transport across cell membrane

Question 1

what does the cell membrane consist of?

Answer 1

phospholipids and proteins

Question 2

further function of the cell membrane?

Answer 2

controls the substances that enter and exit the cell as it is selectively permeable

Question 3

selectively permeable membrane?

Answer 3

allows small molecules to enter the cell but not large molecules as they are too big to fit through

Question 4

what are examples of small molecules?

Answer 4

• oxygen
• carbon dioxide
• water
• glucose
• fatty acids/glycerol/amino acids

Question 5

what are examples of large molecules?

Answer 5

• starch (carbohydrates)
• protein
• fat

Question 6

what is passive transport?

Answer 6

does not require energy (ATP) to move molecules across membrane

Question 7

what are two examples of passive transport?

Answer 7

• diffusion
• osmosis

Question 8

what is active transport?

Answer 8

the movement of molecules from an area of low concentration to an area of high concentration against the concentration gradient
requires energy (ATP)

Question 9

what is diffusion?

Answer 9

the movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient

Question 10

what must be remembered about diffusion?

Answer 10

• it does not require energy (ATP)
• eventually the concentration inside the cell will be the same as the concentration outside the cell

Question 11

what is osmosis?

Answer 11

the movement of water molecules from an area of higher water concentration to an area of lower water concentration through a selectively permeable membrane

Question 12

what happens to animal cells when placed in a high concentration of water?

Answer 12

• there is a high water concentration outside of the cell
• water moves from a high to a low concentration into the cell
• CELL BURSTS

Question 13

what happens to animal cells when placed in a low concentration of water?

Answer 13

• there is a higher water concentration inside the cell
• water moves from a high to a low concentration out of the cell
• CELL SHRINKS

Question 14

what happens to plant cells when placed in a low concentration of water?

Answer 14

• there is a higher water concentration inside the cell
• water moves from a high to a low concentration out of the cell
• cell becomes PLASMOLYSED

Question 15

what happens to plant cells when placed in a high concentration of water?

Answer 15

• there is a high water concentration outside of the cell
• water moves from a high to a low concentration into the cell
• cell becomes TURGID

Question 16

explain why plant cells do not burst

Answer 16

plant cells have a cell wall, cell walls prevent the cell from bursting

Question 17

turgid cells

Answer 17

• vacuole has swollen (taken in extra water)
• cytoplasm and cell membrane push against the cell wall
• the cell wall supports cell preventing it from bursting

Question 18

plasmolysed cells

Answer 18

• vacuole has shrunk
• cytoplasm and cell membrane pull away from the cell wall
• the cell wall supports cell preventing it from shrinking