B3.1 Gas Exchange Flashcards
Give an example of gas exchange in plants:
Redwood trees absorb CO2 for use in photosynthesis and release O2 in the process.
Give an example of an organ/organ system that provide a specialized surface area for gas exchange in both animals and plants:
- Alveoli in human lungs
- Spongy Mesophyll in Leaves
What is a gas exchange surface in mammals and aquatic organisms?
- Where cells are exposed to air in the lungs.
- Where cells are exposed to water in the gills of a fish.
What properties of a gas exchange surface ensure that exchange is rapid?
- Permeability to O2
- Large surface area in relation to organism
- Moist surface for dissolving substances
- Thin for short distance diffusion
What’s an example of a process used by large multicellular organisms to maintain concentration gradients?
Pumping
Which structure pumps blood close to gas exchange surfaces?
Dense capillary networks
Blood arriving at the gas exchange surface from the dense capillaries has a.…. O2 concentration and a.…. CO2 concentration.
Low, High, respectively.
How do fish maintain high enough concentrations of oxegyn and low enough concentrations of CO2?
They pump fresh water over their gills and then put through the gill slits. The blood flow moves opposite to this process.
What’s the airway path that air travels through?
Nose/Mouth, trachea, bronchi, broncioles.
How does the thorax create pressure changes during ventilation?
Muscle contractions in:
- The diaphragm
- Muscle in the front wall of the abdomen.
- Antagonistic external and internal intercostal muscles between the ribs.
Outline the changes in pressure and shape during inspiration:
1) External Intercostal muscles contract, diaphragm contracts and becomes flatter (moving down).
2) Rib cage moves up and out, thorax volume increases.
3) Pressure drops below atmospheric pressure.
4) Air flows inside with concentration gradient until pressure rises to atmospheric pressure.
Outline the changes in structure and pressure during expiration:
- Internal intercostal muscles contract, abdominal muscles contract and push diaphragm upwards.
- Volume of thorax decreases, pressure rises to atmospheric pressure.
- Air flows out until pressure drops below atmospheric pressure.
Lung gas exchange adaptations (1):
- Airways for ventilation - branching bronchioles ending in alveolar ducts (pack of 6 or 5 alveoli).
Lung gas exchange adaptations (2):
- About 300 mil 0.2-0.5mm alveoli in a adult lung pair, large quantity that provides surface area 40x larger than human outer surface area.
Lung gas exchange adaptations (3):
- Extensive capillary beds - surface area of basket-like networks of blood capillaries is very large.
Lung gas exchange adaptation (4):
- Short diffusion distance as lung alveolus walls and capillaries are single layers of thin cells, making the distance for O2 and CO2 diffusion less than a micrometre.
Lung gas exchange adaptation (5);
- Surfactant for moist surface, allows O2 to dissolve, and prevents alveolar walls from sticking each other.
What does the ‘ventilation rate’ refer to?
The number of time air is inhaled or exhaled per minute.
Tidal Volume
The amount of fresh air inhaled and stale air exhaled with each ventilation.
Inspiratory reserve volume (IRV)
The amount of air a person can forcefully inhale after a normal tidal exhalation.
Vital Capacity
Amount of air that can be exhaled after a maximum inhalation.
Expiratory Reserve volume (ERV)
The amount of air that can be forcefully exhaled after a normal tidal exhalation.
How is tidal volume measured?
By breathing into the spirometer 3 or more times to the check that the readings are consistent.
How is vital capacity measured?
By breathing in as deeply as possible and forcefully exhaling all air until the lungs are empty.
Outline the components of a plant leaf:
- Waxy cuticle
- Upper epidermis
- Palisade Mesophyll
- Spongy Mesophyll
- Lower epidermis
- Stoma
- Air spaces
- Veins
- Guard cells
How does the leaf waxy cuticle provide a moist surface area for gas exchange?
- It prevents water loss and movement of CO2 and O2 movement.
