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Biology 2 > Lecture 7- Membrane transport > Flashcards

Lecture 7- Membrane transport Flashcards

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1
Q

What is selective permeability?

A

Membranes allow some substances but not others to pass through them

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2
Q

What two types of processes do substances cross biological membranes by?

A

Active transport

Passive transport

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3
Q

What are the two types of passive transport?

A

Simple diffusion

Facilitated diffusion

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4
Q

What is diffusion?

A

The process of random movement towards a state of equilibrium

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5
Q

What is a solution said to be at when there is no net change in distribution?

A

Equilibrium

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6
Q

Define diffusion

A

The net movement from regions of greater concentration to regions of lesser concentration

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7
Q

What 4 factors does the rate of diffusion depend on?

A
  • Diameter of molecules/ions
  • Temperature
  • Electric charge
  • Concentration gradient
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8
Q

How long does it take solutes to diffuse across an organelle?

A

1 milisecond

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9
Q

Over what distances is diffusion less useful?

A

1cm- one hour to diffuse

-Not adequate over the length of the human body

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10
Q

What is a membrane called when it allows solutes across easily?

A

Permeable

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11
Q

Explain an experiment that tests the hypothesis that diffusion leads to a uniform distribution of solutes.

A

Add equal amounts of three dyes to still water in a shallow container
Sample different regions at different times

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12
Q

How do solutes distribute within a solution?

A

By diffusion, uniformly and independently of each other.

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13
Q

What is simple diffusion?

A

Small molecules pass through the phospholipid bilayer membrane

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14
Q

What type of molecule moves by simple diffusion?

A

Hydrophobic, lipid soluble molecules

Also water

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15
Q

What types of molecules do not pass readily though a membrane by simple diffusion?

A

Proteins, amino acids, ions (electrically charged, polar molecules)

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16
Q

Why do polar, charged molecules not pass through a membrane by simple diffusion?

A

Polar substances form polar bonds with water- being surrounded prevents their escape
The interior of the membrane is hydrophobic, hydrophilic substances are excluded

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17
Q

What is osmosis defined as?

A

Water diffuses from regions of higher concentrations to a region of its lower concentration

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18
Q

What does osmosis depend on?

A

Number of solute particles present (not kinds)

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19
Q

What is an isotonic solution?

A

Solutions with equal solute concentrations

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20
Q

What is a hypertonic solution?

A

Solution has higher solute concentration than the other solution with which it is being compared

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21
Q

What is a hypotonic solution?

A

Solution has lower solute concentration than the other solution with which is it being compared

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22
Q

What happens when a red blood cell is placed in a hypotonic solution?

A

It takes up water, swells and then bursts

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23
Q

What happens when a red blood cell is placed in a hypertonic solution?

A

Cells lose water and shrivel

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24
Q

What two processes are facilitated diffusion?

A

Channel proteins

Carrier proteins

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25
Q

What is the structure of a channel protein?

A

A central pore lined with polar amino acids and water, non-polar amino acids outside to keep it embedded in the bilayer

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26
Q

What is the movement of ions into and out of cells important in?

A

Electrical activity of the nervous system

Opening of pores in leaves

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27
Q

What is a channel protein that can be opened or closed called?

A

A gated channel

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28
Q

What are some types of gated channel proteins?

A

Ligand-gated channel

Voltage-gated channel

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29
Q

What two factors does the speed of ions through channel proteins depend on?

A
  • Concentration gradient

- Electrochemical gradient

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30
Q

What is a charge imbalance across a plasma membrane called?

A

A membrane potential

31
Q

What is the Nernst equation?

A

Ek=58log[Ko/Ki]
Where Ek is the membrane potential in milivolts
Ko is concentration of ion outside cell
Ki is concentration of ions inside cell

32
Q

What is the membrane potential of animal cells?

A

-70mV (inside negative with respect to outside)

33
Q

How are ion channels specific?

A

K+ is larger but lets go of its water shell and is attracted to oxygen atoms of the channel protein
Smaller Na+ ions are more distant from the oxygen so are surrounded by more water

34
Q

How does water move through membranes faster than expected?

A

Hydrating ions as they pass through channels

Aquaporins

35
Q

What are aquaporins?

A

Channel proteins that allow water to pass through them

36
Q

Where are aquaporins found?

A 
Plant vacuoles (to maintain turgor pressure)
Mammalian kidney (retain water)
37
Q

What do carrier proteins transport?

