Name: CEYDA Surname: Eren Course: University of Bath Biology Foundation Topic: Gas exchange Submitted to the Biology Department of the University.

Name: CEYDAName: CEYDA Surname: ErenSurname: Eren Course: University of Bath Biology Foundation Course: University of Bath Biology Foundation

Topic: Gas exchangeTopic: Gas exchange Submitted to the Biology Department of the Submitted to the Biology Department of the

University of Bath.University of Bath. RICHARD LLOPIS-GARCIARICHARD LLOPIS-GARCIA Date: 16/03/2007Date: 16/03/2007

GAS EXCHANGE SURFACESGAS EXCHANGE SURFACES

• Many organisms have developed adaptations that enable them to exchange gases efficiently.

• Insects and plants always have to make a compromise between the need for respiratory gases and problems with water loss.

Gas Exchange Surfaces have FOUR Major Adaptations:

1) They have large surface area to volume ratio.2) They are thin –often they are just one layer of epithelial cells.3) There are short diffusion pathways between the gases and

internal tissues.4) Steep concentration gradients between the tissues where the

gases are absorbed are maintained.

Fick’s Law is used to calculate Fick’s Law is used to calculate Diffusion RatesDiffusion Rates

The rate at which a substance The rate at which a substance diffuses can be worked out using diffuses can be worked out using

Fick’s Law:Fick’s Law:

Rate of diffusion = Rate of diffusion = Surface area Surface area x Difference in concentrationx Difference in concentration

thickness of membranethickness of membrane

Single celled organismSingle celled organism1)1)Protozoa --> Amoeba or Plasmodium (Malaria)Protozoa --> Amoeba or Plasmodium (Malaria)

2) Algal forms --> Chorella2) Algal forms --> Chorella

The body surface of a Protoctist is adapted to its The body surface of a Protoctist is adapted to its EnvironmentEnvironment

1) Protoctist are 1) Protoctist are small organismssmall organisms and they are very and they are very diverse organismdiverse organism. .

2) In this group if the can not fit other group, they will be in this group. 2) In this group if the can not fit other group, they will be in this group. 3) They can behave 3) They can behave like animal (protozoa) and plant (algae).like animal (protozoa) and plant (algae).

4) Protoctist have 4) Protoctist have soft bodiedsoft bodied . .

5) Protoctist are 5) Protoctist are unicellular organismunicellular organism( it means that they are single celled ( it means that they are single celled organisms) .organisms) .

6)Sometimes they are large enough to be seen with naked eye.6)Sometimes they are large enough to be seen with naked eye.7) Sometimes they cause diseases in human such as Malaria and It’s caused 7) Sometimes they cause diseases in human such as Malaria and It’s caused

by infection with a protoctist called by infection with a protoctist called Plasmodium.Plasmodium.8) Anopheles Mosquito carries the protoctist and it is the vector.8) Anopheles Mosquito carries the protoctist and it is the vector.

Kingdom of ProtoctistaKingdom of Protoctista Cell structureCell structure : Eukaryotic, Unicellular, Colonial and Multicellular forms. : Eukaryotic, Unicellular, Colonial and Multicellular forms.

Cell wallCell wall:: Sometimes present. Sometimes present.

NutritionNutrition:: Autotrophic protoctist Autotrophic protoctist Heterotrophic protoctist.Heterotrophic protoctist.

Other notesOther notes:: 60.000 protoctist species are aquatic (aquatic refers to water). 60.000 protoctist species are aquatic (aquatic refers to water). Algae are immobile and they are autotrophic protoctist.Algae are immobile and they are autotrophic protoctist.

AutotrophicAutotrophic means that organisms are capable of synthesising energy from means that organisms are capable of synthesising energy from inorganic material such as plant who obtain their energy from the sun.inorganic material such as plant who obtain their energy from the sun.

Protozoa are heterotrophic protoctist.Protozoa are heterotrophic protoctist.

