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;
32 Cards in this Set
- Front
- Back
|
In the phototransduction visual cycle, 11-cis retinal is converted to what?
|
All trans isomer by visible light.
|
|
|
What is the major retinoid hormone of the body?
|
Retinoic Acid
|
|
|
Retinoic Acid is the ligand for what?
|
Nuclear hormone receptors modulating transcription.
|
|
|
Dietary retinol is carried as _______ in _____________
|
retinyl esters
lymph chylomicrons |
|
|
Absorbed beta-carotene is carried in?
|
Chylomicrons
|
|
|
Vitamin A is solube in what type of compound?
|
Fat soluble
|
|
|
Retinoid receptors are similar to what other type of receptors?
|
steroid hormone
|
|
|
What type of cells specially benefit from Retinoic acid?
|
Epithelial
|
|
|
All-trans retinoic acid (tretinoin) is useful in what medically?
|
A variety of dermatalogical conditions such as psoriasis
|
|
|
13-cis retinoic acid (isotretinoin) is used to treat what?
|
Severe acne
|
|
|
What are the complications of 13-cis retinoic acid (isotretinoin)?
|
It is a teratogen. Contraindicated in pregnant women or women with childbearing potential.
|
|
|
What is the major function of vitamin A?
|
Phototransduction
|
|
|
What are light sensitive neurons called that detect light?
|
The rods and cone cells
|
|
|
What are the functions of rod cells and describe their quantity.
|
Most numerous.
Very sensitive to light. Critical for vision in dim light. |
|
|
What are the functions of cone cells and describe their quantity.
|
Very few.
Little light sensitivity, but can discriminate color. |
|
|
Describe the similar structure of rods and cones.
|
Inner segment w/ nucleus and mitochondria
Outer segment with stacks of membranous containing opsin proteins |
|
|
What are opsin proteins and what is their function.
|
Light receptors in the signal transduction process.
Located on the outer segment in stacks of membranous disks. |
|
|
What is Rhodopsin?
|
Rod cell light receptors
|
|
|
What is transducin?
|
Trimeric G-protein of phototransduction
|
|
|
Rhodopsin and transducin are anchored to membrane by what?
|
C-terminal lipid modifications
|
|
|
What is the second messenger in visual receptor cells?
|
cGMP
|
|
|
Light induces what in light receptor cells?
|
Hyperpolarization
|
|
|
Describe the transmembrane potential of the inner segment when in the dark.
|
Low potential produced by Na-K ATPase
|
|
|
When rhodopsin absorbs light, it does what to cGMP?
|
Hydrolyze them
|
|
|
Hydrolysis of cGMP does what to cation channels?
|
Closes them, thus hyperpolarization b/c Na-K ATPase continues to generate electric signal
|
|
|
Discrimination of colors and hues is accomplished by integrating output from what?
|
Three types of cone cells.
|
|
|
Differences in cone cells are seen where?
|
Amino acid differences in the retinal binding site.
|
|
|
If gene rearrangement occurs BETWEEN transcribed regions, then what is the result.
|
Difficulty distinguishing red and green
|
|
|
In gene rearrangement occurs WITHIN transcribed regions, then what is the result?
|
Difficulty discriminating color.
|
|
|
Vitamin A deficiency causes what?
|
Nyctalopia (poor night vision)
|
|
|
No vitamin A causes what? x3
|
Xeropthalmia - no tears
Keratomalacia - dry cornea Corneal erosion |
|
|
Hyperpolarization occurs by blocking what channels?
|
Na+ and Ca2+
|
