B3.1 Gas exchange Flashcards
What are the properties of gas exchange surfaces?
- Surfaces are thin (decreases the distances that the gases need to diffuse through)
- Permeable membranes (so that the gases can pass/cross through)
- Large surface area to volume ratio
- Surfaces are moist (gases can diffuse better when dissolved in a solution)
Explain the maintenance of the concentration gradients at exchange surfaces in animals.
- Diffusion is passive and is driven by concentration gradients
- High gradients lead to faster rates of diffusion
- High concentration to low concentration (molecules)
- Complex organisms have ventilation systems.
- Ventilation is air moving in and out of these ventilation systems. Ex: for humans the ventilation system is our lungs, whereas for fish, it is their gills. So, the form of ventilation systems may be different, but they all have the same function.
What are the adaptations of mammalian lungs for gas exchange?
- Draw diagram of lungs, and then in detail- the digram of the alveoli and capillaries
- Explain how the two types of pneumocytes help in gas exchange
-Air is drawn
into the lungs through the trachea
(windpipe) and then the left and
right bronchi (singular, bronchus). In each lung, the bronchus branches repeatedly to form bronchioles. Alveolar ducts branch of from the bronchioles, each leading to a group of five or six alveoli (air-sacs). - Alveoli are surrounded by a dense
capillary network. The capillary wall
is also extremely thin and consists
of a single layer of cells. Air and blood are therefore a very short distance apart. The capillaries cover
much of the surface of the alveoli
but there are also some other cells. - Hence, gases can easily diffuse in and out of these walls.
- Also mention that blood keeps flowing and hence diffusion can continue occurring.
Describe the features of the lungs that make gas exchange efficient.
The exchange surface has a large surface area, provided by the large number of alveoli. The surface is only one cell thick, and is supplied with blood by a very dense network of capillaries. This makes gas exchange more efficient.
Explain the process of ventilation in the lungs. (inhalation and exhalation)
During inhalation-
1. Diaphragm and external intercostal muscles contract, so the diaphragm basically flattens out.
2. Abdominal muscles and internal intercostal muscles relax, allowing them to expand.
3. Volume of the chest cavity increases, therefore pressure in the lungs decrease.
4. Air is pulled into the lungs.
During exhalation-
1. Diaphragm and external intercostal muscles relax.
2. Abdominal muscles and internal intercostal muscles contract.
3. Pressure increases inside the lungs, hence the volume of the chest cavity decreases.
4. Air is pulled out of the lungs.
Outline the measurement of lung volumes.
- Ventilation rate= number of inhalations/ number of exhalations per minute
- Tidal volume (TV)= Vol. of air inhaled/ Vol. of air exhaled
- Inspiratory reserve volume (IRV)= amount of air a person can inhale after a normal breath.
- Expiratory reserve volume (ERV)= amount of air a person can exhale after a normal breath.
- Vital capacity= total amount of air the lungs can hold= TV+IRV+ERV
What are the adaptations for gas exchange in leaves?
- The outer surface of the lead is covered in a layer of wax, secreted by the epidermis cells. This waterproof layer is called the waxy cuticle and has low permeability to gases.
- The stomata are openings for gas exchange and water loss. They connect the air outside to a network of air spaces in the spongy mesophyll of the leaf.
Draw a diagram for the distribution of tissues in a leaf.
Include-
- waxy cuticle
- upper epidermis
- palisade mesophyll (xylem)
- spongy mesophyll (moist for gas exchange) (phloem)
- lower epidermis
- waxy cuticle
What is transpiration and how is it a consequence of gas exchange in a leaf?
- Water moves from a region of high concentration to a region of low concentration (osmosis)
- Transpiration is a loss of water vapour from these leaves.
- Higher temperatures lead to more transpiration since the air is drier than the leaf.
- Higher humidity leads to less transpiration since the air is moist too.
Stomatal density?
Two ways to check-
1. Nail polish-under side of the leaf-tape after nail polish dries-microscope-stomata can be seen
- remove lower epidermis if easy to remove- microscope- stomata can be seen
stomatal density (mm^-2)= mean no. of stomata/area of field of view (mm^2)
or # of stomata/cm^2
What are the adaptations of foetal and adult haemoglobin for the transport of oxygen?
- Haemoglobin can transport 4 oxygen molecules.
- It consists of 4 polypeptide chains and contains a haem group between each.
- For adult- 2 alpha, 2 beta; For foetus- 2 alpha, 2 gamma.
- Oxygen binding causes a conformational change which could be the structure, which leads to a higher affinity or attraction to oxygen molecules.
- It is reversible, so one molecule of oxygen need not permanently stay within the same haemoglobin.
Talk about the relation between oxygen dissociation curves and partial pressure.
- Partial pressure is the pressure exerted by one gas in a mixture of gases. Its unit is in KiloPascals (KPa)
- Foetal haemoglobin has a higher affinity for oxygen and so its curve will be slight to the left as compared to the adult haemoglobin curve.
Explain the Bohr Shift.
⬆️ ATP= ⬆️ respiration= ⬆️ CO2= ⬇️ pH= carbaminohaemoglobin.
So, haemoglobin+4CO2=CAHG
- CAHG has a lesser affinity to oxygen, so it gives up oxygen at a higher partial pressure to surrounding cells that require oxygen.
- Bohr Shift is basically the shift in the curve due to higher concentrations of carbon dioxide which is reducing the affinity of haemoglobin.
- CO2+H2O=H^+ + HCO3^-
Which is the prime site for the exchange of gases in our body?
Alveoli
Why does smoking cigarettes cause emphysema?
It is a chronic disease of the respiratory system where inflation of the alveolar occurs. Over a period of time, cigarette smoking or even inhalation of smoke causes the damage of septa between the alveoli and of its elastic tissue is substituted by the connective tissue in the lungs. The respiratory surface decreases which cause emphysema.
