B3.1 Flashcards
Gas Exchange
Gas Exchange in Animals
Gas Exchange
Driven by diffusion of molecules from high conc. to their low conc across an exchange surface.
Gas Exchange in Animals
Concentration Gradients
The difference in conc. of substances between locations - needed for diffusion to occur.
Gas Exchange in Animals
Aveolus
- Located in lungs, microscopic spheres (aveoli) of 1 cell thick, tissue wall bubbles.
- Covered in capillary blood supply
Gas Exchange in Animals
Surfactant
- Lines the inner surface of each alveolus.
- Is a phospolipid & protein monolayer film.
- Made by type 2 pnuemocyes
- Helps keep alveoli open and expanded for gas exchange.
- Surrounds wall of aveoli with phospholipid tails facing up, meaning aveoli’s walls won’t stick during an exhale, reduces surface tension that could cause H2O behind the surfactant to lead to lung collapse.
Gas Exchange in Animals
Bronchioles
- Air travels down a single tube (trachea) which then divies into 2 bronchi that travel to the lung.
- Bronchi then divide into many small tubes with the alveoli at the end of them (best way to deliver air)
- These small tubes are bronchioles.
Gas Exchange in Animals
Properties of Gas Exchange Surfaces
- Very thin (ideally 1 cell thick) for short distances.
- Moist for gases to dissolve.
- Large SA:V ratio for more rapid diffusion.
- Higher permeability of membrances.
Gas Exchange in Animals
SA:V of Large vs Small Organisms
- Larger animals have larger volumes, constituting for larger no. interior cells that are far removed from the external environment.
- Larger organisms and their low SA:V ratio prevent cell exchange directly with environment, thus have organs to obtain and transport gasses.
Gas Exchange in Animals
Conc. Gradients in Fish
- Fish swallow water, and thus dissolved oxygen.
- They pump this oxygen over thier gills which have blood supply running through them.
- Water moves along the gills with a higher conc. gradient than the blood travelling in the oxygen direction.
- Water maintains high oxygen conc. in the alveoli than the blood of the gills, causing O2 to diffuse into them (capillaries).
- This is done by ventilation, as O2 conc. drops, fish exhale and replace when the CO2 levels rise in blood.
Gas Exchange in Animals
Conc. Gradients in Land Animals
- Each alveolar wall is 1 cell thick & surrounded by a capillary, whose wall is also 1 cell thick.
- Allows for short distance for efficient diffusion.
- Many small alveoli allows for higher SA:V, and increases blood supply access.
- Surfactant prevents alveoli walls from attracting and collapsing it.
Ventilation
What is Ventiliation?
- Exchange of air between the lungs and the environment.
- Inhalation brings in O2, exhalation releases CO2.
- Frequent ventiliation maintains conc. gradients.
Ventilation
Inspiration?
- Process of inhalation
1. Based on CO2 levels, the Diaphragm is signalled to contract.
2. At the same time, external intercostal muscles signalled to contract, pulling up and out.
3. Lung volume increases.
4. Due to Boyle’s law (increased pressure correspond to decreased volume and vice versa), pressure drops in lungs.
5. Air moves in since outside air pressure is higher.
Ventilation
Expiration
- Process of Exhalation.
1. Diaphragm relaxes, pulling back up.
2. External Intercostel muscle relaxes, pulling in and down. Intercostal mucle can contract further pulling the ribs down (a big exhale)
3. Lung Volume decreases.
4. Lung pressure increases.
5. Air is pushed out the airway.
Ventilation
Diaphragm
- A thin, dome shaped mucle that sits below the lungs.
- Attatched to the lungs, rib cage and spine.
- The contraction & relaxtion of the diaphragm enables volume of the lung to change and faciliate breathing.
Ventilation
Patrial Vacuum
- Change in pressure, when the lungs increase in volume which causes a decrease in pressure due to the change of volume.
- Causes air to move into the lungs from the environment.
