Ch. 8 Cells & Their Environment

Section 8.1 – Cell Membrane 1. What is homeostasis, and what is the main way that the cell membrane helps maintain homeostasis? - the maintenance of stable internal conditions in a changing environment. - by controlling the movement of substances across the cell membrane. 2. List three other functions of the cell membrane. Provides structural support to the cytoplasm, recognizes foreign material, communicates with other cells. 3. The _____ _____ is made of a double layer of phospholipids. The double layer of phospholipids is called a(n) _____ _____. - cell membrane - lipid bilayer 4. The lipid bilayer forms because there is _____ both inside and _____ of the cell. - water - outside 5. The phosphate _____ of a phospholipid is polar. It is _____ _____ water. - head - attracted to

6. The long fatty acid _____ of a phospholipid are nonpolar. They are _____ _____ water. tails repelled by 7. The lipid bilayer forms a barrier, preventing most molecules from passing through it. Only molecules that are _____ in size and _____ can pass through the lipid bilayer. small nonpolar 8. Ions, which are _____ particles, and _____ molecules are repelled by the nonpolar interior of the lipid bilayer. charged polar 9. The cell membrane includes various kinds of _____. Some face the inside of the cell. Some face the _____ of the cell. Others span the entire width of the _____ _____. proteins outside cell membrane

Pair-Share Take 3 minutes to explain why water requires a channel to get through the cell membrane. Use the following terms in doing so: Cell membrane Lipid bilayer Hydrophobic Polar Nonpolar

10. What are proteins made of? - amino acids 11. Why do proteins stay within the lipid bilayer of the cell membrane? Nonpolar parts of the protein are attracted to the interior of the lipid bilayer while also repelled by water on either side of the membrane. 12. List the four types of proteins found in a cell membrane. cell-surface markers receptor proteins enzymes transport proteins

13. Cell Surface Marker - identifies the cell type Example: markers on red blood cells that denote blood type

14. Receptor protein recognizes and binds to substances outside the cell, enabling the cell to sense its environment Example: HIV virus infecting human white blood cells

15. Enzyme - helps with chemical reactions inside the cell

16. Transport protein - Helps substances move across the cell membrane

Use your notes to identify each of the following cell membrane proteins. 3. 1. 2. 4.

Section 8.2 – Cell Transport 1. What is the purpose of cell transport? What is the difference between active transport and passive transport? Cell transport is the movement of substances across a cell membrane. Active transport requires energy to move a substance while passive transport does not. 2. What is equilibrium? When a space is filled evenly with molecules or particles. 3. What is diffusion? Why is diffusion an example of passive transport? The movement of substances from an area of high concentration to an area of low concentration, down the concentration gradient.

4. simple diffusion b. small, nonpolar molecules passing directly through the cell membrane 5. facilitated diffusion with channel proteins c. an ion, sugar, or amino acid moving through a specific pore, based on the size and charge of the moving substance 6. facilitated diffusion with carrier proteins a. a substance binds to a protein, which changes shape; both move together across the cell membrane, where the substance is released

Osmosis 7. What is osmosis, and why is it important in cells? - The movement of water across a membrane from an area of high concentration to an area of low concentration. 8. Explain how water moves across a cell membrane. - Water moves through specific channel proteins.

9. water moves into the cell c. The solution a cell is in is hypotonic, meaning that it has a lower solute concentration than the cytoplasm does. 10. a state of ongoing equilibrium occurs b. The solution a cell is in is isotonic, meaning that it has the same solute. concentration as the cytoplasm does 11. water moves out of the cell a. The solution a cell is in is hypertonic, meaning that it has a higher solute concentration than the cytoplasm does

Active Transport 12. The transport of a substance across the cell membrane against its concentration gradient is called _____ _____. - active transport 13. The energy needed for active transport is usually supplied by _____. - ATP 14. What is the sodium-potassium pump? Describe how it works.

Endocytosis 15. Explain why proteins and polysaccharides cannot be transported across a cell membrane by carrier proteins. How do these substances cross the cell membrane? - they are too large, they use vesicles 16. What is endocytosis? Describe how it works. - The cell membrane forms a pouch around the substance to be imported which then pinches off into a vesicle.

Exocytosis 17. What is exocytosis? Describe how it works. - A vesicle containing large molecules fuses with the cell membrane and expels its contents outside of the cell. 18. What are some circumstances in which cells use exocytosis? - Export proteins, release waste, remove bacteria

Label each of the following types of movement across a cell membrane. D. C.