IB Biology Topic 6, IB Biology Topic 6

Topic 6.1

Absorption

Topic 6.1

Absorption

the movement of a substance, such as a liquid or solute, across a cell membrane by means of diffusion, osmosis, or active transport.

Topic 6.1

Amylase

an enzyme, found mainly in saliva and pancreatic fluid, that converts starch and glycogen into simple sugars.

Topic 6.1

Cellulose

a complex carbohydrate that is composed of glucose units, and forms the main constituent of the cell wall in most plants.

Topic 6.1

Circular muscles

the inner layer of smooth (involuntary) muscle of the muscle coat (muscularis externa) of the small intestine in which the muscle fibres encircle the lumen.

Topic 6.1

Dialysis

the separation of smaller molecules from larger molecules, or of dissolved substances in a solution by selective diffusion through a semi-permeable membrane.

Topic 6.1

Endopeptidase

any of a large group of enzymes that catalyse the hydrolysis of peptide bonds in the interior of a polypeptide chain or protein molecule.

Topic 6.1

Enzymes

proteins or conjugated proteins produced by living organisms and functioning as biochemical catalysts.

Topic 6.1

Epithelium

the thin tissue forming the outer layer of a body's surface and lining the alimentary canal and other hollow structures.

Topic 6.1

Glycogen

a polysaccharide that is the main form of carbohydrate storage in animals and occurs primarily in the liver and muscle tissue. It is readily converted to glucose when needed by the body to satisfy its energy needs.

Topic 6.1

Lipase

a pancreatic enzyme that catalyses the breakdown of lipids through the hydrolysis of the linkages between fatty acids and glycerol in triglycerides and phospholipids.

Topic 6.1

Liver

a large glandular organ located in the upper right side of the abdominal cavity active in the secretion of bile and various metabolic processes.

Topic 6.1

Longitudinal muscles (of the stomach)

the outer longitudinal layer of smooth muscles, continuous with that of the esophagus.

Topic 6.1

Lumen

the inner open space or cavity of the small intestine.

Topic 6.1

Macromolecule

a very large molecule, such as a polymer or protein, consisting of many smaller structural units linked together.

Topic 6.1

Mineral ions

individual elements with an electrical charge.

Topic 6.1

Monomer

a molecule that can combine with others to form a polymer.

Topic 6.1

Mucosa

a mucus-secreting membrane lining all bodily passages that are open to the air, such as the digestive tract.

Topic 6.1

Nucleic acids

complex compounds found in all living cells composed of bases, carbohydrates, and phosphoric acid. Nucleic acids in the form of DNA and RNA control cellular function and heredity.

Topic 6.1

Pancreas

a gland in vertebrates, lying behind the stomach, that secretes pancreatic juice into the duodenum and insulin and glucagon into the bloodstream.

Topic 6.1

Small intestine

the narrow, winding, upper part of the intestine where digestion is completed and nutrients are absorbed by the blood.

Topic 6.1

Starch

a polysaccharide composed of glucose units that occurs widely in plant tissues in the form of storage

Topic 6.1

Villus (plural villi)

one of the minute finger-shaped processes of the mucous membrane of the small intestine that serve in the absorption of nutrients.

Topic 6.1

Vitamin

any of various fat-soluble or water-soluble organic substances essential in minute amounts for normal growth and activity of the body and obtained naturally from plant and animal foods.

Topic 6.2

Aorta

the main artery of circulatory system that carries blood from the lef side of the heart to the arteries of all limbs and organs except the lungs.

Topic 6.2

Arteriole

a small terminal branch of an artery that connects with a capillary.

Topic 6.2

Artery

a vessel that carries blood away from the heart to organs through the body

Topic 6.2

Atrium (plural atria)

a chamber that receives blood returning to the heart.

Topic 6.2

Blood pressure

the hydrostatic force that blood exerts against the wall of a blood vessel

Topic 6.2

Capillary

a microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells to allow exchange with interstitial fluid.

Topic 6.2

Cardiac output

the volume of blood pumped per minute by the left ventricle of the heart.

Topic 6.2

Diastolic pressure

the minimum blood pressure during relaxation of heart muscles.

