Topic 3: Organisms exchange substances with their environment

Why do multicellular organisms require specialized exchange surfaces?

Due to a larger distance for substances to cross and a higher surface area to volume ratio.

What are the features of an efficient exchange surface?

Large surface area, thin structure, good blood supply/ventilation.

How do fish achieve gas exchange?

Through gills with lamellae, where blood and water flow in a counter current direction.

What is the role of the operculum in fish ventilation?

It acts as a valve and pump to let water out and pump it in.

How do terrestrial insects transport oxygen?

Through spiracles and tracheae that allow direct gas exchange with tissues.

What adaptations do plants have for gas exchange?

Leaves have stomata for gas entry and air spaces for gas movement.

What is the structure and function of the mammalian lungs?

Lobed structures with a large surface area located in the chest cavity, protected by the rib cage.

How does air flow into the lungs?

Air enters through the nose, trachea, bronchi, and bronchioles.

What is the role of cartilage in the trachea and bronchi?

It supports the airways and prevents them from collapsing.

What is the function of ciliated epithelium in the respiratory system?

It moves mucus to prevent lung infections by clearing it towards the throat.

What do goblet cells do in the respiratory system?

They secrete mucus to trap bacteria and dust.

What is the role of smooth muscle in the bronchioles?

It controls the diameter of the airway, regulating airflow to the alveoli.

How do elastic fibers function in the lungs?

They stretch during exhalation and recoil during inhalation to control airflow.

What are the two stages of ventilation?

Inspiration and expiration.

What happens during expiration?

Internal intercostal muscles contract, diaphragm relaxes, decreasing thoracic volume and increasing pressure.

What occurs during inspiration?

External intercostal muscles contract, diaphragm flattens, increasing thoracic volume and decreasing pressure.

What is a spirometer used for?

To measure lung volume by recording the volume of air breathed in and out.

What is the significance of a steep diffusion gradient in gas exchange?

It maximizes the amount of oxygen diffusing into the blood from water.

What is the function of alveoli in the lungs?

They are the sites of gas exchange, providing a large surface area and thin walls for efficient diffusion.

How many alveoli are typically found in human lungs?

Approximately 300 million.

What is the role of the diaphragm in ventilation?

It separates the thoracic cavity from the abdomen and aids in changing thoracic volume.

What is the importance of maintaining a good blood supply in the alveoli?

It ensures a steep concentration gradient for efficient gas exchange.

What happens to the gill filaments when fish are out of water?

They stick together, preventing gas exchange and leading to suffocation.

What adaptations do gills have for gas exchange?

They have multiple lamellae to increase surface area and facilitate counter current flow.

What is the primary gas exchanged in the alveoli?

Oxygen is absorbed, and carbon dioxide is released.

What is the role of the rib cage during breathing?

It protects the lungs and aids in the mechanics of ventilation.

What is the function of tracheoles in insects?

They deliver oxygen directly to tissues through a network of tubes.

What does vital capacity refer to?

The maximum volume of air that can be inhaled or exhaled in a single breath.

What is tidal volume?

The volume of air breathed in and out at rest.

How is breathing rate calculated?

By counting the number of peaks or troughs in a spirometer trace per minute.

What is residual volume?

The volume of air that is always present in the lungs.

What happens to tidal volume during exercise?

It can be exceeded as the inspiratory reserve volume is reached.

What is digestion?

The hydrolysis of large biological molecules into smaller molecules that can be absorbed.

Which enzymes digest carbohydrates?

Amylases, maltases, sucrases, and lactases.

How are lipids digested?

By lipases that hydrolyze the ester bond between monoglycerides and fatty acids.

What role do bile salts play in lipid digestion?

They emulsify lipids into micelles, increasing surface area for digestion.

What are the three main groups of peptidases?

Endopeptidases, exopeptidases, and dipeptidases.

How are amino acids absorbed in the ileum?

By facilitated diffusion through specific carrier molecules and co-transport with Na+.

What happens to monoglycerides and fatty acids after absorption?

They are reformed into triglycerides in the endoplasmic reticulum and transported to the lymph system.

What is haemoglobin?

A water-soluble globular protein that carries oxygen in the blood.

How many oxygen molecules can one haemoglobin molecule carry?

Four oxygen molecules.

What is the Bohr effect?

The decrease in haemoglobin's affinity for oxygen in the presence of carbon dioxide.

What is positive cooperativity in haemoglobin?

The increased affinity for oxygen after the first oxygen molecule binds.

What is the difference between fetal and adult haemoglobin?

Fetal haemoglobin has a higher affinity for oxygen to survive at low partial pressures.

What are the common features of a circulatory system?

A suitable medium, means of moving the medium, control flow mechanisms, and a closed system of vessels.

What is the transport medium in mammals?

Blood, which is water-based.

What is the function of the heart in the circulatory system?

To pump blood and maintain pressure differences around the body.

What are the two main pumps of the mammalian heart?

One pumps blood to the lungs, the other pumps oxygenated blood around the body.

What are the two types of chambers in the heart?

Atria and ventricles.

What is the role of valves in the circulatory system?

To prevent backflow of blood.

What is the aorta's function?

To carry oxygenated blood from the left ventricle to the body.

What does the pulmonary artery do?

