Excretion

Question 1

What is excretion?

Answer 1

The removal of metabolic waste products from the body

Question 2

What are the three reasons why is excretion important?

Answer 2

-They could become toxic if they build up
-It keeps levels low/constant which helps to maintain homeostasis
-As it prevents them causing end-product inhibition

Question 3

What are the 3 products we need to excrete?

Answer 3

-Nitrogenous Waste
-Bile Pigment
-CO2

Question 4

Why do we need to excrete Nitrogenous Waste?

Answer 4

Excess amino acids which contain nitrogen can’t be stored as too much can become toxic so they need to be excreted

Question 5

How is Nitrogenous Waste excreted in fish, insects/birds and mammals?

Answer 5

Fish-ammonia
Insects/Birds-Uric Acid
Mammals-Urea

Question 6

What is uric acid?

Answer 6

Solid, clear and crystalline

Question 7

Why do we need to excrete Bile Pigment?

Answer 7

Old RBC’s are broken down by kupffer cells then the hepatocytes break down Hb into bilirubin

Question 8

What happens to the bilirubin?

Answer 8

It’s put into bile and excreted with bile and colours faeces brown

Question 9

How is CO2 excreted?

Answer 9

-Hydrogen carbonate ions are produced in the erythrocytes and diffuse into the plasma
-CO2 enters the erythrocytes and reacts with water to produce carbonic acid which is catalysed by carbonic anhydrase
-Carbonic acid dissociates which forms hydrogen carbonate ions
-Haemoglobinic acid is formed which prevents H+ ions causing drop in pH so enzymes denature
-Chloride Shift happens to balance out the charge.

Question 10

What do Haemoglobinic Acid and Carbaminohaemoglobin cause?

Answer 10

A change in the tertiary/quaternary structure of Hb so Hb dissociates from O2 more easily=more O2 to cells