Enzymes Flashcards

Questions and Answers

What are enzymes?

Proteins which speed up the rate of chemical reactions by acting as biological catalysts.

What term is used to describe an enzyme that acts outside cells?

Extracellular

What is the activation energy of a chemical reaction?

A certain amount of energy that needs to be supplied to the chemicals before the reaction will start.

How do enzymes affect the activation energy?

Enzymes lower the activation energy needed, making reactions happen at a lower temperature. Signup and view all the answers

What is a catalyst?

A substance which speeds up a chemical reaction without being used up in the reaction itself. Signup and view all the answers

Which line shows a reaction with the presence of an enzyme?

B Signup and view all the answers

What does the line labelled X represent?

The activation energy needed for the reaction with the presence of an enzyme. Signup and view all the answers

What is the main difference between the lock and key model and the induced fit model?

In the lock and key model, the active site has a fixed shape that is complementary to the substrate; in the induced fit model, the active site changes shape slightly to allow the substrate to bind tightly. Signup and view all the answers

What determines the shape of an enzyme's active site?

It's tertiary structure. Signup and view all the answers

Why will an enzyme only bind with one substrate?

An enzyme can only bind with a substrate which has a complementary shape to its active site. Signup and view all the answers

What is the enzyme's tertiary structure determined by?

It's primary structure. Signup and view all the answers

How does the formation of an enzyme-substrate complex lower the activation energy?

<ol> <li>If two substrate molecules need to be joined, being attached to an enzyme holds them closer together, reducing any repulsion. 2. If the enzyme is catalyzing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate.</li> </ol> Signup and view all the answers

Name the two ways you could measure enzyme activity.

<ol> <li>How fast the product is produced 2. How fast the substrate is broken down.</li> </ol> Signup and view all the answers

Explain why an increase in temperature increases the rate of enzyme activity.

More heat means more kinetic energy, so molecules move faster. This makes substrate molecules more likely to collide with the enzyme's active sites. Signup and view all the answers

Explain how a very high temperature can stop an enzyme from working.

Temperature increase makes the enzyme's molecules vibrate more, breaking bonds that hold the enzyme's shape. The active site changes shape and the enzyme is denatured. Signup and view all the answers

What happens to an enzyme's shape and function when it is denatured?

The bonds holding the enzyme in shape are broken, altering the active site shape, and the enzyme can't catalyze the reaction. Signup and view all the answers

Give two factors which can denature an enzyme.

<ol> <li>Temperature 2. pH</li> </ol> Signup and view all the answers

What is meant by the 'saturation point' in an enzyme-controlled reaction?

When all active sites are occupied. Signup and view all the answers

Explain what happens in an enzyme-controlled reaction when the substrate concentration is increased after the saturation point.

The rate of reaction stays constant as all active sites are occupied. Signup and view all the answers

Explain the effect of increasing the enzyme concentration on the rate of an enzyme-controlled reaction.

Increasing enzyme concentration increases reaction rate until substrate is limited; then adding more enzyme makes no difference. Signup and view all the answers

Where does a non-competitive inhibitor bind to an enzyme?

Bind away from the enzyme's active site. Signup and view all the answers

Where does a competitive inhibitor bind to an enzyme?

Bind to the enzyme's active site. Signup and view all the answers

Explain how non-competitive inhibition prevents enzyme activity.

A non-competitive inhibitor binds away from the active site, altering its shape so substrates cannot bind. Signup and view all the answers

How do the relative concentrations of the inhibitor and substrate affect how much the enzyme is inhibited?

A higher concentration of inhibitor compared to substrate means fewer substrate molecules will reach the enzyme, reducing activity. Signup and view all the answers

How do competitive inhibitors prevent enzyme activity?

They have a similar shape to substrate molecules and compete for binding to the active site. Signup and view all the answers

Study Notes

Enzymes Overview

Enzymes are proteins that act as biological catalysts, speeding up chemical reactions.
They work by lowering the activation energy required for reactions to occur.

Enzyme Locations and Types

Extracellular enzymes function outside of cells.

Activation Energy

Activation energy is the energy needed to start a chemical reaction.
Enzymes significantly lower this energy, allowing reactions to occur at lower temperatures.

Catalysts

A catalyst accelerates a chemical reaction without being consumed in the process.

Enzyme Models

The lock and key model has a fixed active site shape, while the induced fit model involves a slight shape change in the active site to accommodate the substrate.

Active Site and Structure

An enzyme's active site shape is determined by its tertiary structure, which in turn is defined by its primary structure (sequence of amino acids).
Enzymes can only bind with substrates that fit their active site shape, ensuring specificity.

Enzyme-Substrate Complex

The formation of an enzyme-substrate complex decreases activation energy in two ways:
- Holding two substrates close reduces repulsion, facilitating bonding.
- Straining substrate bonds makes them easier to break in breakdown reactions.

Measuring Enzyme Activity

Enzyme activity can be measured by the rate of product formation or the rate of substrate breakdown.

Temperature Effects on Enzymes

Increased temperature results in higher kinetic energy, leading to more frequent successful collisions between substrate and active sites.
Extreme temperatures can lead to denaturation, as bonds that maintain enzyme shape break, altering the active site.

Denaturation and Factors

Factors that can denature enzymes include high temperature and unfavorable pH levels.
Denaturation results in loss of the enzyme's functional shape, preventing substrate binding.

Saturation Point

The saturation point occurs when all active sites on the enzyme are occupied, rendering further substrate increases ineffective.

Enzyme Concentration Effects

Increasing enzyme concentration raises reaction rates until substrate becomes limiting, after which additional enzymes have no effect.

Inhibition Mechanisms

Non-competitive inhibitors bind away from the active site, altering its shape and preventing substrate binding.
Competitive inhibitors resemble substrates, competing for the active site and blocking substrate access.

Inhibitor Concentration Effects

Higher inhibitor concentrations than substrate thwart reaction by occupying active sites.
Conversely, when substrate concentration exceeds that of the inhibitor, the likelihood of substrate binding to the active site increases.

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Description

Test your knowledge of enzymes with these flashcards. Each card presents a key concept, from the definition of enzymes to activation energy and extracellular enzymes. Perfect for students learning about biochemistry and biology.