Poisonous mushrooms Bill Indge Poisonous mushrooms Bringing it

Poisonous mushrooms Bill Indge

Poisonous mushrooms Bringing it all together Molecules Ecology Cells Poisonous mushrooms Genes and genetics Physiological systems

Poisonous mushrooms Amino acids and peptide bonds R R H H O N C OH H H C OH

Poisonous mushrooms Amino acids and peptide bonds R R H H O N C OH H H C OH

Poisonous mushrooms Amino acids and peptide bonds R R H H O N C H Peptide bond O N C C H OH

Poisonous mushrooms 1 (c) In the simplest cyclic polypeptides, the amino acids bind together to form a ring. How many peptide bonds would there be in a cyclic polypeptide containing eight amino acids? Explain how you arrived at your answer. (2 marks) Amino acid Peptide bond joining two amino acids

Poisonous mushrooms Digesting peptides and polypeptides Endopeptidases break peptide bonds in the middle of a polypeptide chain producing smaller polypeptides Exopeptidases break peptide bonds in the end of a polypeptide chain releasing amino acids

Poisonous mushrooms Exopeptidases break peptide bonds in the end of a polypeptide chain releasing amino acids 2 -amanitin is not broken down by endopeptidases. Use this information to suggest why exopeptidases do not digest -amanitin. (2 marks) Endopeptidases break peptide bonds in the middle of a polypeptide chain producing smaller polypeptides Cyclic polypeptide so no smaller polypeptides produced; No free amino/ carboxylic acid groups; Will not bind with enzyme;

Poisonous mushrooms Bile salts and their circulation • Bile salts are produced in the liver and enter the duodenum • Most of the bile salts are reabsorbed in the lower part of the small intestine • These bile salts are returned to the liver in the blood intestine liver (Stored in gall bladder) then through bile duct 3 (a) Describe the route by which bile salts produced in the liver enter the duodenum. (1 mark)

Poisonous mushrooms Bile salts and their circulation • Bile salts are produced in the liver and enter the duodenum • Most of the bile salts are reabsorbed in the lower part of the small intestine liver Hepatic portal vein • These bile salts are returned to the liver in the blood 3 (b) Name the blood vessel through which bile salts are returned to the liver. (1 mark) intestine

Poisonous mushrooms 4 There is a delay of 2– 6 days between eating fungi containing -amanitin and the development of symptoms associated with liver damage. (a) Explain why this delay might suggest that it would be inappropriate to treat patients showing symptoms with substances that remove poisons from the gut. (2 marks) • Takes less than 2 days/short time for substances in gut to be absorbed; • Will pass out as faeces; • So would not expect any -amanitin to still be in gut

Poisonous mushrooms (b) In spite of this delay, patients are often given oral doses of activated charcoal. Activated charcoal absorbs poisonous substances in the gut which are then safely removed from the body in faeces. Use information provided in this question to explain why giving activated charcoal might still be a useful treatment for a person who has eaten fungi containing -amanitin. (2 marks) • -amanitin is recycled/passes back into the gut; • Activated charcoal may remove the -amanitin that re-enters the gut; • So would not reach such high concentrations in the liver;

Poisonous mushrooms Getting into liver cells Concentration of amanitin/µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0

Poisonous mushrooms Make sure that you understand the data Read the stem It is suggested that -amanitin enters cells by facilitated diffusion, making use of the same transport protein as bile salts. Scientists investigated factors affecting the rate of uptake of -amanitin through liver cell membranes. In the first experiment they looked at the effect of the concentration of -amanitin on its rate of uptake. Their results are shown in the table.

Poisonous mushrooms Check the table headings in the stem Concentration should be clear enough Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0

Poisonous mushrooms Check the table headings in the stem This is rate of uptake, not the total amount of -amanitin taken up Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0

Poisonous mushrooms Make sure that you know what the table as a whole is telling you Put the information in this box into words Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0

Poisonous mushrooms Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0 5 (a) Describe the effect of -amanitin concentration on its uptake by liver cell membranes. (2 marks)

Poisonous mushrooms Describe Follow these guidelines • Look for the overall trend or pattern Sometimes it helps to sketch a simple graph • Describe this in terms of the column headings • Quote values where they peak or the gradient changes and 2 marks are guaranteed.

Poisonous mushrooms Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0 5 (a) Describe the effect of -amanitin concentration on its uptake by liver cell membranes. (2 marks) The rate of uptake increases and then levels out (as the concentration of -amanitin increases); Between 400 and 600 µmol dm– 3;

Poisonous mushrooms Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0 (b) Explain the change in the rate of uptake at concentrations of -amanitin between 400 and 800 µmol dm– 3. (2 marks)

Poisonous mushrooms Explain Follow these guidelines: • Explain means ‘Give a reason why’. A description, however good, will not gain marks. • Start your answer with the word ‘Because’. • If you are asked to use a table, or a graph or diagram, make sure you do. • It is a good idea to include a phrase such as ‘in the table’ or ‘the graph shows’. This will show your examiner that you are using the relevant information. • Describe this in terms of the column headings. • Quote values where they peak or the gradient changes. If you do all this, 2 marks are guaranteed.

Poisonous mushrooms Concentration of -amanitin/ µmol dm– 3 Rate of uptake of -amanitin/ µmol min– 1 mg– 1 protein 50 1. 0 100 2. 2 150 3. 0 200 3. 8 400 4. 4 600 5. 0 800 5. 0 (b) Explain the change in the rate of uptake at concentrations of -amanitin between 400 and 800 µmol dm– 3. (2 marks) Because -amanitin is taken up by facilitated diffusion; At concentrations above 400 µmol dm– 3 the carriers are saturated with -amanitin;

Poisonous mushrooms Rate of uptake of amanitin/ µmol min– 1 mg– 1 protein Getting into liver cells 800 Don’t forget • Stem • Axes • Graph as a whole 600 Amanitin only 400 200 Amanitin + bile salts 0 0 30 60 90 120 Time/s

Poisonous mushrooms Rate of uptake of amanitin / µmol min– 1 mg– 1 protein Getting into liver cells 800 600 400 200 0 6 (a) Explain why the units for -amanitin uptake are given per gram of protein. (2 marks) (b) Explain how the results shown in the graph support the Amanitin only suggestion that -amanitin enters cells by facilitated diffusion, making use of the same transport Amanitin + bile salts protein as bile salts. (2 marks) 0 30 60 90 120 Time/s

Poisonous mushrooms 6 (a) Explain why the units for -amanitin uptake are given per gram of protein. (2 marks) Because this allows the results to be compared; As uptake depends on the number of carrier proteins present/ the number of carrier proteins may vary from membrane to membrane; 6 (b) Explain how the results shown in the graph support the suggestion that -amanitin enters cells by facilitated diffusion, making use of the same transport protein as bile salts. (2 marks) Because the graph shows that the rate of uptake is lower when bile salts are present; -amanitin and bile salts are competing for the same transport protein;

Poisonous mushrooms 6 (c) The fetus is not harmed if a pregnant women eats fungi containing -amanitin. Suggest why the fetus is not poisoned by -amanitin. (2 marks) This question requires you to apply knowledge to a new situation. • The question will be based on information you should know. • You will be given all other information you need. -amanitin cannot pass through the placental membranes; No -amanitin/bile salt carrier proteins present; All you needed to know was that substances reach a developing fetus by way of the placenta.

Poisonous mushrooms Bringing it all together Molecules Protein structure Ecology Poisonous mushrooms Genes and genetics Protein synthesis Cells Facilitated diffusion Physiological systems The gut and digestion