Protein Structure

Question 1

4 protein structures

Answer 1

1 primary
2 secondary
3 tertiary
4 quartenary

Question 2

Primary structure and direction of sequence writting

Answer 2

• protein sequence made from amino acid residues by covalent polymerization at COOH and NH2 ends
• sequence written in N to C directon

Question 3

Properties of peptide bond

Answer 3

• partial C-N double bond restriction of rotation at bond but not other atoms
• bond unchanged but polar so reactions occurs via R groups

Question 4

Secondary structure and t ypes

Answer 4

-folding of segments of polypeptide to form a-helix or B-sheet

Question 5

A-helix, direction of r groups, number of residues present and what stabilises

Answer 5

• spiral structure of tingly coiled polypeptide core with R groups extending outwards from central axis to avoid interfering with each other
• stabilized by H2 bonding between peptide bond carbonyl and amide hydrogens part of backbone
• H2 bonding parallel to axis and extend from carbonyl oxygen to peptide 4 residues ahead

Question 6

How many amino acids in each turn

Answer 6

-36 residues in each turn

Question 7

Amino acids which disrupt helix

Answer 7

• Proline ( imino acid ) inserts kink in chain as it is not compatible with spiral
• charged amino acids : lysine ( forms electrostatic bonds which interfere with each other )
• bulky aas - can interfere if present in large numbers

Question 8

B - sheet and diagram presentation

Answer 8

• presented as broad arrow
• all peptides involved in H2 bonding and surface appears pleated
• can be one strand turning back on itself or 2 or more stands

Question 9

Types of B sheets

Answer 9

• parallel
• antiparallel
• mixed

Question 10

B turns

Answer 10

• 4 amino acids which turn a strand around
• can connect A and B together
• 1st amino H2 bond to 4th
• Proline present. Provides the kink

Question 11

Motifs ( secondary structure ) what connects them and function

Answer 11

• combination of secondary structures producing specific geometric patterns
• connected by loops and form cores of molecules

Question 12

Types of motifs

Answer 12

• a-a
• B-a-B
• B meander

( - means connected by loop )

Question 13

Tertiary structure

Answer 13

-folding of domains and final arrangement of domains in polypeptides

Question 14

Domains

Answer 14

• fundamental functional 3D structure units of poly peptides
• combination of motifs
• they fold differently and thus are structurally independent of one another

Question 15

Interactions stabilizing tertiary proteins

Answer 15

• H2 bonding
• Dipole dipole
• Van Der Waals
• disulfide bonds

Question 16

Denatured proteins without ATP and causes

Answer 16

• unfolding and disorganization of proteins without Hydrolysis
• caused by heat , strong acids or bases

Question 17

Chaperone proteins functions and types

Answer 17

• interact with polypeptides at various stages until folding is complete
• bind hydrophobic regions of extended proteins and keep proteins unfolded until synthesis is compete
• others form 2 ring stacked cage. Partially folded protein enters cage binds central cavity and released
• they facilitate correct folding, prevent premature folding by binding and stabilizing exposed aggregation prone hydrophobic regions of polypeptides
• also called heat shock proteins

Question 18

Quaternary structure

Answer 18

• arrangement of polypeptides subunits held by non covalent forces
• subunits may function independently

Question 19

Isoforms and isozymes

Answer 19

• proteins with same function but different structure

- enzymes with same function different structure