Chapter 7:
Cell
Structure
and
Function
7-1 Life Is Cellular
Robert Hooke
(1635-1703)
English Scientist
First to use the
microscope to
observe cells
Coined the term “cell”
Looked at cork cells
7-1 Life Is Cellular
Anton van Leeuwenhoek
1632-1723
Dutch scientist
Invented the first
compound
microscope
First to observe
LIVING cells
Blood cells and
protists
7-1 Life Is Cellular
Robert Brown
1773-1858
Scottish botanist
In 1831 he was the
first person to observe
the nucleus of a cell
7-1 Life Is Cellular
Developing Cell Theory 1838
Schleiden
Said “all plants
are made up of
cells”
1804-1881
Schwann
Said “all animals
are made up of
cells”
1810-1882
7-1 Life Is Cellular
Rudolph Virchow 1855
“All cells arise only from
preexisting cells.”
7-1 Life Is Cellular
Cell Theory Overview
1. All organisms are made of one or more cells.
1. All cells carry on life activities.
2. New cells arise only from other living cells.
7-1 Life Is Cellular
Exploring the Cell
There are 3 major types of microscopes
1. Light Microscope
•
•
•
•
•
Magnifies Up to 1,000 X
Eyepiece magnifies 10X
Total magnification calculation:
eyepiece X objective being used.
Exampleeyepiece (10X) times low power
objective (4X) = 40X
Light must pass through.
Uses slides, can observe living things
7-1 Life Is Cellular
Exploring the Cell
2. Dissecting Microscope
Magnifies 10 to 30 times
Eyepiece magnifies 10X
Objectives: 1X and 2X (3X)
Used to magnify objects that light
cannot pass through
Used mostly by research scientists
and jewelers
Advantage: objects are 3-D
Disadvantage: can’t view small
objects
7-1 Life Is Cellular
Exploring the Cell
3. Electron Microscope
Uses electrons to illuminate objects
Can magnify from 30,000 to 9 million times
Two types: Transmission and Scanning
Costly to own and maintain
Can only be used to look at dead specimens
Used for cytology, forensics, and virology
7-1 Life Is Cellular
Exploring the Cell
TEM -Transmission Electron Microscope
•TEM- thin slices need to be made to have clear images,
images are 2-D
•Useful for studying internal structures
7-1 Life Is Cellular
Exploring the Cell
•SEM- Scanning Electron Microscope
samples do not need to be cut, are in 3-D
• Useful for studying external structure
7-1 Life Is Cellular
Two Types of Cells
1. PROKARYOTE: do NOT contain a membrane bound
nucleus
(all bacteria are prokaryotes)
2. EUKARYOTE: DO contain a membrane bound nucleus,
and most have other specialized organelles.
7-1 Life Is Cellular
Prokaryotes and Eukaryotes
7-1 Life Is Cellular
Prokaryotic vs Eukaryotic
PROKARYOTIC
Simplest form
Lack membrane
bound structures
Example: bacteria and
some protists
EUKARYOTIC
Most common
Possess membrane
bound structures and
a nucleus
Found in most living
things
7-1 Life Is Cellular
Cell Size
1. Cells are small because materials need to get
into and out of the cell at a rate that will meet
the cell’s needs.
2. Surface area – to – volume ratio
a. Larger surface area/volume ratio, the
more materials a cell can exchange
b. As cell size increases, surface area to
volume ration decreases
7-1 Life Is Cellular
Cell Size
7-2 Eukaryotic Cell Structure
Common cell structures
Cell Membrane

