Section 7-1
Are All Cells Alike?
All living things are made up of cells. Some
organisms are composed of only one cell. Other
organisms are made up of many cells.
1.
What are the advantages of a one-celled
organism?
2.
What are the advantages of an organism
that is made up of many cells?
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Section:
Section Outline
Section 7-1
7–1 Life Is Cellular
A. The Discovery of the Cell
1. Microscopes
2. The Cell Theory
B. Exploring the Cell
C. Prokaryotes and Eukaryotes
1. Prokaryotes
2. Eukaryotes
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Section:
Section 7-1
Discovery of the Cell
1. Robert Hooke – 1665 – named cell
2. Leeuwenhoek – 1674 – observed living
microorganisms
3. Schleiden – 1838 – all plants made of cells
4. Schwann – 1839 – all animals made of cells
5. Virchow – 1855 - all cells come from cells
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Section:
Section 7-1
Exploring the Cell
Microscopy
- the history of cytology is tied to the
development of the microscope.
1. Light microscopes - pass light through the
specimen
- can magnify up to about 1200x
- easy to prepare specimens and can look at
living specimens.
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Section:
Section 7-1
2. Transmission Electron Microscope
- send a beam of electrons through the
specimen
- focused with magnets
- resolving power up to 100,000(+)x
- specimens have to be prepared and can’t
be alive
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Section:
Section 7-1
3. Scanning Electron Microscope
- bounce electrons off the surface
of the specimen
- gives detailed three-dimensional
images of the surface of the specimen
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Section:
Section 7-1
Cell Theory
Cells are the basic structural and functional units of
life
Under the conditions present on Earth today all cells
come from other cells.
All living things are composed of cells
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Section:
Section 7-1
Prokaryotes-cells that have genetic material
that is not contained in the nucleus.
Generally smaller and more simple
than eukaryotes.
Bacteria are prokaryotes.
Eukaryotes-contains a nucleus in which their
genetic material is separated from the rest of
the cell. Plants, animals, fungi, and protists
are Eukaryotes.
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Section:
Prokaryotic and Eukaryotic Cells
Section 7-1
Cell membrane
Cytoplasm
Prokaryotic Cell
Cell membrane
Cytoplasm
Nucleus
Eukaryotic Cell
Organelles
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Section:
Venn Diagram
Section 7-1
Prokaryotes
Cell membrane
Contain DNA
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Section:
Eukaryotes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Section 7-2
Division of Labor
A cell is made up of many parts with different functions that
work together. Similarly, the parts of a computer work together
to carry out different functions.
Working with a partner, answer the following questions.
1. What are some of the different parts of a computer? What
are the functions of these computer parts?
2. How do the functions of these computer parts correspond
to the functions of certain cell parts?
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Section:
Section Outline
Section 7-2
7–2 Eukaryotic Cell Structure
A. Comparing the Cell to a Factory
B. Nucleus
C. Ribosomes
D. Endoplasmic Reticulum
E. Golgi Apparatus
F. Lysosomes
G. Vacuoles
H. Mitochondria and Chloroplasts
1. Mitochondria
2. Chloroplasts
3. Organelle DNA
I. Cytoskeleton
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Section:
Section 7-2
Nucleus
“control center” of the cell
Contains the chromosomes on which the genes are located
Fine threads called chromatin in nondividing cells
Condense into visible chromosomes during cell division
Nuclear membrane has two parallel membranes with
nuclear pores penetrating them
Nuclear pores allow mRNA to leave the nucleus to go to
the cytoplasm
Also contains the nucleolus where ribosomal subunits are
produced
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Section:
Section 7-2
Ribosomes
- sites of protein synthesis – where amino acids are
joined
- many are attached to Rough ER; others are free in
the cytoplasm
- composed of RNA and protein
- attached ribosomes make proteins for export
- free ribosomes make proteins for intracellular use
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Section:
Section 7-2
Endoplasmic Reticulum
- membranous-walled canals and flat sacs that
extend from the plasma membrane to the nucleus
