand can be synthesized continuously. (B)</p> Signup and view all the answers

What is the primary function of DNA polymerase III in DNA replication?

<p>To synthesize new DNA strands (D)</p> Signup and view all the answers

What is the function of DNA ligase during DNA replication?

<p>To join Okazaki fragments together (A)</p> Signup and view all the answers

What is the first step in DNA replication?

<p>Unwinding of the double helix (C)</p> Signup and view all the answers

Which enzyme is responsible for replacing RNA primers with DNA nucleotides on the lagging strand?

<p>DNA polymerase I (B)</p> Signup and view all the answers

How many origins of replication do eukaryotic genomes typically have?

<p>Approximately 30,000 (C)</p> Signup and view all the answers

How does DNA polymerase ensure that nucleotides added are correct during replication?

<p>Through base pairing with the template strand (B)</p> Signup and view all the answers

What is the main reason prokaryotic replication is faster than eukaryotic replication?

<p>Prokaryotes have simpler genome structures (A)</p> Signup and view all the answers

What does the 3’ to 5’ exonuclease activity of DNA polymerase allow it to do?

<p>Remove mispaired bases (B)</p> Signup and view all the answers

What is the role of telomerase in eukaryotic DNA replication?

<p>To extend the telomeres (B)</p> Signup and view all the answers

What role does primase play in DNA replication?

<p>It provides RNA primers for DNA synthesis (B)</p> Signup and view all the answers

What characteristic differentiates the chromosome structure of prokaryotes from that of eukaryotes?

<p>Prokaryotes have single circular chromosomes (A)</p> Signup and view all the answers

Which enzymes perform functions similar to DNA polymerase III in eukaryotic DNA replication?

<p>DNA polymerase delta and epsilon (C)</p> Signup and view all the answers

What problem arises during the replication of linear chromosomes in eukaryotes?

<p>The lagging strand cannot be fully replicated (B)</p> Signup and view all the answers

What is the role of ATP synthase in the process of photophosphorylation?

<p>To convert ADP into ATP as protons flow into the stroma. (C)</p> Signup and view all the answers

Which molecule is primarily responsible for fixing carbon dioxide during the Calvin cycle?

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

What is the first stable product formed during the Calvin cycle?

<p>3-phosphoglycerate (PGA) (D)</p> Signup and view all the answers

How many turns of the Calvin cycle are needed to produce one molecule of glucose?

<p>6 (B)</p> Signup and view all the answers

What happens to the remaining G3P molecules after one is released from the Calvin cycle?

<p>They are used to regenerate RuBP. (A)</p> Signup and view all the answers

What is the function of ferredoxin in the electron transport chain?

<p>To transport electrons to NADP+ reductase. (C)</p> Signup and view all the answers

Which of the following processes occurs in the stroma of the chloroplasts?

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

Which enzyme catalyzes the fixation of carbon dioxide in the Calvin cycle?

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

Flashcards

Photosystem

A complex of pigments and proteins that capture light energy.

Antenna Complex

A group of accessory pigments, including chlorophyll b and carotenoids, that capture photons of light and transfer energy between pigment molecules.

Photosystem II (PSII)

This key pigment absorbs light (primarily at 680 nm) and excites electrons within the reaction center, leading to the splitting of water molecules.

Photosystem I (PSI)

This photosystem absorbs light (primarily at 700 nm) and energizes electrons coming from PSII, ultimately creating NADPH.

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Photolysis

This process uses energy from absorbed photons to split water molecules into oxygen (O2), protons (H+), and electrons in PSII.

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Anaerobic respiration

A metabolic process that uses an inorganic molecule other than oxygen (like sulfur, carbon dioxide, or metals) as the final electron acceptor to produce ATP.

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Fermentation

The breakdown of glucose in the absence of oxygen, producing a small amount of ATP and regenerating NAD+ for glycolysis to continue.

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Ethanol fermentation

A type of fermentation where yeast converts pyruvate into ethanol (alcohol) and carbon dioxide.

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Lactic acid fermentation

A type of fermentation where certain animal cells (like muscle cells) convert pyruvate into lactic acid.

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Protein catabolism

The process of breaking down proteins into individual amino acids and then converting their carbon skeletons into molecules that can enter glycolysis or the Krebs cycle.

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Fat catabolism

The process of breaking down fats into fatty acids and glycerol, which are then converted into two-carbon acetyl groups that enter the Krebs cycle.

