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BM210 > Block 2 > Flashcards

Block 2 Flashcards

1
Q

what is chiral

A

four different groups are bonded to the tetrahedral alpha carbon

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2
Q

which isomer is found in protein

A

L

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3
Q

what do free amino acids in solution at neutral pH exist as

A

dipolar ions

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4
Q

what groups are charged

A

amino group and carboxyl group

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5
Q

proline

A

(P), non-polar R group

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6
Q

leucine

A

(L), non-polar R group

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7
Q

methionine

A

(M), non-polar R group

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8
Q

isoleucine

A

(I), non-polar R group

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9
Q

glycine

A

(G), non-polar R group

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10
Q

alanine

A

(A), non-polar R group

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11
Q

valine

A

(V), non-polar R group

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12
Q

phenylalanine

A

(F), non-polar aromatic R group

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13
Q

tryptophan

A

(W), non-polar aromatic R group

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14
Q

serine

A

(S), polar R group

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15
Q

thereonine

A

(T), polar R group

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16
Q

cyteine

A

(C), polar R group

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17
Q

asparagine

A

(N), polar R group

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18
Q

glutamine

A

(Q), polar R group

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19
Q

lysine

A

(K), positively charged polar R group

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20
Q

arginine

A

(R), positively charged polar R group

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21
Q

aspartate

A

(D), negatively charged polar R group

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22
Q

glutamate

A

(E), negatively charged polar R group

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23
Q

histidine

A

(H), positively charged polar aromatic R group

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24
Q

tyrosine

A

(Y), polar aromatic R group

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25
Q

what is primary structure

A

amino acid sequence of a protein

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26
Q

what is secondary structure

A

the three-dimensional structure formed by hydrogen bonds between peptide and CO groups of amino acids that are near one another in the primary structure

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27
Q

secondary structure examples

A

alpha helices, beta sheets and turns

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28
Q

what is alpha helix

A

tightly-coiled rod-like structure, with R groups sticking out from the axis of the helix

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29
Q

what is beta sheets

A

formed by adjacent beta strands, stabilised by hydrogen bonds between the polypeptide strands

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30
Q

what is tertiary structure

A

the spatial arrangement of amino acids that are far apart in the primary structure and it refers to the pattern of disulphide bond formation

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31
Q

what are myoglobin

A

very compact, the interior consists mainly of hydrophobic amino acids, and the exterior consists pf charged and polar amino acids

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32
Q

what are motifs

A

combinations of secondary structures that are found in many proteins, some proteins have two or more similar or identical compact structures called domains

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33
Q

what is the quaternary structure

A

proteins that are composed of multiple polypeptide chains

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34
Q

post-translational modification

A

converting a proprotein by proteolytic cleavage to a mature protein. addition of various chemical groups modifying the: N-terminal amino group, C-terminal carboxyl group, side chains of amino acids throughout the length of the protein

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35
Q

what can the lack of appropriate protein modification

A

pathological conditions

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36
Q

what does an enzyme do

A

Lowers the activation energy, increased rate of reactions, not consumed in the reaction, does not affect the equilibrium

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37
Q

what are the properties of the active site

A

positioning of substrate molecules in the most favourable relative orientation for the reaction to occur, perfectly complementary to the transition state, amino acid side chains of the active site stabilise the electron distribution of the transition state

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38
Q

Oxidoreductases

A

oxidation and reduction reactions Dehydrogenases- addition or removal of two-electron transfer to O2 forming H2O2.
Oxygenases- two-electron transfer to ½ O2 forming H2O incorporate O2 into product
Hydroxylases- incorporate ½ O2 into product as -OH and form H2O Peroxidases- use as H2O2 as oxygen donor, forming H20

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39
Q

Transferases

A

transfer a chemical group from one substrate to another
Kinases- transfer phosphate from ATP onto the substrate

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40
Q

Hydrolases

A

hydrolysis is water spliting the bond of C-O, C-N, O-P and C-S bonds

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41
Q

Lyases

A

addition across a carbon-carbon double bond

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42
Q

Isomerases

A

intramolecular rearrangements

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43
Q

synthetases

A

formation of bonds between two substrates frequently linked to the utilisation of ATP

