Cell Structure
& Function
Did You Know?
The average human is composed of over
100 Trillion individual cells!!!
It would take up to 50 cells to cover the
dot in the letter i
Definition of Cell
A cell is the smallest unit that is
capable of performing life functions.
Recall from your studies in
characteristics of life the
organization of living organisms
Cells
Tissues
Organs
Organ Systems
Organism
Cell Theory
• All living things are made up of cells.
• Cells are the smallest working units of all living
things.
• All cells come from preexisting cells through
cell division.
Cell Specialization and
Organization
Cells are the basic unit of structure and
function in living things
Serve a specific function within the
organism
Examples: blood cells, nerve cells,
bone cells, skin cells, etc…
Examples of Cells
Amoeba Proteus
Plant Stem
Bacteria
Red Blood Cell
Nerve Cell
Level 2—Tissues
Made up of cells that are similar in structure and
function that work together to perform a specific
activity
Examples: blood, nervous, bone, etc. In
humans, we have 4 types of tissue: connective,
epithelial, muscle, and nerve
Level 3--Organs
Made up of tissues that work
together to perform a specific
function
Examples: heart, brain, kidney,
skin
Level 4—Organ Systems
Groups of two or more organs that work
together to perform a specific function for the
organism
Examples—Circulatory System, Nervous
System, Digestive System
Level 5--Organism
Entire living things that can carry out all basic life processes.
They can take in materials, release energy from food, release
waste, grow, respond to the environment, etc…remember the 6
characteristics of living organisms???
Organisms are usually made up of organ systems, but an
organism may only be made up of one cell as is the case
with bacteria
Examples—human, bacterium, amoeba, euglena,
mushroom, sunflower
Discovery of Cells
Scientists who were instrumental in the
discovery of cells and the development of
the Cell Theory:
Robert Hooke
Anton van Leuwenhoek
Matthias Schleiden & Theodore Schwann
Louis Pasteur & Francisco Redi
Robert Hooke
• Discovered Cells while
viewing a cork under a
microscope
Anton van Leuwenhoek
• Observed single-celled
organisms in pond
water
• Observed blood cells
Matthias Schleiden &
Theodore Schwann
Said that plant parts and
animal tissues were made of
cells
Louis Pasteur & Francisco Redi
Disproved the Theory of
Spontaneous Generation
Two Types of Cells
•Prokaryotic
•Eukaryotic
Prokaryotic
• Do not have
structures
surrounded by
membranes
• Few internal
structures
• One-celled
organisms, Bacteria
Eukaryotic
• Contain organelles surrounded by membranes
• Most living organisms
Plant
Animal
“Typical” Animal Cell
“Typical” Plant Cell
Cell Parts
Organelles
Surrounding the Cell
Cell Membrane
• Outer membrane of cell
that controls movement in
and out of the cell
• Double layer
Cell Wall
• Most commonly found
in plant cells & bacteria
• Supports & protects
cells
Inside the Cell
Nucleus
• Directs cell activities
• Separated from cytoplasm by nuclear
membrane
• Contains genetic material - DNA
Cytoplasm
• Gel-like mixture
• Surrounded by cell membrane
• Contains hereditary material
Chloroplast
• Usually found in plant
cells
• Contains green
chlorophyll
• Where photosynthesis
takes place