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Biochemistry > Part 2 - lecture 3 - Exam > Flashcards

Part 2 - lecture 3 - Exam Flashcards

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1
Q

What are the types of lipids found in humans?

A

Fatty acids, triglycerides, phospoglycerides, sphingolipids, steroids, fat-soluble bitamines, eicosanoids, ketone bodies

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2
Q

What are fatty acids?

A

A type of lipid with R-COOH - can be saturated/unsaturated (with 1-5 double bonds), short to very long chain, and branched or unbranched

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3
Q

What are triglycerides?

A

A type of lipid - esters of 3 fatty acids and glycerol (triacylglycerols)

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4
Q

What are phosphoglycerides?

A

A type of lipid - esters of glycerol with 2 fatty acids and a phosphate-containing group (phospholipids) - phosphatidylcholine - serine -inositol, palasmalogen

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5
Q

What are sphingolipids?

A

Sphingosine-containing lipids (glycolipids as a type) which makes up cerbrosides, globosides, gangliosides, sulfatides) and also sphingomyelines as a type

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6
Q

What are steroids?

A

Lipid that contains a sterol ring and are cholesterol derivatives - examples inlcude cholesterol, bile, acids/salts, hormones

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7
Q

What are the fat-soluble vitamins?

A

Types of lipids like vit. A, D, E, and K

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8
Q

What are eicosanoids?

A

Types of lipids like prostaglandins, thromboxanes, leukotrienes

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9
Q

What are ketone bodies?

A

Types of lipids that are produced during fasting

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10
Q

What is the chemical nature of lipids?

A

Hydrophobic or amphipatic (hydrophilic and hydrophobic properties) - most contain fatty acids stored as triacylglycerol

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11
Q

What are examples of totally hydrophobic lipids?

A

Triacylglycerols and cholesterol esters

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12
Q

What is a good example of an amphipatic lipid?

A

Phosphoglycerides

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13
Q

What are the functions of lipids?

A

energy storage, nonpolar surface, lung alveolar integrity, solubilizing nonpolar substances, serve as hormones in metabolic processes

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14
Q

Where can we obtain lipids from?

A

Dietary or synthesize by liver to give triacylglycerols, cholesterol, bile acids and salts, phospholipids and ketone bodies, synthesize by other cells (like immune cells and specialized glands) to give phospholipids, eicosanoids, and cholesterol derivatives

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15
Q

What is the majority of dietary fat composed of?

A

Triglycerides, cholesterol, cholesterol ester and phospholipids

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16
Q

What does the water-insoluble nature of fat cause?

A

Presents as fat droplet-water emulsion in chyme

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17
Q

Where does digestion of lipids begin? and what are the enzymes?

A

Starts in stomach with acid-stable lipases from lingual and gastric origin that digest TAGs with short to medium FA side chains

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18
Q

Where does emulsification of lipids occur and how?

A

Small intestine by bile salts and peristalsis - act as detergents to solubilize fatty acids and monoglycerides, cholesterol, vitamins, lysophospholipids to form mixed micelles

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19
Q

What is an important enzyme of TAG digestion?

A

Pancreatic lipase - anchored to surface of fat droplets by colipase (pancreatic protein) - cleaves 2 FAs from each triglyceride to yield 2-monoglycerides

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20
Q

How are cholesterol esters digested?

A

Cholesterol esterase in pancreatic juice

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21
Q

How are phospholipids digested?

A

Phospholipase A2 in pancreatic juice cleaving one fatty acid to give lysophospholipids and further digestion by lysophospholipase cleaves another FA

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22
Q

How are lipids transported to surface of enterocytes?

A

Micelles - which disaggregate so that lipids enter cells by passive diffusion

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23
Q

What helps with the absorption of long-chain FAs and cholesterol?

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A

FATP4 transporter for long chain and NPC1L1 channel for cholesterol

24
Q

What happens to bile salts?

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A

They are reabsorbed in SI by ileum and are returned to liver to participate in cycles of micelle formation before reabsorption