Thin flexible barrier around the cell
Nucleus


Contains genetic material
Controls cell’s activities
Cytoplasm

Material inside the cell surrounding the
organelles
7-4 Diversity of Cellular Life
ANIMAL CELL VS. PLANT CELL
7-2 Eukaryotic Cell Structure
PLANT CELL
7-2 Eukaryotic Cell Structure
ANIMAL CELL
7-2 Eukaryotic Cell Structure
Cell Organelles
7-2 Eukaryotic Cell Structure
Cell Organelles
Organelle
“little organ”
Found only inside
eukaryotic cells
All the stuff in
between the
organelles is cytosol
Everything in a cell
except the nucleus
is cytoplasm
7-2 Eukaryotic Cell Structure
Cell Membrane
Boundary of the cell
Made of a phospholipid bilayer
7-2 Eukaryotic Cell Structure
Nucleus
Control center of the cell
Contains DNA
Surrounded by a
double membrane
Usually the easiest
organelle to see under a
microscope
Usually one per cell
7-2 Eukaryotic Cell Structure
Cytoskeleton
Acts as skeleton and muscle
Provides shape and structure
Helps move organelles around the cell
Made of three
types of filaments
Endoplasmic
Reticulum
7-2 Eukaryotic Cell Structure
A.k.a. “ER”
Connected to
nuclear membrane
Highway of the cell
Rough ER: studded
with ribosomes; it
makes proteins
Smooth ER: no
ribosomes; it makes lipids
7-2 Eukaryotic Cell Structure
Ribosome
Site of protein synthesis
Found attached to rough
ER or floating free in cytosol
Produced in a part of
the nucleus called
the nucleolus
That looks familiar…what is a
polypeptide?
7-2 Eukaryotic Cell Structure
Golgi Apparatus
Looks like a stack of plates
Stores, modifies and
packages proteins
Molecules transported
to and from the Golgi
by means of vesicles
7-2 Eukaryotic Cell Structure
Lysosomes
Garbage disposal
of the cell
Contain digestive
enzymes that
break down wastes
Which organelles do
lysosomes work with?
7-2 Eukaryotic Cell Structure
Mitochondria
“Powerhouse of the cell”
Cellular respiration occurs
here to release energy for the
cell to use
Bound by a double membrane
Has its own strand of DNA
7-2 Eukaryotic Cell Structure
Chloroplast
Found only in plant cells
Contains the green
pigment chlorophyll
Site of food
(glucose) production
Bound by a double
membrane
7-2 Eukaryotic Cell Structure
Cell Wall
Found in plant and bacterial cells
Rigid, protective barrier
Located outside of the
cell membrane
Made of cellulose (fiber)
7-2 Eukaryotic Cell Structure
Vacuoles
Large central vacuole
usually in plant cells
Many smaller vacuoles
in animal cells
Storage container for
water, food, enzymes,
wastes, pigments, etc.
What type of microscope may have
been used to take this picture?
7-2 Eukaryotic Cell Structure
Centriole
Helps with cell division
Usually found only in
animal cells
Made of microtubules
Where else have we talked
about microtubules?
7-2 Eukaryotic Cell Structure
Quick Review
Which organelle is the control center of the cell?
nucleus
Which organelle holds the cell together?
cell membrane
Which organelles are not found in animal cells?
cell wall, central vacuole, chloroplasts
Which organelle helps plant cells make food?
chloroplasts
What does E.R. stand for?
 endoplasmic reticulum
7-4 Diversity of Cellular Life
What are the parts?
7-3 Cell Boundaries
Cell Boundaries: Cell Wall
Found in plants, algae, fungi,
and nearly all prokaryotes.
MAIN FUNCTION: provide
support & protection for the
cell. Plants have cellulose
Animal cells DO NOT have
cell walls!
Cell Boundaries: Cell
Membrane
7-3 Cell Boundaries
Controls what materials move in and out
Helps to maintain homeostasis
Similar to the “city limits”
Made up of three substances :

Lipids, proteins, and carbohydrates
Cell Boundaries: Cell
Membrane
7-3 Cell Boundaries
Fluid-Mosaic Model
7-15 The StructureCell
of the
Cell Figure
Boundaries:
Cell Membrane
Membrane
7-3 Cell Boundaries
Section 7-3
Fluid-Mosaic Model
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Go to
Section:
Protein
channel
Lipid bilayer
7-3 Cell Boundaries
Selectively permeable
Some substances pass
through while others
may not.
Regulates chemical
composition
Maintains homeostasis
7-3 Cell Boundaries
Maintaining Homeostasis
All cells must regulate what materials enter &
leave; sometimes no energy is required to do
this, other times energy is required

Passive transport –
no energy is required to
move substances from
an area of high
concentration to an
area of low concentration
7-3 Cell Boundaries
Types of Passive Transport
Diffusion – the movement of a solute from an area of high
conc. To an area of low conc. Equilibrium is reached when an
equal number of molecules move in both directions
7-3 Cell Boundaries
Diffusion
Movement of
molecules from a
region of high
concentration to a
region of low
concentration
7-3 Cell Boundaries
Types of Passive Transport
Osmosis – the diffusion of water across a membrane from a
region of high water concentration to a region of low water
concentration
http://www.youtube.com/watch?v=sdiJtDRJQEc (osmosis animation)
7-3 Cell Boundaries
Osmosis
Diffusion of WATER across a selectively
permeable membrane from a region of high
water concentration to a region of low
water concentration.
Osmotic pressure =

Increased pressure resulting from osmosis
7-3 Cell Boundaries
Osmosis
Higher Concentration
of Water
Water molecules
Cell
membrane
Lower Concentration
of Water
Sugar molecules
7-3 Cell Boundaries
Types of Osmotic Solutions
Isotonic solution –
solution has the
same solute
concentration as
that of the living cell,
there is no net
movement of H2O
7-3 Cell Boundaries
Isotonic Solution
Same concentration of dissolved
substances in solution as there is in the cell
Same water concentrations
Net result

