Download 3 Chapter 3

• Chapter 3 Cells
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Chapter 3 The Cell: Module Hyperlinks
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3.1 Cells are the fundamental units of life
3.2 Plant vs. animal cells
3.3 Membranes: structure
3.4 Membranes: function
3.5 The nucleus
3.6 Organelles in protein production
3.7 Chloroplasts and mitochondria
3.8 Other organelles
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3.1 Opening Questions: Are all living things
made of cells?
• What are at least five things you know
about cells?
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3.1 All living organisms consist of cells.
• Some living organisms
have just one cell.
• Some living organisms
have trillions of cells.
Cells are the fundamental
units of life
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3.1 Cells can be grouped into two categories.
• Prokaryotic cells
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Small, simple cells
No organelles
First appeared 3.5 BYA
Unicellular
• Eukaryotic cells
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Larger, complex cells
Membrane-enclosed organelles
First appeared 2.1 BYA
Unicellular or multicellular
Are you a prokaryote
or a eukaryote?
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3.1 Cells can be grouped into two
categories
All cells on Earth can be classified into two
general kinds:
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Are Homo
sapiens
Bacteria
(humans) a
Small, simple cells
prokaryote
Single celled
or a
Eukaryotic cells
Plants, animals, fungi and protists eukaryote?
Prokaryotic cells
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– Larger, more complex cells
– Single celled or multicellular
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3.1 Cells can be grouped into two categories.
• Prokaryotic cells
– Bacteria and Archaea
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• Eukaryotic cells
– Plants, Animals,
Fungi, and Protists
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3.1 All prokaryotes are relatively simple
single-celled organisms.
• There are two domains of prokaryotes:
Bacteria and Archaea.
• Prokaryotic fossils date back at least
3.5 billion years.
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3.1 Bacteria have some unique features
and some features common to all cells.
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3.1 Bacteria have common and some
unique features
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Common features
Cell wall
Plasma membrane
Cytoplasm
Ribosomes
Nucleoid region with
DNA
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Unique features
Capsule
Flagellum
Plasmids
Pili
3.2 Opening Questions: What are you really
made of?
• Did you know that scientists estimate that
only maybe one in 10 of the cells in your
body are actually human! The rest are
largely prokaryote cells. These good
bacteria help us digest food, synthesize
vitamins, and protect against disease.
• How is it possible to have more bacteria
cells than human cells?
• Does knowing the above change your view
of bacteria?
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3.2 Animals and Plants are made of
eukaryotic cells that contain organelles.
• Compared to prokaryotic cells, eukaryotic
cells are relatively large (10-fold bigger)
and more complex.
• Eukaryotic cells contain
organelles, which are
membrane-enclosed
structures that perform
specific functions.
Prokaryotes do not contain organelles!
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3.1 Eukaryotic cells are bigger and more
complex
• Animals, fungi, plants, and protists are all
eukaryotes.
• Eukaryotes evolved from prokaryotes
around 2 billion years ago.
3.2 Plant and animal cells have many
organelles in common.
• All eukaryotic cells
are fundamentally
alike.
• All eukaryotic cells
have:
– Plasma
membrane
– Nucleus
– Mitochondria
– Ribosomes
– Cytoplasm
– Endoplasmic
reticulum
– Golgi
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Chapter Table of Contents
3.2 Structure of an idealized animal cell
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3.2 Structure of an idealized plant cell
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3.2 Animal and plant cells have some
unique organelles.
• Animal cells have
lysosomes.
• Plant cells have
chloroplasts, cell
walls, and central
vacuoles.
Looking at cells under a
microscope, you see cell
walls and chloroplasts.
What type of cells are
these?
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3.2 Some cells have unique organelles
• Only animal cells have lysosomes.
• Only plant cells have chloroplasts, cellulose cell walls,
and central vacuoles.
• Some animal cells, protists and prokaryotic cells have
flagella and/or cilia
– Plant cells do not
• Bacteria have
– Peptidoglycan cell wall, plasma membrane, cytoplasm,
ribosomes, DNA
– Some bacteria have capsule, flagellum, cilia, thylakoid
membranes
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3.3 Every cell is surrounded by a plasma
membrane.
