Presentation on theme: "Module 2 Exchange & Transport. Special Exchange Surfaces Living organisms must be able to take in or remove substances To do this they need specialised."— Presentation transcript:
Special Exchange Surfaces Living organisms must be able to take in or remove substances To do this they need specialised exchange surfaces
Organisms must take in: Substance for Organisms must remove: Substance source Exchange surfaces in living organisms Organ exchange surface substances exchanged Exchange surface characteristics:
Organisms must take in: Substance: Oxygen Glucose Amino acids Lipids Mineral ions Water For: Aerobic respiration Respiration/energy source To make proteins for growth & repair Make membranes and store energy Various solvent
Organisms must remove: Substance: Carbon dioxide Oxygen Urea/ammonia From: A waste product of cell respiration A waste product of plant cell photosynthesis Nitrogenous waste from breakdown of protein
Exchange surface characteristics Large surface area Thin barrier for faster diffusion Moist to allow molecules to dissolve so they can diffuse Maintain a steep concentration gradient across the barrier To do this ensure fresh supply of molecules arrives and removal of the molecule on the other side.This means exchange surfaces often have a good blood supply Sometimes Active transport proteins in the membranes to pump materials across
Surface area/Volume ratio: cube animals Cube size(cm)Surface area (cm 2 )Cube volume (cm 3 )Surface area/volume ratio 1 2 3 4 5 1.Plot a graph of this data 2.What pattern is shown? 3.How does this information link to the need for a specialised exchange surfaces and transport systems in organisms?
Proof is in the pudding You will get 3 squares of jelly 1 of them you will keep whole 1 of them you will cut in half The last you will need to cut into quarters With each one you will need to drop into to a beaker containing 50ml of just boiled water Make a note of how long it takes each one to dissolve What are your conclusions about the rates of reaction?
Examples of specialised exchange surfaces Single celled organisms Their exchange surface is their outer membrane They have a large surface area/volume ratio This allows materials to enter and leave by diffusion
Small organisms Such as jellyfish, flatworms and true worms They also have large SA/V ratios and can still exchange some materials through their outer skin
Large Organisms As animals and plants get larger their SA / V ratio gets smaller and they can no longer rely on diffusion through their outside layer They will need specialised organs as exchange surfaces
Specialised exchange surfaces in larger organisms Lungs, gills for gaseous exchange Small intestines for exchange of nutrients with the blood Roots of plants for exchange of water & minerals Hyphae of fungi for absorbing nutrients Liver for exchange of glucose and other nutrients with the blood Kidney for reabsorption of useful molecules back into the blood
Airways Trachea Leads from the throat to the lungs Lined with ciliated epithelium Glands in the wall also secrete mucus Protected from collapse & supported by C shaped cartilage rings Cartilage is a tough,hard tissue as well as being slightly flexible
Ciliated epithelium Much of the airways are lined with this tissue May look like several layers,but each reaches the basement membrane. (Pseudostratified epithelium) In goblet cells the end nearest the membrane is thin,and widens at the top like a goblet The top part is full of mucus secreted by the cell Mucus is a slimy solution of mucin,contains glyocoprotein & carbohydrate. It is sticky and traps particles (bacteria, pollen, dust etc) It keeps the surface moist Basement membrane Goblet cell
Ciliated epithelium In between the goblet cells are columnar ciliated epithelial cells The cilia beat carrying a carpet of mucus upwards Speed about 1cm/minute At the top of the trachea the mucus is swallowed and destroyed by the stomach acid along with any pathogens
Bronchi At the base of the trachea are 2 bronchi,one leading to each lung They subdivide and branch forming the bronchial tree. Lined with ciliated epithelium,but less goblet cells Cartilage is in irregular blocks not rings so allowing more flexibility Also contains elastic fibres and smooth muscle
Bronchioles The bronchi divide into smaller and smaller tubes: Bronchiole -terminal bronchioles – respiratory bronchiole – alveolar duct No cartilage, no goblet cells Walls contains smooth muscle which can contract to narrow the airway (lack of cartilage allows this) This can reduce flow of air to alveoli and is a reflex action to protect against harmful substances in the air Allergic reactions, asthma etc When the smooth muscle relaxes airway widens due to recoil of elastic tissues
Alveoli Structure & Function Alveolus wall- very thin for easy exchange of gases Alveolus-millions give large surface area Blood capillary- good blood supply removes O 2 and brings CO 2 Air moved in and out by breathing(ventilation)
Alveoli Gaseous exchange surface in mammals Moist lining to dissolve gases Very thin single cell thick lining of epithelial cells Surrounded by very thin blood capillaries walls one cell thick. low blood pressure so very slow flow of RBCs RBCs only just fit through and are pressed against the capillary wall to lower diffusion distance Blood removes oxygen from and brings carbon dioxide to the alveoli, maintaining a steep concentration gradient Very short distance from blood to alveoli(2-4µm) Total surface area 70m 2 All leads to rapid and efficient diffusion of CO 2 & O 2 Contain elastic fibres so alveoli can stretch when inhaling (increase area more), recoil after, and push air out Surfactant chemical lowers surface tension and stops alveoli collapsing
Gaseous Exchange surfaces Produce a set of powerpoint slides to: Explain the characteristics of an exchange surface A slide each on how this is achieved in the following organisms: Bony fish Land snail Insect Plant
Breathing Breathing or ventilation renews the air inside the alveoli(bringing fresh O 2 and removing CO 2 Maintains a concentration gradient so oxygen and carbon dioxide can diffuse in and out of the blood At rest need to ventilate 6.0dm 3 /minute of air into the lungs Only about 1/7 th of air in the alveoli is changed with each breath This means composition of gases in the alveoli stays constant and aids gaseous exchange
Breathing rate The depth and rate of breathing varies with our level of activity The rate of breathing is called the ventilation rate Depth of breathing is the amount of air taken in with each breath These can be measured using a spirometer.
Using the spirometer The air in the air chamber is breathed in and out This causes the float to rise up(expiring) and down(inspiring) This movement can be recorded by a pen on a kymograph drum or by computer sensors The kymograph paper can be calibrated for time and volume Sterile mouthpiece must be used Nose clip ensures breathing through mouth only The air chamber can be used with normal air for a limited time For longer use it must be filled with medical grade oxygen and a carbon dioxide absorber such as soda lime used(why?)
Tidal volume The volume of air breathed in (or out) in one breath Breathing rate Number of breaths /minute Ventilation rate Total volume of air breathed in and out in one minute Vital capacity The largest volume of air you can breathe in and out in one breath Inspiratory reserve volume Extra air above the tidal volume you breathe in when deeply filling your lungs Expiratory reserve volume Extra air you breathe out when emptying your lunmgs Residual capacity Air that you cannot empty from your lungs Total capacity Equals VC + RC
Measuring oxygen consumption Use soda lime to absorb the exhaled CO 2 The trace will gradually fall as the breathed air volume in the chamber reduces Measure how much the trace drops in a set time Work out the volume of O 2 consumed/minute Trace drops 0.5dm 3 in 55s 500cm 3 in 55s 500/55 = 9.1cm 3 /s 9.1 x 60 = 546cm 3 /min
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