chapter 7- membrane structure and function Flashcards

1
Q

what is an amphipathic molecule and example

A

a molecule that has both a hydrophilic and hydrophobic region
phospholipid

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2
Q

why are membranes considered fluid

A

because the proteins and lipids move laterally through the membrane

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3
Q

what moves and how does it move in a membrane

A

phospholipids and proteins move side to side fast
but they wont flip upside down because it would require going through the hydrophobic/hydrophilic portions (hard to cross)

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4
Q

how does temperature affect the fluidity of the membrane

A

lower temperature = solid membrane
higher temperature = more fluid/liquid

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5
Q

how is the temperature at which a membrane solidifies determined

A

based on the types of lipids in it

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6
Q

why should a membrane be fluid

A

it needs to be to work properly

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7
Q

which membrane it more fluid:
lots of unsaturated fatty acids or lots of saturated fatty acids

A

unsaturated as the kinks in the fatty acids prevent the packing of molecules

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8
Q

what does cholesterol do regarding membranes at different temperatures

A

at warm temperatures it restrains the phospholipid movement (stops membrane from being too fluid)
at cool temperatures it prevents packing (keeps membrane fluid)

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9
Q

what is the reason for the difference in membrane lipid composition (evolution)

A

adaptation to different environmental conditions
(ability to change lipid composition as temperature changes evolved in organisms that live where temperature varies)

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10
Q

what are integral proteins

A

proteins that are imbedded into the membrane (through the hydrophobic middle)

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11
Q

characteristics of integral proteins

A

they have hydrophobic sections made up of nonpolar amino acids/R groups and hydrophilic/polar sections that touch the inside and outside of the cell

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12
Q

what are integral proteins also called

A

transmembrane proteins

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13
Q

what are peripheral proteins

A

proteins that are bound to the surface of the membrane or to integral proteins

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14
Q

what are the six major functions of membrane proteins

A

transport
enzymatic activity
signal transduction
cell-cell recognition
intercellular joining
attachment to cytoskeleton and extracellular matrix

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15
Q

what are the two types of membrane carbohydrates

A

glycolipids (sugar + lipid)
glycoproteins (sugar + protein)

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16
Q

what is the role of membrane carbs in cell recognition

A

cells recognize each other by binding to surface molecules, often carbs and recognizing foreign glyco-lipids/proteins

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17
Q

what builds the membrane

A

the ER and golgi

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18
Q

what does selective permeability mean

A

allows some substances to cross more easily than others

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19
Q

what passes through the membrane and what does not

A

hydrophobic molecules pass through easily while hydrophilic molecules do not or pass through slowly

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20
Q

what facilitates the movement of hydrophilic molecules across the membrane

A

transport

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21
Q

what are the types of transport proteins

A

channel and carrier

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22
Q

what are the types of channel proteins

A

aquaporins
ion channels

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23
Q

how do ion channels work

A

they have a hydrophilic channel that allows polar molecules to pass (ions)

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24
Q

what are gated channels

A

ion channels that open or close in response to a stimulus

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25
how do aquaporins work
channel that allows water to pass through
26
are transport proteins specific
yes they are specific to the substance that they move (and sometimes related substances)
27
what are carrier proteins
proteins that bind molecules and change shape to shuttle them across the membrane
28
what is diffusion
tendency for molecules to spread out evenly into available space
29
how does diffusion work
substances diffuse down their concentration gradient (high concentration to low) spontaneous
30
what kind of transport is diffusion
passive
31
what does passive transport mean
substance moves with no energy being used from the cell
32
what is osmosis
diffusion of water across a selectively permeable membrane
33
how does water diffuse in osmosis
moves from region of lower solute concentration to a region of higher solute concentration until they are equal
34
what is the formula for solute concentration/osmolarity
molarity x number of ionized particles (van hoff i)
35
what is tonicity
ability of a surrounding solution to make a cell gain or lose water
36
what is an isotonic solution
solution's solute concentration is the same as the cell's concentration (no water movement)
37
what is a hypertonic solution
solution's solute concentration is higher than the cell's (water moves out of the cell)
38
what is a hypotonic solution
solution's solute concentration is lower than cell's (water moves in the cell)
39
when an animal cell is placed into isotonic, hypertonic and hypotonic solutions what happens to it
isotonic: normal hypertonic: shrivel hypotonic: swell
40
what is osmoregulation
control of solute concentrations and water balance
41
what is different for plant cells regarding osmosis
they have cell walls which allow them to have better water balance
42
when a plant cell is placed into isotonic, hypertonic and hypotonic solutions what happens to it
isotonic: flaccid (limp) hypertonic: plasmolysis (dead) hypotonic: turgid (firm)
43
what happens during plasmolysis
plant cell loses water, plasma membrane pulls away from cell wall and causes plant to wilt
44
what is facilitated diffusion
transport proteins aid the passive movement of molecules across the membrane
45
what is active transport and characteristics
moving of substances against their concentration gradient, requires energy, performed by specific proteins embedded in membrane
46
what is a type of active transport system
sodium-potassium pump
47
what are the 6 steps of the sodium-potassium pump
1. sodium in the cell binds to the pump 2. binding of sodium stimulates the attachment of a phosphate group to the pump (using atp) 3. the attachment of P group leads to the pump changing shape and releasing the sodium to the outside 4. new shape attracts and binds potassium from the outside which triggers the release of the P group (inside) 5. losing P group restores the original shape 6. potassium is released
48
what is phosphorylation
attachment of a phosphate group to a molecule of ion
49
how much energy does one cycle of the sodium-potassium pump take
one ATP molecule
50
how many sodiums are taken out and potassiums taken in
3 sodiums and 2 potassiums
51
what is membrane potential
voltage difference across a membrane
52
how is voltage created in a membrane
by the differences in the distribution of + and - charged ions across a membrane
53
what is the electrochemical gradient
chemical force (ion's concentration gradient) and electrical force (effect of membrane potential on ion's movement)
54
what does the electrochemical gradient do
diffuses ions across the membrane
55
what is an electrogenic pump and example
a transport protein that generates voltage across a membrane sodium-potassium pump
56
what is the main electrogenic pump for plants fungi and bacteria
proton pump (pumps out H+)
57
what is another function of the electrogenic pump
store energy that can be used for cellular work
58
what is cotransport
when the transport of one solute indirectly drives the transport of other solutes active transport driven by concentration gradient
59
what is bulk transport
large molecules crossing membrane using vesicles
60
does bulk transport require energy
yes
61
what is exocytosis
transport vesicles migrating to the membrane then fusing with it and releasing their contents outside
62
what is endocytosis
cell taking in macromolecules by forming vesicles from the membrane
63
what are the three types of endocytosis
phagocytosis pinocytosis receptor-mediated endocytosis
64
what is phagocytosis
when a cell engulfs a particle into a vacuole vacuole then fuses with lysosome to be digested
65
what is pinocytosis
extracellular fluid in gulped into tiny vesicles
66
what is receptor-mediated endocytosis*
molecule or ion binding to a receptor triggers the formation of a vesicle
67
what do humans use receptor-mediated endocytosis for*
to take in cholesterol using LDL receptors
68
how is cholesterol found in blood*
in particles called low-density lipoproteins (LDL)