Chapters 8 & 5 Test Review

Chapter 8

1. Distinguish between the following pairs of terms: catabolic and anabolic pathways; kinetic and potential energy; open and closed systems; exergonic and endergonic reactions

   Catabolic and Anabolic Pathways: Catabolic pathways release energy by breaking more complex molecules down into small molecules (cellular respiration, glucose breaking down in the presence of oxygen), while anabolic pathways consume energy to build more complex molecules from simpler ones (protein synthesis).

   Kinetic and Potential Energy: Kinetic energy is energy in motion, whilst potential energy is given by location.

   Open and Closed Systems: Open systems take and give energy to surroundings (an organism) while closed systems are isolated from their surroundings (a thermos).

   Exergonic and Endergonic Reactions: Exergonic reactions release free energy and are spontaneous and an endergonic reaction absorbs free energy from surroundings and is nonspontaneous.

2. In your own words, explain the Second Law of Thermodynamics and explain why it is not violated by living organisms

   The Second Law of Thermodynamics says that energy transfer and transformations always result in increased universal disorder, but this isn’t violated by the evolution of living organisms, because even though entropy decreases with evolution, the universe’s total entropy still increases.

3. Explain in general terms how cells obtain the energy to do cellular work

   Cells obtain energy via ATP through phosphorylation, where a phosphate group is added another molecule, and enzymes that pairs the release of ATP energy with cellular work.

4. Explain how ATP performs cellular work

   ATP is used as a cellular energy shuttle, and it mediates energy coupling by using an exergonic process to drive an endergonic one.

5. Explain why an investment of activation energy is necessary to initiate a spontaneous reaction

   Activation energy is inversely related to reaction spontaneity, so as necessary activation energy is lowered, reaction spontaneity increases. The transition state is also unstable, so they proceed to the next step of the reaction as quickly as possible.

6. Describe the mechanisms by which enzymes lower activation energy

   Enzyme-substrate complexes lower activation energy by facilitating bond breaking to move it over to a transition state more quickly.

7. Describe how allosteric regulators may inhibit or stimulate the activity of an enzyme

   Allosteric regulation occurs when a regulatory molecule binds to a protein at one site and affects the protein’s functions at another site. Activators stabilize the active form and stimulate activity, while inhibitors stabilize the inactive form and inhibit activity.

Chapter 5

1. List and describe the four major classes of molecules

   Carbohydrates: Include sugars and polymers of sugars; the simplest carbohydrates are monosaccharides and the macromolecules are polysaccharides. Covalent bonds between monosaccharides are called glycosidic linkages, and they create disaccharides. Polysaccharides have storage and structural roles, and starch and glycogen are storage polysaccharides in plants and animals. Structural polysaccharides include cellulose and chitin.

   Lipids: Lipids are hydrophobic and nonpolar, and they are primarily made of hydorcarbons. Fats are constructed

2. Describe the formation of a glycosidic linkage and distinguish between monosaccharides, dissaccharides, and polysaccharides.

3. Distinguish between saturated and unsaturated fats and between cis and trans fat molecules

4. Describe the four levels of protein structure

5. Distinguish between the following pairs: pyrimidine and purine, nucleotide and nucleoside, ribose and deoxyribose, and the 5 end and 3 end of a nucleotide.