Midterm Case

1. You are the biologist in a group of scientists who have traveled to a distant star system and landed on a planet. You see an astounding array of shapes and forms. You have three days to take samples of living things before returning to earth. How do you decide what is alive?

I would look to see if anything on this planet possesses any of the properties of life. I would try to determine if anything had a cellular organization by taking samples and looking under a microscope to see if there were any thin membranes covering tiny compartments of cells. Next I would look for evidence of metabolism. Metabolism will be easier to identify because it deals with energy such as sunlight and waste excreted from unused energy. There may also be possibly evidence of homeostasis on the planet. All living things maintain a stable internal condition so that their complex processes can be better coordinated. This stable internal condition is called homeostasis. An example of this would be the human body that maintains a temperature of 98.6 degrees. The last two properties of life are growth and reproduction and heredity. Growth and reproduction are the increase in size of a cell or simply the splitting of two cells for reproduction. Heredity is the transmission of characteristics from parent to offspring that contains DNA in every cell. In the three day timeframe on this planet you may not have an opportunity to witness growth, reproduction, or evidence of heredity so I would not use these properties of life in making my determination.

2. What happens if an atom of an element gains or loses electrons? What happens if an atom of an element gains or loses neutrons? What happens if an atom of an element gains or loses protons?

Atoms in which the number of electrons does not equal the number of protons because they have lost one or more electrons are called ions (Johnson, 2010, p. 34). Johnson (2010) tells us "atoms that have the same number protons but different numbers of neutrons are called isotopes" (p. 34). An atom of an element that gains or loses neutrons changes it's mass so it can weigh a little more, or a little less, than the average weight. An atom of an element that gains or loses protons is no longer that element. It has become the element just to the right or to the left of it on the periodic table of the elements. The number of protons in the nucleus of an atom is called the atomic number. An example of this would be carbon with six protons and an atomic number of six. If carbon was to gain a proton it would then become nitrogen which has seven protons and is atomic number seven.

3. The molecule directly above is a peptide made from monomers of amino acids. The molecule below is a disaccharide made from monomers of simple sugars. Both molecules were synthesized suing a common chemical reaction. What is the chemical reaction that formed these molecules and what is the common by-product of both these reactions?

The chemical reaction that formed these molecules is called dehydration synthesis. Dehydration synthesis is when biological molecules are formed by linking subunits with a covalent bond in dehydration synthesis during which two hydrogen's and one oxygen are removed in formation of a bond, so the common by-product of both these reactions is water.

4. Compare the cellular organelles and other structures to the parts of a city. For example, the nucleus is city hall and the DNA is all the city's laws and instructions.

The nucleus of a cell is where most of genetic material