Ch. 8 Cells & Their Environment

Section 8.1 – Cell Membrane1. 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 bilayer4. The lipid bilayer forms because there is _____ both inside and _____ of the cell. - water- outside5. 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 by7. 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- polar9. 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:

1. Cell membrane

2. Lipid bilayer

3. Hydrophobic

4. Polar

5. Nonpolar

10. What are proteins made of? - amino acids11. 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

4.2.

3. 1.

Use your notes to identify each of the following cell membrane proteins.

Section 8.2 – Cell Transport1. 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

Osmosis7. 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

12. The transport of a substance across the cell membrane against its concentration gradient is called _____ _____.

- active transport13. The energy needed for active transport is usually supplied by _____. - ATP14. What is the sodium-potassium pump? Describe how it works.

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

Active Transport

Endocytosis15. 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

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

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

A. B. C. D.

Section 8.3 – Cell Communication1. What is the main way cells communicate and coordinate activities? - By sending chemical signals2. What is a target cell? - Cells that have specific proteins that recognize and respond to signals.

3. How might neighboring cells communicate? - By direct contact between their cell membranes.

4. What is an environmental signal?

Give an example. - A signal that originates outside of

the body.

- An example of this would be light.

5. Cells are constantly bombarded by signals. How are they able to respond to only the few signals important to their cell function?

- It recognizes and responds to only a few that are important to its function.

6. What is a binding site, and why does it have a specific shape? - A binding site is where a receptor

protein only binds to signals that match the specific shape of its binding site. It has a specific shape so that it only reacts to specific signals.

7. Summarize the three responses cells generally have to a specific signal.

- Permeability change: transport protein may open or close in response to a signal.

- Enzyme activation: enzymes are activated inside the cell which then trigger specific chemical reactions.

- Second messenger: a signal molecule is formed within the cell which then causes changes inside the cell.

8. signal

- d. carries information from one cell or cells to other cells

9. receptor protein

- b. binds to a specific signal molecule,

causing a cell to respond

10. enzyme

- c. speeds up a specific chemical

reaction in the cell

11. second messenger

- a. forms in response to information

from outside a cell and acts as an

information carrier within a cell,

causing changes in the cytoplasm

or the nucleus