HeterotrophicHeterotrophic means that the organisms can not synthesize their own food. means that the organisms can not synthesize their own food. Therefore rely on other food sources found within environment (such as Therefore rely on other food sources found within environment (such as Bacteria and Fungi)Bacteria and Fungi)

Protoctist are well adapted to aquatic environments which only contain Protoctist are well adapted to aquatic environments which only contain around 1% oxygenaround 1% oxygen

1) They have all the usual features for efficient gas 1) They have all the usual features for efficient gas exchange = exchange = a a large,large, thin surface thin surface , and , and ability to ability to maintainmaintain high concentration gradients.high concentration gradients.

2) 2) The short diffusion pathwayThe short diffusion pathway in unicellular organism in unicellular organism means that oxygen can take part in means that oxygen can take part in biochemical biochemical reactions reactions asas soon as it has soon as it has diffused diffused into the cell.into the cell.

Therefore, they are small organisms.Therefore, they are small organisms.

There is There is no need for circulatory system.no need for circulatory system. Because Protoctist have Because Protoctist have no need of ventilation.no need of ventilation.

The distance over which Oxygen and Carbon dioxide have The distance over which Oxygen and Carbon dioxide have to travel in these creatures to travel in these creatures are smallare small. So that diffusion . So that diffusion fast fast enoughenough to meet their needs. to meet their needs.

Fish are adapted to live in aquatic EnvironmentFish are adapted to live in aquatic Environment The lungs of mammal and gills of fish both show that the basic The lungs of mammal and gills of fish both show that the basic

requirements of an efficient structure of gaseous exchange.requirements of an efficient structure of gaseous exchange. Both need large surface area.Both need large surface area. The gills achieved this by having The gills achieved this by having

hundreds of filaments, with many branches on each filament.hundreds of filaments, with many branches on each filament. Gill filaments are called Gill filaments are called lamellaelamellae.. The wall of gill lamellae are also made from very The wall of gill lamellae are also made from very thin thin squamous squamous

epitheliumepithelium to minimise the diffusion distance. to minimise the diffusion distance. A A blood systemblood system carries gases between carries gases between the gaseous the gaseous

exchange surfaceexchange surface and the respiring cells and the gills. There is and the respiring cells and the gills. There is a dense network of capillaries which carry blood close to the a dense network of capillaries which carry blood close to the surface of the gill lamellae.surface of the gill lamellae.

At the same time, capillaries enable rapid exchange of oxygen At the same time, capillaries enable rapid exchange of oxygen and carbon dioxide between the blood and the water or air.and carbon dioxide between the blood and the water or air.

Capillaries are separated from the water or air by Capillaries are separated from the water or air by only a thin only a thin epithelium (single layer of cells).epithelium (single layer of cells). So that the diffusion of gases is So that the diffusion of gases is a rapid as possible.a rapid as possible.

Location and the Structure of Fish Location and the Structure of Fish GillsGills

What is counter current system?What is counter current system? Although water molecule contains oxygen, this can not used by Although water molecule contains oxygen, this can not used by

aquatic organism. aquatic organism. Oxygen comes from the atmosphere and is dissolved in the Oxygen comes from the atmosphere and is dissolved in the

water.water. Fish absorb dissolved Oxygen from the water by means of gills.Fish absorb dissolved Oxygen from the water by means of gills. Water constantly flows over the gills and the oxygen diffuses into Water constantly flows over the gills and the oxygen diffuses into

the blood.the blood. That’s because That’s because oxygen is more concentrated in the water than in oxygen is more concentrated in the water than in

the blood inside the capillaries.the blood inside the capillaries. Some of the fastest moving fish have a counter current system Some of the fastest moving fish have a counter current system

where the blood and the water flow in opposite direction.where the blood and the water flow in opposite direction. Advantage of counter current systemAdvantage of counter current system.. It maintains a It maintains a high concentration gradient of high concentration gradient of oxygen oxygen between the between the

water water andand the blood. the blood. It allows It allows 90% of the available oxygen90% of the available oxygen in the water to diffuse into in the water to diffuse into

the blood.the blood. NOTE: if blood and water flowed in the same direction, the blood NOTE: if blood and water flowed in the same direction, the blood

could pick up 50% of the available oxygen, and net diffusion into could pick up 50% of the available oxygen, and net diffusion into the blood would stop at this concentration.the blood would stop at this concentration.