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Beta-oxidation

The process of converting fatty acids into two-carbon acetyl groups, which are then combined with coenzyme A to form acetyl-CoA, which enters the Krebs cycle.

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Coenzyme A (CoA)

A type of organic molecule that combines with acetyl groups to form acetyl-CoA, which enters the Krebs cycle.

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DNA helicase

Enzyme that unwinds the DNA double helix, separating the two parental strands to serve as templates for replication.

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Single-stranded binding proteins (SSBs)

Proteins that bind to the separated DNA strands, preventing them from reforming hydrogen bonds with each other.

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DNA gyrase (topoisomerase in eukaryotes)

Enzyme that relieves torsional strain caused by the unwinding of the DNA helix, preventing supercoiling.

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Primase

Enzyme that synthesizes short RNA primers, providing a starting point for DNA synthesis.

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Continuous replication

This describes the synthesis of the new DNA strand in the same direction as the replication fork movement.

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Discontinuous replication

This describes the synthesis of the new DNA strand in the opposite direction of the replication fork movement.

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Okazaki Fragments

Short fragments of DNA synthesized on the lagging strand during replication.

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DNA Ligase

Enzyme that joins the Okazaki fragments together to form a continuous strand on the lagging strand.

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Electron Transport Chain (ETC) in Photosynthesis

Movement of electrons through the electron transport chain (ETC) in the thylakoid membrane, powered by light energy, which leads to the pumping of protons from the stroma into the thylakoid lumen.

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Proton Gradient

The difference in proton concentration between the thylakoid lumen and the stroma, created by the ETC.

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Photophosphorylation

Process where ATP synthase uses the potential energy stored in the proton gradient to generate ATP from ADP and inorganic phosphate.

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Light-Dependent Reactions (Photosynthesis)

The process by which light energy is used to excite electrons in photosystem II (PSII), initiating the electron transport chain (ETC).

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NADPH

A molecule used to carry electrons during photosynthesis, ultimately reducing NADP+ to NADPH.

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Carbon Fixation

Process by which carbon dioxide is converted into organic molecules by the Calvin cycle.

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3-Phosphoglycerate (PGA)

The first stable product formed in the Calvin cycle, a 3-carbon molecule.

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Rubisco

An enzyme that catalyzes the initial step of carbon fixation in the Calvin cycle, attaching carbon dioxide to RuBP.

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Kinetic Energy

The energy of motion. It is the energy that an object possesses due to its movement. Examples include a moving car, a flowing river, or a spinning top.

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Potential Energy

Stored energy. It is the energy that an object possesses due to its position or state. Examples include a stretched rubber band, a book on a shelf, or a battery.

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Oxidation

A chemical reaction where a molecule loses one or more electrons, resulting in a decrease in overall electron density and increasing its positive charge.

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Reduction

A chemical reaction where a molecule gains one or more electrons, resulting in an increase in overall electron density and decreasing its positive charge.

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Free Energy

The total energy of a system, representing the energy available to do work. It often refers specifically to the Gibbs free energy, which takes into account enthalpy and entropy.

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The First Law of Thermodynamics

The first law states that energy can't be created or destroyed, only transformed from one form to another. Think of a light bulb - the energy is transformed from electrical to light and heat energy, but the total amount remains the same.

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The Second Law of Thermodynamics

The second law states that disorder (entropy) always increases in an isolated system. Think of a messy room - it's easier for it to get messier than to become organized.

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Enzyme

A biological catalyst, usually a protein, that speeds up a specific chemical reaction without changing the overall energy change of the reaction itself. It does this by lowering the activation energy needed to start the reaction. Think of it as the helper that makes the reaction happen faster.

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DNA polymerase III

The main enzyme responsible for synthesizing new DNA strands during DNA replication. It adds nucleotides to the 3' end of the primer or growing DNA strand.

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Clamp loader and sliding clamp

A protein complex that holds DNA polymerase III in place on the DNA during replication. It allows DNA polymerase III to efficiently move along the DNA template.

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DNA polymerase I

An enzyme that removes RNA primers during DNA replication and replaces them with DNA nucleotides, specifically on the lagging strand.

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Genome size and structure in replication

Prokaryotes have small genomes with a single circular chromosome, while eukaryotes have much larger genomes with multiple linear chromosomes.

