Amino Acids & Proteins

Question 1

Are fibrous proteins water soluble?

Answer 1

no

Question 2

Are globular proteins water soluble?

Answer 2

yes

Question 3

What is the role of fibrous proteins?

Answer 3

structural

Question 4

What is the role of globular proteins?

Answer 4

dynamic (e.g enzymes and receptors)

Question 5

What is an example of a part globular, part structural protein?

Answer 5

myosin

Question 6

What percentage of dry cell weight do proteins represent?

Answer 6

50%

Question 7

What is the role of proteins?

Answer 7

to perform the functions essential for life

Question 8

know the structure of an amino acid

Answer 8

Carboxyl group
Amino group
R group
H atom

Question 9

What causes the folding of proteins?

Answer 9

The hydrophobic effect (driven by the need of internalise hydrophobic polypeptide chains) (polar chains on outside, non-polar on inside)

Question 10

What is pKA?

Answer 10

PH value at which a weakly ionising group is 50% associated

Question 11

What is the role of di-sulfide bridges?

Answer 11

Hold polypeptide chains in shape

Question 12

What is the most hydrophobic amino acid?

Answer 12

phenylalanine

Question 13

What are the aromatic amino acids?

Answer 13

phenylalanine tyrosine tryptophan

Question 14

What is the primary structure?

Answer 14

linear sequence of amino acids

Question 15

What is the secondary structure?

Answer 15

regions of regularly repeating conformations of the peptide stabilised by hydrogen bonding between the peptide groups e.g alpha helices and beta sheets

Question 16

What is tertiary structure?

Answer 16

the 3D shape of the folded chain. Arrangement of all amino acids including R groups and any prosthetic groups (in a single polypeptide chain)

Question 17

What is the quaternary structure?

Answer 17

the arrangement of two or more polypeptide subunits in an oligomeric protein (multi chain only)

Question 18

How is a peptide bond formed

Answer 18

removal of O from one peptide and 2 H from the other O=C-N-H

Question 19

which amino acids have ionising side chains?

Answer 19

Asp, Glu, His, Arg, Ly, Tyr and Cys

Question 20

How do we know that ionising side chains have an affect on protein structure and function?

Answer 20

Use electrophoresis to separate proteins and amino acids at different PHs, because they carry different charges at different PHs

Question 21

How do you write an amino acid

Answer 21

C terminus first. N terminus on right

Question 22

Describe the structure of a right handed alpha helix

Answer 22

Each C=O is hydrogen bonded with the amide hydrogen of the residue 4 places ahead

Question 23

What’s an example of an alpha helix

Answer 23

Alpha keratin

Question 24

What’s an example of a beta pleated sheet?

Answer 24

virus coat proteins

Question 25

Differences between alpha helix and beta sheet?

Answer 25

Alpha helix more compact | -look at structures

Question 26

Describe the tertiary structure of Mb

Answer 26

- contains a heme group - globular - folded to be very compact (with hydrophobic on inside) - 75% of amino acids folded into a right handed alpha helix

Question 27

Why is Hb an allosteric protein?

Answer 27

It has multiple ligand binding sites

Question 28

What is the structure of Hb made up of?

Answer 28

Two molecules of alpha globin Two molecules of beta globin Tetramer organised into a pair of dimers Largely alpha helical

Question 29

What is collagen?

Answer 29

A major protein in vertebrae connective tissue (25-35% of total proteins in mammals)

Question 30

What is collagen made up of?

Answer 30

- Units of the triple stranded tropocollagen molecule. The triple helix is held together by H bonds between chains. - multiple repeats of -Gly-X-Y (where X is often proline and Y is often hydroxyproline) - Three left handed helical chains coiled around each other in a right handed supercoil

Question 31

What is an enzyme?

Answer 31

Usually a protein (can sometimes be RNA) that accelerates biological reactions

Question 32

Why are enzymes important for life?

Answer 32

- Accelerates metabolic reactions - enables regulation of metabolic reactions - integration of metabolism

Question 33

What are the biomedical applications of enzymes?

Answer 33

1. Diagnostic reagents (e.g enzymes being released into blood after tissue damage) 2. Lab reagents 3. Drug metabolism 4. Drugs work by inhibiting enzymes

Question 34

What are isozymes?

Answer 34

Tissue-specific physically distant form of an enzyme