1. All cells have a plasma membrane. This outermost, double-layered membrane separates a cell’s interior from its surroundings. The plasma membrane is selectively permeable. Plant, fungal, eubacterial, algal and archaebacterial cells also have a cell wall, which helps to give the cell its structure, and protect it from osmotic pressure. Animal cells, and most protists don’t have a cell wall.

2. microfilaments and

3. Nucleus Nuclear envelope, nucleoplasm, nucleolus, chromosome, chromatin Endoplasmic Reticulum Golgi Bodies Lysosomes, peroxisomes Vesicles Mitochondria Plastids Chloroplasts Central Vacuole Ribosomes Movement of cells: Cilia Flagella Psuedopodia Also, know the parts of the cytoskeleton: microtubules and microfilaments

4. All cells contain cytoplasm, an organized internal region where energy conversions, protein synthesis, movements of cell parts, and other required activities proceed. Eukaryotic cells contain DNA within a membrane-bound nucleus. Prokaryotic cells contain DNA, but no nucleus. Instead, prokaryotes contain a region within called a nucleoid where the genetic material can be found.

5. Abiogenesis, or the origins of life, is now more precisely known as spontaneous generation. Before the microscope, it was believed that living organisms were generated by decaying organic substances. According to Aristotle it was a readily observable that aphids arise from the dew which falls on plants fleas from putrid matter mice from dirty hay crocodiles from rotting logs at the bottom of bodies of water

6. The first step was taken by the Italian Francesco Redi, who, in 1668, proved that no maggots appeared in meat when flies were prevented from laying eggs.

7. Robert Hooke used a compound light microscope to study cork…the dead cells of oak bark. German scientist Matthias Schleiden observed plant tissues under a microscope, and came to the conclusion that all plants were composed of cells. Theodor Schwann observed animal tissues under the microscope and came up with a similar conclusion. Because of the work of each of these scientists, the fundamental ideas of the cell theory were formulated. They are as follows:

8. 1. All organisms are composed of one or more cells.

9. 2. The cell is the basic unit of structure and organization of organisms.

10. 3. All cells come from preexisting cells.

11. Up to now, the microscopes we’ve discussed use combinations of lenses, and light to magnify objects. At most, these compound light microscopes can magnify things about 1500x. In the 1930s and 1940s, a new kind of microscope was invented that could actually get a look inside the cell. Instead of using beams of light, it used beams of electrons. We could now see things magnified up to 500,000x! S.E.M. T.E.M. S.T.M. Anton van Leeuwenhoek 1600s

12. The transmission electron microscope (TEM) is used to study structures contained within a cell The scanning electron (SEM) microscope is generally used to study the surfaces of cells to learn their three-dimensional shape. The newest “scanning tunneling microscope (STM) uses the flow of electrons to create computer images of atoms on the surface of molecules! Copper metal, with manganese structures about 1-10 atoms long

13. All cellular membranes are made primarily of phospholipids, organized as a double layer. This lipid bilayer gives cells protection against the haphazard movement of water, and water-soluble substances. Phosphate Lipid Lipid tails are hydrophobic Phosphate heads are hydrophilic The structure of the plasma membrane is sometimes referred to as the fluid mosaic model. This “fluidity is achieved with the help of the cholesterol molecules within.

14. Receptor proteins within the plasma membrane receive chemical signals that trigger changes in cell activities. The endocrine system is linked to the plasma membrane through the work of hormones. Recognition proteins help identify a cell as being of a certain type. Transport proteins are also within the plasma membrane and channels through which water soluble substances can cross.

15. Adhesion proteins help cells of the same type Communication proteins form channels that match up across the plasma membranes of two cells, and allow signals and substances to flow rapidly between their cytoplasm. In some instances (cardiac tissue), this channel forms a gap- junction between cells so that electrical signals can flow quickly and all cells can contract together as a functional unit. locate, stick together, and remain in the proper tissues

16. There are many ways in which a material can pass through the cell membrane. One such method is simple diffusion.diffusion Diffusion is simply the movement of particles (molecules) from a region of higher concentration to a region of lower concentration.

