2.2. 8-10 Proteins

Question 1

What are amino acids?

Answer 1

monomers of all proteins, and all amino acids have the same basic structure

Question 2

What is a peptide bond?

Answer 2

a bond formed when two amino acids are joined by a condensation reaction

Question 3

What functions do the properties of proteins give them?

Answer 3

1. Form structural components of animals in particular for example, muscles are made of proteins
2. Their tendency to adopt specific shapes makes proteins important as enzymes, antibodies and some hormones
3. Membranes have proteins constituents that act as carriers and pores for active transport across the membrane and facilitated diffusion

Question 4

What are essential amino acids?

Answer 4

Animals can make some amino acids but must ingest the others.

Question 5

Plants can make all the amino acids they need but only when… ?

Answer 5

If they can access fixed nitrogen such as nitrate

Question 6

What does each amino acid contain?

Answer 6

Carbon, hydrogen, oxygen and nitrogen. Some may contain sulfur

Question 7

What is the structure of an amino acid

Answer 7

1. Amino group (-NH2)
2. Carboxyl group (-COOH) on the other end
3. R Group + H

Question 8

What is the simplistic amino acid?

Answer 8

Glycine

Question 9

What enzymes break peptide bonds during digestion?

Answer 9

Protease, they also break down protein hormones so that their effects are not permanent

Question 10

How can an amino acid act as a buffer?

Answer 10

1. Carobxyl group can ionise
2. Amino group can accept an H+ ion
3. At low pH the amino acid will accept H+
4. At high pH, the amino acid will release H+ ions which means it has acidic and base properties\yy

Question 11

What is a primary structure?

Answer 11

the sequence of amino acids found in a molecule

Question 12

What is a quaternary structure?

Answer 12

It is a protein structure where a protein consists of more than one polypeptide chain. For example, insulin.

Question 13

What is the secondary structure?

Answer 13

• The coiling or folding of an amino acid chain, which arises often as a result of hydrogen bond formation between different parts of the chain.
• The main forms of secondary structure are the helix and the pleated sheet.

Question 14

What is the tertiary structure?

Answer 14

• The overall three-dimensional shape of a protein molecule. It’s shape arises due to interactions including hydrogen bonding, sulfide bridges, ionic bonds and hydrophobic interactions.

Question 15

How many amino acids are there?

Answer 15

20. There is a 20^100 possible ways of ordering 100 amino acids

Question 16

How is the helix held of a secondary structure?

Answer 16

Hydrogen bonding between the -NH group of one amino acid and the -CO of the other

Question 17

How is a β-pleated sheet formed in a secondary structure?

Answer 17

When chains in a zig zag structure fold over on itself.

Question 18

What makes the alpha helix and beta pleated sheet stable?

Answer 18

Although weak, many hydrogen bonds.

Question 19

Where do the hydrogen bonds form

Answer 19

Between the hydroxyl, carboxyl and amino groups

Question 20

Where do the Ionic bonds form?

Answer 20

Between those carboxyl and amino groups

Question 21

What is the strongest bond, hydrogen bond, Ionic bond or Disulfide links (covalent)?

Answer 21

Strongest: Disulfide bonding
Then: Ionic bonding
Weakest: Hydrogen bonding

Question 22

Where are disulfide links formed?

Answer 22

Disulfide bridges are formed between the R groups of two cysteines

Question 23

What is a fibrous protein?

Answer 23

Has a relatively long, thin structure it is insoluble in water and metabolically inactive, often having a structural role within an organism e.g collagen.

Question 24

What is a globular protein?

Answer 24

• Has molecules of a relatively spherical shape, which are soluble in water and often have metabolic roles within organisms
• Hydrophilic groups always on the outside making it water soluble.
• Specific shapes =

Question 25

What is a prosthetic group?

Answer 25

a non-protein component that forms a permanent part of a functioning molecule

Question 26

Properties of some Fiborous proteins

Answer 26

Collagen:

• Preventing arteries from bursting when withstanding high pressure from blood being pumped by the heart
• Tendons are made of collagen and connect muscles to bones, allowing them to pull on bones

Keratin:

• Found where ever a body part needs to be hard and strong e.g finger nails
• Contains lots of disulfide bridges which makes its stronger

Question 27

Name some globular proteins

Answer 27

Haemoglobin, Insulin, Pepsin

Question 28

What is the quaternary structure of the haemoglobin made of

Answer 28

• 4 Polypeptide: two alpha-globin chains and two beta-globin chains.
• Each with its own tertiary structure forming the whole molecule

Question 29

What is a protein associated with a prosthetic group called?

Answer 29

Conjugated protein

Question 30

What is the function of haemoglobin?

Answer 30

• To carry oxygen from the lungs to the tissues.

- In lugs oxygen molecule binds to the iron in each of the four heam groups in the molecule

Question 31

Structure of Insulin

Answer 31

Two polypeptide chains consisting of:

Alpha helix and beta pleat.

Question 32

Function of Insulin:

Answer 32

Binds to glycoprotein receptors on the outisde of muscle and fat cells to increase their uptake of glucose from the blood and to increase their rate of consumption of glucose.

Question 33

What is the structure of Pepsin?

Answer 33

Single polypeptide chain

Question 34

What is the function of Pepsin?

Answer 34

Digests protein in the stomach

Question 35

Why is computer modelling of protein structures important?

Answer 35

Scientists can predict protein shapes using computer modelling techniques

Question 36

What is Ab initio protein modelling

Answer 36

Model built based on the physical and electrical properties of the atoms in each amino acid in the sequence

Question 37

What is comparative protein modelling

Answer 37

Protein threading, which scans amino acid sequence against a database of solved structures and produces a set of possible models which would match that sequence.