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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
upon contact with water, phospholipids form either ___ or ____?
micelles | phospholipid bilayers
26
micelles
head face the water, tails face each other (forms a ring) - tiny droplets - tend to form fatty acids/simple amphipathic hydrocarbon chains
27
phospholipid bilayers
(lipid bilayers) - form when two sheets of phospholipid molecules align - hydrophilic heads face the solution - hydrophobic tails face each other (inward)
28
does the formation of phospholipid bilayers require energy input?
No, they form spontaneously without any outside input of energy -they are much more stable when organized in micelles or bilayers
29
why are independent lipids unstable in water?
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
permeability
tendency of a structure to allow a given substance to pass through it
31
describe the selective permeability of phospholipid bilayers
- small/non polar molecules pass quickly | - large/charged molecules pass slowly, if at all
32
what is the permeability of O2,CO2, N2?
- high permeability | - small non-polar molecules
33
what is the permeability of H2O, Glycerol?
- high/medium permeability | - small uncharged polar molecules
34
what is the permeability of glucose/sucrose?
- low permeability | - large uncharged polar molecules
35
what is the permeability of Cl-, K+, Na+?
none. | ions, no permeability
36
what are some factors that influence the behavior of the membrane?
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
which has greater permeability, lipid bilayer with short unsaturated tails? or long saturated tails?
-short unsaturated tails have greater permeability (kinks, shorter tails = more space for substances to pass through)
38
how does temperature affect permeability?
decrease temp = molecules move more slowly | -decreased permeability
39
how does cholesterol affect permeability?
adding cholesterol increases density of the hydrophobic section -adding cholesterol decreases membrane permeability
40
how does tail length affect permeability?
longer tail = stronger hydrophobic interactions | -longer tail = less permeability
41
what kind of lipids comprise butter?
saturated lipids
42
what kind of lipids comprise beeswax?
saturated lipids with long hydrocarbon tails
43
what kind of lipids comprise safflower oil?
unsaturated lipids
44
how do individual phospholipids move within the bilayer?
laterally within the same layer | -they rarely flip to the opposite side of the bilayer
45
passive transport
does not require energy input
46
active transport
requires input energy to move substances across membrane
47
solutes
small ions/molecules in a solution | -they have thermal energy and are in constant motion
48
diffusion
random motion of solutes from a high --> low concentration gradient (no energy required)
49
concentration gradient
difference in solute concentrations
50
equilibrium
reached once molecules/ions are evenly distributed throughout a solution
51
osmosis
the random movement of water across lipid bilayers | -water moves from low solute concentration --> high solute concentration (dilutes the higher concentration)
52
hypertonic
water leaves cell (higher concentration outside cell) shrinkage
53
hypotonic
water enters cell (higher concentration inside cell) swelling
54
isotonic
even distribution of solute
55
fluid-mosaic model
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
integral proteins
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
transmembrane proteins
a type integral protein that spans the membrane | -involved with transporting selected ions/molecules across membrane
58
peripheral proteins
only found on one side of the membrane | -often attached to integral proteins
59
transport proteins (name 3 types)
transmembrane proteins that transport molecules 1. channels (always passive) 2. carrier proteins/transporters (always passive) 3. pumps (active)
60
ion channels
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
electrochemical gradient
areas of like charge/unlike charge (comparable to concentration gradient)
62
why are ion channels so important?
they allow otherwise impermeable ions to pass through the plasma membrane (facilitated diffusion)
63
how are channels proteins selective?
they only allow certain molecules/ions to pass through each type of channel protein (ex. ion channels only allow certain ions)
64
facilitated diffusion
-the passive transport of substances that would not otherwise cross the membrane
65
aquaporins
"water pores" - allow water to cross the membrane over 10x faster than it would naturally - hydrophilic interior/hydrophobic exterior
66
gated channels
a characteristic of channels in which the channels operate by opening/closing with certain signaling (binding of specific molecule/change in electrical voltage)
67
carrier protein (transporters)
channels that change shape during the transport process
68
pumps
membrane proteins that require active transport of molecules (move against concentration/electrochemical gradient) -requires ATP
69
secondary active transport (cotransport)
-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
3 mechanisms of membrane transport
1. diffusion (passive) 2. facilitated diffusion (passive) 3. active transport (requires ATP)

Biology 1107 Exam 1 (6 decks)

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