Keystone Practice: Open-Ended Questions
General
1. State two safety procedures that should be followed when conducting an experiment that involves
heating protein in a test tube containing water, an acid, and a digestive enzyme.
Chemistry
1. The table below lists enzymes that function in different locations in the human body, and the
temperature and pH ranges of these locations.
Different enzymes are secreted in each of the three locations. Ptyalin digests carbohydrates. Pepsin
and trypsin both digest proteins. Discuss the activity of these enzymes. In your answer, be sure to:
a. state how the activity of pepsin will most likely change after it moves with the food from the
stomach to the small intestine
b. support your answer using data from the table
c. state how a fever of 40ºC would most likely affect the activity of these enzymes and support
your answer
d. identify the characteristic of enzymes that prevents ptyalin and trypsin from digesting the
same type of food
2. When an apple is cut open, the inside soon turns brown. This is because enzymes that are released
from the cut cells react with certain molecules in the apple. Rubbing lemon juice (which contains
citric acid) on the cut apple prevents it from browning. Explain why this is so.
3. Fresh pineapple contains an enzyme that digests proteins. Adding fresh pineapple to gelatin (a
protein) prevents it from setting or jelling. Adding cooked or canned pineapple does not have this
effect and the gelatin can set normally. Explain why these different effects occur.
4. The human stomach contains an enzyme called pepsin, which actively breaks down (digests) protein
molecules found in food. Based on your knowledge of biology, answer the following:
a. At what temperature would you expect pepsin to work best? Give a reason.
b. At what pH would you expect pepsin to work best? Give a reason.
c. Why would drinking very cold beverages have a negative effect on digestion of food in the
stomach?
Cells & Cell Transport
1. Identify a specific structure in a single-celled organism. State how that structure is involved in the
survival of the organism.
2. Arrow A in the diagram above represents active transport. State two ways that active transport is
different from diffusion.
3. Select one lettered organelle from the diagram above and write the letter of that organelle and identify
it. Give the function of the organelle you selected.
4. Identify one process that is carried out in cell Y that is not carried out in cell X.
Photosynthesis & Respiration
1. The diagram above represents a cell found in some complex organisms. The enlarged section
represents an organelle, labeled X, found in this cell. Describe the function of organelle X and
explain how it is important to the survival of the cell. In your answer, be sure to:
a. identify organelle X
b. state the process that this organelle performs
c. identify the two raw materials that are needed for this process to occur
d. identify one molecule produced by this organelle and explain why it is important to the
organism
Mitosis & Meiosis
1. Compare asexual reproduction to sexual reproduction. In your comparison, be sure to include:
a. which type of reproduction results in offspring that are usually genetically identical to the
previous generation and explain why this occurs
b. One other way these methods of reproduction differ
DNA
1. Describe how structures 1 and 2 interact in the process of protein synthesis.
2. Choose either structure 3 or structure 4, state which structure you chose, and describe how it aids the
process of protein synthesis.
3. Read the following scenario and use it to answer questions a-c.
a. State two reasons that a gardener might choose to grow this new variety of plant.
b. State one possible disadvantage of the synthesis of insecticide by potatoes.
c. Explain why every cell in the New Leaf Superior potato plant is able to produce its own
insecticide.
Evolution
1. Although paramecia (single-celled organisms) usually reproduce asexually, some have developed a
method by which they exchange genetic material with each other in a simple form of sexual
reproduction. State one advantage this simple form of sexual reproduction would provide over asexual
reproduction for the survival of these organisms.
2. A hawk has a genetic trait that gives it much better eyesight than other hawks of the same species in
the same area. Explain how this could lead to evolutionary change within this species of hawk over a
long period of time. In your answer, be sure to include an explanation of:
a. competition within the hawk population
b. survival of various individuals in the population
c. how the frequency of the better-eyesight trait would be expected to change over time within
the population
d. what would most likely happen to the hawks having the better-eyesight trait if they also had
unusually weak wing muscles
Ecology
1. The temperature of the environment in which alligator embryos develop influences the sex of
embryos. At higher temperatures, more embryos develop into males while at lower temperatures,
more develop into females. What effect might global warming have on the ability of these alligators
to survive as a species?
2. State one biological benefit of preserving endangered species. Also, give one way that an endangered
species might be saved.
Use the following food web to answer questions 3 & 4.
3.
4.
5.
6.
7.
8.
A rapid decrease in the frog population results in a change in the hawk population. State how the hawk
population may change. Support your answer.
Identify one cell structure found in a producer in this meadow system that is not found in the
carnivores.
The United States government does not allow travelers from foreign countries to bring plants, fruits,
vegetables, animals, or other living organisms into this country. State one biological reason for keeping
these out of the United States.
Due to the negative effects on the environment of burning coal and oil, society is looking for alternate
energy sources that are renewable. Identify one renewable resource that can be used to generate
energy. State one benefit, other than the fact that it is renewable, of using this resource.
In many investigations, both in the laboratory and in natural environments, the pH of substances is
measured. Explain why pH is important to living things. In your explanation be sure to:
a. Identify one example of a life process of an organism that could be affected by a pH change
b. state one environmental problem that is directly related to pH
c. identify one possible cause of this environmental problem
Read the following scenario:
Cargo ships traveling to the Great Lakes from the Caspian Sea in Eurasia often carry water in
tanks known as ballast tanks. This water helps the ships to be more stable while crossing the ocean.
Upon arrival in the Great Lakes, this water is pumped out of the ships. Often this water contains
species that are not native to the Great Lakes environment. The zebra mussel is one species that was
introduced into the Great Lakes in this way.
Although large numbers of zebra mussels often clog water intake pipes of power plants and other
industries, the mussels have a benefit. Each mussel filters about a quart of water per day, absorbing
cancer causing PCB's from lake water in the process.
The goby, a bottom-feeding fish from Europe, was introduced into the Great Lakes in a similar
way a few years later. The gobies have become a dominant species in the Great Lakes, eating small
zebra mussels and the eggs and young of other fish. Gobies are eaten by large sport fish. These sport
fish have been tested and PCB's have been found in their tissues. Recommendations have been made
that people limit the number of sport fish they eat.
Explain how the introduction of foreign species can often cause environmental problems. In your
answer be sure to:
a. state how the zebra mussels and gobies were introduced into the United States
b. state one way either the zebra mussels or gobies have become a problem in their new
environment
c. describe how both zebra mussels and gobies contribute to increasing the concentration of
PCB's in sport fish