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Biology 1107 Exam 1 > Chapter 6 - Lipids, Membranes, and the First Cells > Flashcards

Chapter 6 - Lipids, Membranes, and the First Cells Flashcards

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1
Q

plasma membrane/cell membrane

A

separates the cell interior from its environment

-made up of selectively permeable bilayers of phospholipids

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2
Q

functions of the plasma membrane

A
  1. keep damaging materials out of the cell
  2. allow entry of materials needed by the cell
  3. facilitate chemical reactions necessary for life
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3
Q

lipid

A

carbon-containing compounds found in organisms

-non polar and hydrophobic

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4
Q

hydrocarbons

A

non-polar molecules that contain only carbon and hydrogen

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5
Q

why do lipids not dissolve in water?

A

they contain a major hydrocarbon component called a fatty acid

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6
Q

fatty acid

A

a hydrocarbon chain bonded to carboxyl (-COOH) functional group

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7
Q

what are the two building blocks of lipids?

A

fatty acid

isoprene

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8
Q

saturated hydrocarbon chains

A

hydrocarbon chains that consist of only single bonds between the carbons

  • have more chemical energy than unsaturated fats
  • can be closely packed (no kinks)
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9
Q

unsaturated hydrocarbon chains

A

hydrocarbon chains with one or more double bonds between the carbons

  • cause “kinks”/prevents close packing of tails
  • reduces hydrophobic interactions
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10
Q

which is healthier, unsaturated or saturated fats?

A

food that contain lipids with polyunsaturated fats are said to be healthier than foods with saturated fats

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11
Q

what are the 3 most important types of lipids found in cells?

A
  • fats
  • steroids
  • phospholipids
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12
Q

fats

A

composed of 3 fatty acids linked to 3-carbon glycerol
(aka triacylglycerols/triglycerides)
-primary use is energy storage

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13
Q

oils

A

occur when fatty acids are polyunsaturated

-liquid triacylglycerols

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14
Q

ester linkage

A

join glycerol and fatty acids

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15
Q

steroids

A

family of lipids with distinctive four-ring structures

-differ from steroid to steroid depending on the side groups attached to the hydrophobic rings

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16
Q

cholesterol

A

-important type of steroid in mammals

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17
Q

phospholipids

A

consist of a glycerol linked to:

  1. phosphate group (PO42-)
  2. two hydrocarbon chains of isoprene OR fatty acids
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18
Q

where are phospholipids composed of fatty acids found? what organisms?

A

domains bacteria and eukarya

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19
Q

where are phospholipids composed of isoprenoid chains found? what organisms?

A

domain archaea

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20
Q

functions of lipids

A
  1. store chemical energy
  2. signals between cells
  3. capture/respond to sunlight
  4. waterproof coating on leaves
  5. act as vitamins in cellular processes
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21
Q

can all lipids form membranes? why or why not?

A

no. membrane forming lipids must contain a polar hydrophilic region AND a non polar hydrophobic region

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22
Q

what are the two parts of phospholipid (membrane forming)?

A

head = interact with water (face outward)
tail = do not interact with water (face inward)
** allows these lipids to form membranes

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23
Q

what is the head region comprised of?

A

-glycerol
-phosphate
-charged group
(highly polar covalent bonds/reactive in water)

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24
Q

what is the tail region comprised of?

A

-two non-polar fatty acids or isoprene chains

hydrophobic/non polar

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25
Q

upon contact with water, phospholipids form either ___ or ____?

A

micelles

phospholipid bilayers

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26
Q

micelles

A

head face the water, tails face each other (forms a ring)

  • tiny droplets
  • tend to form fatty acids/simple amphipathic hydrocarbon chains
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27
Q

phospholipid bilayers

A

(lipid bilayers)

  • form when two sheets of phospholipid molecules align
  • hydrophilic heads face the solution
  • hydrophobic tails face each other (inward)
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28
Q

does the formation of phospholipid bilayers require energy input?

A

No, they form spontaneously without any outside input of energy
-they are much more stable when organized in micelles or bilayers

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29
Q

why are independent lipids unstable in water?

A

because hydrophobic tails disrupt hydrogen bonds that could otherwise form between water molecules
-as a result, tails of these molecules are forced together
(no energy input required)

30
Q

permeability

A

tendency of a structure to allow a given substance to pass through it

31
Q

describe the selective permeability of phospholipid bilayers

A
  • small/non polar molecules pass quickly

- large/charged molecules pass slowly, if at all

32
Q

what is the permeability of O2,CO2, N2?

A
  • high permeability

- small non-polar molecules

33
Q

what is the permeability of H2O, Glycerol?

