Practice Exam: Introductory Biology & Inorganic Chemistry KEY

Practice Exam: Introductory Biology & Inorganic Chemistry KEY Honors Biology

1. What is the current definition of life?

Life is very hard to describe, but the definition most used by modern scientist is “a self-sustained chemical system capable of undergoing Darwinian evolution.”

2. What are some benefits and drawbacks of asexual and sexual reproduction?

Asexual reproduction is very fast, only requires one parental life form, and produces identical offspring that may be very well suited to the environment. However, a drawback of asexual reproduction may be the identical offspring, which may not have the diversity needed to survive evolutionary stresses. Sexual reproduction produces unique offspring, giving the species a better chance of surviving in a changing environment. However, it is also slow and requires two parents of opposite mating type.

3. Elementary school students are often taught that the source of all energy on the Earth is ultimately the sun, because phototrophs use the sun as an energy source, and heterotrophs use plants as an energy source. This concept is completely wrong. Explain.

The idea that life on Earth depends on the sun does not take into account chemosynthetic organisms. These life forms do not need the sun; they burn sugar for energy, but are able to make the sugar and

other raw materials from CO2 from the seawater and the energy of chemical reactions. These types of life can survive in the deepest parts of the ocean, where sunlight never penetrates.

4. Differentiate between a prokaryote and a eukaryote.

Prokaryotic cells are the most common type on Earth. They are cells with no nuclei and no membrane bound organelles (like ER, Golgi bodies, etc.). Examples are bacteria and archaea. Eukaryotic cells are typically much larger and have a nucleus to hold their DNA.

5. Below is the description of an experiment:

A team of researchers is studying the effectiveness of a drug to treat heart attacks. Patients that arrive at the hospital emergency department on Monday, Wednesday, and Friday get the new drug. Patients that arrive on Tuesday, Thursday, and Saturday get the old drug. [Don’t ask about Sunday—this day usually screws up studies like this.] The physicians then look at how well the patients survive from the two different treatments.

a. What is the hypothesis being tested?

The hypothesis is whether the new drug is better than the old drug.

b. What is the variable?

Which drug the patients get is the variable. c. What is the control the variable is being tested against?

The new drug is being compared against the control group composed of patients getting the current drug and treatment.

d. What are some of the factors that must be standardized?

Both groups of patients are treated by the same doctors at the same hospital. Both groups get equally sick patients; each group gets people from the same geographic region.

e. Why the complicated system of the different weekdays of arrival being used to assign patients into the different group?

So the doctors don’t get to pick and choose which patients go where; they can’t purposely or accidentally skew the experiment.

6. List the SI units for the following.

Length meter Mass kilogram Volume liter Temperature Kelvin or °C

7. Perform the following conversions:

137 mm → μm 29 L → kL 813 μg → cg

137 mm • 1 000 000 μm = 137 000 μm 29 L • 1 kL = 0.029 kL 813 μg • __100 cg = .0813cg 1 000 mm 1000 L 1 000 000 μg 8. Draw the structure of the magnesium atom, including all particles in the nucleus and the electron cloud. Give the valence electrons.

Nucleus Electron cloud 12 protons in the nucleus 12 e-, 2 valance e- 12 neutrons in the nucleus

a. What charge would the ion have? Loses two electrons, so +2.

9. Complete this chart.

Element Symbol Protons Neutrons Electrons Neon Ne 10 10 10 Sulfur S 16 16 16 Cadmium Cd 48 64 48

10. Oxygen comes in two forms: Oxygen-16 and Oxygen-18. These two atoms are examples of what?

Same atoms, different weights are examples of isotopes. They would have the same number of protons but differ in neutrons, and thus have a different weight.

[N.B.-the number after the atom’s name is the atomic mass.] 11. Ions are very important to biology. What is an ion?

Ions are atoms that have either lost or gained electrons. They have an overall electrical charge because the protons and electrons no longer cancel each other out. Ions can form electrostatic, or ionic attractions, between oppositely charged ions.

12. Hydrogen-1 and hydrogen-2 are isotopes, but hydrogen-1 is stable whereas hydrogen-2 is radioactive. Define radioactivity. Why is radioactivity important to biology?

A radioactive molecule has too many protons and/or neutrons in its nucleus, making it unstable. To become stable, the atom will either destroy particles in the nucleus—releasing energy—or eject protons and neutrons directly from the nucleus to become smaller. As the atom throws out part of its nucleus, it changes from one element to another. Radioactive elements are used in biological experiments, but are better known for the damage that the energy or particles ejected from the nucleus cause to proteins and DNA in the cell.

13. Water tends to climb up a paper towel when you dip a corner into a puddle. Ethanol, the alcohol you drink, does not. What must be the difference between the two?

Water has polar bonds. This allows hydrogen bonds to form between different water molecules, creating cohesion. One side effect of cohesion is the phenomenon of capillary action.

Alcohol does not have very polar bonds and thus does not form strong hydrogen bonds, and as a result does not have capillary action.

14. If water didn’t behave the unusual way it does, life would have died as soon as it formed, and we would not be here. Explain.

Due to the polarity of water, when it freezes solid the ice floats on the surface of liquid water. This (1) prevents solid blocks of ice from horribly crushing the denizens of the sea, and (2) insulates the body of water and prevents it from freezing sold.

15. Define pH. Describe an acid and a base. Sketch the pH scale, labeling neutral, acidic, and basic regions.

pH is the measure of the amount of hydrogen ions (also called protons, or H+) in a solution. Solutions with high levels of H+ are acids, and those with low H+ (and often high levels of another ion called hydroxide, or OH-) are bases. pH is measured on a never-ending scale centered at 7 (which is neutral). And solution with a pH value below 7 is acidic, and above seven basic. The further away from seven, the stronger the solution is. In addition, each value on the pH scale is logarithmic, meaning that it is 10 times stronger than the previous value (i.e., a pH of 5 if 10 times stronger than a pH of 6).