Welcome back to A2 BIOLOGY!

F214Here we come!

Remaining A2 course consists of:

• F214 - Communication, Homeostasis and Energy – 1 hour 15 mins exam, 60 (90 ums) marks.

• F216 – Practical Skills – 40 (60 ums) marks.

F214 – June exam – calendar to come

1. Excretion – liver and kidneys – Quantitative Assessment

2. Photosynthesis – Qualitative Assessment3. Need for Communication and

Homeostasis4. Hormones5. Nerves6. Respiration

12 weeks to cover it + practicals in

AIMS• Define the term excretion.

• Explain the importance of removing metabolic wastes from the body, including carbon dioxide and nitrogenous waste.

• Describe the histology and gross structure of the liver.

• Homework – Complete pages 6, 7, 9 + 10 in booklet for tomorrow.

A2 Excretion – what is being excreted from these organs?

• Excretion is the removal of metabolic waste from the body.

• Metabolic wastes are by-products of normal cell processes.

• Metabolic wastes are toxic if allowed to accumulate.

• (2 or 3 marks)(See page 2)

So, what is secretion? (p 2)

• Release into the body of...?

• These useful cell products are still produced by................

• Endocrine glands secrete.........?

• Exocrine glands secrete............?

Define the term excretion on your own paper – 2 marks.• Excretion = __________________________ ____________________________________

• Metabolic waste = __________________ ________________________________

• Now for the detail concerning carbon dioxide and nitrogenous waste – prepare for a market place on your assigned topic and then take your own notes when being taught by another student.

(Either) Carbon dioxide…….Prepare for a

market place! Flow chart the story of 1. how carbon dioxide travels from 2. where it is produced, to 3. where it is excreted from the

body.

• Include the detail of transport in the blood on page 37 A2 text book

(or………..)

Nitrogenous compounds……prepare for a market place! (p.

36/37) Flow chart the story of:1. how excess amino acids are deaminated

(key definition) in the liver,2. how the toxic and soluble ammonia is

converted to less soluble and less toxic urea,

3. how urea reaches the kidney, and4. what happens to the remaining “keto

acid” (left over from the deamination of an amino acid). (or…………….)

Why must these substances be removed? Prepare for a market

place….. Produce a diagram which explains:

1. The 3 main effects of toxic carbon dioxide,

2. The symptoms of respiratory acidosis.

3. Why excess amino acids are deaminated rather than being excreted.

Five minutes to go!Can you finish before the jar fills up with marbles?

Time’s up!

Time to move with in your groups of 3 pairs!

• One person in each pair is the mover (A).

• All the movers move to the next pair.• Now the person who has stayed still

(B) teaches the incomer (A) the story and they take notes.

• Next B moves to rejoin their partner (A) and is taught the new info and so on.

• Four moves should do it!

Toxic uric acid (another nitrogenous waste product) can

cause Gout!

• Creatinine is another nitrogenous waste product in urine.

True or False?• Excretion is the removal of undigested

food by the process of defecation.• Urea is produced in the liver from

excess amino acids.• Deamination requires oxygen and

produces a keto acid + carbon dioxide.• Urea is formed from ammonia +

water.• Keto acids are respired or stored as

fats or carbohydrates.• Excess carbon dioxide can cause

respiratory acidosis.

• Blood proteins can act as buffers, soaking up hydrogen ions to prevent acidosis.

• Blood pH below 7.35 results in tremor, confusion and fast breathing rate.

• Carbaminohaemoglobin has a higher affinity for oxygen than haemoglobin.

• Carbonic anhydrase produces carbonic acid which dissociates into hydrogen ions and hydrogen carbonate ions.

AIM – to describe the histology and gross structure of the liver.

Liver and its blood vessels and bile duct.

• Why are the hepatocytes of the liver supplied with blood from two sources? (See page 4)

Histology of Liver Lobules – central = intra-lobular vein or branch of hepatic vein.

See page38 andbookletpages 4 + 5

• 2 of these tissue types you should be able to recognise and label.

The third is kidney.

A

B

C

123

45

Can you add labels?

A

B

C

Liver Structure

• http://www.siumed.edu/~dking2/erg/GI159b.htm

• http://www.nottingham.ac.uk/nursing/sonet/rlos/bioproc/liveranatomy/4.html

Section of lobule – can you see a label mistake?! Now make a 3D model

INTRALOBULAR

Describe the features which show this

hepatocyte is a very active, absorbing cell.