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44
Q

what does ionisation state vary with

A

pH in solution

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45
Q

where is rotation permitted in the amino acid chain

A

N-C bond

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46
Q

why do chemical reactions proceed faster at higher temperatures

A

molecules move faster so they have a greater chance of colliding, electrons gain activation energy easier

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47
Q

what happens when an enzyme is denatured

A

loss of hydrogen bonding, unfolding, precipitation, loss of activity

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48
Q

what does high Km correspond to

A

low affinity for substrate

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49
Q

what does low Km correspond to

A

high affinity for substrate

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50
Q

what is an enzyme inhibitors

A

Decrease the enzyme’s ability to bind substrate, Lower the enzyme’s catalytic activity

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51
Q

reversible inhibitors

A

non-covalent (equilibrium) binding to enzyme, many are relatively unspecific, mechanism: blocking substrate binding or hindering catalytic steps

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52
Q

irreversible inhibitors (inactivators)

A

bind to enzyme covalently (“suicide inhibitor”), many are substrate analogues, undergo part of reaction, transition state covalent intermediate does not break down

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53
Q

competitive inhibitors

A

competes with the substrate for binding at the active site, inhibition is a function of the relative affinities of the substrate and the inhibitor for binding the enzyme, inhibition is a function of the relative concentrations of substrate and inhibitor

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54
Q

mixed inhibitors

A

Mixed inhibitors do not bind in the active site, Inhibitor can bind prior to substrate or to the enzyme-substrate complex, Mixed inhibitors distort the substrate binding site, which affects: apparent substrate affinity, catalytic turn-over (slowing catalysis), Mixed inhibitors can either increase or decrease Km and decrease Vmax

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55
Q

non-competitive inhibitor

A

It binds to the enzyme at a position separate from the active site, No competition for binding with the substrate, The apparent affinity for the substrate is unchanged, but the rate of reaction is slowed

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56
Q

allosteric inihibitor

A

increase Km and hence lower the apparent affinity of the enzyme for its substrate, decease in the substrate affinity leads to a decrease of enzyme activity

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57
Q

how are sugar alcohols formed

A

reduction of the aldehyde group of glucose to a hydroxyl group.

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58
Q

what is dehydrogenase

A

addition or removal of two-electron transfer to O2 forming H2O

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59
Q

what is oxygenases

A

two-electron transfer to 1/2 O2 forming H2O incoporate O2 into product

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60
Q

what is hydroxylases

A

incorporate 1/2. O2 into product as -OH and form H2O

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61
Q

what is peroxidases

A

use as H2O as oxygen donor forming H2O

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62
Q

what is transferases

A

transfer a chemical group from one substrate to another
kinases- transfer phosphate from ATP onto substrate

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63
Q

what is hydrolyses

A

water splits the bond of C-O, C-N, O-P, C-S

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64
Q

what is lyases

A

addition across a carbon-carbon double bond

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65
Q

what is isomerases

A

intramolecular rearrangements

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66
Q

what is synthetases

A

formation of bonds between two substrates frequently linked to utilisation of ATP

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67
Q

what is a disaccharide

A

condensation between two monosaccharides

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68
Q

what is an oligosaccharide

A

three to ten monosaccharides

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69
Q

what are intrinsic sugars

A

sugars contained within cell walls

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70
Q

what are extrinsic sugars

A

sugars that are free in solution

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71
Q

what is sucrose made from

A

one glucose and one fructose

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72
Q

what is lactose made from

A

one glucose and one galactose

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73
Q

what is maltose made from

A

two glucoses

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74
Q

what do saturated molecules contain

A

no double bonds

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75
Q

what do unsaturated molecules contain

A

double bonds

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76
Q

what are the eight functions of proteins?

A
  • catalysts
  • transport molecules
  • storage
  • mechanical support
  • immune protection
  • movement
  • transmission of nerve impulses
  • growth and differentiation
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77
Q

what two mirror image forms do amino acids exist as and where are they found?

A

L isomer (found in proteins) and D isomer (not in proteins)

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78
Q

what kind of ions do amino acids exist as in solution at a neutral pH?

A

dipolar

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79
Q

what two groups on the amino acid are charged?

A

carboxyl (COO-) and amine group (NH3+)

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80
Q

what can the unique side chains of amino acids vary in?

A

size, shape, charge, hydrogen bonding capacity, hydrophobic character and chemical reactivity

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81
Q

what does a change in pH do to the charge of the amino acids?

A
  • acidic pH - more positive charge (both groups protonated)
  • alkali pH - more negative charge (both groups deprotonated)
  • neutral pH - no charge (Zwitterionic form)
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82
Q

what is the difference between non polar and polar R groups?

A
  • non polar - rich in CH2 groups, hydrophobic
  • polar - hydrophillic
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83
Q

what is an aromatic R group?

A

polar or non polar benzene ring

84
Q

explain peptide-bond formation

A
  • condensation reaction releasing water
  • carboxyl group and amino acid group link to form peptide bond
85
Q

what are four features of primary protein structure and how many amino acids are found per protein?

A
  • amino acid sequence
  • polarity
  • disulfide bonds/ bridges
  • peptide bonds
  • 50 - 2000
86
Q

what is the amino terminal end?

A

the beginning of a polypeptide chain

87
Q

what is the variable part of primary structure?

A

distinctive amino acid side chains

88
Q

what is the molecular weight for an amino acid?

A

110g mol-1, 1 Dalton=1gmol-1

89
Q

what are disulfide bonds/bridges?

A
  • cross linked polypeptide chain
  • formed by oxidation of 2 cysteines (crosslinked=cystine)
  • important for insulin function (pre molecule) as it provides stability
90
Q

what are peptide bonds?

A
  • planar (C alpha, C, O, N, H, C alpha)
  • partial double bond character - resonance, so rotation around bond prohibited
91
Q

what form of peptide bonds is favoured and why?

A

trans form as steric clashes arise in the cis form

92
Q

where is rotation permitted and what does this allow?

A
  • about the N-C alpha bond (phi bond) and C alpha carbonyl bond (the psi bond)
  • allows protein folds in many ways
93
Q

what are the principles of protein folding?

A
  • complete freedom means no protein folds
  • possible because restrictions by the ridged of the peptide bond, restricted set of allowed psi and phi angles (steric hinderance)
94
Q

name the five properties of secondary structure

A
  • three dimensional
  • hydrogen bonds between peptide NH and CO groups
  • near each other in amino acids in primary structure
  • alpha helices, beta strands and turns
  • hydrogen bond between amino acid i and i+4
95
Q

explain the structural features of alpha helices

A
  • tightly-coiled and rod-like
  • R groups stick out from axis
  • all CO and NH groups on backbone form H bonds except those at the end of the helix.
  • coiled
  • stabilised by intrachain H bonds
  • right-handed (winds around)
96
Q

what are beta sheets formed by? and how are the side chains placed?

A

adjacent beta strands that have side chains alternating above and below the plane

97
Q

what is the difference in beta sheets and beta strands formation?

A

beta strands - can be parallel, antiparallel or mixed
beta sheets - can be flat or twisted

98
Q

what do hairpin turns and omega loops do?

A

change the direction of the polypeptide

99
Q

tertiary structure refers to the pattern of ……….., and the ….. is linked by …….

A
  1. disulfide-bond formation
  2. cysteine
  3. disulfide bridges
100
Q

what is tertiary structure?

A

the spatial arrangement of amino acids, far apart in primary structure

101
Q

the interior of globular proteins consist mainly of …….. amino acids. The exterior of globular proteins consists of …… and …… amino acids

A
  1. hydrophobic
  2. charged
  3. polar
102
Q

how does a pore form in the middle of a membrane protein?

A
  • lots of beta strands that consist of lipids, as membrane proteins have the reverse distribution of hydrophillic and hydrophobic amino acids
103
Q

what is a motif and a domain?

A

motif - super secondary structure, combos of secondary structure found in many proteins
domain - proteins that have two or more similar or identical compact structures (bigger)

104
Q

true or false? cell surface protein CD4 consists of 6 similar domains

A

false - consists of 4

105
Q

what is the function of beta-mercaptoethanol?

