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Flashcards in Cell Membranes Deck (56):
1

A 1 year old girl was brought to the local clinic because of severe abdominal pain. She is pale skinned, shows marked mental retardation, and has an enlarged abdomen. After genetic testing the doctor diagnosed her with Niemann-Pick's disease. The symptoms of this disease are due to the accumuation of which one of the following lipids? A) Sphingomyelin B) Phosphatidylcholine C) Phosphatidylserine D) Cerebroside E) Ceramide

A) Sphingomyelin

2

A medical student was studying the fluidity of the PM of hippocampal neurons. He cultured cells in the presence of a high concentration of fluorescently labeled PUFA's. Examination of the cells under a microscope showed bright fluorescence around the boundary of the cells suggesting that the PUFAs were incorporated into the neuronal membrane. Which of the following statements is the most accurate? A) The PM is likely rigid B) The PM is likely fluid C) The PM has high cholesterol D) The PM has phosphatidylserine facing the outside of the bilayer E) The PM has a 10-fold increase in integral membrane proteins

B) The PM is likely fluid

3

What 3 things make up a cell membrane?

Lipids, proteins and carbs - Arranged in asymmetric bilayer

4

Cell membranes are amphipathic, what does this mean?

They possess a hydrophobic tail and a hydrophilic head group

5

What are the most abundant lipids found in biological membranes?

Phospholipids

6

What is a glycerophospholipid composed of?

Glycerol backbone, with a phosphate and 2 FAs esterified to backbone - Phosphatidylcholine, serine, and inositol

7

What is a sphingolipid composed of?

Sphingosine backbone, with a fatty acid and phosphorylcholine - Sphingomyelin - most common SL present in outer leaflet

8

What are glycolipids composed of?

Sphingosine backbone with carb (oligosaccharide residues)

9

Where are glycolipids found?

Outer leaflet of the lipid bilayer

10

What is cholesterol composed of?

Steroid nucleus with a hydroxy group and hydrocarbon side-chain. The latter interacts with the hydrophobic tails of membrane lipids

11

Where do plaques in Alzheimer's disease occur?

Lipid rafts - If you disrupt the rafts you cant get the plaques

12

Glycolipids, sphingomyelin and phosphatidylcholine are all found where in the PM?

Outer sheet

13

Phosphatidylinositol, serine, and ethanolamine are all found where in the PM?

Inner leaflet

14

_____________ proteins are firmly embedded in the membrane and stabilized by hydrophobic interactions with lipids

Integral membrane proteins

15

___________ proteins are loosely bound to membrane through electrostatic interactions with lipids or proteins

Peripheral proteins

16

_________________ proteins are tethered to membranes via covalent attachment to a lipid

Lipid-anchored proteins

17

Outer sheet of many membranes is covered with a carb shell called a ___________ due to presence of glycolipids and glycosylated proteins

Glycocalyx

18

What are teh 3 key functions of glycocalyx?

Protection, cell adhesion and cell identification - Disruption of the glycocalyx for example could lead to a leaky vessel wall

19

Where is phosphatidylserine found in healthy cells?

In the inner leaflet of bilayer

20

Dying cells are recognized by phosphatidylserine in the outer leaflet and are removed by ___________

Phagocytes

21

Niemann-Pick disease is caused by a deficiency in activity of what?

Acid Sphingomyelinase (A-SMase

22

What is the role of Acid Sphingomyelinase (A-SMase)?

A lysosomal enzyme which breaks down sphingomyelin (SM)

23

What accumulates in Niemann-pick disease and where does it accumulate?

Sphingomyelin accumulates in lysosomes of the liver, spleen and CNS

24

What are the symptoms of Niemann-pick disease?

Enlargement of liver and spleen and neurological damage

25

An incompatible blood transfusion could result in what 3 conditions?

Acute hemolysis, renal failure, and shock

26

What blood type is the universal donor?

Type O because the RBCs have no blood group Ag but it does have Abs against A and B so it can only receive from O

27

What is the universal acceptor?

Type AB because the plasma does not contain any Abs, however they can only give to AB because they have A and B Ags

28

How is the D Ag inherited?

Autosomal dominant

29

Do Rh+ individuals express the D Ag?

Yes -> Rh- do not

30

____________________ is a disease in which incompatibility between blood of mother and fetus

Erythroblastosis fetalis - When mom is Rh- and fetus is Rh+, the mom produces Abs that cross the placenta and can attack the baby

31

What is the structure of a Michelle?

- Monolayer of amphipathic molecules - Formed by surfactant molecules (detergents, emulsifiers) when they are dispersed in polar solvent beyond a critical miceller temp - Small

32

What is the structure of liposomes?

- Bilayer of amphipathic molecules arranged in 2 concentric circles - Formed by phospholipids (hydration of dry lips molecules in a non-polar solvent followed by mechanical agitation) - Large

33

What is the role of micelles

Used to transport hydrophobic molecules

34

What is the role of liposomes?

Can carry hydrophobic and hydrophilic molecules

35

Between micelles and liposomes which is biological and which is artificial?

Micelles are biological(bile salts/ bile acids -> used to digest lipids by increasing access to lipases) Liposomes are artificial (used for drug delivery)

36

What directions can proteins and lipids move in membranes?

Rotate and move laterally

37

Temp at which membranes switch from fluid to rigid state = _____________

Melting temp (TM)

38

Temp >>> Tm = ?

Too fluid

39

Temp > Tm = ?

Optimal fluidity

40

Temp < Tm = ?

Rigid

41

Do long FAs promote increased or decreased membrane fluidity?

Long = rigid Short = fluid

42

What is the role of cholesterol in a rigid versus fluid membranes?

Cholesterol in rigid membrane = increase fluidity Cholesterol in fluid membrane = decrease fluidity

43

When cells are exposed to low temps (

Unsaturated - This lowers the Tm and allows membrane to remain fluid at lower temps instead of transitioning to a rigid semi-crystalline state

44

Spur cell anemia is characterized by elevated levels of ___________ in RBC membrane

Cholesterol - Decreases fluidity and flexibility of membrane and causes RBCs to lyse as they pass through capillaries of the spleen

45

T/F: Membrane proteins and lipids can move from one leaflet of the bilayer to the other

False -> They cannot move leaflets!

46

What is the role of flippases

Move PE and PS from outer to cystolic leaflet

47

What type of ATP do flippases use?

P-type ATPase

48

What types of phospholipids do flippases move?

Phosphatidylethanolamine and serine - More specific for phosphatidyl serine

49

What is the role of floppase?

Moves phospholipids from cytosolic to outer leaflet

50

What type of ATP do floppases use?

ABC transporter

51

What is floppase responsible for moving?

Phosphatidylcholine, sphingomyelin and cholesterol

52

What is the role of scramblase

Moves lipids in either direction, toward equilibrium

53

What type of ATP does scramblase use?

NONE -> scramblase doesnt use energy

54

Label 1 - 3

Q image thumb

1) phospholipid bilayer

2) Phospholipid molecule

3) Hydrophilic heads

A image thumb
55

Label 4-6

Q image thumb

4) Hydrophobic tails

5) glycolipid

6) Cholesterol

A image thumb
56

Label 7, 8, 10

Q image thumb

7) Alpha helix protein (integral)

8) Peripheral protein

10) Glycoprotein

A image thumb