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Midterm 1 Answer Key:
Note: Scroll down for the answers to the questions.
Questions:
1. Which of these is a correct representation of the hierarchical organization of life from least to most complex? (2 points)
a) hydrogen, water, nucleus, heart muscle cell, heart, heart muscle tissue, human
b) hydrogen, water, nucleus, heart muscle cell, heart muscle tissue, heart, human
c) nucleus, hydrogen, water, heart muscle cell, heart, heart muscle tissue, human
d) water, hydrogen, nucleus, heart muscle cell, heart muscle tissue, heart, human
e) hydrogen, water, heart muscle cell, nucleus, heart muscle tissue, heart, human
2. According to scientists, what is the smallest level of organization that is considered to be "alive"? (2 points)
3. List four characteristics that are considered to be attributes of living things. (4 points)
4. What scientific idea/belief did the experiments of Louis Pasteur disprove/refute with his experiments using meat broth ? (2 points)
5. Why is it important to include a control group when conducting an experiment? (2 points)
6. Argon (Ar) has an atomic number of 18 and is an unreactive element, whereas potassium (K), which has an atomic number of 19, is very reactive. What is the reason for this difference in reactivity between these two elements? (2 points)
7. Isotopes are identical atoms that differ in their number of: (2 points)
a) protons.
b) electrons.
c) neutrons.
d) proteins.
e) mitochondria.
Match the following answer choices with the next 3 questions and write the correct letter in the space provided.
(2 points each)
A. nonpolar covalent bond
B. polar covalent bond
C. ionic bond
D. hydrogen bond
E. hydrophobic interaction
8. Which of the above results from a transfer of electron(s) between atoms?
9. Which of the above results from an unequal sharing of electrons between atoms?
10. Which of the above explains the reason why water molecules are attracted to one another?
11. How does the presence of water affect the orientation of the molecules that make up the phospholipid bilayer of cell membranes? (Note: your answer should include a discussion of hydrophilic/hydrophobic molecules)
(4 points)
12. Circle the choice that correctly completes the following statement:
Hyrophobic / hydrophilic molecules can pass easily (without assistance) through the plasma membrane. (2 points)
13. Water takes a large amount of energy to raise or lower its temperature compared to other molecules; this is because: (2 points)
a) it can dissolve large quantities of solutes.
b) it has a strong surface tension.
c) it is more dense when liquid than when frozen.
d) it has a high specific heat.
e) cells are composed mostly of water.
14. a) Explain why water has surface tension. (3 points)
b) Provide one biological example of how an organism can make use of the surface tension of water in its survival. (2 points)
15. What property of water is essential for the survival of aquatic organisms that live in lakes where winters are very cold and lakes freeze over for long periods of time? (3 points)
16. Explain the function of each of the following complex carbohydrates in living organisms. (8
points)
a) chitin
b) cellulose
c) glycogen
d) starch
17. What are the monomer molecules that make up proteins? (2 points)
18. You go the store and buy some lard as well as vegetable oil for cooking. You notice when you get home that the lard is solid at room temperature whereas the vegetable oil is liquid.
a) What type of fat is the lard? (1 point)
b) What type of fat is vegetable oil? (1 point)
c) What causes the difference in composition (solid vs. liquid) in the two types of fats? (3 points)
19. Which of the following solutions has the greatest concentration of hydrogen ions [H+]? (2 points)
a) lemon juice (pH 2)
b) ammonia (pH 11.5)
c) water (pH 7)
d) soda (pH 3)
e) coffee (pH 5)
20. What is the source/cause of acid rain and why is it considered to be an environmental problem? (Note: you do not need to include chemical formulas for any of the compounds; a descriptive answer is adequate) (4 points)
21. List two structures that are found in plant cells, but NOT in animal cells. (4 points)
22. A biologist ground up some plant cells and then centrifuged the mixture. She obtained some organelles from the sediment in the test tube. The organelles took up
CO2 and gave off O2. These organelles are most likely ___________________________________. (2 points)
23. Ribosomes are manufactured in a special region of the eukaryotic cell called the _____________________________________. (2 points)
24. List two characteristics/structures that eukaryotic cells have but that prokaryotic cells do not. (4 points)
25. List the three different types of structures that make up the cytoskeleton in cells and explain one function of each of them. (6 points)
26. Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through:
(2 points)
a) nuclear pores.
b) gap junctions.
c) plasmodesmata.
d) the glycocalyx.
e) tight junctions.
27. Explain two of the functions of cell membrane proteins (integral and/or peripheral proteins). (4 points)
28. You go on vacation for two weeks and when you get home your favorite plant is drooped over in its planter. Remembering your biology, you immediately water your plant, and it perks back up. Explain why a lack of water caused the plant to droop, and why watering restored it. (3 points)
29. Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are: (2 points)
a) hypertonic to both fresh water and the salt solution.
b) hypotonic to both fresh water and the salt solution.
c) isotonic with fresh water but hypotonic to the salt solution.
d) hypotonic to fresh water but hypertonic to the salt solution.
e) hypertonic to fresh water but hypotonic to the salt solution.
