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part I > human metabolism: carbs, fats proteins (biochem) > Flashcards

human metabolism: carbs, fats proteins (biochem) Flashcards

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1
Q

which is the only fuel that can be respired anaerobically?

A

carbohydrates

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2
Q

which 2 parts of body rely especially on carbohydrates?

A

brain

erythrocytes

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3
Q

monosaccharides examples x2

which foods are they found in?

A

glucose and fructose
(both found in fruit & honey)

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4
Q

disaccharides examples x2

what are their monosaccharide components?

which foods are they found in?

A

lactose (milk sugar)
glucose, galactose
milk

sucrose (table sugar)
glucose, fructose
cane sugar, prepared foods

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5
Q

trisaccharide (1)
what is its monosaccharide component?
which food is it found it?

A

trehalose

glucose

mushrooms

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6
Q

polysaccharides examples (3)

i) monosaccharide components
ii) foods they are found in

A

amylose
i) glucose (linear)
ii) plant starch

amylopectin
i) glucose (branched)
ii) plant starch

glycogen
i) glucose (branched)
ii) meat

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7
Q

what is the first stage of both aerobic and anaerobic respiration?

A

glycolysis

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8
Q

in which part of the cell does glycolysis occur?

what are the start and end products?

A

cytosol

glucose –> 2x pyruvate

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9
Q

under anaerobic conditions what happens to pyruvate?

which enzyme does this?

what other substance is involved in anaerobic respiration of pyruvate and what is it turned into?

A

reduced to lactate

lactate dehydrogenase

NADH –> NAD+

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10
Q

where does aerobic metabolism take place?

A

mitochondria

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11
Q

what is the cycle for aerobic respiration called?

A

tricarboxylic acid cycle (Krebs cycle)

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12
Q

what initially happens to pyruvate during aerobic respiration?

which enzyme catalyses this reaction?

what other substance is involved and what is it converted to/from?

A

pyruvate –> acteyl CoA + CO2

PDH (pyruvate dehydrogenase)

NAD+–> NADH

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13
Q

what happens to acetyle CoA in tricarboxylic acid acid?

A

acetyl CoA (C2) + oxaloacetate (C4)–> citrate (C6) –> cis-acetonate (C6) –> isocitrate (C6)

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14
Q

what happens to isocitrate in tricarboxylic acid cycle?

A

isocitrate (C6) –> a-ketoglutarate (C5) + CO2

NAD+–> NADH facilitates this reaction

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15
Q

what happens to a-ketogluterate (C5) in tricarboxylic acid cycle?

A

–> succinyl CoA (C4) + CO2

facilitated by NAD+ –> NADH

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16
Q

how does succinyl CoA become oxeloacetete in tricarboxylic acid cycle?

A

succinyl CoA –> succinate
facilitated by GDP –> GTP

succinate –> fumerate
facilitated by FAD–> FADH2

fumerate –> malate

malate –> oxaloacetate
facilitated by NAD+ –> NADH

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17
Q

products of each TCA cycle:

A

reduced co-factors: 3x NADH, 1x FADH2
high energy compound: 1x GTP
decarboxylation products: 2x CO2

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18
Q

how many moles of ATP are produces by:

i) aerobic respiration
ii) anaerobic respiration

A

i) 30-32
ii) 2

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19
Q

examples of partially anaerobic tissues: (4)

A
  • renal medulla
  • retinal cells
  • red blood cells
  • white (type 2) muscle fibres
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20
Q

white muscle fibres

  1. which fuel can they use?
  2. what do they store?
  3. what is storage product broken down to?
A
  1. only glucose
  2. glycogen

glycogen is broken down to glucose -1-phosphate then intermediate glucose-6-phosphate

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21
Q

how much glucose does the brain consume per day in:

i) fed state
ii) starved state

How quickly are glycogen stores used up in starvation?

A

i) 100g/day
ii) 25g/day

within 1st 24 hrs

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22
Q

how is glucose obtained during starvation?

A

breakdown of muscles

protein –> amino acid –> oxoacid

amino acid–> oxoacid
allows pyruvate –> alanine

alanine –> pyruvate in liver
which then allows for glucose production in the liver

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23
Q

what is the site of ketogenesis?

A

the liver

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24
Q

which transport molecule allows glucose to be taken up into brain?

