Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GI- Week 3 > Skildum: Vitamins > Flashcards

Skildum: Vitamins Flashcards

1
Q

Which cofactor is not required by the pyruvate dehydrogenase complex?

A

Biotin (carboxylation cofactor)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the fat soluble vitamins?

A

A, D, E, K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the biologically active form of vitamin A?

A

all trans retiniol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the structural elements of Vit A?

A

B-Ionine ring
branched polyunsaturated chain
alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What can the alcohol of trans-retinol be converted to in the body?

A

aldehyde
carboxylic acid
ester w/ FA (palmitate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the dietary forms of Vit A?

A

retinyl-acyl esters
carotenes (two molecules of retinol)

BOTH can be converted to all trans retinol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is vit A found in?

A

Red, yellow, orange fruits and vegetables

*carrotts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are lycopene, lutein, canthaxanthin?

A

Other forms of Vit A

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the circulating forms of vit A?

A

carboxylic acid
retinoic acid

these are exported into the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens to the esterified retinoic acid esters?

A

Transfered into chylomicrons> enter the lymph system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens to retinoic acid that enters the blood?

A

Majority enters the liver (first organ that gets a crack at vits and nutrients)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What stores Vit A?

A

Vit A>
taken up by hepatocytes>
esterified to fat>
stored in stellate cells (enlarged stellate cells> vit A toxicity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What mediates retiniol homeostasis in the body?

A

hepatocytes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the sources of retinyl to the hepatocytes?

A

dietary: chylomicrons
stored: stellate cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Retinyl esters g out to…

A 
Stellate cells (storage)
VLDL (to tissues)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Retinol goes out to the serum in complex w/..

A

transthyretin

RBP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Retinoic acid goes out to the serum complexed to..

A

albumin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the functions of Vit A in the body?

A

Vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Vit A def?

A

night blindness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Vit A toxicity?

A

blurred vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does light signaling through the eye reach neurons in the brain?

A 
Rhodopsin (Opsin-cis-retinal)>
Light>
conversion to trans-retinal>
activates heterotrimeric G protein>
closure of Na channel>
hyperpolarization of rod cell>
signaling to neuron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Retinoic acid acts as a ligand for RAR, RXR and PPAR which act as…

A

activated TFs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What does retinoic acid as a transcription activator stimulate?

A
  1. differentiation of goblet cells (gut)–> affect absorption
  2. apoptosis of cancer cells (anti-cancer properities)
  3. maturation of dendritic cells
  4. recruitment of Ab secreting cells to small intestine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What does retinoic acid TFs inhibit?

A

keratinization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Carotenes can be cut by monooxygenase to form…

A

molecules of retinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

W/out being cut, carotenes act as ….

A

antioxidants b/c their double bonds can neutralize singlet oxygen and free radicals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the clinical sxs of Vit A def?

A 
anorexia
retarded growth
increased susceptibility to infections
alopecia
keratinization of epithelial cells

eyes: NIGHT BLINDNESS, xeropthalmia, bitot’s spots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How do you diagnose Vit A def?

A

look at the relative dose response:

Measure plasma retinol conc>
give oral bolus of retinyl>
measure plasma retinol conc after 5 hrs

The HIGHER the RDR (liver and stellate cells aren’t maintaining homeostasis) the more the body is relying on short term dietary vit K, rather than liver and adipose stores.

RDRs> 20% indicate the liver is NOT maintaining serum vit K

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the tolerable upper limit for Vit A? And what SE are associated w/ large doses?

A

3000 RAE/day

nausea, vomiting, blurred vision, HA, desquamation of skin, alopecia, ataxia, liver damage, conjunctivitis, eye pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What vitamin and common acne medicine is a teratogen in high doses?

A

Vit A

Acutane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What are the two types of Vit E?

A
  1. tocopherols (saturate 16 C acyl chains)

2. Tocotrienols (polyunsaturated 16 C acyl chains)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Where is Vit E found?