30. What are the two major differences between active transport and passive transport (diffusion)? Give a specific example of each type of transport that occurs within a eukaryotic cell. (6 points)
31. Explain the difference between: (6 points)
a) pinocytosis
b) receptor-mediated endocytosis
c) phagocytosis
32. Bonus Question 1:
What is the difference in function of ribosomes that are attached to the endoplasmic reticulum with those that are free (not attached to the ER)? (2 points)
33. Bonus Question 2:
Which of the following elements would form covalent bonds rather than ionic bonds? Explain the reason behind your answer. (Note: the number associated with each element is the atomic number) (3 points)Lithium (Li3), Magnesiun (Mg12), Silicon (Si14), and Helium (He2)
Answers:
1. Answer: b
2. Answer: cells
3. Answer:
can assimilate and use energy
can respond to their environment
can maintain a relatively constant internal environment
possess inherited information can reproduce
are composed of one or more cells
evolved from other living things
highly organized compared to inanimate objects
4. Answer: spontaneous generation
5. Answer: Without a control group, there is no basis for knowing if a particular result is due to the variable being tested or to some other factor.
6. Answer: The outer shell of argon is filled with 8 electrons and is stable, whereas potassium has 1 electron in its outer shell, and needs to get rid of it to become stable.
7. Answer: c
8. Answer: C
9. Answer: B
10. Answer: D
11. Answer: The phopholipids are made up of a hydrophilic head and hydrophobic tail. The presence of water in cells orients the molecules such that the hydrophobic tails are isolated in the center of the membrane.
12. Answer: hydrophobic
13. Answer: d
14. Answer:
a) The cohesion property of water (attraction of water molecules to each other) causes water molecules at the surface of a body of water to be
attracted sideways and down, but not up, thus forming a relatively stable and strong layer of water
molecules.
b) Small organisms such as water striders can travel across the water without sinking and drowning.
15. Answer: Ice is less dense than liquid water, so when water starts to freeze, it forms an insulating layer on the lake surface and the water below does not freeze, thereby allowing the animals to survive.
16. Answer:
a) chitin - provides structural support in insects
b) cellulose - provides structural support in plants
c) glycogen - form of carbohydrate storage in animals
d) starch - form of carbohydrate storage in animal
17. Answer: amino acids
18. Answer:
a) saturated fat
b) unsaturated fat
c) Lard is made up of saturated fats that stack up when cool, therefore, forming solids. Unsaturated fats have kinks that prevent them from stacking so they remain liquid at room temperature.
19. Answer: a
20. Answer: Acid rain is caused by pollutants such as SO2 and NO2 that are released from industrial sources and that combine with water vapor to form sulfuric and nitric acid in the atmosphere. These compounds rain down from the cloud cover and reduce the pH of the environment where they land, disrupting the plants' and animals' biological processes.
21. Answer: cell wall, chloroplast (plastid) and central vacuole
22. Answer: chloroplasts
23. Answer: nucleolus
24. Answer: internal compartmentalization, membrane-bound organelles, presence
of a nucleus
25. Answer:
Microfilaments - function in changes in cell shape and rapid movement of
cells.
Intermediate filaments - function as the anchor for organelles in the cell (the
skeleton).
Microtubules - function in cell movement (flagella), movement of particles across the cell surface (cilia) and movement of vesicles within the cell.
26. Answer: b
27. Answer: They provide structural support when attached to the cytoskeleton, they play a role in cell recognition, communication though molecules like hormones, and serve as channels through which materials can pass through.
28. Answer: When the plant was not watered, the plant cells lost water due to osmosis and therefore lose turgor pressure. Watering the plant allowed the cells to regain turgor pressure by osmosis.
29. Answer: e
30. Answer:
Active transport: requires energy and moves materials against their concentration
gradient.
Example: sodium-potassium pump
Passive transport (diffusion): does not require energy and moves materials down their concentration gradient (from greater to lesser
concentration).
Example: movement of oxygen, carbon dioxide, glucose
31. Answer:
a) pinocytosis - "cell drinking", the plasma membrane encloses the material to be brought into the cell and pinches off into a
vesicle.
b) receptor-mediated endocytosis - receptors bind to molecules, converge in a depression on the membrane, and the pit pinches off into a
vesicle.
c) phagocytosis - food particles or whole cells are brought into the cell through pseudopodia, or "false feet", that surround the material and form a vesicle around it.
32. Answer: ER-ribosomes manufacture proteins that are destined for the cell
membrane or that will be transported outside of the cell. Free ribosomes manufacture proteins that will be used within the cell.
33. Answer: Silicon - because it has 4 electrons in its outer shell and it will share electrons with other elements because it doesn't have an extremely high or low
electronegativity.
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