B5 Controlling Water Content

Question 1

What role do kidneys play in homeostasis?

Answer 1

They help regulate water content

Question 2

What are body cells surrounded by?

Answer 2

Tissue fluid

Question 3

Where does tissue fluid come from?

Answer 3

It is squeezed out of the blood capillaries to supply the cells with everything they need.

Question 4

How and why does water move from the tissue fluid to the cell?

Answer 4

Because they usually have a different concentration to the fluid inside a cell.

This means water will either move into the cell from the tissue fluid or out of the cell by osmosis.

Question 5

What happens if there are more water molecules in the tissue fluid than in the cell?

Answer 5

There will be a net movement of water into the cell by osmosis.

Question 6

What happens if too much water moves into the cell?

Answer 6

The cell may burst.

This is called lysis

Question 7

What happens if there are fewer water molecules in the tissue fluid than in the cell?

Answer 7

There will be a net movement of water out of the cell and into the tissue fluid.

Question 8

What happens to the cells when there is a net movement of water into the tissue fluid?

Answer 8

They shrink

Question 9

What is lysis?

Answer 9

If too much water moves into the cell, then the cell may burst.

Question 10

What happens if the concentration of water molecules in the tissue fluid is roughly the same as the cell?

Answer 10

They will stay the same.

Question 11

Why is it important that the water content of the blood is controlled?

Answer 11

This controls the water content of the tissue fluid and keeps cells the cells functioning normally.

Question 12

Why do animal cells burst when they contain too much water?

Answer 12

Because they don’t have a rigid cell wall (unlike plants)

Question 13

What role do kidneys play in balancing the level of water in the body?

Answer 13

They control how much water is lost in urine by varying the volume of urine produced and how concentrated it is.

They get rid of waste and control levels of other substances in the body.

Question 14

What are kidney tubules?

Answer 14

Millions of little structures inside the kidneys

Question 15

See p 80 for diagram of the kidneys and tubule.

Answer 15

.

Question 16

Parts of kidney system

Answer 16

Renal vein
Renal artery
Cortex
Medulla
Kidney
Ureter

Question 17

Where is urine formed?

Answer 17

In the tubules

Question 18

What happens in the glomerulus?

Answer 18

Blood flows through it at high pressure and small molecules including water, sugar, salt and urea are filtered out into the capsule.

Question 19

What happens to the liquid in the capsule?

Answer 19

It flows along the tubule and useful substances are selectively reabsorbed.

Question 20

How much sugar is reabsorbed?

Answer 20

All the sugar is reabsorbed

Question 21

How much salt is reabsorbed?

Answer 21

Sufficient salt is reabsorbed, excess salt isn’t

Question 22

How much water is reabsorbed?

Answer 22

Sufficient water is reabsorbed, according to the level of the hormone ADH.

This helps keep the blood plasma at the correct concentration to prevent cell lysis or shrinkage.

Question 23

What happens to substances that are absorbed in the tubule?

Answer 23

They form urine, which is excreted by the kidney and stored in the bladder.

Question 24

Explain what might happen to an animal cell surround by a less concentrated solution. (2 marks)

Answer 24

The cell may burst/lysis may occur (1 mark) as there will be a net movement of water into the cell by osmosis (1 mark)