Excretion

Question 1

Define ‘excretion’

Answer 1

The removal of toxic waste substances produces by the cells

Question 2

What is the process of the removal of faeces called?

Answer 2

Egestion

Question 3

What is the waste product of repiration, and how is it removed from animals and plants?

Answer 3

CO₂

Removed via the lungs in animals

Removed via the leaves in plants

Question 4

Where is CO₂ made in humans, how is it made, and where is it removed?

Answer 4

Made in the respiring cells

Made by respiration

Removed throught the lungs via blood plasma

Question 5

Where is urea made in humans, how is it made, and where is it removed?

Answer 5

Made in the liver cells

Made by the breakdown of amino acids

Removed by the kidneys and skin

Question 6

How are amino acids filtered into the liver?

Answer 6

Via the heptic artery

Question 7

What are excess amino acids within the liver broken down into?

Answer 7

Carbohydrates and ammonia

Question 8

What is ammonia broken down into within the liver?

Answer 8

Urea

Question 9

How are needed amino acids and urea released back into the blood stream?

Answer 9

Via the heptic vein

Question 10

What are the three main sections of the kidney?

Answer 10

Cortex, medulla, & pelvis

Question 11

What structures within the kidney filter the blood?

Answer 11

Nephrons

Question 12

Label the nephron

Answer 12

Question 13

Describe ultrafiltration

Answer 13

1. The artery at the exit of the glomerulus is smaller then that at the entrance, creating a large build up of pressure
2. The pressure forces small molecules such as urea, glucose, amino acids and salts across the Bowman’s Capsule top form the glomerular filtrate
3. Larger molecules like proteins or red blood cells are too big to fit across and therefore stay in the blood

Question 14

Describe selective reabsorption

Answer 14

1. The glomerular filtrate travels from the Bowman’s Capsule into the proximal convoluted tubule (PCT).
2. The specialised cells within the walls of the PCT pump the useful materials back into the blood stream against a concentration gradient using energy - active transport. All of the glucose is reabsorbed, along with 80% of the water.

Question 15

Describe water reabsorption

Answer 15

1. If you have lost a lot of water through sweating, or not drinking enough, your volume of urine will be lower as more water will be reabsorbed, and excess water will raise the volume.
2. This is controlled by Anti Diuretic Hormone (ADH), production of which is controlled by the hypothalamus in your brain, and if more water needs to be reabsorbed it will tell the pituitary gland to release more ADH
3. ADH is carried in the blood to the collecting ducts, diffusing onto the receptors on the collecting ducts, to tell it to become more permeable to water.