2. The plasma membrane separates the internal and external environments of the cell This description is known as the fluid-mosaic model

4. The lipid bilayer phosopholipid heads are polar, hydrophilic Their phospholipid tails are hydrophobic

5. Proteins in a membrane consist of peripheral & integral proteins Peripheral proteins: Integral proteins:

7. Both Phosopholipids and proteins can have attached carbohydrate chains facing the outside of the cell This combined with peripheral proteins means that the 2 halves of the plasma membrane lipid bilayer are asymmetrically

8. The plasma membrane function differs from cell to cell and the type of integral proteins largely determine the specific function: Channel Proteins: Carrier Proteins: involved in the passage of molecules through membrane

9. Cell Recognition Proteins: glycoproteins that help the body recognize invaders (pathogens) Receptor Proteins: have a shape that allows a specific molecule to bind to it Enzymatic Proteins: carry out metabolic reactions, and without it these necessary reactions would be not occur

10. The plasma membrane is differentially permeable, which is why substances can move across the membrane while others cannot Most molecules move across the membrane due to a concentration gradient that is high on one side of the cell and low on the other

11. Larger molecules and some ions or charged molecules can’t move freely using concentration gradients

12. Diffusion is the movement of molecules from a higher area to lower area of concentration It is a physical process that occurs with any type of molecule and doesn’t require any use of energy

13. The properties of the plasma membrane allow only a few types of molecules to enter and exit the cell this way Several factors influence the rate of diffusion:

14. Osmosis is the diffusion of water across a differentially permeable membrane from an area of high concentration to low Osmotic Pressure is the pressure that develops in a system due to osmosis

15. Isotonic Solution: The solute concentration and water concentration both inside and outside the cell are equal

16. Hypotonic Solution: Can cause the cell to burst Hypo=less than and refers to a solution with a lower concentration of solute If a cell is placed in a hypotonic solution, water would enter the cell Cytolysis is used to refer to a burst cell

17. Hypertonic solution : Hyper=more than and refers to a solution with a higher percentage of solute If a cell is in a hypertonic solution water leaves the cell Plasmolysis is the shrinking of cytoplasm in a plant cell

18. Facilitated transport: the passage of molecules like glucose and amino acids, across the membrane by carrier proteins Active transport : when molecules or ions move through the plasma membrane, when an accumulation occurs

19. Usually chemical energy like ATP is required for the carrier protein to combine with the molecule being transported A sodium-potassium pump is the most common example of these protein pumps

22. Your fingers in water When your fingers are submerged in water they become water logged the massive amount of water out side of your skin moves in causing you skin to expand, leading to wrinkles

23. Improper functioning of Carrier proteins can result in many different types of disorders, most considered genetic Cysteinuria: causes the Cysteine Protein Carrier to malfunction allowing a build up of cysteine in urine and causes it to solidify Other Vitamin carriers have been linked to people who develop breast cancer

24. A malfunctioning Na-K pump can cause a variety of disorders Build ups of Na or Ca ions in cells lead to Chronic Obstructive Lung Disease (COLD)

25. Exocytosis is when a vesicle fuses with the plasma membrane as secretion occurs to the outside of the cell

26. Endocytosis is when cells take in substances by vesicle formation There are Three Types of Endocytosis

27. Pinocytosis occurs when vesicles form around a liquid or very small particles Phagocytosis is when the material taken into the cell by endocytosis is large (like food particles)

28. Receptor Mediated Endocytosis is a form of pinocytosis that uses receptor proteins shaped to a specific molecule

29. Hermansky-Pudlak syndrome Pigment dilution, decreased visual acuity, a bleeding, and lysosomal accumulation that can lead to pulmonary fibrosis Lysomes are made in the cell, serve their function and when are no longer needed are not destroyed, causing a build up of toxins in the cell

30. Cells are small. This is an incredible advantage for multi-cellular organism A larger cell would require more nutrients and produce more wastes than a smaller cell

32. For example a cube shaped cell two units high, wide and depth has a surface area of 24 units and volume of 8 units. A cube cell double the size, 4 units, would have a surface area of 96 units surface area and 64 units volume. The smaller has more surface area per unit of volume allowing for more efficient exchanges of nutrients at the cell surface Most actively metabolizing cells are small. A cell needs a surface area that can adequately exchange materials with its environment and surface area to volume ratios require that cell stay small