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AEBI 122 > Chapter 7 > Flashcards

Chapter 7 Flashcards

1
Q

what is the plasma membrane?

A

it is the boundary that separates the living cell from its surroundings (8mm)
- it is selectively permeable

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2
Q

what is selective permeability?

A

allowing some substances to cross it more easily than others

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3
Q

what lipid is the most abundant in the plasma membrane?

A

the phospholipids are the most abundant lipid in the plasma membrane

  • phospholipids are also amphipathic molecules
  • phospholipids can move within the bilayer
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4
Q

what are amphipathic molecules?

A

molecules that contain a hydrophobic and a hydrophilic region(s)

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5
Q

what is the fluid mosaic model?

A

it states that the membrane is a fluid structure with a “mosaic” of various proteins embedded in it or attached.

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6
Q

hydrophobic interactions are what?

A

they are weaker than covalent bonds

and membranes are held together by these types of bonds

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7
Q

what rarely happens across a membrane?

A

rarely does a molecule flip-flop transversely across the membrane

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8
Q

How are the membrane of a cell and temperature related?

A
  • As temperatures cool, membranes switch from a fluid state to a solid state
  • the temperature at which a membrane solidifies depends on the type of lipids
  • membranes must be fluid to work properly
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9
Q

membranes rich in…?

A

membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids

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10
Q

At warm temperatures of about 37 degrees celsius?

A

cholesterol restricts the movement of phospholipids

- at cool temperatures it maintains fluidity by preventing tight packing

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11
Q

proteins do what?

A
  • proteins determine most of the membranes specific functions
  • proteins can be peripheral( attached outside the membrane) or integral (within the membrane)
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12
Q

what are peripheral proteins?

A

they are like appendages bound loosely to the surface of the membrane

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13
Q

what are integral proteins?

A

they penetrate the hydrophobic core

- integral proteins that span the membrane are called TRANSMEMBRANE PROTEINS

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14
Q

Integral proteins contain how many regions?

A

2 regions
hydrophobic region: consists of one or more stretches of nonpolar amino acids, often coiled into alpha helices
hydrophilic region: is in contact with the aqueous solution

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15
Q

what are the 6 major functions of membrane proteins?

A
  1. transport
  2. enzymatic activity
  3. signal transduction
  4. cell - cell recognition
  5. intercellular joining
  6. attachement to the cytoskeleton and extracellular matrix (ECM)
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16
Q

what is the role of carbohydrates in cell- cell recognition?

A
  • cells recognize each other by binding to surface molecules, often carbohydrates (there are 15 sugars), on the plasma membrane
  • Carbohydrates act as makers to distinguish one cell from another
  • Membrane carbohydrates maybe covalently bonded to lipids (glycolipids) or more commonly proteins (glycoproteins)
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17
Q

The asymmetrical distribution of lipids, proteins and carbohydrates in the membrane is determined when?

A

This is determined when the membrane is built by the golgi apparatus and the ER

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18
Q

what is the Asymmetry of membrane lipids?

A
  • Inner and outer membrane leaflets have different lipid compositions
  • Provides different physicochemical properties appropriate for different interactions
  • membrane lipids move easily within a leaflet but only rarely flip-flop
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19
Q

Hydrophobic (non-polar) molecules can?

A

can dissolve in the phospholipid bilayer and pass through the membrane rapidly
(hydrocarbons, oxygen, and carbon dioxide)

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20
Q

Hydrophilic (polar) molecules?

A

do not cross the membrane as easily (sugars, ions and water)

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21
Q

what are transport proteins?

A

allow passage of of hydrophilic substances across the membrane without coming in touch with the hydrophobic part

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22
Q

what are channel proteins?

A

A type of transport protein that has a hydrophilic that certain ions or molecules can use as a tunnel

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23
Q

what is an aquaproin?

A

a channel protein that facilitate the passage of water

24
Q

what are carrier proteins?

A

bind to molecules and change the shape to shuttle them across the membrane

25
Q

transport proteins are an example of what?

