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Chapter 3 Cell Structure and Function
Section 1: Discovering Cells
What are cells?
How did the invention of the microscope contribute to
knowledge about living things?
What is the cell theory?
How are the cells of multicellular organisms
organized?
Chapter 3 Cell Structure and Function
What Are Cells?
All living things are made up of cells.
Cells have many similarities between
different species.
• Example: Mitochondria can be found in the
cells of humans, dogs, spiders, trees, etc.
Cells are the basic unit of structure and
function in all living things.
Chapter 3 Cell Structure and Function
Cell Structure
Cells form parts of your organs.
It gives your body its’ shape, size, strength.
Chapter 3 Cell Structure and Function
Cell Function
Cells perform all of an organism’s tasks
and functions.
» obtain oxygen and food
» get rid of wastes
» allow you to grow and repair.
Chapter 3 Cell Structure and Function
Cell Size
Most cells are so small they
are microscopic.
• Microscopic: can only be seen by
the human eye with the help of a
microscope.
• Approximately 100,000 skin cells fit
in a square centimeter.
• Approximately 250 million red blood
cells are found in a drop of blood.
Chapter 3 Cell Structure and Function
Development of the Cell Theory
The cell theory states the following:
• All living things are composed of cells.
• Cells are the basic units of structure and function in living things.
• All cells are produced from other cells.
Chapter 3 Cell Structure and Function
Unicellular vs. Multicellular
Unicellular, or singlecelled, organisms
include bacteria, the
most numerous
organisms on Earth.
Unicellular
Multicellular
organisms, like this
dog, are composed of
many cells.
Multicellular
Chapter 3 Cell Structure and Function
Advantages of Being Multicellular
In multicellular
organisms, cells are
often organized into
tissues, organs, and
organ systems.
This allows our cells
to perform specialized
and unique tasks.
Chapter 3 Cell Structure and Function
End of Section:
Discovering Cells
Chapter 3 Cell Structure and Function
Section 2: Looking Inside Cells
What role do the cell wall and cell membrane
play in the cell?
What is the role of the nucleus in the cell?
What organelles are found in the cytoplasm
and what are their functions?
How do cells differ?
Chapter 3 Cell Structure and Function
Organelles (and other Cell Structures)
Organelle: a tiny structure that has a specific function inside the cell,
floating in the cytoplasm
Found in Both
Plant and Animal Cells
Found Only in
Plant Cells
Found Only in
Animal Cells
nucleus
cell wall
lysosomes
cell membrane
chloroplasts
vacuoles
(several small)
cytoplasm
vacuole (one large)
endoplasmic reticulum
ribosomes
Golgi body
mitochondria
Chapter 3 Cell Structure and Function
Plant and Animal Cells
Chapter 3 Cell Structure and Function
Cell Membrane
What is it?
The “skin” of the cell, helping
form a boundary that separates
the inside of the cell from the
outside.
Why does the cell need it?
To control what substances are
allowed to enter or leave the
cell.
Where can it be found?
In both plant and animal cells.
Chapter 3 Cell Structure and Function
Cell Wall
What is it?
A rigid layer of cellulose that
surrounds the cell membrane.
Although it is very strong, it still
allows materials like water and
oxygen to pass through.
Why does the cell need it?
It helps to protect and support
the cell.
Where can it be found?
In plant cells only.
Chapter 3 Cell Structure and Function
Nucleus
What is it?
The “control center” of the cell.
It contains thin strands of DNA
called chromatin that direct all
of the cell’s activities.
Why does the cell need it?
The cell would not know how to
function without the nucleus.
Where can it be found?
In both plant and animal cells.
Chapter 3 Cell Structure and Function
Cytoplasm
What is it?
The area between the cell
membrane and the nucleus.
Contains a gel-like fluid that is
constantly moving inside the cell.
Why does the cell need it?
Allows organelles to move around
the inside of the cell. Also, the
fluid helps regulate the cell’s
temperature and pH level.
Where can it be found?
In plant and animal cells.
Chapter 3 Cell Structure and Function
Mitochondria
What is it?
The “powerhouses” of the cell
because they convert food
molecules to energy the cell
can use to carry out its
functions (also called “cellular
respiration”).
Why does the cell need it?
Without it, cells wouldn’t have
the energy to function.
Where can it be found?
In both plant and animal cells.
Chapter 3 Cell Structure and Function
Endoplasmic Reticulum (E.R.)
What is it?
Moves materials throughout the
cell. When covered with ribosomes,
it is called “Rough E.R.”. Without
ribosomes, it is called “Smooth E.R.”.
Why does the cell need it?
Ribosomes help make proteins,
hormones, and other materials.
The E.R. helps move these
materials to specific places
after they have been made.
Where can it be found?
In plant and animal cells.
Chapter 3 Cell Structure and Function
Ribosomes
What is it?
Tiny “protein factories” that are
found floating in the cytoplasm
or attached to the E.R.
Middle School Version
Why does the cell need it?
Ribosomes read the message
encoded in the cell’s DNA and
translate these codes into
proteins, hormones, and other
structures. Without ribosomes,
the DNA would be useless.
Where can it be found?
In both plant and animal cells.
