UNIT 1: (1.2) Transport Across Cell Membranes

Question 1

What is the function of the cell membrane

Answer 1

Allow transport of molecules or ions in and out the cell

Question 2

What is the cell membrane composed of ?

Answer 2

Phospholipid (fat) bilayer and protein molecules

Question 3

What is the structure of the cell membrane called ?

What does it stand for ?

Answer 3

• Fluid mosaic
• Fluid : due to the constant movement of the phospholipid bilayer
• Mosaic : due to the patchy distribution of proteins throughout the bilayer

Question 4

What is the definition of diffusion ?

Answer 4

Diffusion is the movement of molecules from a region of high concentration to a region of lower concentration down a concentration gradient

Question 5

What type of transport is diffusion ?

Answer 5

Passive transport ( as it requires no energy )

Question 6

What does it mean if the cell membrane is selectively permeable ?

Answer 6

It will only allow the passage of some molecules and not others

Question 7

What is a concentration gradient ?

Answer 7

A concentration gradient is the difference in concentration between the regions of high concentration and low concentration.

Question 8

What is passive transport ?

Answer 8

Passive transport involves the movement of molecules down a concentration gradient without using any energy

Question 9

Why is diffusion important ?

Answer 9

multicellular organisms - it allows the movement of molecules like oxygen from the lungs into the blood .

unicellular organisms- allows it to obtain resources needed to survive like oxygen in it’s surrounding environment

Question 10

What is the definition of osmosis ?

Answer 10

Osmosis is the movement of water molecules from a region of high water concentration to a region of lower water concentration though a selectively permeable membrane

Question 11

What does osmosis only refer to ?

Answer 11

It only refers to the movement of water in and out of cells

Question 12

What happens when a plant cell is placed in water or a dilute solution?

Answer 12

• water molecules move into the cell due to osmosis ( gains water )
• plant cell becomes turgid
• cell wall prevents it from bursting

Question 13

What happens to a plant cell when placed in a solution of equal water concentration ?

Answer 13

• No net movement of water molecules due to lack of a water concentration gradient
• No change in appearance

Question 14

What happens to a plant cell when placed in a concentrated solution ?

Answer 14

• water molecules move out of the cell due to osmosis ( loses water )
• plant cell becomes plasmolysed

Question 15

What happens when a animal cell (red blood cell ) is placed in water or a dilute / weak solution ?

Answer 15

• water molecules move into the cell due to osmosis ( gains water )
• cell bursts

Question 16

What happens when an animal cell ( red blood cell ) is placed in a solution of equal water concentration ?

Answer 16

• No net movement of water molecules due to the lack of a water concentration gradient
• No change in appearance

Question 17

What happens when an animal cell ( red blood cell ) when placed in a strong solution ?

Answer 17

• water molecules move out of the cell due to osmosis ( lose water )
• cell shrinks

Question 18

What is the definition of active transport ?

Answer 18

Active transport is the movement of molecules or ions by carrier proteins in the cell membrane from a region of low concentration to a region of higher concentration against a concentration gradient

Question 19

What does active transport require ?

Answer 19

It requires energy in the form ATP as it moves against the concentration gradient

Question 20

How is ATP produced ?

Answer 20

Produced by a chemical process called respiration.

Question 21

What are factors that effect the rate of respiration?

Answer 21

• oxygen concentration
• Glucose availability
• Temperature

Question 22

What does the rate of respiration also effect ?

Answer 22

Rate of active transport

Question 23

What is an example of active transport in plants ?

Answer 23

Some seaweeds and corals accumulate iodine from sea water in their cells to a concentration hundreds of times greater that that in the surrounding water

Question 24

What is an example of active transport in animal cells ?

Answer 24

Reabsorption of glucose from kidney tubules back into the bloodstream ensuring that glucose I not lost in urine .

Question 25

What are examples of passive transport ?

Answer 25

• Diffusion

* Osmosis

Question 26

What are solids, liquids and gases made up of ?

Answer 26

Small particals called molecules