Lifestyle health and risk

Diffusion is the free movement of particles in a liquid or a gas down a concentration gradient, from an arwa where they are at a high concentration to a low concentration

A unicellular organisim has a large suface area: volume ratio becuase its just one cell thick so it doesnt need to travel from cell to the cells inside it.

A multicellar organisim has a small suface area: volume ratio bcuz the distance from the outside of the organisim to the inside gets longer, there is also less surface area for substances to diffuse through. In larger organisims made up of billions of cells often have specialised organs and tissues.

In humans the systems used to get oxygen and food inot the body are the gut and lungs. To remove waste is the gut, lungs , skin and kidneys. They also have internal transport system to deliver O2 and nutrients to every cell.

Substances amde in the body can be transported around the body such as adrenaline.

The heart and circulatory system is a mass transport system, substances are are transported in the flow of fluid. They are transported though osmosis over short distances and active transport (energy is used to move substances against as concentration gradient).

Most transport systems have certain features. They have

• a sytem of vessels that carry substances, following a very specific route, wide spread and brancing
• a way of making sure that substances are moved in the right direction e.g. nutrients in and waste out
• a means of moving materials fast enough to supply the needs of the organism (pumping of the heart) or ways of maintaing the concentration gradient so that substances move quickly from one plce to another (active transport)
• a suitable transport medium

Water [H2O] has two atoms of hydrogen and one atom of oxygen. It is involved in photosyntesis on which life depends. Each water molecule is highly polarised. So it has a very slightly negative part [the O] and a very slightly +tive part [the H]. This separation charge is called a dipole, as a result also hydrogen bonds [weak electrostatic attraction]are made. Even thought the bonds are weak there there are many of them so they stick togeter quite well. It alkso has a high melting and boliing temp. becuse it takes quite some energy to overcome the attractive forces of all the hydrogen bonds.

IONIC -a chemical compound which is made up of positive and negative ions [cationwich is +tive] and [anion which is -tive]

POLAR-a molecule with a positve and negative end

NON-POLAR-chemicals that do not form ions

DIPOLE-a molecule with both a positively charged group and a negatively charged group.

COLLOID-formed by large particles non particels mixed with water (does not settle out)

EMULSIONS- tiny droplets of one liquid suspended in another liquid

SUSPENSIONS-a solid mixed with a liquid, in whihc the particles will separate out if the mixture is not consistantly moved or stired. Formed by large particles and non particles mixed with water (does not settle out)

WATER TENSION-formed bcuz H-bonds btwn water molecules pull the surface 2getha

AMPHOTERIC-the ability to accept or donate electrons to act as an acid or a base

BUFFER-helping to prevent reactions in progress from changing the pH inside the cell. any excess H+ and OH- ions are mopped up

1) Water is an unusual and excellent solvent Many other substancers can disolve in it. This is becuase water has a dipole means ionic subtances can will dissolve in it e.g. NaCl...the positve and negative ions will separate and become surrounded by water molecules which keeps then in the solution. Polar substances will disslove inw ater. However, water also carries many non-polar substances, these form colloids. the solute particles spread thought the water but do not separtate out. Bcuz the chem. reactions within our cells occur in water (aqueous solution). its ability toi act as a solvent is a vitally important feature.

The substances that do not dissolve in water are important also important in body. Insoluable particles form emulsions or suspensions. Blood is a suspension of cells and platelets in plasma.

Surface tension-is a property of liqiuds, when they behave as if the surface is covered by a thin elastic skin. There isnt such an attraction bwtn the water and air meet. So the water layer holds together forming a thin skin causes surface tention. It is of great importance in plant transport sysytems, and also pond surface life, lakes and other water masses.

3)The water molecule is amphoteric-it can act as both acid [forms H+ ions and is a proton] and base[it forms OH- ions and is a proton acceptor]. This ability of water to donate and recieve protons. This makes it a great and ideal medium for biochemical reactions and acts as a buffer

In humans mass transport system is the cardiovascular sytem...made up of a seris of vessles with a pump (heart) to move blood trough the vessels. The blood is the transport medium and its passage through the vessels is called circulation. It delievers O2 and nutrients and removes waste products like CO2 and of the metabolism.

It also carries- hormones, defense system, distributing heat

COMPONENTS OF BLOOD

PLASMA-straw coloured liquid and is the main component of blood, whihc consists largely of water. Plasma which also contains a wide range of dissolved substances to be transported and alos fibronogen [soluble] whihc is needed for clotting.

