B8 Flashcards
Why do organisms need to transport substances in and out including oxygen, carbon dioxide, water, dissolved food molecules, mineral ions and urea
-For respiration(O2) and CO2 out as a waste product by diffusion.
-Water taken in by osmosis, while dissolved food molecules and mineral ions diffuse along with it.
-Urea diffuses from cells to blood plasma for removal from the kidneys.
Need for exchange surfaces and transport system in multicellular organisms
In single-cellular organisms, gases and dissolved substances diffuse directly into cell across membrane(because of large surface area compared to volume so enough substance can be exchanged across membrane to supply volume of cell).
-Multicellular organisms have smaller surface area to volume so harder to exchange enough substance for entire volume across outside surface alone. Need exchange surface for efficient diffusion a mass transport system to move substances between exchange surfaces and rest of body. These surfaces are adapted to maximise effectiveness and allow enough of necessary substance through.
Surface area to volume ratio calc
Calculate surface area and volume and put it in a ratio in that order. Larger an organism-the smaller its surface area compared to volume meaning less effective exchange of substances because surface area is smaller.
How alveoli are adapted to gas exchange by diffusion between air in lungs and blood in capillaries
-Blood arriving at alveoli has just returned from the rest of the body so lots of CO2 and little O2.
-Maximises conc gradient for diffusion of both.
-O2 diffuses out of alveoli(where O2 conco is high) into blood (O2 conc low) and vice versa for CO2.
-specialised to maximise diffusion by;
-moist lining for dissolving gases
-Good blood supply to maintain conc grads of CO2 and O2
-very thin walls-minimises distance gases have to move
-Enormous surface area(75m^2 in humans)
-gases diffuse across membranes of the cells that make up walls of capillary and alveolus. Partially permeable.
How alveoli are adapted to gas exchange by diffusion between air in lungs and blood in capillaries
-Blood arriving at alveoli has just returned from the rest of the body so lots of CO2 and little O2.
-Maximises conc gradient for diffusion of both.
-O2 diffuses out of alveoli(where O2 conco is high) into blood (O2 conc low) and vice versa for CO2.
-specialised to maximise diffusion by;
-moist lining for dissolving gases
-Good blood supply to maintain conc grads of CO2 and O2
-very thin walls-minimises distance gases have to move
-Enormous surface area(75m^2 in humans)
-gases diffuse across membranes of the cells that make up walls of capillary and alveolus. Partially permeable.
Factors affecting rate of diffusion
-Distance(quicker diffusion when less far to move)
-Conc difference(grad)-diffuse faster if there is a bigger diff in conc between area diffusing from and to. More particles on one side=more there to move across.
Surface area-More surface area, more available for molecules to move across, faster they can get from one side to another.
Rate of diffusion calc(Fick’s law)
rate of diffusion is directly proportional to; surface area x concentration difference/thickness of membrane
How structure of blood is related to function:
-red blood cells(ethryrocytes)
-White blood cells(phagocytes and lymphocytes)
-plasma
-platelets
Red blood cells-carry oxygen from lungs to all cells in body. Biconcave disc shape to give large surface area for absorption of O2. No nucleus-more room to carry oxygen. Haemoglobin(red pigment) contains iron. In lungs haemoglobin binds to O2 to become oxyhaemoglobin. In body tissues reverse happens ( oxh splits up into h and O2 to release O2 to cells). More red blood cells=more oxygen can get to cells. High altitude=less O2 so people produce more red blood cells to compensate.
White blood cells(same q continued)
Phagocytes are white blood cells that change shape to engulf unwelcome microorganisms(pathogens)-phagocytosis.
Lymphocytes produce antibodies against microorganisms. Some produce antitoxins to neutralise toxins produced by your microorganisms. When have infection, white blood cells multiply to fight it off-blood test show high white blood cell count.Have a nucleus.
Plasma
Pale-straw coloured liquid carrying;
-red and white blood cells and platelets
-Nutrients like glucose and amino acids. Soluble products of digestion absorbed from gut and taken to body cells.
-CO2 from organs to lungs.
-Urea from liver to kidneys.
-Hormones.
-Proteins.
-Antibodies and antitoxins produced by white blood cells.
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Platelets
Small fragments of cells. No nucleus. Help to clot blood at wounds- stop blood pouring out, stop microorgansims getting in. (float about waiting for accidents to happen). Lack of platelets can cause excessive bleeding and bruising.
How structure of blood vessels are related to function
Arteries- carry oxygenated blood away from the heart to the rest of the body. Heart pumps blood out at high pressure so artery walls are strong and elastic. Thick walls compared to size of hole down the middle(lumen). Contain thick layers of muscle to make strong and elastic fibres to allow stretch and spring back.
Capillaries- involved in exchange of materials at tissues between the blood and tissue cells. Arteries branch into capilleries. Really tiny-too small to see. Very narrow so can squeeze into gaps between cells. They carry blood really close to every cell in body to exchange substances with them. Permeable walls so substances can diffuse in and out. Supply food and O2 and take away waste like CO2. Usually one cell thick walls. Increases rate of diffusion by decreasing distance over which occurs. Very small lumen and nucleus of cell there.
Veins- carry deoxygenated blood to the heart. Capilleries eventually join up to form veins. Blood at lower pressure in veins so walls dont need to be as thick as artery walls. Bigger lumen than arteries to help blood flow despite lower pressure. Valves to help keep blood flowing in right direction. Elastic fibres and smooth muscle and large lumen.
Double circulatory system in mammals
-heart pumps deox blood to lungs to take in O2. Ox blood returns to heart. Second circuit- heart pumps ox blood around all other organs of body to deliver ox to body cells. De ox blood returns to heart. Single circulatory systems in fish (single circuit).
Structure of heart and circulatory system relating to function including;
-roles of major blood vessels
-valves
-relative thickness of chamber walls
-Right atrium of heart receives deox blood from body through vena cava.
-Deox blood moves through to the right ventricle which pumps it to the lungs via pulmonary artery.
-Left atrium receives ox blood from lungs through pulmonary vein.
-Ox blood then moves through left ventricle which pumps it out round the whole body via aorta.
-Left ventricle has much thicker wall than right. Needs more muscle because has to pump blood round whole body at high pressure whereas right only has to pump it to lungs.
Valves-prevent back flow of blood in heart.
Cardiac output equation
Total volume blood pumped out by heart every min.
output(cm^3 min^-1)=heart rate(bpm) x stroke volume(cm^3)