A

plant oils (PALM OIL, sunflower oil, canola oil, wheat germ)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe Vit E digestion/absorption (parallels fat digestion and absorption!)

A 
Tocopherols, tocotreinol-acyl esters>
pancreatic lipase>
tocopherols, tocotrienols>
intestinal epithelial cell>
chylomicrons>
tissues>
chylomicron remnants>
liver>
VLDL>
tissues
34
Q

What type of vit E sterioisomers are exported in VLDL?

A

RRR

35
Q

Where does vit E function?

A

Lipid bilayers in intracellular and plasma membranes.

The phenolic hydroxyl can distribute and stabilize singlet oxygen and free radicals as part of cellular oxidative stress defense

36
Q

What can regenerate Vit E when oxidized?

A

ascorbate (vit C)

37
Q

What does vit E inhibit?

A

Vit K absorption and metabolism

38
Q

What people have Vit E def?

A 
Absorption problems:
premature infants
chrons
short bowel syndrome
inherites lipoprotein disorders
39
Q

A pt presents w/ myopathy, hemolytic anemia, peripheral neuropathy, ataxia, and loss of vibratory sense. Dx?

A

vit E def

40
Q

What is the TUL of Vit E?

A

1000 mg/day

not very toxic

41
Q

What is the main form of Vit K in the diet?

A

phylloquinone from leafy green vegatbles

42
Q

What produces menaquinones?

A

fermentation (in gut, cheese)

Have variable numbers of isoprenoid subunits on the acyl chain

43
Q

What is a synthetic vit K used in animal feed?

A

menadione

44
Q

Describe vit K digestion/absorption.

A 
phylloquinone, menaquinone>
intestinal epithelial cell>
chylomicrons>
tissues>
chylomicron remnants>
liver>
VLDL>
tissues
45
Q

Where is Vit K stored?

A

cell membranes, especially the lung, kidney, bone marrow, adrenal glands

46
Q

What does Vit K do in target cells?

A

Acts as a cofactor for glutamyl carboxylase

47
Q

What does glutamyl carboxylase do?

A

coarboxylates gluatmic side chains on blood clotting proteins

48
Q

What inhibits vit K epoxide reductase?

A

coumadin

49
Q

What cofactors are dependent on Vit K dependent carboxylation?

A

Factor IX (Christmas factor), Factor VIIa, Factor X (Stuart factor), and prothrombin

50
Q

Vit K def can affect what populations?

A

Infants (milk is low in vit K)

People w/ absorption disorders

51
Q

A severe Vit K def can manifest as what type of disorder?

A

coagulation disorder–> increased PTT and increased bleeding

52
Q

Is there a TUL for vit K?

A

no but Menadione causes liver toxicity at high doses

53
Q

Where is vit D found?

A

animal origin: liver, eggs, fatty fish

shitake mushrooms

fortified dairy products

54
Q

Vitamin D can be synthesized de nove from ….

A

cholesterol

55
Q

What is required to make active vit D3?

A

metabolism of skin, liver, kidney

56
Q

What is the most important fxn of Vit D?

A

Ca homeostasis

57
Q

How is Ca homeostasis maintained in the kidney?

A 
When the serum Ca is below a set point>
parathyroid>
PTH>
kidney> 1 alpha hydroxylase>
1,25-OH D2>
bone and gut
58
Q

What does low serum Ca conc trigger in the bone and gut?

A

bone- mobilization of bone Ca

gut- increased Ca uptake

59
Q

What is the dietary form of Vit D and how is it abosrbed?

A

cholecalciferol

passive diffusion w/ fat into intestinal epithelial cells>
transported to tissue in chylomicrons>
taken up by liver in chylomicron remnants

60
Q

What is the main form of Vit D circulating in the blood and the form measured to assess vit D status?

A

25-hydroxycholecalciferol

61
Q

What is considered a healthy amt of vit D?

