Topic 2-Proteins

Question 1

primary structure

Answer 1

Sequence of amino acids in polypeptide chain
- amino acids joined in condensation reaction to form dipeptide (peptide bond forms between subunits)

Question 2

Secondary structure

Answer 2

Interactions between side groups cause 3D shape
lengths may coil into alpha helices or beta pleated sheets
shape maintained by hydrogen bonds between CO and NH groups

Question 3

Tertiary structure

Answer 3

folding up into final 3D structure
caused by various interactions within the protein (ionic/hydrogen bonds/hydrophobic interactions)
strongest links caused between neighbouring cysteine amino acids (form di-sulphide bridges)

Question 4

quaternary structure

Answer 4

arrangement of polypeptide chains into a functional protein
complex proteins exist as aggregations of polypeptide chains

Question 5

conjugated proteins

Answer 5

proteins containing non-protein material
non-protein part= prosthethic group

Question 6

denaturation of proteins

Answer 6

loss of 3D structure of the protein
often permanent
causes disruption/ alteration in bonds that maintain secondary and tertiary structure
sequence of amino acids remains unchanged

Question 7

fibrous proteins structure

Answer 7

repetitive regular sequences of amino acids with NON POLAR R groups
polypeptide chains spiral- NO SECONDARY STRUCTURE
no tertiary structure- many have quaternary structure with different polypeptide chains being R group cross-linked to form long parallel strands

Question 8

fibrous proteins properties

Answer 8

length may vary within one protein
stable in wide range of conditions
insoluble due to close packing of polypeptide chains and non-polar nature of R groups in AA primary structure
support and structure

Question 9

fibrous protein examples

Answer 9

collagen, keratin, actin, myosin

Question 10

globular proteins structure

Answer 10

specific irregular amino acid sequences
change in primary structure greatly changes function
affects bond formation in tertiary structure
most have sec structure
ALL tert structure
polypep chain folds into spherical shapes that are maintained by bonds between R groups

Question 11

glob properties

Answer 11

length highly specific to protein
sensitive to changes/ presence of chemicals
soluble- hydrophilic R groups- H bond interactions

Question 12

primary structure + solubility

Answer 12

primary structure determines folding of polypeptide
form globular structure
hydrophobic r groups located in centre of protein (/ obverse- hydrophilic r groups on outside of protein)
water forms hydrogen bonds with protein/ hydrophilic groups

Question 13

primary structure + function

Answer 13

diff primary structure (sequence of amino acids)
different r group
other structures will change (sec/tert/quart)
change in H bonds holding molecule in 3D shape

Question 14

effect of removing/ changing base on protein structure

Answer 14

deletion could affect every codon- frame shift
- results in diff sequence of AA
substitution would only affect one
- may code for same amino acid- degenerate nature of code
deletion more likely to affect position of start/stop codon