Gas Exchange and Surface Area to Volume Ratio 3.1 + 3.2

    Cards (32)

    • How does an organisms size relate to its surface area to volume ratio?
      The larger the organism, the lower the surface area to volume ratio.
    • Surface area and volume of spheres and cylinders
      SphereSurface area= 4πr²Volume= 4/3πr^3CylinderSurface area= 2πrh + 2πr²Volume= πr²h
    • How does surface area to volume ratio relate to metabolic rate?
      The smaller the surface area to volume ratio, the higher the metabolic rate.
    • How might an organism adapt to compensate for a small surface area to volume ratio?
      -body parts become larger (eg elephants ears)-elongating shape-developing a special gas exchange surface
    • Essential features of an exchange surface
      -large surface area to volume ratio-short diffusion distance-selectively permeable -maintains a steep concentration gradient
    • Insect adaptions to prevent water loss
      1. Small surface area to volume ratio2. Waterproof exoskeleton made of chitin (polysaccharide)3. Spiracles (where gases can enter and exit - open and close to reduce water loss)This is why they can’t use their bodies as exchange surface
    • Three main features of an insect's gas transport system
      1. Spiracles = holes on the body’s surface which can be open and closed to allow gases in and out2. Tracheae = large tubes extending through the body, supported by rings of chitin to prevent collapsing2. Tracheoles = smaller branches dividing off to reach to every single tissue to provide oxygen and remove carbon dioxide
    • Process of gas exchange in insects
      First Method - Diffusion● Gases move in and out of the tracheae through the spiracles.● A diffusion gradient (as oxygen is used during respiration) allows oxygen to diffuse into the body tissue while waste CO2 diffuses out.● Contraction of muscles in the tracheae allows mass movement of air in and out.Second Method - Mass transport● Abdominal muscles contract and relax to move gases on massThird Method - Anaerobic Respiration● Produces lactic acid● Lowers water potential● Therefore water moves into cells via osmosis● Lower pressure in tracheoles so more air in
    • Adaptations for efficient diffusion in insects
      1. Large number of trachioles2. Short diffusion distance (thin walls)3. Steep concentration gradient (use and production of oxygen and carbon dioxide)
    • Why can't fish use their bodies as an exchange surface?
      -waterproof, impermeable outer membrane-small surface area to volume ratio
    • Two main features of a fish's gas transport system
      Gills= supported by arches (multiple projections of gill filaments), stacked up in pilesLamellae= at right angles to gill filaments, increases surface area, blood and water flow across them in opposite directions (countercurrent exchange system)
    • Explain the process of gas exchange in fish

      ● The fish opens its mouth to enable water to flow in, then closes its mouth to increase pressure. ● The water passes over the lamellae, and the oxygen diffuses into the bloodstream.Waste carbon dioxide diffuses into the water and flows back out of the gills.
    • How does the countercurrent exchange system maximise oxygen absorbed by the fish?
      1. Water and blood flow in opposite directions2. Maintains a concentration gradient as water is always next to blood with a lower concentration of oxygen3. Along whole length of gill4. Enables 80% of oxygen to be absorbed
    • Two types of fish
      Cartilaginous -no ventilation mechanism-have to keep swimming in order for oxygenated blood to flow over gills-parallel flowBony -water in through mouth-forced over gills-countercurrent flow
    • Parallel flow graph
    • Countercurrent flow graph
    • Three adaptations of a leaf that allow efficient gas exchange
      1) Thin and Flat ( short diffusion distance)2) Many small pores on underside (stomata) to allow gases to easily enter3) Air spaces (spongy mesophyll) allow gases to move around leaf (facilitating photosynthesis)
    • How do plants limit water loss while still allowing gases to be exchanged?
      Stomata regulated by guard cells to allow them to open and close as needed
    • How do plants levels of respiration and photosynthesis differ?
      - During the day, levels of photosynthesis are higher- At night, levels of respiration are higher
    • Structure of a leaf
      Waxy Cuticle: A waxy, waterproof layer which cuts down the water lost by evaporation and protects against parasitic fungiUpper epidermis: A single layer of cells that are transparent and contain no chloroplast allowing light to pass straight throughPalisade layer: Made up of palisade cells which contain chloroplasts, where most of the photosynthesis takes placeVein: Contains tubes called the xylem and phloem. The xylem brings water and salts to the leaf for photosynthesis. The phloem transports the dissolved foods awaySpongy mesophyll: consists of irregularly shaped cells with large air spaces between them allowing gas exchange (diffusion) between stomata and photosynthesising cellsLower epidermis: contains lots of tiny holes or pores called stomata at regular intervals which allow gases to diffuse in and out of the leaf
    • Similarities and differences between gas exchange in plants and insects
      Similarities 1. Obtain the gases they need from the air by diffusion down a concentration gradient2. Movement of gases is controlled by pore- like structuresDifferences 1. Insects deliver air through tubes which aren't present in leaves2. Muscle contraction in insects can assist with movement of air whereas leaves cant
    • Describe the pathway taken by air as it enters the mammalian gas exchange system
      Nasal cavity --> trachea --> bronchi --> bronchioles --> alveoli
    • The lungs diagram
    • Function of the naval cavity
      -Warms and humidifies -Goblet cells in the membrane secrete mucus which traps dust and bacteria
    • Structure and function of the trachea
      -Wide tube supported by C-shaped cartlidge to keep airway open during pressure changes-Lined ciliated epithelial cells which move mucus towards the throat to be swallowed to prevent lungs from infecfion-Carries air to bronchi
    • Structure and function of the bronchi
      -Supported by rings of cartilage -Lined by epithelial cells-Allow passage of air into the bronchioles
    • Structure and function of the bronchioles
      -Narrower than the bronchi-Not kept open by cartilage so only have muscle and elastic fibres which contract and relax during ventilation -Allow passage of air into the alveoli.
    • Features of the alveoli
      1. provide large surface area 2. wall of alveoli and wall of capillary are only 1-cell thick - short diffusion distance3. moist surface allows the gases to dissolve in water then pass in and out of the alveoli4. network of capillaries surround each alveolus5. concentration gradient between alveoli & capillary is high due to capillaries being narrow and blood flowing
    • Pulmonary surfactant
      A mixture of phospholipids and proteins that coats the alveoli and prevents them from collapsing during exhalation.
    • Process of inhalation
      -External intercostal muscles contract- Internal intercostal muscles relax- diaphragm contracts- ribs move upwards and outwards- diaphragm moves down-volume of the thorax increases
    • Process of exhalation
      -External intercostal muscles relax- Internal intercostal muscles contract- diaphragm relaxes- ribs move downwards and inwards- diaphragm moves up-volume of thorax decreases
    • Lung disease