Proteins Flashcards by Hannah Knowles

What are the characteristics of globular proteins

Compact
soluble
hydrophilic residues outside and hydrophobic residues hidden

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What are the characteristics of fibrous proteins

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

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

Myoglobin: O2 store
Haemoglobin: o2 transport

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What are the characteristics of myoglobin

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

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What is the haem group

tightly bound to protein

essential for biological activity

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What are the advantages of haem associating with protein molecule

Fe atoms kept in Fe2+ form

Binding of other small molecules is inhibited

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What are the characteristics of haemoglobin

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

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What if O2 affinity for Hb dependent on

pH and CO2

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What is the result of oxygen binding to Hb

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

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What is the tense state

more salt bridges between subunits so low affinity for O2

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What is the relaxed state

Fewer salt bridges so high affinity for O2

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What is the Bohr effect

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

Increased CO2 or lactic acid will lower pH

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What is BPG (bisphosphoglycerate)

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

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What are the three haemoglobin regulators

H+, CO2, BPG

They act at different sites so their effects are additive

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What are the characteristics of Foetal haemoglobin

Binds O2 more strongly than adult

2 a 2 y

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

Sickle cell anaemia

B- thalassaemia

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How can mutations affect Hb

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

Why do mutations not always cause disease

Position

Type

What is collagen

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

What are the three grouping of collagen types

fibril-forming
network-forming
fibril- associated

What is the primary structure of collagen

Gly- X- Y repeating

What is the secondary structure of collagen

Left handed helix

3.3 residues per turn

What is the quaternary structure of collagen

Triple helix

Right handed twist

What are collagenases

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

What is osteogenesis imperfecta

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

What is the relevance of enzymology to medicine

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

What are enzymes and how do they work

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

What is an assay

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

What is Michaelis constant

Km = (k2 + k3)/ k1 | Measure of the affinity of an enzyme for its substrate

What factors affect enzyme activity

Substrate conc Temperature pH Inhibitors

How do irreversible inhibitors work

covalent modification of amino acid side chains in the active site

What is the IC50

Inhibitory conc that knocks out 50% of the activity

What cofactors are essential for enzyme function

metal ions coenzyme vitamins

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

Haemolytic crisis

What is the function of protein kinases

phosphorylation of enzymes

What is the function of protein phosphatases

removal of phosphate groups

What are the four types of control of enzyme activity

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

How can enzyme presence indicate tissue damage

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

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

the half-life of enzymes in the blood stream varies

What does the unit IU mean

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