Cell Structure and
Functions
Discovering Cells
• What do all the things in this picture have in common?
• They are all organisms or living things
• All living things are made of cells
• Cells are the building blocks of life
• They are the smallest things that have all the
characteristics of life
• The diversity of living things are determined by the
amazing variety of ways in which cells are put together
• Cells carry out the basic processes of life
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Respiration (obtaining oxygen or carbon dioxide)
Eliminating waste
Obtaining food
Reproducing, and
Growing or developing
•
Cells make these functions happen
– For example, cells in your digestive system absorb food
– The food provides an organism energy and materials
needed for growth/development
•
Cells function similarly in all organisms
regardless of the organism they are
part of
• Prior to the early 1800s, people believed in Spontaneous
Generation— Life can come from nonliving things
• Rats came from garbage
– Frogs came from mud
– Flies grew out of rotten meat
Flies smell meat
and lay eggs on
screen which drop
through then hatch
Francesco Redi’s Experiment
Flies cannot
get to rotten
meat and no
flies hatch
Flies lay
eggs directly
on rotten
meat then
hatch
• In 1838, German botonist, Matthias Schleiden, concluded
that all plants are made of cells
• German physiologist,Theodor Schwann, concluded that all
animals are also made up of cells
• Schwann stated that all living things are made up of cells
The Cell Theory
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All Living things are composed of cells
Cells are the basic unit of all living things
All cells come from other cells
The cell theory is true for all living things
Since cells are common to all living things, they
provide information about the functions that living
things perform
Cell Organelles
Organelles
Cell Membrane
Controls
what
and out of cell
• There are even smaller structures
inside
of goes
cellsin called
organelles
Cytoplasm
Environment for cell structures
•
Just as your stomach, lungs, and
heart have different
Nucleus
functions in your body, each organelle has a different
Cell reproduction
function within the cell
Vacuole
Storage of water and food
Mitochondria
Conversion of food to energy
Chloroplasts
Production of food in plants
Cell Wall
Strength and structure for plants
Cell Wall
• The cell wall is a rigid
layer of nonliving material
surrounds the cells of
plants
that
• A cell wall helps to protect and support the cell
• The cell wall is made mostly of a strong material called
cellulose
• Although the cell wall is tough, many materials, including water
and oxygen can pass through
easily
• Animal cells and many
single celled organisms do not
have cell walls
Cell membrane
• All cells have a cell membrane
• In plant cells, it is inside of the
cell wall
• The cell membrane is the outside
boundary of animal cells
• This membrane controls what goes into the cell and what
goes out
C
Cell Wall
Cell Membrane
The Nucleus
• The nucleus is the control center,
directing all of the cell’s activities
• The nucleus surrounded by a
membrane called the nuclear
envelope
• Materials pass in and out of the
nucleus through pores in the
nuclear envelope
• Nucleus is where cell reproduction takes place
– Chromatin in the
nucleus contains
genetic material
which insructs the
cell to divide to form
new cells
The Nucleolus
• The nucleolus is where ribosomes are made
• Ribosomes are the organelles where proteins are
produced
The Cytoplasm
• The cytoplasm is a clear thick fluid between the cell
membrane and the nucleus
• In the cytoplasm
are many
organelles
that perform
specific
functions in the
cell
Mitochondria and Endoplasmic Reticulum
• Mitochondria are known as the “powerhouses” of the cell
because they convert energy in food to energy the cell can
use to carry out its functions
• The endoplasmic
reticulum are
passageways
that help form
proteins and
other materials
• They also carry
material throughout the cell
Ribosomes
• Attached to some of the endoplasmic reticulum are small,
bodies called ribosomes
• Ribosomes function as factories to produce proteins from the
endoplasmic
reticulum, the
proteins are
transported to the
Golgi bodies
Golgi Bodies
