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Biology - Macromolecules > Lipid Metabolism > Flashcards

Lipid Metabolism Flashcards

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1
Q

How much of dietary fats do TAGs constitute?

A

90%, being manor form of metabolic energy storage.

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2
Q

What do TAGs consist of?

A

Glycerol backbone and a trimester of fatty acids.

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3
Q

Why does lipid digestion take place at the water-lipid interface?

A

Because TAGs are water insoluble yet their enzymes are water soluble.

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4
Q

What is rate of lipid digestion dependent on?

A

Surface area of the water-lipid interface.

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5
Q

What increases rate of lipid digestion?

A

Churning peristaltic movements of the intestine, and emulsifying action of bile acids.

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6
Q

Bile Acids

A

Amphiohatic detergent like molecules that solubulise fat globules.

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7
Q

Where do Bile Acids come from?

A

Synth in the liver from cholesterol, secreted as glycine or taurine conjugates into the gall bladder for storage.

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8
Q

Where on TAGs does hydrolysis occur?

A

1 and 3 alpha carbon by lipases.

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9
Q

Where on TAGS does lipase hydrolysis take place?

A

1 and 3 alpha carbon

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10
Q

What does lipase TAG hydrolysis form?

A

1,2 diacylglycerols and 2-acylglycerols.

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11
Q

Interfacial Activation

A

The increase of lipase activity at lipid-water interface.

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12
Q

What is Lipase dependent on for binding to the LW interface?

A

Mixed micelles of phosphatidylcholine and bile acids and pancreatic colipase.

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13
Q

What is the process if interfacial Activation?

A

The lipase active site within its NTD contains a catalytic domain: this is covered by a 25 residue helical lid in the absence of micelles, of which remove this lid through CC, revealing a expansion hole, generating a hydrophobic surface at the active site.

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14
Q

What does colipase do proceeding interfacial activation?

A

Colipase binds CTD of lipase, in a way the hydrophobic tips of its three loops extend from the complex, creating a continuous hydrophobic plateau, assisting in binding complex to lipid surfaces.

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15
Q

Where does lipid absorption take place?

A

Cells lining the small intestine of the fatty acid and glycerol products.

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16
Q

When does lipid digestion take place?

A

Proceeding intestinal metabolism.

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17
Q

How do Bile Acids play roles in lipid digestion?

A

Permit transport of non polar lipid degraded products across the intestinal wall.

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18
Q

What do FA form upon absorption?

A

Complexes with Intestinal Fatty Acid Binding Protein in the cytoplasm.

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19
Q

Why does FA need to bind IFABP?

A

It increases FA solubility.

20
Q

Intestinal Fatty Acid Binding Protein

A

This coordinates lipid transport and metabolism.

21
Q

What is the structure of IFABP?

A

10 antiparralel beta pleated sheets, between of which the fatty Cids occupy parallel to the strands.

22
Q

What happens to FA after Binding IFABP?

A

Transport to other tissues for metabolism or storage in the form of lipoproteins.

23
Q

Lipoproteins

A

Globular, micelles like particles consisting of a non polar core of TAGS, surrounded by an amphiphilic coating of proteins, phospholipids and cholesterol.

24
Q

What upon absorption are FA packaged into?

A

Lipoproteins called Chylomicrons

25
Q

What is the FA packaged CM pathway?

A

Release into intestinal lymph, transported through lymph vessels, draining into veins, then circulating throughout body.

26
Q

Where are VLDLs, LDLs and IDLs synthesised?

A

Within the liver

27
Q

Function of Lipopeoteins?

A

Transport endogenous TAGS and cholesterol to required tissues.

28
Q

Structure of Apolipoprtoein B-100

A

A large 4536 residue monomer with high hydrophobcity, found once on LDL, covering half the particle surface.

29
Q

What are characteristics of ALPs?

A

Water soluble, associate weakly with LP, high helical contact.

30
Q

Why does ALP helical content increase when Binding to LP?

A

Contact with hydrophobic surfaces favours helical formation, satisfying hydrogen bonding potential of proteins polar backbone group.

31
Q

Function of VLDL

A

Transport endogenous TAGS and cholesterol.

32
Q

Where are VLDLs degraded?

A

In adipose/muscle tissues by lipoprotein lipases.

33
Q

What happens when VLDL are degraded?

A

Internal FA release where they’re absorbed ht cells and oxidized for energy, or used to resynthesie TAGS.

34
Q

What happens to TAG glycerol backbone after VLDL degradation?

A

Transport to liver/kidneys converted to the glycolytic pathway.

35
Q

What happens to the VLDL remenenats after degradation?

A

Appear in circulation as IDL half of which are taken up by the liver, then LDL

36
Q

What do VLDL derived LDLs do proceeding?

A

Taken up by receptor mediated endocyotsis in the liver.

37
Q

How are LDLS sequestered?

A

They bind LDL receptors, which cluster into clathrin coated pits, which invalidate to form clathrin coated vesicles.

38
Q

What is the pathway of LDL sequestered clathrin coated vesicles?

A

Divest their clathrin coating, fusing with endosomes which harbour low pH, dissolving LDL from their receptors.

39
Q

Upon CCV fusion with endosomes, what happens?

A

LDL receptors are recycled and endosomes fuse with lysosomes.

40
Q

What happens to LDL in lysosomes?

A

Apob-100 is degraded into its AA and cholesterol esters hysrolyse into cholesterol and FA.

41
Q

What do HDL function to do?

A

Remove cholesterol from tissues.

42
Q

Where does HDL assembly take place?

A

In plasma from components obtained through LP degradation.

43
Q

How does HDL acquire cholesterol?

A

Extraction from cell surface membranes.

44
Q

What happens to cholesterol after HDL absorbs them?

A

Convert them into cholesteryl esters by lecithin cholesterol acyltransferase.

45
Q

How is HDL absorbed?

A

Binding scavenger receptor class B type 1 on the liver, which transports lipids into the cell, where HDL reenters circulation.

Biology - Macromolecules (16 decks)

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