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Transport systems
Within an organism substances need to be moved from one place toanother - glucose to cells for respiration, Carbon dioxide out of cellsNutrients, ions, water etc
To start with : Simple organisms Diffusion is the main mode of transport it is the free moveme
particles in a liquid or gas down a concentration gradient, from anarea of high concentration to an area where the same particles are inlow concentration
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To compare diffusion among organismsSize, Surface area and gas exchange
The amount of oxygen needed by an organism is determined by: The amount of living cells The rate they need to respire
Requirement of oxygen is related to volume of an organism and rate depends on the surface area .
Note: make sure you understand Ficks Law from BY1
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Which organism has the highest volume?
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Which has the most surface available forgas exchange?
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Large Organisms e.g. Elephant
The surface area to volume ratio is much smaller
The external surface area of the body is not large enough for diffusionof oxygen through it to take place rapidly enough to supply cells withthe oxygen it needs.
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Features of a mass transport system
A system of vessels to carry substances from e.g. tubes or bloodvessels A way of making sure that substances are moving in the right
direction. Eg. Nutrients in and wastes out Means of moving materials fast..eg the heart, or a concentration
gradient A suitable transport medium e.g Blood, water
Work sheet
http://d/abc/Newton%20Stuff%20Term%201%20unsorted/Term%201%202013-2014/Biology%20IGCSE%20notes/Y%2012/1.1%20Transport%20around%20the%20body/Diffusion%20of%20gases%20work%20sheet%201.dochttp://d/abc/Newton%20Stuff%20Term%201%20unsorted/Term%201%202013-2014/Biology%20IGCSE%20notes/Y%2012/1.1%20Transport%20around%20the%20body/Diffusion%20of%20gases%20work%20sheet%201.doc8/10/2019 11 1transport Systems
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Water in living organismsThe chemistry of water
Made of slightly negative oxygen atom which are attracted slightlypositive Hydrogen atoms in a model as one shown
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Water has a simple molecular structure. It is composed of one oxygen atom and two hydrogen atoms.Each hydrogen atom is covalently bonded to the oxygen via a shared pair of electrons. Oxygen also hastwo unshared pairs of electrons. Thus there are 4 pairs of electrons surrounding the oxygen atom, twopairs involved in covalent bonds with hydrogen, and two unshared pairs on the opposite side of theoxygen atom. Oxygen is an "electronegative" or electron "loving" atom compared with hydrogen. Wateris a "polar" molecule, meaning that there is an uneven distribution of electron density. Water has apartial negative charge (-) near the oxygen atom due the unshared pairs of electrons, and partialpositive charges (+) near the hydrogen atoms.An electrostatic attraction between the partial positive charge near the hydrogen atoms and the partialnegative charge near the oxygen results in the formation of a hydrogen bond as shown in theillustration.
The ability of ions and other molecules to dissolve in water is due to polarity. For example, in the illustrationbelow sodium chloride is shown in its crystalline form and dissolved in water.
The polarity of water
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Importance of water
1. Water is an excellent solvent substances dissolve in water ean ionic substance the positive and negative charges gets attracted tovarious parts of the water molecule and gets dissolved Substancesthat may not dissolve in water may form colloids where solidsparticles do not completely separate out but remains spread out.Some others remain as emulsions (tiny droplets of one liquidsuspended in another liquis) or supensions (solid particles mixed withliquid.
Blood is suspension of cells and platelets in plasma Fats can be transported as emulsions
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2. surface tension . - behaving like there is a thin surface skin, duemuch attraction between water molecules
3. Amphoteric nature of water . - being able to act as both acid(donating protons) and base (forming OH- ions and hence a protonacceptor) due to this nature water acts as a buffer in the cells helping
reactions in progress from overproducing H+ or OH ions by moppingthem up
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Blood and the cardiovascular system
Components Plasma , - mainly water, has a wide range of dissolved of dissolvedsubstances, Fibrinogen vital for clotting
Erythrocytes Biconcave discs, 5 million per 1 mm of blood, formed in thbone marrow and short bones. Contain haemoglobin, red in colour. Lifespan120 days
Leucocytes much larger, about 4000 to 11000 per mm of blood, formed inbone marrow of long bone and femur in the leg, lymphocytes are howeverformed in the lymph glands and spleen. Defence
Platelets tiny fragments of cells called megakaryocytes. Involved in clott
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Functions of blood
Transport of food substances to the cells as needed Tranport of excretory products e.g. CO2 and urea to the cells that
excreate them Tranport of hormones Help to maintain a steady body temperature by distribution of heat Acts as a buffer to pH changes
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How well adapted are Erythrocytes
Biconcave shape enhances more surface area to volume ratio No nucleus mean more space created to pack haemoglobin Numerous on the blood, 5 mill per mm of blood
Leucocytes some makes antibodies which destroy pathogens Some engulf the pathogen itself. (phagocytosis.)
