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AP Biology (Bob) > Mebrane Transport and Cell Signaling (Chapter 5) > Flashcards

Mebrane Transport and Cell Signaling (Chapter 5) Flashcards

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1
Q

ingredients of membranes

A

lipids and proteins

phospholipids are most abundant

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2
Q

amphipathic

A

quality of having both hyrdophilic and hydrophobic regions

membrane phospholipidss and proteins are amphipathic

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3
Q

fluid mosaic model

A

membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids

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4
Q

sensitivitivity of membranes to temperature

A

at lower temperatures phospholipids become closely packed

phospholipids with unsaturated hyrdocarbon tails stay fluid

kinks in the tail where double bonds are located keep them from being closely packed

cholesterol wedged between phospholipids changes fluidity at different temperatures:

high temperatures cause membrane to be less fluid

lowers the temperature at which membrane will solidify

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5
Q

reason for variations in lipid composition

A

maintains fluidity in extreme environments

fishes in cold water have lots of unsaturated hyrdocarbon

bacteria in geysers have unusual lipids that prevent fluidity

lipid composition can change over time (e.g. winter wheat)

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6
Q

integral proteins

A

penetrate the hyrdophopic interior of the lipid bilayer

most are transmembrane proteins and span the membrane

hydrophobic region consisting of non-polar amino acids

some have hydrophilic channels allowing passage

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7
Q

peripheral proteins

A

not embedded in lipid billayer

appendages are loosely bound to the surface of the membrane

some are held in place by the cytoskeleton

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8
Q

functions of proteins in plasma membrane

A

transport: hydrophilic channel across the membrane

enzymatic activity: active site exposed to adjacent solution

attachment to cytoskeleton and extracellular matric: microfilaments non-covalently bound

cell-cell recognition: allow recognition by membrane proteins on other side of membrane

intercellular joining: hook together various kinds of junctions

signal transduction: one side of protein receieves message from hormone and transmits by changing shape on other side

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9
Q

role of carbohydrates in cell-cell recognition

A

cells recognize other cells by binding molecules

membrane carbohydrates are commonly the bound molecule

short (<15) chains of sugar units

glycolipids: carbohydrates covalently bonded to lipid
glycoprotein: carbohydrate covalently bonded to protein

great variation in membrane carbohydrates: species to species and among cell types

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10
Q

selective permeability

A

nonpolar molecules (hydrocarbons, carbon dioxide, oxygen) are hydrophobic, can dissolve in lipid bilayer, and can cross it easily without membrane protein

polar molecules and ions (glucose, sugars) are hydrophilic and cnanot pass from the inside of the hydrophobic membrane

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11
Q

transport proteins

A

span lipid bilayer and allow passage of polar molecules and ions

specific to the substance it translocates

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12
Q

channel proteins

A

hyrdophilic channel that molecules use as a tunnel

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13
Q

aquaporins

A

type of channel protein

allows passage of water through the plasma membrane

consists of four identical subunits

polypeptide forms channel for single file passage

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14
Q

carrier proteins

A

hold onto passengers and change shape to shuttle across

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15
Q

diffusion

A

movement of particles as a result of constant motion due to thermal energy

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16
Q

rule of diffusion

A

substance will diffuse to be less concentrated

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17
Q

concentration gradient

A

region along which concentration increases or decreases

substances diffuse down their concentration gradient

no work must be done; diffusion is spontaneous

each substance diffuses down its own gradient unaffected by other substances

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18
Q

passive transport

A

diffusion of substance across a biological membrane

cell does not expend energy to make it happen

concentration gradient represents potential energy

membranes have different effects on rates of diffusion

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19
Q

osmosis

A

diffusion of free water across selectively permeable membrane

tight clustering of water molecules around the hydrophilic solute molecules make some water unavailable

remaining free water diffues across membrane from highest free water concentration to lower

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20
Q

tonicity

A

ability of a solution to cause cell to gain or lose water

factors affecting tonicity:

solute concentration

membrane permeability

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21
Q

isotonic environment

A

results in no net movement of water

water diffuses across the membrane but at same rate

example: seawater is isotonic to many marine invertebrates

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22
Q

hypertonic environment

A

high concentration of non-penetrating solutes in surrounding solution

will case water to leave cell

cell will loose water, shrivel and possibly die

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23
Q

hypotonic environment

A

low concentration of non-penetrating solutes in surrounding solution will cause water to enter cell

cell will gain water, swell, and burst

24
Q

osmoregulation

A

mechanism by which cells in hypotonic and hypertonic environments control water balance

example: contractile vacuole organelle functions as bilge pump

25
Q

turgor pressure

A

cell walls exert back pressure

prevents futher uptake of water

walls help maintain the cell’s water balance

without turgor pressure plant cells become flaccid

26
Q

plasmolysis

A

plant cell in hypertonic enviornment

plant cell loses water to environment and wilts

27
Q

facilitated diffusion

A

transport proteins help diffuse polar molecules and ions

most transport proteins are specific

28
Q

active transport

A

mechanism to pump solute against the concentration gradient

allows cell to maintain internal concentration of small solutes

animal cells have high concentrations of potassium ions (K+)

animal cells have low concentrations of sodium ions (Na-)

plasma membrane pumps Na+ out and K+ inot the cell

ATP supplies the energy for most active transport

29
Q

sodium-potassium pump

A

exchanges Na+ for K+ across the plasma membrane

30
Q

membrane potential

A

voltage across a membrane

voltage is electrical potential energy and comes from seperation of opposite charges

cytoplasmic side is negative in charge relative to extracellular side

ranges from -50 to -200 millivolts (mV)

acts like a battery energy source

31
Q

electrochemical gradient

A

combination of forces acting on an ion

ion diffuses down its electrochemical gradient

important to nerve impulses

32
Q

electrogenic pump

A

transport proteins actively contribute to membrane potential

sodium-potassium pum pumps 3 Na+ out for 2 K+ in

each pup there is net transfer of one positive charge out

33
Q

proton pump

A

main electogenic pump of plants, fungi

actively transports protons out of the cell

transfers positive charge from the cytoplasm to the extracellular

proton gradients useful for:

