GCSE Bio unit 2.2/2.3 (AQA - Animal tissues, organs, and systems)

Digestive system

An organ system in which several organs work together to digest and absorb food.

Lock and key theory

A model of enzyme action where the substrate fits precisely into the complementary shape of the enzyme's active site.

Carbohydrases

Enzymes that break down complex carbohydrates into simple sugars.

Amylase

A specific carbohydrase that catalyses the breakdown of starch into sugars.

Proteases

Enzymes that break down proteins into individual amino acids.

Lipases

Enzymes that break down lipids (fats) into glycerol and fatty acids.

Bile

An alkaline substance produced in the liver and stored in the gall bladder that neutralises stomach acid and emulsifies fats to increase surface area.

Benedict's test

A qualitative food test used to detect reducing sugars, which turns from blue to green, yellow, or brick red upon heating.

Iodine test

A qualitative food test used to identify starch, turning from yellow-brown to blue-black in its presence.

Biuret test

A qualitative chemical test that detects the presence of proteins, changing from blue to purple/lilac.

Double circulatory system

A circulatory system where blood travels through the heart twice in one complete circuit around the body.

Right ventricle

The heart chamber that pumps deoxygenated blood to the lungs for gaseous exchange.

Left ventricle

The thick, muscular heart chamber that pumps oxygenated blood at high pressure around the entire body.

Natural pacemaker

A specialised group of cells located in the right atrium that controls the resting heart rate by generating electrical impulses.

Arteries

Thick-walled blood vessels with muscle and elastic fibres that transport blood under high pressure away from the heart.

Veins

Blood vessels with thinner walls, larger lumens, and valves that transport blood back to the heart under low pressure.

Capillaries

Narrow, single-cell-thick blood vessels that permit the exchange of substances between blood and body tissues.

Blood plasma

The pale yellow liquid portion of blood in which red blood cells, white blood cells, platelets, and dissolved substances are suspended.

Platelets

Small cell fragments suspended in blood plasma that play an essential role in blood clotting.

Coronary heart disease

A non-communicable condition caused by the build-up of fatty deposits inside coronary arteries, restricting blood flow and oxygen to the heart muscle.

Stents

Metal mesh tubes inserted into narrowed coronary arteries to keep them open and restore blood flow.

Statins

Prescription medications used to lower blood cholesterol levels, thereby slowing down the deposition of fatty material in arteries.

Health

The state of complete physical and mental well-being.

Benign tumour

A mass of abnormal cells contained in one local area (often enclosed in a membrane) that does not invade neighbouring tissues.

Malignant tumour

A cancerous mass of cells that invades surrounding tissues and can enter the bloodstream to form secondary tumours elsewhere in the body.

Carcinogen

An agent, substance, or form of radiation (such as ionising radiation) capable of causing cancer.