ERYTHROCYTES- biconcave disc, they contain heamoglobin, a red pigment which carries O2 and gives then the red colour. They are formed in the red bone marrow of the short bones such as ribs. Mature erythrocytes dont contain a nucleus and have 120 days life cycle

LUECOCYTES-these are much largewr then erythrocytes, but can also squeeze thru tiny blood vessles and can change shape. They all contain a nuclues and have a coulourless cytoplasm, there are several types. Most formed in white bone marrow of the long bones (humerusin the arm and fumur leg). Although lymphocytes are formed in the lymph glands and spleen...also denfent body against infection

PLATELETS- tiny fragments of large cells called magakaryocytes which are found in the bone marrow. Involed in clotting.

Function of blood the plasma ...

• transports digested food [glucose,amino acids] from small intestines to all the parts of the body for use / storage
• transports food molecules from storage area to the cells that need them
• transports excretory products [CO2 and urea] from the cells to oragans [lungs, kindneys]
• transport chem. messages [hormones] from where they are made to where they cause changes
• helps to maintian a steady body temp. by carrying heat aound the system from deep seated organ [gut] or very active tissues [legs]
• acts as a buffer to pH chnges

WBC's defend against disease in two ways

• makeing antibiotics which destroy pathogenbs or antioxins which nuetralise the poison [toxins] made by pathogens. WBC's will make memory cells to remeba pathogen qucikly if it attacks again
• and others engulf and digest pathogens in a process called phagocytosis

OXYGEN [O2]

• heamoglobin molecule packed in the red blood cells each heamoglobin molecule carries four molecues of O2
• O2 moves into the RBC's from the air in the lungs thru diffusion bcuz O2 is picked up and bound to the heamoglobin. the free O2 in cytoplasm remains low, this maintains a steep conc. gr. so more O2 is loaded into the heamoglobin
• In body tisues the O2 levels are low. The concentration of the O2 in the cytoplasm of the RBC's is higher than surrouding tissue, as a resulty O2 out into the body cells by diffusion down its conc. gr. and the heamoglobin give up some of their oxygen
• When u r at rest or excersiing gently on 25% of the O2 carried by heamoglobin is releasedinto ur cells
• There is anotha 75% reserve in the transport system for when u r v.active

CARBON DOIXIDE [CO2]

• Waste CO2 diffuses from respiring cells of the body tissues into the blood along a conc. gr
• When CO2 is dissolved in the blood it reacts slowly with water to form carbonic acid H2CO3..which separates to form H+ and HCO3-

CO2 + H2O=H2CO3=HCO3-+H+

• About 5 % of the CO2 is carried in the plasma...a further 10-20% joins with haemoglobin molecules to form carbaminohaemoglobin.
• Most of the CO2 is transported in the cytoplasm of the RBC's as hydrogencarbonate ions
• the enzyme carbonic anhydrase controls the rate of reaction btwn the CO2 and H2O to form carbonic acid
• in the lungs the CO2 conc. is low so carbonic anhydrase catlyses the reverse reaction so free CO2 diffuses out of the blood into the lungs

BLOOD CLOTTING

From a cut you could loose too much blood and die, and 2nd pathogens can get in ur body thru an open wound. To help with this plasma, blood cells and platelets flow from a cut vessel. Contact btween the platelets and components of the tissue [collagen fibres in the skin] cause the platelets to break open in large numbers. they release some substances like...

SEROTONIN-causes the smooth muscle of the blood vessel to contract. This narrows the blood vessels, cutting off the blood flow to the damaged area

THROMBOPLASTIN-an enzyme which sets in progress a cascade of events that leads to the formation of a clot

Blood clotting

• thromboplastin catalyses the conversion of the large molecule prothrombin found in the plasma into anotha enzyme called thrombin
• this happens on a large scale at the site, Ca2+ ions need to be present in the blood at the right conc. for the reaction to take place
• Thrombin acts on another plasma protein called fibrinogen, converting it to fibrin. This forms a mesh of fibres.
• Platelets, blood cells pouring from the wound get trapped in the fibrin mesh. this forms a clot
• Special proteins in the platelets contract, making the clot tighter and tougher.

