KEY CONCEPT Cells are the Basic unit of life.
Transcript of KEY CONCEPT Cells are the Basic unit of life.
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3.1 Cell Theory
KEY CONCEPT Cells are the Basic unit of life.
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3.1 Cell Theory
The cell theory grew out of the work of many scientists
and improvements in the microscope.
• Many scientists contributed to the cell theory.
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3.1 Cell Theory
Early studies led to the development of the cell theory.
• The Cell theory has three principles.
–All organisms are made of cells.
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3.1 Cell Theory
Early studies led to the development of the cell theory.
• The Cell theory has three principles.
–All organisms are made of cells.
–All existing cells are produced by other living cells.
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3.1 Cell Theory
Early studies led to the development of the cell theory.
• The Cell theory has three principles.
–All organisms are made of cells.
–All existing cells are produced by other living cells.
– The cell is the most basic unit of life.
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3.1 Cell Theory
Prokaryotic cells lack a nucleus and most internal
structures of eukaryotic cells.
• All cells share certain characteristics.
–Cells tend to be microscopic.
–All cells are enclosed
by a membrane.
–All cells are filled with
cytoplasm.
Bacterium
(colored SEM; magnification 8800x)
cell membrane
cytoplasm
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3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Eukaryotic cells have a
nucleus.
• Prokaryotic cells do
not have membrane-
bound organelles.
nucleus
cell membrane
organelles
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3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Prokaryotic cells do not
have a nucleus.
• Prokaryotic cells do not
have membrane-bound
organelles.
nucleus
cell membrane
organelles
cytoplasm
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3.2 Cell Organelles
KEY CONCEPT Eukaryotic cells share many similarities.
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3.2 Cell Organelles
Cells have an internal structure.
• The cytoskeleton has many functions.
– supports and shapes cell
– helps position and transport organelles
– provides strength
– assists in cell division
– aids in cell movement
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3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
• The nucleus stores genetic information.
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3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
• The nucleus stores genetic information.
• Many processes occur in the endoplasmic reticulum.
• There are two types of endoplasmic reticulum.
– rough endoplasmic
reticulum
– smooth endoplasmic
reticulum
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3.2 Cell Organelles
Several organelles are involved in making and
processing proteins. (continued)
• Ribosomes link amino acids to form proteins.
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3.2 Cell Organelles
Several organelles are involved in making and
processing proteins. (continued)
• Ribosomes link amino acids to form proteins.
• Vesicles are membrane-bound sacs that hold materials.
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3.2 Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
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3.2 Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
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3.2 Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
• Lysosomes contain enzymes to digest material.
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3.2 Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
• Lysosomes contain enzymes to digest material.
• Centrioles are tubes found in the centrosomes.
–Centrioles help divide
DNA.
–Centrioles form cilia and
flagella.
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3.2 Cell Organelles
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
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3.2 Cell Organelles
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
• Chloroplasts convert solar energy to chemical energy.
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3.3 Cell Membrane
KEY CONCEPT The cell membrane is a barrier that
separates a cell from the external environment.
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3.3 Cell Membrane
cell membrane
Cell membranes are composed of two phospholipid
layers.
• The cell membrane is made of a phospholipid bilayer.
• There are other molecules embedded in the membrane.
• The fluid mosaic model describes the membrane.
protein
cholesterol
proteincarbohydrate
chain
protein channel
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3.3 Cell Membrane
Cell membranes are composed of two phospholipid
layers.
• The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
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3.3 Cell Membrane
Chemical signals are transmitted across the cell
membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
– intracellular receptor
–membrane receptor
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KEY CONCEPT Materials move across membranes
because of concentration differences.
3.4 Diffusion and Osmosis
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Passive transport does not require energy input from a
cell.
• Molecules can move across the cell membrane
through passive transport.
• There are two types of
passive transport.
• osmosis
• diffusion
3.4 Diffusion and Osmosis
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Diffusion and osmosis are types of passive
transport.
• Molecules diffuse down a
concentration gradient.
3.4 Diffusion and Osmosis
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Diffusion and osmosis are types of passive
transport.
• Osmosis is the diffusion of water molecules across a
semipermeable membrane.
3.4 Diffusion and Osmosis
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Diffusion and osmosis are types of passive transport.
• There are three types of solutions.
• isotonic
3.4 Diffusion and Osmosis
• hypotonic
• hypertonic
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Some molecules can only diffuse through transport
proteins.
• Some molecules cannot easily diffuse across the cell
membrane.
• Facilitated diffusion is
diffusion through transport
proteins.
3.4 Diffusion and Osmosis
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KEY CONCEPT Cells use energy to transport materials
that cannot diffuse across a membrane.
3.5 Active Transport, Endocytosis, and Exocytosis
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Active transport requires energy input from a cell
and enables a cell to move a substance against its
concentration gradient.
• Passive transport requires no energy from the cell.
• Active transport is
powered by chemical
energy (ATP).
3.5 Active Transport, Endocytosis, and Exocytosis
• Cells use active transport
to maintain homeostasis.
• Active transport occurs
through transport protein
pumps.
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A cell can import and export large materials or large
amounts of material in vesicles during the
processes of endocytosis and exocytosis.
• Cells use energy to transport material in vesicles.
• Endocytosis is the process of
taking material into the cell.
3.5 Active Transport, Endocytosis, and Exocytosis
• Phagocytosis is a type of
endocytosis.
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A cell can import and export large materials or large
amounts of material in vesicles during the
processes of endocytosis and exocytosis.
• Cells use energy to transport material in vesicles.
• Exocytosis is the process of
expelling material from the
cell.
3.5 Active Transport, Endocytosis, and Exocytosis