A

30-40 ng/mL

62
Q

Where makes the biologically active 1,25-OHD3?

A

Acyl hydroxylation in the kidney in response to PTH (produced in response to low Ca)

63
Q

What is VDR?

A

ligand activated TF

64
Q

What genes are regulated by vit D (VDRE)?

A

calcium transport proteins: calbindin, TRPV6, PMCA1b

65
Q

Activated VDR increases expression of…

A
  1. Ca channel TRPV6 at the brush border
  2. Calbindin in the cytoplasm (chaperones Ca from luminal to basolateral side)
  3. Ca ATPase pumps at the basolateral membrane
66
Q

How does VDR affect tight junction permeability to Ca?

A

Low Ca conc–> high vit D conc–> claudin is disrupted–> tight junctions are not so tight–> paracellular transport of Ca and other substances

67
Q

Rickets is associated w/ what def? What is rickets?

A

Vit D

seizures, growth retardation, failure of bone mineralization (osteomalacia)

68
Q

What can cause vit D def?

A

dietary
genetic
secondary to absorption problem like Chrons

69
Q

What vitamin is most likely to have toxic effects?

A

Vit D

70
Q

What is hte TUL of vit D?

A

4000 IU for age 9+

71
Q

What are the toxic affects of Vit D?

A

When serum 25-OHD3> 500 ng/mL calcification of soft tissues (kidneys, heart, lungs, blood vessels), hyperphosphatemia, HTN

(too much Ca uptake from the gut–> Ca going to where you don’t want it to be)

72
Q

s

A

Stem cells secrete Wnt–> maintains stem cells in a dedifferentiated state

B-cat is in association w/ actin cytoskeleton or free in cytoplasm. In an unstimulated cell it binds with the APC protein–> phosphorylation–> ubiquitination and degradation of beta catenin. Normally Beta cateninin is sequestered on teh cytoskeleton or ubiquinated and deegraded.

Wnt binds frizzle and it blocks the GSK3B that phosphorylates B catenein and signals disuprtion through the proteasome. Wnt stabalizes b catenin some enters the nuculeus and becomes a TF.

73
Q

What happens in the absence of Wnt?

A

B catenin is phosphorylated by the APC/axin/GSK3/CK1 complex.

Phosphorylation of b-catenin results in ubiquination and degradation in the proteasome.

74
Q

What happens when Wnt is present?

A

Wnt binds frizzled receptor>
inactivation of the APC/axin/GSK3/CK1 complex>
B catenin remains unphosphorylated>
unphosphorylated b catenin accumulates>
translocates to the nucleus>
binds Lef1/TCF>
activates trxn of target genes (cyclin D1 and myc)

75
Q

What promotes differentiation of intestinal epithelial cells?

A

Gradient of APC and Beta catenin

crypt–de differentiated and have more replication potential (beta catenin)

villus- terminally differentiated, more APC present

76
Q

What occurs early in the development of colorectal cancer?

A

loss of fxn mutations in APC

77
Q

APCmin mice develop…

A

multiple spontaneous tumors

78
Q

VDR null mice recapitulate the phenotype of…

A

rickets (vit d def)

79
Q

VDR null mice have elevated…

A

cylcin D expression

80
Q

VDR null mice have decreased expression of…

A

p21 and p27 expression

81
Q

DHFR is an E2F regulated gene. What level of DHFR expression would you predict in tumor cells from VDR knockout mice relative to tumor cells from wild type mice?

A

DHFR expression is HIGHER in tumors from VDR knockout animals

Tumors WANT to express DHFR

In mice w/out vit D receptor, their tumors have more D1 (oncogene driving cell growth)–> RB–> E2F–> TF for DHFR and many other things.

Vit D receptor is beneficial in keeping colorectal cells in a less dividing phenotype.

82
Q

How does high conc of Vit D relate to the incidence of colorectal adenoma?

A

High conc of Vit D REDUCES the incidence of colorectal adenoma

GI- Week 3 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions