9.2.3

• Plants and animals regulate the concentration of gases, water and waste products of metabolism in cells and interstitial fluid

• TEXTBOOK – Chapter 3; Pg. 70 - 102

Friday 23rd November

• AIM – To be able to explain why the concentration of water in cells should be maintained within a narrow range AND why the removal of wastes (excretion) is essential

• REF – TEXT Pg. 70 – 72, KISS Pg. 24-25

Excretion - DEFINITION• Process by which substances formed during body

reactions (cellular activity) are removed from the body• Excretion may occur via:– the kidneys – urination– the lungs – removal of CO2

– skin – sweating (water & salts)– and large intestine – excretion of bile pigments

• NB - normal passing of undigested substances is NOT excretion because they are not products of metabolism, instead = defaecation

Diffusion

Smell Particles & Air Particles

Solution

Smell Particles diffused evenly into the Air Particles

Diffusion is the passive movement of particles from a high concentration of particles to a lower

concentration until they are spread out evenly

Diffusion

• This is similar to what happens when you dissolve sugar or coffee granules in water ....

Sugar Particles & Water Particles

Sugar particles diffused into water Particles = solution

Solute

Solvent

Solution

Diffusion Notes

• Diffusion does not require energy – it’s passive

• Diffusion depends on the random movement of particles.

Solutions

• A solution is made up of two parts: the solute and the solvent.

• The solute dissolves in the solvent• Before a gas can diffuse across a membrane it

must dissolve into a liquid.

Diffusion & Gas Exchange• Animal cells use oxygen, so oxygen is less concentrated

inside the cell than outside. This causes oxygen to diffuse into the cell

• Carbon dioxide is produced in an animal cell, so it is more concentrated inside than outside – so it diffuses out of the cell

Diffusion for Photosynthesis

• Diffusion of gases also happens in leaves:

• For photosynthesis to happen Carbon Dioxide has to get inside the leaves. It diffuses in through stomata

• Water vapour and oxygen diffuse out of the leaf at the same time

Water + Carbon Dioxide → Oxygen and Glucose (& a little water)

Diffusion & Photosynthesis

CO2 O2

Rate of Diffusion

• The rate of diffusion depends on:• Size of the particles: smaller = faster• Temperature (eg. kinetic energy): hotter = faster• The concentration gradient: the higher it is =

faster the rate.• State of the particles: gas > liquid > solid• Distance - thickness of the exchange surface:

thinner = faster• Surface area available: larger = faster

Facilitated Diffusion

• Transport proteins carry specific molecules across the cell membrane

• Movement is along a concentration gradient (i.e. From higher to lower)

• Each type of transport protein will carry only one type of molecule.

• This is how glucose is moved.

Facilitative Diffusion

Facilitated DiffusionGlucoseTransport protein

Concentrationgradient

Facilitative Diffusion

Facilitated DiffusionFacilitative Diffusion

Investigating the importance of Surface Area for Cells

• Raw materials enter a cell by diffusion via the cell membrane. The number of molecules which diffuse into a cell depends on its surface area. To function efficiently a cell needs a large surface area relative to its volume

Aim for Today

• Biological importance of osmosis

Osmosis Defintion

• Osmosis is a special type of diffusion. • Osmosis is the diffusion of water.

Osmosis is the movement of water molecules from a high concentration

of water to a low concentration of water through a semi-permeable

membrane

Osmosis

Osmosis

Osmosis Experiment

1. Fill the partially permeable membrane with strong sugar solution

2. Tie it to a capillary tube and stand it in a weak sugar solution

3. Use your ideas about osmosis to explain why the liquid rises in the tube

Glass tube Level of sugar solution

Weak sugar solution

Visking Tubing with Strong Sugar solution

Osmosis in Potato Cells

1. Cut three potato chips to exactly the same size. Measure their length and write it down.

2. Label and Set up the following test-tubesa) Distilled waterb) Weak sugar solutionc) Strong sugar solution

3. Place one chip in each test-tube and leave it for 30 minutes

4. Re-measure each chip

Questions: Osmosis in Potato Cells

1. Which chip has increased in size? Write a sentence to explained what has happened in relation to osmosis.

2. Which chip has got shorter? Use your knowledge of osmosis to explain this.

3. Feel the chip that was in test-tube A. Why does it feel firm?

Osmosis and Cells - Notes

• Cells are surrounded by a cell membrane that separates the contents of the cell from the outside environment. The cell membrane has tiny holes in it. This allows small molecules to pass through, but not large ones. The cell membrane is partially-permeable.

