Excretion

Question 1

Definition of excretion

Answer 1

Removal of toxic waste products which have been made by cells.

Question 2

Waste product of lungs

Answer 2

Carbon dioxide

Question 3

Waste product of skin

Answer 3

Sweat that contains water, urea and salts

Question 4

Waste product of kidneys

Answer 4

Urea

Question 5

Where is urea made?

Answer 5

Liver

Question 6

Describe how ultrafiltration occurs

Answer 6

Higher pressure in capillaries forces small molecules (glucose, urea, salts, amino acids) out of the capillaries of the glomerulus and into the Bowman’s capsule. Forms glomerular filtrate. Larger molecules such as proteins or red blood cells are unable to fit across the capillary walls so stay in the blood.

Question 7

Composition of the glomerular filtrate

Answer 7

Glucose, amino acids, urea, salts (water)

Question 8

Where does selective reabsorption take place?

Answer 8

Proximal convoluted tubule (first loop after bowman’s capsule)

Question 9

How is the proximal convoluted tubule adapted for its function?

Answer 9

Many mitochondria to provide ATP (energy) for active transport.
Folded membrane to increase surface area

Question 10

How does selective reabsorption work?

Answer 10

Useful substances (glucose, amino acids) move by active transport (using energy back into the bloodstream. Some water and salts also move back into the bloodstream

Question 11

Describe how the body responds when the body is dehydrated

Answer 11

Osmoregulation
Hypothalamus detects low water in blood
Pituitary releases ADH
ADH increases permeability of collecting duct
More water is reabsorbed back into the blood
Less water enters urine, making it more concentrated

Question 12

What gland is ADH released by?

Answer 12

Pituitary gland