ATP synthesis during cellular respiration

co-transport

34
Q

cotransport

A

special transport mechanism

single ATP-powered pump transports a specific solute

indrectly drives the active transport of other solutes

substance pumped across a membrane can do work diffusing back

example: proton pump in plants

H+ pumped into cell with proton pump

H+ diffuses out and provides energy to pump sucrose in from photosynthesis

35
Q

exocytosis

A

molecule secretion by fusion of vesicles with membrane

transport vesicle budded from Golgi apparatus moves along microtubules of the cytoskeleton to the plasma membrane

plasma membranes fuse when vesicle membrane and plasma membrane come into contac

contes of vesicle spill to the outside of the cell

vesicle membrane becomes part of the plasma membrane

examples: pancreas cells secrete insulin into extracellular fluid, nerve cells release neutrotransmitters, plant cells build walls by delivering protein

36
Q

endocytosis

A

cell takes in molecules and particulate matter forming new vesicle

events of endocytosis look like reverse of exocytosis

three types:

phagocytosis, pinocytosis, receptor-mediated endocytosis

37
Q

phagocytosis

A

cell engulfs a particle by wrapping speudopodia around it

packages it within a mebranous sac called food vacuole

particle digested after food vacuole fuses with lysosome

lysosome contains hydrolytic enzymes

38
Q

pinocytosis

A

cell continually “gulps” droplets of extracellular fluid

cell otains molecules dissolved in the droplets

any and all substances are taken into the cell

parts of plasma that form vesicles are lined with protein

39
Q

receptor-mediated endocytosis

A

specialized type of pinocytosis that acquires bulk quantities

embedded in plasma membrane are proteins with receptors

after ingested material is liberated from vesicle, emptied receptrs are recycled to plasma membrane by the same vesicle

40
Q

local cell to cell communication types

A

direct contact between eukaryotic cells

cell to cell recognition

paracine signaling: signaling cell secrete messenger molecules

synaptic signaling: electrical signal moving along nerve cell triggers secretion of neurotransmitter molecules

41
Q

paracine signaling

A

requires local regulators

signaling cell secretes messenger molecules

growth factors are one class and stimulate cells to grow

42
Q

synaptic signaling

A

occurs in the animal nervous system

electrical signal moving along nerve cell

triggers secretion of neurotransmitter molecules

molecules diffuse across the synapse

43
Q

endocrine or hormonal signaling

A

type of long distance cell to cell communication

specialized cells secrete hormones which travel via blood

target cells can recognize and react to the hormone

44
Q

Earl W. Sutherland

A

made discovers about cell signaling

45
Q

stages at receiving end of cell to cell communication

A

reception

transduction

response

46
Q

receptor protein

A

detects the signal on or in the target cell

47
Q

signaling molecule

A

provides signal to receptor protein

complementary in shape

behaves as a ligand (type of molecule that specifically binds to another molecule)

ligand binding causes receptor protein to undergo change

48
Q

ligand

A

signaling molecule that specifically binds to another molecule

49
Q

G protein-coupled receptors (GPCR)

A

cell surface transmembrane receptor

works with the help of a G protein

binds the energy rich molecule GTP

GPCR pathways are extremely diverse in their functions: embryonic development, senses of smell and taste, involved in many diseases

50
Q

ligand-gated ion channels

A

membrane receptor that has a region that can act as a gate

signaling molecule binds as a ligand to the receptor protein

gate opens and closes allowing or blocking diffusion

very important in nervous system

51
Q

intracellular receptors

A

found in either the cytoplasm or nucleus of target cells

chemcial messenger passes through the target cells membrane

messenger binds to receptor protein

protein then enters nucleus

52
Q

signal transduction pathway

A

multistep pathway

binding of specific signaling molecule to receptor in membrane

triggers first step in the chain of interactions

activates another molecule which activates another molecule

53
Q

protein kinase

A

enzyme that transfers phosphate groups from ATP to a protein

widely involved in signaling pathways

signal is transmitted by casade of protein phosphorylations

54
Q

protein phosphatases

A

enzyme that can rapidly remove phosphate groups from protein

process is called phophorylation

provides mechanism for turning off transduction pathway

make the protein kinase available for reuse

55
Q

second messengers

A

small, non-protein, water-soluable molecules

involved in transduction

can rapidly spread by diffusion because they are small

56
Q

cyclid AMP (cAMP)

A

second messenger important to many biological processes

binding of epinehrine to a specific receptor protein leads to activation of adenylyl cyclase, an enzyme embedded in the plasma membrane that converts ATP to cAMP

cAMP activates protein kinase A

57
Q

Response

A

occur in nucleus or cytoplasm

can include:

protein synthesis

activity of protein

AP Biology (Bob) (3 decks)

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