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Science for Medicine > Lipids > Flashcards

Lipids Flashcards

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1
Q

What are some of the functions of lipids?

A 
membrane structure
hormones
vitamins
energy storage
signalling
enzyme cofactors
insulation
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2
Q

what are the essential fatty acids which we have to obtain from diet?

A

linoleic acid

arachidonic acid

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3
Q

what is arachidonic acid derived from?

A

linoleic acid

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4
Q

what are the main dietary lipids?

A

TAG
phospholipids
cholesterol esters

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5
Q

what is the structure of a TAG?

A

glycerol head and three fatty acids

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6
Q

what is the structure of phospholipids?

A

glycerol with two fatty acids and hydrophilic phosphate attached to glycerol

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7
Q

how are lipids digested and absorbed in the gut?

A

emulsification breaks up lipid lumps
pancreatic lipase cuts up TAG into fatty acids
bile salts form micelles with long fatty acids for absorption by gut cells
free fatty acids are absorbed directly

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8
Q

what happens to fatty acids once they enter the gut cells?

A

reassembled into TAG, cholesterol esters and phosphplipids for export

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9
Q

what happens to fatty acids when they leave the gut cells?

A

packaged into chylomicrons with ApoB48

travel through lymph then blood to capillaries

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10
Q

what is the protein that holds lipids packaged into chylomicrons for travel in the circulation?

A

apoB-48

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11
Q

what happens to chylomicrons when they reach the capillaries?

A

fatty acids cleaved off by lipoprotein lipase

then used up for fuel or stored in adipose tissue

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12
Q

what triggers the release or storage of TAG in adipose tissue?

A

hormone sensitive lipase (HSL) activated by epinephrine - releases TAG
high glucose in blood - inhibits release of TAG

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13
Q

how are lipids transported in the blood when release from adipose tissue?

A

free fatty acids - albumin

fatty acid esters (compounds) - lipoproteins

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14
Q

what are the different types of lipoproteins, what do they carry and where?

A

chylomicrons - TAG from intestine to tissues after absorption
VLDL - TAG from liver to tissues
LDL - cholesterol from liver to tissues
HDL - cholesterol from tissues to liver

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15
Q

what are the three stages of fatty acid metabolism?

A

activation
transport
degradation

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16
Q

what happens during fatty acid activation?

A

fatty acid is turned into fatty acyl CoA in cytosol

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17
Q

what happens during fatty acid transport?

A

fatty acyl CoA transported into mitochondrion through carnitine shuttle
CoA taken off before transport, another CoA added in mitochondrion

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18
Q

what are the four steps of fatty acid degradation and what happens during them?

A

Dehydrogenation - FAD to FADH2
Hydration - water added
Dehydrogenation - NAD to NADH
Thiolysis - becomes Acetyl CoA

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19
Q

what happens to Acetyl CoA if there is too much of it in the mitochondria of the liver?

A

Acetyl CoA turned into Ketone bodies

pyruvate carboxylase turns pyruvate into oxaloacetate for gluconeogenesis

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20
Q

what are the properties of Ketone bodies?

A

can be used for fuel by brain and muscle
can’t be used by liver
acidic compound

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21
Q

what happens if there are too many ketone bodies in the circulation?

A

acidosis

fruity breath from acetone

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22
Q

what are the three types of ketone bodies?

A

acetoacetate
acetone
D-betahydroxybutarate

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23
Q

what molecules inhibits carnitine shuttle activity?

A

malonyl CoA

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24
Q

what is the energy yield from breakdown of a 16C fatty acid chain?

A

7 FADH2
7 NADH
8 Acetyl CoA
129 ATP total

25
Q

how is a fatty acid chain broken up for metabolism?

A

two carbons at a time

26
Q

what happens if the fatty acid chain is too long?

A

shortened in peroxisome

no FADH2 comes off

27
Q

are ketone bodies water or lipid soluble?

A

water soluble

28
Q

what is the process of fatty acid metabolism called?

A

beta oxidation

29
Q

where in the cell does fatty acid synthesis occur?

