B3.1 Movement of Molecules In And Out Of Cells

Question 1

How is osmosis used in the body?

Answer 1

• Tissue fluid (with oxygen and glucose dissolved in it) surrounds the cells in the blood capillaries
• If the cell is short of water: solution inside = concentrated, solution outside = dilute so water moves into the cells by osmosis.
• If the cell has excess water: solution inside = dilute, solution outside = concentrated so water moves out the cells by osmosis.

Question 2

What is active transport?

Answer 2

The process which allows cells to absorb ions from very dilute solutions against the concentration gradient.

Question 3

How does active transport work?

Answer 3

• Carrier proteins ‘pick up’ molecules

- Use ATP from respiration to drive them across the cell membrane.

Question 4

Define osmosis.

Answer 4

The passive movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.

Question 5

How are alveoli adapted for diffusion?

Answer 5

• Large surface area
• Moist lining for dissolving gases
• Very thin walls
• Good blood flow from capillaries to maintain concentration gradient.

Question 6

How are the villi in the small intestine adapted for diffusion?

Answer 6

• Large surface area (with micro-villi)
• Folded on the side of the lumen
• Very thin walls
• Good blood flow from capillaries to maintain concentration gradient.

Question 7

How are root hair cells adapted for diffusion?

Answer 7

• Large surface area

- Many mitochondria (to produce ATP for active transport)

Question 8

Why are minerals taken in by plants using active transport?

Answer 8

The concentration of minerals in the root hair cells is usually higher than the minerals in the soil around it.

Question 9

What do sports drinks contain?

Answer 9

Glucose, water, ions

Question 10

Why do sports drinks contain ions and water?

Answer 10

To replace what is lost during sweating.

Question 11

Why do sports drinks contain glucose?

Answer 11

To replace glucose used up during respiration to release energy for exercise.

Question 12

What happens if ions and water in the body are not replaced?

Answer 12

The water/ion balance of the body is disturbed and cells do not work as efficiently (too much/too little water will move out of cells)

Question 13

Describe the mechanism of inhalation.

Answer 13

• Diaphragm flattens
• Intercostal muscles contract
• Ribcage moves upwards and outwards
• Volume of the chest increases
• Pressure decreases
• Air is drawn into the lungs.

Question 14

Describe the mechanism of exhalation.

Answer 14

• Diaphragm moves upwards
• Intercostal muscles relax
• Ribcage moves downwards and inwards
• Volume of the chest decreases
• Pressure increases
• Air is forced out of the lungs.

Question 15

What is the function of the breathing system?

Answer 15

Takes air in and out of the body so oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out.

Question 16

Who uses artificial ventilators? (2)

Answer 16

• People on general anaesthetic

- People with lung injuries/disease

Question 17

Describe how a negative pressure ventilator works.

Answer 17

• Giant cylinder (‘iron lung’) where patients lay

- Air is pumped out of this so pressure decreases and air outside is drawn in.

Question 18

What is the problem with negative pressure ventilators?

Answer 18

• They interfere with blood flow

Question 19

How do positive pressure ventilators work?

Answer 19

• They pump air into the lungs which expands the ribcage.
• When the ribcage relaxes again, air is pushed out.
• ‘The shell’ is used which fits just around the chest.

Question 20

Why is ‘the shell’ a better model for ventilators?

Answer 20

• It is more portable, comfortable and allows patients to use it at home.

Question 21

What is the remaining problem with positive ventilators?

Answer 21

• They can sometimes cause damage (e.g burst alveoli)

Question 22

Where are lungs located?

Answer 22

In the thorax (top part of the body)

Question 23

What is the function of the ribcage?

Answer 23

To protect the lungs

Question 24

Describe the structure of the lungs.

Answer 24

• Air breathed in travels down the trachea
• This splits into two bronchi (one = bronchus)
• These split into bronchioles
• These end in small bags called alveoli.