B1.2 - proteins (2f)

Question 1

what are proteins?

Answer 1

proteins are made of chains of amino acids

Question 2

where are proteins made?

Answer 2

proteins are made on ribosomes, using information from the base sequence of DNA

Question 3

what determines a proteins’ function?

Answer 3

the sequence and number of amino acids determine the 3D shape of the protein and therefore its function

Question 4

what are some examples of proteins?

Answer 4

e.g) enzymes, hormones, fibrinogen, spindle fibres, haemoglobin

Question 5

what are the dietary requirements for amino acids?

Answer 5

• 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 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

what is a peptide?

Answer 9

a single linear chain consisting of typically 2-50 amino acid monomer units held together by peptide bonds

Question 10

what is a polypeptide?

Answer 10

a single linear chain consisting of typically 51+ amino acid monomer units held together by peptide bonds

Question 11

what is a protein made out of?

Answer 11

one or more polypeptides, folded into a 3D conformation that determines its function

Question 12

why is there infinite variety of possible peptide chains?

Answer 12

this is due to a combination of three factors:
- peptide chains can have any number of amino acids, from a few to thousands
- there are 20 amino acids coded for in the genetic code
- these amino acids can be in any order

Question 13

what is denaturation?

Answer 13

irreversible change to the conformation of a protein

Question 14

what causes denaturation?

Answer 14

high temperatures and extreme pHs cause denaturation

Question 15

what is the impact of denaturation?

Answer 15

denaturation affects enzymes by changing the shape of its active site, so the substrate is unable to attach
- this slows the rate of enzyme activity by preventing the reaction

Question 16

how can high temperatures cause denaturation?

Answer 16

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

Answer 17

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

Question 18

what is the role of haemoglobin?

Answer 18

haemoglobin = binds to oxygen, allowing transport of oxygen in erythrocytes

Question 19

what is the role of insulin?

Answer 19

insulin = a hormone that causes uptake of glucose from the blood by many body cells including muscle and liver cells

Question 20

what is the role of collagen?

Answer 20

collagen = a structural hormone found in skin and connective tissue such as tendons

Question 21

what is the role of immunoglobulins?

Answer 21

immunoglobulins = proteins that function as antibodies, binding to antigens on ‘non-self’ cells, such as pathogens

Question 22

what is the role of fibrinogen?

Answer 22

fibrinogen = a protein involved in blood clotting

Question 23

what is the role of actin?

Answer 23

actin = a protein in muscle fibers which is involved in cytokinesis and muscle contraction
- the subunits join together to form filaments

Question 24

what is the role of microtubules?

Answer 24

microtubules = proteins that form the spindle fibres that move chromosomes during mitosis and meiosis
- two different subunits join to form a dimer, which then join together to form filaments