Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
8 Cards in this Set
- Front
- Back
|
1. Cofactor for oxidases involved in:
- Hydroxylation of lysine and proline – necessary for collagen formation - Synthesis of carnitine – transport of long chain fatty acids to mitochondria - Synthesis of norepinephrine (neurotransmiter) 2. Non-enzymatic reducing agent - Facilitates absorption of iron by reducing it to ferrous - Enhances utilization of folic acid by converting it to tetrahydrofolate - General antioxidant - Metabolism of cholesterol to bile acids |
Roles of vitamin C
Ascorbic acid or ascorbate: is a six-carbon lactone which is synthesized from glucose by many animals Human & other primates - are unable to synthesize vitamin C because they lack the terminal enzyme in the biosynthetic pathway, L-gulonolactone oxidase |
|
|
This process describes the absorption of which molecule?
Undergoes oxidation (DHAA) prior to absorption (preferred form) Active transport across intestinal membrane (sodium dependent). Diffusion in mouth Sodium-independent transport system across the basolateral membrane (to plasma) Saturable transport Absorption inhibited by pectin and zinc May be destroyed before absorption by high iron concentrations in diet |
Absorption of vitamin C
Saturable - Better to take several doses than one big dose High iron may interfere with vitamin C absorption |
|
|
Which vitamin is destroyed by UV light?
|
Riboflavin
|
|
|
First symptom of methyl trap.
|
Megaloblastic anemia
|
|
|
They dissolve in fat.
They are absorbed from the small intestines, along with dietary fat, which is why fat malabsorption resulting from various diseases (e.g., cystic fibrosis, ulcerative colitis, Crohn's disease) is associated with poor absorption of these vitamins. Fat-soluble vitamins are primarily stored in the liver and adipose tissues. |
Fat soluble vitamins (A, D, E, K)
With the exception of vitamin K, fat-soluble vitamins are generally excreted more slowly than water-soluble vitamins, and vitamins A and D can accumulate and cause toxic effects in the body |
|
|
Vitamin D obtained from sun exposure, food, or supplements is biologically inert
Vitamin D undergo two hydroxylations for activation. First: in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], or calcidiol. Second: in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], or calcitriol |
Vitamin D3 (cholecalciferol) can be synthesized by humans in the skin upon exposure to ultraviolet-B radiation from sunlight or it can be obtained from the diet
|
|
|
In Bone formation
- Essential for promoting calcium absorption in the gut - Maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone - Needed for bone growth and bone remodeling by osteoblasts and osteoclasts - Stimulates cell differentiation - Modulate immune system - Plays a role in insulin secretion under conditions of increased insulin demand - Decreases the expression renin (renin-angiotensin system that regulate blood pressure) |
Roles of Vitamin D
|
|
|
1. Low serum calcium: the parathyroid glands secrete parathyroid hormone (PTH)
2. PTH stimulates the activity of the 1-hydroxylase enzyme in the kidney => increased calcitriol 3. Calcitriol restores normal serum calcium by: a) activating the vitamin D-dependent transport system in the small intestine, increased absorption b) increasing the mobilization of calcium from bone into the circulation c) by increasing the reabsorption of calcium by the kidneys. |
Mechanism of calcium absorption
|