A
  • reduces disulfide bonds
  • is oxidised forming dimers
  • need long polypeptide chains
  • separation of proteins according to size
  • unfolds and opens up disulfide bridges
106
Q

name five qualities of quaternary structure

A
  • proteins composed of multiple polypeptide chains (subunits)
  • can be as simple as two identical polypeptide chains or as complex as dozens of different polypeptide chains.
  • 2 alpha subunits and 2 beta subunits
  • contains heme group
  • NEED SUBUNITS TO ACHIEVE QUATERNARY STRUCTURE
107
Q

what are the relative frequencies of amino acid residues in secondary structure? (name as many as possible)

A
  • Glu, Ala, Leu, Met, Gln, Lys, Arg, His —> alpha helix
  • Val, Ile, Tyr, Cys, Trp, Phe, Thr —-> beta sheets
  • Gly, Asn, Pro, Ser, Asp —-> reverse turns
108
Q

Trp repressor has VDLLKN on the ……
Class I histocompatibility complex has VDKLLN on the ……

A
  1. alpha helix
  2. beta strand
109
Q

lymphotactin exists in …. conformations, which are ……

A
  1. 2
  2. in equilibrium
110
Q

what are post-translational modifications?

A
  • converts a proprotein (eg. insulin) by proteolytic cleavage to a mature protein
  • the addition of various chemical groups modifying the: N-terminal amino group, the C-terminal carboxyl group and the side chains of amino acids throughout the length of the protein.
111
Q

what can a lack of appropriate protein modification result in?

A

pathological problems

112
Q

what can a lack of hydroxylation of proline in collagen result in?

A

scurvy (vitamin C deficiency)

113
Q

what can a lack of carboxylation of clotting proteins result in?

A

haemorrhaging (vitamin K deficiency)

114
Q

name five examples of post-translational modifications (not exhaustive)

A
  • chemical groups like hydroxyl, carboxyl, methyl, acetyl or phosphate
  • small proteins like ubiquitin (ubiquitinylation)
  • fatty acids like myristoyl or prenyl groups
  • branched glycosylations
  • glycosyl phosphatidyl inositol (GPI) anchors
115
Q

CaaX consensus with “C” being ….. , “X” being the ….. and “a” being any …..

A
  1. cysteine
  2. C-terminal amino acid
  3. amino acid
116
Q

what do lipid groups allow?

A

attachment

117
Q

what are five properties of catalysts?

A
  • lowers activation energy
  • accelerates chemical reaction
  • increases rate
  • is not consumed in reaction
  • does not affect equilibrium
118
Q

what are the three stages to an enzyme catalysed reaction?

A

Enz+S <–> Enz-S <–> Enz-P <–> Enz+P

119
Q

what are the two outcomes of a substrate being strained on the active site?

A
  • lowers activation energy
  • increases reaction rate
120
Q

in what three ways can enzymes catalyse a reaction?

A
  • donating or withdrawing electrons
  • stabilising or generating free radical intermediates
  • forming temporary covalent bonds (a transition state intermediate)
121
Q

what are the two methods of substrate-enzyme binding?

A
  • lock and key
  • induced fit
122
Q

what are three types of cofactors?

A
  • metal groups (hexokinase Mg2+)
  • prosthetic groups (covalently bound organic molecules (heme, lipoic acid))
  • coenzyme (tightly but not covalently bound organic molecule (NAD)
123
Q

what three factors are vital of the substrate for specificity?

A
  • shape
  • charge
  • conformation
124
Q

what are six classes of enzyme and the reaction they catalyse?

A
  • oxidoreductases - reduction and oxidation (redox)
  • transferases - transfer chemical group from one substrate to another
  • hydrolases - hydrolysis
  • lyases - addition across a carbon-carbon double bond
  • isomerases - intramolecular rearrangements
  • synthetases - formation of bonds between two substrates
125
Q

what is 1 enzyme unit (EU) equivalent to?

A

1 microliter min-1 (product formed)

126
Q

what is specific activity and what does it indicate?

A
  1. activity of an enzyme per mg of total protein in enzyme preparation
  2. purity of enzyme
127
Q

what is specific activity and what does it indicate?