A

GLUT 3

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25
how is fat stored in the body?
triaglycerol (TAG/ triglyceride) this forms lipid droplets in cytosol of adipocyte
26
major roles of fats in the body (5) + the form of fat involved in each
1. energy storage - triglycerol 2. membrane formation - phospholipids 3. hormone synthesis - eicosanoids (prostaglandins, thromboxanes, leucotrienes formed from essential fatty acids) 4. intracellular signalling - membrane phospholipids broken down to second messengers when hormone binds to its receptor 5. regulation of gene transcription - fatty acids (+ fat-soluble vitamins)
27
TAG (triaglycerol structure)
threecarbon glycerol backbone that is esterified to three fatty acid side chains and the free fatty acid molecule constitutes the accessible energy source for cells and tissues.
28
which enzymes catalyses liberation of of fatty acid from TAG?
hormone-sensitive lipase (HSL)
29
what affects HSL (hormonesensitive lipase) levels?
stimulated by: - glucagon - adrenaline - noradrenaline inhibited by: - insulin (HSL is elevated in diabetics due to poor insulin sensitiv/ porduction)
30
how are fats transported in blood?
in protein complexes (as are hydrophobic and insoluble)
31
Elevated levels of which one of LDL/ HDL can be sign of high fat diet?
LDL
32
chylomicron i. main fat constituent ii. function
i. dietary TAG ii. transports TAG from intestine to other tissues for oxidation or storage (fed state)
33
VLDL (very low density lipoprotein) i. main fat constituent ii. function
i. endogenous TAG, cholesterol ii. Transports TAG produced in the liver to other tissues where it can be oxidised (fasting state)
34
LDL i. main fat constituent ii. function
i. cholesterol and cholesteryl ester ii. transports cholesterol from liver to other tissues
35
HDL i. main fat constituent ii. function
i. cholesteryl ester ii. Scavenges cholesterol from many tissues and takes it to the liver for excretion
36
fatty acid-albumin i. main fat constituent ii. function
i. fatty acid ii. Transports fatty acids from adipose tissue to other tissues where they can be oxidised (fasting state)
37
which 2 aerobic tissues consume and oxidise fatty acids at high rates?
heart tissue red fibres of skeletal muscle
38
name of pathway which oxidises fatty acids? which part of cell does it occur in? what are its products diagram:
beta oxidation pathway mitochondria 1x acetyl CoA 1x FADH2 1x NADH
39
what is drawn to the liver to fuel gluconeogenesis during starvation?
oxaloacetate
40
imbalance in of oxeloacete and acetyl CoA in liver during starvation [liver takes up high levels of fatty acid so beta oxidation rates remain high resulting in an imbalance between CoA and oxeloacetate levles] what does liver do with excess acetyl CoA?
ketogenesis
41
how much of brain's energy supply do ketones account for during starvation? what level of ketones is sustained in body? which is main ketone used for energy supply?
75% 8mmol/l acetoacetane (acetone is what is excreted in urine)
42
what elements are amino acids made from?
carbon hydrogen oxygen nitrogen
43
in amino acid breakdown what is disposed of separately from carbon skeleton? why?
the amino group to maintain nitrogen balance and prevent accumulation of toxic nitrogenous compounds such as ammonium ion (NH4+)
44
what's the first stage in amino acid metabolism?
removal of the amino group
45
what happens in transamination? which enzyme is involved?
amino group is transferred to a different carbon skeleton a-ketogluerate --> glutamate amino transferase (remember is reversible in case NH4+ levels are low)
46
what happens in de-amination? enzyme involved
amino group is released as NH4+ glutamate +H2o--> a-ketoglutarate + NH4+ facilated by NAD+ --> NADH glutamate dehydrogenase (remember is reversible in case NH4+ levels are low) NB. the pathway of amino acid degradation includes many aminotransferase enzymes with specificity for individual amino acids but only one enzyme (glutamate dehydrogenase) with deaminating activity
47
urea cycle 1. which organ does it occur in? 2. which part of the cell? 3. what is its purpose?
1. liver 2. mitochondria and cytosol 3. detoxify ammonium to produce urea (non-toxic vehicle for transport of nitrogen out of body)
48
upper limit of normal NH4+ in blood? at what levels do sx of toxicity delevlop?
20 micromoles/ L (except for hepatic portal vein where concentrations are like 10x higher) 200 micromoles/L +
49
urea cycle equation:
NH4+ + bicarbonate + asparte (amino acid) ---> urea + fumerate (TCA intermediate) facilitated by 3ATP --> 2ADP + AMP
50
amino acids that are converted to which substance are ketogenic?
acetyl CoA
51
which are the 2 main amino acids released by the brain during starvation? what % of broken down amino acids do they account for?
alanine glutamine 60-70%
52
conversion of glucogenic amino acids to glucose
53
phenylketonuria (PKU) i. what is it? ii. incidence in UK iii. how many different polymorphisms account for this phenotype
i. absence/ greatly diminished activity of enzyme phenylalinase hydroxylase ii. 1 in 10,000 iii. 300
54
PKU what happens
i. acculumation of pheylalanine interferes with uptake of other amino acids by competition with the saturable amino acid transporter results in severe impact on developing brain
55
screening test for PKU? when is it done? cut-off level for dx?
Guthrie test 6-14 days post natally 240 micromoles/L
56
PKU mgt
exclude phenylalaline from diet but include tyrosine and other amino acids must be followed strictly until 11 years must be resumed in pregnancy
57
which amino acid is phenylalanine closely linked to? what appearance can this result in?
tyrosine occulocutaneous albinism
58
insulin sensitivity: i. in early pregnancy vs normal ii. in 3rd trimester vs normal
i. increased ii. reduced by 50-70%
59
TAG/ fatty acids in: i. maternal tissues ii. foetal tissues
i. deposition (early pregnancy) oxidation and ketogenesis (later in pregnancy) ii. little oxidate capacity, stored in late gestation
60
glucose in: i. maternal tissues ii. foetal tissues
i. reduced insulin sensitivity so reduced uptake ii. oxidised at high rates, staored as glycogen in late gestation
61
amino acids: i. in foetal tissues
consumed for proteins synthesis
62
ketone bodies: i. maternal tissues ii. foetal tissues
i. higher circulating levels (indicate high ration of use) ii. little if any oxidate capacity
63
foetal metabolism
no gluconeogenesis initially as no glycogen stores in liver fatty acid oxidation in liver ^^ post natally (but lipogenic capacity remains low until weaning)
64
what else does neonate need dietry fat for (2)
1. CNS development (3rd trimester to 3 months post natal) especially DHA, a derrivatiev of a-linoleic acid (an omega 3 fatty acid) 2. thermogenesis - fatty acids are metabolised by brown adipose tissue for thermogenesis (infant does not have right muscles to shiver)

part I (12 decks)

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