B10 Flashcards
Explain the role of cis- and trans- retinal in vision.
- vitamin A is oxidized to cis- retinal
- it has a conjugated system which allows for absorption of visible light
- cis-retinal is bound to opsin and forms rhodopsin
- visible light absorbed by Cis-retinal which is converted into trans-retinal
- 11-trans retinal no longer fit
into the rhodopsin. - It leads to the conformational change in rhodopsin triggering an impulse to be sent to the brain
- trans retinal is converted back to cis-retinal through enzyme activity
Most naturally occuring carbohydrates are…
D
(chiral carbon atom furthest away from the ketone or aldehyde group has OH hroup on the dexter (right side))
what is the difference between alpha and beta monosaccharides?
alpha have OH group below the plane of the ring
glycogen, starch, cellulose compare the structure
- cellulose beta, 1-4- glycosidic bonds
- starch (amylose and amylopectin (1,4 and 1,6) alpha linkages)
- glycogen alpha 1,4 and 1,6 but more branched than starch
What fatty acids have higher boiling point and why?
- trans becasue they are straight and can be packed more closely, stronger London forces
In what form do fatty acids exist?
19/20 (glycine doesn’t have a chiral carbon) exist in L form
CORN spelled to the left (anticlockwise) 🔄
They are levorotatory meaning they rotate the plane of plane polarized light to the left
In what process are unsaturated fatty acids converted to their trans form (partial…) or saturated fatty acids?
Hydrogenation, Ni as a catalyst
In partial hydrogenation - cis to trans
In hydrogenation - unsaturated to saturated
Hydrogenation makes fats harder ( because increase in melting point)
Decreases the rate of oxidation (longer shelf life)
Trans fats are Hard to metabolize, they accumulate in the body
Why are trans fats unhealthy?
They increase LDL levels
Lower HDL levels
