5.1.2 - excretion - the liver

Question 1

excretion

Answer 1

removal of the waste products of metabolism from the body

Question 2

how is carbon dioxide excreted

Answer 2

excreted from the lungs as one of the waste products of cellular respiration

Question 3

how are bile pigments excreted

Answer 3

excreted in the bile from the liver into the small intenstine via the gall bladder and bile duct

Question 4

how are bile pigments formed

Answer 4

formed in the breakdown of haemoglobin from old red blood cells in the liver

Question 5

why is the release of faeces called egestion, not excretion?

Answer 5

not involved in metabolic reactions in cells, just undigested food which have never entered the bloodstream.

Question 6

why do we get rid of metabolic waste products

Answer 6

they can alter the pH interfering with cell processes so the normal metabolism is affected, they may also inhibit enzymes

Question 7

why must we excrete nitrogenous compounds?

Answer 7

amino acids cant be stored because they have a toxic animo group that needs removing

Question 8

hepatic artery

Answer 8

supplies the liver with oxygenated blood from the heart so the liver gas a good supply of oxygen for respiration, providing plenty of energy

Question 9

hepatic vein

Answer 9

takes deoxygenated blood away from the liver

Question 10

hepatic portal vein

Answer 10

brings blood from the small intestine so its rich in the products of digestion; means any harmful substances are filtered out and broken down straight away

Question 11

bile duct

Answer 11

duct that carries the bile secreted in the liver from the liver to the gall bladder

Question 12

why is it important that the blood flows from the stomach and intestines to the liver before it enters general circulation?

Answer 12

so that any toxins which entered blood can be removed from blood before general circulation (preventing potential harm)

Question 13

lobules

Answer 13

cylinderical structures made up of rows of individual liver cells called hepatocytes

Question 14

in what vessel does blood from the vein and arteries mix

Answer 14

sinusoids

Question 15

role of the hepatocytes

Answer 15

remove oxygen, release carbon dioxide and detoxify the blood as it flows past

Question 16

what is the purpose of blood passing through sinusoids

Answer 16

put the blood in close contant with liver cells that alter the concentrations of substances in it

Question 17

canaliculi

Answer 17

little channeks that collect the bile made by the hepatocytes

Question 18

kupffer cells

Answer 18

deal with any pathogens entering the liver

Question 19

how do hepatocytes store glycogen

Answer 19

in granules in the cytoplasm

Question 20

how does bile help with digestion

Answer 20

bile emulsifies lipids (fats), it breaks them down into smaller droplets which have a high surface area so they can be acted on more efficiently by lipase enzymes

Question 21

how is alcohol broken down by detoxification

Answer 21

ethanol is broken down by ethanol dehydrogenase to ethanal which is then converted to ethanoate.
this is converted into fatty acids, then into acetyl co-A which can be used in respiration

Question 22

what is deamination?

Answer 22

the removal of the amino group from an amino acid producing ammonia and a keto acid

Question 23

what is the ornithine cycle?

Answer 23

ammonia is converted to urea by combining it with co2 and the amino acid ornithine

Question 24

why do we convert ammonia into urea for excretion rather than just excreting the ammonia?

Answer 24

urea is less toxic and less soluble than ammonia
less water is needed to excrete it from the body (reduces water loss)

Question 25

function of the liver - carbohydrate metablism

Answer 25

when blood glucose levels rise, insulin levsls rise and stimulate hepatocytes to convert glucose to glycogen