B1.2 Proteins

Question 1

what monomers make up proteins

Answer 1

amino acids

Question 2

what determines the shape and function of the protein

Answer 2

the sequence, type and number of amino acids present

Question 3

how many naturally occurring amino acids there

Answer 3

20

Question 4

amino acid + amino acid

Answer 4

dipeptide

Question 5

how many essential amino acids are there

Answer 5

9

Question 6

what are essential amino acids

Answer 6

amino acids that can’t be synthesised

Question 7

what does the genetic code (DNA base sequence) code for

Answer 7

the number and order of amino acids in a polypeptide

Question 8

for a chain of 50 amino acids, how many possible combinations would there be

Answer 8

20^50

Question 9

some roles of proteins

Answer 9

catalysis by enzymes
blood clotting - interact w oxygen to form scab
strengthen fibres in skin (collagen, keratin)
immune system antibodies
hormones

Question 10

how does heat denaturation affect protein structure

Answer 10

heat causes vibrations within protein molecules, breaking intramolecular bonds so conformation changes
irreversible

Question 11

how does pH affect protein structure

Answer 11

pH change causes intramolecular bonds to break within the protein molecule

Question 12

why is there a lot of chemical diversity between the amino acids

Answer 12

the r groups vary a lot between the 20 amino acids

Question 13

role of r groups

Answer 13

determine properties of amino acids- acidic/basic, polar/non polar etc

Question 14

___________ R groups are polar and can be either acidic or basic

Answer 14

Hydrophillic

Question 15

what are proteins

Answer 15

relatively large complex molecules that contain one or more chains of amino acids known as polypeptides

Question 16

what is primary structure

Answer 16

the sequence of amino acids in a polypeptide chain

Question 17

what is secondary structure

Answer 17

the formation of secondary structures - alpha helices and beta pleated sheets

Question 18

why do these secondary structures form

Answer 18

as a result of hydrogen bonding between different amino acids in the chain

Question 19

what happens in the tertiary structure

Answer 19

how the secondary structures fold to form a 3d structure

Question 20

what does the folding in the tertiary structure result from

Answer 20

the interactions between the r groups of the amino acids and the environment

Question 20

what types of bonding are there in the tertiary structure

Answer 20

peptide bonds
hydrogen bonds( r groups +amino+carboxyl groups)
disulfide
ionic
hydrophobic interactions

Question 21

are the amino acids in protein polar or non polar

Answer 21

non polar so less soluble in aqueous solutions

Question 22

examples where non polar amino acids in protein are used for structural purposes

Answer 22

in the centre of protein to stabilise
at surface of cell so in contact with membrane- glycoproteins

Question 23

what does quatenary structure refer to

Answer 23

the way the polypeptides fit together when there is more than one polypeptide in a protein

Question 23

example of a protein that has a quaternary structure

Answer 23

haemoglobin - it is a conjugated protein-4 polypeptide chains and 4 heme groups

Question 23

where are polar amino acids found in the cell

Answer 23

on surface of membrane because they can interact with water molecules
line pores in membrane creating hydrophilic channels for transport of polar molecules

Question 24

what is a conjugated protein

Answer 24

a protein with one or more non protein groups

Question 25

examples of non conjugated proteins

Answer 25

insulin and collagen

Question 26

what does insulin consist of

Answer 26

2 chains of amino acids joined by disulfide bridges (21+32)
forms 2 quaternary structures- dimers and hexamers which as as storage molecules

Question 27

what does collagen consist of

Answer 27

a fibrous protein with 3 polypeptide chains held by hydrogen bonds (which allow for good tensile strength) in a helix shape

Question 28

where does the hydrogen bonding in the secondary structure occur

Answer 28

between the amino and carboxyl groups

Question 29

example of globular protein

Answer 29

insulin also functions as hormone

Question 30

what does insulins properties allow for

Answer 30

its small size and hydrophilic surface allows it to be dissolved in blood plasma
shape allows it to bind to specific receptor protein

Question 31

what are fibrous proteins

Answer 31

long strands of polypeptide chains that have cross linkages due to hydrogen bonds

Question 32

where can collagen be found

Answer 32

it has a flexible structure so forms connective tissues- tendons, ligaments, bones, skin

Question 33

shape of globular proteins

Answer 33

roughly circular

Question 34

shape of fibrous proteins

Answer 34

long strands

Question 35

amino acid sequence in globular

Answer 35

irregular and wide range of r groups

Question 36

amino acid sequence

Answer 36

repetitive with a limited range of r groups

Question 37

function of globular

Answer 37

physiological/functional

Question 38

function of fibrous

Answer 38

structural

Question 39

examples of globular

Answer 39

haemoglobin, enzymes, insulin, immunoglobin

Question 40

examples of fibrous

Answer 40

collagen, keratin, myosin, actin, fibrin

Question 41

solubility of globular

Answer 41

generally soluble in water

Question 42

solubility of fibrous

Answer 42

generally insoluble in water