Enzymes

Question 1

What is the effect of SUBSTRATE concentration on the rate of enzyme action?

Answer 1

• Low substrate concentration = too few substrate molecules to occupy all the available active sites = low rate of reaction
• Increasing Substrate Concentration increases the rate of reaction. This is because more substrate molecules will be colliding with enzyme molecules, so more product will be formed. all the active sites are occupied at one time
• However, after a certain concentration, any increase will have no effect on the rate of reaction, since Substrate Concentration will no longer be the limiting factor.
  The enzymes will effectively become saturated, and will be working at their maximum possible rate.

Question 2

What is an enzyme inhibitor?

Answer 2

substances that directly or indirectly interfere with the functioning o the active site of an enzyme and so reduce its activity

Question 3

What are competitive inhibitors (tell me about them)?

Answer 3

• they bind to the active site of the enzyme
• they have a molecular shape similar to that of the substrate, allowing them to occupy the active site of an enzyme
• they compete with the substrate for available active series

Question 4

Describe how the effect on enzyme activity the competitive inhibitor has is determined?

Answer 4

the difference between the concentration of the inhibitor and the concentration of the substrate determines this :

• if the substrate concentration is increased the effect of the competitive inhibitor is reduced
• Since inhibitors are not permanently bound to the active site when it leaves another molecule can take its place. the concentration of the substrate and the inhibitor depends on this.
• sooner or later, all the substrate molecules will occupy an active site ———> the greater the concentration of inhibitor, the longer this will take

Question 5

What are non-competitive inhibitors (tell me about them)?

Answer 5

• they bind to the enzyme at a position other than the active site
• when they attach to the enzyme at the binding site, they alter the shape of the enzyme and thus its active site, in such a way that substrate molecules can no longer occupy it and so the enzyme cannot function

Question 6

What is the definition of metabolism?

Answer 6

the sum of all the biochemical reactions in the body

Question 7

What is the definition of a metabolic pathway?

Answer 7

a single chain of a biochemical reaction in the body

Question 8

What does every reaction require to work?

Answer 8

an input of energy (activation energy)

Question 9

What is the function of RNA?

Answer 9

transfers genetic information from DNA to ribosomes rather than holds information (like DNA)

Question 10

What are enzymes?

Answer 10

They are globular proteins that act as catalysts to both anabolic (building up) and catabolic (breaking down) reactions. They work both in intracellular and extracellular conditions

Question 11

What must happen for a chemical reaction to happen?

Answer 11

The enzyme must collide with the substrate with suffient energy
The substrate must fit into the active site

Question 12

What is the induced fit model?

Answer 12

A
An enzyme-substrate complex forms when the active site changes shape slightly so it is complementary to the substrate

this reduces the activation energy

Question 13

What is the effect of temperature on enzyme action?

Answer 13

ncrease in temp = increase in kinetic energy= molecules moving around more rapidly and colliding with each other more frequently= more enzyme-substrate complexes= increase in the rate of reaction

Optimum temperature = highest number of collisions and enzyme - substrate complexes

High temperatures to very high temperatures = lots of kinetic energy = Hydrogen bonds holding the 3d structure together breaking = the substrate fits less easily into the active, causing the reaction to slow down = eventually the enzyme doesnt have an active site that fits the substrate anymore- no more enzyme- substrate complexes made due to the enzyme denaturing

Question 14

What is the effect of pH on enzyme action?

Answer 14

Slight change in pH = slightly alters the charge = harder for enzyme-substrate complexes to form
change in pH = alters the charge on the amino acid that makes up the active site of the enzyme = substrate can no longer become attached o the active site enzyme-substrate complex cannot be formed
change in pH can cause the bonds maintaining the enzyme’s tertiary structure (Hydrogen and ionic bonds) to break.

Question 15

How is the arrangement of the active site determined?

Answer 15

determined by the hydrogen and ionic bonds between —-NH2 and ——COOH groups of the polypeptides that make up the enzyme. The change in H+ ions affects this bonding, casing the active site to change shape

Question 16

Q
Why is it unlikely for enzymes to denature via pH?

Answer 16

A
because pH fluctuations inside organisms are usually small

Question 17

why aren’t enzymes used up?

Answer 17

Because once an active site on an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule = not used up

Question 18

What is the effect of ENZYME concentration on the rate of reaction?

Answer 18

low enzyme concentration = too few enzyme molecules to allow all substrate molecules to find an active site at one time= rate of the reaction low
intermediate enzyme concentration = all the substrate molecules can occupy an active site at the same time = high rate of reaction
very high enzyme concentration = the addition of further enzyme molecules has no effect as there are already enough active sites to accommodate all the available substrate molecules. This is because it is a LIMITING FACTOR

Question 19

Draw condensation reaction between two amino acids

Answer 19

Question 20

What are nucleic acids, what are two different types, and what do they do?

Answer 20

Nucleic acids are polymers made out of nucleotides

DNA = holds genetic information

RNA = transfers genetic information from DNA to the ribosomes

Question 21

What are ribosomes formed from?

Answer 21

RNA and proteins

Question 22

What is the structure of DNA?

Answer 22

• a double helix with two polynucleotide chains held together by hydrogen bonds between complementary base pairs
• pentose sugar (because it has 5 carbons ) =deoxyribose
• phosphate group
• a nitrogen-containing organic base : cytosine, thymine, adenine, guanine

Question 23

What is the difference between DNA and proteins?

Answer 23

DNA is a sequence of bases but proteins are a sequence of amino acids

Question 24

Draw the structure of a phosphodiester bond

Answer 24

Question 25

What chemical reaction forms a nucleotide and what bond is created when two nucleotides undergo this chemical reaction?

Answer 25

condensation reaction

A condensation reaction between two nucleotides forms a phosphodiester bond

Question 26

What is the structure of RNA?

Answer 26

• relatively short polynucleotide chain
• pentose sugar = ribose
• phosphate group
• a nitrogen-containing organic base: cytosine, uracil, adenine, guanine