3.3.2 gas exchange Flashcards
How do organisms with smaller SA:V ratios adapt to facilitate exchange?
- Short diffusion pathways - capillary walls only one cell thick
- Folds in the membranes of cells eg. villi and microvilli
- Maintained concentration gradient - heart pumps blood around the body so that blood in the lungs have a low concentration of oxygen, encouraging diffusion
- Proteins - protein channel and carriers facilitate diffusion and active transport
What are the five adaptations for gas exchange across the body surface of a single celled organism?
- Lagre SA:V
- short diffusion pathway
- Thin exchange surface
- Exchanges directly with the environment
- Maintenance of concentration gradient
What are the adaptations for gas exchange across the gills of fish?
- Large SA:V - many gill filaments covered with many lammellae
- Short diffusion distance - inside every lamellae is a network of capillaries and the walls of lamellae are very thin
- Maintained concentration gradient - counter current flow, water flowing over the gills is flowing in the opposite direction of the blood in the capillaries
What are the structures and adaptations for gas exchange across the tracheal system of an insect?
- Lots of spiracles join to trachea(network of internal tubes), which join to even smaller tubes called the tracheoles
- Simple diffusion, respiration maintains a concentration gradient for O2 and CO2
- Mass transport, muscles contract and release to transport gases around the organism
- When insects fly they use anaerobic respiration, this produces lactate which in the cells which lowers their water potential, so water moves via osmosis out of the trachea into the cells, lower pressure in the trachea leads to air moving into the trachea
What are the adaptations and structure for gas exchange across the leaves of dicotyledonous plants?
- Gases diffuse into the leaf via the stomata, where they enter the spongy mesophyll, which has a lot of air spaces for gas and to maintain the concentration gradient, so they can diffuse into the palisade mesophyll where photosynthesis occurs
- Stomata closes at night to reduce water loss
How are xerophytes adapted to reduce water loss?
- Curled up leaves - water evaporated gets trapped, increased humidity outside plant
- Hairs trap moisture- more humid
- stomata sunken in- also trap moisture and increase humidity
- thick cuticle to reduce evaporation
- Large network of roots to reach more water
How do terrestrial insects reduce water loss?
- waterproof exoskeleton
- Spiracles can close to reduce water loss
- Small SA:V ratio
What is the structure of the human gas exchange system ?
Trachea, branches into bronchis, which branch into bronchioles, which lead to alveoli which are found in the lungs
How does ventilation impact gas exchange in the lungs?
Inspiration:
- External intercostal muscles contract and internal intercostal muscles relax (antognistic pair)
- Diaphragm contracts
- pressure in lungs decreases, so volume increases to reduce pressure by moving air into the lungs
Expiration:
- external intercostal muscles relaxes and internal contract
- diaphragm relaxes
- pressure in lungs increase so air moves out of the lungs to decrease pressure by decreasing volume
What are the essential feature of the alveolar epithelium as a surface for gas exchange?
- Large surface area - many alveoli in the lungs
- Short diffusion distance - the epithelium is one cell thick
- Maintained concentration gradient - surrounded by capillaries which have deoxygenated blood flowing through
What is the equation for pulminary ventilation rate?
tidal volume x breathing rate
Breathing
Movement of air in and out of the lungs - ventilation
Respiration
Chemical reaction to release energy in the form of ATP
Gaseous exchange
Diffusion of oxygen from the air in the alveoli into the blood and carbon dioxide from the blood into the air in the alveoli
What’s the function of the leaves
- where photosynthesis occurs - carbon dioxide + water»_space; oxygen + glucose
- all plants need sugar to respire
- leaves transport inorganic substances to all cells in the plant via osmossi
Phloem - sieve tubes
- living cells
- no nucleus
- contain few organelles
- structural support
Phloem companion cells
- provide ATP for the transport of inorganic substances in the plant
Transport of sucrose or glucose in the phloem
- Photosynthesis occurring in the chloroplasts of leaves creates organic substances
- sucrose is actively transported into the sieve tube element using the companion cell for ATP
- The increase of sucrose in the sieve tube element lowers the water potential in the source cells
- water Exeters the sieve tube elements from the surrounding xylem vessels via osmosis
- Increased water volume in the sieve tube element increases the hydrostatic pressure causing the liquid to be forced towards the sink
- Sucrose is used in respiration at the sink or stored as insoluble starch
- More sucrose is actively transported into the sink cell causing the water potential to decrease
- osmosis of water from the serve tube element into the sink cell
- this decrease the volume of water and hydrostatic pressure in the sieve tube element
Source to sink hypothesis
- Source cell - photosynthesising leaf cell connects to the sink cell - respiring cell
- source cell has lower water potential as it contains soluble sugars so water moves in via osmosis
- sink cell has higher water potential as it is respiring and using up the soluble sugars therefore water moves out via osmosis
- Hydrostatic pressure in source cell increases and hydrostatic pressure in sink cell decreases so sugary solution is forced towards the sink cell
Affinity
Ability of haemoglobin to attract or bind oxygen
Saturation
Haemoglobin is holding the maximum amount of oxygen it can binf
Loading/ association
Binding of oxygen to haemoglobin
Unloading/dissociation
Oxygen unbinds from haemoglobin
Relationship between partial pressure and saturation of haemoglobin
Higher partial pressure - haemoglobin has a higher affininity
