excretion

Question 1

what is excretion?

Answer 1

the removal of the waste substances of metabolic reactions, toxic materials and substances in the excess of requirements

Question 2

what are some metabolic waste products formed by humans?

Answer 2

• carbon dioxide & water from aerobic respiration in cells
• urea- formed by the breakdown of excess proteins in the liver
• other substances in excess- like antibiotics and sodium

Question 3

what effects can occur if waste products build up in the body?

Answer 3

• toxicity
• osmotic effect
• using up necessary storage

Question 4

how can waste products be toxic?

Answer 4

• if they reach high concentrations
• carbon dioxide dissolves in water- forms an acidic solution that lowers the pH of cells- can reduce the rate of enzymes in the body which are essential for controlling the rate of metabolic reactions

Question 5

how can waste products affect the osmotic effect?

Answer 5

• body fluids can become more concentrated if there are higher amounts of waste products
• concentrated body fluids can cause water to move out of cells- changing their water potential and preventing them from carrying out essential reactions

Question 6

what do humans store carbohydrates and lipids as?

Answer 6

fat tissue

Question 7

where is carbon dioxide removed from?

Answer 7

the lungs via the blood plasma

Question 8

where is urea made?

Answer 8

liver cells

Question 9

how is urea made?

Answer 9

the breakdown of amino acids (deamination)

Question 10

where is urea removed from?

Answer 10

kidneys and the skin

Question 11

what are the 4 excretory organs of the body?

Answer 11

• kidneys
• skin
• liver
• lungs

Question 12

what do the kidneys excrete?

Answer 12

urea, water and mineral ions

Question 13

what do the lungs excrete?

Answer 13

carbon dioxide and water

Question 14

what does the skin excrete?

Answer 14

excess mineral ions e.g. sodium and water

Question 15

what does the liver do?

Answer 15

the breakdown of amino acids into urea