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AP Bio > closer look @ cell membrane > Flashcards

closer look @ cell membrane Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

plasma membrane

A

cell membrane

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2
Q

selectively permeable

A

allows some substances to cross it more easily than other substances

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3
Q

cell membrane is…

A

selectively permeable

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4
Q

Amphipathic molecule-

A

has hydrophilic and hydrophobic regions

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5
Q

main ingredients of membranes

A

Lipids and proteins

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6
Q

Phospholipid

A

most abundant lipid in the world, component of cell membrane, amphipathic, Must be two layers (bilayer)-

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7
Q

why must Phospholipid be bilayer?

A

Hydrophobic tails of phospholipids are sheltered from aqueous surrounding, while hydrophilic heads are
exposed

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8
Q

phospholipid structure

A

fatty acids=hydrophobic tails of phospholipids, head has glycerol and phosphate group, is charged and therefore hydrophilic

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9
Q

Proteins in cell membrane

A

Also amphipathic. o Proteins are randomly dispersed with only their hydrophilic
regions protruding into the water

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10
Q

cell fractionation

A

broke cell apart to examine new model like toothpicks stuck throughout)

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11
Q

Membrane structure

A

fluid mosaic model

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12
Q

fluid mosaic model

A

found that there were globular
proteins with both hydrophobic and hydrophilic regions-
extended throughout membrane. . Supported by freeze-fracture technique, which splits membrane
down the middle- shows interior part of bilayer appearing
cobble-stoned

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13
Q

pre f-m model

A

Used to think “sandwich model”- proteins surround lipids. But
in cell fractionation, found that there were many different type
of proteins with different shapes- how could they lie flat on the
surface?

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14
Q

why mosaic (f-m model)

A

consists of glycolipids, phospholipids, proteins and cholesterol

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15
Q

why fluid (f-m model)

A

movement between each part

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16
Q

what holds membranes together?

A

weak hydrophobic interactions

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17
Q

Membranes must be ___ in order to function and _____ & _____ can drift randomly in the plane of the membrane

A

fluid, Lipids and proteins

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18
Q

rate of movement of lipids and proteins

A

Phospholipids can move rapidly
o Proteins move slowly- much larger, some seem to be
immobile

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19
Q

experiment that fused membrane of mouse with membrane

of human cell

A

proved that proteins were evenly distributed throughout; used fluorescent dye to label the proteins from mouse and a different ones for humans–if they were dispersed throughout, so they were liquid

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20
Q

what stabilizes membrane in animals? explain.

A

steroid cholesterol. integrated
between phospholipids, keeps them from
shifting too much and from solidifying at low temperatures

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21
Q

Two major groups of proteins

f-m model

A

Integral + peripheral

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22
Q

transmembrane

A

spans entire membrane

not all are all the way but to some extent

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23
Q

Integral proteins

A

Transmembrane proteins, with hydrophobic regions spanning the hydrophobic interior of the membrane and hydrophilic regions sticking out

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24
Q

Peripheral proteins

A

Not embedded- loosely bound to the surface of the membrane

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25
Q

Functions of proteins:

A

Transport, Enzymatic, Receptor, Adhesion, Recognition, Attachment to the cytoskeleton and ECM
(mnemonic is TERARA; not necessary to know)

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26
Q

Transport proteins

A

can serve as a

channel for particular solutes

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27
Q

Enzymatic activity-

A

protein built in can be an enzyme

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28
Q

Receptor protein-

A

Signal transduction- can have binding sites

for chemical messengers

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29
Q

Adhesion proteins

A

Intercellular joining- proteins of adjacent

cells can be joined together as a junction

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30
Q

Recognition proteins-

A

Cell-cell recognition- some glycoproteins (proteins with carb chains) serve as identification tags

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31
Q

Attachment to the cytoskeleton and ECM

A

microfilaments can

be bonded to membrane proteins- helps cell shape

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32
Q

ECM

A

extracellular matrix (stuff outside cell)

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33
Q

Why is it important for cell to be able to distinguish one type of cell from
another?

A

Sorting of cells into tissues and basis of rejection of foreign cells

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34
Q

oligosaccharides

A

dozen sugars

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35
Q

Recognition based on surface molecules (carbs) on plasma membrane

A

Usually branched oligosaccharides (short polysac) with fewer
than 15 units. Some- bonded to lipids, forming glycolipids, most are bonded
to proteins- glycoproteins

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36
Q

What does diversity of oligosaccharides allow?

A

them to function as markers to distinguish one cell from another

37
Q

Permeability of Lipid Bilayer

A

Hydrophilic molecules such as polar molecules, charged molecules cannot pass through the hydrophobic center, but hydrophobic molecules can pass through, such as hydrocarbons,
carbon dioxide, oxygen.

38
Q

Diffusion

A

tendency for molecules of any substance to spread from an area of high concentration to low concentration

39
Q

down conc gradient

A

(from more conc to less conc)

40
Q

Concentration gradient

A

difference in the number of ions or
molecules of a substance between
two adjoining regions

41
Q

dynamic equilibrium

A

equal rate of movement between the two sides

42
Q

Any substance will spontaneously diffuse down its concentration gradient until…

A

dynamic equilibrium
is reached. Occurs across cell membrane- ex- oxygen crosses cell membrane for
use in cell respiration

43
Q

Passive transport

A

the movement of molecules from a high

concentration to a low concentration w/o the use of energy

44
Q

Factors that determine diffusion rate:

A

Gradient steepness, Molecular size, temp, Electric gradient (sometimes), pressure gradient (sometimes)

45
Q

Gradient steepness (diffusion factors)

A

faster when gradient is steeper

46
Q

Molecular size (diffusion factors)