• Golgi bodies receive proteins and other newly formed
materials from the endoplasmic reticulum
• They then distribute materials to other
parts of the cell
• Golgi bodies also
release materials
outside the cell
Chloroplasts
• Only plant cells have organelles called chloroplasts
• Chloroplasts contain a chemical called chlorophyll
• Chlorophyll captures energy from sunlight and uses it to
produce food for the plant
• Chlorophyll
makes leaves
look green
Vacuoles
• Vacuoles are large sacs that float in the cytoplasm
• Vacuoles are the storage areas of the cells
• Most plant cells have one large, water-filled, central
vacuole
• Vacuoles can also store waste products
• Animal cells have smaller vacuoles
vacuoles
Lysosomes
• Lysosomes are structures that surround food particles
entering the cell and digest them with chemicals
• Lysosomes also
break down old
cell parts and
release the
substances so
they can be
used again
• Every cell and everything in the cell is made up of
elements and compounds
• Elements are individual atoms of the same type
• Compounds are made of elements chemically bonded in
specific arrangements
Oxygen
Hydrogen
Atoms (Elements)
Compound
• Cells function similarly in all organisms because—
– All organisms’ cells are made out of identical chemical
compounds
– All organisms’
cells use
identical
chemical
compounds
– All organisms’
cells produce
many identical
chemical
compounds
Inorganic and Organic Compounds
• Water is an example of an inorganic
compound
• An inorganic compound does not
contain the element carbon
• Most compounds that contain carbon are called organic
compounds
• Most living things contain carbon
• Important inorganic compounds—
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Carbohydrates,
lipids,
proteins, and
nucleic acids
Water
• Water is a compound
• Each water molecule is made up of two
hydrogen atoms and one oxygen atom
• Water makes up about two thirds of
body
• Water plays many important roles in cells
your
• Water dissolves chemicals that cells need
• Most chemical reactions within cells need water For
Example—
– Plants need water to convert the energy into food
– Water helps plant cells keep their size
– It helps keep the temperature of cells from changing too rapidly
Carbohydrates
• A carbohydrate is an energy-rich organic compound made of
elements carbon, hydrogen, and oxygen
• Sugars and starches are examples of carbohydrates
• Sugars are produced when plants make their own food
• Plant cells store excess energy in large molecules called
starches or complex carbohydrates
• Some starches are stored as potatoes, pasta, rice and bread
• In addition to providing energy for the cell, carbohydrates
are make up some cell parts
– For example
• Cellulose in plant cell walls is a type of carbohydrate
• Carbohydrates are also found in cell membranes
Lipids
• Fats, oils and waxes are all lipids
• Energy-rich organic compounds made of carbon, hydrogen,
and oxygen
• Lipids contain more energy than carbohydrates
• In addition to their function as an energy source
lipids also make up most of the cell membrane
Proteins
• Most body parts are protein
Hair
Skin
Muscles
Bird feathers
Spider webs
Fish scales
Finger and Toe nails
• Protein molecules must be
broken down into amino acids
Structure of Proteins
• Protein molecules are made
up of smaller molecules called
amino acids
• There are only 20 common
amino acids, but can combine
to form thousands of different
proteins
• The 20 amino acids are like
the 26 letters of the alphabet
that can combine thousands
of words
Functions of Proteins
•
Much of the structure of cells is made up of proteins
•
Proteins form parts of cell membranes
•
Proteins also make up many of the organelles within the cell
Enzymes
• Enzymes are proteins speed up chemical reactions in cells
• Without enzymes, many chemical would either take too long
or not occur at all
– For example—
Enzymes in your saliva speed up the digestion of food
by breaking down starches into sugars in your mouth
Nucleic Acids
• Large molecules of carbon, oxygen,
hydrogen, nitrogen, and phosphorus
• Made of four different
kinds of nucleotides
• Differences among living
things depends on the
order of the nucleotides
in the DNA
• Nucleic acids contain the
instructions that cells need to carry
out all the functions of life.