T i d b di id
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Transporting oxygen and carbon dioxide. A) Oxygen a haemoglobin molecule can pick up four molecules of oxygen and
bind to them. The conc of O2 in the RBC when blood enters the lung
is low, hence diffusion of O2 into the blood takes place
Oxygen binds to the haemoglobin which means that at no time willthere be free oxygen in the blood thus a steep conc of oxygen isalways maintained and hence more O2 is loaded
In the cells the O2 conc is low in comparison to the blood so the O2diffuse into the cells
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B) Carbon Dioxide. CO2 Diffuses from respiring cells into the blood along a concentratio
gradient. CO2 reacts with water in the blood to form carbonic acid which
separates into H+ and HCO3- CO2 + H2O H2CO3 H+ + HCO3 About 5% of the CO2 is carried in solution in plasma 10-20% is carried in haemoglobin forming Carbaminohaemogl The rest is in cytoplasm of blood as hydrogen carbonate ions. Enzyme
carbonic anhydrase controls the rate of rxn between CO2 and wate The H+ produced in the process are accepted by the haemoglobin
acting as a buffer to prevent any pH changes of blood
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Bl d l i h i
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Blood clotting mechanism Why would you need your blood to clot as soon as possible if an injury happens ?
Escaping blood would render transport of substances difficult Pathogens can enter in the wound and cause an infection
luckily a mechanism of blood clotting is in place to ensure less lossContact of the platelets and the collagen fibres in the skin causes them to break andrelease substances
Serotonin causes the smooth muscle of blood vessel to contract makimore narrow and thus less blood flow through
Thromboplastin an enzyme that sets a number of reactions
catalyses the protein prothrombin to enzyme thrombin,. Thisreaction needs calcium ions
Thrombin acts on another plasma protein fibrinogen converting it tofibrin, a meshwork of fibres
More platelets and cells pouring from the wound gets trapped and theyform a clot
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Circulation systems
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Circulation systems Open and closed Insects have open - blood not confined into special tubes Larger animals have closed- Blood running in confined tubes, the
blood vessels fish have single circulation blood goes through the heart once for a
single circuit
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Birds and mammals need a more complex system due to movingaround without the support of water but also maintain a constantbody temp. hence a double circulation.
Systemic circulation carries oxygenated blood to the tissues from the hea Pulmonary circulation takes deoxygenated blood from heart to lungs
Advantages deoxygenated and oxygenated blooddoes not mix hence as much oxygen as possible to the cells Fully oxygenated can be delivered to cells at
high pressure
e oo vesse s
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e oo vesse s Arteries
Carry blood away from heart All arteries carry oxygenated blood except pulmonary artery which carry
deoxygenated blood from heart to lungs
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Major arteries more of Elastic fibre to stretch and accommodatemore pressure of blood without being damaged
Other types are smooth muscle which are more in arteriolescollagen fibres. Peripheral arteries have more of muscle fibre
collagen gives general strength and flexibility to both arteries andveins
Capillaries -Arterioles branch into these. Every cell in the body is in close proximity
with a capillary. A simple structure suited to their function.- No muscle or fibre in their structure, enabling them to fit
between cells for rapid diffusion of substances- one cell thick for efficient diffusion of nurients and oxygen in
and CO2 out of cell
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Veins carry blood back to the heart. Carry deoxygenated blood except the pulmonary vein which carries
oxygenated blood from lungs to heart. Umbilical vein carries oxygenated blood from placenta into fetus
Veins hold the bulk of blood in the body due to their flabby nature. Blood in veins is under low pressure and is to take it back to heart depends on
Valves found at intervals that prevent back flow when it its pushed forward Most veins are found between muscles which when they contract the reduce the volum
of vein thus pushing blood forward
oo rcu at on an ancer
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Cancer is uncontrollable growth of abnormal cells called tumor. The formation of new blood vessels anywhere in the body is called
angiogenesis. Cancer cells produce an activator molecule thattriggers angiogenesis which nourish growth of tumor
To treat it? Blocking the blood vessels Dr Erki Rouslahti and team developed a peptide mole
which binds to cancer cells in mice by attaching it to nanoparticles. The peptide moleccauses blood clotting on the vessels supplying the tumor with blood forming a blockwhich cuts of nutrient supply on the tumor. 20% successful but still under research
Blocking receptors - Dr Isaiah Fidler using knockout mice showed that a drug caGlivec could stop the growth of receptor molecules in the epithelial cells which responto triggers produced by cancer cells
oo rcu at on an ancer
ce as o e s - e ca ques ons
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ce as o e s - e ca ques ons 2007 Sir Martin Evans was awarded a Nobel prize for his work on
gene technology and knockout mice. ( Mice with specific genessilenced or replaced so that they develop cancer or other disease.
This has revolutionized the study using animals and reduced the cost
of using animals for testing.
But the society asks whether it is right to modify genes and the ideaof using animals as toolkits raises concerns
Changing genes so that an animal can get a disease seems cruel toanimals