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Replication machinery in prokaryotes and eukaryotes

Prokaryotes use primarily DNA polymerase III for both leading and lagging strands, while eukaryotes use DNA polymerase delta and epsilon for the same function.

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Chromosome ends in replication

Prokaryotes lack telomeres due to their circular chromosomes, while eukaryotes have telomeres at the ends of their linear chromosomes to prevent DNA loss during replication.

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Speed of replication in prokaryotes and eukaryotes

Prokaryotic replication is faster due to simpler genome structure and less regulation, while eukaryotic replication is slower and tightly regulated.

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Study Notes

Energy Flow

  • Energy is the potential to do work
  • Kinetic energy is the energy of motion
  • Potential energy is stored energy
  • Oxidation is the loss of electrons (lower energy)
  • Reduction is the gain of electrons (higher energy)
  • Redox reactions combine oxidation and reduction
  • The first law of thermodynamics states that energy cannot be created or destroyed.
  • The second law of thermodynamics states that entropy (disorder) is constantly increasing.

Calculating Energy

  • ΔG° = ΔH° - TAS°
  • ΔG = free energy (energy available to do work)
  • ΔH = change in enthalpy (energy associated with chemical bonds)
  • T = absolute temperature (in Kelvin)
  • ΔS = change in entropy (disorder)
  • If ΔG is negative, energy is released (exergonic)
  • If ΔG is positive, energy is required (endergonic)

Enzymes

  • Enzymes speed up chemical reactions (catalysts)
  • Enzymes are not consumed or changed in the process
  • Enzymes lower activation energy, accelerating reactions
  • Enzymes bind substrates at the active site

Biochemical Pathways and Feedback Inhibition

  • Biochemical pathways are linked reactions with products serving as substrates
  • Feedback inhibition: the end product of a pathway regulates the earlier steps (often the first) in the pathway
  • Feedback prevents overproduction of a specific product, conserving energy
  • Products bind to an allosteric site of the enzyme, changing its shape and inhibiting activity

ATP

  • ATP (adenosine triphosphate) stores energy in the covalent bonds between its phosphate groups
  • ATP releases energy when a phosphate group is removed (hydrolysis)
  • Cells rely on continuous regeneration of ATP through cellular respiration

Energy From Electrons

  • Autotrophs convert the sun's energy into chemical energy (e.g., plants)
  • Heterotrophs obtain energy by consuming other organisms
  • Electron carriers, like NAD+, accept and transfer electrons efficiently in cellular respiration

Cellular Respiration - Glycolysis

  • Glycolysis (splitting of glucose) occurs in the cytosol
  • In glycolysis, a 6-carbon glucose molecule is broken down into two 3-carbon pyruvate molecules
  • ATP is produced (net gain 2 ATP)
  • NADH molecules are produced

Cellular Respiration - Pyruvate Oxidation

  • Pyruvate oxidation occurs in the mitochondrial matrix
  • Pyruvate is oxidized to form acetyl-CoA, releasing CO2
  • NADH is produced
  • Acetyl-CoA enters the Krebs cycle

Cellular Respiration - Krebs Cycle

  • Occurs in the mitochondrial matrix
  • Acetyl-CoA combines with oxaloacetate to form citrate
  • Through several reactions CO2, NADH, and FADH2 are released
  • Results in ATP production (via substrate-level phosphorylation)

Cellular Respiration - Electron Transport Chain and Chemiosmosis

  • Occurs in the inner mitochondrial membrane
  • Electrons from NADH and FADH2 move through the ETC, pumping H+ ions into the intermembrane space
  • H+ gradient creates a proton motive force
  • ATP synthase uses the flow of H+ ions to produce ATP

Photosynthesis

  • Photosynthesis converts light energy into chemical energy
  • Light-dependent reactions capture light energy and synthesize ATP and NADPH; water is split, generating oxygen
  • Calvin cycle uses ATP and NADPH to convert CO2 into glucose

DNA Replication

  • DNA replication is semiconservative, producing two identical DNA molecules from one original molecule
  • DNA polymerase synthesizes new DNA strands (5'-3' direction)
  • Leading strand synthesis is continuous; lagging strand synthesis is discontinuous (Okazaki fragments)

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BIOL 1105 Test 2 PDF

Description

Explore the fundamental concepts of energy flow in biological systems, including the distinctions between kinetic and potential energy. Understand the role of enzymes as catalysts in biochemical reactions and learn the principles governing energy transformations, including thermodynamics and Gibbs free energy.

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