proteins

Question 1

what are proteins made of?

Answer 1

carbon
hydrogen
oxygen
nitrogen
some sulfur

Question 2

what are the functions of proteins?

Answer 2

enzymes that catalyse reactions
carrier/transport proteins
antibodies
structural support for cells
hormone transmit information
enable muscles to contract

Question 3

what are proteins?

Answer 3

polymers made up of amino acid monomers

Question 4

how many different naturally occurring amino acids are there?

Answer 4

20

Question 5

what does an amino acid contain?

Answer 5

amino group
R functional/variable group
carboxyl group

Question 6

what bond is in a protein?

Answer 6

peptide bond

Question 7

what is the primary structure of a protein?

Answer 7

a sequence of amino acids bonded by peptide bonds
forms a polypeptide
has no functions

Question 8

what is the secondary structure of a protein?

Answer 8

alpha helix or beta pleated sheat

Question 9

what is an alpha helix?

Answer 9

chains of amino acids coiled
stabilised by hydrogen bonds between carboxyl and amino groups

Question 10

what are beta pleated sheets?

Answer 10

parts of amino acid chain are folded and lie next to each other
held in place by hydrogen bonds

Question 11

what is the tertiary structure of a protein?

Answer 11

chains become folded into a globular or fibrous shape
(include areas of helix and pleated sheet)

Question 12

what are the bonds in a tertiary structure?

Answer 12

hydrogen bonds
ionic bonds
disulphide bonds

Question 13

where are the hydrogen bonds in a tertiary structure?

Answer 13

between OH and R groups

Question 14

where are the ionic bonds in a tertiary structure?

Answer 14

oppositely charged amino acids form bonds due to positive or negative R groups

Question 15

where are the disulphide bonds in a tertiary structure?

Answer 15

amino acid cysteine contains sulfur
between two sulfur atoms in two cysteines which are close together

Question 16

what are the functions of a protein in its tertiary structure?

Answer 16

enzymes
plasma/channel/carrier proteins

Question 17

what is the quaternary structure of a protein?

Answer 17

two or more polypeptide chains

Question 18

what is an example of a quaternary structure?

Answer 18

haemoglobin

Question 19

what happens if proteins unfold?

Answer 19

it will lose its 3 dimensional shape so will lose its function

Question 20

what can cause a protein to unfold?

Answer 20

shifts in temperature or ph
exposure to detergent/salts

Question 21

what happens in the primary and secondary structure of a globular protein?

Answer 21

chains of amino acids
alpha helix and bet pleated sheets held together by hydrogen bonds

Question 22

what happens in the tertiary structure of a globular protein?

Answer 22

folds into a precise globular 3D shape
hydrogen, ionic, disulphide bonds
hydrophobic and hydrophilic interactions

Question 23

what does haemoglobin contain (groups)?

Answer 23

contains prosthetic group (non-protein) called the haem group

Question 24

what way do the hydrophobic and hydrophilic group point in haemoglobin?

Answer 24

hydrophobic group points inwards
hydrophilic group points outwards
so it is soluble in water

Question 25

what is in haemoglobin?

Answer 25

2 alpha polypeptide chains and 2 beta polypeptide chains
each chain has prosthetic haem group containing iron ions

Question 26

what does iron ions in prosthetic haem group do in haemoglobin?

Answer 26

bind to oxygen molecules
(4 x O2 = 8 oxygen molecules)

Question 27

what is the function of haemoglobin?

Answer 27

haem group binds to oxygen in the lungs
transports oxygen to tissues where it is released and used by cells in aerobic respiration

Question 28

what are the different colours of haemoglobin?

Answer 28

haemoglobin (bluish red) + 4O2 –> oxyhaemoglobin (bright red)

Question 29

what are the conditions needed to make haemoglobin separate from oxygen?

Answer 29

low partial pressure of oxygen
high CO2 level and low pH to make it more efficient

Question 30

what is the primary and secondary stage of a fibrous protein (collagen)?

Answer 30

a polypeptide chain coils up into a left handed alpha helix
3 of these left-handed alpha helixes twist together to form a triple helix or collagen molecule

Question 31

what happens after triple helices/collagen molecules are formed?

Answer 31

triple helices/collagen molecules interact to form collagen fibrils (cross linked by covalent bonds)
collagen fibrils can make a collagen fibre

Question 32

what is the structure of a triple helix in a fibrous protein?

Answer 32

3 polypeptide chains twisted together
contains high proportion of amino acids alanine and proline
every third amino acid is glycine (smallest amino acids so allows chains to get close and form hydrogen bonds)

Question 33

what is the function of collagen?

Answer 33

gives strength to tendons, ligaments and bones

Question 34

how is collagen strong?

Answer 34

large number of hydrogen bonds between helices so molecules/fibres are very strong
strength is also increased by covalent crosslinks between collagen molecules