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biochemistry Flashcards

1
Q

what are the major carbohydrates of the diet

A

starch
glycogen
cellulose and hemulose
oligosaccharides
lactose, sucrose and maltose,
glucose and fructose

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2
Q

describe digestion of carbohydrates in the mouth

A

salivary amylase hydrolyses a1-4 bonds of starch

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3
Q

describe digestion of carbohydrates in the stomach

A

no carbohydrate digestion

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4
Q

describe digestion of carbohydrates in the duodenum

A

pancreatic amylase works as in mouth

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5
Q

describe digestion of carbohydrates in the jejunum

A

final digestion by mucosal cell surface enzymes

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6
Q

how are glucose and galactose absorbed

A

through and indirect ATP powered process

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7
Q

how is fructose absorbed

A

fructose binds to the channel protein GLUTS and moves down a concentration gradient

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8
Q

how are cellulose and hemicellulose digested and absorbed

A

they cannot be digested by the gut but instead increase faecal bulb and decrease transit time

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9
Q

what are hexokinase and glucokinase

A

enzyme catalysts

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10
Q

synthesis of glycogen step 1

A

Glycogenin covalently binds Glc from uracil-diphosphate (UDP)-glucose to form chains of approx. 8 Glc residues.
Then glycogen synthase takes over and extends the Glc chains

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11
Q

synthesis of glycogen step 2

A

The chains formed by glycogen synthase are then broken by glycogen-branching enzyme and re-attached via (α1→6) bonds to give branch points

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12
Q

function of glycolysis

A
  • catabolic pathway that saves some potential energy from glucose-6-phosphate by forming ATP
  • the only way energy can be made from fuel molecules when cells lack O2
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13
Q

what does lactate dehydrogenase do

A

responsible for the production of lactate and regeneration of NAD+

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14
Q

what does pyruvate dehydrogenase do

A

catalyzes the oxidative decarboxylation of pyruvate with the formation of acetyl-CoA, CO2and NADH (H+)
(1,–3)

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15
Q

what is pyruvate converted to in human cells lacking O2

A

lactate

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16
Q

what are the different classes of amino acids

A
  • aliphatic amino acids
  • aromatic amino acid
  • sulphur containing amino acids
  • basic amino acids
  • acidic amino acids
  • polar amino acids
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17
Q

aliphatic amino acid characteristic

A

R group consisting of hydrocarbon chains

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18
Q

aromatic amino acid characteristic

A

R group consisting of a hydrocarbon ring

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19
Q

functions of proteins

A
  • structural
  • enzymatic
  • contractile
  • receptor
  • defensive
  • hormonal
  • storage
  • transport
    STRECHDS
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20
Q

define primary structure

A

sequence in which amino acid monomers are bonded together to form a polypeptide chain

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21
Q

define secondary structure

A
  • 3D spatial arrangement of amino acids located near each other in a polypeptide chain
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22
Q

forms of secondary structure

A

alpha helix for example myoglobin
beta pleated sheet form like fatty acid binding protein

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23
Q

define tertiary structure

A
  • functional groups interacting with eachother
  • involves van der waals, ionic, hydrogen, disulphide and hydrophobic interactions
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24
Q

