3.1.1 exchange surface
Tuesday, 14 January 2025 15:36
- All organisms require the exchange of substances with their environment (e.g. taking in
O2/glucose for metabolic reactions, excretion of waste products CO2)
- Smaller organisms have higher SA:V, greater efficiency and often they have lower metabolic
demands than larger organisms
- ! Unicellular organisms allow diffusion directly into/out of cell across the cell surface
membrane - smaller distance, quicker rate
- Multicellular organisms have slower rates of diffusion due to: some cells being deeper in
the body/further from surface and more distance, lower SA:V and therefore relatively small
exchange surface to volume, higher metabolic rate
- Specialised exchange surfaces are required for them as a result
- Features of an efficient exchange surface:
- Root hair cells have a maximised surface area, many on a root, inc rate of absorption of
water (osmosis) or mineral ions (a.t)
- Alveoli have a thin surface layer, shorter diffusion distanced through single layer of thin flat
cells (alveolar epithelium), inc rate of diffusion
- Rich blood supply and ventilation are also required: alveoli have a large capillary network,
each one having its own blood supply, lungs ventilated and air replaced - both mean conc
gradient is maintained.
- Fish gills also contain a large network of capillaries, well-ventilated through fresh water
passing over them, maintain conc gradient and inc rate of O2 diffusing
- Mammals exchange organ lungs: trachea - bronchi - each lung - bronchioles- alveoli
- Goblet cells help trap microorganisms/dust from reaching alveoli by secreting mucus
- Cilia beat mucus upwards to the throat instead of to the alveoli preventing lung infections
- Elastic fibres in the trachea, bronchi, bronchiole, alveoli’s walls help with breathing out.
Breathing in, fibres are stretched, then they recoil pushing the air out
- Smooth muscle in bronchi, trachea, bronchioles walls to control diameter/less airflow
resistance, air moves in/out more easily
- Rings of cartilage in trachea has large c-shaped pieces, bronchi has smaller pieces that are
between alternating smooth muscle tissues, provide support
- Ventilation consists of inspiration (requires energy) and expiration (passive process)
- Exploration can be forced if intercostal muscles contact and the rib cage is pulled down and
in
- Inspiration: external intercostal muscles and diaphragm muscles contract, rib cage then
moves upwards and outwards and the diaphragm flattens. This increases the volume of the
thorax (lungs area), lung pressure dec, air flows into it
- Expiration: external intercostal and diaphragm muscles relax, rib cage moves downward
and inwards, diaphragm becomes curved, thorax volume dec, lung air pressure inc, air is
forced out of the lungs
- Tidal volume is the volume of air in each breath
- Vital capacity - maximum volume of air that can be breathed in/out
- Breathing rate is how many breaths are taken, usually in a min
- Oxygen uptake is the rate at which organisms use up oxygen
- Spirometers give readings of breathing previous: have an oxygen filled chamber w movable
lid, person breathes through a tube causing lid to move up and down, movement recorded
by a pen attached to chamber lid, writing on a rotating drum creating a spirometer trace/or
spirometer is attached to a motion sensor using movements to produce electronic signals
picked up by a data logger
Fish:
- Fish take in water, with a low concentration of o2.
- The water enters the mouth, passes out via the gills - made up of gill filaments (thin
branches) inc SA For gas exchange
- These are covered by gill lamellae, very small structure that inc SA more and has many
capillaries, thin surface layer of cells to inc rate of diffusion
- Gill arches support each gill
- Across gill lamellae, blood flows in one direction and water in the other - Counter-current
system, maintaining a large conc gradient between water/blood
- Conc of oxygen in water is always higher than in blood so o2 diffuses into blood
- Mouth open and buccal cavity floor lowers, inc in BC volume, dec pressure allowing water
to be taken into it.
- When mouth closes, buccal cavity floor raised, dec in BC volume, inc pressure and water us
forced out of BC across gill filaments
- Operculum - bony flap that covers gills, protecting it. Inc pressure from mouth closing
causes it to open, allowing water to leave
- Insects have trachea used for gas exchange)
- Spiracles on insects’ surface (pores) allows air to enter into tracheae
- O2 moves down conc gradient towards cells, CO2 moves down its own conc gradient
towards spiracles
- Tracheae branch into tracheoles, thin permeable walls go towards individual cells for O2
diffusion, contains tracheal fluid that o2 dissolves in
- Use rhythmic abdominal movements to change volume of bodies and move air in/out, wing
movements can also pump thoracic movements too
- Expiration: muscles contract, flattening Body, dec body v, air forced out
- Inspiration: passive, elastic nature of body returns to original shape
- Fish dissection: labcoat/goggles, on dissection tray, push back operculum to remove gill
from gill arch
- Insect dissection: larger insect on dissecting board with dissecting pins holding it, remove
piece of exoskeleton from abdominal length. Syringe to fill with saline solution, thin grey
tubes are tracheae
- Use light microscope: wet mount slide, rings of chitin in walls of tracheae for support
Tuesday, 14 January 2025 15:36
- All organisms require the exchange of substances with their environment (e.g. taking in
O2/glucose for metabolic reactions, excretion of waste products CO2)
- Smaller organisms have higher SA:V, greater efficiency and often they have lower metabolic
demands than larger organisms
- ! Unicellular organisms allow diffusion directly into/out of cell across the cell surface
membrane - smaller distance, quicker rate
- Multicellular organisms have slower rates of diffusion due to: some cells being deeper in
the body/further from surface and more distance, lower SA:V and therefore relatively small
exchange surface to volume, higher metabolic rate
- Specialised exchange surfaces are required for them as a result
- Features of an efficient exchange surface:
- Root hair cells have a maximised surface area, many on a root, inc rate of absorption of
water (osmosis) or mineral ions (a.t)
- Alveoli have a thin surface layer, shorter diffusion distanced through single layer of thin flat
cells (alveolar epithelium), inc rate of diffusion
- Rich blood supply and ventilation are also required: alveoli have a large capillary network,
each one having its own blood supply, lungs ventilated and air replaced - both mean conc
gradient is maintained.
