Cell Structure and Function
Discovering Cells
Overview
•
•
Cells are basic units of structure and
function in living things.
This means that cells form the parts or
an organism and carry out all of the an
organism’s processes, or functions.
Cells and Structure
•
•
The structures of living things are
determined by the variety of ways in
which cells are put together.
Examples:
• A tall tree consists of cells arranged to form a
high trunk and leafy branch.
• A red newt’s cells form a body with a head
and four legs.
Cells and Functions
An organisms functions are processes
that enable it to stay alive and
reproduce.
 Examples:

 Obtaining oxygen
 Getting rid of waste
 Growing
 Obtaining food
Many and Small

One square centimeter of your skin’s
surface contains approx. 100,000 cells.
First Observations of Cells


The invention of the
microscope made it
possible for people
to discover and lean
about cells.
A microscope is an
instrument that
makes small objects
look smaller.
Robert Hooke

One of the first people to observe cells
was the English scientist and inventor
Robert Hooke.

Hooke used his microscope to observe
a thin slice of cork.
 Cork is made from trees

To Hooke the empty spaces looked like
empty rooms, which is where we get the
word cell –meaning “small rooms”
Hooke and Cork Cells
Anton van Leeuwenhoek
Leeuwenhoek was a Dutch
businessman who sold cloth. In his
spare time he build simple microscopes.
 Leeuwenhoek looked at samples from
lake water, scrapings from teeth, and
rain water.
 When looking at the samples he say
cells and some of these cells moved.\
 He called these moving organisms
animalcules meaning “little animals”

Leeuwenhoek and cells
The Cell Theory


Three scientists
helped develop the
cell theory.
The cell theory is a
widely accepted
explanation of the
relationship between
cells and living cells.
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.
The Cell Theory

The cell theory
applies to every
living thing no matter
how big or small.

https://www.brainpo
p.com/health/bodysy
stems/cells/
Unicellular Organisms
vs.
Multicellular Organisms
What makes a living thing
different from a nonliving thing?
A living things uses energy!
 Any individual form of life that uses
energy to carry out its activities is an
organism.
 Most organisms move.
 All organisms get water and other
materials from the environment.

Characteristics of Living Things

Living things have these characteristics:
 organization
 the ability to develop and grow
 the ability to respond to the environment
 the ability to reproduce
Needs of Life

Organisms cannot carry out the
activities that characterize life without a
few necessities:
 Energy
 Materials
 Living space.
What is an Organism?
Definition:
Organism – anything that can live on its own
Unicellular
Organisms
Unicellular Organisms
Definition:
Unicellular organism – an organism made of
only one cell
Information:
These organism are very small and need to be
seen with a microscope.
Unicellular:
Common Names

Microscopic Organisms

Microorganisms

Really small living things
Examples of
Unicellular Organisms

Amoeba

Unicellular fungi

Bacteria

Unicellular yeasts

Protozoa

Paramecium

Unicellular algae
Images of Unicellular Organisms
Multicellular
Organisms
Multicellular Organisms
Definition:
Multicellular organism – an organism made of
two or more cells
Information:
 These organisms are able to be seen with the
naked eye.
 These organisms need all parts of itself to
survive.
Common Names
Many – celled organisms
 Eukaryotic organisms
 Mammals
 Birds
 Reptile
 Fish
 Many others…

Examples of Multicellular
Organisms

Humans

Birds

Cats

Flowers

Dogs

Mold

Insects

Trees
Images of Multicellular Organisms
Section Two
Looking Inside Cell

Cells are basic units of structure and function
in living things.

There are even small structures inside a cell.
These tiny structures are called organelles.

Organelles carry out specific functions within
the cell.

https://www.brainpop.com/science/cellularlifea
ndgenetics/cellstructures/
Looking Inside the Cell

Each organelle has a different function
inside the cell.
Cell Wall

Description:
 The cell wall is a rigid layer of nonliving
materials that surrounds the cells of plants
and some other organisms.

