9/9/24 Membrane Structure and Composition

Question 1

what membranes wrap the cell, separating it from the outside and dividing it into compartments?

Answer 1

lipid (=”oily”) membranes

Question 2

how are liposomes prepared in the lab?

Answer 2

prepared in
the lab by assembling
synthetic lipids or breaking
cell membrane

Question 3

what are vesicles?

Answer 3

naturally occurring cell
organelles with aqueous cavities

Question 4

the cell envelope is a biological membrane made of __________
molecules

Answer 4

amphiphilic phospholipid

Question 5

A biological membrane is an
enclosing or separating thin layer
of material that acts as a ________________________________________________________________

Answer 5

selectively permeable barrier

Question 6

describe the thin lipid layer that is trapped by the biological membrane

Answer 6

not
permeable to many small
compounds and large molecules

Question 7

the phospholipid monolayer consists of what liquid

Answer 7

oil

Question 8

the phospholipid bilayer

Answer 8

water

Question 9

what are examples of small molecules that diffuse across lipid bilayer:

Answer 9

Co2, 02, H20

Question 10

what are molecules that the lipid bilayer cannot diffuse across ?

Answer 10

Ions, and larger uncharged molecules such as glucose,
can not diffuse across.

Question 11

what are the characteristics of the amphiphilic molecules in the phospholipid double layer

Answer 11

they have hydrophilic and hydrophilic sides

Question 12

what are the role of proteins in the membrane?

Answer 12

control its permeability to
different compounds, sense the outside, and trigger intracellular
response signals.

Question 13

what are the roles of sterols in the membrane?

Answer 13

control membrane properties

Question 14

True or False: Lipids are the only components of the membrane.

Answer 14

False. Lipids are not the only components of the membrane.

other components include:
-proteins & sterols
-carbohydrates

Question 15

what roles do lipids play in the membrane?

Answer 15

-compartmentalization
- metabolic energy conversion via oxidation
- control of metabolic processes (steroid hormones & prostaglandins)

Question 16

What does the consistency of the membrane depends on?

Answer 16

composition and temperature

ex: when membrane undergoes heat it transforms from a gel-like consistency to a fluidlike consistency

Question 17

define micelle

Answer 17

cone-shaped amphiphilic molecules forming curve structures

Question 18

define bilayer

Answer 18

Cylinder-shaped amphiphilic molecule

ex: phospholipids

Question 19

Bilayer thickness & curvature are affected by what?

Answer 19

Liquid composition

Question 20

what are the building blocks of lipids?

Answer 20

fatty acids

Question 21

what structural lipid is primarily found in membranes?

Answer 21

sterols

Question 22

what are the simplest lipids ?

Answer 22

fatty acids

Question 23

describe a hydrocarbon long hydrocarbon chain

Answer 23

16-18 carbons ending with a carboxyl group

Question 24

the saturated chain adopts ________ conformations

Answer 24

extended

Question 25

unsaturated fatty acids have one or more _______________

Answer 25

double bonds

Question 26

double bonds in natural unsaturated fatty acids introduce

Answer 26

a kink

Question 27

double bonds in natural unsaturated fatty acids are commonly in what configuration

Answer 27

cis config

Question 28

what is an essential polyunsaturated fatty acid (PUFA) needed in the diet for synthesis of critical signaling molecules like Arachidonic Acid

Answer 28

Omega-3

Question 29

the extent of packing depends on the degree of _________

Answer 29

saturation

Question 30

the longer the chain.....

Answer 30

the more organized the less fluid

Question 31

the more (cis) double bonds.....

Answer 31

the more disorganized the more fluid

Question 32

how do trans fatty acids form

Answer 32

by partial breakdown of unsaturated fatty acids (usually industrial)

Question 33

a trans double bond allows a given fatty acid to adopt what

Answer 33

extended conformation

Question 34

trans fatty acids can pack

Answer 34

more regularly, show higher melting points than cis forms

Question 35

trans fatty acids have

Answer 35

higher melting points than cis forms

Question 36

True or False: trans unsaturated fatty acids raise your "good" cholesterol

Answer 36

it raises your "bad" cholesterol

Question 37

which double bond forms a kink

Answer 37

cis double bond

Question 38

how can fatty acids be linked through Glycerol

Answer 38

triacyclglycerols (TAG)

Question 39

what does TAG consist of

Answer 39

glycerol + 3 fatty acids

Question 40

what form are majority of the fatty acids found in

Answer 40

TAGs

Question 41

what are solid TAGs called?

Answer 41

fats

Question 42

what are liquid TAGs called?

Answer 42

oils

Question 43

what are the primary storage forms of lipids (body fat)?

Answer 43

TAGs

Question 44

where do TAGs exist?

Answer 44

in the cytoplasm as droplets/deposits

Question 45

why are TAGs less soluble in water than fatty acids?

Answer 45

lack of charge carboxylate group

Question 46

Mixtures of TAGs differ in their _____________

Answer 46

fatty acid composition

Question 47

fatty acid composition of which three food fats?

Answer 47

olive oil, butter, and beef fat

Question 48

Why do fats and oils float?

Answer 48

because TAGs are less dense than water

Question 49

How are cell membrane lipids formed?

Answer 49

fatty acids combine through scaffold to a head group

Question 50

What are Glycerol and Sphingosine used by?

Answer 50

the scaffold to connect 1-2 hydrophobic fatty acids + polar head group

Question 51

True or False: in the phospholipid bilayer the head is hydrophilic.

Answer 51

True. Hydrophilic head

Question 52

True or False: in the phospholipid bilayer the tail is hydrophobic

Answer 52

True. hydrophobic tail