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Chapter 5
Lesson
What are cells?
Vocabulary Preview
 Cell: basic unit of structure and function of ALL living
things
 Tissue: a group of cells that work together to perform
certain functions
 Organ: a group of tissues that work together to perform a
certain function
 Organ System: a group of organs that work together to do
a job for the body
Cells as Building Blocks
 Cell: is the basic unit of structure and
function in living things
 Most cells are microscopic…..
 A scientist named Robert Hookes
observed a thin layer of cork through a
microscope.
 When he looked at the cork through a
microscope, it looked like tiny rooms so
he called them cells.
what does microscopic mean?
Cells as Building Blocks
 Hooke’s description of
cells made scientists
want to know more
about them.
 Using microscopes, they
learned that all living
things are made of cells.
 They found cells share
some characteristics.
 Also different kinds of
cells do different things.
Cells as Building Blocks
 Every living thing, or
organism is made up of
cells.
 Some simple organisms
are just a single cell.
 Most plants and animals
contain many cells.
 Plants and Animals have
different types of cells,
each with its own job.
Cells are Building Blocks
 The different cells work together to carry
out life functions that keep an organism
alive and healthy.
 Ex: Your body has cells that: break down
food, carry oxygen, and carry away
waste
 To perform these functions, each cell
contains structures called organelles.
 Each organelle has a certain job that
helps keep the cell alive.
The outer cells of
this plant’s leaf help
keep the plant from
losing too much
water. The leaf’s
inner cells make
food for the plant.
The single cell that makes
up this amoeba
[uh•MEE•buh] carries out
all the functions that the
organism needs to stay
alive.
A salamander’s
skin cells don’t
look like a plant’s
cells, but they also
help keep the
organism from
drying out.
Cell Structures and
Functions
 All plant and animal cells have certain organelles in
common.
 Ex: every cell has a thin covering called the cell
membrane
 The cell membrane protects the cell, holds it together,
and controls what goes in or out of the cell.
Plant and Animal Cells
 Plant and Animal cells both have a nucleus.
 This organelle directs all of a cell’s activities.
 Inside the nucleus are threadlike chromosomes
that have information about the cell’s activities.
 When a cell reproduces itself by dividing, the
nucleus first makes a copy of each
chromosome.
 The new cell gets the copies.
Plant and Animal Cells
 Between the cell membrane and the nucleus is
the cytoplasm.
 Cytoplasm: a jelly-like material that contains
chemicals that keep a cell healthy.
 Several organisms float in the cytoplasm.
 Mitochondria are the “powerhouses” of plant
and animal cells.
 Mitochondria release energy from nutrients.
 Vacuoles store nutrients, water, or waste
materials in plant cells.
 Vesicles has similar functions in animal cells.
Plant and Animal Cells
 Plant cells have some structures that are
not found in animal cells.
 A thick cell wall helps support a plant cell.
 The cell wall lies outside the cell
membrane.
 In the cytoplasm of many plant cells,
there are chloroplasts.
 Chloroplasts make food for plant cells.
Cells, Tissues, Organs,
Systems
 Multi-cellular of many celled organisms
like you are made up of trillions of cells.
 Each cell is able to carry out its own life
functions.
 The cells in multi-cellular organisms work
together.
 Cells that work together to perform a
specific function form a tissue.
Single-Celled Organisms
 Single-Celled Organisms
function differently.
 They don’t have organs
or tissues.
 The one cell that a
single-celled organism
has must eat, move, and
do all other functions
necessary for survival.