Job:
 A plant’s cell wall helps to protect and
support the cell.

Type of Cell:
 Plant Only
Cell Wall
Animal cell
Plant cell
Cell Wall

Additional Information:
 The cell wall is made mostly of a strong
material called cellulose.
 The cell wall is tough and strong but
○ Water can pass through
○ Oxygen can pass through
Cell Membrane

Description:
 In cells with cell walls, the cell membrane is
located just inside the cell wall. In other
cells, the cell membrane forms the outside
boundary that separates the cell from its
environment.

Job:
 The cell membrane controls what
substances come into and go out of the cell.
Cell Membrane

Type of Cell:
 Plant and Animal Cells

Additional Information:
 Everything that the cell needs from food to
oxygen pass through the cell membrane.
 The cell membrane prevents harmful
materials from entering the cell
Cell Membrane
Nucleus

Description:
 A large oval structure in the center of the cell.

Job:
 The “brain of the cell”. Controls the activities of
the cell

Types of Cell:
 Animal and Plant Cell

Additional Information:
 There are several parts that make up the
nucleus
Nucleus
Nuclear Envelope

Description:
 A membrane that surrounds the nucleus.
Covered in pores

Job:
 Protects the nucleus and allows materials to
pass in and out through the pores

Types of Cells:
 Plant and animal cells
Chromatin

Description:
 Thin strand floating in the nucleus

Job:
 Contain genetic material that are the
instructions for directing the cell’s functions

Type of Cell:
 Plant and animal cells
Nucleolus

Description:
 A small circular structure that is located in
the nucleus

Job:
 Produces the ribosomes of the cell

Type of Cell:
 Plant and animal cell
All Parts of the Nucleus
Cytoplasm

Description:
 The region between the cell membrane and
the nucleus. Made of a clear gel-like fluid.

Job:
 Cytoplasm is responsible for giving a cell its
shape, keeps organelles in their place.

Types of Cells:
 Plant and animal cells
Cytoplasm
Mitochondria

Description:
 Rod shaped structure

Job:
 Known as the “powerhouse” of the cell
because they convert energy into food
molecules to energy the cell can use to carry
out its functions

Types of Cells:
 Plant and Animals
Mitochondria
Endoplasmic Reticulum

Description:
 A maze of passageways that surround the
nucleus

Job:
 Carries proteins and other materials from
one part of the cell to another

Types of Cells:
 Plants and Animal Cell
Endoplasmic Reticulum
Ribosomes

Description:
 Small, grain-like bodies that attach to the
Endoplasmic Reticulum

Job:
 Produce proteins

Types of Cells:
 Animal and Plant cells
Golgi Bodies

Description:
 Flattened sacs and tubes

Job:
 Receive proteins and other newly formed
materials from the endoplasmic reticulum,
package them, and distribute them to the
other parts of cells

Types of Cells:
 Plant and Animal Cells
Golgi Bodies
Chloroplasts

Description:
 Large green structures that float in the
cytoplasm. It is what makes the leaves
green.

Job:
 Capture the energy from sunlight and use it
to produce food for the cell.

Types of Cells
 Animal cells
Chloroplasts
Vacuoles

Description:
 Large water filled sac floating in the
cytoplasm. Plants have one large one.
Some animal cells have several some ones

Job:
 The storage areas of the cells. Stores food,
water, and waste.

Types of Cells
 Animal and plants cells
Vacuoles
Lysosomes

Description:
 Small, round structures that contain
chemicals

Job:
 Break down materials in the cell.
○ Food
○ Old parts of the cell

Types of Cells
 Animal and Plant cells
Lysosomes
Section Four
The Cell in its Environment
All cells are surrounded by a cell
membrane that separates the cell from
the outside environment.
 The cell membrane is selectively
permeable, which means that some
substances can pass through the
membrane while others cannot.

