Protein Structure

Question 1

What are the main classes of proteins?

Answer 1

Structural proteins - tissues and organs

Enzymes

Regulatory proteins

Question 2

What does central dogma of molecular biology state?

Answer 2

Genetic info flows from DNA TO RNA.

Question 3

Main classes of amino acids

Answer 3

Hydrophobic- have non polar chains

Hydrophilic- include uncharged amino acids

Polar charged-positively chagrd and physiological ph levels

Uncharged- they like to interact with water

Question 4

How are polar and non polar residues distributed in cytosolic protein?

Answer 4

Hydrophobic inside- protein core- non polar

Hydrophilic- polar found on surface

Question 5

What makes glycine, proline and cysteine residues so special?

Answer 5

Glycine- has small size- allows flexibility

Cysteine- disulphide bonds

Proline- helix breaker

Question 6

What is a peptide bond?

Answer 6

Amino acids are linked by peptide bonds

Question 7

What forces stabilise peptide bonds?

Answer 7

Hydrogen bonding between adjacent peptide bonds make it stable

Question 8

What is primary structure of protein and what info it contains?

Answer 8

Linear sequence of amino acids in polypeptide chain.

Information- amino acid sequence, genetic information

Question 9

What are main structures of amino acids?

Answer 9

Amino group

COOH group

Hydrogen atom

Side chain (R group )

Question 10

What bonds stabilise various elements of secondary structure ?

Answer 10

Stabilised by hydrogen bonding in alpha helix and beta sheets

Hydrophobic interactions can also increase stability- fold so hydrophobic residues in the interior away from surrounding aqueous

Question 11

How are amino acid residues organised in a helix and what ab b sheets?

Answer 11

Alpha helix - amino acid residues arranged in helix- with backbone of polypeptide chain- hydrogen bonds form between carbonyl oxygen and amine hydrogen of amino acid residue

Beta sheets- flat sheet like- polypeptide chains forming strands that run parallel- strands run in same directions- LESS STABLE

or anti parallel- run in opposite directions- MORE STABLE

Held by hydrogen bonding between C=O and N-H

Question 12

What is the tertiary structure of proteins and what bonds stabilise it?

Answer 12

3 dimensional structure

Hydrophobic interactions- clustering of hydrophobic groups away from water- and van der waals interactions- between non polar groups

Hydrogen bonds- can form between polar or charged groups on different parts of polypeptide chain

Has covalent disulphide bonds- between 2 cysteine residues linking different parts of peptide chains together

Ionic interactions- between + and - charged amino acid residue- can form salt bridges between oppositely charged groups

Question 13

What is the quartenary structure of proteins and what bonds stabilise it?

Answer 13

Arrangement of multiple polypeptide chains

Interactions between side chains- Same as tertiary structures

Question 14

What is the difference between protein subunits and protein domains?

Answer 14

Protein subunits - individual polypeptide chains to form larger protein, subunits may be identical or different (hemoglobin,collagen, ribosome)

Protein domains- distinct structures and functional units with SINGLE POLYPEPTIDE CHAIN
Independently folded regions can be identified based on sequence structure
Specific binding sites, can be repeated and shared amongst proteins

Question 15

What does the theory of protein shuffling state?

Answer 15

States that modular nature of proteins arose through recombination of genetic material.

Question 16

What are enzyme co factors?

Answer 16

Are molecules or ions that are required for proper functioning of enzymes. Assist enzymes in catalysing biochemical reactions- catalytic processes helping enzyme Maintain proper structure

Question 17

Main features of active site ?

Question 18

What are main differences between lock and key and induced fit models?

Answer 18

The lock and key model portrays enzyme-substrate interaction as a rigid, complementary fit

the induced fit model suggests dynamic structural adjustments in both enzyme and substrate upon binding.

Question 19

What is 3 point attachment model?

Answer 19

describes how enzymes bind to substrates at specific sites, involving interactions at three key points, leading to efficient catalysis.

Question 20

What mutation leads to sickle cell anemia? And what changes does it cause in haemoglobin protein structure ? What are the consequences ?

Answer 20

Sickle cell anemia is caused by a point mutation in the HBB gene

This mutation alters the protein’s structure, causing hemoglobin molecules to form long, rigid fibers instead of maintaining their normal biconcave shape

red blood cells become distorted into a sickle shape, leading to blockages in blood vessels, reduced oxygen delivery to tissues, chronic anemia etc

Question 21

What enzyme is mutated in gouchers disease and type of mutations called lead to this disease and what molecular and clinical consequences of this disease?

Answer 21

mutations in the GAA gene encoding the lysosomal enzyme alpha-glucosidase (acid maltase). These mutations typically result in the deficiency or dysfunction of alpha-glucosidase enzyme activity

missense mutation, which leads to the production of a dysfunctional enzyme.

results in progressive muscle weakness, hypotonia, respiratory distress, cardiomyopathy, and hepatomegaly.