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IMS > Proteins > Flashcards

Proteins Flashcards

1
Q

name the 6 aliphatic amino acids (AGILPV)

A

alanine, glycine, isoleucine, leucine, proline, valine

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2
Q

name the 3 aromatic amino acids (FWY)

A

phenylalanine, tryptophan, tyrosine

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3
Q

name the 2 acidic amino acids (DE)

A

aspartic, glutamic

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4
Q

name the 3 basic amino acids (RHK)

A

arginine, histidine, lysine

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5
Q

name the 2 hydroxylic amino acids (ST)

A

serine, threonine

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6
Q

name the 2 sulfur-containing amino acids (CM)

A

cysteine, methionine

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7
Q

name the 2 amidic amino acids (NQ)

A

asparagine, glutamine

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8
Q

why do amino acid chemical properties differ?

A

due to differences in R groups

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9
Q

what is overall structure/function of protein determined by?

A

physical properties e.g. size/shape

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10
Q

name the 6 categories of R groups

A 
size (large/small)
shape (aliphatic/aromatic)
hydrophobicity (polar/non-polar)
charge (acidic/basic)
sulphur containing (cysteine + methionine)
imino (proline is not an amino acid)
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11
Q

why is proline not an amino acid?

A

is an imino acid

secondary amino acid (2 carbons bonded to central N atom)

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12
Q

which amino acid does not possess optical activity?

A

glycine

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13
Q

what does it mean when an amino acid possesses optical activity?

A

chiral carbon has 4 different groups attached

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14
Q

which isomers are found of amino acids in proteins?

why?

A

only L isomer

due to specificity of enzymes active site

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15
Q

what is the amino acid charge dependent on?

A

pH dependent

amino acid can act as weak acid/base depending on pH of surrounding environment

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16
Q

when is pKa = pH

A

pKa = pH when group is 50% ionised

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17
Q

what is αlpha amino groups pKa?

A

around pH 9 (+ve charged)

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18
Q

what is pKa of histidine?

A

close to pH 6 (can be +ve or -ve charged or neutral)

can find them in active sites of enzymes acting as donors or receptors of protons

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19
Q

enzyme disease: Phenylketonuria (PKU)

cause of disease
diagnosis
treatment

A

phenylalanine hydroxylase cant break down phenylalanine, which builds up in blood/brain leading to brain damage

diagnosed by blood test when 5 days old

low protein diet, amino acid supplement, ensure person still recieving nutrients requires for normal growth

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20
Q

transport/storage disease: Sickle cell anaemia

cause of disease
symptoms
treatment

A

haemoglobin/ferritin, sickle cells contain mostly HbS type of Hb, which is harder and less flexible
causes them to get stuck in small blood vessels and block them

sickle cell crisis, higher risk of infection, anaemia

blood transfusion, antibiotics, bone marrow transplant

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21
Q

motion disease: Duchenne Muscular Dystrophy

A

genetic disorder

progressive muscle degeneration and weakness

caused by abscence of dystrophin (muscle protein)

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22
Q

cause of Type 1 Diabetes

A

pancreas produces little/no insulin

body cant turn glucose into energy

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23
Q

cause of osteogenesis imperfecta

A

disturbance to collagen:

genetic bone disorder

fragile bones, break easily = spinal cord problems, heart failure

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24
Q

cause of scurvy

A

disturbance to collagen:

vitamin C needed to make collagen
vit C deficiency leads to anaemia, exhaustion, spontaneous bleeding, pain in limbs and loss of teeth

25
Q

Cystic Fibrosis

cause
symptoms

A

genetic disorder, defect in CFTR gene, leading to faulty Cl- channels

affects lungs/digestive system
build up of sticky mucus in lungs = breathing problems and increased risk of lung infections
mucus clogs pancreas = stops enzymes reaching food in gut = less digestion

26
Q

what is Myasthenia gravis?

A

chronic autoimmune neuromuscular disease

causes muscle weakness in skeletal muscles- responsible for breathing and movement

27
Q

name the bonds are used to join amino acids.

name the reaction that takes place.

A

peptide bonds

condensation reaction (releases water molecule)

28
Q

why do peptide bonds have limited rotation?

A

they have partial double bond characteristics, making bond rigid

29
Q

what are the 2 ends of the polypeptide chain?

A

N-terminus

C-terminus

30
Q

secondary protein structure consists of which 2 structures?

A

a-helix

ß-pleated sheets

31
Q

secondary protein structure is stabilised by which bonds?

