DNA Protein Carbohydrates Phospholipids

1. 1. The cell membrane (also known as the plasma membrane) surrounding every cell is composed primarily of ______. • DNA • Protein • Carbohydrates • Phospholipids

2. 2. The phospholipids in the cell membrane are arranged in a bilayer (double layer). How are the phospholipid molecules arranged in this bilayer? • The nonpolar (hydrophobic) ends of the molecules faces inwards • The polar (hydrophilic) ends of the molecules faces inwards • The fatty acid tails of the molecules faces inward • Both A and C • Both B and C

3. Channels through the phospholipid membrane are formed by • Proteins • DNA • Cellulose • Cholesterol

4. 3. The term permeability means • The ability of a substance to bend • The ability of a substance to allow gases or liquids to pass through • The ability of a substance to dissolve • The ability of a substance to exist for a long time with out deteriorating.

5. 4. In diffusion, molecules move from _________________ concentration in a process that __________________ additional energy. • high to low; requires • high to low: does NOT require • low to high; requires • low to high; does NOT require

6. Additional energy is not required, because diffusion occurs due to the random motion of the molecules.

7. 5. A hypotonic solution is one that a • contains a higher concentration of solute particles • contains an equal concentration of solute particles • contains a lower concentration of solute particles. • is at a higher temperature • is at a lower temperature

8. The prefix hypo means below or under. (To remember this, think of the word hypothermia which is when one’s body temperature drops below the normal body temperature.) If the solute (such as salt or sugar) concentration outside is lower than that inside the cell, then the outside environment is hypotonic.

9. The prefix hyper means above or over. If the solute (such as salt or sugar) concentration outside is higher than that inside the cell, then the outside environment is hypertonic.

10. 6. If a cell with a 0.2 M sucrose concentration inside is placed in a solution that has a 0.1 M sucrose concentration, the process of osmosis will occur. In this case, • sucrose will move into the cell • sucrose will move out of the cell • the cell will expand due to water gain • the cell will shrink due to water loss • both A and C • both B and D

11. Sucrose is disaccharide that is too large to move through the selectively permeable cell membrane. (Osmosis occurring means that it is the water moving through the membrane) Hints to understanding the direction of movement of water in osmosis: Remember that in passive transport (diffusion and osmosis) molecules always move from high concentrations to low concentration. However, solution concentrations are given in terms of the solute, but in osmosis it the water that moves through the membrane. To avoid getting confused by this, you can remember that if it has a higher solute concentration it will have a lower concentration of water. Examples: 3% sucrose solution is 97% water 8% sucrose solution is 92% water 3 %sucrose (97% water) 8% salt (92% water)

12. 7. If a cell with a 0.8% salt concentration inside is placed in a 0.9% salt solution, • the cell will shrink due to water loss • salt will move out of the cell • the cell will expand due to water gain • salt will move out of the cell • both A and D • both B and C

13. Salt is an ionic compound that can not move through the nonpolar barrier of the phospholipid membrane (without specialized channels). • In osmosis, water will move in the direction of the higher SOLUTE concentration. Thus hypertonic solutions, such as one high in salt, causes cells to lose water. • Drinking salt water will dehydrate our cells • Plants will wilt in a hypertonic solution.

14. 8. Which kind(s) of solution outside of a cell could cause it to swell and potentially lyse (burst open)? • a hypertonic solution • a hypotonic solution • an isotonic solution • both A and C • both B and C

16. 9. In an isotonic solution • the cell swells • the cell shrinks • there is NO movement of water in or out of the cell • there is no NET movement of water

17. Water is constantly moving and diffusing through a cell membrane. In an isotonic solution, the movement of water into the cell is equal to the movement of water out of the cell. There is a DYNAMIC EQUILIBRIUM.

18. 10. When a substance is secreted from a cell in a process in which a vesicle fuses with the plasma membrane to released to the outside, it is called • endocytosis • exocytosis • osmosis • halitosis

19. 11. O2 is a small, nonpolar molecule and it is present outside the cell in high concentration. It can enterthe cell by • Diffusion through the membrane • Passive transport • Active transport • A and B • A and C

20. 12. Glucose is a larger polar molecule. If it is present outside of the cell in high concentration, it can enter the cell by • Facilitated diffusion through specialized channels • Passive transport • Active transport • A and B • Aand C

21. 13. An amino acid (a large polar molecule) is present outside the cell in low concentration. It can be brought into the cell by • Facilitated diffusion through specialized channels • Passive transport • Active transport • A and B • Aand C

22. D D B B C C A B D B D D C