• All cells are
surrounded by a
plasma membrane.
• Membranes regulate
the passage of
materials.
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3.3 Membranes are made of lipids
• Plasma membranes are made from two
layers of phospholipids and integrated
proteins.
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3.3 Structure of a plasma membrane
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3.4 Membranes regulate the passage of
materials.
• Cells are surrounded by a
plasma membrane.
• Organelles may have their
own outer and internal
membranes.
The most important function
of any membrane is to
regulate the flow of materials.
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3.4 Membranes regulate what substances
can enter and leave the cell.
• Every membrane is
selectively permeable.
• Some substances
flow freely.
• Others pass under
certain circumstances.
• Some cannot pass.
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GO
YIELD
STOP
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3.4 Transport across membranes can be
passive or active.
• Passive transport requires no energy.
– Substances move along a concentration
gradient from high to low.
• Active transport requires energy.
– Substances move against a concentration
gradient from low to high.
Active transport is like trying
to get into a crowded club!
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3.4 Passive transport: Diffusion
Higher concentration
• Diffusion is the
movement of
molecules from an
area of higher
concentration to an
area of lower
concentration.
Lower concentration
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3.4 Passive transport: Osmosis
aquaporins
• The diffusion of
water is called
osmosis.
• Water will always
flow from an area of
higher water
concentration to an
area of lower water
concentration.
• Aquaporins are
proteins in the
plasma membrane
for osmosis
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Lower concentration
Higher concentration
Chapter Table of Contents
3.4 Passive transport: Facilitated diffusion
Higher concentration
• Large molecules can
move through
embedded transport
proteins via
facilitated diffusion.
• Substances still move
from an area of higher
concentration to an
area of lower
concentration.
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Lower concentration
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3.4 Active transport requires energy to
move substances.
• Active transport involves
moving a substance from
an area of lower
concentration to an area
of higher concentration.
• Moving a substance
against its concentration
gradient always requires
an expenditure of energy.
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Lower concentration
Higher concentration
Chapter Table of Contents
3.4 Active transport is usually driven by a
protein that sits within the membrane.
Here, you can see a protein called the sodium-potassium
(Na+/K+) pump moving three sodium ions into the cell.
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3.4 Active transport is usually driven by a
protein that sits within the membrane
• the sodium-potassium (Na+/K+) pump moves
three sodium ions out of the cell and two
potassium ions into the cell. This membrane
protein uses the energy from ATP hydrolysis
3.4 Cells can also transport substances by
fusing a portion of the cell membrane.
• Exocytosis is the export from the cell.
• Endocytosis is the import into the cell.
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3.5 Opening Questions: Where did you get
your chromosomes from?
• Human cells contain 46 chromosomes.
• What are at least three things that you
know about chromosomes?
• Can you draw a chromosome?
• What is it made of?
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3.5 Only eukaryotic cells contain organelles
surrounded by membranes.
• The most prominent
membrane-enclosed
organelle is the
nucleus.
• Every eukaryotic cell
(including plant and
animal cells)
contains a nucleus.
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3.5 The nucleus contains most of the cell’s
DNA stored in chromosomes.
• The nucleus, surrounded by an envelope
and containing DNA, directs the activities
of the cell.
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3.5 The nucleus is surrounded by a double
membrane called the nuclear envelope.
• Protein-lined nuclear pores in the nuclear
envelope allow certain molecules, such as
RNA, to pass through.
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3.5 The nucleus houses the chromosomes.
• DNA molecules are wrapped around
proteins to form fibers called chromatin.
• Each very long chromatin fiber twists and
folds to form a chromosome.
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3.5 The nucleus contains a darker area
called a nucleolus.
• The nucleolus is a
particular location
within the nucleus.
• This area produces
ribosomal RNA
(rRNA), an important
component of a
ribosome.
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3.6 Opening Questions: Who’s in charge?
• Think of the cell as analogous to a factory.
However, instead of producing widgets,
the cellular factory produces proteins.
