Revision for F214 exam

Lessons until 25th January

4th – 7th Jan – revise excretion, photosynthesis, homeostasis, hormones and nerves

11th – 14th Jan – revise respiration and improve practical skills + mock exam

18th – 21st Jan – go over exam paper + practice exam questions

Checking your progress

• Do you know all the facts?

• Can you link topics including AS material?

• Do you follow the question instructions? E.g. state, explain, suggest, compare, calculate, read a passage, use information from graphs

Excretion Explain why excretion is necessary in all

living organisms

3 marks

Explain why excretion is necessary

• Excretion is the removal of metabolic waste from the body (compare with egestion)

• Metabolic wastes are by-products of normal cell processes i.e. they are molecules made by reactions in cells

• Metabolic wastes are toxic if allowed to accumulate.

e.g. carbon dioxide from respiration excreted by lungse.g. waste containing nitrogen such as urea excreted by kidneys

Liver structure and function1) Basic knowledge

a) State how urea is formedb) Explain why fish do not produce ureac) Draw and label a transverse section of a liver lobuled) Describe and explain the flow of blood through a liver lobulee) Describe the role of the liver in detoxification of molecules other than excess amino acids

2) How could these topics be linked with the liver?a) protein structureb) cell structurec) respirationd) homeostasise) blood glucose concentration

Ornithine cycle to convert ammonia into urea

Liver blood supply and internal structure

Internal structure of the liver

Histology of Liver Lobulescentral vein = intra-lobular vein or branch of hepatic

vein.

You shouldrecognise these tissues.

Detoxification of alcohol

ethanol ethanal ethanoic acid

NAD removes hydrogen atoms and carries them to the mitochondrion

enzyme = dehydrogenase

Ethanoic acid enters mitochondrion (Kreb’s cycle in the matrix)

Describe the features which show this hepatocyte is

a very active, absorbing and secreting cell

the control of blood glucose

Homeostasis – maintaining the internal environment stable within certain limits by negative feedback

Negative feedback - a change produces a response which eliminates the change;

this needs a receptor which detects a stimulus, an effector which responds and communication between them e.g. nerves or

hormones

Diabetes – homeostasis is not working for blood glucose concentration

Kidney structure and function 1) Basic knowledgea) Draw and label a nephron to show its position in the

kidney and the function of each part.b) Explain the role of podocytes in ultrafiltration.c) Explain why selective reabsorption is needed and how

it happensd) Explain how the kidney medulla carries out

osmoregulatione) State 2 ways of treating kidney failuref) Describe 3 reasons for taking a urine sample.

2) How does this link with AS work on cell structure, cell membranes and the immune reaction? And with A2 work on respiration and homeostasis?

Kidney Structure

Dialyser

Why do blood and dialysis fluid flow in opposite directions?

What would you put in dialysis fluid and

why?

• Why is heparin added to the blood?• Why are air bubbles removed?• Why is temp. maintained at 37°C?

Kidney Tranplants

• http://www.youtube.com/watch?v=k6d7uX8eH7g&NR=1

• http://www.kidneypatientguide.org.uk/site/TRAanim.php

Pregnancy Testing for human chorionic gonadotrophin (hCG)

Testing for Anabolic Steroids.

A urine sample is tested via gas chromatography or mass

spectrometry.• Each vaporised substance is dissolved in gas and

passed down a tube.• Each substance remains dissolved for a specific

retention time and is then absorbed at the point it has reached in the tube and can be matched against standards.

Homeostasis • Maintaining a stable internal

environment in the tissue fluid around cells

• e.g. temperature, glucose concentration, water

• Fluctuations within narrow limits through negative feedback

• Needs a receptor to detect the change and an effector to eliminate the change and information between the two

Can you explain this?

Humans produce a lower volume of more concentrated urine when the weather is hot or they have been

exercising.

Change in urine concentration and volume

• Sweat loss of water via skin evaporation removes heat from blood (control of body temperature)

• Water content of blood lower / lower water potential• Osmoreceptors in hypothalamus stimulated• ADH released into blood• ADH binds with complementary receptors in

membranes of cells in wall of collecting duct• Active phosphorylase enzymes• Protein channels in cell membranes increase• Water moves by osmosis down a water potential

gradient from collecting duct of nephron to medulla and then into blood in capillaries

• Urine has lower volume and higher concentration• Blood concentration / water potential returns to normal• Example of homeostasis and negative feedback