17. Another way that molecules can move through a membrane is through osmosis. Osmosis is simply the diffusion of water molecules across a selectively permeable membrane The plasma membrane is responsible for maintaining homeostasis within the cell by allowing water in when the cell needs water and allowing water out, when it doesn’t The movement of water is influenced largely by the presence or absence of dissolved solute in solution, or the concentration gradient.

18. solute selectively permeable membrane

19. Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave the cells. Some substances such as water, oxygen, and carbon dioxide, can cross the cell membrane without any input of energy by the cell. The movement of such substances across the membrane is known as Passive Transport

20. A cell can also move particles from a region of lower concentration to a region of higher concentration if it needs to, but it must extend energy to do so.  Movement of materials through a membrane against a concentration gradient is called active transport and requires energy output from the cell.  Endocytosis  Exocytosis

21. Passive Transporters: movement requiring no energy output by the cell. Examples: Vacuoles in plant and animal cells; nerve and muscle cells with sodium, calcium, potassium, and chloride ion channels. Active Transporters: movement requiring energy output by the cell. Examples: Movement of particles against the concentration gradient, like the calcium “pump” which helps keep the concentration of calcium inside a cell at least a thousand times lower than it is outside a cell.

22. Isotonic solutions occur when the concentration of dissolved substances in the solution outside the cell is the same as the concentration of dissolved substances inside the cell. Osmosis still occurs, but water flows into and out of the cell at the same rate.

23. In a hypotonic solution, the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell. Osmosis will occur, and water will flow into the cell, sometimes until the cell bursts. What type of pressure is increasing in this plant cell? Turgor Pressure

24. When cells are placed in a hypertonic solution, one which contains more dissolved particles than are within the cell, water will flow out of the cell. Due to osmosis, cells will shrivel up and shrink as they lose water. Is the turgor pressure low or high in this plant cell?

25. In animal cells, the direction of osmosis (in or out of the cell) depends upon the concentration of solutes inside and outside the plasma membrane. In plant cells, however, osmosis is also influenced by turgor pressure, the pressure of the cell wall exerted on the contents of the cell. To account for the differences in both concentration and pressure, a more general term, water potential, is used to describe the tendency of water to move across a selectively permeable membrane. Water potential is the sum of the pressure potential (like from the cell wall), and the osmotic pressure (from solute concentration). The elastic cell wall of plants exerts a back pressure, which will limit the net gain of water. Ψ = Ψp + Ψ π Water Potential Pressure Potential Osmotic Potential

26. Water moves across a selectively permeable membrane from an area of higher water potential to an area of lower water potential. Water potential can be positive or negative. Negative water potential is called tension. The addition of solutes to water lowers its potential (makes it more negative), just as the increase in pressure increases its potential (makes it more positive). If possible, water will move from an area of higher water potential to an area that has a lower water potential Osmotic potential results from the presence of solutes and is always negative. The higher the concentration of solutes, the smaller (or more negative) the osmotic potential. Pressure potential is zero, unless some force is applied…such as that applied by a cell wall. Pure water at atmospheric pressure has a water potential of zero (pressure potential = 0, and osmotic potential = 0). Water potential is measured in bars (1 bar is approximately equal to 1 atmosphere pressure)

27. Steepness of concentration gradient Molecular size Temperature Electric or pressure gradients present More molecules will move out of a region of higher concentration than a region of lower concentration. Smaller molecules move faster than larger molecules When the net movement of molecules remains nearly uniform in two adjoining regions, it is known as dynamic equilibrium. Heat energy causes molecules to move faster than in colder adjoining regions Dissolved ions can create a potential difference where positive ions are attracted to negative areas, and pressure can also cause a gradient “pushing” molecules from one region to another