Chapter 4:
Cell Structure
and Function
Microscopes
History
• 1400’s: magnifying glass
• 1590: Jansen Bro
– Used 1st compound
microscope (2 lenses)
• 1670-80’s: Anton van
Leeuwenhoek
– Used a simple light
microscope (1 lens)
– 1st person to observe living
microorganisms
– Father of Microbiology
Terms:
• Magnification: enlarges an
object’s image
• Resolution: increases
visible detail
– Separation of 2 points
Light Microscopes
• uses light
• Simple (1 lens)
• Compound (2 or more lenses)
– 1 ocular eyepiece
– 1 objective eyepiece
• Stereomicroscope
– Gives a 3-D image
• Fluorescent dyes combine with video
camera to produce 3-D image of cell
processes (ex: cell movement)
Total Magnification
• ocular lens x objective lens
– Examples: 100 = (10x) x (10x)
430 = (10x) x (43x)
• Highest magnification with a light microscope
is 1500x
Electron Microscopes
• uses beams of electrons
• Transmission electron
microscope (TEM)
– Transmits electrons
through a specimen up
to 200,000x
– Can study structures
within a cell
• Scanning electron microscope (SEM)
– Sends electrons across the surface of a
specimen to make a 3-D image up to
100,000x
• Scanning tunneling microscope (STM)
– Uses a metal probe to show the arrangement of
atoms (1,000,000x)
– Investigates atoms on the surface of a molecule
Advantages/Disadvantages of
each microscope:
• Light Microscope:
– Advantages: can look at living specimens
– Disadvantages: limited in magnification and resolution
• Electron Microscope:
– Advantages: greater magnification and resolution
– Disadvantages: cannot view living things
Microscope Venn Diagram
Light Microscope
Electron Microscope
Cells
Robert Hooke
• Studied cork (dead
plant cells from the
bark of a tree)
• First identified cells
(basic building blocks
of all living things)
Matthias Schleiden and
Theodor Schwann
• Schleiden plants
are made up of cells
• Schwann  animals
are made up of cells
Cell Theory
• 3 parts to the cell theory- applies to all living
organisms
– all organisms are composed of 1 or more
cells
– the cell is the basic unit of structure and
function (organization) of all living things
– all cells come from pre-existing cells
Cells
•
•
•
•
•
Basic units of all living things
Surrounded by a plasma membrane
Have DNA (contains genetic information)
Have cytoplasm (outside the nucleus)
Contain organelles
– membrane-bound structures
– small, specialized structures
– each has a specific function that helps cells survive
• 2 groups of cells
Prokaryotes
• Smaller in size
• Do not have membrane-bound
organelles
• Have genetic material (DNA) but
not surrounded by a membrane
– Circular DNA floats in cytoplasm
• Unicellular organisms (bacteria)
• ****No nucleus or nuclear
membrane***
• have ribosomes, cytoplasm, and
cell membrane
Eukaryotes
• Contain membrane-bound organelles
• Multicellular organisms and some
unicellular (amoeba, algae, and yeast)
• Contain a nucleus
– Control center of the cell
– Contains a cell’s genetic material
– Responsible for cell division
– Manages all cellular functions
– Identified by Rudolf Virchow
• Protists, fungi, plants, and animals
• Bigger in size than prokaryotes
Cell Types Venn Diagram
Prokaryotes
Eukaryotes
Bell Ringer:
1. Cell Theory:
a. All __________ are composed of cells.
b. Cells are the basic units of _______ and ________ in
all organisms.
c. New cells are produced from ____________.
2. The cells of eukaryotes have a _________; the cells of
__________ do not.
3. Eukaryotic cells also have a variety of specialized structure
called ______________.
