proteins

Question 1

what are the roles of proteins?

Answer 1

• Structural – cytoskeleton
• Catalysts – enzymes
• Carrier/storage – haemoglobin
• Protective – antibodies
• Signalling – receptors, intracellular signalling
• Channels – transport through membranes
• Transporters – transport through membranes and barriers
• Cell adhesion – ECM

Question 2

what are the levels of structure of a protein?

Answer 2

primary - amino acid sequence
secondary - 2D folding
tertiary - 3D folding
quaternary - interaction of subunits

Question 3

what are the ends of a protein?

Answer 3

N terminus - comes out the ribosome first

C terminus - comes out the ribosome last

Question 4

which end of the amino acid is the amine end?

Answer 4

N terminus

Question 5

which end of the amino acid is the carboxylic acid end?

Answer 5

C terminus

Question 6

what chemical implications does the peptide bond have?

Answer 6

planar molecule

H bonding

Question 7

what determines secondary structure?

Answer 7

hydrogen bonding between peptide bonds

Question 8

which amino acid isnt found in an alpha helix?

Answer 8

proline

Question 9

describe an alpha helix

Answer 9

• Peptide chain spiralling and the peptide bonds are essentially running vertically
• R groups facing outwards

Question 10

what kind of bonding can you have in a tertiary structure?

Answer 10

hydrogen bonding, ionic bonding, disulphide bridges and hydrophobic and hydrophilic interactions

Question 11

what are the types of tertiary structure?

Answer 11

o Globular = water soluble e.g haemoglobin MAJORITY

o Fibrous= insoluble e.g collagen, keratin

Question 12

what is quaternary subunits?

Answer 12

when multiple subunits come together

Question 13

what type of protein is collagen?

Answer 13

fibrous protein

Question 14

where can you find large scale quaternary protein complexes?

Answer 14

viral capsid

Question 15

describe the amino acid sequence of collagen?

Answer 15

proline-proline-glycine

Question 16

how much of collagen is glycine?

Answer 16

35%

Question 17

describe the structure of collagen

Answer 17

collagen triple helix - helps with strength bc of H bonding
post-translational modifications which enable covalent modifications e.g. di-sulphide bridges between cystines and lysines

Question 18

what is the most common type of protein?

Answer 18

globular

Question 19

when is a protein at its lowest energy level?

Answer 19

when its fully folded

Question 20

what is the hydrophobic effect?

Answer 20

when proteins fold so you can get a hydrophobic centre

Question 21

what can unfold proteins?

Answer 21

heat
ph
detergent

Question 22

what are molecular chaperones?

Answer 22

help fold proteins

Question 23

when do levels of chaperones increase?

Answer 23

when the cell is subjected to stress

Question 24

what can cause protein disease and by what mechanism?

Answer 24

cause; environmental stress or inherited mutation

mechanism; loss of function, toxic gain of function, dominant negative

Question 25

what diseases can misfolding of proteins cause?

Answer 25

neurodegeneration (alzheimers or parkinsons)

metabolic disorders (monogenic obesity)

cancer

Question 26

what do post-translational modifications involve?

Answer 26

adding other functional groups, adding other proteins, changing the chemical nature of amino acids and structural changes

Question 27

what is phosphorylation?

Answer 27

addition of a phosphate group

Question 28

what is a disulphide?

Answer 28

covalent bond between cysteines which can stabilise a 3D structure