The diagram presents a generic representation of a countercurrent exchange system, with two parallel tubes containing fluid separated by a permeable barrier. The property to be exchanged, whose magnitude is represented by the shading, transfers across the barrier in the direction from greater to lesser according to the second law of thermodynamics. With the two flows moving in opposite directions, the countercurrent exchange system maintain a constant gradient between the two flows over their entire length. With a sufficiently long length and a sufficiently low flow rate this can result in almost all of

the property being transferred.By contrast, in the concurrent (or co-current, parallel) exchange system the two fluid flows are in the same direction. As the diagram shows, a concurrent exchange system has a variable gradient

over the length of the exchanger and is only capable of moving half of the property from one flow to the other, no matter how long the exchanger is. It can't achieve more than 50%, because at that

point, equilibrium is reached, and the gradient declines to zero.

Compare the Gas Exchange System between the fish, mammal, Compare the Gas Exchange System between the fish, mammal, insectsinsectsOrganism-Name of gas exchange-Is there any ventilation?-Is blood Organism-Name of gas exchange-Is there any ventilation?-Is blood involved?involved?

FISH FISH Gills Yes Yes Gills Yes Yes MAMMALMAMMAL Lungs Yes Yes Lungs Yes Yes

Insects Insects Tracheoles Very little No Tracheoles Very little No

Insects use Trachea to Exchange Gases:Insects use Trachea to Exchange Gases:

Insects are active animals and so need a lot of oxygen. The system Insects are active animals and so need a lot of oxygen. The system for gas exchange is different from that of any other group of for gas exchange is different from that of any other group of animals.animals.

Insects have a system of tubes that lead directly from the outside Insects have a system of tubes that lead directly from the outside atmosphere to the working tissues. The tubes called atmosphere to the working tissues. The tubes called ‘‘tracheolestracheoles’.’.

Insect’s deal with gaseous exchange by having microscopic air-Insect’s deal with gaseous exchange by having microscopic air-filled pipes called filled pipes called ‘trachea‘trachea’. Trachea penetrates the whole of the ’. Trachea penetrates the whole of the body from pores on the surface called body from pores on the surface called spiracles. spiracles.

Trachea branch off into smaller trancheolesTrachea branch off into smaller trancheoles

Tracheoles have Tracheoles have thin,permeable wallsthin,permeable walls and go to individual and go to individual cells.cells.

This means that gases are not transported by blood and the This means that gases are not transported by blood and the oxygen diffuses directly into the respiring cells. oxygen diffuses directly into the respiring cells.

Trancheoles must be Trancheoles must be short.short. Because the diffusion need to Because the diffusion need to be slow.That’s why the insects are quite small.be slow.That’s why the insects are quite small.

NO need for circulatory systemNO need for circulatory system. Because insects use . Because insects use rhytmic abdominal movements – to move air in and out of rhytmic abdominal movements – to move air in and out of spiracles.spiracles.

Generally large insects can move the abdomen up and Generally large insects can move the abdomen up and down to pump air in and out.down to pump air in and out.

Plants exchange gases at the surface of the mesophyll Plants exchange gases at the surface of the mesophyll cellscells

Plants do not have special breathing organs.Plants do not have special breathing organs.Because they do not move like animals.Because they do not move like animals.

Plant leaves Plant leaves have large surface areahave large surface area to the air. to the air. Therefore, Oxygen and carbon dioxide through Therefore, Oxygen and carbon dioxide through stomata into the intercellular spaces is fast enough stomata into the intercellular spaces is fast enough for respiration going in their cells by diffusion.for respiration going in their cells by diffusion.

