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WorksheetsTOPIC 3.1 Enzymes: Introduction to Enzyme Function
Total questions: 108
Worksheet time: 54mins
Which statement best describes the primary role of enzymes in cells?
They store genetic information.
They act as biological catalysts that lower activation energy.
They function as structural carbohydrates.
They provide energy by being broken down during reactions.
Enzymes are a type of which biomolecule, and what is their monomer?
Carbohydrate; monosaccharide
Protein; amino acid
Lipid; fatty acid
Nucleic acid; nucleotide
What is the term for the region of an enzyme where the substrate binds?
Allosteric site
Active site
Regulatory domain
Phosphorylation loop
For an enzyme-mediated reaction to occur, what must be compatible between the substrate and the active site?
Size and temperature
Shape and charge
pH and pressure
Concentration and volume
Which option best explains the enzyme-substrate complex model?
Substrates permanently change the enzyme’s primary structure.
The substrate temporarily binds to the enzyme’s active site to form a complex.
Enzymes only function after being consumed by the reaction.
The enzyme binds nonspecifically to any molecule nearby.
An enzyme has a positively charged amino acid at the center of its active site. What is the most likely effect if a mutation changes this residue to a negatively charged one?
Increased substrate binding due to stronger attraction
No change because charge does not affect binding
Loss of function because substrate charge compatibility is disrupted
The enzyme becomes a carbohydrate
If an enzyme’s shape is altered by mutation, what is the predicted outcome for its function?
Enhanced activity with any substrate
Substrate cannot fit into the active site, reducing or eliminating function
The enzyme gains the ability to replicate DNA
No effect on reaction rate
Which factor directly explains why enzymes can regulate biological processes by facilitating reactions?
They raise the activation energy required.
They lower the activation energy required.
They neutralize substrates before binding.
They permanently bond to products.
According to substrate specificity, which substrate would bind to the depicted enzyme’s active site? Refer to a diagram showing an active site shaped to fit a particular substrate.
A substrate with a very different shape from the active site
Any substrate if concentration is high enough
A substrate whose shape complements the active site
Only substrates with neutral charge regardless of shape
Which statement best defines activation energy in a chemical reaction?
The total energy released by the reaction
The amount of energy required for a chemical reaction to happen
The energy stored in the products
The energy that enzymes produce
In the straw-and-scissors analogy for an enzymatic reaction, what is the biological catalyst?
The straw pieces
The hand
The scissors
The tape
According to the energy diagrams, how does the presence of an enzyme affect activation energy and reaction rate?
It increases activation energy and slows the reaction
It decreases activation energy and speeds up the reaction
It has no effect on activation energy but speeds up the reaction
It increases activation energy and speeds up the reaction
Which part of the enzyme binds the substrate during catalysis?
Active site
Product site
Energy site
Binding pocket of the product
If you had to break straws by hand without scissors, what would happen to the reaction rate, and why?
Rate would increase because activation energy is lower
Rate would decrease because activation energy is higher
Rate would be unchanged because activation energy is the same
Rate would be random because activation energy varies
Identify the substrate and product in the straw analogy.
Substrate: two straw pieces; Product: one whole straw
Substrate: one plastic straw; Product: two pieces of straw (A and B)
Substrate: scissors; Product: straw pieces
Substrate: hand; Product: energy
Which graph represents a reaction without an enzyme?
The graph with a lower activation energy peak
The graph labeled 'With enzyme'
The graph showing a higher activation energy peak
Neither graph
What is the primary role of a biological catalyst in a reaction?
To become a product
To raise the energy of the products
To lower the activation energy and increase reaction speed
To supply energy to the substrate
In an energy diagram, where is activation energy indicated?
As the difference between substrate and product energies at the end
As the peak height that must be overcome for the reaction to proceed
As the area under the curve
As the final energy of the products
Which statement best describes enzyme denaturation?
A permanent increase in enzyme concentration
A change in enzyme structure due to temperature, pH, or chemical environment that eliminates catalytic ability
A temporary blockage of the active site by a competitive inhibitor
Formation of more hydrogen bonds to stabilize the enzyme
What happens to the substrate binding when an enzyme is denatured?
