Download 3-1 Cells are the Basic unit of life

3-1 Cells are the Basic unit of life.
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.
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.
–**Applies to ALL cells
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.
There are two cell types: eukaryotic cells and prokaryotic cells.
•Eukaryotic cells have a nucleus.
•Prokaryotic cells do not have membrane-bound organelles. (bacteria ONLY)
3-2 Eukaryotic cells share many similarities.
Cells have an internal structure.
The cytoskeleton has many functions.
–Made up of microtubules and microfilaments
–supports and shapes cell
–helps position and transport organelles
–provides strength
–assists in cell division
–aids in cell movement
Several organelles are involved in making and processing proteins.
The nucleus stores genetic information and controls cells activities.
Many processes occur in the endoplasmic reticulum. There are two types of
endoplasmic reticulum.
–rough endoplasmic reticulum (involved in protein synthesis)
–smooth endoplasmic reticulum (involved in lipid synthesis)
Several organelles are involved in making and processing proteins.
Ribosomes link amino acids to form proteins following coded instructions
from the nucleus.
Vesicles are membrane-bound sacs that hold materials.
Other organelles have various functions.
•Mitochondria uses energy from food to make high energy compounds the cell can
use to power growth, development, and movement.
•Golgi
apparatus has enzymes that attach carbohydrates and lipids to proteins, and
send them to their final destination (transport).
•Vacuoles are fluid-filled sacs that hold materials such as water, salts, pigments, etc.
•Lysosomes contain enzymes to digest lipids, carbohydrates, and proteins into
particles that can be used by the cell.
•Centrioles are formed from microtubules in animal cells. They are important in cell
division.
–Centrioles help divide DNA.
–Centrioles form cilia and flagella.
Plant cells have cell walls and chloroplasts.
•A cell wall provides rigid support and protection for plant cells and bacteria.
•Chloroplasts convert solar energy to chemical energy.
3-3 The cell membrane is a barrier that separates a cell from the external
environment.
Cell membranes are composed of two phospholipid layers. They form a thin,
flexible barrier around the cell (all cells).
The cell membrane has two major functions.
–forms a boundary between inside and outside of the cell
–controls passage of materials (what enters and leaves the cell)
•There are other molecules embedded in the membrane.
•The fluid mosaic model describes the membrane.
•The cell membrane is selectively permeable.(some substances can pass across the
cell membrane while others cannot)
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
3-4 Materials move across membranes because of concentration differences.
The cell takes in water and food and eliminates wastes through the membrane.
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.
• diffusion
• osmosis
• facilitate diffusion
Diffusion and osmosis are types of passive transport. (do not require energy)
Diffusion occurs because molecules constantly move and collide with each other.
Diffusion is movement of molecules from areas of high concentration to areas of low
concentration.
** Molecules will diffuse across until concentration on both side of the membrane are
the same, then the molecules will move across the membrane in both directions.
This is called equilibrium.
Osmosis is the diffusion of water across a selectively permeable membrane.
Water diffuses from a region of HIGH water concentration to a region of LOW water
concentration. Water molecules will continue to move until equilibrium is reached.
There are three types of solutions that vary according to the concentration of water
and solute dissolved in them.
 Isotonic – solutions are the same strength inside and outside, so there
is NO net movement of water
 Hypertonic – solution outside the membrane has a higher
concentration of solute than inside, so water moves OUT.
 Hypotonic – solution outside the membrane has a lower concentration
of solute than inside, so water moves IN.
**Plant cells and bacteria have a cell wall to protect the cells from water moving into
the cells (osmotic pressure). Other cells have contractile vacuoles to pump excess
water out of the cell.
Some molecules can only diffuse through transport proteins.
• Some molecules cannot easily diffuse across the cell membrane.
Facilitated diffusion is diffusion through transport proteins. Net movement will
still only occur from high concentration to low concentration.
3-5 Cells use energy to transport materials that cannot diffuse across a
membrane.
Active transport requires energy input from a cell and enables a cell to move a
substance against its concentration gradient. (low to high concentration)
• 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.
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 by means of
enfoldings in the cell membrane.
 Phagocytosis is a type of endocytosis where large particles are taken
into the cell.
Cells use energy to transport material in vesicles
• Exocytosis is the process of expelling material from the cell.