H Flashcards
Haemoglobin
The red pigment in red blood cells that combines with oxygen to form oxyhaemoglobin.
Haploid nucleus
A nucleus containing a single set of unpaired chromosomes (e.g. sperm and egg).
Hepatic portal vein
The vein through which absorbed food travels from the small insetting to the liver.
Herbicide
A chemical that kills weeds.
Herbivore
An animal that feeds only on plants.
Heroin
A highly addictive, depressant drug derived from opium extracted from poppies.
Heterozygous
A genotype where the alleles of a gene are different.
HIV (human immunodeficiency virus)
The virus that causes AIDS. HIV attacks and destroys lymphocytes reducing the body’s ability to defend itself against disease.
Homeostasis
Maintenance of a constant internal environment. This involves controlling factors, such as temperature and the concentration of glucose in the blood.
Homologous chromosomes
A pair of matching chromosomes that carry genes for the same characteristics in the same positions.
Homozygous
A genotype where both alleles of a gene are identical .
Hormone
A chemical messenger produced by an endocrine gland that is transported in the blood and alters activity of one or more specific target organs. Hormones are destroyed by the liver.
Hydrophyte
A plant that is adapted to living in water.
Hypha
(plural: hyphae) Thin thread-like structure that is part of the body (mycelium) of a mould fungus.
