B1.2-proteins

Question 1

common structure of amino acid

Answer 1

central alpha carbon
-amine group to left of carbon
-carboxyl group to left of carbon
-hydrogen atom above carbon
-R group to remaining covalent bond

Question 2

process of condensation reaction to form dipeptides and long chains of amino acids

Answer 2

-carboxyl group from one amino acid reacts with amine group of another, releasing a water molecule and forming a peptide bond.

Question 3

essential amino acids

Answer 3

-cells can synthesize 11/20 amino acids, the 9 have to come from food called essential amino acids
-they cannot by synthesized by the body
examples; meat
-diets must include different sources of protein to include all the different amino acids

Question 4

reasons for variety in polypeptides

Answer 4

-DNA number and order amino acids within polypeptides
-20 different amino acids in genetic code
-can very in length, from a few to thousands
-amino acids can be arranged in different orders

Question 5

examples of common polypeptides

Answer 5

hemoglobin
keratin
lipase
collagen
histones
insulin

Question 6

what is denaturation

Answer 6

when proteins are placed in environment that is higher in temp/Ph than their physiological optimum, it puts stress on many of the weak hydrogen bonds, resulting in loosing shape and function.

Question 7

chemical diversity of R groups

Answer 7

-R groups that are non-polar are hydrophobic
-Hydrophilic R groups can be divided into; acidic and basic

-polar due to negative ionization charge= acidic R group

-polar due to positive ionization charge= basic R group

Question 8

structures of proteins

Answer 8

1) primary-sequence of amino acids in polypeptide chain held by peptide bonds. determined by DNA of cell
2) secondary structure
-formation of complex shapes within polypeptide chain. Occurs due to hydrogen bonds between R groups. Sequence folds into either alpha helix or beta plated sheaths. (proteins that have purely a-helix, b-plated shape form complex globular shapes)
3) tertiary structure-polypeptide chain folds to form complex 3D shape. Gives proteins specific shapes like receptor sites. Folding occurs due to interactions like;
1)hydrogen bonds between polar R groups
2)hydrophilic/phobic interactions within interior
3)covalent bonds between R groups cysteine to form disulphide bridges
4)ionic bonds-between charged R group
4) quaternary structure-linking of two or more polypeptides to form single protein. Same types of intermolecular bonding used as in territory structure

Question 9

effects of polar and non-polar amino acids on territory structure

Answer 9

proteins composed of non-polar amino acids have poor solubility, proteins composed of polar amino acids have much better solubility and found in different locations of the body

Question 10

lipase and glycoprotein A/B solubility

Answer 10

lipase=hydrophobic amino acids are clustered in the core of globular proteins and polar amino acids on outside permit solubility in water environments (small intestine)
glycoproteins A/B=integral proteins have regions with hydrophobic amino acids, helping them embed in membranes

Question 11

conjugated proteins

Answer 11

proteins that also contain non-polypeptide components (contain a prosthetic group)

Question 12

3 examples of proteins with quaternary structure

Answer 12

1) INSULIN= non-conjugated globular protein. composed of two polypeptide chains, linked by two disulfide bridges with no prosthetic group

2) COLLAGEN=non-conjugated fibrous protein. 3polypeptide chains coiled tightly together into triple helix structure. found in tissues; skin, bone. structure supports function; strength/ elasticity

3) HAEMOGLOBIN= conjugated globular protein. consists of multiple polypeptide chains. 4 subunits and prosthetic haem group.

Question 13

fibrous and globular proteins

Answer 13

fibrous=structural protein. Long repeated structure
globular= proteins with specialized function. Metabolically active. Rounded formation

Question 14

aspects to include when comparing globular/ fibrous proteins (e.g; insulin/collagen)

Answer 14

• shape
• amino acid sequence(insulin= irregular amino acid sequence)
  -solubility(insulin soluble)
  -bonding (insulin=two polypeptide held by two disulfide bridges, collagen= 3 polypeptides held by H bonds)
  -functional or structural

Question 15

insulin function

Answer 15

help regulate the passage of glucose from bloodstream into cell