Unit 2: Section 3 - Enzymes

Question 1

<p>The sum of all the chemical reactions in the body is called the...</p>

Answer 1

<p>Metabolism</p>

Question 2

<p>Enzymes that speed up reactions where molecules are broken down are called...</p>

Answer 2

<p>Catabolic reactions</p>

Question 3

<p>Enzymes that build up large molecules from smaller ones are called...</p>

Answer 3

<p>Anabolic reactions</p>

Question 4

<p>What do extracellular enzymes do</p>

Answer 4

<p>Break down large molecules outside the cell into smaller, soluble molecules that can be absorbed</p>

Question 5

<p>What is activation energy</p>

Answer 5

<p>The energy needed to break the bonds in the substrate and start the reaction</p>

Question 6

<p>what is an exergonic/endogonic reaction</p>

Answer 6

<p>Energy is released/energy is absorbed</p>

Question 7

<p>How is an enzyme substrate formed</p>

Answer 7

<p>Because the enzyme and substrate molecules are constantly moving they frequently collide, if a substrate fits into an active site, it is held there for a brief moment, causing an enzyme substrate complex to form.`</p>

Question 8

<p>What happens in the induced fit model</p>

Answer 8

<p>R groups on the polypeptide forming the active site move to form temporary bonds with the substrate molecule.</p>

Question 9

<p>why do enzymes speed up catabolic reactions</p>

Answer 9

<p>Because when a substrate is in an active site in puts a strain on the bonds meaning that they will be easier to break</p>

Question 10

<p>why do enzymes speed up anabolic reactions</p>

Answer 10

<p>Because when 2 substrate molecules need to be joined, attaching them to an enzyme holds them together, reducing any repulsion between them, so they can join together easier.</p>

Question 11

<p>4 factors affecting enzyme activity</p>

Answer 11

<p>Temperature
pH
Substrate concentration
Enzyme concentration</p>

Question 12

<p>Explain how temperature affects enzyme activity </p>

Answer 12

<p>Low temperatures - The molecules have low kinetic energy meaning fewer collisions will occur resulting in a lower rate of reaction

Optimum - At optimum temperature the rate of reaction is at its highest

High temperatures - at temperatures above the optimum the enzyme will start to denature (lose its tertiary structure and lose its active sites shape), this means fewer enzyme-substrate complexes will form so a lower ROR. Eventually the tertiary structure will denature completely and there will be no enzyme activity.</p>

Question 13

<p>Explain how substrate concentration affects enzyme activity</p>

Answer 13

<p>At lower substrate concentrations rate of reaction will be lower as there will be fewer substrate molecules available to form enzyme substrate complexes. As substrate concentration increases so does ROR. However when substrate concentration reaches a certain level all the active sites will be filled meaning that rate of reaction will stop increasing.</p>

Question 14

<p>Explain how enzyme concentration affects enzyme activity</p>

Answer 14

<p>As enzyme concentration increases so does ROR when there are plenty of substrate molecules.</p>

Question 15

<p>Explain how pH affects enzyme activity</p>

Answer 15

<p>Most enzymes work at narrow pH ranges (they don't work at a wide range either side of their optimum). Their optimum pH depends on where they are, e.g. pepsin works in the stomach where hydrochloric acid is secreted and has a very low optimum pH of about 2. </p>

Question 16

<p>What happens when the pH changes from its optimum</p>

Answer 16

<p>The shape of the enzyme changes

The affinity of the substrate for the active site decreases</p>

Question 17

<p>What is a cofactor</p>

Answer 17

<p>A non protein component of an enzyme required by enzymes to carry out reactions</p>

Question 18

<p>What is a coenzyme</p>

Answer 18

<p>An organic cofactor, involved in the energy transfer reactions of respiration and photosynthesis, can be tightly bound to their enzyme or mobile.</p>

Question 19

<p>What is a competitive inhibitor</p>

Answer 19

<p>Molecular shape is similar to the substrate, so it fits into the active site, slowing rate of reaction</p>

Question 20

<p>What is a non competitive inhibitor</p>

Answer 20

<p>Molecule binds to a part of the enzyme that is not the active site, this changes the enzymes active site shape, so the substrate can no longer fit.</p>

Question 21

<p>What happens to the number of substrate molecules and product molecules as a reaction proceeds</p>

Answer 21

<p>Substrate - decrease

| Product - increase</p>

Question 22

<p>Two ways you can measure rate of reaction</p>

Answer 22

<p>- Increasing levels of product

| - decreasing levels of substrate</p>

Question 23

What do cofactors do in a reaction?

Answer 23

They help the enzyme and substrate to bind together, they don’t participate directly in the reaction so they are not used up or changed in the reaction.

Question 24

What do co enzymes do in a reaction?

Answer 24

They often act as carriers, moving chemical groups between different enzymes, they are continually recycled during this process (reaction A changed Co enzyme 1 into co enzyme 2, co enzyme 2 is then used in reaction B where it is converted back into co enzyme 1, and so on)

Question 25

what is the difference between reversible and irreversible inhibitors?

Answer 25

irreversible have strong, covalent bonds so the inhibitor can’t be removed as easily.

reversible have weak, hydrogen or ionic bonds so the inhibitor can be removed and the inhibition is reversible.