Vitamins and Lipids - Skildum

Question 1

After ingestion, how do triacyglycerols travel through the gut lumen?

Answer 1

The gall bladder secretes bile salts that emulsify the TG’s.

Question 2

What is the next step of TG’s after being emulsified by bile salts?

Answer 2

Lipase and colipase released from the pancreas breaks TG’s into a fatty acid and 2 monoacyglycerols.
They are then reemulsified in a bile salt micelle.

Question 3

What happens to the micelle containing 2 Monacyglycerols and a TG?

Answer 3

They are taken up by intestinal epithelium and Triacyglycerols are reformed. Then they are packaged in chylomicrons and transported through the lymph to get to the blood.

Question 4

What is the major apoprotein in chylomicrons?

Answer 4

ApoB-48

Question 5

What is the difference between ApoB-48 in chylomicrons and the ApoB-100 found in hepatocytes?

Answer 5

They come from the same gene in DNA. The difference is that after transcription, the RNA that makes ApoB-48 is EDITED. A stop codon is added in producing a smaller mRNA and protein

Question 6

How does HDL affect chylomicrons after they have entered the blood?

Answer 6

HDL transfers ApoCII and ApoE onto the nascent chylomicron transforming it into a mature chylomicron

Thats metamorphosis! (random comment to no one)

Question 7

What activates Lipoprotein Lipase (LPL) ?

What does it do?

Answer 7

LPL is activated by ApoCII.
LPL is found in the capillary beds of muscle and adipose tissue.
LPL cleaves chylomicrons into FA’s, glycerol, and chylomicrons remnants

Question 8

After LPL breaks up the chylomicron. Where do the FA’s, glycerol, and chylomicron remnants go?

Answer 8

FA’s: Oxidized in muscle or stored as TG’s in adipose tissue

Glycerol: Back to the liver

Chylo Remnants: Back to the liver

Question 9

FA’s and cholesterol grabbed by the liver from chylo-remnants can be repackaged to serve a very similar function as chylomicrons. Explain

Answer 9

Can be repackaged with ApoB-100 as VLDL (very low density lipoprotein).

VLDL also delivers FA fuels to the body tissues

Question 10

Why is it only possible for adipose tissue to store FA’s as TG’s in the fed state?

Answer 10

BECAUSE the glycerol-3-phosphate backbone required to form TG’s can only be produced by glycolysis in adipocytes

Question 11

What kinds of cells serve as a storage reservoir for Vitamin A?

Answer 11

Stellate cells of the liver

Question 12

What proteins are important for blood transport of retinol and retinoic acid?

Answer 12

Retinol = RBP (retinol binding protein)

Retinoic Acid = Complexes with albumin

Question 13

Active form of Vitamin A?

Answer 13

All-trans-retinol

Question 14

Rod cell rhodopsin is a complex of two molecules:
Opsin and _______.
When light strikes it a conformation change then converts _______ to _________.

Answer 14

Rod cell rhodopsin is a complex of two molecules:
Opsin and cis-retinal.
When light strikes it, a conformation change then converts cis-retinal to trans-retinal.

This conversion activates a g-protein and Na channel –> boom sight!

Question 15

How does Vit A affect the immuen system?

Answer 15

Retinoic acid actually plays a role in maturing dendritic cells and recruiting antibody-secreting cells to the small intestine.

Question 16

Complications of Vit A Deficiency?

Answer 16

Anorexia
Retarded growth
Infections
Alopecia
Epithelial cell keratinization
Night blindness, xeropthalmia, Bitot's spots (keratin build-ups)

Question 17

Most important complication to remember with Vit A toxicity?

Answer 17

Teratogenic effect

Question 18

Vit E deficiency is rare unless you have an absorption problem. Premies, Chrohn’s, short bowel, etc.
What would the clinical manifestations include?

Answer 18

Myopathy
Hemolytic anemia
Peripheral neuropathy
Loss of vibratory sense - ataxia

Question 19

Vit E function?

Answer 19

Cellular oxidative stress defense
Especially in membranes

Possibly why myopathy occurs without it

Question 20

2 main forms of Vit K. Phylloquinone and Menaquinone. Where are they found?

Answer 20

Phylloquinone = leafy green vegetables

Menaquinone = produced by fermentation (in gut, or can be found in cheese)

Question 21

Which vitamin inhibits Vitamin K absorption and metabolism?

Answer 21

Vit E

Question 22

How could Vit K deficiency result in a patient with increased prothrombin time and increased bleeding?
(Rare, by the way)

Answer 22

Vitamin K acts as a cofactor for gamma-glutamyl carboxylase.
Which activates blood-clotting proteins

Factor 9, 7a, 10, and prothrombin are all Vit-K-Dependent!

Question 23

What foods is Vitamin D found in?

Answer 23

Animal origins:

liver, eggs, fish, dairy products, shitake mushrooms

Question 24

In order to synthesize Vit D de novo, what organs are required?

Answer 24

Skin, liver, kidney

Question 25

Why is the parathyroid gland important vor Vit D synthesis?

Answer 25

In order for kidney to convert Vit D to its active form it must be acted upon by PTH, produced int he Parathyroid gland.

PTH is produced in response to low calcium conentrations

Question 26

When Vit D binds to VDR it induces transcription events to increase Ca in the blood. What are some of these proteins created?

Answer 26

Ca channel TRPV6 at the intestinal brush border, calbindin in cytoplasm, Ca-ATPase pumps on basolateral membrane, and claudin to allow more Ca across tight junction.

Question 27

Vit D is the most likely Vitamin to have toxic effects. What are the effects?

Answer 27

Calcification of soft tissues (kidneys, heart, lungs, vessels)
Hyperphosphatemia
Hypertension

Question 28

Problems associated with Vit D deficiency?

Answer 28

Rickets - seizures, growth retardation, failure of bone mineralization
Osteomalacia is the adults form

Question 29

most calorically dense food?

Answer 29

fat!

Question 30

Which molecule’s function is to maintain cholesterol and apoprotein homeostasis.

Answer 30

HDL