Exchange With Environment Flashcards
What is the difference between surface area to volume ratio in single-celled and large multicellular organisms?
Single-celled organisms have a large surface area to volume ratio and short diffusion pathway, while large multicellular organisms have a lower surface area to volume ratio, requiring specialized systems for exchange.
Why do small animals like mice have higher metabolic rates compared to large animals like horses?
Mice have a larger surface area to volume ratio, resulting in faster heat loss and therefore a higher metabolic rate to replace the lost heat.
How do insects exchange gases?
Insects use a system of tracheae with openings called spiracles, and tracheoles for direct exchange with respiring tissues. They limit water loss by closing spiracles and having a waxy cuticle.
What is the advantage of the counter-current principle in fish gills?
Water and blood flow in opposite directions, maintaining a diffusion gradient for oxygen across the whole surface of the gill lamellae.
How do guard cells regulate water loss in plants?
Guard cells open stomata during the day for gas exchange and close them when the plant is dehydrated to reduce water loss.
What role do bile salts play in lipid digestion?
Bile salts emulsify large lipid droplets into smaller droplets, increasing surface area for lipase action and forming micelles for easier absorption.
Describe the Bohr effect in haemoglobin affinity.
An increase in carbon dioxide lowers the pH, reducing haemoglobin’s affinity for oxygen and causing it to unload oxygen more readily.
Explain how water is transported in the xylem using cohesion-tension theory.
Transpiration creates a tension, pulling water up the xylem. Cohesion between water molecules maintains a continuous column, and adhesion to xylem walls helps water rise.
How does a potometer measure water uptake?
A potometer measures water uptake by tracking the movement of an air bubble in a sealed system, assuming uptake equals transpiration.
Describe the process of translocation in plants.
Sucrose is actively loaded into phloem at the source, lowering water potential and causing water to enter by osmosis. This creates high hydrostatic pressure, driving the flow towards sinks where sucrose is used or stored.
What adaptations allow alveoli to efficiently exchange gases?
Alveoli have a large surface area, are one cell thick, have a good blood supply, and are well-ventilated to maintain steep concentration gradients for oxygen and carbon dioxide.
What happens during inspiration (inhalation)?
The diaphragm contracts, external intercostal muscles contract, ribcage moves up and out, thoracic volume increases, pressure decreases, and air moves into the lungs.
What is the role of endopeptidases and exopeptidases in protein digestion?
Endopeptidases break peptide bonds within proteins, creating shorter chains, while exopeptidases remove amino acids from the ends, increasing digestion rate.
How are monosaccharides and amino acids absorbed in the ileum?
They are absorbed by co-transport with sodium ions. Sodium is actively transported out of cells, creating a gradient that allows sodium to bring monosaccharides and amino acids into cells.
How does the counter-current system in fish gills enhance gas exchange?
It ensures that water with a higher oxygen concentration always flows next to blood with lower oxygen concentration, maintaining a diffusion gradient along the entire length of the gill.
What are the three main factors affecting the rate of transpiration in plants?
Temperature (increases kinetic energy), humidity (lowers the gradient if high), and air movement (removes saturated air, increasing the water potential gradient).
How is water transported through the xylem?
Water moves up the xylem through cohesion between water molecules, adhesion to xylem walls, and tension created by evaporation from leaves.
What is the Bohr effect in gas exchange?
Increased carbon dioxide concentration decreases the pH, reducing haemoglobin’s affinity for oxygen, so more oxygen is released to tissues during respiration.
What are the structural differences between arteries and veins?
Arteries have thick, muscular, elastic walls and a narrow lumen to maintain high pressure. Veins have thinner walls, a wider lumen, and valves to prevent backflow of low-pressure blood.
Explain how tissue fluid is formed and reabsorbed.
High hydrostatic pressure at the arteriole end forces water and solutes out of the capillaries. Plasma proteins lower water potential, drawing water back in by osmosis at the venule end.
What happens during ventricular systole in the cardiac cycle?
Ventricles contract, increasing pressure, closing the atrioventricular valves, and forcing blood through the semilunar valves into the arteries.
How do lymph vessels contribute to tissue fluid balance?
Lymph vessels collect excess tissue fluid and return it to the circulatory system, preventing tissue swelling (oedema).
What is the significance of foetal haemoglobin having a higher affinity for oxygen than adult haemoglobin?
Foetal haemoglobin can extract oxygen from the mother’s blood even at lower oxygen partial pressures, ensuring the foetus receives sufficient oxygen.
How do plants reduce water loss in xerophytic conditions?
Xerophytes have adaptations such as rolled leaves, sunken stomata, a thick waxy cuticle, and hairs to trap humid air and reduce the water potential gradient.
How does cardiac output relate to heart rate and stroke volume?
Cardiac output is the volume of blood pumped by the heart per minute and is calculated by multiplying heart rate (beats per minute) by stroke volume (volume of blood per beat).
Why is diffusion insufficient for large multicellular organisms?
Large multicellular organisms have a lower surface area to volume ratio, making diffusion too slow for adequate exchange of substances.
How do small animals compensate for their high surface area to volume ratio?
Small animals like mice have a higher metabolic rate to generate more heat because they lose heat quickly due to their large surface area relative to volume.
Why do insects not require a respiratory pigment?
Insects use tracheoles for gas exchange directly with tissues, so they do not need respiratory pigments to transport oxygen in the blood.
Explain why the gills of fish have a counter-current flow system.
The counter-current flow of water and blood maintains a steep concentration gradient for oxygen across the entire length of the gill lamellae, increasing the efficiency of gas exchange.
What is the role of spiracles in insects?
Spiracles are openings in the tracheal system that allow gas exchange but can be closed to prevent water loss.
How does the rolling of leaves in xerophytes reduce water loss?
The rolled leaves trap humid air inside, lowering the water potential gradient between the inside and outside of the leaf, reducing water loss by transpiration.
What is the function of bile salts in lipid digestion?
Bile salts emulsify large fat droplets into smaller ones, increasing the surface area for the action of lipase.
