Excretion

Question 1

what is excretion?

Answer 1

the removal of metabolic waste from the body

Question 2

what are the main excretory products?

Answer 2

carbon-dioxide from respiration, nitrogen containing compounds such as urea, other compounds such as bile pigments

Question 3

Where does the blood flow in the hepatic artery?

Answer 3

From the heart to the liver carrying oxygenated blood

Question 4

Where does blood flow in the hepatic portal vein?

Answer 4

From the digestive system to the liver carrying deoxygenated blood rich in products of digestion

Question 5

Where does the hepatic vein take blood?

Answer 5

away from the liver

Question 6

What is a sinusoid?

Answer 6

where oxygenated and deoxygenated blood mix to join together and form the hepatic vein, blood flowing along here comes into close contact with the liver cells

Question 7

What are kupffer cells?

Answer 7

specialised macrophges which breakdown and recycle old blood cells

Question 8

What are hepatpcytes?

Answer 8

liver cells that have a cuboidal shape with many microvilli on their surface

Question 9

What is the bile canaliculi?

Answer 9

a chamber which joins to the bile duct that transports bile to the gall bladder

Question 10

What does the enzyme catalase do in the liver?

Answer 10

converts hydrogen peroxide to oxygen and water

Question 11

what does cytochrome P450 do in the liver?

Answer 11

breakdown drugs including cocaine and various medicinal drugs

Question 12

How is alcohol broken down?

Answer 12

ethanol is broken down into ethanal by ethanol dehydrongenase. Ethanal is dehyrdogenated further by the same enzyme. This produces ethanoic acid. Ethanoate (acetate) is combined with coenzyme A to form acetyl coenzyme A

Question 13

Why do we not excrete the whole of an amino acid molecule?

Answer 13

they contain a lot of energy

Question 14

what processes occur during the formation of urea?

Answer 14

deamination and the ornithine cycle

Question 15

what occurs during deamination?

Answer 15

the amino group is removed and ammonia is produced as well as keto acid

Question 16

what is keto acid used fr?

Answer 16

respiration

Question 17

what happens in the ornithine cycle?

Answer 17

ammonia is combined with carbon dioxide to produce urea. Ammonia and carbon dioxide combine with the amino acid ornithine to produce citrulline. This is converted to arginine by adding more ammonia. The arginine is re-converted to ornithine by the removal of urea

Question 18

what is the function of the kidney?

Answer 18

to filter blood and remove excess ions/water to produce urine

Question 19

what are the regions within the kidney?

Answer 19

outer region - cortex
inner region - medulla
centre - pelvis leading to ureter

Question 20

what is ultrafiltration?

Answer 20

filtration of the blood at a molecular level under pressure

Question 21

what are the three layers adapted to enable ultrafiltration?

Answer 21

the endothelium of the capillary, the basement membrane, the epithelial cells of the bowmans capsule

Question 22

how is the endothelium of the capillary adapted?

Answer 22

there are narrow gaps between the endothelium cells of the capillary wall which substances to pass out

Question 23

how is the basement membrane adapted?

Answer 23

consists of a fine mesh of collagen fibres and glycoproteins which prevent molecules larger then 69,000 molecular mass, from passing

Question 24

how is the epithelial cells of the bowmans capsule adapted?

Answer 24

they have cells called podocytes which have projections called major processes. Each major process has minor processes that hold cells away from the endothelium of the capillary - ensuring there are gaps between the cells