chemicals > transported from outside to in > waste products created > they need to be removed

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1 1 Transport systems chemicals > transported from outside to in > waste products created > they need to be removed Simple organisms Diffusion the free movement of particles in a liquid or a gas down a concentration gradient from an area where they are at a relatively high concentration to an area where they are at a relatively low concentration. The bigger an organisms gets, the smaller the surface area to volume ratio becomes. The distance from outside the organism to the inside gets longer, and there is less surface for substances to enter through. So it takes longer for substances to diffuse in. Large organisms Specialist systems e.g. guts / lungs to get in and remove waste Internal transport system transport substances around the body such as hormones The transport system in humans is the heart and circulatory system and the blood which flows through it. This is an example of a mass transport system substances are transported in the flow of a fluid with a mechanism for moving it around the body. All large complex organisms have some form of a mass transport system. Substances are delivered over short distances from the mass transport system to individual cells deep in the body by processes such as diffusion, osmosis and active transport. Osmosis the movement of water along a concentration gradient through a partially permeable membrane. Active transport energy is used to move substances against the concentration gradient Features of a mass transport system Vessels to carry substances Way of ensuring substances move in the correct direction Method of transporting materials fast enough to supply the needs of the organism this may involve mechanical methods or ways of maintaining a concentration gradient so that substances move quickly from one place to another.

2 2 Biology : Water Structure Dipolarity oxygen negative, hydrogen positive - bonds between two water molecules Hydrogen bonds oxygen + hydrogen strong lattice liquids break reform dissolve others Polar molecules attracted to charges, spread out among them water molecules Polar can dissolve hydrophilic, Solution free movement for the reactants to react, minerals to lakes, metabolic waste removed Cohesion surface tension attraction, top molecules > down skin, travel/ planar surface Adhesion attraction to dissimilar molecules on surfaces of plants Density bonds dense living organisms have similar density, can float aquatic organisms can swim, ice is less dense than water and floats, insulating water underneath and preventing all water from freezing, organisms can live underneath Metabolite Photosynthesis- plants gain energy / glucose for living processes Photolysis splitting of light molecules using light energy, in PS water to oxygen useful Movement across membranes Osmosis allows balance of water in cells, molecules break and reform Moistens gaseous exchange membranes - hydrostatic Habitat for aquatic organisms Transparency allows photons through for photosynthesis Constant water temperature for organisms to live in Support Turgor high water content keeps plants rigid Plasmolysis water loss from osmosis - allows right amount to be there Hydrostatic skeletons worms / jellyfish fluid for muscles and locomotion Temperature regulation Latent heat of evaporation energy required liquid to gas (attractions between molecules), water would dry quickly otherwise lot of energy for sweat cool us down, plants mesophyll 24C High heat capacity molecules are attracted to each other, takes a lot of kinetic energy to move them / increase temperature, can maintain heat level, disregarding fluctuations in environmental temp, important for metabolic processes with water Transport Blood plasma glucose, hormones, mostly water Transpiration stream capillarity atmospheric pressure xylem water Translocation transport of nutrients from phloem to rest of plant Removal of waste in the form of urine

3 3 Reproduction Gamete transfer allows sperm to get to ovum Seed dispersal can carry seeds because of density Digestion / Absorption Medium for enzyme action Hydrolysis using water to dissolve organic compounds Absorption allows absorption of nutrients Secretions Tears clean / lubricate the eyes / infections aqueous layer in tear film Saliva break down food in mouth / protect it (amylase) Physical protection Amniotic fluid surrounding the embryo, protects the foetus from heat loss / pressure Synovial fluid eases movement of synovial joints in body Pleural fluid pleural cavity allows movement of chest wall whilst breathing Health waste sweat temperature

