Biochemistry: Protein Structure and Function

Question 1

primary structure of protein

Answer 1

polypeptide chain of amino acid residues

Question 2

secondary structure of protein

Answer 2

localised conformation of polypeptide backbone

Question 3

tertiary structure of protein

Answer 3

3-D conformation of polypeptide including side chain

Question 4

quaternary structure of protein

Answer 4

spatial arrangement of polypeptide chains in a protein with multiple subunits

Question 5

at what angles can proteins rotate around

Answer 5

the alpha carbon and the amino acid group

the alpha carbon and the carboxyl group

Question 6

3 types of secondary structures

Answer 6

• alpha-helices
• beta-sheets
• collagen triple helix

Question 7

describe alpha-helices

Answer 7

• 1 chain, mostly R handed

- the carboxyl group binds with the amine group 4 residues away

Question 8

why does proline break down alpha helices

Answer 8

causes a kink in the chain

Question 9

describe beta-sheets

Answer 9

• can invole 1+ chains
• not folded, turns between strands
• C=O and N-H of neighbouring peptides form hydrogen bonds

Question 10

what are beta-pleated sheets

Answer 10

repeated zig zag patterns

Question 11

what is collagen a component of

Answer 11

bone and connective tissue

Question 12

is collagen water in/soluble

Answer 12

insoluble

Question 13

describe the structure of collagen

Answer 13

3 L-handed helical chains twist around each other to form a R-handed super helix - tropocollagen

Question 14

what bonding occurs in tropocollagen

Answer 14

• inter-chain H bonds

- intra- and inter-molecular bonds

Question 15

what happens as a result of weakened collagen

Answer 15

• bleeding gums - Scurvy

Question 16

what is covalent crosslinking and what does it increase with

Answer 16

• covalent bonding of 2+ molecules, can alter properties

- age

Question 17

2 types of tertiaty structures

Answer 17

• fibrous

- globular

Question 18

describe the general structure of tertiary proteins

Answer 18

local regions with distinct secondary structures

Question 19

describe fibrous proteins

Answer 19

• polypeptides arranged along 1 axis
• water insoluble and dilute salt solutions
• made of long fibres/large sheets
• mechanically strong
• structural roles

Question 20

describe globular proteins

Answer 20

• folded into roughly spherical shape
• soluble in water and salt solutions
• polar chains on outside and non-polar on inside
• interact with aq environment bu H bonding and dipole-dipole interactions
• big helix and sheet sections

Question 21

what forces stabilise tertiary structures

Answer 21

• covelant disulphide bonds
• electrostatic interaction (salt bridges)
• hydrophobic interactins
• H bonds
• complex with metal ions

Question 22

how are disulphide bonds formed

Answer 22

via oxidation (often redox centres), 1 side reduced, other oxidised

Question 23

what happens as a result of disulphide bonds

Answer 23

reversible changein shape and function

Question 24

describe electrostatic interactions

Answer 24

• -ve attracts +ve
• charged side groups located on the outside of proteins and they react with water
• salt bridges

Question 25

describe hydrophobic interactions

Answer 25

• strong organising influence

- hydrophobic side chains tend to cluster in the middle

Question 26

what level of structure contain all the information needed for folding

Answer 26

primary

Question 27

what specialised proteins aid folding of proteins

Answer 27

chaperons

Question 28

when can proteins begin folding

Answer 28

• after translation

- before translation is finished

Question 29

what can cause proteins to denature and why

Answer 29

• heat, increases vibrations within a protein
• pH, electrostatic interactions disrupted
• detergents, urea, guanidine, hydrochloride, disrupts hydrophobic interactions
• thiol and reducing agents, reduce and disrupt disulphide bonds

Question 30

describe myoglobin’s structure and functions

Answer 30

• globular with a haem prosthetic group
• 1 haem group binds 1 oxygen molecules
• stored O2 in muscle

Question 31

describe haemoglobins structure and function

Answer 31

• 2 alpha and 2 beta subunits, each containing a haem group - each binds 1 O2
• exhibits co-operativity
• transports O2 in blood