•
There are two kinds of nucleic acids
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Deoxyribonucleic acid or DNA
–
DNA is the genetic material determines traits which are
passed from parent to offspring
–
DNA also directs all cell functions Most of the DNA in a cell is
found in the chromatin in the nucleus
• Ribonucleic acid or RNA
– Plays an important role in the
production of proteins
– RNA is found in the cytoplasm as
well as in the nucleus
Cell Diversity
• Cells come in many shapes
– Nerve cells have long,
fingerlike extensions
which help transmit
information
– Red blood cells have a
flattened shape so that they
can fit through tiny blood
vessels
• Some cells contain certain organelles
but not others
– For example, not all plant cells have
chloroplasts
– Since root cells grow
underground, they
have no need for
chloroplasts
• Cells may also have more of a
particular kind of organelle
– For example, cells that
produce proteins, like liver
cells, contain many more
ribosomes than other cells
Vacuole
Liver Cell
Ribosomes
The Cell Environment
•
Cells must let things enter and leave it
•
The cell membrane allows some substances to pass
through it while other substances cannot
•
Waste materials
move out of the cells
•
Oxygen, food
molecules, and
water move into
the cell
Diffusion
•
Substances that can move into and out of a cell do so by
one of three methods:
1. Diffusion is the process by which molecules move from
an area of higher concentration to an area of lower
concentration
2. Osmosis is the diffusion of water molecules through a
the cell membrane
3. Active and Passive Transport
-Diffusion and osmosis do not require the cell to use its
own energy—this is called passive transport
-Active transport is the movement of materials through a
cell membrane using cellular energy
•
Cells have several ways of moving materials by active
transport
1. Transport proteins in the cell membrane “pick up”
molecules outside the cell and carry them in, using energy
Transport proteins also carry molecules out of the cell in a
similar way
Cell membrane may contain many transport proteins
Each transport protein can carry a specific substance.
2.Transport by engulfing
First 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
The cell must use
energy in this
process
• Cells are so small that they are measured in units called
micrometers
• One micrometer is one millionth of a meter
• One square centimeter of your skin surface contains more
than 100,000 cells
• Cell are usually
visible only through
a microscope
100,000
cells
• Untill around the year 1600, no one knew
cells existed
• Around 1590, invention of the microscope
made it possible to see cells
• Two early discoverers of cells are
Robert Hooke and Antonj van Leeuwenhoek
• Hooke conceived the name “cells” because under a
microscope, they looked like the monistary
rooms, called cells,
that monks lived in
Robert Hooke
• Hooke built his own compound microscope
• He used his microscope to observe the structure of a
thin slice of cork
• He calculated that a cubic inch of cork had about twelve
hundred million cells (1,200,000,000)
Antonj van Leeuwenhoek
• van Leeuwenhoek was a Dutch businessman who built
simple microscopes in his spare time
• He looked at drops of pond water and noticed many tiny
organisms moving through the water
• He called these moving organisms “animalcules”
meaning "little animals"
Levels of Cell Organization
• Organisms consisting of only one cell are
called unicellular
• Organisms consisting of two or more cells
are called multicellular
The lowest level of organization is the SINGLE CELL
• Multi-celled organisms have individual cells that are
specialized to perform specific functions
The second level of organization is TISSUE
• A group of the same types of cells working together to
perform a function
Skeletal Muscle
Voluntary Muscle
xylem
Striated Muscle
Smooth Muscle
Cardiac Muscle
The Third level of organization is the ORGAN
• A group of tissues working together to perform a
function
LEAF
HEART
Epidermal Tissue
Cardiac Muscle Tissue
Nerve Tissue
Blood Tissue
Phloem Tissue
Chlorophyll
The 4th level of organization is the ORGAN SYSTEM
• A group of organs working together to perform a
function
Moo
Circulatory
System
Digestive System
Stomach
Intestines
Heart
Arteries
Veins
Pancreas
The 5th level of organization is ORGANISM
• A group of organ systems working together to perform
a function