What is gas exchange?
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What is gas exchange?
Gas exchange is the process by which oxygen and carbon dioxide are exchanged between living organisms and their environment.
How does gas exchange occur in organisms?
Gas exchange takes place by the process of diffusion.
What are three factors that determine the rate of diffusion in gas exchange?
The three factors that determine the rate of diffusion in gas exchange are:
size of the respiratory surface
concentration gradient
diffusion distance
True or False?
Large multicellular organisms can rely on diffusion alone for gas exchange.
False.
Large multicellular organisms cannot rely on diffusion alone to supply every cell with oxygen due to their smaller surface area to volume ratio and greater diffusion distance.
List four properties of effective gas exchange surfaces.
Effective gas exchange surfaces are permeable, have a thin tissue layer, presence of moisture, and a large surface area.
Why do small, unicellular organisms like amoeba not need specialised gas exchange organs?
Small, unicellular organisms have a large surface area compared to their volume and a short diffusion distance, allowing sufficient diffusion for their oxygen needs.
How does the presence of moisture facilitate gas exchange?
Moisture facilitates gas exchange by allowing gases to dissolve, which aids their diffusion across the gas exchange surface.
What is the role of blood vessels in maintaining concentration gradients for gas exchange?
Blood vessels provide a dense network with a large surface area for gas diffusion and ensure continuous blood flow to maintain concentration gradients.
How does ventilation contribute to gas exchange?
Ventilation brings oxygen close to the gas exchange surface and removes carbon dioxide, helping to maintain concentration gradients.
True or False?
Respiration and gas exchange are the same process.
False.
Respiration is a chemical process occurring in all living cells, while gas exchange refers to the diffusion of oxygen and carbon dioxide across a respiratory surface.
How are the alveoli adapted for gas exchange?
The alveoli have thin walls to minimise diffusion distance, a good blood supply to maintain a steep concentration gradient and surfactant to increase the rate of diffusion.
How do bronchioles help regulate airflow into the lungs?
Bronchioles are lined with smooth muscle that can dilate when more air is needed and constrict when an allergen is present, regulating airflow.
What structure is found at the end of bronchioles?
Groups of alveoli are found at the end of bronchioles.
How do alveoli contribute to efficient gas exchange?
Alveoli provide a large surface area for gas exchange and are surrounded by an extensive network of capillaries.
True or False?
Bronchi have smooth muscle in their walls.
True.
Bronchi have walls strengthened with cartilage and a layer of smooth muscle that can contract or relax to change the diameter of the airways.
What is the function of surfactant in the alveoli?
Surfactant lowers the surface tension in the alveoli, preventing them from collapsing and sticking together during expiration.
What maintains the concentration gradient between alveoli and blood?
Deoxygenated blood enters the capillary beds from a branch of the pulmonary artery while oxygenated blood leaves via a branch of the pulmonary vein, maintaining the concentration gradient.
True or False?
The bronchi divide to form bronchioles.
True.
Bronchioles branch off the two bronchi to form a network of narrow tubes.
What is ventilation and why is it important?
Ventilation is the process of breathing in and out, which is essential for effective gas exchange in the lungs by replacing older air with fresh air and maintaining concentration gradients.
Define inspiration in the context of ventilation.
Inspiration is the process of breathing in, which causes the volume of the chest to increase and air pressure to decrease until it is lower than atmospheric pressure.
What happens to the diaphragm during inspiration?
During inspiration, the diaphragm contracts and flattens, increasing chest volume.
How do external intercostal muscles contribute to inspiration?
External intercostal muscles contract during inspiration, causing the ribcage to move upwards and outwards, increasing chest volume.
What causes air to move into the lungs during inspiration?
Air moves into the lungs during inspiration because it flows down the pressure gradient from the higher pressure outside to the lower pressure inside the lungs.
True or False?
Expiration is always an active process.
False.
Expiration is mostly a passive process due to the recoil of the lungs after they have been stretched by inspiration.
Describe the passive expiration process.
In passive expiration, external intercostal muscles relax, the diaphragm relaxes and becomes dome-shaped, and elastic fibres in alveoli walls recoil, reducing lung volume.
When does active expiration occur?
Active expiration occurs when there is a need to expel excess air from the lungs, such as when blowing out a candle.
What role do abdominal muscles play in active expiration?
During active expiration, abdominal muscles contract to push organs upwards against the diaphragm, decreasing the volume of the chest cavity.
True or False?
During expiration, the volume of the chest increases.
False.
During expiration, the volume of the chest decreases and pressure increases, causing air to be forced out down its pressure gradient.
What is a spirometer?
A spirometer is an apparatus used to investigate ventilation, consisting of a water-filled chamber covered by a hinged plastic lid.
Define tidal volume.
Tidal volume is the volume of air inhaled and exhaled during normal breathing.
