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Life on a Cellular Level
Mrs. Geist
Biology
Fall 2010-2011
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Warm-Up 09/08/10
What
is a cell?
Does
a smaller organism have smaller
or fewer cells? Why?
Does
a larger organism have larger or
a greater number of cells? Why?
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Standards/Essential Questions
 SCOS
2.02 Investigate and describe the structure
and function of cells including: cell organelles, cell
specialization, communication among cells within
an organism.
 Essential
question(s): - What are the three parts of
the cell theory?
 What
is the relationship between surface area and
volume?
 Why
are there limits on cell size?
 Distinguish
between prokaryotes and eukaryotes.
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Cell Size
 Cell
size is limited
 Smaller
cells are more efficient than larger
cells.
 Surface
area-to-volume ratio decreases as a
cell grows larger in size
 Harder
for larger cells to pass materials in and
out of the cell membrane and throughout the cell
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Surface Area-to-Volume Ratio
 To
simplify things, we will consider cells to
be cuboidal for this exercise.
 Surface
area = length x width x 6 sides
 Volume
= length x width x height
 Ratio
= surface area/volume
 Complete
the data table
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Surface Area-to-Volume Ratio
Cell
Dimensions
(cm)
1
1x1x1
2
2x2x2
3
4x4x4
4
8x8x8
Surface Area
(cm2)
Volume (cm3)
SA/V Ratio
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Surface Area-to-Volume Ratio
Cell
Dimensions
(cm)
Surface Area
(cm2)
Volume (cm3)
SA/V Ratio
1
1x1x1
= 1 x 1 x 6= 6
=1x1x1=1
= 6/1 = 6 = 6:1
2
2x2x2
= 2 x 2 x 6 = 24 = 2 x 2 x 2 = 8
= 24/8 = 3 = 3:1
3
4x4x4
= 4 x 4 x 6 = 96 = 4 x 4 x 4 =
64
= 96/64 = 1.5 =
3:2
4
8x8x8
=8x8x6=
384
= 384/512 = 0.75
= 3:4
=8x8x8=
512
+ Why study cells?
Cell biology aids in understanding human diseases and
the design of therapeutics to treat these diseases.
Duchene muscular
dystrophy
Cystic fibrosis
Sickle cell anemia
+ Multicellular organisms are made up of many
different cell types that each carry out a particular
function.
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The Discovery of the Cell

Cells are not visible to the naked eye.

Early Microscopes
 In 1665, Robert Hooke used an early
compound microscope to look at a thin
slice of cork, a plant material.
 Cork looked like thousands of tiny,
empty chambers.
 Hooke called these chambers “cells.”

The cell is the basic unit of life.
Hooke’s Drawing of Cork Cells
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The Discovery of the Cell
At
the same time, Anton van
Leeuwenhoek used a single-lens
microscope to observe pond water and
other things.
The
microscope revealed a world of
tiny living organisms.
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The History of the Cell
 1838-
Matthias Schleiden concluded that
all plants were made of cells.
 1839- Theodor Schwann stated that all
animals were made of cells.
 1855- Rudolph Virchow concluded that
new cells were created only from division
of existing cells.
 These discoveries led to the cell theory.
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The Cell Theory
1.
All living things are composed of
cells.
2.
Cells are the basic units of structure
and function in living things.
3.
New cells are produced from
existing cells.
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Cells
Cells
come in a variety of shapes and
sizes.
All
cells:
 are
surrounded by a barrier called a cell
membrane.
 at some point contain DNA.
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The Nucleus
 Cells
are classified into two categories,
depending on whether they contain a
nucleus.
 Eukaryotes
are cells that contain nuclei.
 Prokaryotes are cells that do not contain nuclei.
 Nucleus-
large membrane-enclosed
structure that contains the cell's genetic
material (in the form of DNA).
 The
nucleus controls many of the cell's
activities.
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Nucleus
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Prokaryotes
 Prokaryotic
cells have genetic material
that is not contained in a nucleus.
 do
not have membrane-bound organelles.
 generally
smaller and simpler than
eukaryotic cells.
 Ex: bacteria
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Eukaryotes
 Eukaryotic
cells contain a nucleus in which
their genetic material is separated from the rest
of the cell.
 generally larger and more complex than
prokaryotic cells.
 generally contain dozens of structures and
internal membranes.
 Many eukaryotic cells are highly specialized.
 Ex: Plants, animals, fungi, and protists
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Rapid Review
09/08/2010
To be completed in class work section of your binder.
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 The
cell theory states that new cells are
produced from
 nonliving material.
 existing cells.
 cytoplasm.
 animals.
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 The
a.
b.
c.
d.
person who first used the term cell was
Matthias Schleiden.
Lynn Margulis.
Anton van Leeuwenhoek.
Robert Hooke.
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Homework

Define the following terms in your own words: (1) organelle,
(2) nucleus, (3) plasma membrane, (4) selective permeability,
(5) phospholipid, (6) fluid mosaic model, and (7) transport
protein.