It binds more strongly to the active site
It no longer fits into the active site, so the reaction does not occur
It converts directly into product without enzyme assistance
It binds to an allosteric site to increase reaction rate
Which environmental factor disrupts the hydrogen bonds that help form the 3D shape of an enzyme, leading to lower reaction rates when outside the optimum?
Only low temperature
Only high pH
Both high temperature and high/low pH outside the optimum
Only substrate concentration
According to the material, what is the typical optimal temperature for enzymes in the human body?
72 degrees
37 degrees Celsius (98 degrees Fahrenheit)
25 degrees Celsius
100 degrees Celsius
Which graph trend best represents enzyme reaction rate versus temperature around the optimum?
A steady linear increase with temperature
A bell-shaped curve with peak at the optimum and lower rates at temperatures above or below it
A constant reaction rate regardless of temperature
A step function that jumps at the optimum
Which statement about pH effects on enzymes is accurate?
Enzyme activity increases indefinitely with pH
Activity is highest at the enzyme’s optimum pH and decreases at too acidic or too basic conditions
pH has no effect on enzyme structure
Only basic pH affects enzymes
Which bonds are primarily disrupted during denaturation that alters enzyme structure?
Covalent peptide bonds of the primary structure
Hydrogen bonds that stabilize the 3D shape
Ionic bonds in substrates
Metallic bonds
Is enzyme denaturation ever reversible, allowing the enzyme to regain activity?
No, denaturation is always irreversible
Yes, sometimes
Only at very high temperatures
Only in the presence of inhibitors
Which scenario would most likely cause an enzyme’s reaction rate to decrease due to denaturation?
Maintaining the enzyme at its optimum temperature
Exposing the enzyme to high temperature and extreme pH
Increasing substrate concentration at optimum pH
Adding a cofactor at optimum temperature
Catalase catalyzes the breakdown of hydrogen peroxide to water and oxygen (H2O2 → H2O + O2). Which direct measurement could indicate catalase reaction rate?
Decrease in enzyme mass
Increase in oxygen produced over time
Change in color of the solution unrelated to products
Number of substrates added
Which statement best describes how product concentration affects enzyme reaction rate over time?
The reaction rate increases because product stimulates the active site.
The reaction rate drops as product interferes with enzyme–substrate interactions.
The reaction rate remains constant because product does not affect enzymes.
The reaction rate increases because product becomes additional substrate.
As substrate concentration around an enzyme decreases over time, what is the expected impact on reaction rate?
Reaction rate increases due to reduced competition.
Reaction rate drops because there is less substrate for the reaction.
Reaction rate remains unchanged if temperature is optimal.
Reaction rate oscillates due to product feedback.
Which cellular strategy helps maintain a high reaction rate by managing product concentration?
Increase pH to denature enzymes.
Move product away from the area or use the product in another reaction.
Decrease substrate concentration to prevent saturation.
Add noncompetitive inhibitors to stabilize enzymes.
Which cellular strategy helps maintain a high reaction rate in terms of substrate availability?
Dilute the substrate throughout the cell.
Compartmentalize the reaction to concentrate substrate near the enzyme.
Remove products to inhibit feedback.
Bind inhibitors to the active site.
Which statement correctly distinguishes competitive and noncompetitive (allosteric) inhibitors?
Competitive inhibitors bind allosteric sites; noncompetitive inhibitors bind the active site.
Competitive inhibitors irreversibly denature enzymes; noncompetitive inhibitors are reversible.
Competitive inhibitors bind directly to the active site; noncompetitive inhibitors bind allosteric sites causing a change in the shape of the active site.
Both inhibitors increase substrate binding affinity at the active site.
Where do competitive inhibitors bind, and what immediate effect does this have?
Allosteric site; increases product formation.
Active site; prevents substrate from binding.
Active site; accelerates enzyme turnover.
Allosteric site; prevents product release.
According to Essential Knowledge 3.2.B.2, how do higher environmental temperatures generally affect enzymatic reactions in solution?
