SC 135 - Second Exam 1997

Answer Key

On the line to the left, place the letter of the choice that best answers the question.

A. NOTE: "e" answers are never the correct answer. Five Points Each.

1. In which bond are electrons shared?

____C_____    a. Hydrogen                 b. Ionic                c. Covalent 
                        d. Osmotic                e. Handcuffs for two wired to a battery

                            ...match the term with the definition.

2. Which is an example of spontaneous generation?

____D_____   a. Baby snakes hatching from eggs
                            b. Amebas dividing
                            c. A scar forming where a wound was
                            d. Snails forming from rocks on a stream bottom
                            e. I just know that my paycheck does something like the opposite...

                            ...life from non-living sources.

3. Which chemical process is essential in the digestion (breakdown) of food?

____A_____    a. Hydrolysis             b. Dehydration synthesis            c. Osmosis 
                        d. Ionic bonding                     e. The creation of special sauce

                            ...Hydrolysis is how molecules are broken.

4. When liver cells process glucose, glucose moves from a lower blood concentration 
                                into the higher-concentration cells. This is

____B_____    a. Osmotic pressure             b. Active transport            c. Secretion 
                        d. Passive transport       e. Inconvenient when you're trying for a "sugar high..."

                            ...diffusion goes from high to low concentrations - if the movement is
                                the reverse, it has to be active transport.

5. Which of the following is not a polymer?

____D_____   a. Protein                 b. Nucleic acid                 c. Starch
                            d. Sugar                     e. Eenimer, meenimer, mynimer, mo...

                            ...the only one that's not a long repeating string.

6. An atom is most stable as an ion with a negative one ( ^- ) charge. How many electrons  
                                should it have in its outer orbital?

____C_____   a. 1             b. 8             c. 7             d. 3            e. Oh, that's what it meant.....

                            ...it stabilizes by filling that shell to the full number of 8.

7. Which is best described as a phospholipid bilayer?

____B_____    a. DNA                 b. Cell membrane                c. Cell wall 
                        d. Ribosome                                e. A Twinkie

                            ...match the structure to its features.

8. Steroid hormones belong to which class of organic molecule?

____A_____   a. Lipids                 b. Proteins                 c. Carbohydrates
                            d. Nucleic Acids                     e. Pumped-up molecules

9. The pH of digestive juices in the intestine is between 7.5 and 8.5. Compared with a 
                            neutral pH, the concentration of H⁺ ions should be

____B_____    a. Higher                            b. Lower                        c. Equal 
                        d. There's no way to tell        e. I saw this in the book - guess I should have figured it out...

                            ...moving up the scale (from the neutral number of 7) means less H+.

10. The extremely salty water of the Dead Sea is what sort of solution for almost any 
                                organism that would try to live there?

____B_____      a. Isotonic                     b. Hypertonic                     d. Hypotonic
                                d. Cytotonic                                     e. Gin and tonic

                            ...a solution with more particles and less water.

11. Polydehydrogenase would belong to which class of organic molecule?

____B_____   a. Oils                         b. Enzymes                         c. Starches
                            d. Nucleic Acids          e. No, you're not supposed to recognize the word

                            ...the -ase is the giveaway.

12. When iron (Fe) rusts, it starts as Fe⁺² and becomes Fe⁺³. Rusting is a(n)

____C_____    a. Enzyme reaction             b. Reduction reaction            c. Oxidation reaction 
                        d. Hydrolysis reaction          e. Process I think my brain cells are doing right now

                            ...an electron's been lost (so the charge gets more positive)

13. Which cell element is most involved in cell movement?

____A_____    a. Microtubules                     b. Nucleolus                    c. Vacuoles 
                        d. Microfilaments                            e. Incredibly tiny moving vans

                            ...they drive cilia and flagella (although microfilaments drive pseudopods,
                                so they shouldn't be a choice).

SHORT ANSWER.  

Answer any ten of the following questions for 7 Points Each.
Note: if you answer more than ten, only the first ten will be corrected.

1. Mitochondrial DNA does not "mix & match" every generation. Why not?

        ...it's passed on as a part of the egg cell - no sperm mitochondria are supposed to contribute, and mitochondria reproduce like bacteria.