- important in the synthesis, modification, and
movement of materials within the cell
A. Rough Endoplasmic Reticulum
- has ribosomes attached to its’ surface
- ribosomes make proteins which move into
the cisternae of the ER and are transported
toward the Golgi apparatus
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Section:
Section 7-2
B. Smooth Endoplasmic Reticulum
- lacks ribosomes
- transports, synthesizes, and
chemically modifies small molecules
- synthesizes certain lipids and
carbohydrates and creates
membranes for use throughout the cell
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Section:
Section 7-2
Golgi Apparatus
- series of flattened membranous sacs that modify
protein products of the rough endoplasmic
reticulum
- final products are packaged in vesicles which can
then be moved to the cell membrane for export
- some of these vesicles remain in the cell as
lysosomes
- can also give rise to new membrane structures for
the cell
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Section:
Section 7-2
Lysosomes
- digestive system of the cell
- membranous sacs which pinch off the Golgi
apparatus
- contain hydrolytic enzymes which digest particles
or large molecules that enter them
- also responsible for digesting unneeded or
unhealthy cells and cell parts
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Section:
Section 7-2
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Section:
Section 7-2
Vacuoles
- saclike structures used for storage within the cell
- stores water, salts, proteins, and carbohydrates
- discerning feature in many plant cells that is
large and liquid filled
makes possible for plants to support heavy
structures such as leaves and flowers
- in many cases the vacuole is controls the water
content of the cell which maintains homeostasis
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Section:
Section 7-2
Mitochondria
- “power plants” of cells
- double membraned organelle with fluid between
the membranes
- lots of enzymes attached to both membranes
- enzymes catalyze oxidation reactions of cellular
respiration and capture the energy of sugars in the
bonds of ATP
- provide 95% of the cell’s energy
- contain their own ribosomes and DNA and can
replicate themselves
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Section:
Section 7-2
Chloroplasts
- capture the energy of the sunlight and convert it
into the chemical energy of sugar in a process
called photosynthesis
- double membraned organelle like mitochondria
- also contain their own DNA
- contain large stacks of membranes containing
chlorophyll
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Section:
Section 7-2
Cytoskeleton
Internal support framework made up of rigid,
rodlike proteins that support the cell and allow
movement and mechanisms that can move the
cell or its parts
Acts as both muscle and skeleton for cell
Cell Fibers
- form a three-dimensional support framework
- support endoplasmic reticulum, mitochondria,
and free ribosomes
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Section:
Section 7-2
1. Microfilaments – smallest fibers
- cellular muscles that provide for movement
2. Intermediate filaments – form much of the
support network of the cell
3. Microtubules – maintain cell shape and move
things within the cell made up of proteins known as
tublin
4. Tubulin is also used to make structures in
animal cells known as the centrioles. These aid in
organization during cell division
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Section:
Figure 7-11 Cytoskeleton
Section 7-2
Cell membrane
Endoplasmic
reticulum
Microtubule
Microfilament
Ribosomes
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Section:
Mitochondrion
Figure 7-5 Plant and Animal Cells
Section 7-2
Smooth endoplasmic
reticulum
Vacuole
Ribosome
(free)
Chloroplast
Ribosome
(attached)
Cell
Membrane
Nuclear
envelope
Cell wall
Nucleolus
Golgi apparatus
Nucleus
Mitochondrion
Rough endoplasmic reticulum
Plant Cell
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Section:
Figure 7-5 Plant and Animal Cells
Section 7-2
Nucleolus
Nucleus
Ribosome
(attached)
Nuclear
envelope
Mitochondrion
Smooth
endoplasmic
reticulum
Rough
endoplasmic
reticulum
Centrioles
Golgi apparatus
Animal Cell
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Section:
Ribosome
(free)
Cell
Membrane
Venn Diagram
Section 7-2
Animal Cells
Centrioles
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Section:
Plant Cells
Cell membrane
Ribosomes
Nucleus
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Mitochondria
Cytoskeleton
Cell Wall
Chloroplasts
Section 7-3
In or Out?