A

in cytosol

30
Q

how does Acetyl CoA get transported from the liver cell mitochondrion to the cytosol?

A

through the citrate shuttle

31
Q

what is the building block of fatty acid synthesis?

A

malonyl CoA

32
Q

which molecule is used to carry H+ in fatty acid synthesis?

A

NADPH

33
Q

how is cholesterol synthesised?

A

acetyl CoA converted to HMG CoA

34
Q

what are eicosanoids and some examples?

A

long fatty acid chains derived from essential fatty acids

examples are leukotrienes, prostaglandins, thromboxane

35
Q

what are the steps involved in fatty acid synthesis and what happens in them?

A

condensation (acetyl CoA to Malonyl CoA)
reduction (NADPH to NADP)
dehydration (water molecule lost)
reduction (NADPH to NADP)

36
Q

where are fatty acids further synthesised in the cell?

A

Endoplasmic reticulum

37
Q

what enzyme turns acetyl CoA into malonyl CoA in fatty acid synthesis?

A

Acetyl CoA Carboxylase

38
Q

where are steroids derived from?

A

cholesterol

39
Q

what is the end result of fatty acid synthesis?

A 
palmitic acid
8 CoA
14 NADP
7 ADP
7 Pi
7 H2O
40
Q

how is Malonyl CoA carried through the cytosol to be added to the growing fatty acid chain?

A

through ACP

41
Q

what is the main enzyme complex used to link together malonyl CoA to turn it into palmitic acid?

A

fatty acid synthase

42
Q

how is nitrogen captured from the atmosphere?

A

through nitrogen fixation by bacteria

43
Q

how is nitrogen found in the body, and how is it passed to different molecules?

A

found in amino groups

transamination “ping-pong reaction” to bounce amino groups from one molecule to the other

44
Q

what is an amino acid called when it doesn’t have a nitrogen attached to it?

A

keto acid

45
Q

what is the only molecule in the body which accepts nitrogen directly (as ammonia)?

A

glutamate

46
Q

what are the four most commonly found amino acids in the body?

A

Alanine
Aspartate
Glutamine
Glutamate

47
Q

how is nitrogen excreted by the body?

A

through the urea cycle

48
Q

where does metabolism of nitrogen occur in the body?

A

mitochondria of liver cells

49
Q

what are the enzymes which break down proteins in the body, where do they occur and what is their function?

A

pepsin - stomach (break proteins into peptides)
trypsin/chymotrypsin - small intestine (break up larger proteins into peptides)
aminopeptidases - small intestine (break up peptides into amino acids)

50
Q

when are proteins broken down by the body?

A

during starvation once sugars/fats are depleted
when there is excess protein from turnover
when there is excess protein from diet

51
Q

what is an important co-factor for the function of transaminases, and what is it derived from?

A

pyridoxal phosphate cofactor

derived from vitamin B6

52
Q

what is a proteasome and when is it used?

A

recycling point for malfunctioning proteins

proteins “ubiquinated” and sent to proteasome for breaking up

53
Q

what is the purpose of the glucose-alanine cycle?

A

it allows pyruvate to be turned back into glucose when muscle is exercising anaerobically

54
Q

when are the two main nitrogen acquiring steps during protein metabolism?

A

when ammonia is captured by synthesis of Carbamoyl phosphate (after glutamate has been split)
when aspartate enters the urea cycle

55
Q

how can the carbon chains of amino acids be used during metabolism?

A

they can be broken down for energy (CAC)
they can make the citric acid cycle intermediaries
they can form glucose through oxaloacetate and gluconeogenesis
they can form ketone bodies through Acetyl CoA

56
Q

why are glutamine and alanine used to transport nitrogen around the body, rather than glutamate?

A

because glutamate has negative charge

alanine and glutamine are uncharged

57
Q

what is the main function of the urea cycle?

A

to introduce ammonia (which is toxic) and turn it into urea (non-toxic)

58
Q

what is an example of a metabolic urea cycle disorder?

A

ornithine transcarbamoylase deficiency

59
Q

what is an example of a metabolic amino acid disorder?

A

phenylketonuria (PKU)

Science for Medicine (6 decks)

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