Ventilation
Spirometer
- Measures the amount of air breathed in and out & how quickly you breathe out.
Ventilation
Tidal Volume
- The volume of fresh air that is inhaled and exhaled during a typical resting breathing pattern.
- Not a maximum potentional of our lungs.
Ventilation
Inspiratory Reserve Volume
- Volume of air that a person could inhale forefully beyond the normal tidal volume.
Ventilation
Expiratory Reserve Volume
- The volume of air we could exhale beyond the normal tidal volume.
- Not as lage as the inspiratory volume as we retain a small residual volume after a large inhale –> protective way to retain some air in lungs at all times.
Ventilation
Vital Capcacity
- Potential lung volume during a deliberate/ forced inhale/ exhale.
- We have a large vital capaicity, an important adaptation for activities (swimming eg.,)
- The sum of the inspiratory reserve volume, tidal volume & expiratorty reserve volume. DOESN’T include small residual volume.
Ventilation
Boyle’s Law - Pressure & Volume
- An increase in volume leads to a decrease in pressure, vice versa.
- Explains how expanding the volume of the lungs reduces the pressure, which reduces the pressure to LOWER than the atmospheric pressure, cuasing air to move in during inhalation.
- Increase in pressure by reducing volume is caused by exhalation.
Ventilation
Role of Intercostal Muscles
To adjust the ribcage.
* External Intercostal muscles expand the ribcage when the contract. When relaxed, then reduce the volume of the lungs for exhalation to occur.
* Internal Intercostal muslces contract to further shrink the lungs (forced exhale)
Haemoglobin
What is Haemoglobin?
- The oxygen transport protein found IN red blood cells. It’s a conjugated protein with 4 polypeptide subunits, each with a Haem group made of Iron.
- The haem group is the binding site of oxygen –> each haemoblogin can transport 4 O2 molcules.
- Each red blood cells has many haemoglobins.
Haemoglobin
Saturation of Haemoglobin
- Refers to how many O2 molecules are bound to haemoglobin.
- Each subsequent O2 added makes it easier for the next one to bind.
Haemoglobin
Cooporative binding?
- Each O2 molecule that binds to Haemoglobin makes it easer for the next one.
- Due to shape changes in the protein that increase the potentional/ affinity for the next O2 to bind, i.e O2 is most attracted to a haemoglobin with 3 O2 already bound.
Haemoglobin
What is allosteric binding?
- The binding of carbon dioxide to haemoglobin at an allosteric binding site.
- Like enzyme inhibition, this binding change the shape of the haemoglobin by reduching the attraction to the O2, making it more likely to detatch with CO2 bound
Haemoglobin
Fetal Haemoglobin?
- A fetus has haemoglobin for circulating O2 to the growing tissues.
- It’s haemoglobin is a distinct protein made of two alpha chains and two y chains, as oppose to two beta chains.
- It’s structural difference cause it to have a higher affinity for O2 than adult haemoglobin.
- Fetal haemoglobin thus ‘steals’ O2 from maternal blood.
Haemoglobin
Placenta?
- A highly vascularized tissue that connects the blood streams of the pregnant woman with the fetus.
- Within it, thin capillaries of mother & baby come close enough in contact for diffusion to occur.
- Due to high affinity of O2 for the fetal haemoglobin ,O2 diffuses out of maternal capillaries into the fetal ones.
Haemoglobin
Oxygen Partial Pressure?
- The pressure exerted by a gas in a mixture of gases.
- An indicator of available oxygen, and helps represent the relationship between O2 supply and the sauration of haemoglobin.
Haemoglobin
The Bhor Shift
- The fact that increased binding of CO2 causes the decreased binding/release of O2 is called the Bohr Shift.
- Often represented as a pH change that causes this shift, however the pH change is due to the increase in CO2 binding. (increased CO2, lowers pH, reduces affinity for O2)
Haemoglobin
Bohr Shift for Respiring Muscles
- Bohr shift helps understand how different cells can access O2 needed for cellular resp.
