Enzymes are mostly protein biological catalysts, with some RNA examples. They speed up reactions in small amounts and remain unchanged after catalysis, so cells can run reactions quickly without using up the enzyme.

Enzymes are biological catalysts

They are effective in small amounts

They remain unchanged after the reaction.

Which statement best describes an enzyme catalyst?

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Metabolism is all enzyme-controlled chemical reactions in cells. Specific enzymes control which metabolic reactions occur and when, so metabolism is not random chemistry; it is coordinated pathway control.

Metabolism includes all enzyme-controlled reactions in a cell or organism.

Different enzymes control different pathway steps.

Controlling enzymes controls metabolic output.

Which is the best definition of metabolism?

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Metabolism includes anabolism and catabolism. Anabolism builds complex molecules from smaller ones, often by condensation, and requires energy. Catabolism breaks molecules down by hydrolysis or oxidation and releases energy.

Anabolism builds and requires energy.

Catabolism breaks down and releases energy.

Metabolism includes both anabolic and catabolic reactions.

Sort each reaction clue.

Sort

Enzymes are usually globular proteins with a small active-site pocket. The active site binds the substrate, forms an enzyme-substrate complex, and catalyses the reaction. Active-site shape and chemistry are why enzymes are specific.

Enzymes are usually globular proteins.

The active site is a small pocket that binds substrate.

The enzyme-substrate complex positions the substrate for catalysis.

The folded protein creates the pocket that does the chemistry.

Which statement best links active site to function?

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Which statement best links active site to function?

Choose

In induced fit, substrate binding causes shape changes in both enzyme and substrate. This aligns catalytic groups and raises the substrate toward the transition state, making reaction more likely.

Induced fit is not a rigid lock-and-key fit.

Binding changes shape in enzyme and substrate.

The changed fit helps reach the transition state.

Binding helps create the best catalytic fit rather than matching a rigid template from the start.

Order induced-fit catalysis.

Order

1

catalytic groups align

2

substrate begins to bind

3

enzyme and substrate change shape

4

substrate collides with active site

5

transition state is stabilized and products form

Order induced-fit catalysis.

Choose

substrate collides with active site

substrate begins to bind

enzyme and substrate change shape

catalytic groups align

transition state is stabilized and products form

Molecular motion brings substrates and active sites into collision. Higher kinetic energy can increase successful active-site collisions, but only up to the point where enzyme structure remains intact.

Substrate and enzyme must collide for catalysis.

Higher kinetic energy increases collision frequency.

Too much heat can denature enzyme structure.

Why can a moderate temperature rise increase enzyme reaction rate?

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Active-site amino acid arrangement determines substrate specificity. Denaturation changes tertiary structure and active-site shape, reducing activity; it does not usually break peptide bonds in the primary structure.

Specificity depends on active-site amino acid arrangement.

Denaturation changes tertiary structure and active-site shape.

Peptide bonds are not the usual target of denaturation in enzyme questions.

What usually happens when an enzyme is denatured?

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Temperature, pH, and substrate concentration change enzyme activity in different ways. Temperature increases rate to an optimum, then denaturation lowers activity. pH changes bonding in the active site. Substrate concentration increases rate until active sites are saturated and the curve plateaus.

Temperature curve rises to an optimum then falls with denaturation.

pH changes active-site bonding and each enzyme has an optimum pH.

Substrate concentration gives a saturation plateau when active sites are occupied.

The graph shape tells you the mechanism.

Match each curve pattern to its mechanism.

Match

Reasons

0/4

Match each curve pattern to its mechanism.

Choose

temperature rises to optimum

temperature falls after optimum

pH away from optimum

substrate plateau

Enzyme reaction rate can be measured by substrate loss or product formation per unit time. Good assays use initial rate, replicates, controls, and graphs. Examples include amylase assays tracking starch loss or catalase assays tracking oxygen production.

Measure rate as change per unit time.

Initial rate is preferred before substrate depletion or product buildup distorts the rate.

Replicates and controls make data reliable.

Sort each assay feature by purpose.

Sort

Enzymes lower activation energy by providing an alternative pathway and stabilizing the transition state. They do not remove the energy barrier completely, and they do not change the overall energy difference between reactants and products.

Activation energy is the energy barrier to reaction.

Enzymes lower activation energy through an alternative pathway.

The transition state is stabilized, but the enzyme remains unchanged after catalysis.

The enzyme changes the route, not the starting and ending energy levels.

What does an enzyme change on an energy profile?

Choose

What does an enzyme change on an energy profile?

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Enzymes are biological catalysts that lower activation energy and remain unchanged. Their globular protein shape creates active-site specificity; induced fit aligns substrates; molecular motion and collisions affect rate; temperature, pH, and substrate concentration change activity; assays measure substrate loss or product formation over time.

Define enzyme as biological catalyst, effective in small amounts and unchanged.

Use active site, specificity, induced fit, ES complex, and activation energy in mechanism answers.

Use curve shapes: temperature optimum/denaturation, pH optimum, and substrate saturation plateau.

For practicals, state what is measured per unit time and use initial rate, controls, and replicates.

Fill Blanks

Complete the skeleton: Enzymes lowerenergy. Theirsite binds a specific substrate. Temperature has anbefore denaturation. Substrate concentration eventually reaches awhen active sites are saturated.

Word bank

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Use this for core questions on enzyme definition, metabolism, active sites, induced fit, rate curves, enzyme assays, and activation energy.

Enzymes are mostly protein biological catalysts, effective in small amounts and unchanged after catalysis.

Metabolism is all enzyme-controlled reactions; anabolism builds molecules and uses energy, while catabolism breaks molecules down and releases energy.

Enzymes are usually globular proteins with active sites that bind substrates, form enzyme-substrate complexes, and create specificity.

Induced fit changes enzyme/substrate shape, aligns catalytic groups, and helps reach the transition state.

Temperature, pH, and substrate concentration affect enzyme activity through collisions, denaturation, bonding changes, and active-site saturation.

Enzyme reactions are measured by substrate loss or product formation per unit time, ideally using initial rate, controls, and replicates.

Enzymes lower activation energy by providing an alternative pathway and stabilizing the transition state.

Use this for core questions on enzyme definition, metabolism, active sites, induced fit, rate curves, enzyme assays, and activation energy.

Do not write isolated enzyme terms without explaining active-site shape, activation energy, or rate mechanism.

IB Biology SL C1.1 Enzymes and metabolism Notes

Recognize an Enzyme Catalyst

Define Metabolism

Sort Anabolism and Catabolism

Inspect an Active Site

Explain Induced Fit

Predict Collision Rate

Link Shape to Specificity

Read Enzyme Rate Curves

Plan an Enzyme Assay

Compare Activation Energy

SL Transfer: Explain Enzyme Catalysis And Rate