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A Look at Cells
-the smallest unit of life
that can carry out all
the functions of a living
organism
-not discovered until the
invention of the
microscope
UNICELLULAR
Some living organisms
are unicellular, only made
of only 1 cell; they are the
smallest of all living
organisms
Ex. Some bacteria
Many protists
Some living organisms
are made of many cellsMULTICELLULAR
Ex. Plants, Animals,
Fungi
Shape is related to Function
Blood Cell-hemocyte;
round to move through vessels
Nerve-neuron; long to carry
message to spinal cord
Muscle-for
contraction and relaxation
Robert Hooke-1665
•Gave the cell its name
•Cork from an oak tree
Anton van Leeuwenhoek1670
•First “real” microscope
•Living organisms in pond
water
protists
bacteria
Robert Brown—1840
•discovered the nucleus of a cell
•Observed the epidermal cells of
orchids and the anthers of
Tradescantia
http://2bnthewild.com/plants/H299.htm
© Peter v. Sengbusch - Impressum
http://www.orchidworks.com/orchids/sept98/carol044.htm
3 men established The Cell Theory
•M. Schleiden 1838, botanist, “all
plants are made of cells”
•T. Schwann 1839, zoologist, “all
animals/organisms are made of
cells”
•R. Virchow 1855, physician, “all
new cells come from other cells”
(biogenesis)
The Cell Theory
1.Cells are the basic units
of all life
2. All organisms are
made of 1 or more cells
3. All cells come from
other cells
Basic Cell Structures
Cell Membrane-phospholipid and
proteins
Cytoplasm-everything inside the
cell except the nucleus/DNA
Cytoskeleton-system of fibers
DNA-the genetic material
Ribosomes-proteins are made on
these
Cell Membrane
Function: Homeostasis
1. Controls what enters and leaves
2. Boundary separating the cell
from its environment
*Figure 11 & 12, p. 60-61
Cell Membrane
Structure:
1. Thin layer of lipids embedded with
proteins
2. Semipermeable (a.k.a. selectively
permeable)
3. 2 phospholipid layers called a
bilayer
4. Hydrophilic (H2O loving) head
5. Hydrophobic (H2O fearing) tail
Cell Membrane
Cytoplasm
Function:
1. Contains or “suspends” structures called
organelles inside the cell
Structure:
1. Jelly like base, consisting mainly of water
and organic compounds called the cytosol
2. Other structures within the cytoplasm vary
3. Contains the cytoskeleton
Cytoplasm
Cytoskeleton
•Function-provides support and a place to “anchor”
other structures
•Structure-composed of protein fibers;
3 types:
• actin fibers – contract and expand to give the cell its
shape
• microtubules – “highway system”; transport
information from nucleus to parts of the cell
• intermediate fibers – framework for
ribosomes/enzymes to be organized for metabolic
pathways
Cytoplasm showing
Cytoskeleton
DNA
•All cells contain DNA at some point in
their life cycle
•Structure-complementary strands in
a double helix
•Function-carries the genetic code
•Replicates itself to pass the
genetic code on to its daughter
cells
DNA
Ribosomes
•Structure-spheres composed of RNA
and protein
•Function-site of protein synthesis
•Free ribosomes make proteins that
remain inside the cell
•Attached ribosomes make proteins
that become part of the cell or are
exported from the cell
These are free ribosomes (in the cytosol). Other
ribosomes are attached to the ER
Ribosomes
Ribosomes
Typical Animal Cell
Typical Plant Cell
Nucleus
Found ONLY in eukaryotes!!!
Function:
1.Control headquarters for the
cell (brain)
Nucleus
Structure:
• Found in the cytoplasm
• Contains the genetic materialchromosomes- made of DNA &
proteins
• Surrounded by a double membranenuclear envelope/membrane
• Inside is a nucleolus that makes
ribosomes
Nucleus
Nucleus
Overview of Organelles
Eukaryotic cells contain a variety of
organelles other than the nucleus. These
include:
•Endoplasmic reticulum (ER) – transport system of
tubes
•Golgi – stacked sacs that package and distribute
materials through the cell
Vesicles – membrane-bound sacs for transport of
proteins
Vacuoles – tiny membrane-bound storage container
•Lysosomes – contain digestive enzymes, “suicide
sacs”
Mitochondria – function in the 2nd part of cell
respiration, taking the energy from small carbon
compounds and storing it in ATP; have their own
DNA “powerhouse of cell”
Centrioles –a region for microtubule assembly once
thought to function in cell division (animal cells
only); part of the centrosome
•Chloroplasts – type of plastid containing
chlorophyll; functions in photosynthesis (plant cells
and a few protists only) ; have their own DNA
•Central vacuole (plant cells only) – large central
structure for storing water and its solutes
Organelles—A Closer Look
Nucleolus
Location
Within the nucleus
Structure
knot of chromatin
Function
Produces ribosomes
Endoplasmic Reticulum
Rough
Structure:
Network of membranes near nucleus
Contains ribosomes on surface
Function: Transports proteins that were
made by the attached ribosomes
through the cell to the golgi.