A

active transport, which means they require energy to go through with reactions

26
Q

what is passive transport?

A

is diffusion of a substance across a membrane with no energy investment

27
Q

what is diffusion?

A

is the tendency for molecules to spread out evenly into the available space
- goes from high to low concentration

28
Q

what is a concentration gradient?

A

the difference in concentration of a substance from one area to another
- no work must be done to move substances down their concentration gradient

29
Q

a concentration gradient represents what?

A

potential energy

30
Q

what is osmosis?

A

is the diffusion of water across a selectively permeable membrane
- goes from lower solute concentration to higher solute concentration

31
Q

what is tonicity?

A

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

32
Q

what is an isotonic solution?

A

solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

33
Q

what is a hypertonic solution?

A

solute concentration is greater than that inside the cell, cell loses water

34
Q

what is a hypotonic solution?

A

solute concentration is less than that inside the cell, cell gains water

35
Q

what is facilitated diffusion?

A

transport proteins speed the passive movement of molecules across the plasma membrane
- channel proteins provide corridors that allow a specific molecule or ion to cross the membrane

36
Q

channel proteins include?

A
  • aqauporins for facilitated diffusion of water

- ion channels that open and close in response to a stimulus (Gated Channels)

37
Q

what is active transport?

A

active transport moves ions against their concentration gradients and they require energy to do this
- allows cells to maintain concentration gradients that differ fro their surroundings

38
Q

what is the sodium-potassium pump?

A

is one type of active transport system

  • found in animal cells
  • the pump is an integral membrane glycoprotein ( an antiporter)
  • for every 3 Na+ that goes in 2 K+ go out
39
Q

what is primary active transport?

A

requires direct hydrolysis of ATP

40
Q

what s secondary active transport?

A

energy comes from an ion concentration gradient that is established by primary active transport

41
Q

what is membrane potential?

A

is the voltage difference across a membrane
- all membrane have a potential of -50mV to -200mV because the inside of the cell is more negative than the outside of the cell

42
Q

what is voltage?

A

voltage is created by differences in the distribution of positive and negative ions

43
Q

what is an electrochemical gradient?

A

DRIVE THE DIFFUSION OF IONS ACROSS A MEMBRANE

  • A chemical force (the ion’s concentration gradient)
  • An electrical force ( the effect of the membrane potential on the ion’s movement)
  • Ions will diffuse down the concentration gradient and down the electrochemical gradient
44
Q

what is an electrogenic pump?

A

is a transport protein that generates voltage across a membrane
- the sodium-potassium pump is the major electrogenic pump of animals

45
Q

what is a proton pump?

A

The main electrogenic pump of plants, fungi, and bacteria

46
Q

what is co-transport ?

A

Occurs when active transport of a solute indirectly drives transport of another solute

47
Q

what is the Glucose Transporter?

A

an example of facilitated diffusion

  • the gradient for glucose entry into the cell is maintained by phosphorylation of glucose in the cytoplasm
  • insulin stimulates glucose uptake by causing the insertion into cell membrane vesicles containing preformed glucose transporters
48
Q

what is exocytosis?

A

transport vesicles migrate to the membrane, fuse with it, and release their contents

49
Q

bulk transport across the plasma membrane occurs by?

A

exocytosis and endocytosis

50
Q

what is endocytosis?

A

the cell takes in macromolecules by forming vesicles from the plasma membrane
- there are three types of endocytosis

51
Q

what are the 3 types of endocytosis?

A
  1. phagocytosis ( cellular eating)
  2. pinocytosis ( cellular drinking)
  3. Receptor-mediated endocytosis
52
Q

what is phagocytosis?

A

A cell engulfs a particle in a vacuole, the vacuole fuses with the lysosome to digest the particle

53
Q

what is pinocytosis?

A

molecules are taken up when extracellular fluid is “gulped” into tiny vesicles

54
Q

what is receptor-mediated endocytosis?

A

binding of ligands to receptors triggers vesicle formation

55
Q

what are ligands?

A

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

AEBI 122 (6 decks)

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