The Cell in its Environment
Cells must let things enter and leave.
 Oxygen, food molecules, and waste
products all must pass through the cell
membrane.

The Cell in its Environment

Substances that can move into and out
of a cell do so by one of three methods:
 Diffusion
 Osmosis
 Active transport
Diffusion

Diffusion is the main method by which
small molecules move across the cell
membrane.
Diffusion is the process by which
molecules move from an area of higher
concentration to an area of lower
concentration.
 https://www.brainpop.com/science/cellul
arlifeandgenetics/passivetransport/

What Causes Diffusion?

Molecules are always moving and
bumping into one another.

The more molecules there are in an
area, the more collisions there will be.

Eventually they will spread evenly
throughout the area.
Diffusion
Osmosis

Osmosis is the diffusion of water
molecules through a selectively
permeable membrane

Cells cannot function properly without
adequate water, many cellular
processes depend on osmosis
Osmosis and Diffusion

In osmosis, water molecules move by
diffusion from an area where they are
highly concentrated through the cell
membrane to an area where they are
less concentrated.

Osmosis is simply diffusion for water
Effects of Osmosis

There are three effects of osmosis:
 Hypertonic
 Isotonic
 Hypotonic
Hypertonic

Hypertonic osmosis:
 Low water
concentration outside
of the cell
 Water moves out of
the cell during
osmosis
Isotonic

Isotonic osmosis:
 Normal Cell
 Concentration of water inside the cell is the
same as outside.
Hypotonic

Hypotonic Osmosis:
 High water
concentration outside
the cell.
 During osmosis,
water moves into the
cell.
Passive Transport
For a cell moving materials through the
cell membrane by diffusion and osmosis
require no energy.
 The movement of dissolved material
through a cell membrane without using
cellular energy is called passive
transport

Active Transport

What if a cell has to take in a substance
that is present in a higher concentration
inside the cell than outside?

The cell would have to move the
molecules in the opposite direction than
they naturally move by diffusion.
Active Transport

Active transport is the movement of
materials through a cell membrane
using cellular energy.
Active transport uses the cell’s
energy while passive transport does
not.
 https://www.brainpop.com/science/ce
llularlifeandgenetics/activetransport/

Active Transport vs. Passive
Transport
Types of Active Transport

Transport proteins:
 Transport proteins in the cell membrane
“pick up” molecules outside the cell and
carry them inside the cell
○ Calcium
○ Potassium
○ Sodium
Types of Active Transport

Transport by engulfing:
 The cell membrane surrounds and engulfs,
or encloses, a particle.
 Once the particle is engulfed, the cell
membrane wraps around the particle and
forms a vacuole within the cell.
Specialized Cells

Plants and animals contain many cells.

In a many-celled organism, the cells are
often quite different from one another
and are specialized to preform specific
functions.
Specialized Cells
Red Blood Cells
Nerve Cells
The levels of organization from
simplest to most complex are:
Cells
 Tissues
 Organs
 System
 Organism

Levels of Organization
Cells
 The
basic unit of structure and
function in the human body
 Though all cells perform the
processes that keep humans alive,
they also have specialized functions
as well.
 Examples may be nerve cells
(neurons), blood cells, and bone cells.
Tissues


A group of specialized cells
that work together to perform
the same function.
There are four basic types of
tissue in the human body:
Tissues
1. Nerve tissue – carries
impulses back and forth to
the brain from the body
Three types of muscle tissue
Muscle tissue – (cardiac, smooth, skeletal)
contract and shorten, making body parts move
 Skeletal


Cardiac

Smooth
3. Epithelial tissue – covers the surfaces of the
body, inside (as lining and /or covering of
internal organs) and outside (as layer of skin)
4. Connective tissue – connects all parts of the
body and provides support (for example
tendons, ligaments, cartilage).
Organs
 A group
of two or more different types
of tissue that work together to perform
a specific function.
 The task is generally more complex
than that of the tissue.
 For example, the heart is made of
muscle and connective tissues which
functions to pump blood throughout
the body.
Systems
A group of two or more organs that work
together to perform a specific function.
 Each organ system has its own function but the
systems work together and depend on one
another.
 There are eleven different organ systems in the
human body: circulatory, digestive, endocrine,
excretory (urinary), immune, integumentary,
muscular, nervous, reproductive, respiratory,
and skeletal.

