Polvi lec #2

Question 1

Can you visualize cell membranes using a light microscope? why or why not?

Answer 1

No, because the cell membrane is too small (5-10nm wide).

Question 2

When were plasma membranes first observed? Using what?

Answer 2

They were first observed in the 1950s using an electron microscope

Question 3

What are membranes composed of? How was this discovered?

Answer 3

lipids, Overton found this by dipping the plant root hairs into solution and found that they more readily took up nonpolar solutes

Question 4

Membranes have how many layers? How was this found?

Answer 4

Membranes have two layers (bilayer) and this was found by Gorter and Grendel in 1925 which showed that lipids from a red blood cell could cover the cell twice.

Question 5

Why did Gorter and Grendel use a red blood cell in their experiment?

Answer 5

Because they didn’t have any interior membranes, only one

Question 6

What two things do membranes have?

Answer 6

lipids and proteins

Question 7

What this the membrane bilayer composed of?

Answer 7

Phospholipids

Question 8

Where do polar phosphatesbl face?

Answer 8

the membrane surface (where aqueous stuff is)

Question 9

Where do nonpolar fatty acid tails face?

Answer 9

Into the interior of the membrane (so they don’t interact w polar water)

Question 10

What does the lipid bilayer prevent?

Answer 10

Prevents random movement of substances in and out of the cell

Question 11

What is the structure of fatty acids?

Answer 11

They are long unbranched hydrocarbon chains, have typically 14-20 carbons, can saturated or unsaturated

Question 12

What are saturated fatty acids?

Answer 12

Lack double bonds

Question 13

What are unsaturated fatty acids?

Answer 13

Has one or more double bonds
introduces a bending in the fatty acid

Question 14

What kind of double bonds do naturally occurring fatty acids have?

Answer 14

cis

Question 15

What do unsaturated fatty acids do to phosolipids packing?

Answer 15

The bend stops phospholipids from packing tightly

Question 16

What are membrane lipids?

Answer 16

are lipids that make up the membrane

Question 17

What are the three kinds of membrane lipids?

Answer 17

Phosphoglycerides
Sphingolipids
Cholesterol

Question 18

Are all phosphoglycerides phospholipids?

Answer 18

yes

Question 19

Are all sphingolipids phospholipids?

Answer 19

no only some

Question 20

Most membrane phospholipids are what?

Answer 20

phosphoglycerides

Question 21

What are the components of phosphoglycerides?

Answer 21

glycerol back bone, two fatty acid chains, a phosphate group, and an additonal group

Question 22

What types of fatty acid chains do phosphoglycerides commonly have?

Answer 22

One unsaturated and one saturated fatty acid chain

Question 23

What are the 5 different types of phosphoglycerides? What are they differentiated by?

Answer 23

Phosphatic acid
Phosphatidylcholine
Phosphatidylserine
Phosphatidyl-ethanolamine
Phosphatidylinositol
They are differentiated by their head groups

Question 24

What the overall charge of phosphatidic acid?

Answer 24

Additional group is H, so negatively charged

Question 25

What is the overall charge of phosphatidylcholine?

Answer 25

Has a choline additional group, is neutral

Question 26

What is the overall charge of phosphatidylserine?

Answer 26

Has a serine additional group, is negatively charged

Question 27

What is the overall charge of phosphatidyl-ethanolamine?

Answer 27

Has a ethanolamine additional group, is neutral

Question 28

What is the overall charge of Phosphatidylinositol?

Answer 28

Has an inositol additional group, is negatively charged

Question 29

What is a polar head group?

Answer 29

P group plus additional group

Question 30

Are sphingolipids less or more abundant in membranes?

Answer 30

less

Question 31

What is the structure of sphingolipids?

Answer 31

Built on a sphingosine spine, so has a polar head group and hydrophobic tail, the sphingosine is attached to a fatty acid, the polar head group can also attach to additional groups

Question 32

What is the most basic example of a sphingolipid?

Answer 32

ceramide, made of just sphingosine and fatty acid

Question 33

Sphingolipids are hydrophobic or hydrophillic?

Answer 33

Neither, they are amphipathic

Question 34

What is sphingomyelin?

Answer 34

is a sphingolipid with a phosphorylcholine group attached, this makes it also a phospholipid

Question 35

What has more longer and saturated fatty acid tails, sphingolipids or phosphoglycerides?

Answer 35

sphingolipids

Question 36

What are the roles of sphingolipids?

Answer 36

signal transduction, membrane structure, and sensing

Question 37

If the additional group to a sphingolipid is a carbohydrate. what is the molecule called?

Answer 37

A glycosphingolipid (in short a glycolipid)

Question 38

What two types of glycolipids are there?

Answer 38

cerebrosides and gangliosides

Question 39

What is a cerebroside?

Answer 39

a glycolipid where the carbohydrate additional group is a simple sugar (for ex galactose)

Question 40

What is a ganglioside?

Answer 40

a glycolipid where the carbohydrate addition is a clusters of sugars that includes sialic acid

Question 41

Membranes in the nervous system have a lot of what?

Answer 41

glycosphingolipids

Question 42

What can alterations in glycolipid abundance result in?

Answer 42

neurological diseases

Question 43

What is tay sachs disease? How does it connect to the neurological diseases we see when glycolipid abundance gets altered?

Answer 43

Is a deficiency of an enzyme that normally breaks down GM2 ganglioside, this causes excess GM2 buildup and impairs the function of nerve cells

Question 44

Is cholesterol flexible? Why or why not?

Answer 44

No, because it has large carbon chains

Question 45

How much of the plasma membrane lipid sin animal cells does cholesterol make?

Answer 45

50%

Question 46

What is cholesterols structure?

Answer 46

Has a polar head group, and big carbon chains

Question 47

Where is cholesterol oriented in the membrane?

Answer 47

oriented with small hydrophilic groups which face the membranes surface, rest of it is the fatty acid tails of phospholipids

Question 48

What do cholesterols do the movement of fatty acid tails in phosphlipids?

Answer 48

slow it down cause it's big and bulky

Question 49

Are the lipids found on the two layers of membrane the same?

Answer 49

No, ratios of exoplasmic (facing outside) and cytosolic (facing inside) vary of each lipid

Question 50

Which lipids are more exoplasmic?

Answer 50

sphingomyelin, phosphatidylcholine

Question 51

Which lipids are more cytosolic?

Answer 51

phosphatidylserine phosphatidylethanolamine phosphatidylinositol

Question 52

What lipids are equals parts cytosolic and exoplasmic?

Answer 52

cholesterol

Question 53

What does membrane lipid asymmetry affect? give examples?

Answer 53

Asymmetry affects membrane permeability, surface charge, membrane shape, and stability Phosphatidylethanolamine- promotes curvature of membrane phosphatidylserine- has a negative charge which interacts with transmembrane proteins Phosphatidylinositol- has roles in signal transduction

Question 54

10% of membrane carbs are covalently linked to what?

Answer 54

lipids

Question 55

50% of membrane carbs of covalently linked to what?

Answer 55

proteins

Question 56

All membrane carbohydrates face what in the membrane?

Answer 56

the extracellular space, only outerleaflet has them

Question 57

Do carbohydrates vary in diff cell types and tissues?

Answer 57

yes

Question 58

What role do carbohydrates play, given an example?

Answer 58

play important roles as receptors, sorting membrane proteins, and cell recognition, theyre the ones that recognize blood type antigens

Question 59

What can lipid composition determine?

Answer 59

the state of the membrane, it can help with protein interactions, and has role sin signal transduction

Question 60

What is myeline sheath composed of?

Answer 60

multiple layers of plasma membrane with very little protein