2. Lipid molecules are constructed from two basic parts. What are these molecule subunits?

        ...glycerol and (3) fatty acids

3. What are plasmids, and where exactly are they found?

        ...bacteria carry these extra copies of various often-used genes.

4. What happens during phagocytosis?

        ...the cell membrane folds up and around materials and takes them in as a vacuole

5. What exactly makes a molecule polar? (Not necessarily bipolar!)

        ...it has partial charges on it.

6. Explain what a codon is.

        ...a 3-base sequence in a gene used to code for a specific amino acid in a protein.

7. Cells are rarely above a certain size. What bad thing happens as a cell increases in size?

        ...its surface can't keep pace with the needs of its interior.

8. By the newest definition, what features must a molecule have to be considered organic?

        ...carbon and hydrogen.

9. For what two different, major reasons do plants produce glucose?

        ...for energy and for structure.

10. RNA and DNA molecules are built differently. Give two differences in the way the molecules are put together.

        ...DNA double-stranded, RNA single.  DNA has Thymine where RNA has Uracil.  Made up of different sugars.

11. The fluid mosaic model describes a cell membrane. Explain:

    In what way is the membrane fluid?   Lipid molecules flow freely around each other.

    In what way is the membrane a mosaic?  Other molecules are embedded in the membrane.

12. Some people think that the cell damage of aging is produced by oxygen radicals.

    What exactly is a radical?  An uncharged, unstable atom.

    Why are they so damaging?  To stabilize, they are highly reactive.

13. Give the common names of the two basic forms of carbohydrates:

Simple:  Sugars

Complex:  Starches.

14. What purpose is served by microvilli?

        ...they increase a cell's surface area.

15. What is a hydration shell?

        ...the layer of water molecules that surrounds dissolved particles.

16. Fill in the blanks: _____DNA_____ molecules in a nucleus are coiled up into

a material called __chromatin__ ; during cell  division  this  material  is  packed

into  individual pieces called __chromosomes_ .

17. What are two basic principles of the cell theory?

        ...All living things are made up of at least one cell.
        ...Cells are the smallest living unit.
        ...Cells only come from pre-existing, related cells.

18. Name two features of both mitochondria and chloroplasts that support the endosymbiont theory.

        ...They are structurally very similar to known types of bacteria.
        ...They still carry some bacterial-type DNA.

19. Which property of water is it when water is "soaked up" by the cellulose of a paper towel?

        ...Adhesion.

Answer any five of the following questions for 13 Points Each.
Note: if you answer more than five, only the first five will be corrected.

1. Name and define three of the four structural levels of proteins.

2. Give a function of any three of the four organelles listed below:

3. Fill in the chart below for cell structures you might see with an electron microscope.  This is a badly written question - some of it is almost impossible to answer correctly.

4. Give the following cell chemical reactions: (include all molecules and energy types)

Photosynthesis:              Carbon       +    Water       ------->      Glucose     +   Oxygen
                                        Dioxide                              Light

5. For cilia and flagella, list three pairs of differences.

6. The atoms in the following molecule are either Carbon (C), Hydrogen (H), Nitrogen (N) or Oxygen (O). Fill in the boxes with the appropriate atom.

7. For proteins and lipids molecules, give three distinctly different uses (functions - don't just list types, tell what they do) for each in a cell.

8. Name three types of adaptations living things use against osmotic pressure. For each, explain how that adaptation keeps osmotic pressure from harming the organisms.

Answer as many as you are able. Wrong answers will not result in points being lost from the main exam.

Why is Earth's atmosphere mostly (almost 3/4) nitrogen? Five Points.

Local lakes "turn over" in the fall and spring. What exactly causes this? Five Points.

Antibody molecules have two functional ends. What, for four points each, does each end do?

Skeletal muscle cells have many nuclei. Contrary to what the book claims, what's the real reason for this? Four Points.

What advantage do organisms get from having multiple chromosomes, and what possible disadvantage can come from multiple chromosomes? Four Points each.

Cilia move new embryos down the fallopian tubes to the uterus. Smokers are more likely to have an embryo stall in the tubes, producing a dangerous tubal pregnancy. Why, exactly? Four Points.

People requiring intravenous fluids are given a saline (salt) solution rather than pure water. Why? Five Points.