substance exchange

    Cards (80)

    • Surface area to volume ratio
      Formula: Surface area / Volume. Relationship between organism size/shape and this ratio
    • Small organisms
      • Have very large surface area compared to volume, so can meet needs through simple diffusion
    • Larger organisms
      • Have smaller surface area compared to volume, so need adaptations for mass transport and efficient exchange
    • Key adaptations for exchange surfaces
      • Villi and microvilli (small intestine)
      • Alveoli and bronchioles (lungs)
      • Spiracles and tracheae (insects)
      • Gill filaments and lamellae (fish)
      • Stomata (plants)
    • Breathing
      Movement of air in and out of the lungs
    • Respiration
      Chemical reaction that results in release of energy in the form of ATP
    • Ventilation
      Scientific term for breathing
    • Gas exchange
      Diffusion of oxygen and carbon dioxide in and out of cells
    • Key structures of human gas exchange system
      • Alveoli
      • Bronchioles
      • Bronchi
      • Trachea
      • Lungs
    • Human ventilation
      1. Diaphragm muscle contracts
      2. External intercostal muscles contract, internal intercostal muscles relax
      3. Rib cage moves out, volume increases, pressure decreases, air flows in (inspiration)
      4. Diaphragm muscle relaxes
      5. External intercostal muscles relax, internal intercostal muscles contract
      6. Rib cage moves in, volume decreases, pressure increases, air flows out (expiration)
    • Pulmonary ventilation
      Total volume of air moved into the lungs per minute
    • Alveolar epithelium
      • Very thin to minimize diffusion distance
      • Surrounded by capillary network to maintain concentration gradients
    • Terrestrial insect gas exchange
      • Tracheal system with spiracles, tracheae, and tracheoles
      • Gases can diffuse in, mass transport by abdominal muscle contraction, and drawing in air during flight
    • Terrestrial insect adaptations to limit water loss
      • Small surface area for gas exchange
      • Spiracles can open and close like plant stomata
    • Fish gills
      • Large surface area with many gill filaments and lamellae
      • Short diffusion distance due to capillary network
      • Counter-current flow mechanism maintains concentration gradient
    • Leaf gas exchange
      • Palisade and spongy mesophyll tissue
      • Stomata open during the day, close at night to reduce water loss
    • Wing in opposite directions which means you should never actually have equilibrium and there will always be a higher concentration of oxygen in the water compared to the blood and that is why we maintain the concentration or the diffusion gradient across the entire gill lamellae
    • Structures in the leaf
      • Palisade mesophyll
      • Spongy mesophyll
      • Stomata
    • Palisade mesophyll

      Where photosynthesis mainly happens
    • Spongy mesophyll
      Lots of air spaces
    • Stomata
      Where gases diffuse in and out
    • Oxygen diffuses out of stomata
      If not being used in respiration
    • Carbon dioxide diffuses in through stomata
      Because it's needed for photosynthesis
    • Stomata close at night
      To reduce water loss by evaporation
    • Stomata open in the daytime
      When it's bright
    • This is linked to the light-dependent reaction of photosynthesis
    • Adaptations of xerophytic plants to minimise water loss
      • Leaves roll up
      • Stomata are deep and sunken in
      • Tiny hairs sticking out
      • Thicker cuticle
      • Longer root network
    • Digestion
      Large biological molecules are hydrolyzed into smaller soluble molecules which can be absorbed across the cell membranes
    • Biological molecules digested
      • Carbohydrates
      • Lipids
      • Proteins
    • Carbohydrate digestion
      1. Amylase in mouth
      2. Amylase in duodenum hydrolyzes polysaccharides to maltose
      3. Sucrase and lactase hydrolyze disaccharides to monosaccharides
    • Protein digestion
      1. Endopeptidases hydrolyze peptide bonds in the middle of the chain
      2. Exopeptidases hydrolyze peptide bonds at the ends of the chain
      3. Dipeptidase hydrolyzes dipeptides
    • Lipid digestion
      1. Lipase hydrolyzes ester bonds in triglycerides
      2. Bile salts emulsify lipids to form micelles
    • Micelle
      Vesicle formed of fatty acids, glycerol, monoglycerides and bile salts
    • Lipid absorption
      1. Monoglycerides and fatty acids diffuse across cell membrane
      2. Reassembled into triglycerides in ER and Golgi
      3. Packaged into vesicles and released into lacteals
    • Ileum adaptations for absorption
      • Covered in villi and microvilli
      • Thin walls
      • Network of capillaries
    • Co-transport
      Monosaccharides and amino acids absorbed by active transport due to higher concentration in epithelial cells
    • Hemoglobin
      Quaternary structure protein involved in oxygen transport
    • Myoglobin
      Hemoglobin found in muscle tissue and fetuses
    • Oxyhemoglobin dissociation curve
      Shows how hemoglobin binds and releases oxygen at different partial pressures
    • Oxygen loading
      Occurs in regions with high partial pressure of oxygen, e.g. alveoli
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