The Digestive System
Purpose: to convert food particles into simpler
micromolecules that can be absorbed into the bloodstream and used by the body
Major Organs and their Functions:
Mouth – to chew and grind up food
-- saliva also begins the chemical breakdown
Esophagus – pipe connecting mouth to stomach
Stomach – secretes an extraordinarily strong acid (pH = 2) that leads to breakdown
of food
Pancreas – produces the hormone insulin that regulates blood
levels
sugar
-- also help neutralize stomach acid
Liver – produces bile, which breaks down fats in foods
Gallbladder – pouch-like organ that stores bile for future use
Small Intestine – after digestion is complete, the chyme enters the small intestine
where it is absorbed into the bloodstream
-- the chyme is propelled along by folded surfaces
called villi, on the
intestine
Large Intestine – removes water from the chyme and gets the waste ready for
excretion
The Digestive System
The Excretory System
Purpose: to rid the body of wastes, including excess water and salts
Major Organs and Their Functions
Kidneys – the main organs of the excretory system
-- waste-laden blood enters the kidney and the kidney filters out urea,
excess water and other waste products, which eventually travel out of the kidney as
urine
-- eventually they travel through the ureter to the urinary bladder
Rectum – solid (food) waste travels out of the body through the rectum
Skin – sweat glands remove excess water and salts from the
Lungs – expel the waste gas carbon dioxide
body
The Excretory System
The Respiratory System
Purpose: to provide the body with a fresh supply of oxygen for cellular respiration
and remove the waste product carbon dioxide
Major Organs and Their Functions
Nose – internal entry and exit point for air
Pharynx – serves as a passage way for both air and food at the back of the
throat
Larynx – your “voicebox”, as air passes over your vocal
chords, you speak
Trachea – the “windpipe”, or what connects your pharynx to your lungs
Bronchi – the two large passageways that lead from the trachea to your lungs
(one for each lung)
The diaphragm is the muscle that causes you to breath
Image of the Respiratory System
The Circulatory System
Purpose: to deliver oxygenated blood to the various cells and organ systems in
your body so they can undergo cellular respiration
Major Organs and Their Functions
Heart – the major muscle of the circulatory system
-- pumps blood through its four chambers (two ventricles and two atria)
-- pumps deoxygenated blood into the lungs, where it gets oxygenated,
returned to the heart, and then pumped out through the aorta to the rest of the
body
-- valve regulate the flow of blood between the chambers
Arteries – carry blood away from the heart and to the major organs of the body
Veins – carry blood back to the heart away from the major organs of the body
Capillaries – small blood vessels where gas exchange occurs
Blood – the cells that flow through the circulatory system
Spleen – helps to filter out toxins in the blood
Image of the Circulatory System
The Nervous System
Purpose: to coordinate the body’s response to changes in its internal and external
environment
Major Organs and Their Functions
Brain – control center of the body, where all processes are relayed through
Spinal Cord – sends instructions from the brain to the rest of the body
and vice versa
Nerves – conduct impulses to muscle cells throughout the body
Diagram of a Nerve Cell
The Muscular System
Purpose: works with the skeletal and nervous system to produce movement, also
helps to circulate blood through the human body
-- muscle cells are fibrous
-- muscle contractions can be voluntary or involuntary
Major Muscles in the Human Body
-- biceps
-- glutes
-- triceps
-- hamstrings
-- deltoids
The Muscular System