Bio Frq

Topics: Protein, Photosynthesis, Metabolism Pages: 5 (1503 words) Published: May 3, 2011
Liuyi Bian
1. The physical structure of a protein often reflects and affects its function.

(a) Describe THREE types of chemical bonds/interactions found in proteins. For each type, describe its role in determining protein structure.
Different types of bonds/interactions in proteins lead to different kinds of structures. Three of the most commonly known chemical bonds in proteins include the hydrogen bond, the covalent bond, and the ionic bond. In hydrogen bonds, hydrogen interacts with oxygen, nitrogen, or fluorine to form either the alpha helix, or the beta sheet, which in turn determines its secondary, tertiary, or quaternary structure. Another type of bonds, the covalent bond, links amino acids together by sharing electrons; this bond is critical to proteins in that it determines the amino acid sequence, and the primary structure of the peptide chain. Lastly, the ionic bond, it is a charged R group that determines whether the protein structure would be tertiary, or quaternary.

(b) Discuss how the structure of a protein affects the function of TWO of the following. • Muscle contraction
• Regulation of enzyme activity
• Cell signaling
Enzymes bind to their substrates at a specific point called the active site. The regulation of enzyme activities mostly involves the inhibition of substrates, and this inhibition is divided into two types. The first type, competitive inhibitor, binds the inhibitors at the active site, blocking the substrates from entering. The second type is the noncompetitive inhibitor where the inhibitor binds to the opposite side of the active site, changing the shape of the enzyme, and stops it from being active.

Cell signaling is also affected by the structure of the protein because in this activity, ligand binds specifically to receptor, causing it to catalyze reactions. If a gap junctions, for instance, is formed, then the shape of the junctions would allow for passages of regulatory ions or molecules, thus regulating the communication between cells.

(c) Abnormal hemoglobin is the identifying characteristic of sickle cell anemia. Explain the genetic basis of the abnormal hemoglobin. Explain why the sickle cell allele is selected for in certain areas of the world.

Abnormal hemoglobin is most likely caused by point mutation in DNA, where the base substitution leads to a different amino acid in the hemoglobin. Sickle cell allele is selected for in certain areas of the world because its condition protects against or resists malaria. It also maintains a reproductive advantage/success.

2. Consumers in aquatic ecosystems depend on producers for nutrition. (a) Explain the difference between gross and net primary productivity
Net primary productivity is part of the gross productivity in that gross include the overall amount of energy obtained from photosynthesis, while net primary productivity only includes the amount of energy or organic molecules left for the next trophic level. Net primary productivity would always be less than gross productivity because it subtracted the amount of energy used by the producers for cell respiration and the energy lost in the forms of heat.

(b) Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period.
Obtain two samples of pond water. Measure the dissolved oxygen content for each one, and then expose light to one sample while no light to the other. After a period of 24 hours, measure the dissolved oxygen content again; when subtracting the dark reaction content from the light, gross productivity would be obtains, and when subtracting the initial from the dissolved oxygen content of the one with light, net productivity could be obtained.

(c) Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond.
As shown by the graph, the net primary productivity decreases as the water gets...
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