Excretion 5.2

Question 1

why is excretion important?

Answer 1

important in maintaining metabolism

Question 2

what is excretion?

Answer 2

process by which excess toxic waste products of metabolism are removed from the body

Question 3

give examples of excretory organs

Answer 3

lungs,kidney,liver and skin

Question 4

what is metabolic waste made of?

Answer 4

carbon dioxide

nitrogenous waste

bile pigments

Question 5

mammals produce urea, fish and birds/insects produce..?

Answer 5

fish- ammonia

birds and insects- uric acid

Question 6

what is bile pigments?

Answer 6

breakdown of haemoglobin from old red blood cells in the liver

they colour the faeces

Question 7

what is urea made of?

Answer 7

undigested food and fibre

Question 8

how does the skin act as an excretory organ?

Answer 8

sweat contains salts, urea, water, uric acid and ammonia

Question 9

what happens if products of metabolism build up in the body?

Answer 9

build up of CO2 and NH3 is toxic

this can interfere by altering the pH or act as inhibitors and reduce the activity of enzymes

Question 10

what is the role of the liver

Answer 10

breakdown of unwanted or toxic substances and the production of excretory waste,

Question 11

what are hepatocytes?

Answer 11

liver cells - cuboidal, undifferntiated with a cytoplasm

contains a nuclei, golgi apparatus, folded membrane and mitochondria

Question 12

what is the difference between the hepatic artery and hepatic vein

Answer 12

hepatic a - receives oxygenated blood from the heart ( smaller than v bcs carries only 30% blood)

hepatic v - brings deoxygenated blood back to heart (bigger bcs carries 70%)

Question 13

describe the internal structure of the liver

Answer 13

. hepatocytes
. lobes -> lobules (connective tissue)
. sinusoids ( wide capillaries)
. branch of hepatic vein ( drains blood away from lobule)

Question 14

explain why the liver has 2 supplies of blood

Answer 14

hepatic artery carries oxygenated blood from heart to liver which is needed for respiration.

hepatic vein carries deoxygenated blood away from liver to heart to prevent the build up of toxic products

Question 15

why might blood in the hepatic portal vein contain toxins

Answer 15

after digestion of alcohol, blood from the intestine contains toxins

Question 16

what are the functions of liver

Answer 16

storage of glycogen

detoxification

formation of urea

Question 17

explain the role of the liver in storing glycogen

Answer 17

hepatocytes are involved in converting glucose into glycogen

glycogen can be broken down to release glucose into the blood

Question 18

explain how detoxification works on hydrogen peroxide (substance in the liver)

Answer 18

catalase breaks down hydrogen peroxide into oxygen and water (by-product)

Question 19

explain how detoxification works on recreational drugs / medicines

Answer 19

cytochrome P450, (group of enzymes) , break them down

Question 20

explain how detoxification works on alcohol (5 marks)

Answer 20

ethanol, broken down by hepatocytes using the enzyme ethanol dehydrogenase into ethanal

ethanal is further dehydrogenated by etanal dehydrogenase to produce ethanoate (actetate)

acetate combines with coenzyme A to form acetyl CoA (which is used in cellular respiration)

the hydrogen atoms released combine with coenzyme NAD and forms reduced NAD

Question 21

what does NAD do

Answer 21

breakdown fatty acids used in respiration

Question 22

what happens if NAD is used up

Answer 22

breakdown of fatty acids is no longer possible

FA converted back to lipids

builds up in liver and can cause hepatitis or cirrhosis

Question 23

describe AA in the liver

Answer 23

excess amino acids cant be stored in the body as their amino group make them toxic

they cant also be excreted as a whole because theyre full of lots of energy

so, excreted via deamination

Question 24

what is deamination

Answer 24

removal of an amino group from the amino acid leaving ammonia

Question 25

describe ammonia in the liver

Answer 25

very toxic and insoluble , quickly converted in to urea which is less soluble and less toxic

Question 26

what are the products of deamination?

Answer 26

ammonia and keto acid

Question 27

what do the branch of hepatic vein and artery do

Answer 27

supply blood to the lobules

Question 28

what is the difference between hepatic vein and portal vein

Answer 28

vein- carries deoxygenated blood to heart

portal vein- carries deoxygenated blood to live