Carries deoxygenated blood from the right ventricle to the lungs.

What does the pulmonary vein do?

It brings oxygenated blood back from the lungs to the left atrium.

What is the function of the vena cava?

It brings deoxygenated blood back from the tissues to the right atrium.

What is the sinoatrial node?

It is the pacemaker of the heart located in the right atrium that initiates electrical stimulation.

What is the role of the atrioventricular node?

It passes the electrical excitation from the atria to the ventricles.

What happens during cardiac diastole?

The atria and ventricles relax, allowing blood to fill the heart chambers.

What occurs during atrial systole?

The atria contract, forcing blood into the ventricles.

What is ventricular systole?

It is the contraction of the ventricles that allows blood to leave the heart through the aorta and pulmonary artery.

What are arteries adapted for?

They carry blood away from the heart and are thick-walled to withstand high blood pressure.

What is the function of arterioles?

They branch off arteries and feed blood into capillaries.

What is the primary function of capillaries?

They are the site of metabolic exchange and are only one cell thick for fast exchange of substances.

What do veins do?

They carry blood from the body back to the heart and contain valves to prevent back-flow.

What is tissue fluid?

It is a liquid containing dissolved oxygen and nutrients that supplies tissues and exchanges waste products.

How is hydrostatic pressure created?

It is created when blood is pumped along the arteries, arterioles, and capillaries, forcing fluid out of capillaries.

What is the role of the lymphatic system?

It carries excess tissue fluid back to the bloodstream and filters out bacteria and foreign material.

What is transpiration in plants?

It is the process where plants absorb water through the roots and release it as water vapor through leaves.

What do xylem vessels do?

They transport water and minerals up the plant and provide structural support.

What is translocation in plants?

It is the active transport of sugars throughout the plant via phloem tissue.

What is the structure of xylem vessels?

They are long cylinders made of dead tissue with open ends, allowing for a continuous column of water.

What is the function of stomata in leaves?

They allow carbon dioxide to enter and water vapor to exit the leaf.

What is the role of lignin in xylem vessels?

It thickens the walls of xylem vessels, allowing them to remain flexible while providing support.

What is the purpose of the cambium layer in vascular bundles?

It contains meristem cells involved in the production of new xylem and phloem tissue.

What is the significance of the transpiration stream?

It supplies water for photosynthesis, growth, and temperature control in plants.

What is the difference between tissue fluid and lymph fluid?

Tissue fluid contains more oxygen and nutrients, while lymph fluid contains less and primarily carries waste products.

What is the function of Purkyne fibres?

They carry the electrical wave upwards, causing the ventricles to contract.

What happens to the semi-lunar valves during ventricular systole?

They open to allow blood to leave the ventricles.

What is the role of smooth muscle in arteries?

It enables arteries to vary blood flow by contracting and relaxing.

What is the structure of veins compared to arteries?

Veins have thinner walls and a wider lumen, as blood is under lower pressure.

What is the function of the endodermis in plant roots?

It supplies xylem vessels with water.

What is transpiration?

The process of water vapor loss from plant surfaces, primarily through stomata.

How is the rate of transpiration measured?

Using a potometer to measure the movement of water lost by a leaf.

What factors affect the rate of transpiration?

Number of leaves, stomata size/position, waxy cuticle presence, light, temperature, humidity, air movement, and water availability.

What are xerophytes?

Plants adapted to dry conditions with adaptations to minimize water loss.

How do xerophytes minimize water loss?

By having smaller leaves, thick waxy cuticles, and closing stomata during low water availability.

What is the role of root hair cells?

To provide a large surface area for water absorption from the soil.

What is the symplast pathway?

The route where water enters the cytoplasm and moves from cell to cell through plasmodesmata.

What is the apoplast pathway?

The route where water moves through the spaces between cellulose molecules in cell walls without crossing plasma membranes.

What is the Casparian strip?

A layer of suberin in the endodermis that prevents water from passing through cell walls.

How does water move up the xylem?

Water is pushed upwards by root pressure and pulled by cohesion and surface tension.

What is the cohesion-tension theory?

A theory explaining how water is pulled up through the xylem due to cohesion between water molecules and tension created by transpiration.

What are the components of phloem?

Sieve tube elements and companion cells.

What is active loading in translocation?

The process where companion cells use ATP to transport hydrogen ions, creating a gradient that allows sucrose to enter the phloem.

How does sucrose move from companion cells to sieve tube elements?

Through plasmodesmata as a result of concentration gradient differences.

What happens to water potential in the sieve tube when sucrose enters?

The water potential decreases, causing water to enter from the xylem via osmosis.

What is mass flow in the context of translocation?

The movement of sucrose and water from areas of high hydrostatic pressure to areas of low hydrostatic pressure in the phloem.

What evidence supports the mass transport theory?

Pressure in sieve tubes, higher sucrose concentration in leaves than roots, and metabolic poisons inhibiting translocation.

What are ringing experiments?

Experiments that show sucrose is transported in the phloem by removing the bark and observing swelling above the cut.

What are tracer experiments?

Experiments using radioactive carbon dioxide to trace the movement of sugars in plants.

What role do plasmodesmata play in phloem function?

They allow communication and flow of substances between sieve tube elements and companion cells.