A
  • high/medium permeability

- small uncharged polar molecules

34
Q

what is the permeability of glucose/sucrose?

A
  • low permeability

- large uncharged polar molecules

35
Q

what is the permeability of Cl-, K+, Na+?

A

none.

ions, no permeability

36
Q

what are some factors that influence the behavior of the membrane?

A
  1. number of double bonds between carbons in the tail
  2. length of tail
  3. number of cholesterol molecules in membrane
  4. temperature
  5. transmembrane proteins
37
Q

which has greater permeability, lipid bilayer with short unsaturated tails? or long saturated tails?

A

-short unsaturated tails have greater permeability (kinks, shorter tails = more space for substances to pass through)

38
Q

how does temperature affect permeability?

A

decrease temp = molecules move more slowly

-decreased permeability

39
Q

how does cholesterol affect permeability?

A

adding cholesterol increases density of the hydrophobic section
-adding cholesterol decreases membrane permeability

40
Q

how does tail length affect permeability?

A

longer tail = stronger hydrophobic interactions

-longer tail = less permeability

41
Q

what kind of lipids comprise butter?

A

saturated lipids

42
Q

what kind of lipids comprise beeswax?

A

saturated lipids with long hydrocarbon tails

43
Q

what kind of lipids comprise safflower oil?

A

unsaturated lipids

44
Q

how do individual phospholipids move within the bilayer?

A

laterally within the same layer

-they rarely flip to the opposite side of the bilayer

45
Q

passive transport

A

does not require energy input

46
Q

active transport

A

requires input energy to move substances across membrane

47
Q

solutes

A

small ions/molecules in a solution

-they have thermal energy and are in constant motion

48
Q

diffusion

A

random motion of solutes from a high –> low concentration gradient
(no energy required)

49
Q

concentration gradient

A

difference in solute concentrations

50
Q

equilibrium

A

reached once molecules/ions are evenly distributed throughout a solution

51
Q

osmosis

A

the random movement of water across lipid bilayers

-water moves from low solute concentration –> high solute concentration (dilutes the higher concentration)

52
Q

hypertonic

A

water leaves cell (higher concentration outside cell) shrinkage

53
Q

hypotonic

A

water enters cell (higher concentration inside cell) swelling

54
Q

isotonic

A

even distribution of solute

55
Q

fluid-mosaic model

A

a model of membrane structure that suggests some proteins are inserted into the lipid bilayer
-this makes the membrane a dynamic combination of lipids and proteins

56
Q

integral proteins

A

amphipathic proteins that are inserted throughout the membrane
-segments are within the membrane

  • polar part of protein align with the phospholipid head
  • non polar align within the bilayer alongside the tails
57
Q

transmembrane proteins

A

a type integral protein that spans the membrane

-involved with transporting selected ions/molecules across membrane

58
Q

peripheral proteins

A

only found on one side of the membrane

-often attached to integral proteins

59
Q

transport proteins (name 3 types)

A

transmembrane proteins that transport molecules

  1. channels (always passive)
  2. carrier proteins/transporters (always passive)
  3. pumps (active)
60
Q

ion channels

A

specialized membrane proteins

  • form pores/openings in the cell membrane
  • ions move through these pores from high –> low concentration
  • also move from like charge –> unlike charge

(concentration gradient and electrochemical gradient)

61
Q

electrochemical gradient

A

areas of like charge/unlike charge (comparable to concentration gradient)

62
Q

why are ion channels so important?

A

they allow otherwise impermeable ions to pass through the plasma membrane
(facilitated diffusion)

63
Q

how are channels proteins selective?

A

they only allow certain molecules/ions to pass through each type of channel protein (ex. ion channels only allow certain ions)

64
Q

facilitated diffusion

A

-the passive transport of substances that would not otherwise cross the membrane

65
Q

aquaporins

A

“water pores”

  • allow water to cross the membrane over 10x faster than it would naturally
  • hydrophilic interior/hydrophobic exterior
66
Q

gated channels

A

a characteristic of channels in which the channels operate by opening/closing with certain signaling
(binding of specific molecule/change in electrical voltage)

67
Q

carrier protein (transporters)

A

channels that change shape during the transport process

68
Q

pumps

A

membrane proteins that require active transport of molecules (move against concentration/electrochemical gradient)
-requires ATP

69
Q

secondary active transport (cotransport)

A

-occurs when the electrochemical gradient (caused by pumps) provides enough potential energy to power the movement of a different molecule against its particular gradient

70
Q

3 mechanisms of membrane transport

A
  1. diffusion (passive)
  2. facilitated diffusion (passive)
  3. active transport (requires ATP)

Biology 1107 Exam 1 (6 decks)

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