Cambridge International AS & A Level Biology (9700): Gas Exchange, Transport, Infectious Disease, and Immunity

Comprehensive vocabulary flashcards covering the gas exchange system, smoking, infectious diseases, antibiotics, immunity, and mammalian transport systems from Cambridge AS & A Level Biology (9700) Paper 1 materials.

Ciliated Epithelium

A specialized epithelial tissue lining the airways consisting of cells with hair-like cilia that beat rhythmically to sweep mucus and trapped foreign particles upward toward the throat.

Goblet Cells

Specialized epithelial cells found in the trachea, bronchi, and larger bronchioles that synthesize and secrete mucus to trap inhaled dirt, dust, and pathogens.

Cartilage

A flexible connective tissue present as incomplete C-shaped rings in the trachea and irregular plates in bronchi that provides support and prevents the airways from collapsing during breathing.

Smooth Muscle (in airways)

An involuntary contractile tissue present in the walls of the trachea, bronchi, and bronchioles that contracts and relaxes to regulate airway diameter and air resistance.

Elastic Fibres (in gas exchange)

Protein fibres containing elastin found in the walls of alveoli and airways that stretch during inhalation and recoil during exhalation to force air out.

Pulmonary Surfactant

A phospholipid-protein fluid secreted by alveolar epithelial cells that reduces surface tension across the alveolar liquid lining, preventing the collapse of alveoli during exhalation.

Tar

A toxic, sticky mixture of chemical compounds in tobacco smoke that paralyses and destroys cilia, stimulates goblet cells to hypersecrete mucus, and contains chemical carcinogens that cause DNA mutations.

Nicotine

An addictive alkaloid in tobacco smoke that stimulates adrenaline release, constricts arterioles, increases heart rate, and raises blood pressure.

Carbon Monoxide

A toxic gas present in cigarette smoke that binds with high affinity to haemoglobin to form carboxyhaemoglobin, thereby decreasing the oxygen-carrying capacity of the blood.

Chronic Obstructive Pulmonary Disease (COPD)

A progressive, non-reversible respiratory condition commonly occurring in individuals over 30 years old that encompasses chronic bronchitis and emphysema, presenting with breathlessness, chronic cough, and high sputum production.

Emphysema

A lung disease characterized by the breakdown of elastin in alveolar walls by elastase, causing alveoli to burst, which drastically reduces the surface area available for gaseous exchange and eliminates elastic recoil.

Elastase

A destructive protease enzyme released by alveolar macrophages in response to chronic inflammation that digests elastic fibres in the walls of bronchioles and alveoli.

Chronic Bronchitis

A form of COPD characterized by chronic inflammation, persistent infection, and scarring of the bronchi, accompanied by hypertrophy of goblet cells and hypersecretion of mucus.

Pathogen

A disease-causing biological agent or biological organism, such as a bacterium, virus, fungus, or protoctist.

Vibrio cholerae

A water-borne bacterial pathogen transmitted via water or food contaminated with human faeces that causes cholera by releasing toxins in the small intestine.

Plasmodium

A genus of parasitic protoctists that acts as the causative pathogen of malaria, exhibiting multiple antigenic variants across its life cycle inside human red blood cells and hepatocytes.

Anopheles

The genus of mosquito whose females act as insect vectors for malaria, transferring $Plasmodium$ parasites into the human bloodstream during blood meals.

Vector

An organism (such as the female $Anopheles$ mosquito) that transmits a pathogen from one host to another without being harmed by the disease itself.

Mycobacterium tuberculosis

The bacterial pathogen that causes tuberculosis (TB), transmitted through airborne droplets released by infected individuals when coughing or sneezing.

Morbillivirus

The viral pathogen transmitted through airborne respiratory droplets that causes the highly contagious disease measles.

Penicillin

A bactericidal antibiotic that acts as an enzyme inhibitor against transpeptidase, preventing the cross-linking of peptidoglycan chains in growing bacterial cell walls and resulting in osmotic lysis.

Transpeptidase

The bacterial enzyme that catalyses the formation of peptide cross-links between peptidoglycan polymers during bacterial cell wall synthesis.

Osmotic Lysis

The rupture and death of a bacterial cell caused by the uncontrolled influx of water via osmosis when the cell wall is weakened or inhibited.

Antibiotic Resistance

The capacity of a bacterial population to survive exposure to an antibiotic that normally kills it, arising from random DNA mutations and subsequent natural selection under antibiotic pressure.

MRSA

Methicillin-resistant $Staphylococcus\,aureus$, a pathogenic bacterium that has evolved resistance to methicillin and multiple other conventional antibiotics.

B-Lymphocytes

White blood cells that mature in the bone marrow and provide humoral immunity by binding specific antigens and dividing by mitosis into plasma cells and memory B cells.

T-Lymphocytes

White blood cells that originate in the bone marrow and are processed in the thymus; they mediate cellular immunity via cytokine secretion (helper T cells) or direct destruction of infected body cells (killer T cells).

Plasma Cells

Short-lived effector cells derived from activated B-lymphocytes containing abundant rough endoplasmic reticulum and Golgi bodies that produce and secrete thousands of specific antibodies per second.

Memory Cells

Long-lived lymphocytes formed during a primary immune response that remain in circulation to mount a faster and larger secondary immune response upon subsequent encounter with the same antigen.

