10. Transport System in Organisms E-learning - Diffusion & Osmosis

Transport System in Organisms

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Diffusion and Osmosis

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Learning Outcomes for Section 1At the end of this lesson, you should be able to:

observe and infer that diffusion is the movement of molecules from a region of higher concentration

observe and infer that osmosis involves the movement of water molecules when two solutions of unequal concentration are separated by a partially permeable membrane

explain how diffusion and osmosis are involved in the transport system

explain the need for a transport system in multicellular organisms

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Eww... What’s that smell???

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How can we smell rubbish? Smell come from vapour from the

rubbish.Particles in the vapour move

about randomly.They bump into each other and

spread out quickly.Some of the particles enter our

nostrils.The spreading out of particles is

brought about by diffusion.

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DiffusionDiffusion is the movement of particles from a region

of higher concentration to a region of lower concentration.

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What is happening?

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10.1 Diffusion and OsmosisFactors Affecting the Rate of Diffusion

Factor EffectTemperature ↑ Temperature, ↑ rate of diffusionMolecular Mass ↓ Molecular mass, ↑ rate of

diffusionThickness of barrier

↑ (Thicker) cell wall, ↓ rate of diffusion

Concentration gradient

↑ Concentration gradient, ↑ rate of diffusion

Surface-area-to- volume ratio

↑ Surface area-to-volume ratio, ↑ rate of diffusion

10.1 Diffusion and OsmosisSurface area-to- volume ratio

Cube Sides 1 cm Sides 2 cm Sides 3 cmSurface area/ cm2

6 x 1 x 1 = 6 6 x 2 x 2 = 24 6 x 3 x 3 = 54

Volume/ cm3

1 8 27

Surface area-to- volume ratio

6 : 1 24 :8= 3 :1

54 : 27= 2:1

Time/ s 1 3 10

The greater the ratio, the faster the rate of diffusion.

Diffusion through a Membrane

Diffusion can also occur through a membrane.

There are two types of membranes:Fully permeable membrane

Example: Cell wall of plant cellsPartially permeable membrane

Example: Cell membrane of cells

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Diffusion through a Permeable Membrane

A fully permeable membrane allows all molecules to pass through it.

A partially permeable membrane allows only small molecules but not large molecules to pass through it.

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Diffusion through a Partially Permeable MembraneA partially permeable membrane allows only small molecules

to pass through its pores but not the large ones.The small glucose molecules diffuse through the membrane

(Visking tubing) from inside the tube (higher glucose concentration) into the water (lower glucose concentration).

The starch molecules are too large to pass through the membrane.

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Diffusion in Living Organisms1. Photosynthesis

Carbon dioxide diffuses from the air (higher carbon dioxide concentration) into the cells in the leaves (lower carbon dioxide concentration)

Oxygen produced diffuses from the cells in the leaves (higher oxygen concentration) into the air (lower oxygen concentration).

Gases exchange take place via the stomata.

Diffusion in Living Organisms2. The Human Body

In the human digestive system, digested food diffuses through the wall of the small intestine into the bloodstream.

Also, food and oxygen diffuse from the blood through the cell membranes into the body cells.

Osmosis When a piece of raisin is soaked in water, it swells

up and becomes less wrinkled.Water has diffused into the cells of the raisin through

the partially permeable membrane.

After soaking in

water for 1 h

Turgid (larger and firm)

Flaccid (smaller and soft)

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OsmosisOsmosis is the net movement of water molecules

through a partially permeable membrane from a region with a higher concentration of water molecules to a region with a lower concentration of water molecules.

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An Example of OsmosisA piece of potato is placed in distilled water.

After 20 minutes

After 20 minutes

original

Distilled water

An Example of OsmosisAfter 20 minutes of soaking in distilled water, the

potato pieces become larger, longer and firmer.

The water concentration of distilled water is higher than the water concentration of in the potato cells.

Therefore water molecules move via osmosis from the distilled water into the potato cells causing them to swell and become turgid.

Another Example of OsmosisWe can show osmosis using Visking tubing.

The pores in the Visking tubing allow the smaller water molecules but not the larger sugar molecules to pass through.

Another Example of Osmosis

The water concentration is _________ in the beaker than in the Visking tubing.

Therefore, water molecules move via _________ from the water in the beaker into the Visking tubing.

higher

osmosis

Another Example of Osmosis

This causes the water level in the glass tube to _______ and the water level in the beaker to _______.

risedrop

Osmosis in Living Organisms1. Roots

Water from the soil enters the root hair cells of a plant by osmosis.

This is because the water concentration in the soil is higher than in the cell solution of the root hair cells.

Osmosis in Living Organisms2. Stems and Leaves

Water moves into the cells of stems and leaves of a plant by osmosis.

This makes them firm and strong. Stems of non-woody plants need turgid cells to support

the plants. If this support is lost, the plant wilts.