• Osmosis occurs when two solutions are separated by a partially permeable membrane

Class Activity: Correctly LabelWeak Solution

Strong Solution

Solute Molecule

Water Molecule

Partially Permeable Membrane

Which way will the water flow???

Osmosis

Types of Solutions

• Isotonic – when both solutions have the same concentration

of dissolved substances• Hypotonic– A solution with a lower concentration of dissolved

substances (ie. More water cf. solutes)• Hypertonic– A solution with a higher concentration of

dissolved substances (ie. More solute cf. water)

Osmosis & Animal Cells

haemolysis

Hypotonic solution

Hypertonic solution

Osmosis & Plant Cells

Turgid Cell Plasmolysed Cell

Hypotonic solution Hypertonic

solution

Cells in distilled waterWhat type of solution?

Cells in a salt solutionWhat type of solution?

Water in

Cells eventuallyexplode

Water out

Cells shrivel &die

Osmosis

Hypotonic Hypertonic

Plasmolysis in Elodea

Plasmolysis in Elodea: http://www.mrphome.net/mrp/Membrane_Transport.html

Osmosis & pH

• Can you relate CO2 concentration and the need for water balance to maintain pH, and therefore homeostasis?

• REF – Text book Pg. 72, KISS Pg. 25

The importance of the removal of wastes

• Accumulation of wastes may be toxic to cells and so metabolic wastes and so must be excreted as soon as possible. – Nitrogenous Wastes (contain Nitrogen)• Ammonia – increases pH• Uric Acid – birds, reptiles, insects• Urea – mammals, amphibians

– Carbon dioxide• Changes to acidity affect the optimal functioning of

enzymes.

HOMEWORK

• Read Reference Pages:– Text Pg. 70-72– Kiss Pg. 24-25

• Complete worksheet 11 KISS booklet

DATE

• Aim – To be able to explain why diffusion & osmosis are inadequate in removing nitrogenous wastes in some organisms AND Identify the role of the kidney in the excretory system of fish and mammals

• REF – Text Pg. 72-74, 76, KISS Pg.

Problems with Diffusion & Osmosis

• They are PASSIVE transport and are therefore, SLOW

• They rely on a concentration gradient and therefore reach EQUILIBRIUM & so not all wastes would be removed

• Osmosis may cause TOO MUCH water to be lost in urine

• THEREFORE ACTIVE TRANSPORT IS ALSO REQUIRED TO ENSURE ADEQUATE HOMEOSTASIS

The Kidneys & Homeostasis

• The kidneys are part of the body’s excretory system

• The kidneys basically act as filters to “clean” the blood

• They perform three main roles:1. Remove urea from the blood2. Adjustment of ions (salts) in the blood3. Adjustment of water content in the blood

Kidney: Structure

• Kidneys are located on the dorsal wall of the body and have fat stored around them.

1. Removal of Urea

• Urea is produced in the liver.• Proteins can NOT be stored by the body so

excess amino acids are broken down by the liver – this is called deamination

• The waste product is urea, which is passed into the blood to be filtered out by the kidneys. Urea is also lost partly in sweat.

• Urea is poisonous and must be excreted.

2. Adjustment of Ion content

• Ions such as sodium are taken into the body in food, then absorbed into the blood.

• Excess ions (salts) are removed by the kidneys.• Some ions are also lost in sweat (which tastes

salty).• The important thing to remember is that the

balance of ions is maintained by the kidneys = homeostasis

3. Adjustment of water content• The hypothalamus in the brain monitors the water

content of the blood and instructs the pituitary gland to release the hormone ADH (Anti-diuretic hormone) into the blood accordingly:

Too little water in blood:1. Hypothalamus detects &

Pituitary releases ADH2. More ADH enters kidney -

more water is reaborbed3. So less urine which is more

concentrated is produced

Too much water in blood:1. Hypothalamus detects &

Pituitary releases LESS ADH2. Less ADH enters kidney - less

water is reaborbed3. So more urine which is less

concentrated is produced

Too much water

Too little water

The Nephron

• Nephrons are the filtration units in the kidneys:

The Nephron

1. Ultrafiltration at the Bowman’s Capsule – high pressure squeezes water, urea, ions & glucose out of blood (big molecules eg. Proteins stay in the blood).