Variable Region

The distinct antigen-binding site at the tip of the 'Y' shape of an antibody formed by specific amino acid sequences on both the heavy and light polypeptide chains.

Constant Region

The unchanging amino acid sequence of an antibody's heavy and light chains that determines its functional class and binds to surface receptors on phagocytes.

Hinge Region

A flexible region located on the heavy polypeptide chains of an antibody molecule that permits variations in the distance between the two antigen-binding sites.

Natural Active Immunity

Long-term immunity acquired when an individual is naturally exposed to a live pathogen, activating their own immune system to generate specific antibodies and memory cells.

Artificial Active Immunity

Long-term protection achieved by introducing antigens or attenuated pathogens via vaccination, stimulating an individual's own lymphocytes to produce antibodies and memory cells.

Natural Passive Immunity

Short-term protection conferred to an infant via maternal antibodies transported across the placenta before birth or ingested in colostrum after birth, without activating the recipient's own lymphocytes.

Artificial Passive Immunity

Short-term protection achieved by injecting pre-formed antibodies directly into the recipient's bloodstream, providing immediate defence without producing memory cells.

Monoclonal Antibodies

Pure, identical antibodies derived from a single clone of hybridoma cells that are all identical and specific to a single target epitope.

Hybridoma

A cell constructed by fusing an antigen-sensitized B-lymphocyte (plasma cell) with an immortal myeloma (cancer) cell, utilized to manufacture monoclonal antibodies indefinitely.

Telomerase

An active enzyme found in cancer and hybridoma cells that prevents the shortening of telomeres during repeated mitotic cycles, conferring cellular immortality.

Autoimmune Disease

A pathological state in which the immune system fails to distinguish self from non-self, mistakenly generating antibodies and effector cells against the body's own tissues.

Myasthenia Gravis

An autoimmune disorder characterized by plasma cells secreting autoantibodies that bind to and block acetylcholine (ACh) receptors on muscle cell surface membranes, preventing stimulation and inducing muscle breakdown.

Severe Combined Immunodeficiency (SCID)

An inherited genetic disorder in which children lack functional T-lymphocytes, compromising cell-mediated and humoral immunity and leaving patients susceptible to fatal infections; treatable by stem cell transplants.

Tunica Media

The thick middle layer of an artery wall composed of smooth muscle cells, collagen, and elastic fibres that allows arteries to withstand high hydrostatic pressure.

Endothelium

A smooth single-cell layer of squamous epithelial cells lining the lumen of all blood vessels and heart chambers that reduces friction to blood flow.

Sinoatrial Node (SAN)

A specialized collection of cardiac cells located in the right atrial wall that acts as the heart's primary pacemaker by spontaneously initiating waves of electrical excitation across both atria.

Atrioventricular Node (AVN)

A specialized region of conducting tissue that receives electrical excitation from the atria and introduces a short delay before transmitting the impulse to the ventricles, allowing atrial emptying.

Purkyne Tissue

Specialized conducting muscle fibres that run down the septum and spread through the ventricle walls to conduct electrical impulses rapidly to the apex, ensuring ventricular contraction proceeds from the base upwards.

Ventricular Systole

The phase of the cardiac cycle in which the ventricles contract, causing ventricular pressure to exceed atrial and arterial pressures, closing the atrioventricular valves and forcing open the semilunar valves.

Diastole

The relaxation phase of the cardiac cycle during which both atria and ventricles relax, allowing blood from the veins to flow into the heart under low pressure.

Carbaminohaemoglobin

A molecular complex formed when carbon dioxide directly binds to the uncharged terminal amino groups ($-\text{NH}_2$) of haemoglobin polypeptide chains.

Carbonic Anhydrase

An enzyme present inside erythrocytes that catalyses the reversible hydration of carbon dioxide: $\text{CO}_2 + \text{H}_2\text{O} \rightleftharpoons \text{H}_2\text{CO}_3$.

Haemoglobinic Acid

A molecular compound formed when reduced haemoglobin buffers free hydrogen ions ($\text{H}^+$) produced by the dissociation of carbonic acid, preventing blood acidosis.

Bohr Effect

The physiological shift of the oxygen dissociation curve of haemoglobin to the right caused by an increased concentration of $\text{CO}_2$ or reduced pH, facilitating the release of oxygen in metabolically active tissues.

Chloride Shift

The diffusion of chloride ions ($\text{Cl}^-$) from plasma into red blood cells to maintain electrical neutrality as hydrogencarbonate ions ($\text{HCO}_3^-$) diffuse out into the plasma.

2,3-Bisphosphoglycerate (2,3-BPG)

A biochemical substance in red blood cells that binds allosterically to haemoglobin, decreasing its oxygen affinity and shifting the oxygen dissociation curve to the right to encourage oxygen release.

Neutrophils

Granular, short-lived phagocytic white blood cells with multi-lobed nuclei that leave blood capillaries to enter inflamed tissues, engulfing and destroying bacteria with lysosomal enzymes.

Macrophages

Large agranular phagocytic cells derived from monocytes that reside in organ tissues (such as the lungs and spleen) to engulf cellular debris and pathogens and present non-self antigens to lymphocytes.