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Chapter 7: Cell Structure and Function
The Discovery of the Cell
 Early
Microscopes allowed us
to see cells for the first time!
– The earliest lenses in Europe
allowed us to see the quality of
cloth and tiny insects, which
appeared small and blurry.
– Scientists didn’t use
microscopes to study nature
until the 1600’s.
7-1 Life is Cellular
 Anton
van Leeuwenhoek (1632-1723)
Discovered the new world of
microorganisms when he looked at
pond water through his microscope.
Leeuwenhoek greatly improved the
quality of lenses
“Cells” named by
Robert Hooke
Robert Hooke was one of the first
to look at objects under the
microscope.
Robert Hooke looked at cork
(from the Cork Oak Tree).
He thought the compartments looked like
little rooms, or “cells”.
The name stuck.
The History of the Cell Theory



In 1838, Matthias Schleiden stated that all
plants are made of cells.
In 1839, Theodore Schwann stated that all
animals were made of cells.
In 1855, Rudolf Virchow stated that cells
could only come from other cells.
- This is unlike how we bake cakes or
build automobiles.
The Cell Theory
1. All living things are made of cells.
2. Cells are the basic units of
structure & function in living things.
3. New cells are produced from existing
cells.
Cells come in all shapes & sizes
But, all cells have 2 characteristics in
common:
1.
2.
They have a cell membrane at some point
in their lives.
They contain DNA.
 There
are 2 categories of cells:
– Prokaryotes
 Cells
that do not have a membrane-bound
nucleus.
– Eukaryotes
 Cells
that do have a membrane-bound
nucleus.
– Pro = before
– Eu = true
– Karyon =kernel
 The
type of cell is based on the
presence (or absence) of a
nucleus & organelles.
– Nucleus –large membrane bound
organelle.
 Contains
the cell’s DNA.
 Controls many of the cell’s activities.
– Organelle –specialized structure that
performs important functions w/in the cell.
 “Tiny
organs”
Prokaryotes
The first cells (bacteria)
 Generally smaller & simpler than
eukaryotic cells.
 Have DNA, but it’s not contained in a
membrane-bound nucleus.
 Most are unicellular.
 Despite their simplicity,
prokaryotes:

–
–
–
–
Grow
Reproduce
Respond to their environment
Some are mobile.
Eukaryotes




Generally larger & more complex than prokaryotes.
Contain membrane bound organelles and a nucleus.
Can be unicellular or multicellular.
Found in animals, plants, fungi, and protists
Pro-k vs. Eu-k
Review
Prokaryotes
Eukaryotes
Cell membrane
Contain DNA
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Plant vs. Animal Cell
Animal Cells
Centrioles
Plant Cells
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
Chloroplasts
Cell Structures
Cell wall
7-2
– provides support & protection for a cell
Cell walls are found
in plants, algae, fungi,
and most prokaryotes
But, NOT animals!
Cell walls are made from
fibers of carbohydrates
and proteins
Follow along in your textbook...
(p. 173)

Cells can be subdivided into 2 main parts:
1.Cytoplasm – portion of the cell between
the nucleus and the cell membrane.
Includes the organelles
Do not confuse the
cytoplasm
with the cytosol...
Analogy:
cytoplasm is like vegetable soup
cytosol is like the broth
2. Nucleus – the control center of the cell

Contains almost all of the cell’s DNA, the coded
instructions for making proteins & other important
molecules.
The nuclear envelope is a
double membrane that
surrounds the nucleus.
Found in eukaryotic cells only
On the nuclear envelope you will find
nuclear pores. These pores allow
materials to move in & out of the nucleus
•
•
•
Proteins
RNA
Other molecules
(p. 175)
 Chromatin
–a granular material
visible w/in the nucleus.
– It consists of DNA tightly coiled around
proteins.
– Most of the time chromatin is spread
throughout the nucleus.
– However, when a cell divides, chromatin
condenses to form chromosomes.
 Another
structure found in most nuclei
is a nucleolus.
– The nucleolus assembles ribosomes.
(p. 176)
Figure 7-7
Analogy...Comparing the Cell to a Factory

Organelles – means “little organs”.
– Specialized structures that carry out specific
functions in a cell... They each have a job to do.
Organelles are found within the cytoplasm.
As we learn about each organelle, we can compare it to parts of a factory.
For example: the nucleus is like
the boss who sends out
instructions... DNA.
Now lets look at organelles:
ribosomes,
endoplasmic reticulum,
Golgi apparatus,
lysosomes,
vacuoles,
mitochondria,
and chloroplasts
Ribosomes
Ribosomes –small particles of RNA & protein
found throughout the cytoplasm.