They decrease molecular movement, lowering collision frequency.
They increase average molecule movement and enzyme–substrate collision frequency until optimal temperature is reached.
They immediately denature all enzymes regardless of temperature.
They have no effect on reaction rate.
Noncompetitive inhibitors bind allosteric sites. What is the consequence of this binding on the enzyme’s active site?
No change occurs; substrate still binds normally.
The active site changes shape, altering enzyme activity.
The active site is duplicated, increasing activity.
The enzyme is transported to another compartment.
Which statement best describes the first law of thermodynamics in biological systems?
Energy can be created by cells when needed
Energy cannot be created or destroyed; it can be transformed from one form to another
Entropy of a system always decreases during metabolism
Energy is only stored in ATP and cannot be transferred
What is the second law of thermodynamics as it applies to living systems?
Energy transformations increase the system's entropy
Energy is perfectly conserved without loss
Entropy decreases when matter moves
Cells can eliminate entropy entirely
Why is a continual input of energy necessary for living organisms to maintain homeostasis?
To decrease entropy below zero
To power cellular processes and prevent the system from moving toward disorder
To increase heat within cells for stability
To store unlimited glucose
According to the instructional material, what happens when organisms obtain less energy than required to stay alive?
They grow faster
They enter a reversible dormancy
They die due to loss of order outweighing energy input
They become more efficient at energy use without consequence
Which pairing correctly illustrates energy coupling in cells?
Photosynthesis coupled to fermentation
ATP formation coupled to processes that require energy
Glycolysis coupled to decreasing entropy
Oxidative phosphorylation coupled to energy loss only
In cellular respiration, which statement is accurate based on the material?
Respiration builds glucose to store energy
Respiration breaks down glucose to release energy
Respiration converts radiant energy directly into ATP
Respiration decreases entropy of the universe
What is the ultimate source of energy for Earth mentioned in the material?
Geothermal vents
Chemical bonds in glucose
The sun
Earth's magnetic field
What do photoautotrophs do with the energy they receive from the sun?
Use it in photosynthesis to make glucose
Use it to increase cellular entropy
Use it to combust ATP directly
Use it to power glycolysis only
Why are glycolysis and oxidative phosphorylation described as "highly conserved" across all domains of life, and what does this imply about evolution?
They evolved independently in each lineage; implies frequent reinvention
They are found across life forms largely unchanged; implies early origin and inheritance from a common ancestor
They are unique to eukaryotes; implies recent evolution
They only occur in bacteria; implies horizontal transfer only
Which equation best represents photosynthesis as presented, including reactants and products powered by sunlight?
6CO2 + 6H2O —sun→ C6H12O6 + 6O2
C6H12O6 + 6O2 —sun→ 6CO2 + 6H2O
6O2 + C6H12O6 —sun→ 6CO2 + 6H2O
6CO2 + 6O2 —sun→ C6H12O6 + 6H2O
What is stored in a glucose molecule produced by photosynthesis?
Genetic information
Energy
Nitrogen
Iron
According to the material, in which type of organisms did photosynthesis first evolve?
Eukaryotic plant cells
Animals
Prokaryotic organisms
Fungi
Which statement best explains how cyanobacteria impacted early Earth?
They removed oxygen from the atmosphere, preventing iron oxidation.
They generated oxygen as a waste product, increasing atmospheric oxygen.
They produced methane that rusted iron in oceans.
They consumed sunlight, reducing oxygen levels.
What do banded iron formations indicate about ancient oceans, and how did they form according to the text?
Oceans lacked iron; bands formed from volcanic ash.
Oceans had dissolved iron; oxygen from cyanobacteria oxidized iron causing it to sink and form bands.
Oceans were rich in oxygen; iron bands formed from tidal action.
Oceans had no microbes; iron bands formed by evaporation.
Which theory explains the origin of chloroplasts in eukaryotic plant cells?
Chemiosmotic theory
Fluid mosaic theory
Endosymbiotic theory
Gene flow theory
Which statement about the relationship between prokaryotic photosynthetic pathways and eukaryotic photosynthesis is supported by the material?