- Respiring tissues accumulate CO2.
- As blood circulates through respiring tissues, CO2 binds to RBCs, causing O2 to lose affinity & hop off haemoblogin, delivering to cells who need it to continue to create energy for acitvity.
Haemoglobin
Oxygen Dissociaiton Curve
- A graphical representation of the relationship between O2 availability and the saturation of haemoglobin.
- Curve’s non-linear shape relates to co-op binding, as O2 availability (pressure) increases & more O2 binds to Hb, it rapidly increases saturation.
Gas Exchange in Plants
What is a cuticle?
- Waxy lipid layer that covers the surface of leaves & prevents uncontrolled/ excessive leaf water loss by evaporation.
- No gaps in cuticle for the stomata.
- Varies in thickness for different plants –> thicker –> adaptation to limit water loss.
Gas Exchange in Plants
Epidermis?
- Uppermost cells, in plants, the small layer of cells at the surface of leaves.
- Epidermis cells secrete the cuticle that coats the cells providing a waterproof later.
Gas Exchange in Plants
Palisade Mesophyll?
- A densely packed region of cylindrical cells in the upper portion of the leaf.
- Contain many chloroplasts, located at the top to maximise exposure to sunlight for photosynthesis.
- Chloroplasts rich layer gives leaves their green colour & primary site of photosynthesis.
Gas Exchange in Plants
Sponge Mesophyll?
- Below the palisade mesophyll.
- A loosely packed layer of cells, containing fewer chloroplasts, with space between the cells to allow the gases that entered at the stomata to diffuse through to the palisade cells for photosynthesis.
Gas Exchange in Plants
Xylem?
- Tissue (like veins) for transport throughout the plant.
- The vessel (one of two for plants, phloem being the other vessel) that transports water and dissolved minerals from the roots up to the rest of the plant (leaves etc.)
Gas Exchange in Plants
Phloem?
- A seperate vessel that transports sugars, often with some water that it’s dissolved in.
- The transport vessel that collects sugars made in photosynthesis and delivers it to the parts of the plant (FRUITS) and below (STORAGE ROOTS) –> THINK rhyme, root and fruit.
Gas Exchange in Plants
Stomata?
- Pores (stoma singular) that are an opening in the epidermis allowing gases to enter and exit –> needed for photosynthesis.
- Helpful because the waxy cuticle reduces permeability of gases to enter through the epidermis.
- Stomata has the ability to be opened/ closed by gaurd cells.
Gas Exchange in Plants
Gaurd Cells?
- Pairs of cells placed one on each side of the stomata, controlling whether the stoma is closed or open.
1. Turgid Gaurd Cells –> open the stomata during the day, full vacuole, allowing gas exchange, photosynthesis and transpiration to occur. Water supply is present (hydrated plants).
2. Flacid Gaurd Cells –> closed stomata, during night, empty vacuole, no gas exhcnage, no photosynthesis or transpiration occurs.
Gas Exchange in Plants
Transpiration?
- When water vapour molecules leave the plant cells out of the stomata, created by broken hydrogen bonds in liquid water being released into water vapour molecules.
Influenced by:
1. Increased Temperature: More Transpiration, as increased kinetic enegery of liquid water moleculars increases evaporation to water vapour.
2. Increased Light: More transpiration, as gaurd cells are stimulated to open for CO2 & enhance photosynthesis.
3. Increased Wind:More transpiration, as wind moves released water away from stomata maintaining low water potential of air.
4. Increased Humidity:: LESS transpiration, as increased water potential of air/pulling it less/lower conc. gradient between air and leaf.
Gas Exchange in Plants
Stomatal Density?
- The mean no.stomata per unit area of leaf surface in mm^2.
Gas Exchange in Plants
Protometer?
- A tool for measuring rate of transpiration.
- As plant takes up water from roots, the ubble moves along the capillary tube.
