Download Cell theory

3.1
Cell Theory
KEY CONCEPT Cells are the Basic unit of life.
TEKS 3F, 4A
3.1
Cell Theory
TEKS 3F, 4A
The cell theory grew out of the work of many scientists
and improvements in the microscope.
• Many scientists contributed to the cell theory.
First to see
cells (cork
cells) in
a microscope.
First to see tiny
organisms
moving in
pond water he
placed under
the microscope
1838Concluded all
plants were
made of
cells
1839Concluded all
animals were
made of
cells
1855- New cells can
only be produced
from the division of
existing cells.
This completed the
3rd statement of the
new “Cell Theory” of
life
3.1
Cell Theory
TEKS 3F, 4A
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
TEKS 3F, 4A
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
TEKS 3F, 4A
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
TEKS 3F, 4A
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
TEKS 3F, 4A
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
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
TEKS 3F, 4A
3.1
Cell Theory
3.2
Cell Organelles
TEKS 3F, 4A
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
3.2
Cell Organelles
TEKS 3F, 4A
Several organelles are involved in making and
processing proteins.
• Manufacturing and transport processes occur in the
endoplasmic reticulum.
• There are two types of endoplasmic reticulum.
– rough endoplasmic
reticulum
– smooth endoplasmic
reticulum
3.1
Cell Theory
3.2
Cell Organelles
Several organelles are involved in making and
processing proteins. (continued)
• Ribosomes link amino acids to make proteins.
TEKS 3F, 4A
3.1
Cell Theory
3.2
Cell Organelles
TEKS 3F, 4A
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
(like the newly made proteins).
3.1
Cell Theory
3.2
Cell Organelles
Other organelles have various functions.
• Mitochondria supply energy to the cell.
TEKS 3F, 4A
3.1
Cell Theory
3.2
Cell Organelles
TEKS 3F, 4A
Other organelles have various functions.
• Vacuoles are fluid-filled sacs that hold materials.
• Larger in plants cells to help maintain water pressure.
3.1
Cell Theory
3.2
Cell Organelles
Other organelles have various functions.
• Lysosomes contain enzymes to digest material.
TEKS 3F, 4A
3.1
Cell Theory
3.2
Cell Organelles
TEKS 3F, 4A
Other organelles have various functions.
• Centrioles are tubes found in the centrosomes.
Centrioles help divide
DNA during mitosis.
Centrioles form cilia and
flagella.
3.1
Cell Theory
3.2
Cell Organelles
TEKS 3F, 4A
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.
3.1
Cell Theory
3.2
Cell Organelles
Plant cells have cell walls and chloroplasts.
• A cell wall provides rigid support.
TEKS 3F, 4A
3.1
Cell Theory
3.2
Cell Organelles
TEKS 3F, 4A
Plant cells have cell walls and chloroplasts.
• Chloroplasts convert solar energy to chemical energy
during photosynthesis.
3.1
Cell Theory
3.3
Cell Membrane
KEY CONCEPT The cell membrane is a barrier that
separates a cell from the external environment.
TEKS 3F, 4A
3.1
Cell Theory
3.3
Cell Membrane
TEKS 3F, 4A
Cell membranes are composed of two phospholipid
layers.
water
Hydrophillic
Hydrophobic
water
3.1
Cell Theory
3.3
Cell Membrane
TEKS 3F, 4A
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
3.3
Cell Membrane
TEKS 3F, 4A
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
3.3
Cell Membrane
TEKS 3F, 4A
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
3.3
Cell Membrane
TEKS 3F, 4A
Chemical signals are transmitted across the cell
membrane.
•
•
Receptors bind with ligands (chemical messengers) and change shape.
There are two types of receptors.
– intracellular receptor – lipid-based (testosterone, estrogen)
– membrane receptor – usually proteins
intracellular receptor
membrane receptor
3.1
Cell
3.4
Osmosis
andTheory
Diffusion
TEKS 3F, 4A
Diffusion and Osmosis are types of passive transport.
• Passive transport does not
require energy input from a cell.
• Molecules can move across the
cell membrane through passive
transport.
• Requires a gradient – molecules
move from higher concentrations
to lower concentrations.
• There are two types of passive
transport.
• diffusion
• osmosis
3.1
Cell
3.4
Osmosis
andTheory
Diffusion
Diffusion and osmosis are types of passive
transport.
Diffusion
• Diffusion is when molecules
move down a concentration
gradient.
• Movement is from a region
of higher concentration to a
region of lower
concentration.
• Osmosis is the diffusion of
water molecules across a
semipermeable membrane.
TEKS 3F, 4A
3.1
Cell
3.4
Osmosis
andTheory
Diffusion
TEKS 3F, 4A
The mixture of solutes and solvents
are called solutions.
NOTE: The following terms are based on the
concentration of solute which will then determine the
movement of water.
Hypertonic- “high” levels of solute/Low H20
Hypotonic-”low” levels of solute/high H2O
Isotonic-“equal” levels on both sides of membrane –
”tonic”
3.1
Cell
3.4
Osmosis
andTheory
Diffusion
TEKS 3F, 4A
Fresh water flows
to salt water as rivers
flow to the sea…
3.1
Cell
3.4
Osmosis
andTheory
Diffusion
TEKS 3F, 4A
This is the shrinking of the cell due to water leaving
the cell…
95% water
plasmolysis.
5% solute
93% water
7% solute
This is the bursting of the cell due to water entering
the cell…
cytolysis.
93% water
7% solute
95% water
5% solute
3.1
Cell
3.4
Osmosis
andTheory
Diffusion
Some molecules can only diffuse through
transport proteins.
• Some molecules cannot easily diffuse across the cell
membrane.
• Facilitated diffusion is
diffusion through transport
proteins.
TEKS 3F, 4A
3.1
Theory
3.5
ActiveCell
Transport,
Endocytosis, and Exocytosis
TEKS 3F, 4A
KEY CONCEPT Cells use energy to transport materials
that cannot diffuse across a membrane.
ATP
Cells also use energy to
transport materials against a
concentration gradient!
…from a low concentration
to a higher concentration..
3.1
Theory
3.5
ActiveCell
Transport,
Endocytosis, and Exocytosis
• Passive transport requires
no energy from the cell.
• Active transport is powered
by chemical energy (ATP).
• Active transport occurs
through transport protein
pumps.
• Cells use active transport
to maintain homeostasis.
TEKS 3F, 4A
3.1
Theory
3.5
ActiveCell
Transport,
Endocytosis, and Exocytosis
TEKS 3F, 4A
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.
• Phagocytosis is a type of
endocytosis.
3.1
Theory
3.5
ActiveCell
Transport,
Endocytosis, and Exocytosis
TEKS 3F, 4A
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.