Extras M Flashcards
Major histocompatibility complexes
Proteins
that may carry antigens within antigenpresenting
cells to the cell surface membrane
where they identify the cell as ‘foreign’ and
attract the attention of the immune system.
Other major histocompatibility complexes
(MHCs) identify cells as ‘self’ rather than
foreign.
Malignant
A tumour that destroys tissues
around it and is able to spread to other areas of
the body. Cells become detached from the
original tumour and are carried in the blood or
by the lymphatic system to other areas of the
body where they form secondary tumours.
Maltase
An enzyme that breaks down maltose to
two molecules of glucose. This reaction involves
hydrolysis. Seeds store carbohydrates as
starch. When the seed germinates, this starch is
broken down to maltose by amylase. The
maltose is then broken down to glucose by
maltase.
Mammal
Mammals are vertebrate animals that
share certain characteristics. All mammals feed
their young on milk secreted by mammary
glands, possess hair and sweat glands which play
an important role in temperature regulation, and
possess different types of teeth, which have
different functions. Humans, cattle, dogs and
cats are mammals, and so are bats and whales
Mangrove
A type of forest found in estuaries and
on muddy seashores in the tropics. There are
many different sorts of trees growing in a mangrove forest. Many of them have adaptations
which allow their roots to get oxygen even when
growing in thick mud.
Mannose
Mannose is a monosaccharide with six
carbon atoms in each of its molecules. It is one
of the substances that helps to bind together the
cellulose molecules in plant cell walls.
Maternal chromosome
One chromosome in
each pair of homologous chromosomes comes
from the mother. These are the maternal
chromosomes. The other comes from the father.
These are the paternal chromosomes.
Messenger RNA
Messenger RNA (mRNA)
carries information from DNA in the nucleus to
the cytoplasm for protein transcription.
Metabolic rate
A measurement of the rate of
energy release by the chemical reactions which
take place in the body. Metabolic rate is usually
measured in kJ m–2 h–1. This takes into account
the size of the person and the time, making it
easier to compare figures
Metabolise
A term that refers to chemical
reactions in the body. Drugs are eventually
metabolised into other substances in the body
and become less effective. For example,
molecules from food are metabolised in cellular
respiration.
Metamorphosis, Metamorphose
Metamorphosis
is the term used to describe the drastic changes
in body form during an individual’s lifetime. For
example, the adult corn borer is a moth, while
the immature stage is a larva which lives inside
a maize stem. The larva of this insect looks very
different from the adult. When the larva
becomes an adult, many changes occur, both
externally and internally.
Metastasis
A malignant tumour destroys the
tissues around it and is able to spread to other
areas of the body. Metastasis is where cells
become detached from the original tumour and
are carried in the blood or lymphatic system to
other areas of the body.
Micronutrient
A substance required by an
organism in very small amounts. Micronutrients
include vitamins and mineral ions. In mammals,
for example, iron is a micronutrient. Small
amounts are required to produce haemoglobin
and for some enzymes to work
Microorganism, Microbe, Microbial
An
organism that is too small to see without the aid
of a microscope. (The fruiting bodies of fungi
are an exception to this.) There are three main
groups of microorganism. These are viruses,
bacteria and fungi. Many microorganisms cause
diseases but bacteria and fungi also play a very
important role in decomposition and the
recycling of substances such as carbon.
Microorganisms are also called microbes
Micropyle
A small pore in the coat of a seed.
When a seed starts to germinate, water enters
through the micropyle.
