Session 2- Lipid Transport

Question 1

how are lipids carried around the body

Answer 1

2% carried bound to albumin but this a limited capacity

98% carried are lipoprotein particles consisting of phospholipids, cholesterol, cholesterol esters, proteins and TAG

Question 2

typical lipid range in blood

Answer 2

4000 - 8500 mg/L

Question 3

what are the 2 types phospholipids

Answer 3

choline- phosphatidylcholine

inositol- phosphatidylinositol

Question 4

what steriod hormones is cholesterol the precursor of

Answer 4

cortisol
aldosterone
testosterone
oestrogen

Question 5

what does the lipoprotein cargo consist of

Answer 5

triacylglycerol
cholesterol ester
fat soluble vitamins

Question 6

what the 5 lipoproteins

Answer 6

chylomicrons
VLDL 
IDL
LDL
HDL

Question 7

what are the main carriers of fat

Answer 7

chylomicrons

VLDL

Question 8

what are the main carriers of cholesterol esters

Answer 8

LDL
IDL
HDL

Question 9

Order the lipoproteins in order of most dense to least

Answer 9

HDL
LDL
IDL
VLDL

Question 10

What are the roles of apolipoproteins

Answer 10

structural: packaging water insoluble lipids

functional: co-factor for enzymes
ligands for cell surface receptors

Question 11

function of LDL

Answer 11

provide cholesterol from liver to peripheral tissues
peripheral cells express LDL receptor and take up LDL via receptor mediated endocytosis

transport of cholesterol synthesised in liver to tissues

Question 12

why is LDL more susceptible to oxidative damage

Answer 12

it has a longer half life than VLDL or IDL

Question 13

how does LDL enter cells

Answer 13

LDL receptors/ LDL complex taken into cell by endocytosis into endosomes

fuse with lysosomes for digestion to release cholesterol and fatty acids

LDL-R expression controlled by cholesterol concentration in cell

Question 14

how is HDL synthesised

Answer 14

nascent HDL synthesised by liver and intestine

HDL particles can also bud off from chylomicrons and VLDL as they are digested by LDL

Free apoA-I can also acquire cholesterol and phospholipid from other lipoproteins and cell membranes to form nascent-like HDL

Question 15

chylomicrons function

Answer 15

transport dietary TAG from intestine to tissues such as adipose tossue

Question 16

VLDL function

Answer 16

transport of triacylglycerol synthesised in liver to adipose tissue for storage

Question 17

IDL function

Answer 17

short-lived precursor of LDL. Transport of cholesterol synthesised in the liver to tissues

Question 18

HDL function

Answer 18

transport of excess cholesterol from cells to liver for disposal as bile salts and to cells requiring additional cholesterol

Question 19

what is hyperlipoproteinaemia

Answer 19

raised plasma level of one or more lipoprotein class
caused by
-over production
-under removal

defects in

• enzymes
• receptors
• apoproteins

Question 20

clinical signs of hypercholeserolaemia

Answer 20

high levels of cholesterol in blood 
cholesterol depositions in various areas of body 
Xanthelasma-yellow patches
tendon xanthoma- nodules 
corneal arcus- white circle around eye

Question 21

how is raised serum levels associated with artheroscelrosis

Answer 21

oxidised LDL
recognised and engulfed by macrophages
macrophages turn into foam cells
foam cells accumulate in intima of blood vessels
fatty streak can evolve into artherosclerotic plaque
grows and enroaches the lumen of the artery causing angina
the blood vessels could rupture and trigger acute thrombosis causing an MI or stroke

Question 22

how do you treat hyoerlipoproteinaemia

Answer 22

diet- reduce cholesterol and saturated lipids and increase fibre intake

lifestyle- exercise and stop smoking

statins- reduce cholesterol synthesis by inhibiting HMG-CoA reductase

bile salt sequestrants- bind bile salts in GI tract. Forces liver to produce more bile acids using more cholesterol

Question 23

statins mechanism if action

Answer 23

they inhibit HMG-CoA reductase which usually converts HMG-CoA formed from acetyl-CoA to mevalonate which forms cholesterol

Question 24

what is PKU

Answer 24

phenylketonuria- deficiency in phenylalanine hydroxylase causes phenylalanaine to be converted into phenylpyruvate which is converted into phenylacetate and phenyllactate (phenylketones)

autosomal recessive

accumulation of phenylalanine in tissues, plasma and urine]

phenylketones in urine

musty smell

Question 25

what pathways does PKU affect

Answer 25

noradrenaline
adrenaline
dopamine 
melanin 
thyroid hormone 
protein synthesis

Question 26

symptoms of PKU

Answer 26

severe intellectual disability 
developmental delay 
microcephaly
seizures 
hypopigmentation

Question 27

how does phenylalanine affect brain development

Answer 27

it is a large neutral amino acid

competes for transport across the blood brain carrier via Large neutral amino acid transporter

excess phenylalanine can saturate this transport

levels of other LNAA in the brain decreased

protein/neurotransmitter synthesis inhibited

brain development affected

causes metal retardation

Question 28

how do you treat PKU

Answer 28

strictly controlled phenylalanine diet

avoid artificial sweetners

avoid high protein foods such as

• meat
• milk
• eggs

Question 29

what is homocystinurias

Answer 29

problem breaking down methionine
excess homocysteine excreted in urine
autosomal recessive disorders
defect in cystathione beta-synthase

affects connective tissue, muscles, CNS and CVS

Question 30

how do you treat homocystinurias

Answer 30

low-methionine diet
avoid milk, cheese, meat, fish and eggs
nuts and peanut butter

cysteine, Vit b6, betaine, b12, and folate supllemment

Question 31

what is the difference between marfans and homocystinuria

Answer 31

metabolites of methionine are toxic to neurons and cause neurological disfunction isnt seen in marfans