C1.1 Enzymes and Metabolism Review (IB Bio SL)

IB definition of metabolism

The complex network of interdependent and interacting chemical reactions occurring in living organisms through the use of enzymes (Simplified: All enzyme catalyzed reactions

Enzyme

A substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction

Catalyst

A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change

Why are enzymes necessary?

All chemical reactions require some amount of activation energy to react the activation energy without enzymes would be more than the organism can supply enzymes work to lower this activation energy to one that the organism can provide

Need to be able to interpret this graph

Catalysis

The acceleration of a chemical reaction by a catalyst

What type of protein are enzymes?

Globular protein (meaning that is is roughly globe-shaped)

Structure of enzymes

Enzymes are globular proteins with an active site for catalysis. The active site is a small handful of amino acids that directly bind to the substrate (the overall structure affects binding though)

Substrate

A specific reactant (what is put in) acted upon by an enzyme

Induced fit model

Both the enzyme and the substrate change shape when binding occurs

Anabolic reaction

Any condensation reaction that forms polymers

Examples of anabolic reactions

Protein synthesis, glycogen formation, photosynthesis

Catabolic reaction

Any hydrolysis reaction that breaks down macromolecules into monomers

Examples of catabolic reactions

Digestion, oxidation in respiration

What must happen in order for a reaction to occur between a substrate and enzyme?

They must collide

How does temperature affect the likelihood of a reaction between an enzyme and substrate?

Temperature is the speed of molecules, so the higher the temperature, the faster molecules are moving. The faster the molecules are moving, the more likely they are to collide

How can the likelihood of a collision between an enzyme and substrate increase?

• Increase the temperature

• Embed either the enzyme or substrate into a membrane and lock it in place

How to measure the rate of reaction in an enzyme-catalyzed reaction

Use the rate of reaction equation: Rate of reaction = change in concentration of substance over time Rate = ΔB/Δt = -ΔA/Δt

Reactants go down, products go up

Factors that affect enzyme activity

Substrate concentration, pH, and temperature

Temperature vs. enzyme activity

As temperature increases, enzyme activity linearly increases, then sharply declines as enzymes denature past the optimum temperature (Only higher temperatures cause denaturation, lower temperatures simply cause the enzyme to move slower)

pH vs. enzyme activity

Enzymes denature on both sides of the optimum

Substrate concentration on enzyme activity

As substrate concentration increases, enzyme activity rapidly increases, then plateaus once all enzymes are being used

Relationship between structure of active site, enzyme-substrate specificity, and denaturation

Enzymes are shaped specifically for their substrate, so if an enzyme denatures (changes shape), it no longer works