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AP Biology > Unit 2 Cell Membranes and Homeostasis > Flashcards

Unit 2 Cell Membranes and Homeostasis Flashcards

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1
Q

selective permeability

A

plasma membranes allow some substances to cross more easily than others

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2
Q

phospholipids

A

the most abundant lipids in most membranes

-amphipathic; have both a hydrophilic and hydrophobic region

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3
Q

fluid mosaic model

A

membrane is a fluid structure with a “mosaic” of various proteins embedded or attached to a double (bilayer) of phospholipids

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4
Q

The Fluidity Membranes

A
  • membrane is held together mainly by weak hydrophobic interactions
  • most lipids and some proteins can shift laterally (this occurs rapidly)
  • some proteins seem to be moved and directed by cytoskeleton while others are held in place
  • membranes must be within a certain range of fluidity to function properly
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5
Q

The Fluidity of Membranes and Temperature

A

membranes solidify at low temperatures

  • membranes with bent, unsaturated tails will remain fluid at lower temperatures because they cannot be backed closely together
  • cholesterol in animal cells resists changes in plasma membrane fluidity caused by change in temperature
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6
Q

integral proteins

A

penetrate the hydrophobic interior of the lipid bilayer

  • hydrophobic part contains stretches of nonpolar amino acids
  • hydrophilic parts are exposed to aqueous solutions
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7
Q

peripheral proteins

A

appendages loosely bound to the surface of a membrane

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8
Q

Functions of Proteins

A
  1. Transport
  2. Enzymatic Activity
  3. Signal transduction
  4. Cell-cell recognition
  5. Intercellular joining
  6. attachment of cytoskeleton and ECM
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9
Q

Proteins and transport

A

may provide hydrophilic channel across membrane or shuttle a substance across by changing shape

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10
Q

proteins and enzymatic activity

A

may be enzyme with active sight exposed to substances in adjacent solution

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11
Q

proteins and signal transduction

A

may have binding sight that fits the shape of a chemical messenger, protein changes shape and relays message

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12
Q

proteins and cell-cell recognition

A

some proteins serve as ID tags that are recognized by membrane proteins of other cells

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13
Q

proteins and intercellular joining

A

membrane proteins of adjacent cells hook together

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14
Q

proteins and attachment of cytoskeleton and ECM

A

elements of both bound to membrane proteins

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15
Q

The Role of Membrane Carbohydrates in cell-cell recognition

A
  • cells recognize other cells by minding to molecules, often containing carbohydrates, on the extracellular surface of the plasma membrane
  • diversity of molecules allow them to serve as markers
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16
Q

glycolipids

A

carbohydrates bonded to lipids

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17
Q

glycoproteins

A

carbohydrates bonded to proteins

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18
Q

The permeability of the lipid bilayer

A
  • nonpolar, hydrophobic molecules can dissolve in the lipid bilayer and easily cross the membrane
  • polar molecules pass through very slowly
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19
Q

transport proteins

A

allow hydrophobic substances to pass through

-types: channel proteins and carrier proteins

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20
Q

channel proteins

A

function by having a hydrophilic channel that certain molecules or ions use as a tunnel through the membrane

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21
Q

aquaporins

A

allows water to pass through plasma membrane rapidly

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22
Q

carrier proteins

A

hold on to passengers and shuttle them across the membrane by changing shape
-specific for the substance it transports

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23
Q

passive transport

A

diffusion of a substance across a membrane with no energy investment

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24
Q

diffusion

A

the movement of molecules of any substance so that they spread out evenly into the available space
-a substance will naturally diffuse from where it is more concentrated to where it is less concentrated

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25
Q

dynamic equilibrium

A

reached when molecules cross a membrane at equal rates in both directions

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26
Q

concentration gradient

A

the region along which the density of a chemical substance increases or decreases

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27
Q

osmosis

A

diffusion of free water molecules across a selectively permeable membrane
-water diffuses from region of lower solute concentration (more water molecules) to the region of higher solute concentration until both concentrations are equal

28
Q

tonicity

A

the ability of a surrounding solution to cause a cell to gain or lose water
-depends in part on concentrations of solutes that cannot cross the membrane

29
Q

isotonic

A

an environment in which water will diffuse across a cell membranes at the same rate in both directions. Volume of animal cell remains stable

30
Q

hypertonic

A

more solute outside of cell; cell will lose water and shrivel

31
Q

hypotonic

A

loss solute outside, cell will swell and burst

32
Q

osmoregulation

A

the control of solute concentrations and water balance

-some organisms have less water permeable membranes or have vacuoles that pump out water

33
Q

turgid

A

health, firm state of a plant cell that occurs when it is in a hypotonic solution

