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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
What is the structure of a channel protein?
A central pore lined with polar amino acids and water, non-polar amino acids outside to keep it embedded in the bilayer
26
What is the movement of ions into and out of cells important in?
Electrical activity of the nervous system | Opening of pores in leaves
27
What is a channel protein that can be opened or closed called?
A gated channel
28
What are some types of gated channel proteins?
Ligand-gated channel | Voltage-gated channel
29
What two factors does the speed of ions through channel proteins depend on?
- Concentration gradient | - Electrochemical gradient
30
What is a charge imbalance across a plasma membrane called?
A membrane potential
31
What is the Nernst equation?
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
What is the membrane potential of animal cells?
-70mV (inside negative with respect to outside)
33
How are ion channels specific?
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
How does water move through membranes faster than expected?
Hydrating ions as they pass through channels | Aquaporins
35
What are aquaporins?
Channel proteins that allow water to pass through them
36
Where are aquaporins found?
``` Plant vacuoles (to maintain turgor pressure) Mammalian kidney (retain water) ```
37
What do carrier proteins transport?
Polar substances such as amino acids and sugars
38
What carrier protein transports glucose?
The glucose transporter
39
What does the glucose transporter do?
Facilitate glucose uptake into the cell
40
How is simple diffusion similar to carrier protein transport?
The rate of both depends on concentration gradient across the membrane
41
How is simple diffusion and carrier protein transport different?
Carrier-mediated transport, a point is reached at which increasing concentration does not increase rate of diffusion- saturation
42
Why is there a saturation point for carrier-mediated transport?
The limited number of carrier proteins are fully loaded with solute molecules
43
What is active transport?
The movement of a substance across a biological membrane against a concentration gradient, requiring expenditure of chemical energy
44
What are the three types of membrane protein involved in active transport?
Uniports Symports Antiports
45
What do uniports do?
Move a single substance in one direction
46
Give an example of a uniport?
Calcium-binding protein in plasma membrane and endoplasmic reticulum actively transport Ca2+ outside the cell or inside the ER
47
What do symports do?
Move two substances in the same direction
48
Give an example of a symport.
Uptake of amino acids from the intestine by cells that line it requires simultaneous binding of Na+ and amino acid
49
What do antiports do?
Move two substances in opposite directions
50
Give an example of an antiport.
Sodium-potassium pump moves 3 molecules of Na+ out and 2 molecules K+ in
51
What are symports and antiports known as?
Coupled transporters | Because they move two substances at once
52
What are the two types of active transport?
Primary active transport | Secondary active transport
53
What is primary active transport?
Requires direct participation of energy rich ATP
54
What is secondary active transport?
Does not use ATP directly | Energy is supplied by an ion concentration gradient established by primary active transport
55
What does secondary active transport aid in?
Uptake of amino acids and sugars
56
Why cant macromolecules such as proteins, polysaccharides and nucleic acids pass through membranes?
They are too large, too charged and/or polar
57
How do large macromolecules pass biological membranes?
Endocytosis | Exocytosis
58
What is endocytosis?
Process by which mall molecules, macromolecules, large particles and even small cells are brought into the eukaryotic cell
59
What are the three types of endocytosis?
Phagocytosis Pinocytosis Receptor-mediated endocytosis
60
What is phagocytosis?
Plasma membrane engulfs large particles or entire cells
61
Where is phagocytosis used?
Unicellular protists as cellular feeding White blood cells to defend body Food vacuole or phagosome fuses with lysosome for digestion
62
What is pinocytosis?
Small vesicles bring small, dissolved substances or fluids into the cell
63
Where does pinocytosis occur?
Endothelium- the single layer of cells separating tiny blood capillaries from surrounding tissue for cells to acquire fluids from the blood
64
What is receptor-mediated endocytosis?
Specific reactions at the cell surface trigger the uptake of specific materials
65
What does receptor-mediated endocytosis depend on?
Receptor-proteins
66
What is the first step in receptor-mediated endocytosis?
Receptor proteins on the extracellular surface bind with specific substances. These sites are called coated pits
67
What is the cytoplasmic surfaces behind a coated pit coated in?
Other proteins such as clathrin
68
What happens once a receptor binds to a specific ligand?
Coated pit invaginates and forms a coated vesicle
69
What does clathrin do?
Strengthen and stabilize the coated vesicle
70
What happens to a coated vesicle once inside the cell?
The clathrin is lost May fuse with lysosome Engulfed material is processed and released into the cytosome
71
How is cholesterol taken up by mammalian cells?
Receptor-mediated endocytosis
72
Where are LDL's taken up?
The liver for recycling
73
What is exocytosis?
The process by which materials packaged in vesicles fuses with the plasma membranes and materials are moved out of the cell
74
Where is exocytosis important?
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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