transport across cell membranes

Question 1

what is the function of the cell membrane?

Answer 1

controls what enters and leaves the cell

Question 2

name the two main components of the cell membrane

Answer 2

proteins

phospholipids

Question 3

which component of the cell membrane helps to move molecules and ions by active transport?

Answer 3

protein

Question 4

name two substances which enter cells by diffusion

Answer 4

oxygen

Question 5

name a substance which leaves the cell by diffusion

Answer 5

carbon dioxide

Question 6

what is diffusion?

Answer 6

the movement of molecules from an area of high concentration to an area of low concentration of that substance

Question 7

why is the cell membrane described as “selectively permeable” ?

Answer 7

as the cell membrane allows some substance pass through with ease, while blocking other substances.

allows small molecules to pass but not large molecules

Question 8

explain why starch molecules are unable to diffuse across the cell membrane

Answer 8

as starch is an insoluble molecule which is too large to fit through the cell membrane

Question 9

small, soluble substances diffuse “down a concentration gradient”, what does this mean?

Answer 9

substances move from an area of high concentration to an area of low concentration of that substance

Question 10

describe two different between active and passive transport

Answer 10

active transport requires energy whereas passive transport does not require energy

passive transport is the movement of molecules along/ down the concentration gradient whereas active transport is the movement of molecules against the concentration gradient

Question 11

give two examples of passive transport

Answer 11

diffusion

osmosis

Question 12

describe how a plant cell becomes plasmolysed

Answer 12

plant cell is placed in a solution with a lower water concentration that inside the cells. water leaves the cell by osmosis

Question 13

describe the appearance of an animal cell shown which has been placed in a solution of higher salt concentration than its cell contents

Answer 13

shrunken

Question 14

glucose molecules in low concentration in the kidney are moved into the bloodstream, where there is a higher concentration of glucose. Name the process responsible for this action.

Answer 14

active transport

Question 15

what is the name given to the diffusion of water?

Answer 15

osmosis

Question 16

describe the appearance of a plant cell placed in pure water

Answer 16

Turgid - swell up

Question 17

name the structure of the plant cell that prevents it from bursting when full of water

Answer 17

cell wall

Question 18

a piece of beetroot was placed in a salt solution with a water concentration lower than that in the cells. after 1 hour the mass of the beetroot had reduced by 0.3g. explain how osmosis caused this loss of mass.

Answer 18

water was lost from the beetroot as it moved out beetroot cell by osmosis from an area of high concentration to an area of low concentration. this caused the mass to decrease