Dr. Reichler’s Bio 301L 9:30-11:00am Print Name:________________KEY_________

In-class Exam #1 25 Sept. 2001

Answer each question as succinctly as possible in the space provided. You may use the back if you need more space. If you use a drawing as part of your answer, be sure to also include a written explanation. Each question is worth 3 pts, unless otherwise noted, for a total of 100 points possible for this exam. Read each question carefully, and don’t hesitate to ask if a question seems unclear.
  1. a. If you want to understand what happens to human cells to make them insensitive to insulin, would you use primarily a reductionist or wholistic approach? Why?

Reductionist. The question is about events at the molecular or cellular level. Looking at the smallest components will give answers to this question.
  1. As we discussed in class, science is a human endeavor. How does the use of Strong Inference reduce the chance that human bias will effect scientific results? Be specific in your answer by explaining what part or parts of Strong Inference reduce bias. (4pts)

By having multiple hypotheses, we can not become attached to just one. Also by eliminating hypotheses, we are less likely to be led astray by positive, but incorrect results.
  1. a. If potassium has 19 protons, how many electrons does it have?

19

b. If potassium forms an ionic bond with chloride to make the salt KCl, and if this makes the potassium positive and the chloride negative, how many electrons does the potassium have now?

18
  1. If you drop the KCl into water it will disassociate, but carbon dioxide (CO2) in water will not disassociate. Why?

KCl is held together by ionic bonds that can be interrupted by the + and - charges. CO2 is covalently bonded, and will not disassociate when put near other charges.

 

 

Dr. Reichler’s Bio 301L 9:30-11:00am In-class Exam #1 25 Sept. 2001 Name:_____________KEY________

3. a. Describe what happens to an individual water molecule that causes it to be polar.

The electron sharing in the covalent bond is unequal, so the electrons are closer to the oxygen more time than they are close to the hydrogen. Thus the O has an overall - charge and the H a + charege. Because these + and - charge are unequally distributed, the water molecule is polar.
  1. There are some proteins that are soluble in water while others are not soluble in water. What could be one difference between these kinds of proteins that would determine if they are soluble or not? (4pts)

    2. A soluble protein is likely made of mostly polar AA'a, while a non-soluble protein is made of non-polar AA's.
  2. Why is the characteristic that ice (solid water) floats critical to the existence of life on earth?

As water freezes it rises leaving liquid water below where organisms can survive during cold temp's.
  1. Liquid water (H2O) disassociates into H (hydrogen) and OH (hydroxide).
  1. Is this disassociation a chemical or physical change? Explain.

    2. Chemical. Covalent bonds are being broken.
  2. Pure water has a pH of 7. At the molecular level what is happening if the solution becomes more acidic (pH below 7)?

There are more H+ than OH-.
  1. a. Phosphate (P) has 15 protons. Radioactive Phosphate-32 has 17 neutrons. Describe what happens during radioactive decay in phosphate? (4pts)

One neutron breaks into a proton and electron. The electron leaves the molecule, and the proton remains so now the element has changed to one with 16 protons.

 

Dr. Reichler’s Bio 301L 9:30-11:00am In-class Exam #1 25 Sept. 2001 Name:________ KEY ____________

The half-life of phosphate-32 is about 14 days, and the half-life of calcium-45 is 165 days

  1. If equal amounts of each radioactive element are present, which will be emitting more radioactivity? Explain.

    2. 32P, it is less stable and therefore releasing more radioactivity more quickly.
  2. Which one will take longer to cease emitting radioactivity? Explain.

45Ca, it is more stable, and will continue to emit radioactivity slower and therefore longer.
  1. a. Water plays an important role in how radioactive elements harm living organisms. How does this take place? (4pts)

When beta-particles enter a cell, it commonly hits a water molecule, breaking the water molecule apart. This releases a single O molecule, called activated O. this is very reactive and will cause improper/unregulated chemical reactions thereby damaging the cell.
  1. Government officials from Travis county have asked you to help solve a problem. Some cave paintings have been discovered in the western part of the county, but there are some doubts as to whether they are authentic or not. You already know that the dyes used to paint them are made from plants. How could you determine whether the paintings are thousands of years old or only a few years old?

By using radioactive dating you can check how much of a radioactive element is left in the dye versus how much should be present, carbon-14 is commonly used. This will tell you how long ago the plant was killed to make the dye.
  1. a. Describe the primary function of: (6pts)

Carbohydrates-Store energy

Nucleic acids (nucleotides)-Store information

Lipids-Serve as barrier/membrane

Dr. Reichler’s Bio 301L 9:30-11:00am In-class Exam #1 25 Sept. 2001 Name:_________ KEY ___________
  1. Carbohydrates, amino acids, and nucleic acids (nucleotides) are all organic molecules. When they are functioning in cells, they have something in common that separates them from the fourth class of organic molecules, lipids. What is it? (2pts)

They are all made of small units that must be covalently bonded together to form a functional unit. Lipids are not covalently bound to each other.
  1. a. Is it easier to separate the two strands of DNA or cut a chain of DNA? Why?

Separating the strands only involves breaking ionic bonds. Cutting a chain means cutting covalent bonds.
  1. What does RNA do in cells?

    2. Transfer the info from DNA to make proteins.
  2. Why is damage to DNA more serious than damage to a protein?

DNA carries the info, and if it is damaged all the proteins made after it will be wrong. Damaged proteins can be remade from the DNA.
  1. a. List and describe three functions for proteins. (6pts)

Any three of:

Signal-sending or receiving information

Transport-moving things in/out of cell or around organism

Enzyme-allow chemical reaction to take place

Structural-support cell or organism
  1. Diabetics have increased levels of sugar in their blood. Additionally, proteins in the blood can cease to function because they unfold. What is causing this unfolding? (4pts)

Sugars are polar, and their increased levels interfere with the ionic bonds that give the protein its 3-D shape, so it unfolds.

 

Dr. Reichler’s Bio 301L 9:30-11:00am In-class Exam #1 25 Sept. 2001 Name:________ KEY ___________
  1. a. Lipids have two distinct parts. What are the characteristics of these two parts, and how do these characteristics aid in the function of lipids? (4pts)

Polar head (hydrophilic), nonpolar tail (hydrophobic). Groups of lipids form a bilayer with the tails to the inside and heads outside. This makes a membrane that excludes water and other polar molecules.
  1. Why do cells need proteins associated with their membranes?

Membranes act as barriers but cells need to move things in and out. So proteins in the membrane act to facilitate and regulate this transport.
  1. a. What are two ways to get sugar into the bloodstream?

By releasing it from cells via glucagon and transport proteins or eating it.
  1. Why is it useless to give someone who has type 2 diabetes (adult onset) an insulin shot?

    2. Their cells are insensitive to insulin, so giving insulin will not help.
  2. What role do nucleic acids (in the form of DNA) play in diabetes?

DNA codes for proteins such as insulin, glucagon, the transporters, etc. Also, problems in the DNA can lead to diabetes.
  1. a. As part of your new job at the Centers for Disease Control (CDC), you have been assigned to study the increasing rate of heart disease over the last 70 in the U.S. Before you start any experiments, your boss would like a brief outline of your plan. Using Strong Inference (the parts before actually doing any experiments), briefly describe your plan for studying this problem. (8pts)

Create multiple hypotheses. Design experiments that ELIMINATE one or more of the hypotheses.