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Biology 1

Fall Semester Examination Review

 

ANSWER KEY

 

 

 

1.        What is the difference between inference and observation?

 

        An inference is a logical interpretation based on prior knowledge or experience.

        An observation involves using the senses to gather information.

        Inferences can be supported by observations.

 

2.        How would one determine whether something was living or nonliving?

 

Anything lacking one or more of the following characteristics of life is nonliving:

        Made up of cells

        Reproduces

        Based on a universal genetic code

        Grows and develops

        Obtains and uses materials and energy

        Responds to its environment

        Maintains a stable internal environment

        Taken as a group, changes over time\

 

3.        What are the fur groups of organic compounds found in living things?

 

The four groups are: carbohydrates, lipids, nucleic acids, and proteins

 

4.        Compare enzyme activity to a lock and key.

 

In a comparison of the activity of enzymes to a lock and key, the lock symbolizes the active site of the enzyme and the key symbolizes the substrate. A specific key can fit into a specific lock; so, too, does a specific substrate fit into the active site of a specific enzyme. Without a prefect match, the reaction cannot occur. Likewise, without the right key, the lock cannot open.

 

5.        How do prokaryotes and eukaryotes differ?

 

Prokaryotes are generally simpler and smaller than eukaryotes, whereas eukaryotes have a nucleus and other specialized organelles.

 

6.        A hypertonic salt solution has a higher concentration of solutes than a blood cell. Explain what happens when a blood cell is placed in a hypertonic salt solution.

 

When a blood cell is placed in a hypertonic solution, the water flows from the blood cell, through the cell membrane, into the solution. As a result of losing water, the cell shrinks.

 

7.        Summarize three statements from the cell theory. Explain the significance of the cell theory to biology.

 

The cell theory states that all living things are composed of cells. It also says that cells are the basic units of life and new cells come from preexisting cells. The cell theory is significant to biology because all living things are made of cells. Differences in the structure and function of different life forms are reflected in differences in their cell structures.

 

8.        Discuss the relationship between autotrophs and heterotrophs. Do heterotrophs depend on autotrophs for their survival? Explain your answer.

 

Heterotrophs depend on autotrophs to obtain energy from the sun. This energy is then passed on to heterotrophs in form of food. Without autotrophs, the sunís energy would not be available to heterotrophs and heterotrophs would eventually die out or find a new way of obtaining energy.

 

9.        Identify three factors that affect the rate of photosynthesis, and explain the effect of each.

 

Three of the factors that affect the rate of photosynthesis are light intensity, temperature, and water. The rate of photosynthesis increases with light intensity up to a certain point, then levels off. Photosynthesis slows at extreme temperatures and usually has an optimal temperature for each kind of plant. Lack of water slows down photosynthesis.

 

10.     Trace the events that occur in the thylakoid membrane during the light-dependent reactions.

 

Electrons in the pigments in photosystem II absorb energy from light. These electrons then move through the electron transport chain to photosystem I. H+ ions move from the stroma into the inner thylakoid membrane. NADP+ becomes NADPH. The charge difference on either side to the thylakoid membrane provides the energy to make ATP via ATP synthase.

 

11.     List the main events of glycolysis. How many ATP molecules are produced and consumed by glycolysis? What effect does the presence of oxygen have on the events that follow glycolysis?

 

Glycolysis is the breakdown of glucose into two molecules of pyruvic acid, producing 4 ATP molecules. An initial input of 2 ATP molecules is required to start glycolysis; thus, there is a net gain of 2 ATP molecules. This process produces high-energy electrons, which are passed to AND+ forming 2 NADH. If oxygen is present, glycolysis leads to the Krebs cycle and the electron transport chain. If oxygen is not present, glycolysis is followed by the rest of fermentation.

 

12.     Compare lactic acid fermentation with alcoholic fermentation. Where does each process occur? What are the products of each process?

 

Both main types of fermentation release energy from food molecules by producing ATP in the absence of oxygen via glycolysis. Alcoholic fermentation occurs in yeasts and a few other microorganisms, and its products are alcohol, CO2, and NAD+. Lactic acid fermentation occurs in muscle cells and some unicellular organism, and its products are lactic acid and NAD+.