Insects-open circulatory system in which the body pumps the blood around the body

Fish-single circulation the heart pupms the deoxynated blood to the gills were they recieve oxygen and become oxyganted , then to the rest of the body b4 returning to the heart

Birds and mammals-need far more oxygen than fish and they move around the support from water and maintain a constant body temp. higher than its surroundings this needs a lot of energy from food and oxygen and produce a lot of waste products that need to be removed quickly . For this reason birds and mammals posess the most complex system known as a double circulatory system

Systematic circulation-carries oxygentated (rich blood) from the heart to cells of the body were the O2 is used and carries deoxygenated blood back to the heart

Pulmunory circulation-carries deoxygenated blood back from the heart to the lungs to be oxygenated , and carries the oxygenated blood back to the heart

Separate circulatory system advantages-

• oxygenated and de(O2) blood cannot mis
• tissues recieve as much oxygen as possible
• fully oxygenated blood can be delievered qucikly to the body tissues
• goes thru vesselsat a low pr so it does not damage the vessels and allow gas excahnge to take place
• if the oxygeanted blood went tot the big vessels that carry it around the body it would move v. slowly...bcuz it returns to the heart the oxygeanted blood can be puymped hard and sent around the body at high pr.
• this emans it reaches the tiny capilaries btween the body cells quickly

ATERIES and VEINS are like wide motoways carrying 'heavy traffic' while the narrow town streets resemble the vast branching and spreading capilary network

ATERIES-they carry blood away from the heart towards the cells of the body. Almost all the arteries carry oxygenated blood the only exceptions are

• the pulmunory artery, carriny deoxygenated blood from the heart to the lungs
• during pregnancy, the umbilical arterty carries deoxygenated blood from the fetus to the placanta

the arteries leaving the heart branch off into every direction, the diameter of the lumen gets smaller the further way it is from the heart. The very smallest of branches of the atrial system are the arterioles. Blood is pumped at about 70times a minute...this sends a surge if blood into the arteries. The major arteries close the heart to withstant the pressure surges. Thier walls contain a lot of elastic fibres so they can strech to accomodate the greater volume, without being damaged. Btwen them they return to thier original size therefore squeezing the blood and keeping it on a continuous flow. each pulse is the surge of an artery.

The blood pressure in all the arteies are high but it falls in the arteries further away from the heart (the peripheral arteries). In the peripheral arteries the muscle fibres in the vessel walls contract or relax to change the size of the lumen, controlling the blood flow. The smaller the lumen the harder it is for the blood to flow through the vessel. This controls the amount of blood that flows into an organ, so regulating the activity of the organ.

VEINS-they carry blood back to the heart, most of them carry deoxygenated blood, but the exceptions are

• the pulmunory vein which carries oxygen rich blood from the lungs back to the heart for circulation around the body
• during pregnancy, the umbilical vein carries oxygenated blood from the placenta into the fetus

Tiny venules lead from the capilary network, merging into larger vessels leading back to the heart. Eventually only two veins carry the returning blood to the heart, the inferior vena cava from the lower parts of the body and superior vena cava from the upper parts of the body. Veins can hold a large volume of blood, more than half the boies blood is in the veins at any 1 tym. They act as a resevior. The blood pressure in the viens is relatively low. This blood at low pr. must be returned to to the heart to be oxygenated again and recirculated. There are two ways this is achieved:

• at frequent intervals thru the system there are one way inervals called the semilunat valves bcuz of thier half moon shape. They are formed from infolding of the inner wall of the vein. Blood can pass thru towards the heart, but it starts to flow backwards the valves close to prevent this.
• the larger veins are sitiated inbtween large musles blocks of the body especially in the arms and legs. When the muscles contract during physical activity they squeeze these veins. This helps the valves in keeping the blood flow in one  direction. The squeezing helps to return the blood to the heart.

Aterioles feed into networks of capilaries. These are minute vessels that spread throughout the tissues of the body. The capillaries branch btween cells and the body quickly. Also, bcuz the diameter of each individual capillary is small, the blood travels relativly slowly thru them, giving more oppotunity for diffusion to occur. The smallest capillary is no wider than a single RBC.

They have a very simple structure well suited to thier function. Thier walls are v. thin, containing no elastic fibres, smooth muscle or collagen. This helps them fit btween individual cells and also allows rapid diffussion.  

The walls consist of just one very thin cell, so oxygen and otha molecules quickly diffuse out of the cell into the nearby cells, and CO2 and otha waste molecules diffuse in.

Blood entering the capillary network from the arteries is oxygenated. By the time it leaves, it carries less oxygen and more CO2.