HomeworkCheck!

AIM – Investigate the liver as an organ of excretion and detoxification.

• Check homework• Production of urea (ornithine cycle).• Production of bilirubin, excreted in bile.• Detoxification, especially of alcohol.• Histology and gross structure of Kidney –

dissection.

• Homework - Make revision notes or memory map on excretion and liver.

• Complete pages 13, 14, 15, 16 and 17.• Test question on Wednesday.

Describe the histology of the liver (homework check p 7)

Up to 100,000 lobules each 1-2 mm in diameter.Check answers to questions on page 5

• Complete the right hand column of the table, found on page 7.

Feature What they are and their function

Hepatocyte

Sinusoid

Bile canaliculus

Kupffer cells

Intralobular vessel

/ Branch of hepatic vein

Küpffer cells open up old red blood cells to release h_______ for recycling.

• The ____ ions are stored in the liver. The haem is broken into bilirubin + biliverdin for excretion into the _____ and then faeces.

Functions of the Liver

• http://www.nottingham.ac.uk/nursing/sonet/rlos/bioproc/liverphysiology/7.html

• Protein Metabolism includes i) deamination and

ii) urea production via the ornithine cycle (in cytosol and mitochondria)

• See page 8 Excretion booklet and page 40 in the book.

Production of Urea in the Liver. Quiz on white boards.

• Define Deamination.• When and why are amino acids deaminated?• Name two raw materials needed for the Ornithine

Cycle.• Name two products of the Ornithine Cycle.• Link the following key words into the correct

equations: amino acid / ammonia / urea / keto acid /

carbon dioxide / water / oxygen / ammonia

amino acid + oxygen keto acid + ammonia

ammonia + carbon dioxide urea + water

Detoxification in the liver can be of internally or externally gained substances such as…..

What is keydefinition?

Toxins can be rendered harmless in the liver by… (page 11 – include hydrogen

peroxide)

• Oxidation -

• Reduction -

• Methylation - replacing an H with a CH3.

• Combination with a harmless molecule.

Drugs

• http://www.youtube.com/watch?v=mEFPdNv2Ddk

• (Drugs make you ugly)If alcohol was discovered today, it

would be classified as a class A drug.http://www.youtube.com/watch?

v=1a687tDtwykLet’s check your quizzes page 9 + 10

Detoxification of Alcohol• After our introduction (p11), using

your text books, page 41, answer the questions on page 12 of your booklet.

Kidney structure• Once you have labelled your diagrams,

page 18, watch how to dissect a sheep’s kidney before carefully doing it yourself, (1 between 4!) identifying the regions as you do so.

• Now use a scalpel to scrape some tissue from the cortex region, smear it into a small drop of water on a slide, and add a cover slip. Can you see glomeruli and convoluted tubules from the nephrons?

Starter - Let’s check page 11, 12, 13, 14, 15, 16 and 17 before the 9 min

test……..!

9 min test on excretion and liver structureand function.

Question 4 page 55

• AIMS - Describe with the aid of diagrams and photographs, the detailed structure of a nephron and its associated blood vessels.

• Describe and explain the production of urine, with reference to the processes of ultrafiltration and selective reabsorption.

• Homework – page 39, question 2.

Kidney Structure – page 18http://www.kscience.co.uk/animations/kidney.htm

AIMS

1. Make class plasticine model of nephron and check labels page 19.

2. Ultrafiltration in the Bowman’s Capsule, page 20/21.

3. Selective reabsorption in the PCT.

Proximal ConvolutedTubule

Bowman’s Capsule

Glomerulus

Distal Convoluted Tubule

What is different whenyou compare 2 and 3?

Look how thick the PCT cells are.

Glomerulus and Bowman’s Capsule

http://www.kscience.co.uk/animations/kidney.htm

Complete pages 20 -21

Come and label this transverse section.

A

B

What is this?! Where are you looking from?

Who can show us where the capillaries are buried?

Can you make out the capillaries here too?

Reabsorption in the Proximal Convoluted Tubule. Group work –

design a PCT cell.1. Think of factors about a membrane

which enables it to absorb substances efficiently.