Fold your paper in half lengthwise. Terms go on the left-hand
side. Definitions go on the right-hand side.

Due tomorrow, Thursday 09/09/10.
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Warm-up 09/09/10

Describe why oil and water do not mix.

What kinds of substances might need to enter a cell?

What kinds of substances might need to leave a cell?
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Eukaryotic Cell Structures
 Structures
within a eukaryotic cell that perform important
cellular functions are known as organelles.
 Cell
biologists divide the eukaryotic cell into two major
parts:
 Nucleus

The nucleus is the control center of the cell.

Contains nearly all the cell's DNA, which is the coded instructions for
making proteins and other important molecules.
 Cytoplasm

The cytoplasm is the portion of the cell outside the nucleus.
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Plant Cell
Nucleolus
Nucleus
Smooth
endoplasmic
reticulum
Nuclear envelope
Ribosome (free)
Rough endoplasmic
reticulum
Ribosome
(attached)
Golgi
apparatus
Cell wall
Cell membrane
Chloroplast
Mitochondrion
Vacuole
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Animal Cell
Nucleolus
Nucleus
Nuclear envelope
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosome (free)
Cell membrane
Ribosome
(attached)
Centrioles
Mitochondrion
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Golgi
apparatus
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The Structure of the Nucleus
Chromatin
Nucleolus
Nuclear envelope
Nuclear pores
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The Structure of the Nucleus
The nucleus is surrounded
by a nuclear envelope
composed of two membranes.
The envelope is dotted with
nuclear pores
Nuclear pores allow material
to move in and out of the
nucleus.
Nuclear
envelope
Nuclear
pores
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Chromatin
The granular material in the nucleus is called chromatin.
Chromatin consists of DNA bound to protein.
Chromatin
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Chromosomes
When a cell divides, chromatin condenses to form
chromosomes.
Chromosomes contain the genetic information that is passed
from one generation of cells to the next.
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Nucleolus
Most nuclei also contain a nucleolus.
The nucleolus is where the assembly of ribosomes begins.
Nucleolus
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Ribosomes
One of the most important jobs carried out in
the cell is making proteins.
Proteins are assembled on ribosomes.
Ribosomes are small particles of RNA and
protein found throughout the cytoplasm.
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Ribosomes
Ribosomes produce proteins by following coded
instructions that come from the nucleus.
Cells that are active in protein synthesis are often
packed with ribosomes.
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Endoplasmic Reticulum
Eukaryotic cells contain an internal membrane system
called the endoplasmic reticulum, or ER.
The endoplasmic reticulum is where lipid components
of the cell membrane are assembled, along with
proteins and other materials that are exported from the
cell.
2 types of Endoplasmic Reticulum
1. Smooth ER
2. Rough ER
Endoplasmic Reticulum
Ribosomes
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2 Types of Endoplasmic Reticulum
1. Rough Endoplasmic Reticulum
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Involved in protein synthesis

Ribosomes are found on the surface of the Rough (ER)
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Abundant in cells that produce large amounts of protein for
export.

Proteins produced in the Rough ER move into the Golgi
apparatus.
2. Smooth Endoplasmic Reticulum
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Does not have ribosomes on its surface.

Contains enzymes that perform specialized tasks
Synthesis of membrane lipids
detoxification of drugs.
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Golgi Apparatus
The Golgi apparatus modifies, sorts, and packages
proteins and other materials from the endoplasmic
reticulum for storage in the cell or secretion outside the
cell.
From the Golgi apparatus, proteins are then “shipped” to
their final destinations throughout the cell or outside of the
cell.
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Golgi Apparatus
The Golgi apparatus modifies, sorts, and packages
proteins.
Notice the stacklike membranes that make up the
Golgi apparatus.
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Lysosomes
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Lysosomes are small organelles filled with enzymes.
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Lysosomes break down lipids, carbohydrates, and proteins
into small molecules that can be used by the rest of the cell.

