Chapter1 transportation

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Chapter 1

TRANSPORT


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1.1 THE IMPORTANCE OF

TRANSPORT SYSTEM IN

MULTICELLULAR ORGANISMS Exchange of gases and substances

occurs across the plasma membrane of

the cells by diffusion.

In unicellular organisms, there is no

problem in obtaining the cell requirementsand removing the waste products bydiffusion. This is because diffusion caneasily occur across the plasma

membrane.


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Unicellular organisms such as amoeba sp.

are small in size. They have a large total

surface area to volume (TSA/V) ratio. This

enables the exchange of substances to

occur rapidly by diffusion.

Multicellular organism are bigger and more

complex. The cells cannot depend on

diffusion alone to obtain its cellrequirements.


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The problems faced by multicellularorganisms in sustaining lives are:

a) large body size organisms have a smalltotal surface area to volume (TSA/V) ratio.

As a result, the rate of diffusion ofsubstances is low.

b) as the size of an organism increases, theamount of cell requirements and metabolicwaste product also increases. So, diffusionalone is not sufficient.


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To overcome these problem, multicellularorganisms such as humans, animals and

plants need special transport systems totransport the nutrients to all the body cellsand to remove all the metabolic wasteproduct from the body cells.

The transport system in humans andanimal is the blood circulatory system.

In plant, the transport system is thevascular tissues which consist of xylemtissues and phloem tissues.


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1.2 THE CONCEPT OF

CIRCULATORY SYSTEM The circulatory system in human and

animal consists of :

a) Bloodb) Blood vessels

c) Heart

The medium of transport in human and

animals is the blood which flows in the

circulatory system.


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Composition of human blood Blood is a connective tissue in liquid form.

The human blood is made up of 55% plasma and

45% blood cells.

There are three types of blood cells:

a) Erythrocytes b) leucocytes c) platelets

Plasma is the liquid part of the blood. It is pale

yellowish in colour and contains various dissolved

substances.


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BLOOD

Blood cells 45% Plasma 55%

Water (90-92%)erythrocyte Dissolve substancesplatelet

Digested food

leucocyte

Excretory products

Mineral salts

vitamins

hormones

Plasma protein

Dissolved gases

granulocyte agranulocyte

neutrophil

eosinophil

basophil

monocytelymphocyte


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Erythrocyte (red blood cells)

Biconcave disc-the shaped with an elasticmembrane.

The biconcave disc- shaped increases theTSA/V ratio to facilitate exchange of gasesby diffusion across the membrane.

The elastic membrane enables theerythrocyte to change its shape so that itca squeeze through the narrow blood

capillary.


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Matured erythrocyte does not have nucleus. Thisenables the erythrocyte to contain more haemoglobin tocarry more oxygen.

Erythrocytes are produced in the bone marrow.

Erythrocytes survive for about 120 days and are then

destroyed in the spleen and liver.

Each erythrocyte contains haemoglobin which is arespiratory pigment containing iron and causes the bloodto be red in colour.

Haemoglobin is responsible for the transport of oxygenin the form of oxyhaemoglobin and carbon dioxide in theform of carbaminohaemoglobin.


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Leucocyte (white blood cell)

Has a nucleus and has no fixed shaped.

The number of leucocytes in the blood is lesser

than the erythrocytes, but its size is larger.

The function of leucocytes is to protect the bodyfrom diseases

There are two types of leucocytes:

a) Granulocytes b) agranulocytes


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Granulocytes (granular cytoplasm)

a) Have granules in the cytoplasma

b) Have lobed nucleus

c) Are formed in red bone marrow

d) There are three types of granulocytes:

i) neutrophil

ii) eosinophil

iii) basophil

Neutrophils are phagocytes which can carry outphagocytosis to engulf and digest invading bacteria.

Eosinophils function in regulating the allergicresponses.

Basophils produce heparin which prevent the bloodfrom clotting


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platelet

Fragments of larger cells in the bone

marrow called megacaryocytes. They

have no nucleus.

Platelets are involved in blood clotting.