2. Which types of transport are involved as substances move across the membrane?

3. Which organelles may be involved in some way with transport across membranes?

Five minutes to go!Can you finish before the jar fills up with marbles?

Time’s up!

What makes PCT cells function so effectively?

http://www.kscience.co.uk/animations/kidney.htm

• Now copy onto page 22 my PCT cell on next slide, showing how it reabsorbs sodium ions, glucose or amino acids and water from the filtrate.

• Learn stages 1 – 6 by heart.

Starter – put cut out statements re nephron function into the correct order

• AIMS – Give back test question.

• Osmoregulation in the Loop of Henle.• How osmoregulation is controlled. • Distal Convoluted Tubule.• Kidney failure and Urine testing.• Homework – Revision map etc of how nephron

produces urine. I want to see them! Complete revision pages 28 – 29 and answer exam

questions on page 30, and 37 - 43.

• Excretion Test on Wednesday 22nd Feb + preparation for assessed practical.

• Qualitative Practical on Thursday 23rd.

Loop of Henle – see page 23 The U shaped tubuleis called a hairpincountercurrentmultiplier!

What do you think thatname means?

The longer the loop, the more _______ can be reabsorbed.

Osmoregulation and the Loop of Henle

Osmoregulation is the regulation of the water __________ of the blood and tissue fluid.

AIM of Loop of Henle:–

To create a very LOW water potential in the tissue fluid surrounding the loop and collecting duct, i.e. in the medulla.

It consists of i) a descending and ii) an ascending limb.

HOW?

• By actively transporting chloride and sodium ions, out of the ascending limb into the tissue fluid of the medulla.

• These ions ________ the water potential of the tissue fluid.

• The ascending limb is impermeable to water, so water can not follow from the loop by ______.

WHY?

To prevent too much water loss via the urine.

The mechanism works as follows:-Water channels in the membranes of the

collecting duct cells are open.Water diffuses out of the collecting ducts,

_______ the water potential gradient, into the medulla, and then on into blood capillaries.

This lowers the amount of water leaving the collecting duct in the urine.

Meanwhile some of the chloride and sodium ions in the tissue fluid of the medulla diffuse back into the descending limb and so are re-cycled!

BRILLIANT!Now check Fig 52 page 47 in book and complete pages

24 – 25.

Osmoregulation is the control of ______ and ____ levels in the body. (p48)

Water is gained from 3 sources……

Water is lost in………

Osmoregulation Aim (page 26)

• Explain, using water potential terminology, the control of water content of the blood.

• What is the role of the kidney?

• What are the roles of i) osmoreceptors in the hypothalamus and ii) the posterior pituitary gland?

• http://www.kscience.co.uk/animations/kidney.htm

Antidiuretic Hormone (ADH)

(see kidney animation and go through diagram)• (page 48, book and 26 in booklet)• Where is ADH produced?• How does it reach the posterior

pituitary gland?• How is the release of ADH stimulated?• Where precisely are ADH receptors?• How do ADH receptors cause more

water to be reabsorbed?• What is ADH’s half-life?• Explain the negative feedback system.

How is DEHYDRATION prevented?

Use page 26 of the booklet, page 48,49 of the book and these key words to explain.

hypothalamus osmoreceptor ADH

posterior pituitary gland receptorscollecting duct enzyme

vesicleswater-permeable channels

negative feedback

Distal Convoluted Tubule

• Regulates the concentration of ions in the blood.

• E.g. sodium is pumped out of the tubule but potassium is pumped back in. However the rates can be varied and therefore regulated.

True or False?• Reabsorption of water by osmosis in the

presence of ADH is called ultrafiltration.• The basement membrane is the filter in the

Bowman’s capsule.• Podocytes are fenestrated.• The afferent arteriole is narrower than the

efferent arteriole.• Selective reabsorption occurs in the PCT.• Sodium diffuses from the filtrate into the

PCT cell via cotransporter transporter proteins, bringing in water at the same time.

• Microvilli on the surface of PCT cells, provide a larger surface area for reabsorption across from the filtrate to the capillary.

• Osmoregulation occurs in the loop of Henle.• Sodium and Chloride ions move by osmosis

out of the ascending limb into the tissue fluid of the cortex.

• When the blood’s water potential is low, receptors in the pituitary gland release ADH.

• ADH causes movement of water channels to the walls of the collecting duct.