25
What happens to short and medium chain FAs in the enterocyte?
They are converted to triacylglycerol which can be packaged into chylomicrons - OR - can go right to capillary system and released to herpatic portal vein where they are feed into liver and can enter general circulation where they bind albumin
26
What happens to long chain FAs in the enterocyte?
They enter via the FATP4 transporter and are converted into fatty acyl-CoA which can contribute to give cholesteryl ester and be packaged into chylomicrons
27
What happens to cholesterol in the enterocyte?
Brought in via NPC1L1 channel and converted to cholesteryl ester to be packaged into chylomicrons
28
What happens to chylomicrons?
Can be brought out to lymphatics and through thoracic duct to venous blood to be delivered to peripheral tissues
29
What signals to pancreas to secrete enzymes for lipid digestion?
Food intake and two hormones, secretin and cholecystokinin
30
What is secretin?
An enzyme produced by endocrine cells of the duodenal wall which stimulates secretion of bicarbonate by pancreas
31
What is cholecystokinin?
An enzyme released by endocrine cells of the duodenum to act on acinar cells of the pancreas to stimulate digestive enzyme secretion and cause gallbladder to contract and deliver bile into the duct
32
What happens to long chain FA and short chain in mucosal cell and where?
On the ER - FAs >10-12C are turned into triglycerides and cholesterol which is packaged int chylomicrons - <10C pass through enterocyte and released to heaptic portal vein to go to liver
33
What happens to chylomicrons and what are they carrying?
Carrying triglycerids and cholesterol from FAs and phospholipids and go through thoracic duct from mucosal cells to lymphatic system to systemic veins to adipose and muscle and chylomicron remenants go to liver
34
What is the inter-organ transport of dietary lipids?
From the intestine they are packaged into chylomicron to go to periphery and adipose
35
What is the inter-organ transport of newly synthesize lipids?
Made in liver - packaged into VLDL to go to periphery and adipose Or ketone bodies made in liver go to periphery and then target cells
36
What is the inter-organ transport of stored lipids?
From adipose go to blood bound to albumin where it goes to periphery and target cells
37
What does albumin bind and what does it do?
Binds to free FAs liberated from adipose storage to act as a vehicle - not needed to move ketones
38
Why can chylomicrons travel through blood?
Polar on the outside
39
What are plasma lipoproteins?
Delivery vehicles synthesized in intestine and liver composed of various lipids and apoproteins to give lipid-protein complexes
40
Are lipoproteins hydrophilic or hydrophobic?
Hydrophilic outer layer made up of apoproteins and phospholipids with inner hydrophobic nucleus of triacylglycerol and cholesterol ester
41
What are apoproteins used for on lipoproteins?
Give recognition by receptors
42
What are the types of lipoproteins?
VLDL, LDL, HDL and chylomicron
43
Where are chylomicrons formed and what do they do?
A type of lipoprotein - Formed in intenstine and absorb and transport triglycerides (large proportion), cholesterol and vitamins -- FAs to be taken up by adipose and chylomicron remnants deliver cholesterol to liver
44
What is VLDL, where is it formed?
A type of lipoprotein - synthesized in liver and packages triglycerids and cholesterol -- FAs from triglycerides brought to adipose and cholesterol brought to liver by LDLs (interconversion by IDLs)
45
What is IDL?
Intermediate density LPs that convert VLDL to LDL to bring cholesterol to liver
46
What is HDL
A type of lipoprotein - "good cholesterol" - synthesized by liver and intstine and picks up cholesterol from periphery and from LDL and brings to liver
47
What is LDL?
"Bad cholesterol" - high level cholesterol in center
48
What is the apoprotein on chylomicrons, VLDL and HDL?
Chylomicrons - B-48 | VLDL and HDL - B100 (liver derived only)
49
What are the relative sizes of lipoproteins?
HDL < LDL < VLDL < Chylomicron
50
How are chylomicrons metabolised?
assembled in intestine and excreted to lymphatics and then to blood -- HDL transfers ApoCII and ApoE -- lipoprotein lipase on tissues surface activated by ApoCII to hydrolyzes TGs to glycerol and FAs -- now rich in cholesterol and CE -- loses ApoCII to HDL and delivers cholesterol to liver which recognizes ApoE and takes up remnants by endocytosis
51
What is the role of ApoE and ApoCII in chylomicron metabolism?
ApoCII is recognized by lipoprotein lipase on tissues surfaces to hydrolyze TGs to glycerol and FAs ApoE recognized by liver when cholesterol is being delivered and signals endocytosis or remnants
52
What stimulates lipoprotein lipase?
Insulin - with a low Km in heart and High Km in adipose
53
What is VLDL metabolism?
Synthesized by liver and secreted to blood by newly synthesized FAs and cholesterol - FAs taken up - converted to LDLs to deliver cholesterol to peripheral tissues and back to liver -- ApoCII and ApoE transferred by HDL -- LDL formed and bind to liver and extrahepactic tissues by ApoB100 - giving cholesterol to both
54
What is HDL metabolism?
HDL made my liver and intestine -- reservoir for ApoE and CII to donate to chylomicrons and VLDL -- cholesterol from peripheral tissue is brought into HDL and esterfied by LCAT (from liver) which is activated by ApoA1 -- HDL returns cholesterol to liver via SRB1 receptor
55
How does the liver take up cholesterol?
Cholesterol from LDL and chylomicron remnants are taken up by apoB100/apoE receptor where is separates from lipoprotein -- can be used for hormone synthesis, storage by ACAT enzyme or eliminated by bile acids

Biochemistry (19 decks)

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