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foundations of medicine > biochemistry > Flashcards

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
Q

what are glycoproteins

A

proteins with less than/or 1 carbohydrate molecule

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26
Q

function of glycoproteins

A

can cause stability, solubility, cell signalling, orientation

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27
Q

what are lipoproteins

A

combined with lipids to form lipoproteins

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28
Q

where are lipoproteins found

A

in cell membranes

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29
Q

function of lipoproteins

A

transport hydrophobic molecules

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30
Q

what are metalloproteins

A

protein molecules with metal ions within their structures

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31
Q

functions of metalloproteins

A

various functions e.g signal transduction, storage, transport

32
Q

functions of globular proteins

A

storage, enzymes, hormones, transporters, structural

33
Q

structure of globular proteins

A

can be sphere to cigar shape

34
Q

fibrous proteins location

A

muscle fibres and connective tissue

35
Q

structure of fibrous proteins

A

polypeptide chains organized approximately in parallel along a single axis, producing long fibers or large sheets

36
Q

how do enzymes reduce entropy

A

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
Q

describe desolvation in enzyme-catalysed reactions

A

weak bonds between the substrate and enzyme essentially replace most or all of the H-bonds between substrate in an aqueous solution

38
Q

describe induced fit

A

conformational changes occur in the protein structure when the protein binds

39
Q

what is Km

A

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
Q

what happens to Vmax and Km with a competitive inhibitor

A

Vmax remains unchanged
Km increases because it takes more substrate to overcome the inhibition

41
Q

what happens to Vmax and Km with a non-competitive inhibitor

A
  • 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
Q

why is enzyme activity measured in a clinical setting

A
  • 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 diseaseDetection of vitamin deficiency
43
Q

factors influencing enzyme activity in samples

A

hypoxia
cellular damage
physical damage
immune disorders
microbiological agents
genetic defects
nutritional disorders

44
Q

where does the citric acid cycle occur

A

mitochondrial matrix

45
Q

how is acetyl CoA produced

A

made via the decarboxylation of pyruvate dehydrogenase from pyruvate then oxidation then a transfer of the CoA complex

46
Q

function of pyruvate dehydrogenase sub-units

A

Each sub-unit catalyses a different part of the reaction to convert pyruvate to acetyl CoA

47
Q

function of E1

A

E1 catalyses the first decarboxylation of pyruvate

48
Q

function of E2

A

E2 transfers the acetyl group to coenzyme A

49
Q

function of E3

A

E3 recycles the lipoyllysine through the reduction of FAD, which is recyled by passing electrons to NAD+

50
Q

what are the electron carriers of the citric acid cycle

A

FADH2 and NADH

51
Q

what is complex 1 in terminal respiration

A

NADH-Q oxidoreductase

52
Q

describe complex 1

A

Oxidises NADH and passes the high-energy e’s to ubiquinone to give ubiquinol

53
Q

what is complex 2 of terminal respiration

A

Succinate-Q reductase

54
Q

describe complex 2

A

Oxidises FADH2 and like complex I passes high-energy e’s to ubiquinone, which becomes ubiquinol

55
Q

what is complex 3 of terminal respiration

A

Q-cytochrome c oxidoreductase

56
Q

describe complex 3

A

Takes the e’s from ubiquinol (QH2) and passes them to cytochrome c

57
Q

what is complex 4 of terminal respiration

A

cytochrome c oxidase

58
Q

describe complex 4

A

Takes the e’s from cytochrome c and passes them to molecular O2

59
Q

describe chemiosmosis

A

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
Q

describe proton motive force

A

When these protons are ‘allowed’ to flow back down their gradient they release energy to do work

61
Q

what is the binding change mechanism

A

sequential conformational changed of B subunit

62
Q

what are the major lipid classes and their role in health and disease

A
  • 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
Q

where does lipid digestion begin and by what

A

stomach acid lipases

64
Q

where is the main site of lipid digestion

A

small intestine

65
Q

describe the absorption of lipids

A

Ingested lipids (e.g TAG) are cleaved by enzymes (e.g.,pancreatic lipase), absorbed in thesmall intestine, and then transported inchylomicronsviathe lymphatic systeminto the bloodstream, where they reach theliver (for lipoproteins), peripheral tissues (energy) andadipose tissue(storage).

66
Q

how are lipids transported in chylomicrons

A

FAs are insoluble so they are packed into chylomicrons which are released by exocytosis into the lymph then blood

67
Q

describe the steps of beta oxidation

A

dehydrogenation
hydration
dehydrogenation
thiolysis

68
Q

energy yield of beta oxidation

A

32 ATP from 1 glucose molecule

69
Q

what are ketone bodies

A
  • normal metabolites of fat
  • energy source when fasting
70
Q

synthesis of ketone bodies

A
  • ketone bodies can be oxidised in the mitochondria to yield 2 GTP and 22 ATP
71
Q

transport of ketone bodies

A
  • ketone bodies are transported from the liver to other tissues and reconverted to acetyl-CoA
72
Q

main nitrogen-containing molecules of the body

A

amino acids and nucleotides

73
Q

fate of dietary protein

A

synthesised into amino acids and then used for carbon skeletons or cellular respiration

74
Q

what regulates urea production

A

CPS1 enzyme

75
Q

what activates CPS1

A

N-acetyleglutamate and is allosteric

foundations of medicine (5 decks)

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