B3.1 —> GAS EXCHANGE Flashcards
(23 cards)
What is gas exchange and why is it vital in all organisms?
Gas exchange is the uptake of oxygen and removal of carbon dioxide, vital for aerobic respiration which releases energy for cellular functions.
Why can small organisms rely solely on diffusion for gas exchange?
They have a large surface area to volume ratio and short diffusion distances, allowing efficient gas exchange without specialized systems.
Why do larger organisms need specialized gas exchange systems?
Because surface area to volume ratio decreases and the distance between cells and the environment increases, making diffusion alone insufficient.
What are four key properties of efficient gas exchange surfaces?
They are permeable, thin (short diffusion distance), moist (for gas solubility), and have a large surface area.
How do animals maintain concentration gradients at exchange surfaces? (3)
1) dense capillary networks —> carry gases away/towards exchange surfaces
2) continuous blood flow —> steep gradient
3) ventilation (air in lungs or water in gills) to keep gas levels optimal
What structural features of the lungs increase efficiency of gas exchange?
Millions of alveoli —> ⬆️ surface are
Bronchioles = branched system —> efficient distribution to all lung areas = maximised contact w/ capillary networks
Capillary beds —> surround alveoli for efficient gas transfer
Surfactant—> lipoprotein secreted by alveolar walls to ⬇️surface tension = prevent collapse during exhalation
What does pulmonary surfactant do in the alveoli?
It reduces surface tension, preventing alveolar collapse during exhalation and making breathing easier.
What is the role of bronchiole branching in the lungs?
It increases surface area and ensures even air distribution to all alveoli, improving gas exchange efficiency.
Describe the process of inspiration (inhalation).
Diaphragm contracts and flattens; external intercostal muscles contract; ribcage moves up and out; chest volume increases; pressure drops; air flows in.
Describe passive expiration (exhalation).
Diaphragm relaxes; external intercostal muscles relax; ribcage moves down and in; chest volume decreases; pressure increases; air flows out.
What muscles are involved in forced expiration and why?
Internal intercostal and abdominal muscles contract to reduce lung volume further and force out air (e.g. blowing out a candle).
What does a spirometer measure?
Lung volumes including tidal volume, inspiratory and expiratory reserves, vital capacity, and ventilation rate.
Define tidal volume.
The amount of air inhaled and exhaled during normal breathing.
How is vital capacity calculated?
VC = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV)
What are key adaptations in leaves for gas exchange?
Waxy cuticle (gas exchange only through stomata), stomata (mostly lower epidermis), air spaces (diffusion), spongy mesophyll (surface area), and veins (transport).
What structures should be included in a plan diagram of a dicot leaf?
Cuticle, upper/lower epidermis, palisade mesophyll, spongy mesophyll, guard cells, stomata, and vascular bundles (xylem & phloem).
What is transpiration and why does it occur?
Loss of water vapor from leaves via stomata; it’s a side effect of stomata opening for gas exchange.
List four factors affecting transpiration rate.
Light (increases), temperature (increases), humidity (decreases), wind (increases by removing moist air).
How can stomatal density be measured?
Make a leaf cast with clear nail varnish, peel it off, place on slide, count stomata under microscope, and calculate area with a stage micrometer.
How do you ensure reliable data when measuring stomatal density?
Repeat measurements in multiple fields of view, eliminate anomalies, and calculate a mean.
What is the importance of repeating measurements in biology (NOS)?
It increases the reliability of quantitative data by identifying and minimizing anomalies, leading to more accurate conclusions.
Describe how a concentration gradient of oxygen is maintained between lungs & blood capillaries
a. gas exchange takes place between the alveoli and capillaries;
B. alveoli surrounded by (dense) network of blood capillaries;
c. blood returning to alveolar capillaries is low in oxygen;
d. ventilation brings air rich in oxygen into the alveoli/lungs;
e. there is a higher concentration of oxygen in alveoli than in blood capillaries;
f. oxygen diffuses from alveoli/lungs to capillaries (moves down a concentration gradient);
Explain how gases are exchanged between the air in the alveolus and the blood in the capillaries.
b. gas dissolves in water lining the alveolus
c. diffuses through wall of alveolus and capillary into blood
d. concentration in blood greater than in alveolar air «prior to gas exchange»
e. diffuses through wall of capillary and alveolus into alveolar airspace
