Topic 3

Cards (94)

  • Surface area to volume ratio: The surface area of an organism divided by its volume the larger the organism, the smaller the ratio
  • Factors affecting gas exchange:
    • diffusion distance
    • surface area
    • concentration gradient
    • temperature
  • Ventilation:
    • Inhaling and exhaling in humans
    • controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles
  • Inspiration:
    • External intercostal muscles contract and internal relax
    • pushing ribs up and out
    • diaphragm contracts and flattens
    • air pressure in lungs drops below atmospheric pressure as lung volume increases
    • air moves in down pressure gradient
  • Expiration:
    • External intercostal muscles relax and internal contract
    • pulling ribs down and in
    • diaphragm relaxes and domes
    • air pressure in lungs increases above atmospheric pressure as lung volume decreases
    • air forced out down pressure gradient
  • Passage of gas exchange:
    • Mouth / nose -> trachea -> bronchi -> bronchioles -> alveoli
    • crosses alveolar epithelium into capillary endothelium
  • Why large organisms need specialised exchange surface?
    • They have a small surface area to volume ratio
    • higher metabolic rate - demands efficient gas exchange
    • specialised organs e.g. lungs / gills designed for exchange
  • Fish gill anatomy:
    • Fish gills are stacks of gill filaments
    • each filament is covered with gill lamellae at right angles
  • How fish gas exchange surface provides large surface area?
    • Many gill filaments covered in many gill lamellae are positioned at right angles
    • creates a large surface area for efficient diffusion
  • How tracheal system provides large surface area:
    • Highly branched tracheoles
    • large number of tracheoles
    • filled in ends of tracheoles moves into tissues during exercise so larger surface area for gas exchange
  • Fluid-filled tracheole ends:
    • Adaptation to increase movement of gases
    • when insect flies and muscles respire anaerobically - lactate produced
    • water potential of cells lowered, so water moves from tracholes to cells by osmosis
    • gases diffuse faster in air
  • How do insects limit water loss:
    • Small surface area to volume ratio
    • waterproof exoskeleton
    • spiracles can open and close to reduce water loss
    • thick waxy cuticle - increases diffusion distance so less evaporation
  • Dicotyledonous plants leaf tissues:
    • Key structures involved are mesophyll layers
    • (palisade and spongy mesophyll)
    • stomata created by guard cells
  • Gas exchange in plants:
    • Palisade mesophyll is site of photosynthesis
    • oxygen produced and carbon dioxide used creates a concentration gradient
    • oxygen diffuses through air space in spongy mesophyll and diffuse out stomata
  • Role of guard cells:
    • swell - open stomata
    • shrink - closed stomata
    • at night they shrink, reducing water loss by evaporation
  • Xerophytic plants:
    • Plants adapted to survive in dry environments with limited water (e.g. marram grass/cacti)
    • structural features for efficient gas exchange but limiting water loss
  • Adaptations of xerophyte:
    • Adaptations to trap moisture to increase humidity -> lowers water potential inside plant so less water lost via osmosis:
    • sunken stomata
    • curled leaves
    • hairs
    • thick cuticle reduces loss by evaporation
    • longer root network
  • Locations of carbohydrate digestion: Mouth -> duodenum -> ileum
  • Locations of protein digestion: Stomach -> duodenum -> ileum
  • Endopeptidases:
    • Break peptide bonds between amino acids in the middle of the chain
    • creates more ends for exopeptidases for efficient hydrolysis
  • Exopeptidases: Break peptide bonds between amino acids at the ends of polymer chain
  • Membrane-bound dipeptidases: Break peptide bond between two amino acids
  • Digestion of lipids:
    • Digestion by lipase (chemical)
    • emulsified by bile salts (physical)
    • lipase produced in pancreas
    • bile salts produced in liver and stored in gall bladder
  • Role of bile salts:
    • Emulsify lipids to form tiny droplets and micelles
    • increases surface area for lipase action - faster hydrolysis
  • Micelles: Water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts
  • Lipid absorption:
    • Micelles deliver fatty acids, glycerol and monoglycerides to epithelial cells of ileum for absorption
    • cross via simple diffusion as lipid-soluble and non-polar
  • Lipid modification:
    • Smooth ER reforms monoglycerides / fatty acids into tryglycerides
    • golgi apparatus combines tryglycerides with proteins to form vesicles called chylomicrons
  • How lipids enter blood after modification:
    • Chylomicrons move out of cell via exocytosis and enter lacteal
    • lymphatic vessels carry chylomicrons and deposit them in bloodstream
  • Glucose and amino acids are absorbed via co-transport in the ileum
  • Haemoglobin(Hb):
    • Quaternary structure protein
    • 2 alpha chains
    • 2 beta chains
    • 4 associated haem groups in each chain containing Fe2+
    • transports oxygen
  • Affinity of haemoglobin: The ability of haemoglobin to attract / bind to oxygen
  • Saturation of haemoglobin: When haemoglobin is holding the maximum amount of oxygen it can hold
  • Loading / unloading of haemoglobin:
    • Binding/detachment of oxygen to haemoglobin
    • also known as association and disassociation
  • Oxyhaemoglobin dissociation curve:
    • oxygen is loaded in regions with high partial pressures (alveoli)
    • unloaded in regions of low partial pressure (respiring tissue)
  • Oxyhaemoglobin dissociation curve shifting left:
    • Hb would have a higher affinity for oxygen
    • load more at the same partial pressure
    • becomes more saturated adaptation in low-oxygen environments
    • e.g. llamas/ in foetuses
  • Bohr effect:
    • High carbon dioxide partial pressure
    • causes oxyhaemoglobin curve to shift to the right
  • Oxyhaemoglobin dissociation curve shifting right:
    • Hb has lower affinity for oxygen
    • unloads more at the same partial pressures
    • less saturated
    • present in animals with faster metabolisms that need more oxygen for respiration e.g. birds/rodents
  • Closed circulatory system: Blood remains within blood vessels
  • Name different types of blood vessels: Arteries, arterioles, capillaries, venules and veins
  • Capillary endothelium:
    • Extremely thin
    • one cell thick
    • contains small gaps for small molecules to pass through (e.g. glucose, oxygen)