Characteristics of Cells 2024

Characteristics of
Cells

UNIT 3: Cells

In this lesson…

You will be able to explain
the components of the
scientific theory of cells.

Characteristics of Cells

A cell is the smallest
functional and structural
unit of all living organisms.
An organism is any living
thing.

Multiple Choice

What is a cell?

• A cell is the smallest unit of matter.

• A cell is the largest structure in an organism.

• A cell is the basic unit of structure and function in all living things.

• A cell is a structure that can only be found in plants.

Characteristics of Cells

All organisms are made up
of cells and some are
made up of just one cell.
Humans are made up of
trillions of cells.

Multiple Choice

How many cells are in the human body?

• About one million cells

• About one billion cells

• About one hundred billion cells

• About one trillion cells

Characteristics of Cells

An organism carries out all
of its own life processes.

Characteristics of Cells

Robert Hooke was the first
person to describe cells in 1665
after building a microscope and
looking at cork tree bark.

Characteristics of Cells

Most cells are too small to
be seen without a
microscope. Cells are small
because their size is limited
by their outer surface area.

Characteristics of Cells

The ratio of the cell’s outer
surface area to the cell’s
volume is called the
surface area-to-volume
ratio.

Characteristics of Cells

Smaller cells have greater
surface area-to-volume
ratio than larger cells.

Multiple Choice

Why are cells so small?

• Smaller cells can move more easily within an organism.

• Cells need to be small so they can reproduce quickly.

• Smaller cells have a larger surface area relative to their volume, allowing for efficient exchange of materials.

• Cells are small to fit inside an organism’s tissues.

Characteristics of Cells

Cell theory lists three
basic characteristics of all
cells.

Characteristics of Cells

Cell theory states that:
1. all organisms are made up of one
or more cells.
2. the cell is the basic unit of all
organisms.
3. all cells come from existing cells.

Multiple Choice

According to the cell theory, where do new cells come from?

• New cells form from non-living matter.

• New cells come from pre-existing cells.

• New cells are spontaneously created by the organism.

• New cells are formed by a chemical reaction within the body.

Characteristics of Cells

Unicellular organisms are
those that are made up of
just one cell.

Characteristics of Cells

Organisms that are made
up of more than one cell
are called multicellular
organisms.

Characteristics of Cells

All cells have some parts
in common. Those include
cell membrane, cytoplasm,
organelles, and DNA.

Characteristics of Cells

A cell membrane is a protective
layer that covers a cell’s surface
and acts as a barrier between the
inside of a cell and the cell’s
environment. It also controls
what moves in and out of the cell.

Multiple Choice

What is the main function of the cell membrane?  

• To produce energy for the cell.

• To control what enters and leaves the cell.

• To store genetic information.

• To support the cell by providing a rigid structure.

Characteristics of Cells

The cytoplasm is the region
enclosed by the cell membrane
that includes the fluid and all of
the organelles of the cell.

Multiple Choice

What is the role of the cytoplasm in a cell?  

• It controls what enters and leaves the cell.

• It produces proteins for the cell.

• It fills the cell and holds the organelles in place.

• It stores the cell’s genetic information.

Characteristics of Cells

Organelles are the small bodies
in a cell’s cytoplasm that are
specialized to perform a specific
function. Cells can have one or
more types of organelles. Most
organelles have a membrane.

Multiple Choice

What is an organelle?  

• A structure within a cell that performs a specific function.

• The outermost layer of a cell that provides protection.

• A type of cell that contains a nucleus.

• The fluid that fills the inside of a cell.

Characteristics of Cells

DNA is deoxyribonucleic acid and
is the genetic material that
provides instructions for all cell
processes. Organisms inherit
DNA from their parent or parents.

Characteristics of Cells

In some cells, the DNA is
contained in a membrane-bound
organelle called the nucleus,
although some cells do not have
a nucleus.

Multiple Choice

What is the main function of the nucleus in a cell?

• It controls the movement of materials in and out of the cell.

• It produces energy for the cell.

• It stores the cell’s genetic information and controls cell activities.

• It helps the cell maintain its shape.

Characteristics of Cells

A prokaryote is a single-celled
organism that does not have a
nucleus or membrane-bound
organelles.

Characteristics of Cells

The DNA of prokaryotes is
located in the cytoplasm, as well
as its ribosomes, which do not
have a membrane. Some
prokaryotic cells have hairlike
structures called flagella.

Multiple Choice

Which of the following is a characteristic of prokaryotic cells?

• They have a nucleus that stores their DNA.

• They contain membrane-bound organelles like mitochondria.

• They do not have a nucleus, and their DNA is free-floating in the cytoplasm.

• They are always larger than eukaryotic cells.

Characteristics of Cells

All bacteria and archaea are
prokaryotes, which are smaller
than eukaryotes.

Characteristics of Cells

Eukaryotes are organisms that
are made up of cells that contain
their DNA in a nucleus.
Eukaryotes contain
membrane-bound organelles and
ribosomes.

Characteristics of Cells

Animals, plants, protists, and
fungi are eukaryotes. Most
eukaryotes are multicellular,
although some, such as amoebas
and yeasts, are unicellular.

Multiple Choice

According to cell theory, what is the basic unit of all life?

• the atom

• the heart

• the cell

• the sun