• What roles might the following organelles
play in the cell factory?
– Plasma membrane
– Nucleus
– Ribosomes
– Mitochondria
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3.6 DNA directs a cell’s activities through
the production of proteins.
• DNA in the nucleus
contains the instructions
for making proteins.
• Proteins are very
important molecules in
our cells. They are
involved in virtually all
cell functions.
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DNA
RNA
Protein
Chapter Table of Contents
3.6 Several organelles are involved in
protein manufacture.
Endoplasmic
Reticulum (ER)
Ribosomes
floating or
attached to ER
Golgi Apparatus
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3.6 Protein production involves two steps:
1. Transcription in the nucleus results in the production
of RNA from DNA.
2. Translation at the ribosomes results in the production
of proteins.
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3.6 After transcription, RNA travels from
the nucleus to a ribosome.
• Ribosomes are where proteins are made.
• Some ribosomes are bound to the
membrane of the rough ER.
• Other ribosomes float freely in the
cytoplasm.
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3.6 The endoplasmic reticulum (ER) is filled
with membranes.
• The smooth ER contains enzymes that
produce lipids (such as steroid hormones).
• The rough ER contains ribosomes that
produce many kinds of proteins.
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3.6 Proteins are finalized and packaged in
the Golgi apparatus.
• The Golgi apparatus finishes, sorts, and
ships cell products.
• The Golgi apparatus finishes cell products
in vesicles, small bubbles made of
membrane.
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3.6 Lysosomes are a type of vesicle that
contains digestive enzymes.
• Lysosomes can dissolve large food
molecules, old cellular components, or
invasive organisms such as bacteria.
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3.7 Opening Questions: What if your
organelles went missing?
• What would happen if all the ribosomes in
your cells disappeared?
• What would happen if half of the
mitochondria in your cells disappeared?
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3.7 Two organelles help provide energy for
the cell.
• Chloroplasts are
found in all plant
cells and the cells
of some algae.
• Mitochondria are
found in both plant
and animal cells
(mitochondrion is
singular).
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3.7 Chloroplasts are the organelle of
photosynthesis.
• In photosynthesis, the energy of sunlight
is used to create molecules of sugar.
• Chloroplasts require a
supply of water and
carbon dioxide (CO2).
• The sugars produced
by photosynthesis
provide the energy to
power the cell.
Within a cell, chloroplasts
are visible as green blobs.
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3.7 The chloroplast
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3.7 Mitochondria are the organelle of
cellular respiration.
• Cellular respiration uses oxygen (O2) to
harvest energy from molecules of sugar.
• The harvested energy is stored as
chemical energy in molecules of ATP,
which can then be used to power many
other cellular processes.
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3.7 The mitochondrion
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3.8 Opening Questions: Plant cells vs.
animal cells
• List three structures in the plant cell that
are not found in animal cells.
• For each of these structures, explain why
it is useful for plant cells, but not for animal
cells.
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3.8 Vacuoles function in the general
maintenance of the cell.
• Vacuoles are
intracellular sacs.
• Some are for
storage, such as
for food, nutrients,
or pigments.
• Some pump water
out of a cell.
• Many plant cells have a very large central
vacuole.
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3.8 Some cells have moving appendages.
• Flagella propel the
cell through their
whip-like motion.
• Cilia move in a
coordinated backand-forth motion.
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3.8 Some cells are supported by a rigid cell
wall surrounding the membrane.
• Plant, fungus, and some prokaryotic cells
have a rigid cell wall.
• Plants can stand upright in part because
their rigid cell walls are made of cellulose.
Note: Animal
cells do not have
a cell wall!
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3.8 Animal cells maintain their shape with
an internal cytoskeleton.
• The cytoskeleton is a network of protein
fibers that provides mechanical support,
anchorage, and reinforcement.
The cytoskeleton
network can be
quickly dismantled
and reassembled,
providing flexibility.
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3.8 Animal cells stick together.
• Animal cells produce a sticky
extracellular matrix that helps hold cells
together.
Cells are held
together into a
tissue by the
extracellular
matrix.
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