Unit 1: Cellular Functions – Review Answers

True/False

1. T

2. F Water is a polar because the ends have slight charges

3. F Osmosis is the diffusion of water across a semi-permeable membrane.

4. T

5. F The cell membrane is made mostly of phospholipids.

6. F Passive transport moves materials along a concentration gradient.

7. T

8. T

9. T

10. F Lysosomes contain digestive enzymes that break down molecules.

11. T

12. F Glycolysis takes place in the cytoplasm.

13. F Aerobic respiration releases energy with the help of oxygen.

14. T

15. T

Multiple Choice

16. C

17. B

18. A

19. A

20. D

21. B

22. Omit

23. C

24. B

25.E

26. D

Short Answers

27. Water is a liquid over a wide temperature range that dissolves most substances, changes temperature gradually, and expands when it changes state to a solid.

28. See modeling sugar lab.

29.

Carbohydrate	Role in Cell
Glycogen	glucose storage in animal cells
Cellulose	Structural material for plant cells.
Amylose (starch)	glucose storage in a plant cell
Glucose	energy for the cell; can be used in respiration

30. The basic structure of a lipid has very few oxygen atoms. Carbohydrates have many oxygen atoms.

31. See text page 13, figure 1.14

32.

Protein	Function
Actin Filament	Structural
Catalase	Enzyme
CCR-5 receptor protein	Membrane transport

33. See text page 15, figure 1.17.

34. The extracellular fluid contains a variable mixture of water and dissolved materials.

35. A concentrations exists when there is a relative difference in concentration of a substance between two regions. Diffusion describes the process of molecular movement to create a balanced concentration and eliminate the gradient.

36. Transport across the cell membrane often involves diffusion. To increase this activity cells must maximize the surface area and remain small. Within the cell, diffusion works slowly over long distances, so again cells tend to remain small.

37. Water can move across the permeable cell wall, but the rigidity creates pressure that helps prevent the cell from bursting in a hypotonic environment.

38. The cell membrane is selectively permeable. Water can diffuse across the membrane by way of passive transport. Sodium ions cannot pass through the membrane because they are highly charged. Special proteins in the membrane can actively pump sodium ions across the membrane. Other substances, such as starch molecules, are too big to cross the membrane and must be broken down by enzymes into glucose molecules.

39. With improved technology scientists have increased resolution to see various new cellular components.

40. In every case the membrane delimits the organelle and controls the passage of materials into and out of the cell. The examples of such organelles are mitochondria, chloroplasts, lysosomes, Golgi bodies, and the nucleus.

Structure	Purpose of the membrane
cell membrane	Defines the edges of the cell and controls the movement of materials in and out of the cell.
mitochondrion	The outer membrane defines the organelle, the inner membrane is the site of aerobic respiration.
lysosome	The membrane separates the lysosomal enzymes from the cytoplasm, where they can be destructive
endoplasmic reticulum	The ER membrane acts as the site where molecule synthesis takes place.
nucleus	The nuclear membrane separates the nucleus from the cytoplasm and controls the movement of materials.

41. This is an animal cell.

A. Golgi body B. cell membrane C. nucleus D. endoplasmic reticulum

These products work together to make a substance to be secreted by the cell C D A B.

42. The DNA code is copied in the nucleus by mRNA, which then leaves and goes to the ribosome.

43. Flat squamous epithelial cells form a thin, continuous covering for the lungs that increases the rate of diffusion for carbon dioxide and oxygen

44. Reusing matter within the cell means that less energy is wasted on transporting matter across the cell membrane.

45. Researchers explore how normal cells function and then look to see how cancerous cells function differently. Finding these differences

can lead to more effectively targeted treatments that have fewer side effects.

46. Some people have T-lymphocyte cells with a defective membrane protein that prevents the AIDS virus from entering the cell.

47. Chemical energy is the energy stored in the bonds between atoms within molecules.

48. In photosynthesis the raw materials of carbon dioxide and water are combined using the energy of sunlight and the presence of chlorophyll to produce glucose and oxygen.

49. Leaves contain the green pigment chlorophyll, which reflects green light but absorbs blue and red light.

50.

Mitochondria	Chloroplasts
Double unit membrane DNA Organelle Infoldings of membrane Energy transformation	Double unit membrane DNA Organelle Infoldings of membrane Energy transformation
Use sugar and oxygen Produce carbon dioxide and water	Produce sugar and oxygen Use carbon dioxide and water

51. Yeast requires warm conditions with plenty of sugar and little or no oxygen.

52. Energy flows from the sun, through living things, and then into the environment. Photosynthesis captures radiant energy and stores it in the food molecule glucose. Respiration releases energy to do work in the cell and create heat, which will then escape into the environment and be unusable.

53. Yes, since glycolysis occurs in the cytoplasm rather than an energy organelle, it is likely a reaction that developed in prokaryotes at a very early time.

54. Naturally occurring bacteria found at toxic sites sometimes have the capacity to metabolize dangerous substances into smaller, safer molecules.

Inquiry

55. If immersed in a sports drink for a period of time, model cells will retain their shape and have the same mass because the sports drink is isotonic. A cell in an isotonic will both gain and lose water with no net change. This can be measured by massing the model before and after the immersion.

56. A) The uncooked egg showed the greatest change in mass. This egg had an undamaged cell membrane, so water

diffuse easily from the hypotonic solution into the egg.

C) Heat damages the cell membrane so that materials cannot pass through.

D) Sample prediction; answers may vary) The egg membrane changes when the temperature is 39°C. Prepare three more eggs and test them by immersing each in temperatures: 38°C, 39°C, and 40°C. Find the mass of each egg. Add each to a beaker of distilled water to soak overnight and measure the mass again to see which gained the least amount of water.

58. A) Sperm cells require the most glucose.

B) Basal skin cells have the lowest energy requirement of the cells investigated