3. Organisms Exchange Substances with their Environment: Definitions (AQA A-Level Biology): Revision Notes
3. Organisms Exchange Substances with their Environment: Definitions
Alveoli: Tiny air-filled chambers located at the terminal ends of bronchioles in the lungs, featuring a large surface area that facilitates efficient gas exchange between the respiratory system and bloodstream.
Amylases: Digestive enzymes responsible for breaking down polysaccharides into simpler sugar units through hydrolysis reactions.
Antiporter: A specialised membrane protein that facilitates the simultaneous transport of two different molecular species across a cell membrane in opposing directions.
Aorta: The body's largest artery, responsible for transporting oxygenated blood under high pressure from the heart to various body tissues.
Arteriole: A small-diameter blood vessel that serves as a connection point between larger arteries and the capillary network.
Artery: A thick-walled blood vessel designed to transport blood away from the heart under high pressure to body tissues.
Atrium: A heart chamber that receives blood directly from veins and subsequently transfers it to the corresponding ventricle.
The cardiovascular system uses different vessel types for specific functions: arteries carry blood away from the heart under high pressure, while veins return blood to the heart. The heart's chambers (atria and ventricles) work together to maintain continuous blood flow throughout the body.
Bile salts: Molecular compounds present in the small intestine that facilitate lipid digestion by emulsifying fats, thereby increasing their surface area for enzyme action.
Bronchi: The two primary airways that branch from the trachea and direct airflow towards the smaller bronchioles.
Bronchioles: Narrow airways that branch extensively from the bronchi and terminate at the alveoli for gas exchange.
Capillary: An extremely narrow blood vessel with thin walls and minimal diameter, specifically adapted for efficient substance exchange between blood and surrounding tissues.
Capillary bed: An interconnected network of numerous capillaries that ensures comprehensive blood supply to tissue areas.
Coronary artery: The primary arterial vessel that delivers oxygenated blood specifically to cardiac muscle tissue.
Co-transport: A cellular transport mechanism involving the simultaneous movement of two distinct molecules across a membrane using a shared transport protein.
Diaphragm: A large muscular sheet positioned beneath the lungs that contracts and relaxes to alter lung volume, creating the pressure changes essential for breathing.
The respiratory system includes several key structures working together: the trachea provides the main airway, bronchi and bronchioles branch to distribute air, and alveoli provide the surface area for gas exchange. Respiratory muscles like the diaphragm and intercostal muscles create the pressure changes needed for ventilation.
Endopeptidases: Enzymes that break internal peptide bonds within polypeptide chains through hydrolysis.
Exopeptidases: Enzymes that cleave peptide bonds specifically at protein terminals, such as between the final amino acid and the rest of the polypeptide chain.
External intercostal muscles: Respiratory muscles positioned between ribs on the external surface, facilitating both forced and quiet inspiration through rib movement.
Gill filaments: Thin branching structures extending from fish gill arches that provide surface area for aquatic gas exchange.
Gill lamellae: Small projections on gill filaments that maximise the surface area available for efficient gas exchange with water.
Haemoglobin: A quaternary protein found in red blood cells, specialised for oxygen transport throughout the body's tissues.
Internal intercostal muscles: Respiratory muscles located between ribs on the internal surface, primarily involved in forced expiration.
Left atrium: The heart chamber that receives oxygen-rich blood from pulmonary veins and transfers it to the left ventricle.
Left ventricle: The heart chamber that receives oxygenated blood from the left atrium and pumps it throughout the body via the aorta.
Lipase: Digestive enzymes that catalyse the breakdown of lipids through hydrolysis reactions.
Membrane-bound dipeptidases: Enzymes located within cell membranes that break down dipeptides into individual amino acids.
Membrane-bound disaccharidases: Enzymes embedded in cell membranes that catalyse the breakdown of disaccharides into monosaccharides.
Micelles: Organised lipid molecule clusters that form hydrophobic capsules to facilitate lipid absorption in the digestive system.
Phloem: Plant tissue responsible for transporting organic compounds from their production sites to areas where they are required.
Positive cooperativity: The phenomenon where oxygen binding to haemoglobin causes structural changes that enhance the protein's affinity for additional oxygen molecules.
Pulmonary artery: The major vessel that transports deoxygenated blood from the heart to the lungs for gas exchange.
Pulmonary vein: The principal vessel that returns oxygenated blood from the lungs to the heart.
Renal artery: The main arterial vessel supplying oxygenated blood from the heart to kidney tissue.
Renal vein: The primary vessel returning deoxygenated blood from the kidneys to the heart.
Right atrium: The heart chamber that receives deoxygenated blood from the vena cava and directs it to the right ventricle.
Right ventricle: The heart chamber that receives deoxygenated blood from the right atrium and pumps it to the lungs via the pulmonary artery.
Spiracles: Small surface openings in insects that permit gas exchange between their internal systems and the external environment.
Spongy mesophyll: A type of plant leaf tissue with loosely arranged cells containing air spaces, optimised for gas exchange processes.
Stomata: Microscopic pores in plant leaves that can open and close under guard cell control to regulate water loss and gas exchange.
Symporter: A membrane transport protein that moves two different molecular species across a cell membrane in the same direction simultaneously.
The Bohr effect: The phenomenon where increased carbon dioxide concentration reduces haemoglobin's oxygen-binding affinity, facilitating oxygen release in metabolically active tissues.
Tissue fluid: Blood-derived fluid that surrounds cells, providing nutrients and dissolved gases while facilitating substance exchange.
Trachea: The main respiratory passage that provides an airway connection between the larynx and bronchi.
Trachea (mammals): A cartilage-reinforced tube enabling air movement between the larynx and bronchial airways.
Tracheae (insects): Branching tubes that connect spiracles to tracheoles, forming part of the insect gas exchange system.
Tracheoles: Microscopic tubes comprising the insect respiratory system that transport gases directly from tracheae to individual cells.
Vein: A blood vessel designed to return blood from body tissues back to the heart.
Vena cava: The largest vein that transports deoxygenated blood from body tissues into the right atrium.
Ventricle: A heart chamber that receives blood from the atrium positioned above it and pumps blood out of the heart.
Venule: A small-diameter blood vessel that connects the capillary network to larger veins.
Xerophyte: A plant species adapted for survival in environments with limited water availability.
Xylem: Plant tissue specialised for water transport throughout stems and leaves.
Plant transport systems are highly specialised: xylem transports water and minerals upward from roots, while phloem transports organic compounds throughout the plant. Gas exchange occurs through stomata, which can be controlled to balance carbon dioxide uptake with water loss.
Key Points to Remember:
- Gas exchange structures like alveoli and gill lamellae maximise surface area for efficient substance exchange
- The circulatory system uses different vessel types - arteries carry blood away from the heart, veins return it
- Transport proteins like antiporters and symporters facilitate movement of substances across membranes
- Digestive enzymes break down complex molecules - amylases for carbohydrates, lipases for fats, peptidases for proteins
- Plant structures like stomata, xylem and phloem are essential for substance exchange and transport