Proteins (biomoleq)

Question 1

Amino acid structure

Answer 1

• Central C atom, NH2, H, COOH, R group
• R group/side chain physical/chemical properties determine unique characteristics
  (eg. polar/charged)
  *20 amino acids encoded by genetic code

Question 2

Peptide bonds in amino acids

Answer 2

Covalent bonds betw. aa (pri structure)
- Formed by condensation of OH & NH2
- NH2 end is N terminus, COOH end is C terminus

Question 3

Disulfide bonds (SH)

Answer 3

• Strong covalent bonds from oxidation sulfhydryl grps of CYSTEINE
• Strongest bonds (broken by RA)

Question 4

Ionic bonds

Answer 4

Strong bonds betw. charged NH3+ & COO- in R groups
(affected by pH due to neutralisation of R groups)

Question 5

Hydrophobic interactions

Answer 5

hydrophobic R groups cluster tgt to shield from aq. env.

Question 6

Hydrogen bonds

Answer 6

betw. polar grps, numerous
- stabilise secondary & tertiary structure

Question 7

Protein structure

Answer 7

primary (peptide)
secondary αhelix,βpleated sheet
tertiary (globular 3d)
quarternary (≥ 2 polyp)

Question 8

Pri structure

Answer 8

Specific sequence, no. & type held by peptide bonds (determines how it folds into sec. structure & final 3D)

aa no. 1 N terminal, last aa C terminal

Question 9

Sec structure
αhelix,βpleated sheet

Answer 9

Segments repeatedly, coiled & folded hydrogen bonds
αhelix - 1 turn every 3.6 aa
βpleated sheet - adj. parallel segments
stabile, high tensile strength, flexible, nonelastic

Question 10

tertiary structure

Answer 10

Single polp. chain further coiled, extensively folded into compact globular 3D structure
- Disulfide, ionic, hydrophobic, hydrogen bonds betw. R groups
-

Question 11

Quarternary structure

Answer 11

≥ 2 extensively coiled polyp. chains, held by, disulfide, ionic, hydrophobic, hydrogen bonds

Question 12

Globular protein

Answer 12

• Wide variety, irregular
  tertiary gives its shape
• spherical
• soluble in water
• metabolic function

Question 13

Fibrous protein

Answer 13

• Repetitive, regular
  secondary gives its shape
• long fibrils
• insoluble in water
• structural function

Question 14

Haemoglobin

Answer 14

4 seperate polyp. chains
2αhelix 2βpleated sheet
- held by ionic, hyprohobic, hydrogen
- each chain contains prosthetic haem grp, can bind to 4, Fe 2+ binds reversibly to O2 moleq
- allosteric protein, cooperative binding w O2
- Each O2 that binds causes conformational change, increase affinity for O2, each lost decreases affinity
- Take up O2 in low conx, release O2 in low conc

Question 15

Haemoglobin function

Question 16

Collagen

Answer 16

Fibrous quarternary, NO TERTIARY
- 3 polyp. chains wound to triple helix=1 tropocollagen
- each collagen polyp. chain has 1000 aa moleq loosely wound left helix
- GLYCINE every 3rd aa, allows close packing into tight coil
- linked by HYDROGEN bonds
- MANY tropocollagen lie parallel, overlap staggered, forming FIBRIL
- FIBRILS are strong cuz covalent crosslinks betw. lysines & hydroxlysines, bundle to form fibres
-

Question 17

Collagen function

Question 18

Formation & assembly of collagen fibre