How is a window screen similar to a cell membrane? Read
on to find out.
1.
What are some things that can pass through a
window screen?
2.
What are some things that cannot pass through a
window screen? Why is it important to keep these things
from moving through the screen?
3. The cell is surrounded by a cell membrane, which
regulates what enters and leaves the cell. Why is it
important to regulate what moves into and out of a cell?
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Section:
Section Outline
Section 7-3
7–3 Cell Boundaries
A. Cell Membrane
B. Cell Walls
C. Diffusion Through Cell Boundaries
1. Measuring Concentration
2. Diffusion
D. Osmosis
1. How Osmosis Works
2. Osmotic Pressure
E. Facilitated Diffusion
F. Active Transport
1. Molecular Transport
2. Endocytosis and Exocytosis
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Section:
Section 7-3
Cell Membrane
All of the membranes of the cell have similar structure.
Plasma Membrane
-Fluid Mosaic Model – developed by Singer and Nicolson
-Molecules are arranged in a sheet
-Molecules are held together by chemical attractions between
them and their interactions with water.
-Primary structure is a double layer of phospholipid molecules
Phosphate heads are hydrophilic; tails are hydrophobic
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Section:
Section 7-3
Cell Membrane-cont.
-Cholesterol molecules within the membrane help it function at
body temperatures.
-Because the hydrophobic tails make-up most of the membrane,
water soluble materials can’t pass through the membrane.
-Channel proteins which are embedded in the membrane help
control movement of materials into and out of the cell
-Glycoproteins have carbohydrates attached and serve as cell
surface identifiers
-Receptor proteins react to specific chemicals and cause changes
within the cell.
-Overall, the plasma membrane is selectively permeable.
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Section:
Figure 7-12 The Structure of the
Cell Membrane
Section 7-3
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
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Section:
Protein
channel
Lipid bilayer
Section 7-3
Cell Walls
-Provide support and protection for the cell.
-Most are composed of fibers of carbohydrate
and protein
-Plant cell walls are mostly cellulose
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Section:
Passive and Active Transport
Section 7-3
Section 7-3
Movement Through the Cell Boundaries
Passive Transport Processes
-Do not require energy expenditure by the cell
-Second Law of Thermodynamics
Diffusion
- movement of particles from an area of high
concentration to an area of low concentration down a
concentration gradient.
- continues until equilibrium is reached
- membrane channels are pores through which
specific ions or small water-soluble molecules can pass
- gases also move by diffusion
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Section:
Diffusion and Osmosis Video
Section 7-3
Section 7-3
Passive Transport Processes cont.
Osmosis
- diffusion of water through a selectively
permeable membrane
- water moves down it’s concentration gradient –
this often means it is moving toward higher salt
concentrations
- Osmotic Pressure – water pressure that
develops as a result of osmosis
- healthy cells are normally in an environment
where the net movement of water is 0.
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Section:
Section 7-3
Passive Transport Processes cont.
Osmosis cont.
- Tonicity – ability of a solution to move water
in/out of a cell and change its shape
a. Isotonic – osmotic pressure is = inside and
outside
b. Hypertonic – osmotic pressure is greater than
within the cell – water moves out of cell causing
crenation
c. Hypotonic – osmotic pressure is less than within
the cell – water moves into the cell causing lysis.
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Section:
Figure 7-15 Osmosis
Section 7-3
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Section:
Figure Osmosis
Section 7-3
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Section:
Osmosis Video
Section 7-3
Facilitated Diffusion
Section 7-3
Glucose
molecules
Facilitated Diffusion
- movement through
carrier proteins
along the
concentration
gradient
- rate is dependent
on concentration
gradient and
availability of carrier
molecules
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Section:
High
Concentration
Cell
Membrane
Low
Concentration
Protein
channel
Section 7-3
Molecule to
be carried
Active Transport
-cell uses metabolic energy
to move materials
1. Molecular Transport
- carrier-mediated process
that moves substances against
their concentration gradients
- opposite of diffusion
- substances are moved by
pumps which use ATP to change
shape and move their cargos
- carrier proteins bind to
cargo, change shape, and release
the cargo
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Section:
Energy
Molecule
being carried
Active Transport
Section 7-3
Section 7-3
Active Transport (cont.)
