LESSON 1.
CELLS & TISSUES
Lesson Aim
To explain the human body at a microscopic level, including the structure and function of
cells, tissues and membranes.
THE CELL
All living matter is composed of functional units called cells. At one end of the scale in the
animal kingdom, there are unicellular organisms composed of a single cell (eg. Protozoa
or Amoeba). In an amoeba all the vital processes of the animal take place inside a single
cell.
Cells are capable of digesting food, growing, respiring, excreting, secreting, reproducing
and responding to stimuli. All these things happen in a single-celled animal.
At the other end of the scale, there are the multi-cellular organisms such as the higher
animals and humans. In these organisms, the cells become specialised, and one or more
of these different functions may be lost.
Parts of the Human Cell
The various parts of the human cell and their functions are:
Cell Membrane
This is the outer layer of the cell. It gives the cell its shape and holds the liquid inside the
cell. This membrane is a semi-permeable membrane which means it allows certain things
to pass in and out of the cell.
Nucleus
The nucleus contains the nucleolus; this is the part of the cell which holds the genetic
material, the chromosomes and chromatin which are concerned with reproduction of the
cell.
Nucleolus
A spherical body inside a nucleus made of protein, RNA and DNA. The nucleolus is
involved in the synthesis and storage of ribosomal RNA.
Cytoplasm
This is the fluid inside the cell which contains salts and sugars in solution.
Golgi Apparatus
This stores food inside the cell. Also note the fat droplets which float about in the
cytoplasm and are also a means of storing food in the form of fats. Also called Golgi
complex.
Lysosomes
These are digestive centres in the cell and help to digest and break down food material.
Centriole
This is concerned with cell division, the reproduction of the cell and the movement of cell
, chromosomes.
Mitochondrion
This is concerned with the respiration of the cell. As the end product of all respiration is
energy, it is also a source of energy. (Plural + mitochondria).
Endoplasmic Reticulum
This is the part where protein is manufactured or built up from nitrogen.
Fibrils
These are concerned with nervous responses.
Microtubule
These are tiny tubes inside the cells.
Microvilli
Tiny finger like bumps in the surface of the cell (ie. bumps in the cell wall)
These serve to increase the surface area of the cell, hence improving the ability to absorb
particles into the cell.
Cilia
Long hair or tail like structure projecting from a single cell, used to propel the cell (enables
it to move or swim).
Chromatin
A mass of thread like genetic material, mainly DNA, present inside the nucleus when the
cell is not dividing/reproducing.
Nuclear Envelope
Wall of material surrounding/containing the nucleus.
Glycogen
Complex polymer (compound) of glucose. This acts as a storage/supply of glucose on
liver and muscle cells.
Peroxisome
Similar to lysosomes; an organelle containing enzymes that use oxygen to oxidise different
organic compounds. These are common in liver cells.
Microfilament
A filament of protein. They are contractile units in muscle cells.
They provide support, shape and movement in non-muscle cells.
Free Ribosomes
An organelle suspended in cytoplasm that synthesises proteins.
Contains ribosomal RNA and ribosomal proteins.
Secretory Vesicle
Tiny bladder or sac in the cell that secretes or expels unwanted material.
Although the cell is very, very small, you can see that it contains many different parts It
also carries out many different functions.
CELLS & TISSUES
Lesson Aim
To explain the human body at a microscopic level, including the structure and function of
cells, tissues and membranes.
THE CELL
All living matter is composed of functional units called cells. At one end of the scale in the
animal kingdom, there are unicellular organisms composed of a single cell (eg. Protozoa
or Amoeba). In an amoeba all the vital processes of the animal take place inside a single
cell.
Cells are capable of digesting food, growing, respiring, excreting, secreting, reproducing
and responding to stimuli. All these things happen in a single-celled animal.
At the other end of the scale, there are the multi-cellular organisms such as the higher
animals and humans. In these organisms, the cells become specialised, and one or more
of these different functions may be lost.
Parts of the Human Cell
The various parts of the human cell and their functions are:
Cell Membrane
This is the outer layer of the cell. It gives the cell its shape and holds the liquid inside the
cell. This membrane is a semi-permeable membrane which means it allows certain things
to pass in and out of the cell.
Nucleus
The nucleus contains the nucleolus; this is the part of the cell which holds the genetic
material, the chromosomes and chromatin which are concerned with reproduction of the
cell.
Nucleolus
A spherical body inside a nucleus made of protein, RNA and DNA. The nucleolus is
involved in the synthesis and storage of ribosomal RNA.
Cytoplasm
This is the fluid inside the cell which contains salts and sugars in solution.
Golgi Apparatus
This stores food inside the cell. Also note the fat droplets which float about in the
cytoplasm and are also a means of storing food in the form of fats. Also called Golgi
complex.
Lysosomes
These are digestive centres in the cell and help to digest and break down food material.
Centriole
This is concerned with cell division, the reproduction of the cell and the movement of cell
, chromosomes.
Mitochondrion
This is concerned with the respiration of the cell. As the end product of all respiration is
energy, it is also a source of energy. (Plural + mitochondria).
Endoplasmic Reticulum
This is the part where protein is manufactured or built up from nitrogen.
Fibrils
These are concerned with nervous responses.
Microtubule
These are tiny tubes inside the cells.
Microvilli
Tiny finger like bumps in the surface of the cell (ie. bumps in the cell wall)
These serve to increase the surface area of the cell, hence improving the ability to absorb
particles into the cell.
Cilia
Long hair or tail like structure projecting from a single cell, used to propel the cell (enables
it to move or swim).
Chromatin
A mass of thread like genetic material, mainly DNA, present inside the nucleus when the
cell is not dividing/reproducing.
Nuclear Envelope
Wall of material surrounding/containing the nucleus.
Glycogen
Complex polymer (compound) of glucose. This acts as a storage/supply of glucose on
liver and muscle cells.
Peroxisome
Similar to lysosomes; an organelle containing enzymes that use oxygen to oxidise different
organic compounds. These are common in liver cells.
Microfilament
A filament of protein. They are contractile units in muscle cells.
They provide support, shape and movement in non-muscle cells.
Free Ribosomes
An organelle suspended in cytoplasm that synthesises proteins.
Contains ribosomal RNA and ribosomal proteins.
Secretory Vesicle
Tiny bladder or sac in the cell that secretes or expels unwanted material.
Although the cell is very, very small, you can see that it contains many different parts It
also carries out many different functions.