Eukaryotic photosynthesis evolved independently and shares no features with prokaryotes.
Prokaryotic photosynthetic pathways were the foundation of eukaryotic photosynthesis.
Eukaryotes created prokaryotic photosynthesis through horizontal gene transfer.
Prokaryotic photosynthesis was derived from plant chloroplasts.
Where is the stroma located within a chloroplast, according to the description?
Inside the thylakoid lumen
Between the outer chloroplast membrane and the cell wall
The fluid within the inner chloroplast membrane and outside the thylakoid
Embedded within the grana
In the simple chloroplast diagram, which structures should be labeled in addition to the stroma?
Mitochondria and nucleus
Thylakoid and grana
Cell wall and plasma membrane
Ribosome and centriole
Which location within the chloroplast is the site of the Calvin cycle (light-independent reactions)?
Thylakoid lumen
Thylakoid membrane
Stroma
Grana
In the light-dependent reactions of photosynthesis, where are chlorophyll pigments and electron transport proteins organized?
Mitochondrial cristae
Thylakoid membranes within grana
Stroma matrix
Cytosol
Which outputs are produced by the light-dependent reactions?
Glucose, CO2, NAD+
Oxygen, ATP, NADPH
Water, ADP, NADP+
Pyruvate, ATP, FADH2
Photophosphorylation in chloroplasts directly results in the formation of which molecule?
ADP
ATP
NADP+
Glucose
During photosynthesis, water splitting at the start of the ETC provides which component?
Electrons to replace those lost from photosystem II
Carbon dioxide for Calvin cycle
Protons to neutralize the stroma
Oxygen to reduce NADP+
How many photons are needed to move one electron all the way through the photosynthetic ETC?
One photon hitting PSII
Two photons: one hits PSI and one hits PSII
Three photons: two PSI and one PSII
Four photons: two PSI and two PSII
Movement of electrons through the ETC pumps H+ into which space, making it more acidic?
Stroma
Thylakoid lumen
Cytosol
Intermembrane space
What is the final electron acceptor in the photosynthetic ETC?
O2 forming water
NADH
NADP+ becomes NADPH
FAD
As electrons are passed along the ETC, the molecule that loses the electron is described as being what?
Reduced
Oxidized
Hydrolyzed
Phosphorylated
What is the role of ATP synthase during the light reactions?
Oxidizes NADPH to produce NADP+
Allows H+ to flow to generate ATP from ADP + P
Splits water to provide electrons
Pumps protons into the stroma
Where do ATP and NADPH go after being produced by the light-dependent reactions?
Back to photosystem II
Into the Calvin cycle
Exported out of the chloroplast
Used to split more water
What is the purpose of ATP and NADPH produced in the light reactions?
Store energy to power the Calvin cycle
Provide electrons to PSII
Produce oxygen
Fix carbon directly into glucose
Doubling the number of thylakoids in a chloroplast would most directly increase which outcome?
Rate of CO2 diffusion into the stroma
Production of glucose via more ETC enzymes contributing to Calvin cycle
Amount of water entering the chloroplast
Number of ribosomes in the stroma
Which statement best describes thylakoids and grana?
Thylakoids are membrane sacs arranged in stacks called grana
Grana are stroma-filled spaces within the inner membrane
Thylakoids are cytosolic vesicles with DNA
Grana are protein complexes embedded in PSI
During the light reactions, what happens to O2 generated from water splitting?
It becomes part of glucose
It is released into the air
It remains dissolved in the stroma to reduce NADP+
It enters PSI as an electron donor
Which photosystem’s pigments re-energize electrons after they pass through part of the ETC?
Photosystem I
Photosystem II
Cytochrome c
ATP synthase
What is the membrane that embeds photosystems I and II and connects them via the ETC?
Inner mitochondrial membrane
Nuclear envelope
Thylakoid membrane
Plasma membrane
Establishment of an electrochemical gradient of protons across the thylakoid membrane separates which regions?