A

Polar substances such as amino acids and sugars

38
Q

What carrier protein transports glucose?

A

The glucose transporter

39
Q

What does the glucose transporter do?

A

Facilitate glucose uptake into the cell

40
Q

How is simple diffusion similar to carrier protein transport?

A

The rate of both depends on concentration gradient across the membrane

41
Q

How is simple diffusion and carrier protein transport different?

A

Carrier-mediated transport, a point is reached at which increasing concentration does not increase rate of diffusion- saturation

42
Q

Why is there a saturation point for carrier-mediated transport?

A

The limited number of carrier proteins are fully loaded with solute molecules

43
Q

What is active transport?

A

The movement of a substance across a biological membrane against a concentration gradient, requiring expenditure of chemical energy

44
Q

What are the three types of membrane protein involved in active transport?

A

Uniports
Symports
Antiports

45
Q

What do uniports do?

A

Move a single substance in one direction

46
Q

Give an example of a uniport?

A

Calcium-binding protein in plasma membrane and endoplasmic reticulum actively transport Ca2+ outside the cell or inside the ER

47
Q

What do symports do?

A

Move two substances in the same direction

48
Q

Give an example of a symport.

A

Uptake of amino acids from the intestine by cells that line it requires simultaneous binding of Na+ and amino acid

49
Q

What do antiports do?

A

Move two substances in opposite directions

50
Q

Give an example of an antiport.

A

Sodium-potassium pump moves 3 molecules of Na+ out and 2 molecules K+ in

51
Q

What are symports and antiports known as?

A

Coupled transporters

Because they move two substances at once

52
Q

What are the two types of active transport?

A

Primary active transport

Secondary active transport

53
Q

What is primary active transport?

A

Requires direct participation of energy rich ATP

54
Q

What is secondary active transport?

A

Does not use ATP directly

Energy is supplied by an ion concentration gradient established by primary active transport

55
Q

What does secondary active transport aid in?

A

Uptake of amino acids and sugars

56
Q

Why cant macromolecules such as proteins, polysaccharides and nucleic acids pass through membranes?

A

They are too large, too charged and/or polar

57
Q

How do large macromolecules pass biological membranes?

A

Endocytosis

Exocytosis

58
Q

What is endocytosis?

A

Process by which mall molecules, macromolecules, large particles and even small cells are brought into the eukaryotic cell

59
Q

What are the three types of endocytosis?

A

Phagocytosis
Pinocytosis
Receptor-mediated endocytosis

60
Q

What is phagocytosis?

A

Plasma membrane engulfs large particles or entire cells

61
Q

Where is phagocytosis used?

A

Unicellular protists as cellular feeding
White blood cells to defend body
Food vacuole or phagosome fuses with lysosome for digestion

62
Q

What is pinocytosis?

A

Small vesicles bring small, dissolved substances or fluids into the cell

63
Q

Where does pinocytosis occur?

A

Endothelium- the single layer of cells separating tiny blood capillaries from surrounding tissue for cells to acquire fluids from the blood

64
Q

What is receptor-mediated endocytosis?

A

Specific reactions at the cell surface trigger the uptake of specific materials

65
Q

What does receptor-mediated endocytosis depend on?

A

Receptor-proteins

66
Q

What is the first step in receptor-mediated endocytosis?

A

Receptor proteins on the extracellular surface bind with specific substances. These sites are called coated pits

67
Q

What is the cytoplasmic surfaces behind a coated pit coated in?

A

Other proteins such as clathrin

68
Q

What happens once a receptor binds to a specific ligand?

A

Coated pit invaginates and forms a coated vesicle

69
Q

What does clathrin do?

A

Strengthen and stabilize the coated vesicle

70
Q

What happens to a coated vesicle once inside the cell?

A

The clathrin is lost
May fuse with lysosome
Engulfed material is processed and released into the cytosome

71
Q

How is cholesterol taken up by mammalian cells?

A

Receptor-mediated endocytosis

72
Q

Where are LDL’s taken up?

A

The liver for recycling

73
Q

What is exocytosis?

A

The process by which materials packaged in vesicles fuses with the plasma membranes and materials are moved out of the cell

74
Q

Where is exocytosis important?

A

Secretion of indigestible materials to the environment

Secretion of substances, including digestive enzymes, neurotransmitters, materials for plant cell wall construction

Biology 2 (14 decks)

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