key concept cells are the basic unit of life
TRANSCRIPT
3.1 Cell Theory
KEY CONCEPT Cells are the Basic unit of life.
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.
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.
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.
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.
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
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
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
3.2 Cell Organelles
KEY CONCEPT Eukaryotic cells share many similarities.
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
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins.
• The nucleus stores genetic information.
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
3.2 Cell Organelles
Several organelles are involved in making and
processing proteins. (continued)
• Ribosomes link amino acids to form proteins.
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.
3.2 Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
3.2 Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
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.
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.
3.2 Cell Organelles
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
3.2 Cell Organelles
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
• Chloroplasts convert solar energy to chemical energy.
3.3 Cell Membrane
KEY CONCEPT The cell membrane is a barrier that
separates a cell from the external environment.
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
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.
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
KEY CONCEPT Materials move across membranes
because of concentration differences.
3.4 Diffusion and Osmosis
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
Diffusion and osmosis are types of passive
transport.
• Molecules diffuse down a
concentration gradient.
3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive
transport.
• Osmosis is the diffusion of water molecules across a
semipermeable membrane.
3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
• There are three types of solutions.
• isotonic
3.4 Diffusion and Osmosis
• hypotonic
• hypertonic
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
KEY CONCEPT Cells use energy to transport materials
that cannot diffuse across a membrane.
3.5 Active Transport, Endocytosis, and Exocytosis
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.
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.
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