2. Reabsorption along the nephron – all sugar & sufficient ions are actively reabsorbed. Sufficient water is reabsorbed according to the level of the hormone ADH.

3. Secretion – excess ions and chemicals such as drugs are excreted into nephron

4. Release of wastes as urine - urea, excess ions and water are not reabsorbed and pass from the collecting duct to the ureter to be excreted as urine.

Do Now – Label the Diagram

a

The Nephron

• Nephrons are the filtration units in the kidneys:

Thursday 29th November

• Aim – To explain how filtration and reabsorption in the nephron regulate body fluid composition AND

• Distinguish between active & passive transport and relate these to process occuring in the kidney

• REF – Text Pg. 74 – 75, 78 – 82, Handouts, Kiss Pg. 26

Active & Passive Transport

• Passive transport limitations– Requires concentration gradient (so max 50%

wastes could be removed this way)– Too slow (toxins would build up = bad)

• Active Transport uses ATP (Energy from respiration)– It moves substances AGAINST a concentration

gradient• Movement of substances between blood & kidney

nephrons involves both passive AND active transport

Passive Transport in Kidney

• Excess water moves by osmosis

• Some urea & ammonia move by diffusion

• See Fig. 3.6 Pg. 81

Active Transport in Kidney

• Salts are moved by ‘sodium pump” by active transport back into bloodstream. The movement of salts, alters the osmotic gradient of blood & so water is drawn into blood passively (Fig. 3.7 Pg. 82 Text)

• ALL Glucose & amino acids are reabsorbed from nephron into bloodstream actively

• Addition nitrogenous wastes & H+ ions are secreted into nephron actively

Urine Production

Tubular Secretion

• Toxic substances are secreted into nephron from the capillaries:

• Active secretion– Uric acid, drugs, hydrogen ions

• Passive secretion– Urea, ammonia

Friday 30th November

• Aim – To be able to outline the role of the hormones aldosterone and ADH in the regulation of water and salt levels in the blood.

• Ref – Pg. 83-84, KISS Pg. 27-28, Handouts

Hormones

• The hormonal system, or endocrine, system helps maintain homeostasis.

• Hormones can affect things like the rate of metabolism, growth and sexual development.

A hormone is a chemical produced by an endocrine gland that travels in the blood

to activate target cells

Hormones

• Can you place the following endorcrine glands?

• Adrenal• Ovaries• Testes• Thyroid• Pituitary• Pancreas

Aldosterone

• Brings about RETENTION of salts in body• Low sodium (salt) levels in blood cause the

adrenal gland to secrete aldosterone• Aldosterone reaches target cells in the kidney

and increases the permeability of nephron to sodium, therefore INCREASES reabsorption of sodium back into capillaries

• Salt levels increase to normal again

Anti-diuretic hormone (ADH)

• Diuretics make you pee more eg. caffeine• Anti-diuretic hormone causes water

reabsorption (conservation) in the body• If blood volume drops, hypothalamus detects

the change & stimulates the pituitary gland to secrete ADH

• ADH acts on the target cells of the kidney to cause greater REABSORPTION of water

3. Adjustment of water content• The hypothalamus in the brain monitors the water

content of the blood and instructs the pituitary gland to release the hormone ADH (Anti-diuretic hormone) into the blood accordingly:

Too little water in blood:1. Hypothalamus detects &

Pituitary releases ADH2. More ADH enters kidney -

more water is reaborbed3. So less urine which is more

concentrated is produced

Too much water in blood:1. Hypothalamus detects &

Pituitary releases LESS ADH2. Less ADH enters kidney - less

water is reaborbed3. So more urine which is less

concentrated is produced

Too much water

Too little water

See Handout & TEXT

1. Back-page of handouts 2. Copy diagram 3.6 (Pg. 84) into your notes

HOMEWORK THIS WEEKEND! HEAPS!!!You have handouts on kidney failure and renal dialysis – READ THESE Read Text Pg. 85-87 and answer the task questions