B1.2 - proteins

Question 1

cytokinesis

Answer 1

cell division

Question 2

peptide

Answer 2

a chain of 2-50 amino acids joined through condensation reactions

Question 3

polypeptide

Answer 3

chains of over 50 amino acids

Question 4

prosthetic group

Answer 4

non-protein molecules that bind with quaternary structures or proteins (haem group in haemoglobin)

Question 5

signal transduction pathway

Answer 5

a sequence of resources in a cell that is initiated when a signalling molecule binds to its receptor

Question 6

what are the components of an amino acid?

Answer 6

central carbon atom with 4 groups:
- amine group (NH2)
- carboxyl group (COOH)
- R-group (20 different chemical groups)
- hydrogen (H)

Question 7

what is the word equation for forming dipeptides?

Answer 7

amino acid + amino acid –> dipeptide + water
- condensation reaction

Question 8

what is the word equation for forming a tripeptide?

Answer 8

dipeptide + amino acid –> tripeptide + water
- condensation reaction

Question 9

peptide

Answer 9

single linear chain of 2-50 amino acid monomers held by a peptide bond

Question 10

polypeptide

Answer 10

single linear chain of 51+ amino acid monomers held by a peptide bond

Question 11

what are the dietary requirements for amino acids?

Answer 11

• essential amino acids cannot be synthesized so must be obtained from food
• non-essential amino acids can be made from other amino acids
• vegan diets require attention to ensure essential amino acids are consumed

Question 12

what is the role of haemoglobin?

Answer 12

binds to oxygen, allowing transport of oxygen in erythrocytes

Question 13

what is the role of insulin?

Answer 13

hormone that causes the uptake of glucose from the blood by body cells (muscle and liver)

Question 14

what is the role of collagen?

Answer 14

structural hormone found in skin and connective tissue such as tendons

Question 15

what is the role of immunoglobulins?

Answer 15

proteins that function as antibodies, binding to antigens on pathogens (non-self cells)

Question 16

what is the role of fibrinogen?

Answer 16

protein involved in blood clotting

Question 17

what is the role of actin?

Answer 17

protein involved in cytokinesis and muscle contraction
- subunits join together to form filaments

Question 18

what is the role of microtibules?

Answer 18

proteins that form the spindle fibres that move chromosomes during mitosis and meiosis
- two different subunits join to form a dimer which joins to form a filament

Question 19

why is there infinite variety of possible peptide chains?

Answer 19

• peptide chains can have any number of amino acids
• there are 20 amino acids coded for in the genetic code
• amino acids can be in any order

Question 20

what are proteins composed of?

Answer 20

one or more polypeptides folded into a particular conformation

Question 21

how can high temperatures cause denaturation?

Answer 21

1. vibrations at high temperatures break bonds
2. intramolecular bonds within the protein are broken
3. irreversible change to conformation of a protein
4. protein cannot carry out it’s function OR soluble proteins become insoluble and precipitate

Question 22

how can extreme pH’s cause denaturation?

Answer 22

1. extreme pH alters amino acid’ charges and breaks ionic bonds
2. intramolecular bonds within the protein are broken
3. irreversible change to conformation of a protein
4. protein cannot carry out it’s function OR soluble proteins become insoluble and precipitate