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AS Level Biology Unit 1 > 1.3 Cell Membrane + Transport (osmosis) > Flashcards

1.3 Cell Membrane + Transport (osmosis) Flashcards

1
Q

what is osmosis?

A

the diffusion of water from a region of high water potential to low water potential across a selectively permeable membrane

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2
Q

what are special membrane channel proteins that transport water called?

A

Aquaporins

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3
Q

what are dissolved substances called?

A

solutes

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4
Q

what does water potential measure ?

A

measures the concentration of free water molecules

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5
Q

what is water potential?

A

the tendency of water molecules to diffuse from one solution to another

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6
Q

what process does water diffuse by?

A

osmosis

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7
Q

what is water potential measured in?

A

kilopascals (kPa)

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8
Q

what is the water potential of pure water ?

A

0 kPa

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9
Q

what are three types of osmosis?

A

hypertonic
hypotonic
isotonic

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10
Q

hypertonic

A

solute conc is greater inside the cell than outside - cell loses water

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11
Q

hypotonic

A

solute conc is less than that inside the cell - cell gains water

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12
Q

isotonic

A

external and internal solute potential are the same

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13
Q

what happens to plant cell placed in pure water ?

A

cell swells and becomes turgid
vacuole is filled with water

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14
Q

why does the cell not burst in hypotonic solutions ?

A

due to the strength of the cell wall

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15
Q

what happens if the plant is placed in a hypotonic solution?

A

water enters by osmosis
causes the cell to swell and become firm
plant cells becomes TURGID

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16
Q

what happens when plant cell is placed in hypertonic solution?

A

water moves out of the cell by osmosis
causes the membrane to pull away from cell wall
causes vacuole to shrink and become FLACCID
PLASMOLYSED

17
Q

what is said to happen to the cell in hypertonic solutions?

A

cell becomes plasmolysed

18
Q

animal cell in hypotonic solution?

A

no cell wall causing cell to burst and become lysed

19
Q

animal cell in a hypertonic solution?

A

water leaves by osmosis cell appears wrinkled crenated

20
Q

what is the role of cell wall?

A

cell wall does not stretch
generates pressure potential

21
Q

what is solute potential at incipient plasmolysis?

A

solute potential = water potential

22
Q

what is point of incipient plasmolysis?

A

plasmolysis has just taken place
half cells plasmolysed half not

23
Q

what is a sodium potassium pump ?

A

uses protein pump to move Na+ and K+ in and out cells

24
Q

use of proton pump?

A

an active transport protein
uses ATP to transport hydrogen ions out of the cell

25
Q

explain why there is no decrease in mass at any of the sucrose concentrations?

A

loss of mass is not linked to water movement

AS Level Biology Unit 1 (10 decks)

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