Levels of Organization
• Cells in multicellular organisms are specialized (cell specialization)
– Perform specific functions (separate roles)
– Ex: nerve cells  transmit impulses
– Ex: red blood cells  carry nutrients and gas throughout body
– Ex: pancreatic cell  produce insulin
– Ex: muscle cells  contract and relax to move parts of the body
organism
organ systems
organization
organs
tissues
• Cells: basic units
cells
– Ex: red blood cells, nerve cells, pancreatic cells, skin cells
• Tissues: group of cells that perform a particular function
– Ex: muscle tissue, epithelial tissue
• Organs: group of tissues that work together
– Ex: heart, liver, stomach, brain, lungs
• Organ systems: group of organs that work together to
perform a specific function
– Ex: digestive, respiratory, nervous
Organelle DNA
• Chloroplasts and mitochondria have their own DNA
• Lynn Margulis
– Came up with the endosymbiotic theory
– Suggested that mitochondria and chloroplasts came from
prokaryotic cells
• Formed a relationship with early eukaryotic cells
Cell Wall
Function:
• Provides additional support and protection
• Allows H2O, O2, AND CO2 to pass
Type of Cell:
• Plant cells, fungal cells, and bacterial cells
Cell Wall
Unique
Characteristics:
• Rigid structure
• Inflexible
• Made of cellulose (in • Nickname: “support
plants)
center”
Plasma Membrane
Function:
• Allows substances to enter and leave a
cell
• Provides protection and support
Type of Cell:
• Plant and animal cells
Plasma Membrane
Unique Characteristics:
• Flexible boundary
• Nickname: “the
bouncer”
Nucleus
Function:
• Controls cell processes
• Stores DNA and info to make proteins
Type of Cell:
• Plant and animal cells
Nucleus
Unique Characteristics:
• Has chromatin
– Strands of DNA
• Has nuclear envelope
• Nickname: “Control
Center” or “The
Boss”
Vacuole
Function:
• Temporary storage of food, enzymes, wastes,
and other materials
Type of Cell:
• Plant and animal cells
Vacuole
Unique
Characteristics:
• Sac surrounded by
a membrane
• Bigger in plants
• Nickname: “Storage
closet”
Mitochondria
Function:
• Transforms energy into usable compounds by
breaking down food
• Cellular respiration
Type of Cell:
• Plant and animal cells
Mitochondria
Unique Characteristics:
• Has double membrane
• Folded inner
membrane 
increases surface area
• Occurs in varying #’s
• Nickname:
– Example: more in muscle
cells
“Powerhouse” or
“Mighty-chondria”
Chloroplast
Function:
• Captures light energy and makes food
• Photosynthesis
Type of Cell:
• Plant cells only
Chloroplast
Unique Characteristics:
• Double membrane
• Plastids used for
storage
• Contain chlorophyll
– Green pigment
• Nickname: “Green
sugar shack”
Ribosomes
Function:
• Where proteins are made
Type of Cell:
• Plant and animal cells
Ribosomes
Unique
Characteristics:
• Not bound by a
membrane
• Can be found in
cytoplasm or ER
• Nickname” “Protein
factory”
Nucleolus
Function:
• Makes ribosomes
Type of Cell:
• Plant and animal cells
Nucleolus
Unique
Characteristics:
• Within the nucleus
• Small and dense
• Nickname: “Ribosome
factory”
Cytoplasm
Function:
• Clear gelatinous fluid inside a cell
• Holds organelles in place
Type of Cell:
• Plant and animal cells
Cytoplasm
Unique
Characteristics:
• Mostly made of
water
• Nickname: “Celly
jelly”
Endoplasmic Reticulum
Function:
• Rough: protein synthesis
• Smooth: make and store lipids
Type of Cell:
• Plant and animal cells
Endoplasmic Reticulum
Unique
Characteristics:
• Highly folded
membranes
• Internal
membrane system
• Nickname: “Transport
system”
Lysosomes
Function:
• Digests excess or worn out organelles, food,
and bacteria
Type of Cell:
• Animal cells
Lysosomes
Unique Characteristics:
• Contains digestive
enzymes
• Nickname: “Suicide
sac”
Cytoskeleton
Function:
• Support structure within cytoplasm
• Forms framework for the cell
Type of Cell:
• Plant and animal cells
Cytoskeleton
Unique
Characteristics:
• Composed of tiny
rods and filaments
• Nickname: “Body
shaper”
Golgi Apparatus or Golgi Body
Function:
• Modifies, sorts, and packages proteins
Type of Cell:
• Plant and animal cells
Golgi Apparatus or Golgi Body
Unique
Characteristics:
• Flattened system
of tubular
membranes
• Nickname: “Gift
wrap” or “UPS”
Cilia
Function:
• Aids in locomotion and feeding
Type of Cell:
• Animal cells
Cilia
Unique Characteristics:
• Pairs of microtubules
• Short, numerous
hairlike projections
• Nickname: “Hair”
Flagella
Function:
• Aids in locomotion and feeding
Type of Cell:
• Animal cells
Flagella
Unique
Characteristics:
• Pairs of
microtubules
• Longer projections
• Whiplike motion
• Nickname: “Tail”
Centrioles
Function:
• Function during cell division
Type of Cell:
• Animal cells
Centrioles
Unique
Characteristics:
• None
Nickname: none
Nuclear Envelope
Function:
• Surrounds nucleus
Type of Cell:
• Plant and animal cells
Nuclear Envelope
Unique Characteristics:
• Has pores that allow
materials to move in
and out of the
nucleus
No nickname
Animal vs. Plant Cells Venn Diagram
Animal Cells
Plant Cells
Bell Ringer:
1. Place the following terms in order from smallest to largest level of
organization:
tissues, organ systems, organs, individual cells
2. The small dense region in the nucleus where the assembly of
ribosomes begins is called the ____.
a. nucleolus
b. nuclear envelope
c. chloroplast
d. vacuole
3. Which organelles can use energy from sunlight to create energy-rich
food molecules?
a. lysosomes
b. golgi apparatus
c. vacuoles
d. chloroplasts