Lipids II

Question 1

1. What are functions of a plasma membrane?

Answer 1

protection, cell adhesion, signaling, transport
PAST

Question 2

2. What features does a plasma membrane have with regard to permeability and why is that the case?

Answer 2

impermeable towards hydrophilic molecules because it require a transport ions across membrane

Question 3

3. What are the three major transport types and do they require energy?

Answer 3

passive
active
bulk

*passive transport doesn’t require energy

Question 4

4. What is uniport, symport and antiport (with regard to energy required and molecules moved)?

Answer 4

energy source: ATP
uniport: transport of one molecule into the cell
Energy source: electrochemical gradient
symport: transport of two molecules in the same direction (into cell)
antiport: transport of two molecules in opposite direction

Question 5

5. What are two types of bulk transport and is energy required? What “vessel” is required?

Answer 5

endocytosis: into cytoplasm
exocytosis: out of cytoplasm
*vesicular transport is required to move large molecules OR large amounts of small molecules

Question 6

6. What is an example for an uniporter found in rods, transporting what?

Answer 6

glucose unitporter, GLUT-1

Question 7

7. What is an example for an antiporter found in rods, transporting what?

Answer 7

Na/Ca exchanger (NCx) secondary active transport

Question 8

8. Which for 4 types of multiprotein complexes are found in a membranes involved in transport, signaling, adhesion and protection?

Answer 8

Gap junctions
tight junctions
desmosomes
adherens junctions

Question 9

Which one is the membrane model that is still accepted today and what are the major features of that model?

Answer 9

fluid mosaic model
- fluidity
- dynamic
-molecules floating

Question 10

Which lipid classes are the main types found in plasma membranes?

Answer 10

glycerides (contains glycerol)
non-glycerides (sphingolipids, steroid + cholesterol)

Question 11

Which lipid types are the most abundant?

Answer 11

• Glycerophospholipids/ phosphoglycerides
• Sphingolipids (rafts)
• Cholesterol (rafts)

Question 12

Which 3 types of membrane proteins exist (with regard to location and attachment features)?

Answer 12

intergral membrane proteins
peripheral membrane proteins
lipid-anchored proteins

Question 13

What are the major (important) features of these three membrane proteins types (implied by their name)?

Answer 13

integral - permanently bound
peripheral - temporarily bound
lipid-anchor - permanently placed with anchor

Question 14

Which protein structure of transmembrane (TM) -proteins is the predominant form in our membranes – a helix or b-barrel?

Answer 14

alpha helical is dominant

Question 15

What would be an example for a TM protein that is required for enzymatic activity (type/kind not a specific molecule)?

Answer 15

ATP synthase

Question 16

16. What would be an example for a TM-protein that is required for cell recognition (type/kind not a specific
    molecule)?

Answer 16

T cell receptors , antibodies

Question 17

17. What would be an example for a TM-protein that is required for signal transduction / signaling (type/kind not a
    specific molecule)?

Answer 17

Rhodopsin

Question 18

18. Where in the rod photoreceptor (structure/formation) is rhodopsin predominantly found (enriched) and where in this structure is it located?

Answer 18

Disc Membrane
RPE

Question 19

19. Of which two components is rhodopsin made of (type of molecule and specific name)?

Answer 19

opsin molecule and chromophore (11-cis-retinal)

Question 20

20. What happens to these two components when light hits rhodopsin?

Answer 20

conformational change > all-trans retinal = activated rhodopsin

Question 21

21. What is the name of the G-protein that interacts with activated Rhodopsin?

Answer 21

transducin

Question 22

22. What is the name of the ligand that keeps a special channel open to allow sodium to enter the rod? Bonus: What is the name of that channel?

Answer 22

clyclic GMP , Na+ channels must remain open

Question 23

23. What is the name of the enzyme generating GMP and what is it’s substrate?

Answer 23

phosopdiesterase (PDE)

Question 24

24. In the dark, the rod sodium channels are … resulting in….. resulting in .. resulting in …. ?

Answer 24

low cGMP > Na+ channel blocked > less (+) charge inside cell > hyperpolarization IPSPs

Question 25

25. When light is present, rod sodium channels are … resulting in…. resulting in .. resulting in …. ?

Answer 25

high cGMP > open Na+ channel > more (+) charge inside cell > depolarization EPSPs

Question 26

26. What is the visual cycle?

Answer 26

A chain of biochemical reactions that regenerate the visual pigment

Question 27

27. Which enzymes/enzyme complexes are required in the cycle?

Answer 27

RDH-5/10/11 , RDH8/12, LRAT, RPE65

Question 28

28. Starting with all 11-cis retinal converted to all-trans retinal which products (3) are generated in the cycle until 11-cis retinal is renewed (correct sequence)?

Answer 28

all trans retinal
all trans retinol
11 cis retinol

Question 29

29. If proteins or enzymes in a retinal cell are not build or functioning, what will be the outcome?

Answer 29

congenital blindness in children

Question 30

30. What can you do to protect your cells (not just in your eyes) and ensure proper functionality?

Answer 30

minimize smoking habits, increase nutrition, and absorb healthy amounts of UV light

Question 31

Bonus: Why can water (polar) pass through a lipid bilayer (made of amphipathic molecules)?

Answer 31

osmosis occurs through pores