A
  1. activity of an enzyme per mg of total protein in enzyme preparation
  2. purity of enzyme
128
Q

for what three reasons is a curve hyperbolic? (rate decreasing)

A
  • accumulation of product
  • depletion of substrate
  • denaturation of enzyme
129
Q

for meaningful quantitative assays of enzyme activity, ……… (……) must be measured

A
  1. initial velocities
  2. V0: reaction rates
130
Q

what are five factors affecting enzyme activity?

A
  • pH
  • temperature
  • enzyme concentration
  • substrate
  • enzyme covalent modification
131
Q

does an increase in [E] always result in a linear increase in rate? Why or why not? (hint - dimerisation)

A

no
- increase enzyme - enzyme dimer active, monomer inactive, low activity, dimer dissociates at low concentration
- increase enzyme - active monomer, enzyme dissociates to less active dimer at high concentration

132
Q

how is the Michaelis constant (Km) calculated

A

concentration of substrate at 1/2 Vmax (maximum velocity)

133
Q

what is the Michaelis-Menten equation and what does it describe?

A

v = Vmax[S]/Km+[S]
describes dependence of rate of reaction on concentration of substrate at steady state and vast molar excess

134
Q

A high Km indicates 1/2 Vmax is a …… concentration, and corresponds to …… substrate affinity
A low Km indicates 1/2 Vmax is a ….. concentration, and corresponds to ….. substrate affinity.

A
  1. higher
  2. low
  3. lower
  4. high
135
Q

if a reaction has low Km and high [S], how will it proceed and how will small changes in [S] affect the rate?

A

proceeds at maximum rate
rate is not affected

136
Q

in reactions with high Km, small changes in [S] can ……

A

cause large changes to rate

137
Q

When considering reactions with two substrates, which type of reaction may result in converging lines on a lineweaver - Burk double reciprocal graph?

A

sequential reaction - each substrate binds in turn

138
Q

what is an allosteric enzyme?

A

An enzyme that changes its conformation upon binding of an effector, resulting in a change in binding affinity at the active site

139
Q

On a graph plotting [S] against rate, what type of curve will an allosteric enzyme show ? Why ?

A

sigmoidal - when in a multi-subunit complex, binding of a substrate to the active site of the first subunit leads to change in conformation facilitating binding of substrate to other active sites

140
Q

what is covalent modulation in enzymes?

A

involves the addition/removal of covalent bonds resulting in structural changes that can allow or prevent substrate binding

141
Q

What are the differences between reversible & irreversible inhibitors?

A

reversible - non-covalent binding to enzyme, unspecific, blocks substrate binding or hindering catalytic steps
irreversible - binds to enzyme covalently (suicide inhibitor), substrate analogues, undergo part of reaction, transition state covalent intermediate doesn’t break down

142
Q

how do competitive inhibitors act?

A

competes with substrate for binding of active site, functions of relative affinities and concentrations

143
Q

How are Km & Vmax affected by competitive inhibition ?

A

Km - increased
Vmax - unchanged

144
Q

How are Km and Vmax affected by pure, non-competitive inhibition?

A

Km - unchanged
Vmax - decreased

145
Q

How are Km & Vmax affected by mixed, non-competitive inhibition?

A

Km - increased
Vmax - decreased

146
Q

what are four functions of carbohydrates?

A
  • coating of cell surfaces
    -modification of secreted proteins
  • part of receptors for a variety of pathogens
  • form the basis of human blood groups
147
Q

what are the names of the sugars with carbon numbers from three to seven?

A

3 - triose
4 - tetroses
5 - pentoses
6 - hexoses
7 - heptoses

148
Q

what is a general formulae for sugars?

A

(CH2O)n (n is between 3 and 7)

149
Q

which part of sugars makes them reactive?

A

carbon-oxygen double bonds

150
Q

what is ring-chain tautomerism and the mechanism behind it?

A
  • conversion of an open chain sugar to its ring form
  • occurs via nucleophilic attack of the C1 carbon by the C5 carbon hydroxyl group
151
Q

what is a hemiacetal?

A

a molecule with a C attached to a -OH and -O group

152
Q

how can alpha and beta forms of hemiacetals be distinguished and which form is generally more stable? and why?