A

Hydrogen bonds between N-H and C=O groups

32
Q

how is a-helix formed in the secondary structure

A

formed by backbone of chain
H bonds occur at regular individuals along helix
each O binds to H on bond 4 residues along
gives a-helix some elasticity

33
Q

how is a ß-pleated sheet formed in secondary structure

A

stabilised by H-bonding between adjacent strands
may be between 2 parts of same chain (intrachain)
may be between 2 parts of different chain (interchain)
no elasticity
sheets can be parallel or non-parallel

34
Q

many proteins can contain both _____________ and ___________

A

αlpha helices

ß-pleated sheets

35
Q

describe the tertiary structure of a protein

A

some flexibility

forms active site of enzyme

36
Q

what are the 2 types of tertiary structure of protein

A

soluble
interior = hydrophobic, exterior = hydrophillic

insoluble
interior = hydrophillic, exterior = hydrophobic

37
Q

state structure of quartenary protein

A

several individual polypeptides (subunits)

38
Q

what is the advantage of quatenary structure of structural proteins?

give an example

A

multiple chains provide strength and rigidity (e.g. collagen)

e.g. collagen

39
Q

what is the advantage of quatenary structure of multi-enzyme complexes?

give an example

A

multiple sub-units
catalyse reactions faster –> multiple active sites for substrate to bind –> maximises efficiency

mitochondrial ATPase

40
Q

explain the forces stabilising tertiary/quatenary structure

A

disulphide bonds- covalent, strongest, oxidation between pairs of cysteine

electrostatic interactions- between opposite charged side chains (form salt bridges)

van der vaals- due to dipoles and electron density

hydrogen bonds

hydrophobic effect

41
Q

how does protein prescence cause disease?

A

high protein concentrations and presence of other molecules can interfere with correct protein folding

42
Q

how do molecular chaperones and chaperonins support effective protein folding

A

molecular chaperones- bind to short segments of protein to facilitate correct folding

chaperonins- protein barrels that provide stable space where protein can fold

43
Q

how does incorrect protein folding lead to disease?

A

results in non-functional proteins = hinder cellular process = disease symptoms

misfolding = abnormal protein deposits = accumulation of insoluble protein rich in ß-sheet structure = interfere with cell functioning = cell death

44
Q

why do amyloid diseases occur?

A

build up of amyloid in organs and tissues throughout the body

45
Q

what are prion diseases and why do they occur?

which other diseases can this lead to?

A

group of progressive neurodegnerative conditions

an infectious protein agent causes a change in normal protein

can cause Creutzfeld-Jacob disease, BSE (mad cow disease) & scrapie (sheeps & goats)

46
Q

what is Alzheimers disease?

how does it develop?

A

commonest form of dementia (memory loss, loss of language, poor judgement, confusion)

no current cure

amyloid precursor protein accumulates = insoluble fibrils of amyloid ß protein in brain = leads to plaques = damage to neurons

47
Q

what is Creutzfeldt Jacob disease?

what are the forms of CJD?

how does it develop?

A

loss of neurological function (memory loss, loss of coordination and language ability)

  1. hereditary forms exist- also associated with ingestion of an infectious agent, the prion protein (PrPsc)
  2. most common form of CJD is sporadic form (arises at random, affects older population)

PrP^(Sc)- identical primary seqeunce to normal membrane protein PrP^c but higher proportion of ß-pleated sheet

when normal PrP^c (mostly a-helical) come into contact with abnormal prions- normal proteins change structure and acquire abnormal PrP^(Sc) structure (ß-pleated sheet)

abnormal form is insoluble and resistant to breakdown by protease

48
Q

relate globular proteins to function (e.g. enzymes, haemoglobin)

A

compact, soluble (hydrophillic residues outside, hydropobic residues inside)

49
Q

relate fibrous proteins to function (e.g. keratin (hair/nails), collagen)

A

elongated, repeating amino acid sequences, insoluble due to high hydrophobic amino acid content

50
Q

relate membrane proteins to function (e.g. ion channels)

A

hydrophobic region associate directly with bilayer, hydrophillic region located internally and face aqueous solutions

51
Q

what is the structure of a normal haemoglobin molecule?

A

4 polypeptide chains held by non-covalent interactions
each chain contains one Haem group each
each Hb can bind 4 oxygens
4 chains packed together = quatenary structure

52
Q

which chains is adult haemoglobin made up of?

A

2a and 2ß chains

53
Q

why is haemoglobin an allosteric molecule?

A

binding oxygen to one of the subunits affects interaction with other subunits

54
Q

why does abnormal haemoglobin arise?

A

400 mutant Hb
95% due to single amino acid change
haemoglobinapathies caused by mutations, can be fatal or advantageous (usually inherited)

55
Q

what functions of Hb would be affected by mutation?

A 
amount of Hb synthesised
structure e.g. subunit interfaces
stability of Hb- leading to haemolytic anaemia
affinity for oxygen
affinity for regulators e.g. BPG
56
Q

Relate Haemoglobin structure to function

A

Hb carries oxygen to body cells

oxygen is sparingly soluble so needs transport/storage system

57
Q

state the structure and function of myoglobin (Mb)

A

store oxygen in tissues

globular protein make up of 8 different a-helices
hydrophobic residues inside and polar residues on surface

small- made up of 153 amino acids and very compact

contains haem prosthetic group (Fe2+) and protoporyphyrin group
tightly bound, specific non-polypeptide unit required for biological function
Fe2+ can co-ordinate with 6 ligands
4 bonds to N poryphyrin ring
1 N from proximal His (F8)
1 from O atom- O binding changes position of Fe

58
Q

where is concentration of myoglobin (Mb) the highest?

A

skeletal and cardiac muscle

59
Q

associating haem with haemoglobin does what?

A

inhibits other small molecules from binding (e.g. CO2)

IMS (4 decks)

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