Kidney Failure and Urine Testing. AIMS

1. Outline the problems caused by kidney failure.

2. Discuss the use of renal dialysis and transplants for treatment.

3. Describe how urine samples can be used to test for pregnancy and misuse of anabolic steroids.

4. Turn to page 40

Kidney failure can be caused by:

1. Hypertension - ……how?

2. Infection - …………..how?

3. Diabetes mellitus – ____ glucose levels cause i) leaky glomeruli, followed by ii) cross linked proteins in the membranes of glomeruli causing scarring, which does not filter blood.

• Why do patients feel so ill?

Treatment - dialysis

• http://www.youtube.com/watch?v=x_ra9YUX9fk&feature=related

• Now for the detail of haemo and peritoneal dialysis.

• http://www.youtube.com/watch?v=i6bctm7I3l4&feature=related (use pause button when needed)

• http://www.biotopics.co.uk/human2/andial.html

Dialyser

Pair and Share Describe the flow of blood

and dyalys and dialysis fluid.

Why do they flow in opposite directions?

What would you put in dialysis fluid and why? http://www.biotopics.co.uk/human2/andial.html

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

• Now complete questions on page 41, 42 in booklet.

You might be asked to outline the procedure of kidney

dialysis……• Key words – shunt between artery

and vein / arterial blood / pump / 37ºC / selectively permeable / counter current / heparin / filter for air bubbles.

Kidney Transplants

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

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

Advantages and Disadvantages – sort them!

• Need major surgery under general anaesthetic.• Diet is less limited.• Feel physically better.• Frequent checks for kidney rejection signs.• Better quality of life – able to travel.• Need immunosuppressants for life of kidney so

increased risk of infection.• Freedom from time consuming dialysis.• Surgery risks include infection and bleeding.• No longer seen as chronically ill.• Anti-rejection drugs cause fluid retention and high

blood pressure.

Testing urine samples.• Pair and Share – Substances with a

relative molecular mass of less than 69,000 can leave the glomerulus and enter the Bowman’s Capsule of a nephron.

• Note down two facts which must be true of a substance which can be detected in urine.

Pregnancy Testing for human chorionic gonadotrophin (hCG) You will need

plasticine and a wooden board.• Split into 3 groups of 4 (pregnant) or 3 of 3 (not pregnant)• 1 student makes 4 plasticine hCG antibodies with blue bead, 1 makes 2 immobilised antibodies, 1 makes 2 control line antibodies and for the positive test group, one makes 4 hCG molecules.• Explain to us!

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.

Tests within UK Sport, latest news

• http://www.uksport.gov.uk/news/business_as_usual_for_testing_programme/

• What could cause an incorrect result?• Hints – nandrolone is natural. Nightnurse?

Now complete page 44

Aims• Recap – Write a flow diagram or bullet

points outlining haemodialysis – 10 mins.• Key words – shunt between artery and vein /

arterial blood / pump / 37ºC / selectively permeable / counter current / heparin / filter for air bubbles.

• To go through the graph questions page 30.• Outline the procedure for a kidney

transplant. • Homework – research how a pregnancy test

using monoclonal antibodies works.

Mark Scheme Exam Question 1• a) removal of metabolic waste from body; by-products from normal cell processes;

• b) protein; nucleic acids; (macromolecules)

• c) i) Difference x 100 = 12.5 x 100 = 568% original 2.2

• ii) Excess protein digested into amino acids;

amino acids deaminated into keto acid + ammonia; ammonia converted into urea;

• d) ammonia is toxic and soluble; urea is less toxic and soluble;• e) glucose – glucose enters filtrate at BC

but is reabsorbed by PCT so none is in urine;

not all reabsorbed glucose reaches blood again (renal vein), as some is used up in PCT cells to release energy;

urea – urea is filtered into the BC from the blood;

some is still found in renal vein because not all plasma enters BC;

although some urea is reabsorbed in the PCT, most continues to the collecting duct (and is concentrated by water reabsorbtion);

• Question 2• a) Glucose is reabsorbed in the PCT; along with sodium ions via cotransporter

transporter proteins;• b) urea is concentrated in urine by water

reabsorption;• c) hypothalamus stimulates (posterior)

pituitary to secrete ADH; ADH stimulates more water channels to

allow water reabsorption from collecting ducts;

• d) hot days cause sweating of salts via skin so fewer left to be lost via urine;