Most plants leaves are Most plants leaves are thinthin,, the distances for the the distances for the diffusion are also very diffusion are also very short.short.

Plants exchange gases during Plants exchange gases during respiration respiration and and photosynthesis. photosynthesis. The main gaseous exchangeThe main gaseous exchange is the is the surface of the mesophyll cells. surface of the mesophyll cells. Mesophyll cells in the Mesophyll cells in the leaves.leaves.

This is well adapted for its function: This is well adapted for its function: So that the plantSo that the plant leaves have large surface area.leaves have large surface area.

Structure of Mesophyll cells in leavesStructure of Mesophyll cells in leaves Upper and lower epidermis in leaves is called Mesophyll. It consists Upper and lower epidermis in leaves is called Mesophyll. It consists

of two zones: of two zones: 1) upper palisade mesophyll1) upper palisade mesophyll 2) lower spongy mesophyll2) lower spongy mesophyll

The palisade cellsThe palisade cells are usually: Long and contain many chloroplasts. are usually: Long and contain many chloroplasts.

The spongy cellsThe spongy cells are : vary in shape and fit loosely together, leaving are : vary in shape and fit loosely together, leaving many spaces between them.many spaces between them.

In daylight, some of the Oxygen produced by photosynthesis is used in In daylight, some of the Oxygen produced by photosynthesis is used in respiration and the carbon dioxide released from respiration is used respiration and the carbon dioxide released from respiration is used in photosynthesis.in photosynthesis.

In darkness, only respiration is going on.( Because there is no light).In darkness, only respiration is going on.( Because there is no light).So carbon dioxide released from passes out of the leaf and oxygen So carbon dioxide released from passes out of the leaf and oxygen

diffuses in.diffuses in. Chemical equation for photosynthesis:Chemical equation for photosynthesis: (SUNLIGHT)(SUNLIGHT)

6CO2 + 6H20 6CO2 + 6H20 --->---> C6H1206 + 602 C6H1206 + 602UPTAKE OF CARBON DIOXE UPTAKE OF WATER (CHLOROPHYLL) PRODUCTION OF SUGAR RELEASE OF OXYGENUPTAKE OF CARBON DIOXE UPTAKE OF WATER (CHLOROPHYLL) PRODUCTION OF SUGAR RELEASE OF OXYGEN

Gases pass back and forth from outside Gases pass back and forth from outside through special minute pores and these pores through special minute pores and these pores are mainly present are mainly present in the lower epidermisin the lower epidermis called called stomata.stomata.

Plants can open and close the stomata, which Plants can open and close the stomata, which helps to helps to minimise water lossminimise water loss whilst allowing whilst allowing photosynthesis to continue.photosynthesis to continue.

The stomata can open to allow exchange of The stomata can open to allow exchange of gases and gases and close close if the if the plant is losing too plant is losing too much water.much water.

Insects and Plants can control water loss:Insects and Plants can control water loss:

The problem with opening like stomata and spiracles are The problem with opening like stomata and spiracles are designed to allow gases in and out is that they can lead to designed to allow gases in and out is that they can lead to water loss. Plants and insect have adapted which prevent water loss. Plants and insect have adapted which prevent dehydrationdehydration..

How does the insect can control water loss?How does the insect can control water loss? Insects haveInsects have muscles muscles that they can use to close their that they can use to close their

spiracles if they are losing too much water.spiracles if they are losing too much water. They also have They also have tiny hairstiny hairs around their spiracles which around their spiracles which

reduce evaporation.reduce evaporation. Insects body covered with an Insects body covered with an exoskeleton exoskeleton made of made of

chitinious cuticlechitinious cuticle. . ExoskeletonExoskeleton is a skeleton covering outside of body chitin is a is a skeleton covering outside of body chitin is a

fairly hard waterproof covering made by the cells of fairly hard waterproof covering made by the cells of epidermis. It protects organs inside and prevents the loss of epidermis. It protects organs inside and prevents the loss of water.water.

