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Gas Exchange

Gas Exchange. Metabolic Pathways: Glycolysis. Glucose ( Lactate ) Pyruvate TCA. 2ATP (without O 2 ). 36ATP (with O 2 ). TCA. Metabolic Pathways: anaerobic.

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Gas Exchange

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  1. Gas Exchange

  2. Metabolic Pathways: Glycolysis Glucose ( Lactate ) Pyruvate TCA 2ATP (without O2 ) 36ATP (with O2) TCA

  3. Metabolic Pathways: anaerobic • Lactate pathway – rapid but inefficient conversion of pyruvate to lactate – used for burst work (muscle tissue temporarily. out of O2) 3ATP/pyruvate • Opine pathway – rapid but inefficient – used for burst work 3ATP/glucose (Opine is a class of amino acid derivitives, slightly different ones in different organisms e.g. Octopine in Octopoids, Strombine in some bivalves) • Succinate pathway – slower but more efficient than above – used in animals living in anoxic environments (e.g. bivalves in anoxic mud flats, endoparasites in anoxic parts of hosts) 4-6 ATP/glucose • Phosphogens – not a pathway but a class of phosphoamino acids that can store energy from ATP during periods of relaxation and deliver it under conditions of anoxia or exhaustion (phosphoarginine in invertes. phosphocreatine in verts. , echinoderms have both, annelids have 4 others)

  4. Gas exchange In order for gas to diffuse across a membrane it must be in solution. Therefore gas exchange surfaces must remain moist.

  5. Oxygen Diffusion • Organisms that live in aquatic, marine, or even moist terrestrial environments and which have all tissues within 1 mm of the moist integument, do not have specialized gas exchange structures nor do they require a circulatory system to transport oxygen. In some, such as nemertean worms a circulatory system exists that functions to carry nutrients from the gut to other tissues. • Larger organisms and organisms living in low oxygen environments have evolved such structures and circulatory systems. The diffusion of O2 across such surfaces is most efficient where the medium is in motion and the underlying circulatory fluid is also in motion especially if it is moving in the opposite direction

  6. Oxygen Transport • Water is not an efficient O2 carrier – compounds have evolved that bind O but will give it up easily - Respiratory Pigments: • Haemoglobins - iron containing – in solution or in cells – common among invertebrates. • Haemocyanins – copper containing – in solution only – molluscs and some arthropods. • Haemerythrins – iron containing – in cells – more storage than transport – some polychaetes, sipunculans, brachiopods • Chlorocruorins – iron containing – in solution – some polychaetes

  7. Mollusca: Bivalve Ctenidium

  8. Mollusca: Generalized Circulatory System

  9. Mollusca

  10. Annelida: Polychaetes • Parapodia as multipurpose structures

  11. Adaptations: Snorkel Worm

  12. Annelida: Oligochaetes, the Earthworm

  13. Echinoderms: Echinoids • Note the currents in sea water, water vascular system and the haemal system containing coelomic fluid moved by ciliary action allow gas exchange across podia and ampullae.

  14. Crustacea

  15. Hexapoda – Tracheal System

  16. Myriapoda

  17. Cheliceriformes Horseshoe crab Spider

  18. Dealing with Change in O2 Availability oxyregulator high Pc O O2 uptake oxyconformer low high low Ambient O2 Tension (pressure of O2)

  19. Dealing with Changes in O2 Availability • Oxyconformer –reduces or increase uptake to match availability can chnage metabolic activity and/or switch to succinate pathway – usually found in organisms living in environments that seldom fall very low in O2 tension or do so in a regular predictable way. • Oxyregulators – maintain uptake despite changes in availability may change ventilation of gas exchange structures, change blood flow and volume, change synthesis of respiratory pigments – usually found in organisms living in environments which experience occasional and unpredictable changes in O2 tension. • Organisms vary in their ability to conform or regulate – thus react differently to human induced changes in O2 tension. E.g. Tubifex sp. and Asellus sp increase ventillation and respiratory pigment and survive in polluted freshwaters where Hydra, and some crustaceans can’t survive.

  20. SOD • Too much O in tissues can be harmful by forming superoxide radicals that denature macromolecules. This a potentially serious problem for organisms that harbor symbiotic algae in their cells. • Many cnidarians and giant clams have evolved a system whereby they synthesize superoxide dismutase (SOD) an enzyme that eliminates superoxide radicals

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