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Paramecium
Human Cheek Cells
Onion Cells
OVERVIEW OF THE CELL
Biology 20
Before we could see cells..
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There had to be the
microscope!
 Early lens makers
(often physicists)
allowed for the
study of
microbiology

The first people to see cells...
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

Robert Hooke - He
was looking at cork
and noted that he saw
a “great many boxes”
(1665).
Anton van
Leeuwenhock –
observed living cells in
pond water. He called
these “animalcules”.
(1673)
The first people to see cells...
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


Theodore Schwannobserved that the tissues
of animals had cells
(1839)
Mattais Schleiden–
observed that plants
contained cells (1845)
Rudolf Virchow – every
living thing is made up of
cells (1850)
The Cell Theory
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1.
2.
3.
Every living organism is made of one or more
cells.
The cell is the basic unit of structure and function.
It is the smallest unit that can perform life
functions.
All cells arise from pre-existing cells.
Question for you...
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
Why is the Cell Theory called a Theory and not a
Fact?
Main Points
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
All organisms are made up of cells. They can be:
•
•


Unicellular (1 cell)
OR multicellular (many cells)
In unicellular organisms all life functions are
carried out by a single cell.
In multicellular organisms, cells specialise to
perform specific functions – division of labour.
Cells as seen with a microscope
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


Living protoplasm
surrounded by surface
membrane (& non-living
cell wall in plants).
The living material
between the nucleus and
the cell surface membrane
is known as cytoplasm.
Cytoplasm contains variety
of cell organelles.
Two main types of cells
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Prokaryotic Cells
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



Very simple cells, probably
first to inhabit the earth.
Do not contain a membrane
bound nucleus. Their nucleus
material (DNA) lies free in a
region known as nucleoid.
Example: Bacteria. DNA of
bacteria is circular.
The word "prokaryote"
means "before the nucleus"
Eukaryotic Cells
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


More advanced cells.
Possess true nucleus and
nucleus material are found
inside the nucleus
surrounded by the two
membranes, i.e nucleus
envelope.
Example: plant cell, animal
cell.
Eukaryotic Cells
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4 main parts:
•
•
•
•
cell membrane - outer boundary
cytoplasm - jelly-like fluid
interior
nucleus - the "control center”,
contains the cell's DNA
(chromosomes)
organelles - "little organs" that
carry out cell functions
Organelles in Animal & Plant Cells
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Animal Cell
Plant Cell
Diagram
Cell Part
Function
Mitochondria
Energy center or
"powerhouse" of the cell.
Turns food into useable
energy
Ribosomes
Make protein
Golgi Apparatus
Processes, packages and
secretes proteins. Like a
factory.
Lysosome
Contains digestive enzymes,
breaks things down
Endoplasmic Reticulum
Transport, "intracellular
highway". Ribosomes are
positioned along the rough
ER, protein made by the
ribosomes enter the ER for
transport.
Smooth ER - no ribosomes
Rough ER - ribosomes
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Diagram
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Cell Part
Function
Nucleolus
Located inside the nucleus,
makes ribosomes
Vacuole
Stores water or other
substances, plant cells contain
a large central vacuole.
Chloroplast
Uses sunlight to create food,
photosynthesis (only found in
plant cells)
Cell Wall
Provides additional support
(plant and bacteria cells)
Microtubules
Part of the cytoskeleton,
function in support
Also make up cilia and
flagella (cell movement)
Differences in Animal & Plant Cells
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Found only in Animal Cells

Lysosomes
Found Only in Plant Cells



Cell Wall
Chloroplasts
Chromoplasts/Amyloplasts
Prokaryotic versus Eukaryotic Cells
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Prokaryotic cell
Eukaryotic cell
Nucleus material are not enclosed by nuclear
membrane
Nucleus material are enclosed by nuclear
membrane
Contains few organelles
Contains many organelles
No membrane bounded organelles such as;
chloroplast and mitochondria
Has membrane bounded organelles
DNA is circular and lies free in cytoplasm
DNA is linear and enclosed in nucleus
No mitosis or meiosis, divide by binary fission
Mitosis and meiosis occur
It contains 70s ribosome (smaller)
It contains 80s ribosome (larger)
Mainly unicellular
Mainly multi-cellular