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Form 4 Biology Chapter 7 - Respiration

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Form 4 Biology Chapter 7 - Respiration
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  Chapter 7 : Respiration 1 7.1   Respiratory process 7.1.1   Energy for living processes 1.   All living processes require energy. a)   Movements (muscle contractions, movement of chromosomes, cell movements)   b)   Catalytic processes (break up complex molecules  –   release energy)  c)   Anabolic processes (build up complex molecules ; build new cells)  d)   Maintaining constant body temperature (generate heat energy to maintain optimum internal environment)  e)   Active transport (across plasma membrane against concentration gradient)  f)   Secretions (enzymes and mucus  –   secreted, packaged, transported)  2.   Energy is a)   locked up as chemical bonds (as chemical energy)  in organic food molecules (mainly carbohydrates)   b)   released during oxidation of food substances in mitochondria of cells c)   supplied in the form that can be used by body cells (ATP)  3.   Respiration = oxidation of food substances in the mitochondria of cells to release energy 7.1.2   Main substrate (reactants) for energy production 1.   Main substrate (primary energy source)   >> glucose    In plants, i.   glucose molecules are synthesised from H 2 O and CO 2 during  photosynthesis (in chlorophyll with the presence of sunlight)  ii.   some glucose molecules >>  oxidised by plant to produce energy iii.   extra glucose molecules   >>  converted to   startch/a.a (food reserves)      In other heterotrophs  (cannot synthesise food, only feed on others) , i.   glucose molecules are obtained from the digestion of complex carbohydrates in their food 2.   Other substrate (secondary energy sources)   >> proteins, fats    Must be converted to glucose in liver to produce energy 7.1.3   Types of respiration Respiration Aerobic respiration Anaerobic respiration Cell respiration Gaseous exchange  Chapter 7 : Respiration 2 Aerobic respiration   (respiration that uses oxygen) Breakdown of glucose to produce energy in the presence of oxygen   i.   Breakdown of glucose is complete (release useful ATP    +   body heat)  ii.   Release more energy than anaerobic resp. >> more efficient (A)   Gaseous exchange (external respiration / breathing)  i.   Involve mechanical process of inhalation  and exhalation  of air into and out of our lungs ii.   Transfer oxygen from surrounding medium (air & H  2 O)  to cells iii.   Eliminate products of respiration (CO 2  & H  2 O) to surrounding medium (B)   Cell respiration (internal respiration / tissue respiration)  i.   Involve oxidation of glucose molecules to produce E, CO 2 , H 2 O ii.   Site : mitochondria of living cells (plants and animals)  Energy production from glucose 1.   Glucose is gradually oxidised in a series of enzyme-catalysed reactions. 2.   Some energy is lost as body heat Some energy is used to synthesise ATP molecules (energy store)  3.   Synthesis of ATP  (store energy in A-P-P~P chemical bond)      Add 3 rd  P to ADP using energy from oxidation of glucose    1 glucose molecule   2898kJ energy   38ATP + body heat 4.   Breaking up of ATP (releases energy stored in A-P-P~P bond)      Separated ADP and P is recycled back to an ATP using energy from oxidation of glucose. Anaerobic respiration   (respiration that takes place in the absence of oxygen) Breakdown of glucose to produce energy in the absence of oxygen i.   Breakdown of glucose is incomplete ii.   Only release a small amount of energy >> inefficient (A)   In animals (human muscle cell)  –     produce lactic acid and energy Vigorous activity    Muscle cells contract repeatedly and rapidly    Demand for oxygen increases    Oxygen consumption exceeds oxygen supply Anaerobic respiration takes place    In the absence of oxygen, glucose is broken down into lactic acid and energy (150kJ)      Energy is used to synthesise 2ATP (from 2ADP + 2P)   Oxygen debt (build-up of lactic acid in muscles)      Lactic acid : toxic, cause muscle fatigue, pain & cramps   Lungs    Continuous deep & rapid breathing : repay oxygen debt    Lactic acid is transported from muscles to liver Liver      lactic acid is oxidised to produce energy (2ATP)      Energy converts   lactic acid back to glucose    Muscles    Glucose returns to muscles    Excess glucose is converted to glycogen for storage  Chapter 7 : Respiration 3 (B)   In yeast  (fungi)  and plants  –   produce ethanol, CO 2  and energy a)   Anaerobic respiration in yeast = alcohol fermentation    Used in bread, beer and wine production  b)   In the absence of oxygen, yeast produces enzyme zymase  to catalyse conversion of ethanol, CO 2  and energy c)   Only small amount of energy from glucose is released. The rest of energy : store in chemical bonds of ethanol Similarities    Both are cellular respiration    Both break up glucose molecules (catabolism)    Both produce ATP molecules (anabolism)    Both take place in living organisms (animal and plant cells)    Both produce heat energy as by-product    Involve energy expenditure Differences Aerobic respiration Aspect Anaerobic respiration Required Oxygen requirement  Not required Complete Breakdown of glucose Incomplete CO 2  + H 2 O Products Yeast : CO 2  + ethanol ; Muscle cells   :   lactic acid   Large amount (2880 kJ)   Energy produced per glucose molecule Small amount (210 kJ in fermentation 150 kJ in muscle cell)  32  –   38 molecules Number of ATP produced per glucose molecule 2 molecules of ATP In cell mitochondria Location In cell cytoplasm  Chapter 7 : Respiration 4 7.2   Respiratory structures and breathing mechanisms 7.2.1   Respiratory structures and adaptations 1.   Breathing    Involve pumping movements to ventilate the respiratory surface i.   In humans, chest movements  –   inflate and deflate lungs ii.   In fish, mouth movements  –   allow water to pass over gills    To maximise the process of gaseous exchange    Only take place in complex organism (amoeba, planarian, earthworm)  2.   Respiratory structure    organisation and arrangement of different parts of a respiratory system (to be well adapted for gaseous exchange) 3.   Respiratory surface / membrane    thin and moist membrane that allows oxygen to diffuses into the  body and carbon dioxide to diffuses out of the body    Adaptations of respiratory surfaces i.   Large surface area o   maximise the exchange of gases ii.   Moist respiratory surface o   diffuse gases in fluid   (before diffusing across resp. surface)  iii.   Thin respiratory surface (one-cell thick)   o   for effective diffusion of gases iv.    Network of blood capillaries (beneath respiratory surface)   o    provide a rich blood supply to transport gases to and from respiratory surface (except protozoa and insects)   Surface area : Volume Ratio (    ; SA/V) 1.   SA/V ratio = surface area available for gaseous exchange per unit volume of organism’s body  2.   For small organisms (planarians ; protozoa  –   amoeba, paramecium)      Respiratory surface = body surface    Has high SA/V ratio >> high rate of gaseous diffusion (sustain life)      Respiratory surface area is large enough for efficient diffusion of gaseous through its body volume >> to sustain life 3.   For large organisms (mammals)      Has low SA/V >> low rate of gaseous diffusion (cannot sustain life)      Cannot exchange gas by simple diffusion through body surface    Has developed specific respiratory structures (trachea, gills, lungs)      C ontain large respiratory surface areas   (for effective gaseous exchange)  i.   In fish  –   filaments and lamellae ii.   In amphibians and mammals  –   air sacs or alveoli in lungs
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