Assignment 2: Chapter 3 Questions

1. How big are bacteria?

Bacteria are between 1 and 10 micrometers in size.

2. How does the size of bacteria compare to the size of viruses?

Viruses are between 10 and 100 nanometers in size. This means that bacteria are roughly 300 times larger than viruses.

3. What is the difference between a simple stain and a differential stain? Which type is gram staining?

A simple stain is the use of a single dye to reveal basic cell shapes and arrangements. A differential stain in the use of two or more stains to distinguish between different types of cells or organisms or to differentiate between different parts of an organism.

4. Why do Gram-positive bacteria retain the purple stain?

The Gram-positive bacteria retain their purple stain because of the thick cells walls, which is due to large amounts of peptidoglycan.

5. What are the differences between gram positive and gram negative bacteria that cause them to stain differently?

The thickness of the cell walls is a large difference between the Gram positive and Gram negative bacteria.

6. What is the difference between Gram-variable and Gram-nonreactive cells?

Gram-variable cells are a mix of purple and pink cells which could be from the broken cells from an old sample (dyes both negative and positive). Gram-nonreactive do not stain because they do not have a cell wall.

7. What can you determine about a cell using the Ziehl-Neelsen Acid Fast Stain?

The Ziehl-Neelsen Acid Fast Stain is used on organisms that are not decolorized by acids in alcohol. A positive result is red, and negative is blue.

8. Compare and contrast negative staining with endospore staining.

Negative staining is the dyeing of the background around the organism, leaving the organism itself clear so that it stands out from the background. Endospore staining is where you are trying to visualize the spores on a bacteria. Both of these samples are difficult to stain and they both need heat in order to accept the stain.

Assignment 2: Chapter 2 Questions

1. What is the difference between an endergonic and an exergonic reaction?

Endergonic Reactions are reactions that absorb energy.

Exergonic Reactions are reactions that give off energy.

2. How many protons, neutrons, electrons, and valence electrons does Na⁺ have? (the atomic number for sodium is 11)

Protons: 11

Neutrons: 11

Electrons: 10

Valence Electrons: 8

3. What is the difference between an ionic bond and a covalent bond? Which is stronger?

Covalent bonds are stronger than ionic bonds. Ionic bonds are the gain or loss of electrons that result in a bond formed between ions (either cations or anions). Covalent bonds are the sharing of atoms.

4. What are the four types of organic macromolecules and which monomers link together to make up each?

Polypeptides (proteins)- made up of amino acids

Polysaccharides (starches)- made up of monosaccharides

Lipids (fats)- made up of fatty acids

Nucleic Acids (DNA and RNA)- chains of amino acids

5. Which type of bond holds together the monomers that make up the four primary organic macromolecules?

Covalent bonds hold together the monomers of the four primary organic macromolecules.

6. Which type of bonds hold together two complementary strands of DNA?

Hydrogen bonds hold together complimentary strands of DNA.

7. Why do phospholipids form micelles in water?

Phospholipids form micelles in water because they have hydrophobic and hydrophilic regions.

8. What is the difference between a saturated and an unsaturated fatty acid?

Saturated fatty acids have the maximum amount of hydrogen atoms possible for each carbon (all single bonds). Unsaturated fatty acids have double bonds and there are not the maximum number of hydrogen atoms on each carbon.

9. Often times science fiction stories make reference to silicon-based life forms as opposed to carbon-based life. Why does this make sense as a plausible possibility for alien life?

Silicon-based life forms are a plausible possibility because it has four valence electrons that allow for the attachment of four possible atoms or molecules, similar to carbon.

10. What are the three differences between DNA and RNA?

The sugars in DNA and RNA are different (DNA has a deoxyribose while RNA has a ribose), DNA forms a double helix and RNA is a single spiral, and DNA uses the thymine base, while RNA uses Uracil.

11. What are the five nitrogenous bases that form the eight nucleotides that make up RNA and DNA?

The purines are Adenine (A) and Guanine (G). The pyrimidines are Cysteine (C), Thymine (T), and Uracil (U).

12. How do nucleotides fit together to form DNA? (draw it!)

The nitrogenous bases pair. Adenine pairs with Guanine in DNA and RNA, Adenine pairs Thymine in DNA and Uracil in RNA. These pairs alternate and build upwards creating a spiral staircase that is bounds by hydrogen bonds.

13. What causes proteins to fold into their final shape?

Quaternary structure causes the proteins to fold into their final shape.

14. What is the difference between a protein’s primary structure, secondary structure, tertiary structure, and quaternary structure?

Primary Structure: the specific sequence of the amino acid in a polypeptide chain.

Secondary Structure: the folding and coiling of amina acids in a particular pattern (alpha helix, beta sheets…)

Tertiary Structure: further folding into globular or fibrous shapes

Quaternary Structure: association of several tertiary structure polypeptide chains.

15. What causes the structural shape of receptors to change?

The binding of a ligand causes the shape of the receptors to change.

16. What would happen if an enzyme were absent from a cell?

The cell would not function, as the enzyme is a catalyst for the chemical reactions of the cell.

17. What would happen if a cell had too much of a particular enzyme?

If there is too much of an enzyme, the cell usually tells it to shut that particular enzyme. As far as cells are concerned, depending on what the enzyme is, it may cause problems or it may not. It really depends on enzyme is present and the effect is has on the cell.

18. Why are enzymes highly specific for their substrates and receptors highly specific for their ligands?

The enzyme’s substrates and receptor binding sites are highly specific because the chemical reactions that are needed to run are highly specific.

19. Based on its name, what do you think proteases do?
    (Hint: these are also called peptidases)

Proteases break down proteins.

Assignment 1: Article Summary #1

I found an article entitled, "Phage Therapy May Reduce Salmonella Infection in Pigs" and it can be found at the URL, http://www.sciencedaily.com/releases/2010/01/100121154341.htm. While no author was given, the article cited the American Society of Microbiology for information.
This article looks at inoculating pigs against salmonella in order to prevent cases in human beings who eat the pork. Salmonella is spread through fecal matter, especially when the pigs are in enclosed areas and the sick are mixed in with the healthy pigs. The use of bacteriophages is interesting, since a good portion of the meats we consume are treated with antibiotics. The problem is that many of these microorganisms have become immune to the antibiotics and are essentially rendered ineffective. This is where bacteriophage is useful for bacteria-caused infections. Instead of antibiotics killing off bacteria, viruses are used to kill these harmful bacterial cells. Studies were completed on young pigs who were infected with salmonella and then inoculated with a "bacteriophage cocktail" and there effectiveness was determined to be between 99.0 and 99.9%. These pigs were then introduced to a variety of environments were they would be likely to pick up the salmonella organism, but never did. This seems to be a step in the right direction as far as protecting our food sources.

Assignment 1: About Me!

My name is Meghann. I have lived in Ventura County, specifically Thousand Oaks, all of my life. I just graduated from California Lutheran University with my bachelor's in chemistry (December of 2009). I am waiting to hear from graduate schools I have applied to (there are a bunch of them) as my aspiration is to become a physician assistant. I am taking several of the other prerequisites I need for graduate school this semester (including physiology, intro to abnormal psychology, statistics, developmental psych, medical terminology in addition to microbiology). I attended Thousand Oaks High School and graduated in June of 2005. I work at Telesis Physical Therapy (during the week) and Agoura Sash and Door (on Saturdays). I also volunteer at St. John's Regional Medical Center and St. John's Pleasant Valley Hospital through an internship called the Clinical Care Extender Program. So as you can see I am quite busy, but usually manage to juggle everything with some success!