A

smaller molecules flow down concentration

gradient faster than large ones

47
Q

temp (diffusion factors)

A

more heat energy causes molecules to move faster, therefore diffusion is more rapid

48
Q

Electric gradient (diffusion factors)

A

difference in electric charge between two
regions. Opposite charges attract, so a
more negative region will attract positive ions

49
Q

pressure gradient (diffusion factors)

A

difference in the pressure between two

regions. Depending on where the pressure is, diffusion will be affected

50
Q

Osmosis-

A

movement of water from a higher concentration to a

lower concentration across a semipermeable membrane

51
Q

Tonicity

A

relative solute concentrations of two fluids

52
Q

Hypertonic

A

solution with

higher conc of solutes

53
Q

hypotonic

A

solution with

lower conc of solutes

54
Q

Isotonic

A

2 solutions of equal solute conc

55
Q

diffusion in tonicity terms

A

Water will diffuse across a membrane from a hypotonic solution (greater water concentration) to the hypertonic area. If two solutions are isotonic, water moves across at an equal rate-no net movement. (equilibrium.)

56
Q

lyse–

A

burst

57
Q

What happens if cell w/o walls is in solution that is hypertonic to the cell?

A

it’ll lose water, shrivel, prob die

58
Q

Hydrostatic pressure

A

pressure that a volume of

fluid exerts against a wall or membrane

59
Q

What happens if a cell w/o walls is placed in hypotonic solution?

A

water will enter and cell will

swell. Hydrostatic pressure will increase , and an animal cell will lyse

60
Q

osmoregulation-

A

control of water balance

61
Q

What kind of solution do cells wo walls need to live?

A

To live, cells must live in isotonic solutions, or have special adaptations for osmoregulation

62
Q

Paramecium

A

cell membrane that’s not as permeable to water. lives in freshwater–hypotonic (if it didn’t have osmoregulation, they’d die)
Contractile vacuole that pushes out water

63
Q

turgid

A

firm and healthy

64
Q

what happens if a cell w walls is in hypotonic solution?

A

water flows in but cell wall expands only so
much before it exerts back pressure- opposes further water uptake. Cell is turgid. At some point, osmotic (turgor) pressure will
prevent more water from entering.

65
Q

osmotic (turgor) pressure

A

the fluid pressure

that builds up

66
Q

Osmotic pressure

A

pressure that must be exerted on the side of
the membrane containing higher solute concentration to prevent
the diffusion of water from the
side containing a lower solute conc

67
Q

what happens if a cell w walls is in an isotonic environment?

A

cells become flaccid–limp and the plant wilts

68
Q

plasmolysis

A

plasma membrane pulls away from cell wall

69
Q

what happens if a cell w walls is in an hypertonic environment?

A

cell will lose water and shrink. Plasmolysis occurs and cell dies

70
Q

Facilitated diffusion-

A

transport proteins in membrane help

larger + hydrophilic substances diffuse thru

71
Q

proteins used for facilitated diffusion- (+ characteristics)

A

Transport proteins, (like enzymes):
Specialized for each solute o Can be saturated (used up) o Can be inhibited by molecules that resemble normal solute o Unlike enzymes- catalyze a physical process

72
Q

mechanisms facilitated diffusion

A

Transport protein can undergo change in shape that brings the solute from one side to the other. Transport protein can be a tunnel that allows channel/specific substances to pass thru. Still considered passive because moving down concentration gradient
and it does not require energy.

73
Q
  • Active transport
A

any type of movement that requires energy

74
Q

2 categories- Active transport

A

Performed by proteins in cell membrane, using ATP, or Exocytosis and Endocytosis

75
Q

sodium-potassium pump-

A

(ex of C1 of Active transport) cotransporter–transports three sodium ions outside the cell and brings in 2 potassium ions into the cell

76
Q

exocytosis

A

cell secretes macromolecules by fusion of vesicles with
plasma membrane-contents of vesicle then
spill to the outside of the cell

77
Q

vesicle

A

transporters

78
Q

purpose + ex of exocytosis

A

Used by secretory cells to export products
Ex- Insulin from pancreas, chemical signals from nerve
cells

79
Q

Endocytosis

A

cell takes in macromolecules by forming

new vesicles from the plasma membrane

80
Q

Phagocytosis-

A

Particle of food come near the cell membrane
Cell engulfs particle by wrapping pseudopods around it, forming a vacuole/vesicle
Vacuole then fuses with
a lysosome for digestion

81
Q

Pinocytosis

A

unspecified “gulping” of extracellular fluid and
solutes into
tiny vesicles

82
Q

Receptor-mediated endocytosis-

A

proteins with specific
receptor sites bind extracellular substances called ligands. Receptor proteins are clustered in regions on membrane called
clathrin coated pits

83
Q

Purpose of Receptor-mediated endocytosis-

A

Enables cell to take in bulk quantities of substances- ex- cholesterol from blood (travels as LDL, or low density lipoproteins) binds to receptors on cells in order to enter cells. (If it doesn’t enter the cells, it will build up in arteries and clog them.

84
Q

water potential

A

Water potential is a measure of how likely water is to move from one location (say outside the cell) to another (inside the cell). …water will always move from an area of greater water potential to an area of lesser water potential.

85
Q

equation water potential

A

solute potential + Pressure potential = Water potential

86
Q

equation solute potential

A

solute potential-iCRT

i=ionization constant/how many ions that solute forms in water

87
Q

bigger SA:V ratio for a cell means…

A

more efficient in removing waste by diffusion

88
Q

SA of rectangular solid

A

2(wl+hl+hw)

AP Bio (35 decks)

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