What is vital capacity and how is it calculated?
Vital capacity (VC) is the total amount of air exhaled after taking a deep breath, calculated as:
VC = Tidal Volume + Inspiratory Reserve Volume + Expiratory Reserve Volume.
True or False?
Exercise decreases tidal volume.
False.
Exercise leads to an increase in tidal volume as more air is moved in and out of the lungs.
What is the inspiratory reserve volume?
Inspiratory reserve volume is the difference between the maximum inspiratory level and tidal volume.
How is ventilation rate determined using a spirometer?
Ventilation rate is determined by counting the number of inhalations or exhalations per minute on the spirometer trace.
What is the maximum expiratory level?
The maximum expiratory level is the maximum volume of air that can be exhaled during expiration.
True or False?
Exercise typically increases ventilation rate.
True.
Exercise causes an increase in ventilation rate as you take more breaths per minute.
What are stomata?
Stomata are tiny pores in the lower epidermis of a leaf through which gas exchange occurs.
Define transpiration.
Transpiration is the loss of water vapour from leaves by evaporation through the stomata.
What is the function of the waxy cuticle on a leaf?
The waxy cuticle prevents gases and water vapour from leaving through the epidermis, ensuring that gas exchange occurs through stomata.
True or False?
Most stomata are found in the upper epidermis of a leaf.
False.
Most stomata are found in the lower epidermis where the temperature is lower, reducing water loss.
What is the main difference between palisade and spongy mesophyll tissue?
Palisade mesophyll contains many chloroplasts for maximum photosynthesis, while spongy mesophyll contains large air spaces between cells for gas exchange.
What is the function of vascular bundles in leaves?
Vascular bundles form the veins in leaves and are responsible for the transport of substances around the plant, with xylem transporting water and mineral ions, and phloem transporting products of photosynthesis.
What is the role of guard cells in a leaf?
Guard cells control gas exchange and water loss by opening or closing stomata.
How does air movement affect transpiration rate?
More air movement leads to increased rates of transpiration by maintaining a steeper concentration gradient for water vapour diffusion.
How does temperature affect transpiration rate?
Higher temperatures lead to higher rates of transpiration up to a point, as increased kinetic energy causes water molecules to evaporate faster.
How does light intensity affect transpiration?
Higher light intensities increase the rate of transpiration up to a point, as stomata open in light to enable gas exchange for photosynthesis.
After a point, the stomata may close to reduce water loss as temperatures rise.
What is the effect of high humidity on transpiration?
Higher humidity levels reduce the rate of transpiration by decreasing the concentration gradient for water vapour diffusion.
What is a potometer?
A potometer is a piece of equipment used to measure the rate of water uptake in plants, which is used to represent the rate of transpiration.
Name two different types of potometer.
Two types of potometer are:
Bubble potometer
Mass potometer
What are two advantages of transpiration for plants?
Two advantages of transpiration are:
It provides a means of cooling the plant via evaporation
It helps in the uptake of mineral ions through the transpiration stream
True or False?
The movement of water molecules during transpiration is by osmosis.
False.
The movement of water molecules during transpiration is not by osmosis, as it does not cross a cell membrane.
True or False?
Plan diagrams should include individual cells.
False.
Plan diagrams should not include individual cells, only tissue layers enclosed by lines should be present.
List four rules for labelling plan diagrams.
When labelling your plan diagram remember to:
Use a ruler to draw label lines, not freehand
Avoid using arrowheads and make sure the label lines stop at the structure
Make sure label lines do not cross each other
Write all labels horizontally, not at different angles
True or False?
Plan diagrams can include shaded areas.
False.
Plan diagrams cannot include shaded areas.
How much space should a plan diagram fill up on a page?
A plan diagram should be big enough to fill up at least half the available space.
What is stomatal density?
Stomatal density is the number of stomata per unit of area.
Define the term leaf cast.
Leaf cast is an impression of a leaf's surface created by applying and peeling off a layer of nail varnish.
True or False?
A coverslip is required when examining a leaf cast under a microscope.
False.
A coverslip is not required as a leaf cast isn't a biological sample, just an impression of one.
What is the ideal range of stomata to count in a single field of view?
The ideal range of stomata to count in a single field of view is between 15 and 100.
State the equation for calculating stomatal density.
Stomatal density = Mean number of stomata ÷ Area of field of view
What does 'anomalous measurements' mean in the context of stomatal density?
Anomalous measurements are those that deviate from the expected measurements when counting stomata.
What is the purpose of using a stage micrometer in this experiment to determine stomatal density?
The purpose of using a stage micrometer is to measure the diameter of the field of view at the same magnification used for counting stomata.
Define the term 'reliability' in the context of scientific measurements. (NOS)
Reliability is the level of trust that can be placed in numerical measurements, increased by repeating measurements and obtaining consistent results.