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AP Bio > closer look @ cell membrane > Flashcards

closer look @ cell membrane 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
Functions of proteins:
Transport, Enzymatic, Receptor, Adhesion, Recognition, Attachment to the cytoskeleton and ECM (mnemonic is TERARA; not necessary to know)
26
Transport proteins
can serve as a | channel for particular solutes
27
Enzymatic activity-
protein built in can be an enzyme
28
Receptor protein-
Signal transduction- can have binding sites | for chemical messengers
29
Adhesion proteins
Intercellular joining- proteins of adjacent | cells can be joined together as a junction
30
Recognition proteins-
Cell-cell recognition- some glycoproteins (proteins with carb chains) serve as identification tags
31
Attachment to the cytoskeleton and ECM
microfilaments can | be bonded to membrane proteins- helps cell shape
32
ECM
extracellular matrix (stuff outside cell)
33
Why is it important for cell to be able to distinguish one type of cell from another?
Sorting of cells into tissues and basis of rejection of foreign cells
34
oligosaccharides
dozen sugars
35
Recognition based on surface molecules (carbs) on plasma membrane
Usually branched oligosaccharides (short polysac) with fewer than 15 units. Some- bonded to lipids, forming glycolipids, most are bonded to proteins- glycoproteins
36
What does diversity of oligosaccharides allow?
them to function as markers to distinguish one cell from another
37
Permeability of Lipid Bilayer
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
Diffusion
tendency for molecules of any substance to spread from an area of high concentration to low concentration
39
down conc gradient
(from more conc to less conc)
40
Concentration gradient
difference in the number of ions or molecules of a substance between two adjoining regions
41
dynamic equilibrium
equal rate of movement between the two sides
42
Any substance will spontaneously diffuse down its concentration gradient until...
dynamic equilibrium is reached. Occurs across cell membrane- ex- oxygen crosses cell membrane for use in cell respiration
43
Passive transport
the movement of molecules from a high | concentration to a low concentration w/o the use of energy
44
Factors that determine diffusion rate:
Gradient steepness, Molecular size, temp, Electric gradient (sometimes), pressure gradient (sometimes)
45
Gradient steepness (diffusion factors)
faster when gradient is steeper
46
Molecular size (diffusion factors)
smaller molecules flow down concentration | gradient faster than large ones
47
temp (diffusion factors)
more heat energy causes molecules to move faster, therefore diffusion is more rapid
48
Electric gradient (diffusion factors)
difference in electric charge between two regions. Opposite charges attract, so a more negative region will attract positive ions
49
pressure gradient (diffusion factors)
difference in the pressure between two | regions. Depending on where the pressure is, diffusion will be affected
50
Osmosis-
movement of water from a higher concentration to a | lower concentration across a semipermeable membrane
51
Tonicity
relative solute concentrations of two fluids
52
Hypertonic
solution with | higher conc of solutes
53
hypotonic
solution with | lower conc of solutes
54
Isotonic
2 solutions of equal solute conc
55
diffusion in tonicity terms
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
lyse--
burst
57
What happens if cell w/o walls is in solution that is hypertonic to the cell?
it'll lose water, shrivel, prob die
58
Hydrostatic pressure
pressure that a volume of | fluid exerts against a wall or membrane
59
What happens if a cell w/o walls is placed in hypotonic solution?
water will enter and cell will | swell. Hydrostatic pressure will increase , and an animal cell will lyse
60
osmoregulation-
control of water balance
61
What kind of solution do cells wo walls need to live?
To live, cells must live in isotonic solutions, or have special adaptations for osmoregulation
62
Paramecium
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
turgid
firm and healthy
64
what happens if a cell w walls is in hypotonic solution?
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
osmotic (turgor) pressure
the fluid pressure | that builds up
66
Osmotic pressure
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
what happens if a cell w walls is in an isotonic environment?
cells become flaccid--limp and the plant wilts
68
plasmolysis
plasma membrane pulls away from cell wall
69
what happens if a cell w walls is in an hypertonic environment?
cell will lose water and shrink. Plasmolysis occurs and cell dies
70
Facilitated diffusion-
transport proteins in membrane help | larger + hydrophilic substances diffuse thru
71
proteins used for facilitated diffusion- (+ characteristics)
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
mechanisms facilitated diffusion
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
- Active transport
any type of movement that requires energy
74
2 categories- Active transport
Performed by proteins in cell membrane, using ATP, or Exocytosis and Endocytosis
75
sodium-potassium pump-
(ex of C1 of Active transport) cotransporter--transports three sodium ions outside the cell and brings in 2 potassium ions into the cell
76
exocytosis
cell secretes macromolecules by fusion of vesicles with plasma membrane-contents of vesicle then spill to the outside of the cell
77
vesicle
transporters
78
purpose + ex of exocytosis
Used by secretory cells to export products Ex- Insulin from pancreas, chemical signals from nerve cells
79
Endocytosis
cell takes in macromolecules by forming | new vesicles from the plasma membrane
80
Phagocytosis-
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
Pinocytosis
unspecified “gulping” of extracellular fluid and solutes into tiny vesicles
82
Receptor-mediated endocytosis-
proteins with specific receptor sites bind extracellular substances called ligands. Receptor proteins are clustered in regions on membrane called clathrin coated pits
83
Purpose of Receptor-mediated endocytosis-
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
water potential
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
equation water potential
solute potential + Pressure potential = Water potential 
86
equation solute potential
solute potential-iCRT | i=ionization constant/how many ions that solute forms in water
87
bigger SA:V ratio for a cell means...
more efficient in removing waste by diffusion
88
SA of rectangular solid
2(wl+hl+hw)

AP Bio (35 decks)

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