What type of plant cell secretes waxy cuticle?
Epidermis Cells
How does the leaf guard cell provide a moist surface area for gas exchange?
They change their shape to open or close a stoma during water stress where a plant may die from dehydration, at night when photosynthesis is not occurring,.
How does the leaf air spaces provide a moist surface area for gas exchange?
Carbon dioxide and oxygen diffuse through air spaces to cells from air.
How does the leaf spongy mesophyll provide a moist surface area for gas exchange?
It provides a very large surface area for gas exchange.
- Carbon dioxide in the airspaces dissolves and and diffuses into the cells, and 02 diffuses from the cells to the air.
How does the leaf vein provide a moist surface area for gas exchange?
It replaces the water diffused through the stomata by the water supplied by its xylem vessels.
What intermolecular force is broken when water evaporates?
Hydrogen bonds
When is the air saturated with water vapour?
When the air is very humid and and the number of molecules evaporating is equal to the number of molecules condensing.
Outline the meaning of transpiration
The loss of water vapour from the leaves and stems of plants.
Outline the PROCESS of transpiration
Water vapour molecules diffuse out of the leaf through the stoma, so the humidity in the leafs airways drops below saturation
level, so more molecules from the moist spongy mesophyll will evaporate.
What is the correlation between temperature and transpiration rates?
(POSITIVE) At higher temperatures there is more energy available to break H-bonds between molecules, so the evaporation rate is higher and the air holds more vapor molecules before becoming saturated.
What is the correlation between humidity and transpiration rates?
(NEGATIVE) The higher the humidity in the air, the smaller the water vapour concentration between the air spaces in leaves and the air outside, the lower the rate of diffusion.
What is the correlation between wind and transpiration rates?
Stomatal Density
The number of stomata per unit area of leaf surface,
What is the formula for measuring stomatal density?
mean # of stomata/area of field of view
Which pregnancy organ provides the foetus with oxegyn?
The PLACENTAA
Why does oxegyn dissociate from maternal blood to foetal blood?
Haemoglobin in feotal blood has a stronger affinity fir oxygen.
Oxygen dissociates from haemoglobin in ….. bloodn in the placenta and binds to haemoglobin in …….. blood.
Maternal, Foetal
How much time does it take for foetal haemoglobin to be replaced by adult haemoglobin?
Several months
What is the shape of a dissociation curve for haemoglobin?
Sigmoid
What is the correlation/Causation between CO2 concentrations and the affinity of haemoglobin for oxygen?
An increase in CO2 concentration means a decrease in the affinity of haemoglobin for oxegyn
What are the 2 mechanisms with which CO2 lowers haemoglobin’s affinity for oxygen?
1) Reducing pH by reacting with h2o to create bicarbonate, which decreases the affinity for oxygen.
2) Binding to haemoglobin to form carbaminohaemoglobin, which has a lower affinity for oxygen than haemoglobin,
The Bohr Shift
A shift in the oxegyn dissociation curve to the left, indicating a reduced affinity of haemoglobin for O2 in high CO2 concentrations.
How many oxegyns can 1 heme group carry? How many can one haemoglobin unit carry?
1,4, respectively.
What are the 2 most probable states for haemoglobin?
4 or none
Cooperative binding
The binding of oxygen to any haem group causes conformational changes that increase the affinity for oxygen, conversely the dissociation of oxegyn reduces the affinity in other heme groups.
Blood in which all haemoglobin molecules carry 4 oxegyns is …. saturated.
100%
Blood in which all haemoglobin molecules carry 0 oxegyns is …. saturated.
0
What is the correlation between partial pressure of oxegyn and the percentage saturation
A positive correlation, haemoglobin reaches 100% saturation when partial pressure of oxegyn reaches 10kPa.
Why does oxygen dissociate from haemoglobin and diffuses into tissues?
The partial pressure of oxygen in respiring tissues is lower than 10kPa.