Lysosomes also break down organelles that have outlived
their usefulness.
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Vacuoles
Some cells contain saclike
structures called vacuoles that
store materials such as water, salts,
proteins, and carbohydrates.
In many plant cells there is a
single, large central vacuole filled
with liquid.
The pressure of the central
vacuole allows plants to support
heavy structures such as leaves
and flowers.
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Vacuole
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Vacuoles
Vacuoles are also found in some
unicellular organisms and in some
animals.
The paramecium contains a
contractile vacuole that pumps
excess water out of the cell.
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Contractile vacuole
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Mitochondria
Nearly all eukaryotic
cells contain
mitochondria.
Mitochondria convert
the chemical energy
stored in food into
compounds that are
more convenient for the
cell to use.
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Mitochondria
Mitochondria are enclosed by two membranes
1. outer membrane
2. inner membrane.
The inner membrane is folded up inside the
organelle.
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Chloroplasts
Plants and some other
organisms contain
chloroplasts.
Chloroplasts capture
energy from sunlight and
convert it into chemical
energy in a process called
photosynthesis.
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Chloroplasts
Chloroplasts are surrounded by two membranes.
Chloroplasts contain the green pigment
chlorophyll.
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Cytoskeleton
Eukaryotic cells are given their shape and internal
organization by the cytoskeleton.
The cytoskeleton is a network of protein filaments
that helps the cell to maintain its shape.
The cytoskeleton is also involved in movement.
The cytoskeleton is made up of:
 microfilaments
 microtubules
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Cytoskeleton
Cell membrane
Endoplasmic
reticulum
Microtubule
Microfilament
Ribosomes
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Mitochondrion
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Cytoskeleton  Microfilaments
 Microfilaments:
 are
threadlike structures made up of the protein
actin.
 form extensive networks in some cells.
 produce a tough, flexible framework that
supports the cell.
 help some cells move.
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Cytoskeleton  Microtubules
 Microtubules
are hollow structures made up of
proteins known as tubulins.
 Microtubules:
 maintain
cell shape.
 are important in cell division.
 build projections from the cell surface—cilia and
flagella—that enable some cells to swim rapidly
through liquids.
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Cytoskeleton  Centrioles
In animal cells, structures known as centrioles are formed
from tubulin.
Centrioles are located near the nucleus and help to organize
cell division.
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7-2
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In the nucleus of a cell, the DNA is usually visible as
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a dense region called the nucleolus.

the nuclear envelope.

granular material called chromatin.

condensed bodies called chloroplasts.
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7-2
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Two functions of vacuoles are storing materials and helping to
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break down organelles.

assemble proteins.

maintain homeostasis.

make new organelles.
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7-2
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Chloroplasts are found in the cells of

plants only.

plants and some other organisms.

all eukaryotes.

most prokaryotes.
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7-2
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Which of the following is NOT a function of the Golgi apparatus?

synthesize proteins

modify proteins

sort proteins

package proteins
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7-2
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Which of the following is a function of the cytoskeleton?

manufactures new cell organelles

assists in movement of some cells from one place to another

releases energy in cells

modifies, sorts, and packages proteins
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7-2
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Which of the following is a function of the cytoskeleton?

manufactures new cell organelles

assists in movement of some cells from one place to another

releases energy in cells

modifies, sorts, and packages proteins
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Microscopy
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How do we study
cells?
 The
invention of the
microscope led to the
discovery of the cell.
 Light
microscopes can
magnify images up to 1,000
times the actual size.
 At
higher magnifications, the
image blurs and more
efficient microscopes are
necessary.
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Microscopes
 Microscopes
vary in magnification and resolving
power.
 Magnification is the ratio of an object’s image to
its real size.
 Resolution is the ability to distinguish between 2
points.
 Resolution is limited by the wavelength of light.
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An visual example of how big a cell and its parts are
Magnified by a factor of 10
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Electron Microscopes

Electron microscopes reveal details
1000 times smaller than those visible in
light microscopes.

Electron microscopy can be used to
visualize only nonliving, preserved
cells and tissues.

Transmission electron microscopes
(TEMs)

Used to study cell structures and large
protein molecules

Specimens must be cut into ultra-thin
slices
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Electron Microscopes
 Scanning
electron microscopes
(SEMs)
 Produce three-dimensional
images of cells
 Specimens do not have to be
cut into thin slices
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Scanning Electron micrograph of neurons
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Confocal Light Microscopes

Confocal Light Microscopes scan cells with a laser beam.

This makes it possible to build 3-D images of cells and their
parts.
Confocal Light
Micrograph of HeLa Cells
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Scanning Probe Microscopes

Scanning Probe Microscopes allow us to observe single
atoms.

Images are produced by tracing surfaces of samples with a
fine probe.
Scanning Probe
Micrograph of
DNA
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 Electron
microscopes are capable of revealing
more details than light microscopes because
a. electron microscopes can be used with live
organisms.
b. light microscopes cannot be used to examine
thin tissues.
c. the wavelengths of electrons are longer than
those of light.
d. the wavelengths of electrons are shorter than
those of light.
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 Which
a.
b.
c.
d.
organism listed is a prokaryote?
protist
bacterium
fungus
plant
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 One
way prokaryotes differ from eukaryotes is
that they
a. contain DNA, which carries biological
information.
b. have a surrounding barrier called a cell
membrane.
c. do not have a membrane separating DNA from
the rest of the cell.
d. are usually larger and more complex.
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