Cytosol from nucleus
Stroma (low H+) from thylakoid lumen (high H+)
Mitochondrial matrix from intermembrane space
Grana from stroma
Which balanced overall equation best represents aerobic cellular respiration in eukaryotes?
Glucose + 6 Oxygen → 6 Water + 6 Carbon Dioxide + ATP
Glucose + Oxygen → Alcohol + Carbon Dioxide + ATP
6 Carbon Dioxide + 6 Water → Glucose + Oxygen + ATP
Glucose → Lactic Acid + ATP
In a eukaryotic cell, the majority of cellular respiration occurs in which organelle?
Chloroplast
Mitochondria
Golgi apparatus
Nucleus
Which statement correctly describes the role of the electron transport chain (ETC) in cellular respiration?
It breaks glucose into two pyruvate molecules.
It transfers electrons from NADH and FADH2 to oxygen and helps create a proton gradient across the inner mitochondrial membrane.
It converts carbon dioxide into sugars.
It directly produces glucose from ATP.
During cellular respiration, what is the terminal electron acceptor in aerobic organisms?
NAD+
FAD
Oxygen
Carbon dioxide
What structural feature of mitochondria increases ATP production efficiency by creating more surface area for the ETC?
Outer membrane pores
Cristae (folding of the inner membrane)
Matrix granules
Smooth outer membrane
A patient’s mitochondria resemble diagram A (smooth inner membrane) rather than diagram B (highly folded). Which symptom is most likely and why?
High energy levels due to more membranes
Very tired, low energy because less inner membrane surface area reduces ATP production
Elevated oxygen levels because ETC stops using oxygen
Increased glucose storage due to excess ATP
Where does glycolysis occur in the cell?
Mitochondrial matrix
Inner mitochondrial membrane
Cytosol
Intermembrane space
Glycolysis begins with glucose and produces which immediate end product(s)?
Acetyl-CoA only
Two pyruvate molecules, ATP, and NADH
Carbon dioxide and water
Lactate and ethanol
What is the primary use of the energy released from glucose during cellular respiration according to the material?
To make sucrose
To power photosynthesis
To make molecules of ATP
To produce GA3P
Which molecules deliver electrons to the ETC in cellular respiration?
ATP and ADP
NADH and FADH2
CO2 and H2O
Glucose and oxygen
In the context of aerobic respiration, where does pyruvate go after glycolysis and what is its purpose?
It stays in the cytosol to accept electrons.
It enters the mitochondrion to be oxidized further, contributing to the Krebs cycle and ETC.
It is excreted from the cell.
It becomes GA3P for the Calvin cycle.
Which statement best explains why chemiosmosis in mitochondria is essential for ATP synthesis?
It uses light to directly make ATP.
The proton gradient across the inner membrane drives ATP synthase to convert ADP and inorganic phosphate into ATP.
It splits glucose into two molecules.
It transports oxygen into the matrix.
Which statement best describes the general purpose of the Krebs cycle in cellular respiration?
To directly synthesize the majority of ATP
To make high-energy molecules to be passed to the electron transport chain (ETC)
To break down ATP into ADP and phosphate
To pump protons across the outer mitochondrial membrane
Which set lists three important molecules made during the Krebs cycle according to the material?
ATP, NADH2, FADH
FADH2, ATP, NADH2
CO2, H2O, ATP
Glucose, NADH, Pyruvate
Where do NADH2 and FADH2 go after being produced in the Krebs cycle, and what do they carry?
To the cytosol carrying protons
To ATP synthase carrying oxygen
To the electron transport chain carrying electrons
Remain in the Krebs cycle carrying carbon dioxide
What waste product is released during the Krebs cycle that plants utilize?
Water
Carbon dioxide
Oxygen
Ammonia
As electrons are transferred down the ETC, H+ ions are pumped into which space of the mitochondria, establishing an electrochemical gradient?
Mitochondrial matrix
Intermembrane space
Outer membrane
Cytosol
What is the final electron acceptor at the end of the electron transport chain?
NAD+
FAD
Water
Oxygen
Protons flow back across the inner mitochondrial membrane through which enzyme?