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Why is a transport system important to

multicellular organisms?

Diffusion and Osmosis in Unicellular OrganismsIn unicellular organisms, materials move into and out

of the cell directly by diffusion and osmosis. Hence, these organisms do not need a transport

system.

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O2CO2

Is diffusion and osmosis efficient for multicellular organisms?In multicellular organisms, there are many cells. Most of

these cells are far away from the outside of the organism. Diffusion and osmosis alone are not fast or efficient

enough for the cells to get materials directly from the environment.

Hence, transport systems are needed to take substances to all the cells and to carry waste substances away.

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Something Interesting

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Checkpoint TimeDiffusion and osmosis are two common modes of movement for substances in living organisms.a) Give one example of diffusion taking place in living

organisms.

b) Give one example of osmosis taking place in living organisms.

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Checkpoint TimeState whether each of the following statements about osmosis is true or false.

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Statement True or

False

(a)Osmosis takes place when two solutions of different concentrations are separated by a partially permeable membrane.

(b)Osmosis can only take place in living tissues.

(c)Osmosis is the net movement of water molecules from a solution of lower concentration to a solution of higher water concentration through a partially permeable membrane.

Transport System in Plants

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describe briefly the process of absorption of water and mineral salts by the root of a plant

describe briefly the transport of water and manufactured food substances in the plant

explain the function of phloem and xylemuse terms such as translocation, transpiration pull,

active transport, diffusion and osmosis in the description of plants transport system

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The Tallest Tree in the WorldThe giant redwood trees

in the USA.The trees are more than

a 100m tall.Everyday, the giant

redwood tree moves 1000kg of water from the soil to their leaves, 100m above the ground.

Is Osmosis sufficient?

Transport System in PlantsPlants need a transport

system to carry water, food and dissolved minerals to all cells in the plant.

The transport system is made up of vessels in the root, stem and leaves.

Vessels of the Plant Transport System

There are two types of vessels:

1. Xylem VesselsMade up of dead cells

and have thick wallsCarry water and

dissolved minerals from the roots to all parts of the plant.

Xylem vessels in the roots

Vessels of the Plant Transport System

2. Phloem VesselsMade up of living cells and have thin wallsCarry sugar produced in the leaves to other

parts of the plant.

Phloem vessels in the

roots

Vascular BundlesThe two vessels often run side by side forming

vascular bundles. Xylem vessels in

stem Phloem vessels in

stem

Vascular bundle

Observing vascular bundles in a celery stem

Xylem and Phloem in Different Parts of the Plants

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1. Place a balsam plant in a container of dilute red ink for one day.

10.3 Transport System in Plants• Experiment 1: The path of water

through a plant

2. After one day, wash the roots under running tap water.

How is water

transported in a plant?

Transport tissue in plants

3. Observe the stem and leaves of the balsam plant. You will find that the red ink has risen in certain strands of the stem and veins of the leaf.

10.2 Transport System in Plants• Experiment 1: The path of water

through a plant

• The strands are vascular bundles which are part of the plant transport system.

• In the balsam plant, the vascular bundles are arranged in a ring within the stem.

• Each vascular bundle consists of xylem tissue and phloem tissue.

Which part of the vascular bundle was

actually stained red?

10.2 Transport System in Plants

The xylem tissue In Experiment 1, the xylem tissue was stained red. The xylem tissue consists of long tubes or vessels that pass from the roots to the leaves. Hence, the xylem tissue is able to transport water and mineral salts from the roots to the leaves.

xylem tissue phloem tissue

The phloem tissue The phloem tissue transports food (e.g. sugars) produced in the leaves to other parts of the plant.

10.3 Transport System in Plants• Experiment 2: How is food

transported in a plant?

1. Take the stem of a woody plant (e.g. hibiscus). Remove a ring of bark around the main stem. This should remove the phloem tissue, leaving the xylem tissue intact.

2. Water and mineral salts can still be transported in the plant.

10.3 Transport System in Plants3. After a few weeks, the part of

the stem just above the cut region will swell.

• Food cannot reach the roots because the phloem tissue is removed. It collects in the stem just above the cut, causing that area to swell.

• Without food (sucrose, amino acids), the roots will starve and die. The plant will eventually die as its roots cannot take in water from the soil.

What causes the swelling at this part?

vacuole

root hair cell

cytoplasm

cellulose cell wallcell

membrane

Absorption of Water and Mineral Salts by Roots

How are water and mineral

salts taken into a plant?

soil particlefilm of water

vacuole

root hair cell

cytoplasm

cellulose cell wall

cell membrane


Soil contains water and mineral salts. The root hair cells take in water by osmosis. The root hair cells also take in mineral salts by active transport, a process which requires energy.