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Plasma Pale yellowish liquid consisting of 90% water and large

number of dissolve substances such as:

Blood plasma without plasma protein such asfibrinogen is called blood serum.

a) Digested food materials such as glucose, amino acidsand fatty acids.

b) Excretory products such as urea, uric acid andcreatinine.

c) Minerals in the form of ions such as calcium, sodium,

chloride, potassium, bicarbonates and vitamins.d) Dissolved gases such as carbon dioxide, oxygen and

nitrogen.

e) Plasma protein such as albumins, globulins andfibrinogen.

f) hormones


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Function of blood in transport

1. Transport of oxygen

2. Transport of carbon dioxide

3. Transport of digested food, vitamins andminerals

4. Transport of nitrogenous waste product

5. Transport of hormones

6. Transport of heat

7. Transport of water


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Transport of oxygen

Blood transports oxygen in the form ofoxyhaemoglobin.

In the alveolus, the partial pressure of oxygen ishigher than the partial pressure of oxygen in theblood capillary.

Hence, the oxygen diffuses out from the alveolusinto the blood capillary around the alveolus by

simple diffusion

In the blood, oxygen combines withhaemoglobin in the erythrocytes to formoxyhaemoglobin.


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Oxygen is transported in the form of

oxyhaemoglobin to the body cells which

lack of oxygen.

At the body cells, oxyhaemoglobin breaks

down to release the oxygen to the body

cells for cell respiaration

lungsHaemoglobin + oxygen oxyhaemoglobin

body cells


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Transport of carbon dioxide Carbon dioxide is transported by the blood in

two main forms:i) ion hydrogen carbonate (ion bicarbonate) inthe blood plasma.

ii) carbaminohaemoglobin in the

erythrocyte

Carbon dioxide is transported from the bodycells to the lungs to be removed duringexhalation.

In the body cell, as a result of respiration whichrelease carbon dioxide, the partial pressure ofcarbon dioxide in the body cell is higher than

that in the blood capillary.


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Hence, carbon dioxide diffuse out from the bodycell into the blood capillary.

In the blood capillary, carbon dioxide dissolvesin the blood plasma to form hydrogen carbonateion and it is transported in the blood plasma to

the lungs.

At the lungs, enzyme changes the hydrogencarbonate ion to carbon dioxide again.

The carbon dioxide then diffuses out of theblood capillary into the alveolus to be removedduring exhalation.


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Carbon dioxide can also combine with

haemoglobin in the erythrocyte to form

carbaminohaemoglobin which is thentransported in the erythrocytes to the

lungs. At the alveolus,

carbaminohaemoglobin breaks down torelease the carbon dioxide which then

diffuse into the alveolus to be expelled out

during respiration.


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Transport of digested food,

vitamins and minerals Plasma transports digested food such as simple

sugars, amino acids, fatty acids, glycerol,vitamins and dissolve minerals.

Digested food such as simple sugars and aminoacids, minerals and vitamin B and C areabsorbed into the blood capillaries in the villus ofthe ileum. These nutrients are then transported

in the plasma from the ileum to the liver via thehepatic portal vein, then to the heart andsubsequently to the whole body for usage orstorage.


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Fatty acids, glycerol, vitamins A, D, E and

K diffuse into the lacteal of the villus and

are transported from the ileum to thelymphatic system then back into the

circulatory system via the left subclavicle

vein. The food materials are thentransported in the plasma to the whole

body.


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Transported of nitrogenous

waste products

Nitrogenous wastes such as urea are by

products of protein metabolism.

Product of deamination of excessive

amino acids in the liver, uric acid,

creatinine, bilirubin and ammonium ions

are transported by plasma to the kidneysto be excreted.


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Transport of hormones

Endocrine glands secrete hormones into

the bloodstream which are then

transported by the plasma to the targeted

organs.

Example, insulin hormone is transported

by the blood plasma from the pancreas to

the liver it acts.


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Transport of heat

Heat is produce during cell respiration whichoccurs actively in the muscle and liver, and alsoduring muscle contraction.

The heat is distributed evenly throughout thewhole body by the circulatory system. Excessheat can be removed by transporting it to theskin and the lungs by the blood so that the heat

is dissipated.

Hence, the body temperature is maintainedaround 37C.


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Transport of water

Water is a universal solvent. It acts as a

medium for all chemical reactions to take

place in the body.

The blood transports water to the whole

body regulate the equilibrium of water and

osmotic pressure in the body.

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Chapter1 transportation