Cell theory membrane structure cell transport and important organelles
-
Upload
james-h-workman -
Category
Technology
-
view
5.251 -
download
3
Transcript of Cell theory membrane structure cell transport and important organelles
The cellular level of anatomical organizationAnatomy and Physiology
Brief history of cell theory
Cell membrane structure
Transport into /out of cell
Transport within the cell
Important organelles
Cell Theory:
1. All living things are made of one or more cells
2. Cells are the basic units of structure and function in organisms
3. All cells arise from existing cells
Development of the cell theory:
Robert Hooke in 1663, observed cork (plant): named the cell
Robert Brown observed and named nucleus
Theodor Schwann in 1800’s states: all animals are made of cells
Development of the Cell Theory
Matthias Schleiden in 1800’s states: all plants are made of cells
Louis Pasteur’s work with bacteria ~ 1860 disproved idea of spontaneous generation (living things from nonliving)
Rudolf Virchow observes cells dividing and states all cells come from preexisting cells
A cell is the simplest structural and functional unit of life. There are no smaller subdivisions of a cell or organism that, in themselves, are alive.
An organism’s structure and all of its functions are ultimately due to the activities of its cells.
Importance of Cell Theory
Importance of Cell Theory
Cells come only from preexisting cells, not from nonliving matter. All life, therefore, traces its ancestry to the same original cells.
Because of this common ancestry, the cells of all species have many
fundamental similarities in their chemical composition, and metabolic and
physiological mechanisms.
Why Cells are Small
Small cells are more efficient
Surface area to volume ratio must remain high for materials to easily reach all parts of the cell
Cell Membrane Structure and Transport
Cell Membrane• Defines cell boundaries
• Controls interactions with other cells
• Controls passage of materials in and out of cell (contributes to homeostasis)
• Fluid-Mosaic model
Fluid Mosaic Model of Membranes
Membrane Proteins
Membrane Fluidity
Membrane Permeability• Cell membranes are selectively permeable (semi-permeable)
• Some solutes cross the membrane freely, some cross with assistance, and others do not cross at all.
The diffusion of water molecules through a selectively permeable membraneOsmosis will continue as long as there are more water molecules on one side of the membrane (“osmotic pressure”)
Water will continue to diffuse until there are equal numbers of molecules inside and outside the cell (“osmotic balance”)
Osmosis
60% H2O 90% H2O
Water will move out of to the left across the membrane until osmotic balance has been reached
100% H2O
80% H2O
90% H2O
90% H2O
75% H2O
90% H2O
Water leaves the cell and it shrinks. This is called plasmolysis in plant cells
Facilitated Diffusion
Involves carrier or channel proteins to transport substances that otherwise could not pass the phospholipid bilayer (because of their polarity or charge, like ions)
Active Transport and ATP Powered Pumps
Animal cells contain membrane vesicles called lysosomes, filled with enzymes that can degrade proteins, lipids, nucleic acids, and other biomolecules. These enzymes are most effective at acid pH, and it can be experimentally shown that the pH inside lysosomes is about 5.0, whereas the pH of the cell cytoplasm is close to 7.0. The diagram (at right) illustrates one lysosome inside a cell.
Endocytosis
Exocytosis