4 4 Biology Revision Summary Diffusion free movement of particles in liquid/gas down a concentration gradient from an area where they are at a relatively high concentration to one where they are at a low concentration. Surface area to volume ratio bigger the organism the smaller the ratio Mass transport system hormones (chemicals made one place and transported else where) Osmosis diffusion active transport to transfer substances into cells. Water - Dipolar -Hydrogen bonds -Electrostatic attraction - high heat capacity / latent heat of vaporisation -Solvent ionic substances / colloids -Emulsions / suspensions (blood plasma / fluids) -Surface tension plant transport -amphoteric acid/base buffer Humans MTS cardiovascular system circulation blood is medium its passage through vessels is called circulation : hormones / immune system / heat distribution Blood- Plasma fibrinogen clot digested food storage excretory products hormones temperature buffer to ph Erythrocytes red blood cells biconcave disks SA:V large can diffuse- haemoglobin red bone marrow no nucleus Leucocytes white blood cells large but can change shape white bone marrow lymphocytes defend against infection [ antibodies/antitoxins > phagocytosis] Platelets megakaryocytic bone marrow blood clotting Oxygen haemoglobin 4 molecules of oxygen -concentration of oxygen when it leaves lungs is low -oxygen moves into the red blood cells from the air in the lungs by the diffusion -oxygen is picked up and bound to the haemoglobin - -the free oxygen concentration in the cytoplasm of the red blood cells -more and more oxygen diffuses in and is loaded onto the haemoglobin -in the body tissues oxygen levels are relatively low the concentration of oxygen in the cytoplasm of the red blood cells is higher than in the surrounding tissue - oxygen goes out into the body cells by diffusion down its concentration gradient - the haemoglobin molecules give up some of their oxygen -at rest only 25% is released / active other 75%

5 5 Carbon dioxide - waste carbon dioxide diffuses from the respiring cells of body tissues into the blood along a concentration gradient -the reaction of the carbon dioxide with water is crucial - when carbon dioxide is dissolved in the blood it reacts slowly with the water to form carbonic acid (H2CO3). -This then separates into H+ and HCO3-5% of the carbon dioxide is carried in solution in plasma 10-20% - combines with haemoglobin molecules to form carbaminohaemoglobin - most of the carbon dioxide is transported in the cytoplasm of the red blood cells as hydrogencarbonate ions -the enzyme carbonic anhydrase controls the rate of reaction between carbon dioxide and water to form carbonic acid - there is a high concentration of carbon dioxide in blood (in body tissues) so carbonic anhydrase catalyses the formation of carbonic acid -In the lungs the carbon dioxide concentration is low so carbonic anhydrase catalyses the reverse reaction and free carbon dioxide diffuses out of the blood into the lungs.

6 6 Structure and functions of arteries, capillaries and veins. Arteries The arteries process the transfer of blood from the heart to the rest of the body, where they branch into smaller arteries (named arterioles, which can adapt their diameter to control flow and they maintain pressure) and from here the blood is supplied through the capillaries into the tissue. Blood carried in the arteries is always oxygenated, though with the exception of the pulmonary artery which carries deoxygenated blood from the heart to the lungs. They have the highest pressure as they are closest to the ventricles of the heart. It is because of such high pressure that the arteries have a pulse that can be felt externally. Using their muscular layer they are capable of contracting, assisting the flow of blood around the body. Using the serosa they are able to secrete serosa fluid, preventing friction with tissue and other vessels. Veins Veins carry blood back to the heart via the capillaries and venules (of which many make up a vein), where they only have thin walls and the blood flowing at low pressure. Veins also contain many semi-lunar valves which prevent the backflow of the blood whilst it is circulating the body, which is important in preventing waste materials returning because of the low pressure. Such pressure is in contrast with the arteries, as the veins are a long distance from the heart and have a low amount of muscle. Veins do have a very weak and undetectable pulse because of the pressure. The blood carried is typically a dark red colour and is deoxygenated, apart from the pulmonary vein which carries oxygenated blood from the lungs to the heart. Both veins and arteries have: an outer covering of tough collagen fibres (thin in veins) tunica externa (outer coat) a middle layer of smooth muscle and elastic fibres (thin in veins) tunica media (middle coat) a lining of thin cells (endothelium / endothelial cells) capability of resuming shape after stretching/contracting using elastin (elastic tissue) lumen where the blood flows through from an artery is more narrow than that of a vein Capillaries These are very small in diameter (5-20 micro-metres) and they measure at only one endothelial cell thick. They act as a medium and allow the transfer of substances between the blood and the cells of the human body. A fluid containing plasma (with nutrients, enzymes and hormones) diffuses from the capillaries pores and into the cells, allowing the exchange of such materials. Substances transported may include salts, water, oxygen, carbon dioxide, as well as the removal of waste materials from cells. Additionally they have a high resistance to blood flow, allowing blood to slow down and giving blood pressure here as well as the arteries. The delay caused provides a more efficient exchange of chemicals at the tissues in the body.