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?

680 nm Signup and view all the answers

What process occurs at Photosystem I to generate NADPH?

Uses high energy electrons to reduce NADP+ Signup and view all the answers

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

Kinetic energy Signup and view all the answers

Which statement accurately describes oxidation in a chemical reaction?

Loss of electrons leading to lower energy Signup and view all the answers

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

Energy can neither be created nor destroyed Signup and view all the answers

What does a positive ΔG indicate about a chemical reaction?

Energy must be supplied for the reaction Signup and view all the answers

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

Decreases the activation energy needed for the reaction Signup and view all the answers

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

The reaction releases energy Signup and view all the answers

What distinguishes exergonic reactions from endergonic reactions?

Exergonic reactions occur spontaneously Signup and view all the answers

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

Entropy increases spontaneously over time Signup and view all the answers

What is the final electron acceptor in anaerobic respiration?

Inorganic molecules other than oxygen Signup and view all the answers

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

Lactic acid fermentation Signup and view all the answers

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

Beta-oxidation Signup and view all the answers

Which of the following statements about ATP yield is correct?

Fats yield significantly more energy during respiration than glucose. Signup and view all the answers

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

It is removed through deamination. Signup and view all the answers

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

Alpha-ketoglutarate Signup and view all the answers

Which statement accurately relates photosynthesis and respiration?

The products of photosynthesis serve as the raw materials for respiration. Signup and view all the answers

What is the first step in the catabolism of fats?

Beta-oxidation Signup and view all the answers

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

5' to 3' Signup and view all the answers

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

To prevent reformation of hydrogen bonds Signup and view all the answers

What distinguishes continuous replication from discontinuous replication?

Only the leading strand can be synthesized continuously. Signup and view all the answers

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

To synthesize new DNA strands Signup and view all the answers

What is the function of DNA ligase during DNA replication?

To join Okazaki fragments together Signup and view all the answers

What is the first step in DNA replication?

Unwinding of the double helix Signup and view all the answers

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

DNA polymerase I Signup and view all the answers

How many origins of replication do eukaryotic genomes typically have?

Approximately 30,000 Signup and view all the answers

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

Through base pairing with the template strand Signup and view all the answers

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

Prokaryotes have simpler genome structures Signup and view all the answers

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

Remove mispaired bases Signup and view all the answers

What is the role of telomerase in eukaryotic DNA replication?

To extend the telomeres Signup and view all the answers

What role does primase play in DNA replication?

It provides RNA primers for DNA synthesis Signup and view all the answers

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

Prokaryotes have single circular chromosomes Signup and view all the answers

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

DNA polymerase delta and epsilon Signup and view all the answers

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

The lagging strand cannot be fully replicated Signup and view all the answers

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

To convert ADP into ATP as protons flow into the stroma. Signup and view all the answers

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

RuBP Signup and view all the answers

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

3-phosphoglycerate (PGA) Signup and view all the answers

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

6 Signup and view all the answers

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

They are used to regenerate RuBP. Signup and view all the answers

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

To transport electrons to NADP+ reductase. Signup and view all the answers

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

Calvin cycle Signup and view all the answers

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

Rubisco Signup and view all the answers

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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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.