Topic 6.2

Elastic fibres

a thick, yellow connective-tissue fibre composed principally of elastin and characterized by giving great elasticity to tissues in the body.

Topic 6.2

Epinephrine

a hormone produced as a response to stress, also called adrenaline.

Topic 6.2

Medulla

the lowest part of the brain that controls autonomic and homeostatic functions.

Topic 6.2

Myogenic contraction

A contraction of the heart without external stimulation from a nerve.

Topic 6.2

Pacemaker

a specialized region of the right atrium that sets the rate of heart contraction, also called the sinoatrial (SA) node.

Topic 6.2

Pulmonary circulation

the separated circulatory system that links the lungs and heart in humans.

Topic 6.2

Pulse

the force of blood leaving the heart in one heartbeat; it is felt where arteries pass near the skin.

Topic 6.2

Systemic circulation

the separated circulatory system that links the heart to the rest of the body.

Topic 6.2

Systolic pressure

The maximum blood pressure caused by heart muscles contracting and pumping blood.

Topic 6.2

Valve

a membranous structure in a hollow organ or passage that folds or closes to prevent the return flow of the body fluid passing through it.

Topic 6.2

Vasoconstriction

when the circular muscles in the artery wall contract, narrowing the lumen.

Topic 6.2

Vasodilation

when the circular muscles relax, increasing the lumen size and hence blood flow to downstream tissues.

Topic 6.2

Vein

A vessel that returns blood to the heart.

Topic 6.2

Ventricles

the chambers on the left and right side of the heart that receive blood from the atria and contract to force it into the aorta and pulmonary artery respectively.

Topic 6.3

AIDS (Acquired immunodeficiency syndrome)

the name of the active HIV infection characterized by the reduction of T-cells and the appearance of characteristic secondary infections.

Topic 6.3

Antibiotic

a chemical that kills or inhibits growth of bacteria by deregulation of metabolic pathways.

Topic 6.3

Antibody

An antigen-binding protein produced by B-cells.

Topic 6.3

Blood clotting

the process by which blood becomes thick and stops flowing, forming a solid cover over any place where your skin has been cut or broken.

Topic 6.3

Clotting factors

proteins in the plasma that serve to activate various parts of the blood clotting process by being transformed from inactive to active forms. Also known as coagulation factors.

Topic 6.3

Fibrin

the activated form of the blood-clotting protein fibrinogen.

Topic 6.3

Fibrinogen

a protein in the blood plasma that is essential for the coagulation of blood and is converted to fibrin by the action of thrombin.

Topic 6.3

Gene

a section of DNA on a chromosome that controls a specific trait.

Topic 6.3

Lymphocyte

a white blood cell that could be a B-cell or a T-cell.

Topic 6.3

Metabolism

the totality of all the chemical processes in an organism, consisting of anabolic and catabolic mechanisms.

Topic 6.3

Memory cell

a long-lived cell of the immune system that has previously encountered a specific antigen and that upon re-exposure produces large amounts of antibody.

Topic 6.3

Mucous membranes

membrane lining all body passages and having cells and associated glands that secrete mucus. Also called mucosa.

Topic 6.3

Pathogen

any organism that causes disease, such as a bacterium or fungus.

Topic 6.3

Peniclilin

any of the antibiotic drugs obtained from penicillium moulds or produced synthetically, most active against gram-positive bacteria and used in the treatment of various infections and diseases.

Topic 6.3

Phagocytic white blood cells

a type of white cell that carries endocytosis of large foreign substances.

Topic 6.3

Plasma cell

any of the antibody-producing cells, and derived from B-cells. It plays a major role in antibody-mediated immunity reacting with a specific antigen.

Topic 6.3

Platelet

a small fragment of red blood cells found in the blood plasma that functions to promote blood clotting.

Topic 6.3

Thrombin

a protease in blood that facilitates blood clotting by converting fibrinogen to fibrin.

Topic 6.3

Thrombus

a clot formed in the coronary arteries.

Topic 6.4

Alveolus (plural alveoli)

air sac that constitutes the gas exchange surface of the lungs.

Topic 6.4

Antagonistic muscle

a muscle that opposes the action of another.

