Proteins

Question 1

What are the characteristics of globular proteins

Answer 1

Compact
soluble
hydrophilic residues outside and hydrophobic residues hidden

Question 2

What are the characteristics of fibrous proteins

Answer 2

Elongated
repeating amino acid sequences
insoluble due to high hydrophobic amino acid content

Question 3

What are the two oxygen binding proteins and what are their functions

Answer 3

Myoglobin: O2 store
Haemoglobin: o2 transport

Question 4

What are the characteristics of myoglobin

Answer 4

highest conc in skeletal and cardiac muscles
small protein
contains haem prosthetic group
Globular protein
8 alpha- helices

Question 5

What is the haem group

Answer 5

tightly bound to protein

essential for biological activity

Question 6

What are the advantages of haem associating with protein molecule

Answer 6

Fe atoms kept in Fe2+ form

Binding of other small molecules is inhibited

Question 7

What are the characteristics of haemoglobin

Answer 7

Four polypeptide chains, containing a haem group each, held together by non-covalent interactions, in a tetrahedral array with overall spherical shape, quaternary structure
Adult: 2 a and 2 B chains

Question 8

What if O2 affinity for Hb dependent on

Answer 8

pH and CO2

Question 9

What is the result of oxygen binding to Hb

Answer 9

Alters tertiary and quaternary structure

when one subunit is bound to oxygen the altered shape allows for an increased affinity to oxygen for the other subunits

Question 10

What is the tense state

Answer 10

more salt bridges between subunits so low affinity for O2

Question 11

What is the relaxed state

Answer 11

Fewer salt bridges so high affinity for O2

Question 12

What is the Bohr effect

Answer 12

If pH goes down then decrease of affinity of Hb for O2

Increased CO2 or lactic acid will lower pH

Question 13

What is BPG (bisphosphoglycerate)

Answer 13

BPG decreases affinity of Hb for O2 so causing more oxygen to be released in high altitude and hypoxia where BPG levels are high

Question 14

What are the three haemoglobin regulators

Answer 14

H+, CO2, BPG

They act at different sites so their effects are additive

Question 15

What are the characteristics of Foetal haemoglobin

Answer 15

Binds O2 more strongly than adult

2 a 2 y

Question 16

What are two inherited disorders which affect haemoglobin synthesis, structure and function

Answer 16

Sickle cell anaemia

B- thalassaemia

Question 17

How can mutations affect Hb

Answer 17

Amount synthesised
structure
stability of Hb
affinity for O2
affinity for regulators

Question 18

Why do mutations not always cause disease

Answer 18

Position

Type

Question 19

What is collagen

Answer 19

Family of fibrous proteins
insoluble fibres
high tensile strength
At least 12 different types of collagen
Always consists of three strands

Question 20

What are the three grouping of collagen types

Answer 20

fibril-forming
network-forming
fibril- associated

Question 21

What is the primary structure of collagen

Answer 21

Gly- X- Y repeating

Question 22

What is the secondary structure of collagen

Answer 22

Left handed helix

3.3 residues per turn

Question 23

What is the quaternary structure of collagen

Answer 23

Triple helix

Right handed twist

Question 24

What are collagenases

Answer 24

Enzymes used in growth, tissue remodelling, tissue repair by breaking down collagen

Question 25

What is osteogenesis imperfecta

Answer 25

A range of inherited disorders characterised by increases risk of bone fractures
mutations in type 1 collagen
spontaneous mutation
severity depends on nature of mutation

Question 26

What is the relevance of enzymology to medicine

Answer 26

drug action
biochemical defects in enzymes underlie disease
clinical diagnosis/prognosis

Question 27

What are enzymes and how do they work

Answer 27

Biological catalysts of chemical reactions
Specific action on particular substrates
increase rate at which equilibrium is reached but do not shift the position of equilibrium

Question 28

What is an assay

Answer 28

A procedure for measuring the biochemical or immunological activity of a sample

Question 29

What is Michaelis constant

Answer 29

Km = (k2 + k3)/ k1

Measure of the affinity of an enzyme for its substrate

Question 30

What factors affect enzyme activity

Answer 30

Substrate conc
Temperature
pH
Inhibitors

Question 31

How do irreversible inhibitors work

Answer 31

covalent modification of amino acid side chains in the active site

Question 32

What is the IC50

Answer 32

Inhibitory conc that knocks out 50% of the activity

Question 33

What cofactors are essential for enzyme function

Answer 33

metal ions
coenzyme
vitamins

Question 34

What happens if you have a G6PDH deficiency and are exposed to drugs which produce free radicles

Answer 34

Haemolytic crisis

Question 35

What is the function of protein kinases

Answer 35

phosphorylation of enzymes

Question 36

What is the function of protein phosphatases

Answer 36

removal of phosphate groups

Question 37

What are the four types of control of enzyme activity

Answer 37

Inhibition (reversible or irreversible)
Feedback regulation
Covalent modification
Proteolytic activation

Question 38

How can enzyme presence indicate tissue damage

Answer 38

reduced levels of secreted enzymes in blood indicate damage to secreting tissues
Presence of intracellular enzymes in serum indicates tissue damage

Question 39

Why is time after injury crucial for using enzymes as indicators for damaged cells

Answer 39

the half-life of enzymes in the blood stream varies

Question 40

What does the unit IU mean

Answer 40

measure of enzyme activity

1 IU is the amount of activity that will convert 1 micromole of substrate per minute under standard defined conditions