2. Endocytosis and Exocytosis
- allow things to enter and leave a cell without
actually passing through the plasma membrane.
A. Endocytosis – plasma membrane traps some
extracellular material and moves it to the interior in a
vesicle.
- Phagocytosis – large particles are engulfed
within a vesicle that then fuses with lysosomes to digest
particles
- Pinocytosis – fluid and the substances dissolved
in it enter the cell
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Section:
Endocytosis and Exocytosis
Section 7-3
Section 7-4
From Simple to More Complex
Many multicellular organisms have structures
called organs that have a specific function and
work with other organs. Working together, these
organs carry out the life processes of the entire
organism.
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Section:
Section 7-4
1.
Some activities cannot be performed by
only one person, but need a team of people.
What type of activity requires a team of
people to work together in order to complete
a task?
2.
What do you think are some
characteristics of a successful team?
3.
How is a multicellular organism similar to
a successful team?
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Section:
Section Outline
Section 7-4
7–4The Diversity of Cellular Life
A.Unicellular Organisms
B.Multicellular Organisms
1.Specialized Animal Cells
2.Specialized Plant Cells
C. Levels of Organization
1.Tissues
2.Organs
3.Organ Systems
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Section:
Section 7-4
Unicellular Organisms
Single-celled organisms that grow, respond to
the environment, transform energy, and
reproduce
Multicellular Organisms
Organisms that are made up of many cells that
are developed for different tasks through a
process called cell specialization
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Section:
Levels of Organization
Section 7-4
Muscle cell
Smooth muscle tissue
Levels of Organization
1. Cells
2. Tissues
3. Organs
4. Organ Systems
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Section:
Stomach
Digestive system
Interest Grabber Answers
1. What are the advantages of a one-celled organism?
A one-celled organism has simpler needs and can respond immediately to
its environment because its entire cell is immersed in its environment.
2. What are the advantages of an organism that is made up of many cells?
In a multicellular organism, different jobs are divided among different
groups of cells that work together. Also, a multicellular organism can
continue to survive even if it loses some of its cells.
Interest Grabber Answers
Working with a partner, answer the following questions.
1. What are some of the different parts of a computer? What are the functions
of these computer parts?
Answers may include: monitor (interfaces with the computer’s
environment), software (instructions for how to carry out different jobs),
CPU (directs the computer's activities), recycle bin or trash can (storage
area for wastes), and so on.
2. How do the functions of these computer parts correspond to the functions
of certain cell parts?
Students should try to link the functions they described in question 1 to the
functions of the different cell structures. The cell needs a way to interface
with its environment (cell membrane), instructions for carrying out different
jobs (DNA), and a CPU to direct the cell’s activities (nucleus).
Interest Grabber Answers
1. What are some things that can pass through a window screen?
Answers may include air, fine dust, and rainwater.
2. What are some things that cannot pass through a window screen? Why is
it important to keep these things from moving through the screen?
Insects, leaves, and other matter that may fall from trees. The screen
keeps out annoying insects and objects that may bring dirt into the home.
3. The cell is surrounded by a cell membrane, which regulates what enters
and leaves the cell. Why is it important to regulate what moves into and out
of a cell?
Materials such as oxygen and food that are needed by the cell have to be
able to get inside the cell. At the same time, excess materials have to leave
the cell.
Interest Grabber Answers
1. Some activities cannot be performed by only one person, but need a team
of people. What type of activity requires a team of people to work together
in order to complete a task?
Answers might include building a human pyramid or constructing an arch
out of blocks.
2. What do you think are some characteristics of a successful team?
Divide up jobs and cooperate well with one another.
3. How is a multicellular organism similar to a successful team?
The functions of the organism are divided up among its parts (organs and
organ systems). All the parts cooperate to carry out all the functions of the
whole organism.
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