A
  • in alpha forms the hydroxyl group on C1 points down from the plane of the ring whilst on beta forms it points up
  • beta forms are generally more stable, as the -OH group is “out of the way” of the other groups
153
Q

what is the name of the process by which alpha and beta forms exchange between each other?

A

mutarotation

154
Q

what is the ketone equivalent of hemiacetals?

A

hemiketals (five membered rings, furanoses)

155
Q

how is a sugar alcohol formed?

A

reduction of an aldehyde group to a hydroxyl group

156
Q

for what two reasons can a monosaccharide be joined to an alcohol, amine or phosphate group?

A
  • to form signalling molecules
  • facilitate the molecules metabolism
157
Q

under what three circumstances is an O-glycosidic bond formed?

A
  • between a sugar and an alcohol
  • between two sugars
  • between a sugar and a protein
158
Q

what three things does phosphorylation do to a sugar?

A
  • makes sugars anionic (not charged, can leave the cell)
  • traps sugars within the cell)
  • creates a reactive intermediate of sugar metabolism
159
Q

what type of reaction forms a disaccharide?

A

condensation (between two monosaccharides)

160
Q

what is the difference between intrinsic and extrinsic sugars?

A

intrinsic- contained within plant cell walls (good ones eg. fruit and veg)
extrinsic - free in solution (bad ones eg. dental plaque exempt lactose)

161
Q

what is the structure of sucrose?

A

glucosyl-fructose - made from one glucose and one fructose
1’, 2’ oxygen

162
Q

What is the structure of maltose?

A

glucosyl-glucose, made from two glucoses
1’,4’ O and glycosidic bond

163
Q

what is the structure of isomaltose?

A

isoform of maltose linked 1-6

164
Q

what is the structure of lactose?

A

galactosyl-glucose, made from one galactose and one glucose

165
Q

what is the structure of trehalose?

A

glucosyl- glucose, made from two glucoses
1’,1’ O link

166
Q

what are the two components of starch and a description of each’s structure?

A
  • amylose - makes up 20-30% of starch, chain of glucose molecules with an alpha-1’,4’ glycosidic link
  • amylopectin - makes up the rest of starch, chain of glucose molecules (alpha-1’,4’ link) and every 30th glucose branch to other glucose residues (alpha-1’,6’ link)
167
Q

what is the structure of glycogen?

A

very similar to amylopectin but more branched

168
Q

how can starch granules be made digestible?

A

cooking - swells the granules

169
Q

how is starch made available as energy?

A

split by amylase into dextrin and then into glucose, maltose and isomaltose

170
Q

what does it mean if something is osmotically active?

A

it draws water towards it

171
Q

what causes lactose intolerance and what causes the symptoms?

A
  • decrease in lactase activity
  • fermentation to lactate with production of methane and hydrogen gas, osmotically active and draws water into intestine causing flatulence and diarrhoea
172
Q

glycogen is the storage form of ……

A

glucose

173
Q

how can the reducing and non-reducing ends of a polysaccharide be determined?

A

reducing end has a free anomeric carbon
non-reducing end has an acetal

174
Q

what is an acetal?

A

molecule with two single bonded oxygens attached to the same carbon atom

175
Q

why does glycogen not have a reducing end and what does the high number of non-reducing ends mean for it as a molecule?

A

the “reducing end” glucose residue is not free and is covalently bound to a protein called glycogenin as a beta-linkage to a surface tyrosine residue

176
Q

what type of enzyme is glycogenin and what is its structure in the context of glycogen?

A
  • glucosyltransferase
  • sits as a dimer in the core of glycogen
177
Q

what is a glycoprotein?

A

proteins bonded to oligosaccharide chains via amino acid side chains

178
Q

at which amino acids and where in the cell do O- and N-glycosylation occur?

A

O-glycosylation - serine or threonine in the Golgi
N-glycosylation - asparagine in the ER

179
Q

what are proteoglycans?

A

proteins modified with glycosaminoglycans

180
Q

what are mucins?

A

attachment to protein via N-acetylgalactosamine

181
Q

what are two types of N-linked glycans?

A
  • high-mannose
  • complex
182
Q

what does amphipathic mean?

A

A molecule with both hydrophobic and hydrophilic regions.

183
Q

what are two traits of fatty acids?

