EnzymesUnit 2, lesson 4

Enzymes

A type of protein Function as catalysts- substances

that speed up chemical reactions Enzymes are not changed or used up

by the reactions They lower the activation energy

required to make chemical reactions happen.

Chemical Reactions

Reactants Products

Reactants are the starting ingredients

Products are what you get after the reaction happens

Enzyme Specificity

We have thousands of enzymes in our body

Each enzyme only works for ONE specific chemical reaction

The shape of the enzyme has to match a specific substrate (the molecule that the enzyme helps to react)

An enzyme has an active site that has to fit with the shape of the substrate

Enzyme Specificity

(Reactant)

Conditions that affect enzymes Each enzyme has a specific

temperature and pH at which it works best

If these conditions change, the enzyme won’t work as well (and may not work at all) because it’s shape and structure will change

Concentration (how much there is) Reaction rates can be affected by

the concentration of the enzyme itself AND the concentration of the substrate.

Your Turn…

Workbook pages 52-54, # 1-5

#1

Which is NOT a structural feature of an enzyme?B - A substrate is the other molecule to which an enzyme binds

Enzymes are proteins made from a chain of amino acids. They have active sites where they bind to another molecule.

#2

Which statement describes the reaction?

D- oxygen is a product of the reaction

Water is a product Hydrogen peroxide is the

substrate/reactant Enzymes are NOT consumed by

reactions, and catalase is an enzyme

#3

Which describes how the concentrations of these substances will change?

C – There will be more galactose (reactant) and the amount of lactase (enzyme) will not change

Lactase = enzyme (doesn’t change) Lactose = substrate (less) Glucose and galactose = products (more)

#4

Which of the following will NOT affect the rate of the reaction?

D - increasing the substrate concentration

More substrate doesn’t matter if there isn’t enough enzyme to bind with it. Temperature and pH always matter.

#5 A

What does the graph indicate about the pH of the stomach and small intestine?

Pepsin works in the stomach, so it probably has a pH close to 3

Trypsin works in the small intestine, so it probably has a pH near 7

#5B

The contents of the stomach are released into the small intestine. How does this affect the function of pepsin included with the stomach contents? Since the small intestine is more acidic,

pepsin won’t work anymore and will become denatured

#5 C

What is the advantage to having two different protein-digesting enzymes instead of just one? The advantage is that now at least one

enzyme is working in both parts of the digestive tract, so the body has more time to completely break down the protein in food