34
Q

flaccid

A

limp plant cells in isotonic solutions

35
Q

plasmolysis

A

in a hypertonic environment, a plant cell lose water, shrivels, and its plasma membrane pulls away from the wall

36
Q

facilitated diffusion

A

many polar molecules and ions diffuse passively with the help of transport proteins that span the membrane

  • channel proteins allow quick diffusion of some hydrophilic substances
  • carrier proteins also carry substances down concentration gradient
37
Q

ion channels

A

channel proteins that transport ions

38
Q

gated channels

A

open or close in response to a stimulus (electric stimulus or binding of substances)

39
Q

active transport

A

uses energy to move solutes against their gradients

  • uses carrier proteins
  • enables a cell to maintain internal concentrations of small solutes that differ from concentrations in the environment
  • ATP can transfer its terminal phosphate group directly to the protein, inducing the protein to change shape
40
Q

sodium-potassium pump

A

exchanges sodium ions for potassium ions across the plasma membrane (using active transport) of animal cells

41
Q

membrane potential

A

the voltage across a membrane

  • typically -50 to -200V
  • the inside of the cell is negative relative to the outside
  • influences traffic, favors passive transport of cations (+) into the cell and anions out of the cell
  • some proteins protons, such as NA-K pump, contribute to membrane potential
42
Q

electrochemical gradient

A

the combination of the chemical gradient and electrical force acting on an ion
-ion diffuses down its electrochemical gradient

43
Q

electrogenic pump

A

a transport protein that generates voltage across a membrane
-help store energy that can be tapped for cellular work

44
Q

proton pump

A

an electrogenic pump that actively transports protons (H+) out of a plant cell

45
Q

contransport

A

a mechanism that occurs when an ATP powered pump that transports a specific solute can indirectly drive the active transport of several other solutes
-couples the diffusion of a previously pumped substance with the transport of a second substance against its gradient.

46
Q

exocytosis

A

transport vesicle from the Golgi moves to the plasma membrane. Proteins rearrange lipids so that the vesicle membrane and plasma membranes fuse. Contents of vesicle are spilled outside the cell
-used by secretory cells to export products

47
Q

endocytosis

A

the cell takes in biological molecules and matter by forming new vesicles from the plasma membrane

48
Q

phagocytosis

A

cell wraps psuedopodia around a particle and packaging it in a food vacuole

49
Q

pinocytosis

A

cell gulps droplets of extracellular fluid into tiny vesicles. Nonspecific in the substance it transports

50
Q

receptor-mediated endocytosis

A

specific substances bind to receptor proteins on the membrane. Proteins cluster in coated pits (which are lined by coat proteins) and form a vesicles. Vesicles is emptied and receptors are recycled to plasma membrane by the same vesicle

51
Q

ligands

A

any molecule that binds specifically to a receptor site on another molecule

52
Q

apoplast

A

in plants, consists of everything external to the plasma membrane of living cells
-includes cell walls, extracellular space, and dead cells

53
Q

symplast

A

consists of the entire mass of cytosol of all living cells in a plant as well as the plasmodes (the cytoplasmic channels that interconnect cells)

54
Q

three routes of transport within a plant tissue or organ

A
  1. Apoplastic route
  2. Symplastic route
  3. transmembrane route
55
Q

apoplastic route

A

water and solutes move along the continuum of cell walls and extracellular space

56
Q

symplastic route

A

water and solutes move among continuum of cytosol,

-substance must pass a plasma membrane once then can move from cell to cell with the plasmodesmata

57
Q

transmembrane route

A

movement out of one cell, across cell wall, and into neighboring cell

58
Q

H+ rather than NA+ plays the primary role in basic transport processes in plant cells

A
  • h+ established membrane potential

- H+ most often contransported in plants, helps with absorption of neutral solutes (like sucrose) and movement of ions

59
Q

water potential

A

predicts the direction in which water will flow. Includes the effects of solute concentration and physical pressure

  • free water moves from higher to lower water potential
  • potential refers to waters capacity to perform work
  • equal 0 when pure water in an open containers is at standard conditions
60
Q

solute potential

A

directly proportional to molarity

-expressed as a negative number as the greater the solutes, the fewer free water molecules and the less water potential

61
Q

water potential equation

A

solute potential+ physical pressure= water potential

62
Q

pressure potential

A

physical pressure on a solution. Can be + or - relative to atmospheric pressure

63
Q

protoplast

A

the living part of the cell, which includes the plasma membrane

64
Q

Long Distance transport

A

diffusion is too slow to function in long-distance transport within a plant
-bulk flow plays large role

65
Q

bulk flow

A

the movement of a liquid in response to pressure gradient

  • moves from higher to lower pressure
  • independent of solute concentration

AP Biology (17 decks)

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