Protein Structure And Function

Question 1

Function of amino acids

Answer 1

Make up proteins

Question 2

Amino acid functional groups

Answer 2

Carboxylic acid
Amine (nh2)

Question 3

What is a zwitterion

Answer 3

Possesses both positive and negative negative charges simultaneously creating a molecule which overall bears no net charge

Question 4

What happens to the carboxylic acid of the amino acid with increasing ph

Answer 4

Deprotonated
NH3+ AND COO-

Question 5

What is the isoelectric point

Answer 5

Point at which amino acid has no net charge

Question 6

Enantiomers

Answer 6

Non superimposable mirror images

Question 7

What are the 4 R groups of amino acids

Answer 7

Hydrophobic
Hydrophilic
Acidic
Basic

Question 8

Bonds between peptides and proteins

Answer 8

Amide/peptide bonds between amino acid monomers in a condensation reaction

Question 9

What are the levels of protein structure

Answer 9

Primary- amino acid sequence
Secondary- 3D structure formed by hydrogen bonds
Tertiary- 3D structure formed by non covalent interactions and disulphide bonds
Quaternary- association of multiple polypeptide subunits

Question 10

What are the ends of the amino acids in a polypeptide chain called

Answer 10

N- terminus to C-terminus

Question 11

Types of secondary structures

Answer 11

Alpha helix
Beta pleated sheets

Question 12

Explain beta pleated sheets

Answer 12

Hydrogen bonds form between peptide chains next to each other in the sheet
Parallel= hydrogen bonds to each other run in the same direction
Anti parallel = peptide chain run in opposite directions

Question 13

Explain beta pleated sheets

Answer 13

Hydrogen bonds form between peptide chains next to each other in the sheet
Parallel= hydrogen bonds to each other run in the same direction
Anti parallel = peptide chain run in opposite directions

Question 14

Tertiary structure

Answer 14

Folded structure of polypeptide chain to form a 3D shape with noncovalent and covalent interactions
Non covalent= ionic, hydrogen, hydrophobic and London
Covalent= disulphide

Question 15

Describe disulphide bonds

Answer 15

Covalent single bonds between 2 cysteines
INTRAmolecular= within a single polypeptide chain
INTERmolecular= between different polypeptide chains

Question 16

Quaternary structure

Answer 16

Two or more polypeptides with non covalent interactions
Each polypeptide is called a subunit and the protein is called oligomeric

Question 17

List the 7 protein functions

Answer 17

1) catalysis= enzyme
2) genomic= dna associated proteins (histones) that regulate chromosome structure and gene expression
3) defence= proteins(antibodies) to fight infection
4) movement= contractile proteins (actin and myosin) for muscle contraction
5) structure= proteins which define cell shape and support tissues (collagen and elastin)
6) transport= proteins which carry molecules around body (haemoglobin) and membrane proteins that control transport in and out of cell
7) signalling= hormones which convey signals between cells and receptors which receive signals

Question 18

Protein + what binds? + where does it bind?

Answer 18

Enzyme + substrate + active site
Receptors + ligand + binding site
Antibody + antigen + binding site

Question 19

What are enzymes

Answer 19

Catalyse chemical reactions
Lowers activation barrier

Question 20

Role of histone genomic protein

Answer 20

Condense nuclear dna into chromatin
Positive charge on histones neutralises the negative charge on dna which enables it to pack closely together to fit into the nucleus

Question 21

Structure of antibodies

Answer 21

Quaternary structure held by disulphide bonds
Antigen binding site is variable between different antibodies

Question 22

Role of movement proteins (actin and myosin)

Answer 22

Head groups on myosin use energy from atp hydrolysis to form and break bonds with actin filaments
Myosin slide alongs actin filament= muscle contraction

Question 23

Role of structural proteins (collagen)

Answer 23

Long fibre of insoluble protein
Each strand is a alpha helix and wind together to form a fibre
Cross links with lysine side chains= ‘super secondary structure’

Question 24

Sickle cell anaemia

Answer 24

Mutation in the beta subunits
Causes haemoglobin to aggregate
Sickle shape
Block narrow blood vessels and interfere with blood flow

Question 25

Denaturation

Answer 25

Loss of tertiary and secondary structure in a protein
E.g. heat, ph extremes, uv, heavy metals
Hydrogen bonf]do break and weakens non covalent interactions