Ribosomes make proteins by following coded
instructions that come from the nucleus.
– These instructions are RNA (ribonucleic acid)
Cells that are major
protein producers often
have numerous ribosomes.
... Like an assembly line
(p. 177)
Endoplasmic reticulum

Endoplasmic Reticulum (ER)– organelle in which
components of the cell membrane are assembled and some
proteins are modified.
There are 2 portions to ER... Rough ER and Smooth ER
 Rough ER
Involved in the synthesis of proteins.
Called “rough” b/c ribosomes are found on its surface
Newly made proteins enter the rough ER & are modified.
 Smooth ER
No ribosomes are found on the surface
Contains collections of enzymes that perform special
tasks such as: Synthesis of membrane lipids
Detoxification of drugs
Liver cells tend to have a large amounts of smooth ER.
Rough and Smooth Endoplasmic reticulum
Cross section of ER
 RER
 SER
Golgi Apparatus
Proteins made in the
ER move to the
Golgi Apparatus (GA)
These proteins can be stored in the
cell or secreted out of the cell.
The GA looks like a
stack of closely
opposed membranes,
(or a stack of pita bread)
Golgi apparatus
See Figure 7-9
Factory analogy:
Like a factory’s customized
shop, where finishing
touches are put on the
products.
Sequence pathway of proteins ...
Central nucleus 
Interconnected rough ER 
Golgi  Outer plasma membrane
Lysosomes
The clean up crew,
Or recycling container
Lysosome –small organelles filled w/
digestive enzymes.
 Lysosomes
are involved in:
– Breaking down old organelles.
– Digesting foreign matter in the cell.
Example of what can happen when cells don’t work
 Tay-Sachs
-a disease is caused by
lysosomes that fail to properly do their
job.
– Fatal by the age of 4.
– More common in eastern European Jews
Vacuoles and Vesicles
 Vacuoles
–an organelle that stores
materials such as:
–
–
–
–
Water
Salts
Proteins
Carbs
 Plants
have large central vacuoles
that can hold water & wastes.
Factory analogy – Storage and shipping containers
Smaller vacuoles, especially those that transport
substances within a cell, are called vesicles.
(p. 179)
Figure 7-10
Mitochondria & Chloroplasts
 The
power plants of a cell.
 Most
cells get their energy (E) in 2 ways:
– Food (Heterotrophs)
– Sun (Autotrophs)
 Mitochondria:
– Can be found in almost all eukaryotic cells.
 Including
plant cells.
– Converts chemical E into compounds that are
easy for the cell to use.
 Ex:
ATP (Adenosine Triphosphate)
These high energy compounds
are used to power growth,
development, and movement
(p. 180)
 Mitochondria
membranes.
are enclosed by 2
– An outer membrane
– An inner membrane
 Highly
folded on itself.
 Creates more surface area for chemical
reactions.
 Chloroplasts:
– Found in plants & some other orgs.
– They capture sunlight & convert it into
chemical E by photosynthesis.
 This
chemical E is then converted to ATP by
mitochondria in the plant.
– Also surrounded by 2 membranes.
– Contains a green pigment called
chlorophyll.
 Chloroplasts
Organelle DNA
 Chloroplasts