 

13.     What kinds of problems does growth cause for cells? How does cell division help a cell solve these problems?

 

As a cell grows, it functions less efficiently because it places more demands on its DNA and it is less able to move materials to their proper destinations quickly. Cell division results in two daughter cells. Each cell has its own copy of the parent cellís DNA and has a size that allows it to efficiently exchange materials.

 

14.     List and describe the main events of the cell cycle. Illustrate your description with a diagram of the cell cycle.

 

During the G1 phase, the cell grows; during the S phase, the DNA replicates; during the G2 phase, the cell prepares for mitosis. The M phase or cell division includes mitosis and cytokinesis. Figures should approximate Figure 10-4 on page 245 of the textbook.

 

15.     Explain why short plants reappeared in Mendelís F2 generation of pea plants.

 

When the heterozygous tall F1 plants produces gametes, their dominant allele for tallness segregated from their recessive allele for shortness. As a result, some of their gametes had the dominant allele, while others had the recessive allele. When the F1 plants self-pollinated, some male gametes with the recessive allele fused with female gametes with the recessive allele during fertilization. The offspring that resulted, which were part of the F2 generation, had two alleles for shortness and were therefore short.

 

16.     The stages of meiosis are classified into two divisions: meiosis I and meiosis II. Compare and contrast these two divisions.

 

Both meiosis I and meiosis II contain a prophase, metaphase, anaphase, and telophase. However, chromosome replicate prior toe meiosis I but not prior to meiosis II. Also, during meiosis I, tetrads form and align along the center of the cell. Then, the homologous chromosomes are separated and two haploid daughter cells form. During meiosis II, sister chromatids align along the center of the cell and are then separated. Four haploid daughter cells form.

 

17.     Heterozygous male guinea pigs with black, rough hair (BbRr) are crossed with heterozygous female guinea pigs with black, rough hair (BbRr). In guinea pigs, the recessive gene b is for white hair, and the recessive gene r is for smooth hair. What are the genotypes and phenotypes of the offspring resulting from this cross?

 

B = Black hair†††††††††††† R = rough hair

b = white hair†††††††††††††† r = smooth hair

 

 

BR

Br

bR

br

BR

BBRR

BBRr

BbRR

BbRr

Br

BBRr

BBrr

BbRr

Bbrr

bR

BbRR

BbRr

BbRR

BbRr

br

BbRr

Bbrr

bbRr

bbrr

 

9 black, rough hair

3 black, smooth hair

3 white, rough hair

1 white, smooth hair

 

18.     Red (R) is incompletely dominant to white (r) in snapdragons. The heterozygous genotype produces a pink snapdragon. If a red snapdragon (RR) is crossed with a white snapdragon (rr), what will be the genotypes and phenotypes of the F1 and the F2 offspring?

 

RR = red, Rr = pink, and rr = white

 

†††††††††††††††††††††††† F1 RR x rr

 

 

r

r

4/4 = pink

R

Rr

Rr

R

Rr

Rr

 

 

†††††††††††††††††††††††† F2 Rr x Rr

 

 

R

r

ľ = red

Ĺ = pink

ľ = white

R

RR

Rr

r

Rr

rr

 

19.     Describe the structure of a DNA molecule.

 

A DNA molecule ahs the shape of a double helix, or that of a twisted ladder. Each strand of the helix is a chain of nucleotides. Each nucleotide is made up of a deoxyribose sugar, a phosphate group, and a nitrogenous base. The two strands are held together by hydrogen bonds between the nitrogenous bases of the nucleotides on opposite strands. The nitrogenous bases form hydrogen bonds with each other in pairs. Adenine forms hydrogen bonds with thymine, and guanine forms hydrogen bonds with cytosine.

 

20.     Contrast the functions of the three main types of RNA.

 

Messenger RNA carries copies of instruction for assembling proteins from DNA to the ribosomes. Ribosomal RNA is component of the ribosomes. Transfer RNA carries amino acids to the ribosomes for assembly into proteins.