define quaternary structure

A
  • several polypeptides interacting with each other
  • example: haemoglobin
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25
what are glycoproteins
proteins with less than/or 1 carbohydrate molecule
26
function of glycoproteins
can cause stability, solubility, cell signalling, orientation
27
what are lipoproteins
combined with lipids to form lipoproteins
28
where are lipoproteins found
in cell membranes
29
function of lipoproteins
transport hydrophobic molecules
30
what are metalloproteins
protein molecules with metal ions within their structures
31
functions of metalloproteins
various functions e.g signal transduction, storage, transport
32
functions of globular proteins
storage, enzymes, hormones, transporters, structural
33
structure of globular proteins
can be sphere to cigar shape
34
fibrous proteins location
muscle fibres and connective tissue
35
structure of fibrous proteins
polypeptide chains organized approximately in parallel along a single axis, producing long fibers or large sheets
36
how do enzymes reduce entropy
they force the substrate to be correctly orientated by binding them in the formation they need to be in for the reaction to proceed
37
describe desolvation in enzyme-catalysed reactions
weak bonds between the substrate and enzyme essentially replace most or all of the H-bonds between substrate in an aqueous solution
38
describe induced fit
conformational changes occur in the protein structure when the protein binds
39
what is Km
a measure of the affinity an enzyme has for its substrate, as the lower the value of Km, the more efficient the enzyme is at carrying out its function at a lower substrate concentration
40
what happens to Vmax and Km with a competitive inhibitor
Vmax remains unchanged Km increases because it takes more substrate to overcome the inhibition
41
what happens to Vmax and Km with a non-competitive inhibitor
- Vmax is decreased due to enzymes being taken out of action - Km remains the same as the active site of the enzymes that have not been inhibited is unchanged
42
why is enzyme activity measured in a clinical setting
- Detection of suspected disease at pre-clinical stage - Confirmation of suspected disease and assessing severity - Localisation of disease to organs - Characterisation of organ pathology - Assessing the response to therapy - Organ function assessment - Assessing genetic susceptibility to drug side effects - Detection of inherited metabolic disease Detection of vitamin deficiency
43
factors influencing enzyme activity in samples
hypoxia cellular damage physical damage immune disorders microbiological agents genetic defects nutritional disorders
44
where does the citric acid cycle occur
mitochondrial matrix
45
how is acetyl CoA produced
made via the decarboxylation of pyruvate dehydrogenase from pyruvate then oxidation then a transfer of the CoA complex
46
function of pyruvate dehydrogenase sub-units
Each sub-unit catalyses a different part of the reaction to convert pyruvate to acetyl CoA
47
function of E1
E1 catalyses the first decarboxylation of pyruvate
48
function of E2
E2 transfers the acetyl group to coenzyme A
49
function of E3
E3 recycles the lipoyllysine through the reduction of FAD, which is recyled by passing electrons to NAD+
50
what are the electron carriers of the citric acid cycle
FADH2 and NADH
51
what is complex 1 in terminal respiration
NADH-Q oxidoreductase
52
describe complex 1
Oxidises NADH and passes the high-energy e’s to ubiquinone to give ubiquinol
53
what is complex 2 of terminal respiration
Succinate-Q reductase
54
describe complex 2
Oxidises FADH2 and like complex I passes high-energy e’s to ubiquinone, which becomes ubiquinol
55
what is complex 3 of terminal respiration
Q-cytochrome c oxidoreductase
56
describe complex 3
Takes the e’s from ubiquinol (QH2) and passes them to cytochrome c
57
what is complex 4 of terminal respiration
cytochrome c oxidase
58
describe complex 4
Takes the e’s from cytochrome c and passes them to molecular O2
59
describe chemiosmosis
As e-’s pass through the complexes of the transport chain protons move from the matrix to the outside of the inner mitochondrial membrane
60
describe proton motive force
When these protons are ‘allowed’ to flow back down their gradient they release energy to do work
61
what is the binding change mechanism
sequential conformational changed of B subunit
62
what are the major lipid classes and their role in health and disease
- fatty acids (can be good or bad due to saturation) - triaglycerols (dietary fuel and insulation) - phospholipids (membrane signalling) - steroids (cholesterol, steroid, bile salts) - eicosanoids
63
where does lipid digestion begin and by what
stomach acid lipases
64
where is the main site of lipid digestion
small intestine
65
describe the absorption of lipids
Ingested lipids (e.g TAG) are cleaved by enzymes (e.g., pancreatic lipase), absorbed in the small intestine, and then transported in chylomicrons via the lymphatic system into the bloodstream, where they reach the liver (for lipoproteins), peripheral tissues (energy) and adipose tissue (storage).
66
how are lipids transported in chylomicrons
FAs are insoluble so they are packed into chylomicrons which are released by exocytosis into the lymph then blood
67
describe the steps of beta oxidation
dehydrogenation hydration dehydrogenation thiolysis
68
energy yield of beta oxidation
32 ATP from 1 glucose molecule
69
what are ketone bodies
- normal metabolites of fat - energy source when fasting
70
synthesis of ketone bodies
- ketone bodies can be oxidised in the mitochondria to yield 2 GTP and 22 ATP
71
transport of ketone bodies
- ketone bodies are transported from the liver to other tissues and reconverted to acetyl-CoA
72
main nitrogen-containing molecules of the body
amino acids and nucleotides
73
fate of dietary protein
synthesised into amino acids and then used for carbon skeletons or cellular respiration
74
what regulates urea production
CPS1 enzyme
75
what activates CPS1
N-acetyleglutamate and is allosteric

foundations of medicine (5 decks)

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