A
  • saturated (no double bonds)
  • unsaturated (double bonds)
  • usually 12-22 carbons long
184
Q

what are two examples of non-glycerol lipids?

A

sphingolipids and cholesterol

185
Q

what is the benefit of a fluid membrane?

A

they can accommodate conformational changes changes in proteins without losing integrity. This allows for ligand binding, channel opening/closing etc.

186
Q

what reaction can convert phosphatidylinositol into many different signalling molecules? What are three examples of these signalling molecules?

A
  • phosphorylation
  • PIP, PIP2, PIP3
187
Q

what two products of phosphatidylinositol 4,5-biphosphate (PIP2) break down into and why are they important?

A
  • inositol trisphosphate (IP3)
  • diacylglycerol (DAG)
  • important as they are intracellular signals
188
Q

what is the function of phosphatidic acid and phosphatase (PAP)?

A

converts phosphatidate to diacylglycerol (DAG)

189
Q

what is the function of diacylglycerol (DAG)?

A
  • reacts with activated alcohols to form phospholipids
  • reacts with fatty acyl CoA to form triacylglycerols
190
Q

what is the process behind de novo GPL synthesis?

A

combination of an activated alcohol (headgroup) with diacylglycerol

191
Q

what are two roles of sphingomyelin?

A
  • major structural component of membranes
  • source of messenger molecules
192
Q

what is the precursor to sphingomyelin and what enzyme catalyses the conversion?

A
  • ceramide
  • sphingomyelin synthase
193
Q

how are gangliosides formed?

A

addition of a sugar to a sphingolipid

194
Q

……. is phosphorylated by …… forming sphingosine 1-phosphate, a key signalling molecule

A
  1. sphingosine
  2. sphingosine kinase
195
Q

what are three roles of cholesterol?

A
  • maintains membrane bilayer integrity
  • regulates membrane permeability
  • precursor to steroids, vitamins and bile salts
196
Q

what are the three steps to cholesterol biosynthesis?

A
  • synthesis of isopentyl pyrophosphate (via mevalonate)
  • condensation of six isopentyl pyrophosphate to form squalene
  • squalene cyclisation to lanosterol, which is processed to cholesterol
197
Q

why is HMG-CoA reductase vital for regulation of cholesterol biosynthesis?

A

it catalyses the committed steps of cholesterol synthesis

198
Q

in what four ways can HMG-CoA reductase be regulated?

A
  • rate of synthesis of mRNA
  • rate of translation of mRNA to protein
  • rate of degradation of protein
  • phosphorylation state of protein
199
Q

how do sterol regulatory element binding protein (SREBP) and SREBP cleavage acting protein (SCAP) act to regulate the rate of HMG-CoA reductase mRNA synthesis?

A

Sterol regulatory element binding protein (SREBP) is a transcription factor
When [cholesterol ] is high, SCAP (SREBP cleavage activating protein ) & SREBP are bound, preventing SREBP from acting as a transcription factor as its sealed in the membrane .
When [cholesterol] is low, SCAP & SREBP travel to the Golgi , where SREBP is cleaved twice, releasing the DNA binding domain to act on DNA

200
Q

how is rate of translation of HMG-CoA reductase mRNA to protein regulated?

A

nonsterol metabolites derived from mevalonate act as regulators

201
Q

how is phosphorylation state of HMG-CoA reductase regulated?

A

phosphorylation occurs by AMP-activated protein kinase
phosphorylation decreases catalytic activity of HMG-CoA reductase

202
Q

how is cholesterol transported?

A

via body fluids in lipoproteins particles

203
Q

what are the types of “good” and “bad” cholesterol?

A

good - high density lipoprotein (HDL)
bad - low density lipoprotein (LDL)

204
Q

what is a function of bile salts?

A

detergents (solubilise dietary lipids) - can emulsify fats and modify the permeabilization properties of lipid membranes

205
Q

what are the five classes of steroid?

A
  • progestagens
  • glucocorticoids
  • mineralocorticoids
  • androgens
  • oestrogens
206
Q

what are statins?

A

HMG-CoA reductase inhibitors used to lower lipid concentrations to reduce cholesterol

BM210 (3 decks)

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