2. CELL
Cell is the basic structural and functional
unit of life.
It is the smallest unit that can carry out
all activities of life.
Cells vary from single cell organisms
(bacteria) to multi cellular structures
(tissues, organs) and organisms (plants
and animals).
Building blocks of complex multicellular
organisms.
4. EMERGENCE AND IMPLICATIONS OF CELL THEORY
Cell was discovered by Robert Hooke in 1665. The discovery of
the cell was made possible through the invention of the
microscope.
Hooke first observed cell in thin slices of bottle cork.
Book Micrographia. He gave 60 'observations' in detail of
various objects under a coarse, compound microscope.
Discovered many tiny pores that he named cells. He described
the cells as tiny boxes or a honeycomb. He thought that cells
only existed in plants and fungi.
Cell is an empty space bounded by thick walls. Hooke was
unable to see that there were other internal components to
the cells he was observing.
Spontaneous generation, from either natural or artificial heat,
was the cause.
5. EMERGENCE AND IMPLICATIONS OF CELL THEORY
Anton van Leeuwenhoek (1673) used a
handmade microscope to observe pond scum
and discovered single-celled organisms. He
called them animalcules.
He made use of a microscope containing
improved lenses - magnify objects 270-fold.
Leeuwenhoek found motile objects. In a letter
to The Royal Society on October 9, 1676, he
stated that motility is a quality of life
therefore these were living organisms.
6. EMERGENCE AND IMPLICATIONS OF CELL THEORY
Lorenz Oken (1805) a German scientist – “all living
beings originate from or consist of vesicles or cells”.
Jean Baptist de-Lamarck (1809) – “no body can have
life if its constituent parts are not cellular tissue or are
not formed by cellular tissue”.
In 1831, Robert Brown reported the presence of
nucleus.
7. DEVELOPMENT OF CELL THEORY
1838 – German Botanist, Matthias Schleiden,
concluded that all plants parts are made of cells.
1839 – German Zoologist, Theodor Schwann, who
was a close friend of Schleiden, stated that all
animal tissues are composed of cells.
Both working independently, came out with a
theory called the Cell Theory.
Found that the cell consisted of 3 basic parts –
nucleus, the fluid (cytoplasm), outer membrane
(plasma membrane).
Cell wall, was an additional structure, present only
in plant cell.
8. DEVELOPMENT OF CELL THEORY
All organisms are composed of one or more cells.
Cell is the basic structural as well as functional unit for all
organisms.
All cells arise from pre-existing cells.
9. DEVELOPMENT OF CELL THEORY
1855 – Rudolf Virchow, German physician – new
cells were formed only by the division of previously
existing living cells.
Contrary to the idea of “abiogenesis” (living things
arise spontaneously from non-living things).
Louis Pasteur (1862), supplied experimental proof
for Virchow’s hypothesis.
https://www.youtube.com/watch?v=_ZzJ6NcmiKU
- (Pasteur's Swan Necked Flask Experiments)
10. DEVELOPMENT OF CELL THEORY
August Weismann (1880) – all presently living
cells have a common origin because they have
basic similarities in structure and molecules etc.
Fundamental similarities in the chemical
composition, metabolic activities and structure of
the cells.
Cells are basically similar but extraordinarily
versatile.
11. MODERN CELL THEORY
All known living things are made up of one or more cells.
The cell is the fundamental unit of structure and function in all living organisms.
All living cells arise from pre-existing cells by division.
Cells contain hereditary information (DNA) which is passed on from cell to cell
during cell division.
All cells are basically the same in chemical composition and metabolic activities
in organisms of similar species.
All basic chemical and physiological functions are carried out inside the cells (e.g.,
digestion).
Cell activity depends on the activities of sub-cellular structures within the cell
(organelles; e.g., nucleus).
12. USES OF CELL THEORY
Cell theory is one of the fundamental principles of biology, and it’s
so important.
Knowing that all living things are made up of cells allows us to
understand how organisms are created, grow, and die.
That information helps us understand how new life is created, why
organisms take the form they do, how cancer spreads, how diseases
can be managed, and more.
Cells even help us understand fundamental issues such as life and
death.
13. CELL AS A UNIT OF STRUCTURE AND FUNCTION
Unit of structure and function.
Division of labour among cells in multicellular organisms.
The function of the organism as a whole is the result of the sum of
activities and interactions of different cells, and of different
components of the cell.
Examples: Muscle cells, Nerve cells, Red Blood cells.
Great variation in shape and size.
15. TYPES OF CELLS IN THE HUMAN BODY
There are over 200 different cell types in the human body.
Each type of cells is specialized to carry out a particular function,
either solely, but usually by forming a particular tissue.
16. TYPES OF CELLS IN THE HUMAN BODY
Stem cells:
Before a cell becomes specialised, it first
starts out as a stem cell.
Pluripotent - they have the potential to
become any type of cell in the body.
The ancestors of all cells in the body.
Have the power to replicate into healthy
cells in order to speed up regeneration after
certain pathological conditions.
Cell differentiation: The process that allows
stem cells to transform into any kind of cell.
17. TYPES OF CELLS IN THE HUMAN BODY
Red blood cells:
Red blood cells are known as erythrocytes,
and are the most common type of blood cell.
They are shaped like a biconcave disc.
The main role of red blood cells is to transport
oxygen around the body using haemoglobin.
Haemoglobin is a molecule in red blood cells
that binds to oxygen, allowing it to be
transported through the blood.
18. TYPES OF CELLS IN THE HUMAN BODY
White blood cells:
White blood cells, also known as leukocytes, are
a vital component of the immune system.
