Unit 1: Transport Across Cell Membranes Booklet Key Points

Question 1

What denatures proteins?

Answer 1

Ph and high temperatures

Question 2

What destroys phospholipids?

Answer 2

Alcohol

Question 3

What is the cell membrane composed of?

Answer 3

Proteins and phospholipids

Question 4

How do you know that the cell membrane contains proteins and phospholipids?

Answer 4

From an experiment to investigate the nature of the cell membrane using discs of cabbage by submerging them in acid, alcohol or boiling, I now know that the cell membrane contains proteins and phospholipids as the dye from the cabbage bled into the substances with high heat, acid or alcohol in them. This shows that they dye escaped the cell due to these conditions

Question 5

What is the function of the cell membrane?

Answer 5

To control what enters and exits the cell.

Question 6

What do the two main parts of a cell membrane do?

Answer 6

The phospholipids make the membrane fluid and able to move. The protein part are found within the membrane and on each surface

Question 7

What do some proteins have that allows substances into and out of the cell?

Answer 7

Some proteins have a channel running through them. This allows certain substances to pass into and out of the cell.

Question 8

What is the membrane described as being?

Answer 8

Selectively permeable

Question 9

What substances can pass through the membrane?

Answer 9

Amino acids, fatty acids, glucose, cells

Question 10

What substances cannot pass through the membrane?

Answer 10

Starch, proteins, fats

Question 11

Explain diffusion

Answer 11

The molecules of liquids and gases move about freely all the time. If a substance is introduced, the molecules of this substance will move from a region of high concentration to a region of lower concentration until the concentration in all areas is equal. This process occurs passively with no energy input. The name given to this movement of molecules is diffusion.

Question 12

What does the concentration gradient mean?

Answer 12

The concentration gradient means that the concentration of a particular substance is greater on one side than on the other

Question 13

What is the relationship between the concentration gradient and rate of reaction?

Answer 13

The greater the difference in concentration, the faster the overall movement will be.

Question 14

What is the difference between required substances and harmful substance during diffusion?

Answer 14

Substances required by a cell move into the cell from a higher concentration outside the cell to a lower concentration inside the cell.

Harmful substances leave the cell by diffusion from a higher concentration inside the cell to a lower concentration outside the cell.

Question 15

Why is diffusion important to cells?

Answer 15

The gain from raw materials (oxygen and glucose) for respiration.
They remove harmful waste products (carbon dioxide)

Question 16

What is the definition of diffusion?

Answer 16

Diffusion is the movement of the molecules of a substance down a concentration gradient from a region of higher concentration to a region of lower concentration until the concentration becomes equal.

Question 17

What is the definition of osmosis?

Answer 17

Osmosis is the movement of water from a higher water concentration to a lower water concentration across a selectively permeable membrane.

Question 18

What should you do when answering a question on osmosis?

Answer 18

It is important to convert the concentration of the solute to the concentration of water. That way it is easier to identify which side has the highest water concentration. Think of pure water as being 100% or 100mM or 100M or 100mol l-1 and subtract the solute value. This gives you a comparison of the water concentration.

Question 19

How does osmosis affect plant cells?

Answer 19

If water moves into a normal cell, it becomes turgid.

If water moves out of a normal cell, it becomes plasmolysed.

Question 20

How does osmosis affect animal cells?

Answer 20

If water moves into a normal cell, the cell will burst because it doesn’t have a cell wall.

If water moves out of a normal cell, the cell will shrink.

Question 21

How are the cells affected by osmosis?

Answer 21

When animal cells are placed in a solution with a higher water concentration, the water moves in by osmosis and the cells burst. When animal cells are placed in a solution with lower water concentration, the water moves out by osmosis and the cells shrink. The animal cells burst because they don’t have a cell wall. When plant cells are placed in a solution with a higher water concentration, the water moves in by osmosis and the cells become turgid. The cells do not burst because they have a cell wall. When plant cells are placed in a solution with a lower water concentration, the water moves out by osmosis and the cells become plasmolysed.

Question 22

What are factors affecting the rate of active transport which are needed to produce ATP from aerobic respiration?

Answer 22

Oxygen concentration
Glucose concentration
Temperature

Question 23

What is active transport?

Answer 23

Active transport is when a substance moves across a cell membrane against a concentration gradient from a lower concentration to a higher concentration. This process requires energy to transport the substances from a lower concentration to a higher concentration. Substances cross the membrane through a protein molecule