ATP synthase
Hexokinase
Rubisco
DNA polymerase
In the context of membrane transport, chemiosmosis is best described as which type of process?
Active transport using ATP directly
Facilitated diffusion driven by a proton gradient
Simple diffusion of electrons
Endocytosis of glucose
The process of making ATP by joining ADP and inorganic phosphate as protons flow through ATP synthase is called what?
Substrate-level phosphorylation
Oxidative phosphorylation
Photophosphorylation
Glycolysis
According to the table, how many net ATP per glucose are made by the electron transport chain via oxidative phosphorylation?
2
4 (total, two are used)
32
36
During glycolysis, what type of phosphorylation occurs and how many net ATP per glucose are produced?
Oxidative; 32
Substrate-level; 4 total, two are used
Substrate-level; 2
Oxidative; 2
Which statement correctly matches the cellular respiration process with its phosphorylation type?
Krebs cycle — Oxidative
Electron transport chain — Substrate level
Glycolysis — Oxidative
Krebs cycle — Substrate level
What does phosphorylation mean in simple terms, as stated in the material?
To remove a phosphate from a molecule
To add a phosphate to a molecule
To oxidize glucose
To reduce oxygen
Which molecules are identified as key terms associated with the electron transport chain and oxidative phosphorylation in the material?
Oxygen, Water, ATP synthase, Chemiosmosis, Oxidative phosphorylation
Glucose, Pyruvate, Rubisco, NADPH
Carbon dioxide, Chlorophyll, Thylakoid, Stroma
Lactate, Fermentation, Cytoskeleton, Actin
According to the essential knowledge, where does the Krebs cycle take place within the mitochondrion?
Intermembrane space
Inner membrane
Mitochondrial matrix
Outer membrane
What is broken in ATP to release energy for cellular processes, as indicated by the diagram prompt?
The bond between ribose and adenine
The bond between the ADP and the phosphate (P)
The hydrogen bond with water
The peptide bond between amino acids
Which statement best describes fermentation in cellular respiration?
It requires oxygen and produces high ATP yields.
It does not require oxygen and produces organic molecules such as alcohol and lactic acid.
It uses oxygen as the final electron acceptor in the electron transport chain.
It only occurs in mitochondria of eukaryotic cells.
What is the defining difference between aerobic and anaerobic respiration?
Aerobic respiration does not use oxygen; anaerobic uses oxygen.
Aerobic respiration uses oxygen as a final electron acceptor in an ETC; anaerobic does not use oxygen.
Both use oxygen but at different points in glycolysis.
Anaerobic respiration yields more ATP than aerobic.
Which process generally makes more ATP?
Anaerobic respiration
Glycolysis
Aerobic respiration
Fermentation
Yeast primarily perform which type of fermentation, and what are the products?
Lactic acid fermentation producing lactic acid only
Alcoholic fermentation producing ethanol and CO2
Alcoholic fermentation producing lactic acid and ATP
Lactic acid fermentation producing ethanol and CO2
Humans primarily use which type of fermentation under low-oxygen conditions, and what is the product?
Alcoholic fermentation; ethanol
Lactic acid fermentation; lactic acid
Aerobic respiration; CO2
Anaerobic respiration; ATP
During fermentation, why is the conversion of pyruvate to lactic acid or alcohol essential for glycolysis to continue?
It generates additional ATP directly.
It regenerates NAD+ from NADH, allowing glycolysis to continue.
It increases oxygen availability.
It forms a proton gradient for the ETC in mitochondria.
Is it possible for anaerobic prokaryotes to use an electron transport chain (ETC)?
No, ETC requires oxygen and mitochondria.
Yes; some use molecules other than oxygen as a final electron acceptor, but they generally produce less ATP than aerobic respiration.
Yes; they use chloroplasts to establish a proton gradient.
No; fermentation replaces all ETC functions.
Prokaryotes do not have mitochondria or chloroplasts. How can they establish a proton gradient to make ATP?
By using membrane-bound organelles.
By utilizing infolding of their cell membranes.
By relying on chloroplast thylakoids.
By storing protons in the nucleus.