Topic 6.4

Bronchi

the two main branches of the trachea that go into the lungs; this then further divides into the bronchioles and alveoli.

Topic 6.4

Bronchioles

any of the fine, thin-walled, tubular extensions of a bronchus.

Topic 6.4

Concentration gradient

the gradient resulting from an unequal distribution of ions across the cell membrane.

Topic 6.4

Diaphragm

a dome-shaped muscular partition separating the thorax from the abdomen. It plays a major role in breathing as its contraction increases the volume of the thorax and so inflates the lungs.

Topic 6.4

Emphysema

a chronic respiratory disease where there is over-inflation of the air sacs (alveoli) in the lungs causing a decrease in lung function and often breathlessness.

Topic 6.4

Epidemiology

the study of the incidence and causes of disease.

Topic 6.4

Expiration

when the muscles of the thorax contract to cause the volume to decrease, this increases the pressure in the lungs and air moves from the higher pressure inside the lungs to the lower pressure outside the body.

Topic 6.4

Inspiration

when the air moves from a higher pressure (outside the body) to the lower pressure (inside the lungs).

Topic 6.4

Intercostal muscles

muscles found between the ribs. They are mainly involved in the mechanical aspect of breathing.

Topic 6.4

Pneumocyte

one of the cells lining the alveoli (the air sacs) in the lung that assists in gas exchange and in the secretion of pulmonary surfactant.

Topic 6.4

Spirometer

an instrument for measuring the volume of air entering and leaving the lungs.

Topic 6.4

Surface tension

the force that causes the molecules on the surface of a liquid to be pushed together and form a layer.

Topic 6.4

Surfactant

a substance composed of lipoprotein that is secreted by the alveolar cells of the lung and serves to maintain the stability of pulmonary tissue by reducing the surface tension of fluids that coat the lung.

Topic 6.4

Tidal volume

the volume of air inspired or expired in a single breath during regular breathing.

Topic 6.4

Trachea

thin-walled, cartilaginous tube descending from the larynx to the bronchi and carrying air to the lungs.

Topic 6.4

Ventilation rate

the volume of air passing into and out of the lungs per minute.

Topic 6.5

Acetylcholine

a molecule released by neurons at the neuromuscular junction that causes muscle contraction.

Topic 6.5

Action potential

a localized change in electrical potential, from about -70 mV to +30 mV and back again, that occurs across a nerve fibre during transmission of a nerve impulse.

Topic 6.5

Axon of neurons

the long thread-like extension of a nerve cell that conducts nerve impulses from the cell body.

Topic 6.5

Cholinergic synapse

a junction between two cells that employs acetylcholine as its transmitter substance.

Topic 6.5

Depolarization

a positive-going change in the membrane potential of neurons making it more positive, or less negative. It may result in an action potential.

Topic 6.5

Myelination

the process of development or formation of a myelin sheath around a nerve fibre.

Topic 6.5

Neuron

a specialized, impulse-conducting cell that is the functional unit of the nervous system, consisting of the cell body and its processes, the axon, and dendrites.

Topic 6.5

Neurotransmitter

a substance that transmits nerve impulses across a synapse.

Topic 6.5

Oscilloscope

an electronic instrument used to observe and measure changing electrical signals.

Topic 6.5

Presynaptic neuron

a neuron from which an electrical impulse is transmitted across a synaptic clef to a postsynaptic neuron by the release of a chemical neurotransmitter.

Topic 6.5

Refractory period

the delay afer repolarization where the resting potential is restored.

Topic 6.5

Repolarization

the change in membrane potential that returns the membrane potential to a negative value afer the depolarization phase of an action potential.

Topic 6.5

Resting potential

the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse.

Topic 6.5

Saltatory conduction

the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

Topic 6.5

Synapses

the junction between two nerve cells, consisting of a minute gap across which impulses pass by neurotransmitters.

Topic 6.5

Threshold potential

the critical level to which the membrane potential must be depolarized in order to initiate an action potential.

Topic 6.6

Adipose tissue

A type of connective tissue that contains stored cellular fat.

Topic 6.6

Alpha cells (α-cells)

endocrine cells in the pancreas that synthesize and secrete glucagon, which elevates the glucose levels in the blood.