No net gain or loss of water
7-3 Cell Boundaries
Types of Osmotic Solutions
Hypertonic solution–
solution has a higher
solute concentration
than the inside of the
cell; H2O moves out of
the cell; animal cell will
shrink (crenate);
vacuole collapses in
plant cells
7-3 Cell Boundaries
Hypertonic Solution
A high concentration of dissolved
substances outside the cell
More water in the cell than outside the cell
Net result : cell loses water and contracts
7-3 Cell Boundaries
Types of Osmotic Solutions
Hypotonic solution
– solution has a
lower solute
concentration than
the inside of the cell;
H2O moves into the
cell; animal cell will
burst (lyse); plant
cell will not (why?)
7-3 Cell Boundaries
Hypotonic Solution
Lower concentration of dissolved
substances in solution than in the cell
More water outside the cell than inside the
cell
Net result : cell fills and may burst
7-3 Cell Boundaries
Types of Osmotic Solutions
7-3 Cell Boundaries
Types of Osmotic Solutions
7-3 Cell Boundaries
You can see the effects of
Osmotic Pressure
Osmotic pressure allows plant stems to
stand against gravity
7-3 Cell Boundaries
Types of Passive Transport
Facilitated diffusion – process by which transport proteins
carry certain molecules across a membrane from high
concentration to low concentration
7-3 Cell Boundaries
Facilitated Diffusion vs. Active
Transport
FACILITATED
DIFFUSION
No energy needed
Concentration
gradient determines
movement
Uses protein channels
ACTIVE
Usually works against
the concentration.
gradient
Often a transport
protein helps the
movement (ATP)
7-3 Cell Boundaries
Active Transport
Energy is required to move substances from
an area of low concentration to an area of
high concentration; allows cells to have
internal environments that are different
chemically from the external environment
7-3 Cell Boundaries
Active transport requires energy!
7-3 Cell Boundaries
Types of Active Transport
Molecular transport - proteins in the cell
membrane work as “pumps” to move
substances against the concentration
gradient
7-3 Cell Boundaries
Molecular Transport
• Small molecules & ions are carried across
the cell membrane by protein pumps
• Examples of pumps include: calcium,
potassium, and sodium
7-3 Cell Boundaries
Sodium-potassium pump
7-3 Cell Boundaries
Types of Active Transport
Endocytosis - process by which a cell takes
material into the cell by infolding of the cell
membrane


Phagocytosis – large particles taken in
Pinocytosis – H2O or small particles are taken in
Exocytosis – process by which cell releases large
amounts of material; vacuole membrane fuses with
the cell membrane
7-3 Cell Boundaries
Types of Active Transport
7-3 Cell Boundaries
Bulk Transport
Defined: The transportation of large
molecules and even solid clumps of
material
Two main types:
Exocytosis
Endocytosis
7-3 Cell Boundaries
Phagocytosis“cell eating”;
useful for
unicellular
organisms to
take in food or for
WBC’s to engulf
and destroy
bacteria
Ex: Amoeba
feeding
Phagocytosis is specific to what it transports
7-4 Diversity of Cellular Life
Cells Need to communicate –
send and receive signals with each other
7-4 Diversity of Cellular Life
Diversity of Cellular Life
Unicellular- one celled organisms


Bacterial, some protists
Colony – a group of unicellular organisms living
together
Multicellular - more than one cell; cells are
specialized to perform a specific function
7-4 Diversity of Cellular Life
Diversity of Cellular Life
Unicellular
Multicellular
7-4 Diversity of Cellular Life
Levels of Organization
7-4 Diversity of Cellular Life
Tissues:
A group of cells which are
structurally similar and perform
the same function.
7-4 Diversity of Cellular Life
Examples of Tissues
Nerve Tissue
Nerve Cell
7-4 Diversity of Cellular Life
1. Epithelial Tissue
Tissue that covers surfaces inside
and outside the body
Example: skin
Sheets of closely packed cells
7-4 Diversity of Cellular Life
2. Connective Tissue
Supports and binds
tissues and organs
together
Widely separated
cells
EX. bone, blood
7-4 Diversity of Cellular Life
3. Nervous Tissue
Specialized for
electrical impulse
transport
Ex. brain, spinal
cords, nerves
7-4 Diversity of Cellular Life
4. Muscle Tissue
Specialized for contraction
Lots of mitochondria
7-4 Diversity of Cellular Life
Organs
Group of tissues that work together to
perform a specific function
Ex. heart, stomach, flower
7-4 Diversity of Cellular Life
Organ system
Group of organs that perform a specific
task
Ex. digestive, skeletal, circulatory
7-4 Diversity of Cellular Life
5. Levels of Organization
cells --> tissues --> organs --> organ systems --> organisms
Tissue – is a group of
similar cells that work
together to perform a
function.
7-4 Diversity of Cellular Life
Organ – is a
group of
tissues that
work together
to do a job.
7-4 Diversity of Cellular Life
Organ systemis a group of
organs that
work together
to do a certain
job.
7-4 Diversity of Cellular Life
Examples of organisms
Crow
Organism – is a
living thing that can
be made of one or
more cells.
Human
Amoeba
Elephant
Bonobo