Granulocytes contain granules in the cytoplasm
as agranulocytes do not.
Granulocytes include neutrophils, eosinophils
and basophils.
Agranulocytes include lymphocytes and
monocytes.
20. TYPES OF CELLS IN THE HUMAN BODY
Platelets:
An important component of the blood.
Are vital in the control of bleeding.
They are fragments of large cells called megakaryocytes which are
produced in the bone marrow.
They have surface proteins which allow them to bind to one
another, and to bind to damaged blood vessel walls.
Platelets are recruited when bleeding occurs.
They plug the source of the bleeding, coagulating and sticking
together to form a blood clot, together with a fibrous protein
known as fibrin.
https://www.youtube.com/watch?v=R8JMfbYW2p4
21. TYPES OF CELLS IN THE HUMAN BODY
Nerve cells:
Commonly known as neurons, transmit information throughout
the body in the form of electrical signals or nerve impulses.
The cell body contains a nucleus.
The axon is long and thin, and protrudes from the cell body and
can be myelinated or unmyelinated. Axons are responsible for
conducting electrical impulses in the form of action potentials.
Action potentials cause a change in voltage across the plasma
membrane.
Axons connect to other neurons via synapses, which are formed
by small branches at the end of the axon called axon terminals.
Impulses are received from other cells by dendrites, which are
multiple branching structures protruding from the cell body.
They convert chemical signals from the synapse into small
electrical impulses, and transmit them towards the cell body.
22. TYPES OF CELLS IN THE HUMAN BODY
Neuroglial cells:
Neuroglial cells, more commonly known as
glial cells or glia.
Are not involved in the conduction of nerve
impulses.
Glia are very common in the brain.
Are smaller than neurons, and do not have
axons or dendrites.
https://www.youtube.com/watch?v=AwES6R1
_9PM
23. TYPES OF CELLS IN THE HUMAN BODY
Muscle cells:
There are 3 types of muscle cells, known as myocytes.
1. Skeletal muscle cells: are attached to bones and tendons.
Responsible for voluntary movements.
2.Cardiac muscle cells: are also called cardiomyocytes
which together make up the most important muscular tissue
in the entire body, the tissue of the heart.
The cells contract in unison creating the contractions of
the heart.
3.Smooth muscle cells: are responsible for involuntary
contractions in hollow and visceral organs like the bladder
and lungs, and the walls of blood vessels.
Responsible for peristalsis, whereby food is propelled
through the digestive system via wavelike contractions.
24. TYPES OF CELLS IN THE HUMAN BODY
Cartillage cells:
Cartillage cells, also known as chondrocytes,
make up cartilage, a firm connective tissue that
is vital to the body’s structure.
Cartilage is found in joints between bones, in the
ears and nose, in the airways as well as other
locations.
It acts as a shock absorber throughout your
body. Cartilage at the end of your bones
reduces friction and prevents them from
rubbing together when you use your joints.
25. TYPES OF CELLS IN THE HUMAN BODY
Bone cells:
Osteoclasts: Osteoclasts are large multinucleated cells that are
involved in bone resorption. This is where the bone is broken
down during the process of renewal.
Osteoblasts: Osteoblasts have the opposite function, they are
involved in the generation of new bone. They are triggered to
create new bone by hormones such as vitamin D and estrogen.
Osteocytes: are found inside the bone. Osteocytes can sense
mechanical strain being placed on the bone, and secrete growth
factors which activate bone growth in response.
Lining cells: They line the surface of the bone and are responsible
for the release of calcium from the bone into the bloodstream
when it falls too low. They also work to protect the bone.
26. TYPES OF CELLS IN THE HUMAN BODY
Skin cells:
Keratinocytes: make up 95% of the epidermis. Keratinocytes generate the protein keratin, but are
also important in protecting the body by blocking toxins and pathogens, and preventing loss of heat
and moisture. Hair and nails are examples of fully keratinized epithelial cells.
Melanocytes: The role of melanocytes in the skin is to produce the pigment melanin, which
determines skin coloration.
Langerhans cells: These are dendritic cells involved in antigen processing when the skin becomes
infected, they act as antigen-processing cells.
Merkel cells: These act as mechanosensory cells and are involved in touch reception (the ability to
feel).
Other types of sensory cells are present within the skin, however are found in the deeper layers
and known as cutaneous receptors.
27. TYPES OF CELLS IN THE HUMAN BODY
Endothelial cells:
Are the cells that form the lining of blood vessels. They regulate exchanges
between the bloodstream and the surrounding tissues.
Signals from endothelial cells organize the growth and development of
connective tissue cells that form the surrounding layers of the blood-vessel wall.
Epithelial cells:
Epithelial cells make up the linings of cavities in the body such as the lungs, small
intestine and stomach.
Epithelial cells are innervated with nerve endings, and can become sensory cells.
Epithelial cells can also specialise to become secretory cells, that release mucous,
hormones and enzymes into the body.
28. TYPES OF CELLS IN THE HUMAN BODY
Fat cells:
Fat cells, also referred to as adipocytes and lipocytes are the cells of the body that are specialised
to store energy in the form of adipose tissue, or fat.
It provides energy, absorbs certain nutrients and maintains your core body temperature.
Sex cells:
Sex cells called gametes.
Male sex cells are commonly known as sperm cells, or spermatozoa, and female gametes are
known as eggs or ova. When they fuse together, fertilization occurs and a zygote is formed.
Spermatozoa: Spermatozoa are smaller, and have a head, a midpiece region and a long tail
(flagellum) for propulsion and motility.
Ova: Ova are very large compared to other cell bodies. They are round in shape and are produced
in the ovaries during embryological development.