& mitochondria contain
their own DNA.
– No other organelles do.
 It
is believed that both of these
organelles are ancient descendants
of prokaryotes.
 This
is called the endosymbiotic theory.
Cytoskeleton
 Cytoskeleton
–a network of protein
filaments that helps the cell maintain
its shape.
– It is also involved in movement.
 The
cytoskeleton is made up of:
– Microfilaments
– Microtubules
 Microfilaments:
– Threadlike
– Made of actin
– Forms a tough, flexible framework that
supports the cell.
– Also responsible for cytoplasmic
movement of the cell.
 Microtubules:
– Hollow tube-like structures
– Made of tubulin
– Critical to maintaining cell shape.
– Also form structures called spindles during
cell division.
– Tubulin is also used to make centrioles.
– Located near the nucleus.
 Help organize cell division. Microtubules also
help w/ movement.
– They make up cilia & flagella.
P. 181, fig. 7-11
Section 7-3
Cell Boundaries
Cell Boundaries
7-3
 All
cells are surrounded by a thin
barrier called the cell membrane.
 Many
cells also have a strong
supporting layer around that
membrane called the cell wall.
Cell Membrane
 Cell
membranes regulate what enters &
leaves a cell.
 They
also aid in protection & support.
 Nearly
all cell membranes are a
flexible, double layered sheet
called a lipid bilayer.
– P. 182, fig. 7-12
Along w/ lipids,
the cell membrane
also has proteins &
carbohydrates
embedded in it.
The lipid bilayer
is often called a
mosaic, b/c it is
made up of many
different parts.
 The
proteins form channels & pumps
for moving materials across the
membrane.
 The carbohydrates act like ID cards,
allowing individual cells to identify
one another.
 http://www.youtube.com/watch?v=Q
qsf_UJcfBc&feature=related
 http://www.youtube.com/watch?v=v
h5dhjXzbXc
Cell Walls (CW’s)
 Found
in:
– Plants
– Algae (Protists)
– Fungi
– Many prokaryotes
(not all)
 CW’s
lie outside the
cell membrane.
Onion
Ragweed
 Most
cell walls allow certain
substances to pass through.
 Such as:
– H20
– CO2
– O2
 Its
main function is to support &
protect the cell.
 Most
CW’s are made of fibers of
carbohydrate & protein.
 Plant
CW’s are made of cellulose.
– Cellulose is a tough carbohydrate fiber.
– The fiber in your diet.
Diffusion Through Cell Boundaries
 The
movement of molecules from
one side of the cell membrane to the
other.
Measuring Concentration
 Recall
what a solution is.
– What’s a solute?
– What’s a solvent?
 Concentration
–the mass of solute in
a given volume of solution, or
mass/volume.
 Lets figure concentration of a
solution.
– If you dissolved 12g of salt in 3L of
water, the concentration would be:
12g/3L = 4 g/L
Diffusion
 Diffusion
–process of molecules
moving from an area of high
concentration to an area of low
concentration.
– Equilibrium –when the concentration of
a solute is the same throughout a
solution.
 Diffusion
reached.
will go on until EQ is
 What
does diffusion have to do w/ a
cell membrane?
– P. 184, fig. 7-14
 Diffusion
cell.
– It’s free!
requires no E output by the
Osmosis

