Unit 1.2 Cell Transport

Question 1

Fluid-mosaic model

Answer 1

Describes the structure of cell membranes.

They are made of a double layer of phospholipids with protein molecules floating in it.

Membranes are very flexible and can change shape easily.

Question 2

Membrane proteins

Answer 2

Proteins found in the cell membrane.

Functions include transport proteins, channels, receptors, antigens and enzymes.

Question 3

Selectively permeable

Answer 3

Some molecules can pass through the membrane, and others cannot.

Allows the entry and exit of materials to be controlled.

Question 4

Concentration

Answer 4

Describes the number of particles in a given volume.

Question 5

Concentrated solution

Answer 5

A concentrated solution has a large number of solute particles, compared to water.

Question 6

Dilute solution

Answer 6

A dilute solution has a lower number of solute particles, compared to water.

Question 7

Passive transport

Answer 7

Does not require energy.

Examples are diffusion and osmosis.

Question 8

Concentration gradient

Answer 8

The difference between areas of high and low concentration.

The bigger the difference, the steeper the gradient and the faster particles will move.

Question 9

Diffusion

Answer 9

The movement of particles from a high to a low concentration along a concentration gradient.

It is a passive process, that does not require energy.

Question 10

Impermeable

Answer 10

Molecules are not able to pass through.

Membranes are impermeable to large molecules such as starch.

Question 11

Osmosis

Answer 11

The movement of water from an area of high to low water concentration (from a dilute to a concentrated solution) along a concentration gradient.

It happens through a selectively permeable membrane.

It is a passive process that does not require energy.

Question 12

Solution

Answer 12

A solute (eg. salt, sugar) dissolved in a solvent (eg, water) creates a solution.

Question 13

Molarity

Answer 13

A measure of how concentrated a solution is by describing how many solute particles there are.

0.5 M is less concentrated than 1 M. It has fewer solute particles dissolved in the same volume of water.

Question 14

Turgid

Answer 14

Plant cells fill up with water as a result of osmosis, and the cell contents push against the cell wall.

Turgid cells push against each other and hold a plant upright.

Question 15

Visking tubing

Answer 15

Artificial membrane, which can be used to investigate osmosis.

Question 16

Plasmolysed

Answer 16

Water moves out of a plant cell by osmosis, and the cell membrane starts to pull away from the cell wall.

Question 17

Active transport

Answer 17

The transport of molecules and ions against a concentration gradient, from low to high concentration.

It is an active process which requires energy in the form of ATP.

A specialised membrane protein is required, which acts as a pump.