Proteins and Enzymes

Question 1

What is the monomer of a protein?

Answer 1

Amino Acid

Question 2

What is the function of Hb?

Answer 2

Transports oxygen

Question 3

What is the function of antibodies?

Answer 3

Defend the bodies against infections

Question 4

What is the function of enzymes?

Answer 4

Increase the rate at which chemical reaction occur by lowering the activation energy

Question 5

What is the function of actin and myosin?

Answer 5

Involved in muscle contraction

Question 6

What is the structural role of keratin?

Answer 6

Found in nails and hooves

Question 7

What is the structural role of collagen?

Answer 7

Found in tendons

Question 8

How many different types of amino acids are there?

Answer 8

20

Question 9

What groups are in the general structure of an amino acid?

Answer 9

Amine group, alpha carbon, H atom, carboxyl group, variable side chain

Question 10

What type of bond forms a dipeptide?

Answer 10

Peptide bond

Question 11

What type of reaction occurs in the joining of amino acids?

Answer 11

Condensation reaction

Question 12

What is the primary structure of a protein?

Answer 12

The number and sequence of amino acids in a polypeptide chain

Question 13

What is the secondary structure of a protein?

Answer 13

The -NH group has an overall positive charge and the -C=O has an overall negative charge. The H bond forms between the slight positive charge on the H and the slight negative charge on the O. These 2 groups form weak H bonds but because there is so many they are strong. Die to the H bonding the polypeptide chain coils into alpha helixes or beta pleated-sheets

Question 14

What is the tertiary structure of a protein?

Answer 14

Further folding into a specific, complex 3D shape. Contains H bonds, Ionic bonds (between -N-H and -C=O bot being used in the peptide bonds) and Disulphide bridges

Question 15

What is the Quaternary structure of a protein?

Answer 15

Contains a number of single polypeptide chains that are linked inactive number of different ways. They may also contain non-protein groups like iron in Hb

Question 16

What is denaturation?

Answer 16

Increasing the temperature increases the kinetic energy of the molecule making them vibrate which can break the weak bonds holding the structure together, as the bonds break the tertiary shape of the molecules is lost, this is DENATURATION. Denaturation can also be caused by a change in pH which can disrupt the ionic bonds.

Question 17

How do you perform a biuret test?

Answer 17

• Add the sample
• Add an equal volume of biuret solution to the sample
• If the colour changes to purple, protein is present

Question 18

Define activation energy:

Answer 18

• The minimum energy required for a successful chemical reaction

Question 19

How do enzymes speed up the rate of a chemical reaction?

Answer 19

They lower the activation energy by putting pressure on the bonds and bending the bonds on the substrate during the formation of enzyme substrate complexes

Question 20

What is the specific area that is functional called?

Answer 20

A active site

Question 21

What is the majority of the enzyme structure for?

Answer 21

Holding the active site in place

Question 22

What is it called when the unique shape of the active site binds to a substrate?

Answer 22

They are complimentary

Question 23

What is it called when an enzyme active site binds to a substrate?

Answer 23

Enzyme-substrate complex

Question 24

How is the substrate held in the active site in an enzyme-substrate complex?

Answer 24

Temporary bonds form between the substrate and amino acids in the active site

Question 25

In the lock and key theory the active site is … to it’s substrate

Answer 25

Complimentary

Question 26

What does the lock and key model state about the enzymes active site?

Answer 26

It is rigid or inflexible

Question 27

Why is the lock and key theory useful?

Answer 27

It helps to describe the specificity demonstrated by enzymes

Question 28

How was the induced fit model made?

Answer 28

Scientists observed other molecules binding to enzymes at places other than the active site. These molecules altered the activity of the enzyme suggesting the active site can be changed

Question 29

What is the induced fit model?

Answer 29

The substrate ‘induces’ a change in the shape of the active site making it complimentary

Question 30

What are the 2 changes most commonly recorded?

Answer 30

• Formation of products

- Disappearance of substrate

Question 31

How is the rate of reaction measured

Answer 31

The gradient of the graph

Question 32

What effect does temperature have on enzymes?

Answer 32

As the temperature increases the enzymes and substrates have more kinetic energy, so are more likely to collide and form E-S complexes. So the rate of reaction increases.
The temperature causes the H and Ionic bonds to vibrate and break, resulting in the active site changing shape.
If the temperature is increased further than it’s optimum the H and Ionic bonds between the R groups that form the tertiary structure break, featuring the enzyme.

Question 33

What effect does pH have on enzymes?

Answer 33

Effects the H and Ionic bonds between the -NH and the -C=O groups of the amino acids in the tertiary structure so the ionic bonds are broken

Question 34

What effect does concentration have on enzymes?

Answer 34

As the concentration increases the rate of reaction increases as it is no longer the limiting factor therefore the rate if reaction levels off

Question 35

What effect does concentration have on enzymes?

Answer 35

As the concentration increases the rate of reaction increases as it is no longer the limiting factor therefore the rate if reaction levels off

Question 36

What is the role competitive inhibitors?

Answer 36

They compete with the substrate to bind with the active site

• They have a similar shape to the substrate and block the active site preventing E-S complexes from forming
• They are not permanent so only reduce the rate of reaction

Question 37

What is the role of Non-competitive inhibitors?

Answer 37

These bind to the allosteric site (away from the active site), changing the shape of the active site so that the substrate can not bind meaning fewer E-S complexes are formed

Question 38

What is a metabolic pathway?fron optimum

Answer 38

A series of reactions where each stage is catalysed by an enzyme. These enzyme controlled pathways are highly regulated. The enzymes involved in these pathways are usually attached to the cell or organelle in a precise order.
If too much product is made, this could damage the cell in some way. So it’s important to keep a relatively constant concentration of the product in the cell or organelle.
This is achieved through end product inhibition.
This means the final product of the series of metabolic reactions will inhibit the enzyme that catalyses the first reaction.
When the concentration of product decreases, there will be less of it to inhibit the first enzyme, so the pathway starts again.
This is an example of negative feedback. This is when a change away from the optimum concentration of the chemical causes a change that brings the concentration of the chemical back to normal.