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metabolism > Lipid Transport & Storage > Flashcards

Lipid Transport & Storage Flashcards

1
Q

How are lipids transported?

A

Associated with a protein - 98% as lipoproteins and 2 % bound non-covalently to albumin

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2
Q

Describe the structure of apoproteins

A

Involved in packaging non-water soluble lipids into a soluble form. Contain hydrophobic and hydrophilic regions.

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3
Q

What are the main functions of apoproteins?

A

Activation of enzymes or recognition of cell surface receptors

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4
Q

Describe the structure of a lipoprotein

A

Spherical, surface coat - phospholipids, cholesterol and apoproteins, hydrophobic core - TAGs and cholesterol esters

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5
Q

What keeps lipoproteins stable?

A

Their shape which is dependent on the ratio of core to surface lipids

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6
Q

What is the function of chylomicrons?

A

Transport dietary TAGs from intestines to tissues

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7
Q

What is the function of VLDLs?

A

Transport of TAGs synthesis in liver to adipose for storage

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8
Q

What is the function of LDLs?

A

Transport of cholesterol synthesised in liver to tissues

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9
Q

What is the function of HDLs?

A

Transport of excess tissue cholesterol to liver for disposal (as bile salts)

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10
Q

What happens to dietary TAGs?

A

Hydrolysed in the small intestine by pancreatic lipase. FAs enter epithelial cells - re-esterified to TAGs and then packaged into chylomicrons

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11
Q

How are chylomicrons released into the blood?

A

Via the lymphatic system, from epithelial cells.

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12
Q

Which tissues do chylomicrons affect?

A

Tissues that express the extracellular enzyme lipoprotein lipase

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13
Q

What does lipoprotein lipase do?

A

Removes the core TAGs from lipoproteins. Hydrolyses TAGs in lipoproteins to give FAs and glycerol.

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14
Q

Where can you find lipoprotein lipase?

A

Attached the inner surface of capillaries in muscles and adipose tissue

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15
Q

What does lecithin:cholesterol acyltransferase (LCAT) do?

A

Restores stability of lipoproteins. Conversion of surface lipid to core lipid - cholesterol - cholesterol ester using FA derived from lecithin

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16
Q

What happens if there is a deficiency in lecithin?

A

Unstable lipoproteins, general failure of lipid transport. Lipid deposits occur in many tissues and can lead to atherosclerosis

17
Q

How do tissues obtain cholesterol from LDLs?

A

Receptor-mediated endocytosis

18
Q

Outline the mechanism for the uptake of cholesterol

A

Cells synthesise LDL receptors, bind to specific apoproteins (Apo B100) on the LDL, endocytosis, lysosomal digestion, cholesterol esters - cholesterol

19
Q

What is hyperlipoproteinaemia?

A

Increased level of one or more of the plasma lipoproteins

20
Q

Describe type 1 hyperlipoproteinaemia

A

Chylomicrons present in fasting glucose, caused by defective lipoprotein lipase

21
Q

Describe type 2a hyperlipoproteinaemia

A

Raised LDL, associated with coronary artery disease that may be severe, unknown defect

22
Q

Describe type 2b hyperlipoproteinaemia

A

Raised LDL and VLDL, associated with coronary artery disease, unknown defect

23
Q

Describe type 3 hyperlipoproteinaemia

A

Raised LDL and chylomicrons remnants, associated with coronary artery disease, defective apoprotein (Apo E)

24
Q

Describe type 4 hyperlipoproteinaemia

A

Raised VLDL, associated with coronary artery disease, unknown defect

25
Q

Describe type 5 hyperlipoproteinaemia

A

Raised chylomicrons and VLDL in fasting plasma, associated with coronary artery disease, unknown defect

26
Q

What is familial hypercholesterolaemia?

A

Condition in which there may be an absence (homozygous) or deficiency (heterozygous) of functional LDL receptors.

27
Q

How can you diagnose hypercholesterolaemia?

A

Characterised by elevated levels of LDL and cholesterol in the plasma. Homozygotes - extensive atherosclerosis early

28
Q

How would you treat hyperlipoproteinaemias?

A

Diet and lifestyle modifications, drug therapy (statins)

29
Q

How does the liver dispose of cholesterol?

A

Converts it into bile. Bile salt sequestrants increase disposal from body - act by binding to bile salts in GIT, promoting their loss in faeces

30
Q

What are micelles?

A

Small assemblies of lipid molecules surrounded by polar molecules

metabolism (17 decks)

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