Download Chapter 3, Section 1

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
The cell theory grew out of the work of many scientists
and improvements in the microscope.
• Many scientists contributed to the cell theory.
• More was learned about cells
as microscopes improved.
• The cell theory is a unifying
concept of biology.
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
cell membrane
by a membrane.
– All cells are filled with
cytoplasm.
cytoplasm
Bacterium
(colored SEM; magnification 8800x)
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Eukaryotic cells have a
nucleus.
nucleus
• Prokaryotic cells do
not have membranebound organelles.
organelles
cell membrane
3.1 Cell Theory
There are two cell types: eukaryotic cells and prokaryotic
cells.
• Prokaryotic cells do not
have a nucleus.
nucleus
• Prokaryotic cells do not
have membrane-bound
organelles.
organelles
cell membrane
cytoplasm
3.1 Cell Theory
KEY CONCEPT Eukaryotic cells share many similarities.
3.1 Cell Theory
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
3.1 Cell Theory
Several organelles are involved in making and
processing proteins.
• The nucleus stores genetic information.
3.1 Cell Theory
Several organelles are involved in making and
processing proteins.
• The nucleus stores genetic information.
• Many processes occur in the endoplasmic reticulum.
3.1 Cell Theory
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.
3.1 Cell Theory
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
3.1 Cell Theory
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
3.1 Cell Theory
Several organelles are involved in making and
processing proteins. (continued)
• Ribosomes link amino acids to form proteins.
3.1 Cell Theory
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.
3.1 Cell Theory
Golgi apparatus – packages and delivers proteins
3.1 Cell Theory
Other organelles have various functions.
• Mitochondria supply energy to the cell.
3.1 Cell Theory
Other organelles have various functions.
• Mitochondria supply energy to the cell.
• Vacuoles are fluid-filled sacs that hold materials.
3.1 Cell Theory
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.
3.1 Cell Theory
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
– Centrioles help divide
DNA during mitosis
3.1 Cell Theory
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
3.1 Cell Theory
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
• Chloroplasts convert solar energy to chemical energy.
3.1 Cell Theory
KEY CONCEPT The cell membrane is a barrier that
separates a cell from the external environment.
3.1 Cell Theory
Cell membranes are composed of two phospholipid
layers.
• The cell membrane has two major functions.
– forms a boundary between inside and outside of the
cell
– controls passage of materials
cell membrane
inside cell
outside cell
3.1 Cell Theory
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.
cell membrane
carbohydrate
chain
cholesterol
protein
protein channel
protein
3.1 Cell Theory
Cell membranes are composed of two phospholipid
layers.
• The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
3.1 Cell Theory
Cell membranes are composed of two phospholipid
layers.
• The cell membrane is selectively permeable.
Some molecules can cross the membrane
while others cannot.
3.1 Cell Theory
What Goes in?
Small, nonpolar molecules pass through lipid layers
Small polar molecules go through proteins
Large molecules moved in vesicles
3.1 Cell Theory
Chemical signals are transmitted across the cell
membrane.
• Receptors bind with ligands and change shape.
• There are two types of receptors.
– intracellular receptor
3.1 Cell Theory
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