How does the plant can control water loss?How does the plant can control water loss? Major environmental factors that cause the loss of water from leaves and Major environmental factors that cause the loss of water from leaves and

affect the transpiration:affect the transpiration:

1.1. Humidity Humidity 2.2. TemperatureTemperature3.3. WindWind4.4. LightLight

In plants, the stomata are usually kept In plants, the stomata are usually kept openopen to allow to allow gaseous exchangegaseous exchange..

During the night, During the night, Proton pumpsProton pumps in the guard cells pump H+ ions out of in the guard cells pump H+ ions out of them. This opens them. This opens potassium channelspotassium channels, allowing K+ ions to enter to the , allowing K+ ions to enter to the guard cells.guard cells.

Potassium concentration in the guard cell vacuoles increase. This lower the Potassium concentration in the guard cell vacuoles increase. This lower the water potential of the cell sap and water enters the guard cell by water potential of the cell sap and water enters the guard cell by osmosis.osmosis.

This inflow of water This inflow of water raises the turgor pressureraises the turgor pressure inside the guard cells. The cell inside the guard cells. The cell wall next to the stomatal pore, is wall next to the stomatal pore, is thickerthicker than elsewhere in the cell and it than elsewhere in the cell and it is able to is able to stretch. stretch.

Although increases turgor tends to expand the whole guard cell, the thicker Although increases turgor tends to expand the whole guard cell, the thicker wall can not expand. This causes the guard cells to curve in such a way wall can not expand. This causes the guard cells to curve in such a way that the that the stomatal pore between them is opened.stomatal pore between them is opened.

What is transpiration?What is transpiration? Process of evaporative water loss in plants is called Process of evaporative water loss in plants is called

Transpiration.Transpiration. This essentially has happened by This essentially has happened by different osmotic different osmotic

pressure between the air and the leaves of plant.pressure between the air and the leaves of plant.

If osmotic pressure of If osmotic pressure of air is biggerair is bigger than the osmotic than the osmotic pressure pressure within leaves.within leaves.

Transpiration:Transpiration: %90 of water “absorbed” by roots lost %90 of water “absorbed” by roots lost through transpiration in leaves.through transpiration in leaves.

1.1. Water lost byWater lost by Transpiration Transpiration throughthrough stomata stomata2.2. Transpiration rate Transpiration rate regulated byregulated by two guard cells two guard cells

surrounding each stoma.surrounding each stoma.3.3. Water neededWater needed for metabolic activity for metabolic activity such as such as

photosynthesis.photosynthesis.4.4. If plantsIf plants prevent water loss by closing guard cells prevent water loss by closing guard cells then no then no

C02 can enter for photosynthesis.C02 can enter for photosynthesis.

2) If the plants starts to get 2) If the plants starts to get dehydrateddehydrated, , high light levelshigh light levels and and temperaturetemperature cause cause abscisic acidabscisic acid to be released. to be released.

Abscisic acid is produced in most parts of the plants and Abscisic acid is produced in most parts of the plants and prepares the plant for dormancy ( the period when they do prepares the plant for dormancy ( the period when they do not grow) by not grow) by inhibiting growth.inhibiting growth.

Also plays a role in drought response.Also plays a role in drought response.

Abscisic acid stimulates the closure of the stomata in Abscisic acid stimulates the closure of the stomata in leaves when water is in short supply dehydration, and leaves when water is in short supply dehydration, and inhibits germinating in seeds.inhibits germinating in seeds.

When this abscisic acid to be released, When this abscisic acid to be released, this stops the this stops the proton pump working and no water enters the guard cell proton pump working and no water enters the guard cell by osmosis. by osmosis.

Therefore, The guard cells become Therefore, The guard cells become flaccidflaccid,, which means the which means the turgor pressure fallsturgor pressure falls and the and the guard cells straighten upguard cells straighten up

and and close the stomatal pores.close the stomatal pores.

THE ENDTHE END