Structure and
Function of The Cell
Reference:
Modern Biology
CHAPTER 4
Introduction to the Cell
Modern Biology
Chapter 4 Sect. 4 – 1
Pgs. 69-72
BIG IDEAS
**Cells distinguish living things from all other matter
– they are the “building blocks of life”
**A cell is the smallest unit that can carry on all the
processes of life.
**There is a relationship between a cell’s function
and its structure (size and shape)
Bill Nye The Science Guy!
Introduction to CELLS
Discovery of the CELL
The Microscope - the discovery of the
microscope in the early 1600’s.
– Robert Hooke – 1665 – Viewed “little boxes” –
coined the name “cell”.
– Anton van Leeuwenhoek – 1673 – Viewed the first
living organisms-protozoa, bacteria – “animalcules”
– Matthias Schlieden – 1838 – Concluded that all
plants are made of cells
– Theodor Schwann – 1839 – Concluded that every
animal is made of cells
– Rudolf Virchow - 1855 – Concluded that cells can
only come from other living cells
Observations began by Hooke & van Leeuwenhoek and
later confirmed by
Schleiden, Schwann and Virchow
were organized by scientists into a unified
theory known as:
THE CELL THEORY
1. All living things are composed of cells.
EXPLANATION.A living being is either a cell or is made up of cells.
2. Cells are the basic unit of structure and function in an
organism.
EXPLANATION. Any part of cell cannot be called living. It is the
whole cell which can be called living. In other words it is the smallest
living unit.
3. All cells come from the reproduction of other cells.
EXPLANATION. New cells arise by cell division of pre-existing cells.
This holds good for all cells, but not for the first cell that arose by
chemosynthesis.
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The Cell Theory !
THE CELL
Cell - the smallest unit that can carry out all
the processes of life (take in nutrients, get
rid of waste, etc)
– Every living thing is made of one or more cells.
• Unicellular-complete living thing made of only
one cell
– Example: amoeba, paramecium
• Multicellular-living thing made of more than one
cell
– Example: frogs, trees, coral, mushrooms,
humans
Unicellular – Each new
cell is identical to the
parent. All developing
organisms are exact
clones of their parents.
DIFFERENTIATION
Multicellular – Cells become
different (differentiation)
from each other as they
multiply. All developing
multicellular organisms are a
combination of two parents,
but are different from them –
not clones.
Egg cells are the biggest
single cells…
Just like one of these eggs, each
of you began as a single cell…
Cell Diversity
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Why are cells small?
DO NOW
Respond to the following in your
notebook:
Why do cells divide before they
get too big?
Cell Diversity
Not all cells are alike…they can differ in
size shape and internal organization
*SIZE: Cells come in all sizes, but most cells are very small
(microscopic) - Cell size is limited by the ratio of
volume to surface area.
Examples:
– Longest-giraffe nerve cell (2 meters)
– Smallest-bacteria (0.2 micrometers)
– Largest - egg cells
Some differently sized cells …
The cell body of a motor neuron is
approximately 100 µm (0.1
millimeter) in diameter and the
axon is about 1 meter (1,000
millimeter) in length.
The bacterium, Haemophilus influenzae
(it was once thought to cause the flu)
is among the smallest bacteria - 0.5–
2.0 µm in length - which is about the
smallest object that can be seen
through a light microscope.
*SHAPE
– Cells have a shape (structure) to fit
their function
• Examples:
– Nerve cell-has extensions (axons) to allow
it to transmit and receive nerve impulses
– Skin cells-flat to cover body surface
– White blood cells-can change shape to
squeeze into spaces to isolate bacteria
that invade the body.
Cell Diversity
Some differently shaped cells
*INTERNAL ORGANIZATION
Cells contain internal structures that help it carry
out all of its functions.
In other words :
“FORM FITS FUNCTION”
• For example - Every cell in your body contains
organelles (structures that have specific
functions).
– Just like organs in the body, each organelle contributes
in its own way to helping the cell function well as a whole.
• Examples:
– Cell Membrane – surrounds the cell
– Nucleus – contains most of the cells genetic
material; directs most of the cells activities
“Form Fits Function”
How does the Form (shape / structure) of a
cell help it to do its Function (job)?
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