Key:Movement of mineral saltsMovement of water molecules

lower concentration of water molecules

higher concentration of water molecules

Absorption of Water and Mineral Salts by Roots

Absorption of Water and Mineral Salts by RootsKey:

Movement of mineral saltsMovement of water molecules

vacuole

root hair cell

cytoplasm

cellulose cell wallcell membrane


lower concentration of water molecules

higher concentration of water molecules

After the water and mineral salts are taken in, the water molecules move from one cell to the next by osmosis.

The mineral salts move from one cell to the next by diffusion.

The water and mineral salts will continue to move from one cell to the next until they reach the stem.

How does this

process allow

plants in

hydroponic

systems to

survive?

Transport of Water and Mineral Salts (Xylem)

Water and mineral salts move up the plant mainly by transpiration pull and in some plants, by root pressure.

Transpiration pullThis pulling force is produced

when water evaporates from the leaves through the stomata.

This force is similar to someone sucking up liquid through a straw.

A pretty blue rose from a plain white one.

Transport of Food (Phloem)During photosynthesis, food is produced in the leaves in the form of sugar (glucose) which is then transported to other parts of the plant via the phloem.There is a higher sugar concentration in the leaf than in the phloem vessels which are constantly transporting sugar to other parts of the plant.

Therefore diffusion occurs to transport sugar from the leaves to phloem vessels.

The movement of glucose in the phloem occurs in both directions.

Transport of Food (Phloem)

Exchanges of Gases during Photosynthesis

Carbon dioxide is needed for photosynthesis. There is a higher concentration of carbon dioxide in the surroundings than in the leaf. Therefore, carbon dioxide diffuses from the surroundings to the leaf.

Oxygen is produced during photosynthesis. There is a higher concentration of oxygen in the leaf than in the surroundings. Therefore, oxygen diffuses from the leaf to the surroundings.

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Transport System in a Flowering Plant

1. Water enters a plant through its roots by osmosis. Dissolved minerals are absorbed through diffusion and active transport.

2. Water and minerals move up the stem through xylem vessels.

3. Xylem vessels carry water and dissolved minerals from the roots to the leaves.

4. Most of the water evaporates and diffuses from the leaves through transpiration.

7. Oxygen diffuses from the leaves to the surroundings.

8. Sugar moves from the leaves through phloem vessels to the rest of the plants.

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Movement of waterMovement of sugarMovement of carbon dioxideMovement of oxygen

5. Carbon dioxide diffuses from the surrounding to the leaves.

6. Carbon dioxide and some water are used during photosynthesis by the leaves to produce sugar and oxygen.

Checkpoint TimeComplete the following sentences.1. Water molecules that are taken into a plant move

from one cell to another by ________________.2. Plants can obtain ______________ and

________________________ from soil.3. Mineral salts that are taken into a plant move from

one cell to another by __________________.

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Checkpoint TimeThe figure below shows a cross section of the stem of a green plant.

a) Identify the parts labelled 1 and 2.1: _____________________2: _____________________

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Checkpoint Timeb) Name the substances transported by the parts

labelled 1 and 2.1: ______________________________________2: ______________________________________

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Transport System in Humans

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describe and explain the functions of the 3 main transport system in humans i.e. the heart, the blood vessels and the blood

understand parts of the heart and the double circulation system involved

understand the function of arteries, veins and capillaries and briefly describe areas where they are found

briefly describe different parts of the blood and how blood acts as a transport medium

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Transport System in HumanCirculatory system is the main

transport system in the human body.

It consists of three parts:1. Heart – an organ which pumps

blood around the body2. Blood – a liquid which

transport materials3. Blood vessels – network of

tubes which carry blood round the body

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Transport System in Human1. Heart

Its purpose is to pump blood round the body.

The heart has 4 chambers. Two upper chambers called the

right atrium and left atrium (plural: atria)

Two lower chambers called the right ventricle and left ventricle (plural: ventricles)

The wall down the middle of the heart that separates the left side from the right side is called the septum.

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Transport System in Human1. Heart

The valves in the heart open and close to ensure that blood flows only in one direction.

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Section of a Mammalian Heart

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Artery

Septum

Vein

Right atrium

Valve.

Valve

Right ventricle

Artery

Vein

Left atrium

Valve.

Valve

Septum

Left ventricle

Transport System in Human2. Blood

The human body has about 5 litres of blood. Blood has 2 functions:

To transport materials (e.g. nutrients, oxygen, carbon dioxide and other waste substances) round the body

To protect us against diseases Blood contains:

a. red blood cellsb. white blood cellsc. plateletsd. plasma

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Red blood cells Red blood cells are biconcave in shape to

increase its surface-area-to-volume ratio for oxygen absorption.

Red blood cells have no nuclei so as to pack in more oxygen.

Red blood cells contain haemoglobin, which combines with oxygen and carries it round the body

The haemoglobin then releases oxygen as it passes the cells. This oxygen is used by the cells for respiration.

