Protein

Question 1

Collagen triple helix

Answer 1

• 3 helical polypeptide chains wrapped around each other
• strong water-insoluble fibres
• repeat sequence of X-Pro-Gly or X-Hyp-Gly

Question 2

Collagen triple helix strands held together by

Answer 2

H-bonds involving hydroxyproline and hydroxylysine residues

Question 3

Tertiary structure

Answer 3

Protein folding - Arrangement of helical and pleated sheet sections with respect to each other

Conformations of side chains

= Fibrous proteins
= Globular proteins

Question 4

Globular proteins

Answer 4

• polar residues face surface and interact with solvent
• non-polar residues face interior and interact with each other
• structure is not static

Question 5

Fibrous proteins

Answer 5

• mechanically strong, usually play a structural role in nature

Question 6

Quaternary structure

Answer 6

• Property of proteins that consist of more than one polypeptide chain
• Each chain is a subunit of the oligomer
• Commonly dimers, trimers and tetramers

Question 7

Haemoglobin

Answer 7

• tetramer
• two α- and two β-chains
• chains are similar to myoglobin
• binds 4 oxygens and exhibits positive cooperativity

Question 8

proteins

Answer 8

Polymers of α-amino acids (polypeptides)

with α-carbon / Carboxyl group / Amine group / Side chain

Question 9

Aspartame

Answer 9

• Methyl ester of L-aspartyl-L-phenylalanine
• 200 times sweeter than sugar
• Amino acids have L configuration, substitute D-amino acid for either gives bitter taste

Question 10

different type of R group

Answer 10

polar, uncharged
non-polar (hydrophobic)
basic
acidic

Question 11

polar, uncharged R group

Answer 11

hydroxy / amide / phenol (Tyr) / sulphydryl (Cys

Question 12

non-polar (hydrophobic) R group

Answer 12

alkane /aromatic /methylsulfanyl (Met) / imino acid (Pro)

Question 13

Basic R group

Answer 13

Histidine / Arginine / Lysine

Question 14

Acidic R group

Answer 14

Aspartic Acid / Glutamic acid

Question 15

Non-standard amino acids

Answer 15

• Derived from standard amino acids
• Occur due to post-translational modifications
• extends the range of protein functions by attaching other biochemical functional groups (i.e. phosphate, lipids, carbohydrates), changing the chemical nature of an amino acid or making structural changes (e.g. formation of disulfide bridges).

Question 16

Interactions occur between side-chains

Answer 16

• Covalent bonds
• Electrostatic interactions/ ion-bridges/ salt-bridges
• Hydrogen-bonds
• Hydrophobic interactions
• van der Waals interactions

> define protein structure; important for functional properties

Question 17

Covalent bonds between side-chains occurs ….

Answer 17

• Occur due to oxidation of sulfhydryl groups > Disulfide bonds between Cys residues lead to formation of cystine

Question 18

Hydrogen-bonds between side-chains formed…

Answer 18

Formed between H bonded to an electronegative atom (O or N) and another electronegative atom

Question 19

Peptide bond has ________ character

Answer 19

partial double bond character
> resonance hybrid of two structures
> peptide bond is therefore planar and stable

> No rotation around the peptide bond.
Free rotation around bonds between α-carbon and its amino nitrogen and carbonyl carbon