Endoplasmic Reticulum
Smooth
Structure:
Network of folded membranes throughout cell
Contains no ribosomes on surface
Function:
Makes lipids and breaks down toxic
substances.
Endoplasmic Reticulum
Golgi Apparatus
Location
In the cytoplasm
Structure
Closely stacked, flattened membrane
sacs
Function
 Stores, packages, and transports
products inside for use outside
 Vesicles (a bit of the golgi pinches
for transport of stored materials).
Lysosome
(not found in plants)
StructureSaclike
Contains digestive enzymes
FunctionDigests food particles
Digests old organelles
Mitochondria
(found in all eukaryotic cells)
StructureOval
Inside is a complex matrix of folded membranes to
increase surface area.
FunctionChanges energy stored in food into a more useful
form
Energy storing molecule called adenosine
triphosphate (ATP is formed)
Centrioles
Location
Animal cells only
Structure
9 sets of 3 protein fibers.
Function
Aid in the the division of
chromosomes in mitosis.
Microtubules
Location
Throughout the cell’s structure
Structure
thick filaments made of protein
Function
• gives structure and shape to
cells
• Anchors organelles
Microfilaments
Location
throughout the cell
structure
Structure
hollow, thin protein
tubes
Function
allow for elasticity and
movement within cells.
Vesicles
Location
inside or outside of the plasma/cell membrane
Structure
bits of membrane from the plasma membrane or
the golgi apparatus
Function
Vesicles fuse with the cell membrane may be used to
release or transport chemicals in or out of the cells.
Exocytosis out of the cell
Endocytosis into the cell
Vacuole
Location
cytoplasm
Structure
sac of fluid surrounded by
a membrane
Plants: Large in size
Animals: small in size
Function
Sites of storage of water, ions and some nutrients.
Plants: allows plants to maintain turgor pressure, holds
water to prevent wilting.
In plants, this is referred to as the Large Central Vacuole—
animal cells do not have these, only small ones.
Chloroplast.
Location
Plant cells and some protists
Structure
Double phospholipid bilayer.
Inner layer
– Stacks = grana
– Non stacked area = stroma
Function
• Capturing radiant energy and
converting it to chemical energy.
• Chlorophyll is the green pigment
that traps the energy from the
sun
Cell Wall
Location
surrounding Plant cells
Structure
contains polysaccharide cellulose
Function
• Provides structure and support
for plant cells
Vesicles, Golgi, and ER are all involved in protein
production in the cell. They are all found in both plant and
animal cells.
Mitochondria are
found in both plant and
animal cells. They are
involved in cellular
respiration
Centrioles are found only in animal cells. They were
thought to be involved in cell division. Lysosomes contain digestive enzymes for breaking down toxins and
worn out organelles, invading cells, or “food” for phages
Chloroplasts are found only in plant cells. They
take in light energy and store it in carbohydrates
during photosynthesis.
Note the cell wall and central vacuole in this
diagram of a plant cell. They are also found only
in plant cells.
Flagella and Cilia
Location
outside of cells
Structure
• Cillia: short hair-like
• Flagella long whip-like
Function
Locomotion = movement
• Cilia: tiny, flutters of movement.
• Flagella: one big wave motion will
cause a large amount of movement
 Some Cell Web Sites for Further Study 
•http://sun.menloschool.org/~cweaver/cells/
•http://www.enchantedlearning.com/subjects/biology/cells/
•http://web.jjay.cuny.edu/~acarpi/NSC/13-cells.htm
•http://www.borg.com/~lubehawk/cell.htm
•http://www.rkm.com.au/CELL/
•http://www.rkm.com.au/BACTERIA/bacterial-cell.html
•http://www.emc.maricopa.edu/faculty/farabee/BIOB
K/BioBookCELL2.html#Golgi%20Apparatus%20and%
20Dictyosomes