1. Water is able to form hydrogen bonds because

1. 1. Water is able to form hydrogen bonds because • oxygen has a valence of 2. • the water molecule is shaped like a tetrahedron. • the bonds that hold together the atoms in a water molecule are polar covalent bonds. • the oxygen atom in a water molecule has a weak positive charge. • each of the hydrogen atoms in a water molecule is weakly negative in charge. 25

2. 2.What gives rise to the cohesiveness of water molecules? • hydrophobic interactions • nonpolar covalent bonds • ionic bonds • hydrogen bonds • both A and C 25

3. 3.Which of the following statements is true about buffer solutions ? • They maintain a constant pH when bases are added to them but not when acids are added to them. • They maintain a constant pH when acids are added to them but not when bases are added to them. • They maintain a constant pH of exactly 7 in all living cells and biological fluids. • They maintain a relatively constant pH. • They are found only in living systems and biological fluids. 25

4. Which molecule contains an amino functional group, but is not an amino acid? • A • B • C • D • E 25

5. 5. Which of the following is false? • The higher the pH the more H+ ions present • pH affects the charge of molecules • A change in pH can denature proteins • The pH scale is logarithmic • 1 and 4 are false 25

6. C=0Figure 4.4 6. What is the name of the functional group shown in Figure 4.4? • carboxyl • ketone • hydroxyl • carbonyl • aldehyde 25

7. 7. Which of the following statements is false? • As a cell increases in size, its SA increases by the square of the size increase • As a cell increases in size, its volume increases by the cube of the size increase • In a cell, membranes provide its surface area • In a cell, volume refers to the amount of cytoplasm • In a cell, it is most desirable to have a low surface area to volume ratio 25

8. 8. Of the following, which is probably the most common route for membrane flow in the endomembrane system? • vacuole → plasma membrane → nuclear envelope → smooth ER • Golgi → lysosome → ER → plasma membrane • nuclear envelope → lysosome → Golgi → plasma membrane • rough ER → vesicles → Golgi → plasma membrane • ER → chloroplasts → mitochondrion → cell membrane   25

9. 9.Large numbers of ribosomes are present in cells that specialize in producing which of the following molecules? • proteins • glucose • starches • steroids • lipids 25

10. 10.Tay-Sachs disease is a genetic condition called a storage disease that affects this cell organelle • Mitochondria • ER • Golgi • Lysosome • Vacuole 25

11. 11.Which type of organelle is primarily involved in the synthesis of oils, phospholipids, and steroids? • ribosome • lysosome • smooth endoplasmic reticulum • mitochondrion • contractile vacuole 25

12. 12.These cell structures hold cells of tissues subject to mechanical stress (like the uterus) tightly together • peroxisomes • desmosomes • gap junctions • plasmodesmata • tight junctions   25

13. 13.A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from • a bacterium. • an animal, but not a plant. • a plant, but not an animal. • a plant or an animal. • any kind of organism. 25

14. 14.Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells? • glycocalyx • desmosomes • gap junctions • extracellular matrix • tight junctions 25

15. 15.Which of the following is not associated with chloroplasts? • DNA • Photosynthesis • stroma • Respiration • High inner membrane surface area 25

16. 16.We used white blood cells as an example of an important cell type in the body several times when we discussed cell organelles and systems. What roles(s) do white blood cells play in your body? • They are involved in phagocytosis • They destroy invading bacteria and virus • Some white blood cells secrete antibodies • White blood cells patrol your body looking for invaders • All of the above 25

17. 17.If a plant cell is placed in a hypertonic environment • the turgor pressure of the cell will increase; • the cell will swell but won't burst due to the presence of the cell wall; • the environment will have a greater solute concentration than is present inside the cell; • the net movement of water will be inside the cell. 25

18. 18.Receptor mediated endocytosis • is a form of active transport; • is a form of facilitated diffusion; • describes the method by which vacuoles from the ER fuse to the membranes of the Golgi apparatus ; • is a specialized type of exocytosis; • e) is a way to transport specific substances from the environment in to the cell. 25

19. 19.The membrane activity most nearly opposite to exocytosis is • plasmolysis. • osmosis. • facilitated diffusion. • phagocytosis. • active transport.  25

20. 20.The main problem with the Davson-Danielli model of membrane structure was that it: • did not account for the phospholipidbilayer • phospholipid fluidity was impossible • it placed membrane proteins in a layer on the membrane surface • early electron micrographs clearly did not support this model • nothing is wrong with the model, and it is accepted today by cell biologists 25

21. 21.According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids? • They can move laterally along the plane of the membrane. • They frequently flip-flop from one side of the membrane to the other. • They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane. • They are free to depart from the membrane and dissolve in the surrounding solution. • They have hydrophilic tails in the interior of the membrane. 25

22. 22.If a membrane loses fluidiity • It will lose its ability to regulate what enters and leaves the cell • It’s permeability properties will change • It will not be able to bring things into the cell by endocytosis • 2 and 3 • All of the above 25

23. 23.The difference between simple and facilitated diffusion is that: • One goes from high to low concentration and the other goes from low to high • One requires a carrier molecule and the other does not • One requires energy and the other does not • One involves spontaneous movement and the other does not 25

24. 24. The Na+/K+ Atpase pump • Is a membrane protein • Is an enzyme • Has a binding site for phosphate • Depends on conformational changes to pump ions • All of the above 25