Cellular Levels of Organization and Cellular Transport Notes

1. Cellular Levels of Organization and Cellular Transport Notes

2. Unicellular Organisms • Unicellular organisms that live together in groups called colonies are called “colonial organisms.” • The cells have no relationship to each other and don’t work together. • There is no specialization or differentiation of the cells. A unicellular organism is composed of a single cell. Examples: bacteria, yeast, ameba

3. Multicellular Organisms • A multicellular organism is a group of cells that live and work together in one organism. • There is cellular differentiation and specialization. • Advantage of cellular specialization: • A cell that only has to do one function can be much more efficient at that one job. • Disadvantage of cellular specialization: • The cells are dependent upon one another. If one group of cells fails to do its job, the other cells will perish.

4. Levels of Organization 1. Cells that are differentiated: A cell that becomes specialized for just one function like a nerve cell or a muscle cell A group of similar cells all performing a similar activity. 2. Tissues: 3. Organ: A group of several tissues functioning as a unit and performing the same function. 4. Organs work together to form systems.

5. Structure of the Cell Membrane 1. Phospholipid bilayer 2. Proteins 3. Hydrophobic phospholipid tails 4. Carbohydrates 5. Transport protein 6. Hydrophilic phospholipid head

6. The cell membrane regulates what enters and what leaves the cell. It also provides protection and support to the cell. The membrane consists of a lipid bilayer (double layer) in which proteins are embedded. The lipid bilayer gives the membrane a flexible structure that forms a strong barrier between the inside and the outside of the cell. Many of the proteins form channels and pumps to help move materials across the membrane. The carbohydrates serve as identification markers to help individual cells to identify one another.

7. Homeostasis …. is a balance that organisms maintain through self-regulating adjustments. It requires self-regulation of materials coming into the cell and going out of the cell. The cell is an open system. It requires the constant inflow of matter and energy and the constant out flow of waste.

8. Permeability of the Membrane The cell membrane is called a selectively permeable membrane or a semipermeable membrane. It has the ability to let one substance pass through more readily than others. Some materials are not allowed to enter at all. It can control the speed at which molecules are allowed to enter.

9. Diffusion A. There is a higher concentration of solute molecules on one side of the membrane. B. The solute molecules move from the side of higher concentration to the side of lower concentration. This movement will continue until the concentration is equal on both sides of the membrane. A. B. C. C. Equilibrium has been reached. The concentration is equal on both sides of the membrane. There will still be movement in both directions, but the concentrations will remain equal.

10. Movement across the membrane can be either passive or active. Passive transport means that no energy is being used to move molecules across the membrane. Substances move naturally down their concentration gradients.

11. Types of Passive Transport 1. Diffusion Diffusion is the spreading out of molecules from a region of high concentration to a region of low concentration. 2. Osmosis Osmosis is the movement of water across a membrane from a region of high concentration to a region of low concentration.

12. Types of Passive Transport 3. Facilitated Diffusion Facilitated diffusion speeds the passage of a solute by providing a passage through the membrane. The “passage” is a transport protein that crosses the entire phospholipid bilayer. It does not alter the direction of transport; solutes still move from areas of high concentration to low concentration. Facilitated diffusion is considered passive transport because the solute is moving down its concentration gradient.

13. Small, polar molecules (like water, glucose) have difficulty crossing through the lipid bilayer of the membrane. Transport proteins help these molecules to pass through the membrane more easily. This is known as facilitated diffusion because these proteins “facilitate” or “help” these molecules diffuse across the cell membrane. Polar molecules cross directly through the protein without coming into contact with the lipid bilayer.

14. Movement across the membrane can be either passive or active. Materials must sometimes move against their concentration gradient: meaning the cell must often move materials from an area of low concentration to an area of high concentration. It’s called active transport because the cell must expend energy to accomplish it.

15. Types of Active Transport low 1. Protein Pumps: If small molecules and ions need to be moved across the membrane against the concentration gradient, it will require the use of protein pumps that are embedded in the membrane. This use of protein pumps requires the use of lots of energy in the form of ATP (adenosine triphosphate) that’s made in the mitochondria. ATP high

16. Types of Active Transport 2. Large molecules may have to be transported by a movement of the cell membrane. When the cell membrane brings substances into the cell it’s called endocytosis. When the cell membrane expels substances from the cell it’s called exocytosis. This requires lots of energy in the form of ATP.

17. Types of Active Transport Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. The pocket that results breaks loose from the cell membrane and forms a vacuole within the cytoplasm. Large molecules and clumps of food are taken up in this way. cell membrane food vacuole

18. Two types of endocytosis are: Phagocytosis: the engulfing of large, particulate food particles. The cell membrane forms a pocket, surrounding the food particle & forming a vacuole inside the cell food cell

19. 2. Pinocytosis is known as “cellular drinking”. The cell surrounds and engulfs droplets of extracellular fluid. It is not the fluid that is needed, but the molecules dissolved in the droplets.

20. Exocytosis is the release of large materials from the cell. A vacuole fuses with the cell membrane, forcing the contents out of the cell.