This document summaries all of the different organelles present on eukaryotic cells. These include, the nucleus, mitochondria, chloroplast, endoplasmic reticulum, ribosomes, Golgi apparatus, lysosomes, cell wall and vacuole.
Nucleus
The nucleus is the most prominent feature of a cell containing the
organism’s hereditary material and
controlling the cell's activity.
Nuclear envelope - This is a double
membrane that surrounds the nucleus.
The outer membrane is continuous with
the endoplasmic reticulum and often
has ribosomes on its surface (for
protein synthesis). The membrane
controls the entry and exit of materials
and contains reactions that take place
within the nucleus.
Nuclear pores - These allow passage of
large molecules such as mRNA out of
the nucleus. They are around 3,000
pores in every nucleus.
Nucleoplasm - This is a granular, jelly like material that makes up the
bulk of the nucleus.
Chromatin - This consists of protein bound linear DNA.
Nucleolus - This is a small, spherical region within the nucleoplasm that
manufactures rRNA and assembles the ribosomes, there can be more
than one nucleolus in a single nucleus.
The function of a nucleus - Act as a control center of the cell through
mRNA and tRNA and hence protein synthesis, retain the genetic
material of the cell in the form of DNA and chromosomes and
manufacture rRNA and ribosomes.
, Mitochondria
The mitochondria is where the aerobic stages of respiration take place
(the krebs and oxidative phosphorylation). It is responsible for the
production of the energy-carrier molecule, ATP, from respiratory
substrates, such as glucose. The number and size of mitochondria are
higher in cells that have a high metabolic activity and therefore require a
large amount of ATP. Examples of high metabolically active cells include
the muscle and epithelial cells.
Mitochondria envelope - Around
the organelle is a double
membrane, the inner membrane
and the outer membrane. The
membrane controls the entry and
exit of material. The inner
membrane is folded to form
extensions called cristae.
Cristae - These are extensions of
the inner membrane, which some
extend across the whole width of
the mitochondria. They provide a
large surface area for the attachment of enzymes and other proteins that
are involved in the respiratory process.
Matrix - This makes up the remainder of the mitochondria. Within the
matrix it will contain molecules such as DNA, protein, lipids and
ribosomes. The DNA within the matrix allows the control of the
production of its own proteins. Many of the enzymes in the matrix are
used for respiration.
The mitochondria has its own DNA that is circular like in a prokaryotic
cell, which is believed to be evidence to show that it originated from
prokaryotic cells that were engulfed by larger cells. This is known as
endosymbiosis.
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