Biological membranes are selectively
permeable.
– Some substances can pass & some can’t.

Water passes very easily.

However, many solutes can’t.

Osmosis –the diffusion of water through a
selectively permeable membrane.
How Osmosis Works
 H2O
moves from an area of high H2O
concentration to an area of low H2O
concentration.
 Water
moves across the membrane
until EQ is reached.
Osmosis
Section 7-3
 http://www.youtube.com/watch?v=s
diJtDRJQEc&feature=related
3 types of Osmotic Solutions:
P. 186, fig. 7-16

Isotonic
– Concentrations are equal on both sides of the
membrane.
– Normal looking cells

Hypertonic
– Solution outside the cell has a higher solute
concentration than the inside of the cell.
– Water leaves the cell.
–

Cells shrink
Hypotonic
– Solution has a lower solute concentration than the cell.
– Water enters the cell.
– Cells swell
Plant Cells
Plant Cells
 http://www.youtube.com/watch?v=G
OxouJUtEhE&feature=related
Turgid
Flaccid
Red Blood Cells
Osmotic Pressure



Osmosis exerts a pressure known as
osmotic pressure.
Osmotic pressure -the pressure exerted by
the flow of water through a semi
permeable membrane.
This can cause serious problems for a cell.
– Cells can swell to the point of bursting.
 Fortunately,
animal cells are in a
isotonic solution & don’t come into
contact w/ pure H2O.
– If they did they would burst.
 Also,
plant cells & bacterial cells have
cell walls that prevent the cell from
bursting.
Facilitated Diffusion
 Facilitated
diffusion –movement of
specific molecules across CM’s via
protein channels.
– P. 187, fig. 7-17
 There
are hundreds of protein
channels that allow only certain
substances to cross different
membranes.
 This
 It
process does not require E.
acts just as diffusion.
– It goes from high to low concentrations.
Facilitated Diffusion
 http://www.d.umn.edu/~sdowning/
Membranes/diffusionanimation.html
Active Transport
 When
cells move materials against
the concentration gradient, they are
using Active Transport.
– This process requires E.
 Active
transport is carried out by
transport proteins or pumps found in
the membrane.

Transport of larger molecules can
be done through 2 active transport
processes:
1. Endocytosis
–
P. 188, fig. 7-18
2. Exocytosis
– For each of these processes, the shape
of the membrane changes.
Endo & Exo
 http://www.youtube.com/watch?v=K
7yku3sa4Y8&feature=related
Molecular Transport

Endocytosis –process of taking material
into the cell by infolding or pocketing of
the CM.
– This process forms a vacuole in the
cell.
– This process works for:



taking in food
larger molecules
other cells
– 2 examples of endocytosis are:


Phagocytosis
Pinocytosis
 Phagocytosis
– extensions of
cytoplasm surround a particle &
package it w/in food vesicles.
– Amoebas use this method
 Fig.
7-18
 Pinocytosis
–the process of taking in
liquids from the surrounding env.
 Many
cells also release large
amounts of material from the cell.
 This process is called exocytosis.
 Ex:
– The removal of water by a contractile
vacuole is an example of this kind of
active transport.
 http://highered.mcgraw-
hill.com/sites/0072437316/student_
view0/chapter6/animations.html#
Section 7-4
The Diversity of Cellular
Life
Unicellular Organisms
 Unicellular
orgs. –made of one cell.
 Unicellular
orgs. can:
– grow
– respond to the env.
– reproduce
– transform E
 Unicellular
Earth.
 Examples
orgs. dominate life on
on P. 190, fig. 7-20
Multicellular Organisms



Orgs. made up of many cells.
Multicellular orgs. have cells that are
specialized.
Cell Specialization –process in which cells
develop in different ways to perform
different tasks.
– P. 191, fig. 7-21
Specialized Animal Cells
 Examples
animals:
of specialized cells in
– Red blood cells
 Transport
O2 throughout the body.
– Pancreatic cells
 Produce
enzymes that aid in digestion.
 Contain cells specialized for making
proteins.
– These cells have numerous ribosomes.
– Muscle cells
 Able
to contract & relax, causing movement
of our bones.
Specialized Plant Cells
 Guard
cells of the stomata:
– Monitor a plants internal conditions, &
makes changes accordingly.
Levels of Organization
 The
levels of organization in a
multicellular org. are as follows:
– Individual Cells
– Tissues
– Organs
– Organ systems
– Organism
 P.
192, fig. 7-22
Examples
neurons
(nerve cells)
nervous tissue
brain
central nervous system
human

Tissue –a group of similar cells that
perform a specific function.
– Ex:
 The
collection of cells in the pancreas that make
proteins.
– Most animals have 4 types of tx:
 Muscle
 Epithelial
 Nervous
 connective
 Organs
–many groups of tx’s working
together.
– Each muscle is an organ.
– However, it also contains nervous tx, &
connective tx.
 Organ
system –a group of organs
working together to perform a
specific function.
– Digestive system
– Reproductive system
– Nervous system
 Altogether,
organ systems make up
the organism.
Body Systems