Cell Theory and Structure
All you ever wanted to know
about cells but were afraid
to ask.
Cell Theory and Structure
Cell Theory: There are three parts.
1. All organisms are composed of one or more cells.
2. The cell is the basic unit of life.
3. All cells come from existing cells.
Cell Theory and Structure
Cell Types:
Eukaryotic Cells
- Nucleus
- Membrane-covered organelles
- Linear DNA inside the nucleus
- All cells except bacteria
Prokaryotic Cells
- No nucleus
- No membrane-covered organelles
- Circular DNA floating in the cell
- Bacteria
Cell Theory and Structure
Cell Structure: Overview
1. The cell functions much like a factory. Do you
remember the exercise we did with the PBC
Factory?
2. Organelles within the cell must function together in
order to meet the cell’s needs. If cells within an
organism do not function properly, the organism will
suffer ill effects and possibly death.
3. All cells come from existing cells. The cells that
make up your body are constantly being replaced
by cells that are already there.
Cell Theory and Structure
Cell Structure: The Nucleus and Nucleolus
(Eukaryotic cells only)
1.
2.
3
The nucleus is like the brain of the cell. It controls the cell type and
relays instructions on what to do to the rest of the cell.
The nucleus contains DNA. The cell’s DNA is a set of instructions
on how to make proteins. Without proteins, the cell would die.
The dark spot inside the nucleus is the nucleolus. Basically, the
nucleolus helps in making ribosomes in the cytoplasm.
Cell Theory and Structure
Cell Structure: The Endoplasmic Reticulum
1.
2.
3.
The endoplasmic reticulum (ER) delivers messages and materials
to various parts of the cell. It acts like a tunnel throughout the cell.
The ER also breaks down harmful chemicals in the body that could
destroy the cell.
Another important function of the ER is to make lipids (fats) that
form the membranes around organelles and the cell.
Cell Theory and Structure
Cell Structure: The Ribosomes
1.
2.
3.
The ribosomes of a cell act like an assembly line at a factory. Their
main job is to assemble proteins by hooking together amino acids.
These proteins will be used throughout the organism for the
construction of cells and organelles. Proteins also help control
critical functions of the cell. Think of proteins as the building blocks
of cells and cells as the building blocks of all organisms.
Ribosomes are the smallest of cell organelles and do not have
membranes.
The nucleolus produces ribosomes, which are responsible for
making proteins.
Cell Theory and Structure
Cell Structure: The Golgi Bodies or Golgi Complex
1.
2.
Golgi bodies (Golgi complex) look a lot like the ER. However,
Golgi bodies are located close to the cell membrane.
The function of the Golgi complex is to package and send
proteins and other materials to different parts of the cell. The Golgi
complex also sends proteins and other materials outside the cell.
Cell Theory and Structure
Cell Structure: The Mitochondria
1.
2.
3.
Mitochondria are the cell’s energy makers.
Mitochondria take food molecules and turn them into ATP.
Cells use ATP for energy so that they can perform all their
necessary functions.
Cell Theory and Structure
Cell Structure: The Lysosomes
1.
2.
3.
4.
Lysosomes are the cell’s custodians and SWAT team/commandos.
Lysosomes destroy foreign invaders inside the cell by dissolving
them with enzymes.
Lysosomes also break down food particles and cell organelles
when they become dysfunctional.
Lysosomes clean up and recycle wastes in the cell.
Cell Theory and Structure
Cell Structure: The Vacuoles
1.
2.
3.
Vacuoles store liquids and excess materials in a cell.
Vacuoles in animal cells are very small compared to vacuoles in
plant cells.
Vacuoles in a plant contain large amounts of water and other
liquids which help give the plant support. Plants wilt when their
vacuoles lose water.
Animal Cell
Plant Cell
Cell Theory and Structure
Cell Structure: The Cell Membrane (All Cells)
1.
2.
The cell membrane acts a barrier and gatekeeper between the cell
and the world outside of the cell.
The cell membrane allows certain particles out of the cell and
specific particles into the cell.
Cell Theory and Structure
Cell Structure: The Cell Wall (Plants, Fungi and some
Protists)
1.
2.
The cell wall in plants is made of cellulose and provides support for
the cell, which in turn supports the plant. Millions or perhaps trillions
of these cells together give a tree its strength or celery its crunch.
The cell wall helps keep the cell membrane from breaking under
stress. This keeps the organelles inside the cell where they belong!
Cell Theory and Structure:
Reinforcement Activity
1.
2.
Choose a plant or animal cell and draw it on the front of your paper.
You must include the following organelles:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
3.
Cell membrane
Cell Wall (Plant Only)
Nucleus
Nucleolus
Endoplasmic Reticulum
Golgi Complex
Ribosomes
Lysosomes
Vacuoles
Mitochondria
Chloroplast (Plant cell only)
Cytoplasm
Draw a picture on the back or your paper to represent each of the
organelles in your drawing on the front. The picture must relate to the
function of the organelle not its physical characteristics. For example, you
might draw a flashlight to represent mitochondria, since mitochondria
provide the cell with energy.
From One Cell to an Organism
1. All living organisms are made of cells.
2. You consist of around 100 trillion cells.
3. However, all of your cells came from existing
cells…including the first cell that started your life.
4. You started off as a single cell inside your mother.
From One Cell to an Organism
1. Forty hours after fertilization your one cell has
divided into six to ten cells.
2. Your cells are still just stem cells at this point in
time. They do not have differentiated
functions…yet.
3. After six days, you are still just a mass of cells.
24 Hours
40 Hours
Six Days
From One Cell to an Organism
1. Your cells start to differentiate around two weeks
after fertilization.
2. By four weeks, 28 days you start to look like a little
like a human.
3. After four months, you look very much like a human.
Two Weeks
Four Weeks
Four Months
From One Cell to an Organism
1. After your cells differentiate, and start to perform
specific functions, they come together to form:
TISSUES
2. A tissue is a group of cells that work together to
perform a specific job in the body. Tissues include
red blood cells, fat, and muscle.
From One Cell to an Organism
1. Tissues of the same type come together to form
ORGANS
2. An organ is two or more tissues working together to
perform a specific job. Examples of organs include
your stomach, heart, skin and lungs.
From One Cell to an Organism
1. Organs that work together make up:
ORGAN SYSTEMS
2. An organ system is organs working together to
perform a particular job, such as digesting food or
breathing.
From One Cell to an Organism
1. Organ systems working together make up:
ORGANISMS
2. An organism is anything that can live on its own.
3. Unicellular organisms are made up of one cell.
4. Multi-cellular organisms are made up of many cells.