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Discovering Cells
Lesson 1
Read and Think about It!!
“For me… no more
pleasant sight has met my
eye than this of so many
thousand of living
creatures in one small
drop of water.”
What are Cells?
Why are microscopes needed in
order to study cells??
Anton van Leeuwenhoek was the
first researcher to see bacteria
under a microscope.
Anton van Leeuwenhoek
Scientis
What are Cells?
Cells: The basic units of structure
and function in living things.
• Cells are the basic unit of ALL
life.
• Cells form the parts of an
organism and carry out all of its
functions.
Cells: Structure and Function
 The structure of all living
organisms is determined by the
variety of ways its cells are put
together.
Organism Function: The processes
that enable an organism to live,
grow and reproduce.
Cells: Structure and Function
Functions Include:
 Obtaining Oxygen
 Obtaining Food
 Obtaining Water
 Getting rid of Wastes
For example: Cells in your digestive system absorb food. The food provides
your body with energy and materials needed for growth. Cells in your lungs
help you get oxygen. Your body’s cells work together, keeping you alive! For
each cell to stay alive, the cell MUST carry out many of the same functions as
the entire organism!!
Cell Theory
 Cells were not seen until the 1600s (1st
microscope was invented around 1590)
 Took 200 years AFTER cells were
discovered to determine cells were the
basic unit of structure and function in
living things.
Cell Theory
Cell Theory: Accepted explanation of the
relationship between cells and living things.
Cell Theory States…
 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.
Looking Inside Cells
How do the Parts of a Cell Work?
 Each cell is made up of even smaller
structures.
 Each kind of cell structure has a different
function within a cell.
Organelles: Cell structures that carryout
specific functions within a cell.
How do the parts of a cell work?
Before going inside the cell… lets talk
about their boarder!!
Cell Membrane: Controls which
substances pass into and out of a cell.
 Food, Oxygen, Water ENTER – Waste
products EXIT
 ALL cells have cell membranes
How do the parts of a cell work?
 Plant cells have a cell membrane AND a
Cell Wall.
Cell Wall: Forms the boarder between the
plant cell and its environment.
 Cell wall is made of cellulose.
A polysaccharide (C6H10O5) that is composed of glucose
units that constitutes the chief part of the cell walls of
plants, occurs naturally in such fibrous products as
cotton and kapok, and is the raw material of many
manufactured goods (as paper, rayon, and cellophane)
How do the parts of a cell work?
 When water inside the cell pushes on the
cell wall the cell becomes rigid.
 Provides support for the entire plant.
 Cell membrane is INSIDE the cell wall.
Organelles -- Nucleus
***Remember: Organelles are tiny structures that
carry out specific functions within a cell***
Nucleus: Cell’s control center. Directs all of
the cell’s activities.
 Large oval structure
 Surrounded by the nuclear
envelope
Nucleus
Nuclear Envelope: A porous membrane
that surrounds the nucleus.
 Materials pass in and out
of the nucleus through pores in the nuclear
envelope.
Chromatin: Thin strands of material that fill
the nucleus.
 Contains information for directing a cell’s
functions
Nucleus
Nucleolus: Small round structure in the
nucleus where ribosomes are made.
Organelles In the Cytoplasm
Cytoplasm: Fills the spaces between the
cell membrane and the nucleus.
 Thick, clear, gel-like fluid
 Fluid in the cytoplasm moves constantly
Ribosomes: Small grain-shaped organelles
that produce proteins.
Organelles In the Cytoplasm
Mitochondria: Rod-shaped structures that
convert energy stored in food to energy the
cell needs to survive.
 Nickname: “Powerhouse” of the cell.
Organelles In the Cytoplasm
Endoplasmic Reticulum: A network of
membranes that produces many substances.
 Ribosomes dot some parts of the ER
 Helps attached ribosomes make proteins
Organelles In the Cytoplasm
 Golgi Apparatus: An organelle that
packages and distributes materials made
in the ER to the cell or to the outside of
the cell.
 Secretes proteins
 Looks like flattened sacs and tubes
 Cell’s “Factory”
Organelles In the Cytoplasm
Vacuoles: A sac that stores water, food or
other materials needed by the cell.
 Can also store wastes
 Plant cells have one or more large
vacuole(s)
 Some animal cells have vacuoles while
some don’t
Organelles In the Cytoplasm
Lysosomes: Contains digestive enzymes to
breakdown large food particles into smaller
ones.
Break down old cell parts and release the
substances so they can be used again.
 “Saclike” organelles
 Nicknamed the cell’s “recycling center”
Organelles In the Cytoplasm
Chloroplasts: Green structures that capture
energy from sunlight and changes it to food
for the plant cell.
 Makes leaves GREEN.
 ONLY IN PLANT CELLS
How Do Cells Work Together in an
Organism?
Some organisms are made of just one cell,
while other organisms are made of many
cells.
Unicellular: Single-celled organisms.
Ex. Euglenas, Amoeba’s, Paramecia
How Do Cells Work Together in an
Organism?
Multicellular: Organisms made of many
cells that perform different functions.
 All cells in multicellular organisms must
carry out key functions to remain alive.
How Do Cells Work Together in an Organism?
 In multicellular organisms, cells are
organized into tissues, organs, and organ
systems.
Cell
Tissue
Organ
Organ System
Organism
How Do Cells Work Together in an Organism?
Tissue: A group of similar cells that work
together to perform a specific function.
Ex. Brain – made mostly of nerve tissue, which
consists of nerve cells.
How Do Cells Work Together in an organism?
 There are 4 basic types of tissue: connective
tissue, epithelial tissue, muscle tissue, and
nervous tissue. Connective tissue supports
other tissues and binds them together (bone,
blood, and lymph tissues). Epithelial tissue
provides a covering (skin, the linings of the
various passages inside the body). Muscle
tissue includes striated (also called voluntary)
muscles that move the skeleton, and smooth
muscle, such as the muscles that surround the
stomach. Nerve tissue is made up of nerve cells
(neurons) and is used to carry "messages" to
and from various parts of the body.
How Do Cells Work Together in an Organism?
Organ: Made of different kinds of tissues
that function together.
Ex. Brain – has blood vessels (made of tissues)
that carry the blood that supplies oxygen to your
brain cells.
Organ System: A group of organs that work
together to perform a major function.
Ex. Brain – An organ that is part of your nervous
system.