Unit 1- Transport Across Cell Membranes

Question 1

What is active transport?

Answer 1

The movement of molecules and ions across the plasma membrane from a lower to a higher concentration against a concentration gradient.

Question 2

What is required for active transport?

Answer 2

Energy

Question 3

What are the two main components of the cell membrane?

Answer 3

Phospholipids and proteins

Question 4

What does selectively permeable mean?

Answer 4

Only allows certain substances to pass through

Question 5

Describe the process of osmosis.

Answer 5

The movement of water molecules from a higher water concentration to a lower water concentration through a selectively permeable membrane.

Question 6

What happens to an animal cell placed in a higher water concentration outside than inside?

Answer 6

It bursts

Question 7

What happens to an animal cell in a solution with a lower water concentration?

Answer 7

It shrinks

Question 8

What happens to a plant cell placed in a solution with a lower water concentration?

Answer 8

It becomes plasmolysed

Question 9

What happens to a plant cell in a solution with a higher water concentration?

Answer 9

It becomes turgid

Question 10

Define diffusion.

Answer 10

Movement of ions or molecules from a higher to lower concentration.

Question 11

What is the energy requirement for diffusion?

Answer 11

Passive

Question 12

What is the energy requirement for osmosis?

Answer 12

Passive

Question 13

What is the percentage change formula?

Answer 13

Percentage change = (Change in mass / Initial mass) x 100

Question 14

What is the average final mass calculation for a group of potatoes?

Answer 14

Total mass of potatoes / Number of potatoes

Question 15

Which direction do particles move in diffusion?

Answer 15

From higher concentration to lower concentration

Question 16

What are examples of useful substances that enter cells by diffusion?

Answer 16

Oxygen and glucose

Question 17

What are examples of waste substances that leave cells by diffusion?

Answer 17

Carbon dioxide and urea

Question 18

What are the effects of osmosis on animal and plant cells?

Answer 18

• Animal cells may burst or shrink
• Plant cells may become turgid or plasmolysed

Question 19

Fill in the blank: Water leaves the cell by osmosis and the membrane peels away from the cell wall, the cell is said to be _______.

Answer 19

plasmolysed

Question 20

What stops a plant cell from bursting in a higher water concentration solution?

Answer 20

Cell wall

Question 21

What happens to a plant cell in a solution with equal water concentration?

Answer 21

No change

Question 22

What is the difference between diffusion and active transport?

Answer 22

Diffusion moves down a concentration gradient passively; active transport moves against a gradient and requires energy.

Question 23

What is the function of proteins in the cell membrane?

Answer 23

To facilitate transport and communication across the membrane.

Question 24

What is the outcome if the mass of a potato stays the same in an osmosis experiment?

Answer 24

The sucrose concentration is the same as the potato cell sap.

Question 25

What is the term for the swelling of a plant cell when water enters by osmosis?

Answer 25

Turgid

Question 26

What happens to a red blood cell in a high water concentration solution?

Answer 26

It swells or may burst.

Question 27

True or False: Diffusion requires energy.

Answer 27

False

Question 28

True or False: Active transport involves moving substances against a concentration gradient.

Answer 28

True

Question 29

What is osmosis?

Answer 29

Movement of water molecules from a higher water concentration to a lower water concentration through a selectively permeable membrane.

Question 30

Define plasmolysed.

Answer 30

A condition where a cell has lost water and the cell membrane pulls away from the cell wall.

Question 31

Define turgid.

Answer 31

A condition where a cell is swollen due to water intake, pressing the cell membrane against the cell wall.

Question 32

What are the two components of a plasma (cell) membrane?

Answer 32

• Proteins
• Phospholipids

Question 33

What is the function of proteins in the cell membrane?

Answer 33

To act as channels or receptors.

Question 34

What feature allows the movement of only some substances into the cell?

Answer 34

Selectively permeable.

Question 35

Describe the process of diffusion.

Answer 35

Movement of molecules from an area of higher concentration to an area of lower concentration, down a concentration gradient.

Question 36

Name three substances that can enter a cell by diffusion.

Answer 36

• Glucose
• Oxygen
• Amino acids

Question 37

Name two substances that leave a cell by diffusion.

Answer 37

• Carbon dioxide
• Waste products (e.g., Urea)

Question 38

True or False: In osmosis, water molecules move down a concentration gradient.

Answer 38

True.

Question 39

What does ‘passive’ mean in the context of diffusion?

Answer 39

Does not require energy.

Question 40

What happens to glucose when tested with Benedict’s solution?

Answer 40

Changes from blue to orange.

Question 41

What happens to starch when tested with iodine solution?

Answer 41

Changes from brown to blue/black.

Question 42

Fill in the blank: Diffusion is the movement of molecules from a _______ concentration to a _______ concentration.

Answer 42

[higher] [lower]

Question 43

What allows dissolved substances to pass through the cell membrane?

Answer 43

Tiny pores in the cell membrane.

Question 44

True or False: Large substances like starch can easily pass through the pores of the cell membrane.

Answer 44

False.