The red blood cells then collect carbon dioxide (a waste product of respiration) by diffusion.

The red blood cells are bright red when they carry oxygen.63


Red blood cells When oxygen is bound to

haemoglobin, blood appears to be bright red.

At the cells where oxygen is needed for respiration, haemoglobin will release the oxygen molecules it is carrying.

When oxygen is released from haemoglobin, blood appears to be dark red.

The red blood cells then collect carbon dioxide (a waste product of respiration) by diffusion.

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White blood cells There are fewer white blood cells than red blood cells. They are colourless and are larger than red blood cells

and have nuclei. Some white blood cells are used to fight infections. They produce antibodies to kill bacteria Alternatively, they engulf and digest bacteria.

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White blood cells

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Platelets These are tiny pieces of blood cells. They help blood to clot when we bleed.

Platelet

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Plasma Plasma is a pale yellow liquid made up of 95% water with

dissolved substances including nutrients (glucose, amino acids, fatty acids, mineral salts) and waste substances.

It transports digested food, waste materials (e.g. carbon dioxide and urea) and other materials (e.g. hormones and mineral salts).

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Transport System in Human3. Blood Vessels

Blood vessel is a network of tubes carrying blood around our body, from the heart to the rest of our body, and then back to the heart.

There are three types of blood vessels: arteries, veins and capillaries.

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3. Blood VesselsTransport System in Human

Artery Vein CapillaryFunction Carry oxygenated blood

away from the heart to all other parts of the bodyExcept pulmonary artery

Carry deoxygenated blood from the rest of the body back to the heartExcept pulmonary vein

Connect arteries to veinsCarry blood to all cellsAllow exchange of nutrients, gases and wastes

Pressure Under high pressure Under low pressure -

Thickness of walls

Have thick, elastic muscular walls

Have very thin walls Have walls which are one-cell thick (to ensure fast diffusion of substances)

Presence of valves

No Yes (To prevent the backflow of blood)

No

Diagram

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right

lung

Key:Deoxygenated bloodOxygenated blood brain

other parts of the body

left lung

VeinsVeins carry blood towards the heart.

heart

right

lung



left lung

The arteriesThe arteries carry blood away from the heart.

The heartThe heart is a muscular pump. Its pumping action keeps the blood circulating around the body quickly and continuously.

heart


n Humans

right

lung



left lung

The capillaries These are very tiny blood vessels that connect the arteries to the veins. The capillary walls are one-cell thick. This allows quick diffusion of nutrients and oxygen from the blood to the tissue cells. The capillaries Waste substances such as carbon dioxide can also move from the tissue cells into the blood in the capillaries.

BloodBlood is continuously circulated around the body, transporting many substances. Blood also protects the body from disease-causing germs.

BloodIn places with low oxygen, our body produces more red blood cells to transport more oxygen.

heart


Transport System in Human

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Transport System in HumanExplain why the left ventricle has a thicker muscular

wall than the right ventricle.

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The left ventricle must pump blood at high pressure so that blood can travel to the rest of the body.

Double Circulation in HumanThe double circulatory system of blood flow occurs when

the blood enters the heart twice.All animals with lungs have a double circulatory system.

The cycle is heart body heart lungs heartIn contrast, fish have a single circulation system because

they do not have lungs. The cycle is heart gills body heart

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Double Circulation in HumanDouble circulation is much more efficient than single

circulation. In a fish blood pressure goes down as is passes through capillaries in gills so it is slower and takes longer for oxygen and nutrients to get around the body.

In humans the blood pressure can be increased after it has left the lungs. It is faster. Humans are more active than fish and need to produce more energy and heat.

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Respiratory System: LungsIn the lungs, blood picks up oxygen and loses

carbon dioxide.

The air we breathe contains high concentration of oxygen and low concentration of carbon dioxide.

Lung

The blood flowing towards the lungs contains low concentration of oxygen and high concentration of carbon dioxide.

Therefore, oxygen from the lungs will diffuse into the blood and carbon dioxide from the blood will diffuse into the lungs.

Respiratory System: Lungs

Lung

Our Respiratory System

Digestive SystemIn the small intestine,

blood picks up small, digested food molecules such as glucose, amino acids and fatty acids.

As the blood flows around the body, it will distribute these food molecules to the cells that need them.

Oesophagus

Checkpoint TimeIdentify the components of the human circulatory

system.

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Checkpoint TimeThe diagram below shows a vertical section of the heart in humans.

Label A, B, C and D.A: __________________ B: ___________________ C: __________________ D: ___________________ 83

Checkpoint TimeThe diagram below shows a vertical section of the heart in humans.

In which labelled structure does blood reach the maximum pressure?

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10. Transport System in Organisms E-learning - Diffusion & Osmosis