- Fish gills also contain a large network of capillaries, well-ventilated through fresh water
passing over them, maintain conc gradient and inc rate of O2 diffusing
- Mammals exchange organ lungs: trachea - bronchi - each lung - bronchioles- alveoli
- Goblet cells help trap microorganisms/dust from reaching alveoli by secreting mucus
- Cilia beat mucus upwards to the throat instead of to the alveoli preventing lung infections
- Elastic fibres in the trachea, bronchi, bronchiole, alveoli’s walls help with breathing out.
Breathing in, fibres are stretched, then they recoil pushing the air out
- Smooth muscle in bronchi, trachea, bronchioles walls to control diameter/less airflow
resistance, air moves in/out more easily
- Rings of cartilage in trachea has large c-shaped pieces, bronchi has smaller pieces that are
between alternating smooth muscle tissues, provide support
- Ventilation consists of inspiration (requires energy) and expiration (passive process)
- Exploration can be forced if intercostal muscles contact and the rib cage is pulled down and
in
- Inspiration: external intercostal muscles and diaphragm muscles contract, rib cage then
moves upwards and outwards and the diaphragm flattens. This increases the volume of the
thorax (lungs area), lung pressure dec, air flows into it
- Expiration: external intercostal and diaphragm muscles relax, rib cage moves downward
and inwards, diaphragm becomes curved, thorax volume dec, lung air pressure inc, air is
forced out of the lungs
- Tidal volume is the volume of air in each breath
- Vital capacity - maximum volume of air that can be breathed in/out
- Breathing rate is how many breaths are taken, usually in a min
- Oxygen uptake is the rate at which organisms use up oxygen
- Spirometers give readings of breathing previous: have an oxygen filled chamber w movable
lid, person breathes through a tube causing lid to move up and down, movement recorded
by a pen attached to chamber lid, writing on a rotating drum creating a spirometer trace/or
spirometer is attached to a motion sensor using movements to produce electronic signals
picked up by a data logger
Fish:
- Fish take in water, with a low concentration of o2.
- The water enters the mouth, passes out via the gills - made up of gill filaments (thin
branches) inc SA For gas exchange
- These are covered by gill lamellae, very small structure that inc SA more and has many
capillaries, thin surface layer of cells to inc rate of diffusion
- Gill arches support each gill
- Across gill lamellae, blood flows in one direction and water in the other - Counter-current
system, maintaining a large conc gradient between water/blood
- Conc of oxygen in water is always higher than in blood so o2 diffuses into blood
- Mouth open and buccal cavity floor lowers, inc in BC volume, dec pressure allowing water
to be taken into it.
- When mouth closes, buccal cavity floor raised, dec in BC volume, inc pressure and water us
forced out of BC across gill filaments
- Operculum - bony flap that covers gills, protecting it. Inc pressure from mouth closing
causes it to open, allowing water to leave
- Insects have trachea used for gas exchange)
- Spiracles on insects’ surface (pores) allows air to enter into tracheae
- O2 moves down conc gradient towards cells, CO2 moves down its own conc gradient
towards spiracles
- Tracheae branch into tracheoles, thin permeable walls go towards individual cells for O2
diffusion, contains tracheal fluid that o2 dissolves in
- Use rhythmic abdominal movements to change volume of bodies and move air in/out, wing
movements can also pump thoracic movements too
- Expiration: muscles contract, flattening Body, dec body v, air forced out
- Inspiration: passive, elastic nature of body returns to original shape
- Fish dissection: labcoat/goggles, on dissection tray, push back operculum to remove gill
from gill arch
- Insect dissection: larger insect on dissecting board with dissecting pins holding it, remove
piece of exoskeleton from abdominal length. Syringe to fill with saline solution, thin grey
tubes are tracheae
- Use light microscope: wet mount slide, rings of chitin in walls of tracheae for support