Medical School
Version
Chapter 3 Cell Structure and Function
Golgi bodies
What is it?
The “post office” of the cell.
The Golgi bodies receive
proteins and other newly
formed materials from the E.R.,
package them, and distribute
them to other parts of the cell.
Why does the cell need it?
Without it, many proteins
would be incomplete or lost.
Where can it be found?
In both plant and animal cells.
Chapter 3 Cell Structure and Function
Chloroplast
What is it?
Green organelles that capture
sunlight and convert it into sugar,
which is used as a food source.
Why does the cell need it?
Without it, plants would not have a
food source. Also, animals depend
on plants for food, either because
they eat plants, or they eat other
animals (which eat plants).
Where can it be found?
In plant cells only.
Chapter 3 Cell Structure and Function
Vacuole
What is it?
Storage area of the cell. Mostly
stores water, but sometimes
stores food and waste.
Why does the cell need it?
Allows the cell to store materials.
In plants, the vacuole gives the
cell internal pressure (like air
inflating a balloon).
Where can it be found?
In animal cells, there are several
tiny vacuoles. In plant cells, there
is only 1 large vacuole (called
“the central vacuole”).
Plant Cell
Animal Cell
Chapter 3 Cell Structure and Function
Lysosomes
What is it?
The “clean-up crew” of the cell.
Contains chemicals called
enzymes that break down large
food particles, trash, and even
old organelles.
Why does the cell need it?
Without it, the cell would
become cluttered with food
particles that are too big for the
mitochondria, toxic trash, and
dead organelles.
Where can it be found?
In animal cells only.
Chapter 3 Cell Structure and Function
End of Section:
Looking Inside Cells
Chapter 3 Cell Structure and Function
Section 3: Chemical
Compounds in Cells
What are elements and compounds?
How is water important to the function of cells?
What are the functions of carbohydrates,
lipids, proteins, and nucleic acids?
Chapter 3 Cell Structure and Function
Elements
An element is any
substance that
cannot be broken
down into simpler
substances.
Examples include
carbon (C), nitrogen
(N), hydrogen (H),
and oxygen (O).
Chapter 3 Cell Structure and Function
Compounds
Carbon dioxide, which is found in gas bubbles, is a chemical
compound made up of 1 carbon and 2 oxygen atoms. So is
water (2 hydrogen and 1 oxygen).
Chapter 3 Cell Structure and Function
Organic and Inorganic Molecules
Inorganic Molecules: do not contain carbon (C);
water (H20) and “breathable” oxygen (O2) are
important inorganic molecules needed by living
organisms.
Organic Molecules: contain carbon; includes
carbohydrates, lipids, proteins, and nucleic
acids.
Chapter 3 Cell Structure and Function
Carbohydrates
Provides quick energy
for the cell.
Plants make “carbs” in
the form of sugars and
starches.
The cellulose in a plant
cell wall is a type of
“carb”.
Chapter 3 Cell Structure and Function
Lipids
Provides slow-burning
energy for the cell.
Cells can store lipids to
save energy for future
use.
Makes up most of the
cell membrane.
Found in fats, oils, and
waxes.
Chapter 3 Cell Structure and Function
Proteins
Provides structures (like
muscles) and chemicals (like
hormones and enzymes) for
your body.
Found in meat, eggs, fish,
nuts, and beans.
Proteins are actually made up
of tiny molecules called
amino acids.
Chapter 3 Cell Structure and Function
Nucleic Acids
Contains the instructions
that cells need to do their
job and stay “alive”.
2 types of nucleic acids:
• DNA (instructions that can
be passed on from parent to
child)
• RNA (help make proteins).
Chapter 3 Cell Structure and Function
End of Section:
Chemical
Compounds in Cells
Chapter 3 Cell Structure and Function
Section 4: The Cell in Its
Environment
How do most small molecules cross the cell
membrane?
Why is osmosis important to cells?
What is the difference between passive and
active transport?
Chapter 3 Cell Structure and Function
A Selective Barrier
The cell membrane protects the contents of the cell and
helps control the materials that enter and leave.
Chapter 3 Cell Structure and Function
Diffusion
In diffusion, molecules move from an area of HIGHER
concentration to an area of LOWER concentration.
Chapter 3 Cell Structure and Function
Osmosis
In osmosis, water diffuses through the cell membrane using
the power of diffusion.
Chapter 3 Cell Structure and Function
Osmosis
The picture in the middle shows blood with equal amounts of
salt inside and outside the cell. As a result, water moves
evenly inside and outside.
Chapter 3 Cell Structure and Function
Osmosis
The picture on the left shows blood surrounded by excessive
salt. Water is attracted to this, so it leaves the cell and the
cell shrivels like a raisin.
Chapter 3 Cell Structure and Function
Osmosis
The picture on the right shows a cell that is filled with salt.
Water is attracted to this, so the cell swells up with water.
Chapter 3 Cell Structure and Function
Passive and
Active Transport
Passive and active
transport are two methods
that allow materials (like
food and waste) to pass
through the cell
membrane.
Active transport requires
the cell to use its own
energy, while passive
transport does not.
Chapter 3 Cell Structure and Function
End of Section: The
Cell in Its Environment