Biology Questions

Questions

1. Enzymes are critical to the function of cells because they speed up specific chemical reactions without speeding up unnecessary reactions within the cell. Without enzymes, many of the chemical reactions within a cell could only reach activation if the cell increased its internal temperature. This strategy is not efficient because it would speed up all chemical reactions and would denature essential proteins.

2. Enzymes are proteins. Enzymes have unique shapes and active sites that specifically react with certain substrates, like a lock and key.

3. Chlorophyll absorbs all visible wavelengths of light except green. Chlorophyll uses the lower energy red and yellow wavelengths instead of higher energy green because it evolved in the ocean. The ocean absorbs most of the shorter wavelength light (blue and green) at 2 meters deep which is inaccessible to early plant life. Plants thus evolved a mechanism to harvest low energy wavelengths very efficiently.

4. Photosynthesis is not just important for plants. It is important for animals because the waste product of photosynthesis, oxygen, is required for cellular communication and respiration. Furthermore photosynthesis harvests and stores energy in a readily accessible form, glucose which can be consumed by animals.

5. In the absence of oxygen, muscles resort to another way to get the required energy: glycolysis. Glycolysis involves the breakdown of glucose to two molecules of pyruvate. The difference in energy between the original glucose and the pyruvate produces two ATP. The pyruvate is then reduced by NADH which results in the production of lactic acid. This is wasteful and can also be damaging because of the drop in pH.

6. ATP synthase is a type of motor, which when protons pass through it, (from a high concentration gradient to a low concentration gradient) it turns and harnesses energy from these protons to bond together one ADP and phosphate molecule to make one ATP. ATP is important because it regulates biochemical pathways, is the major energy currency of the cell, and is essential to the formation of RNA and DNA.

7. A typical animal cell will lyse in plain water because of the difference in the concentration of essential metabolites. The cell has more metabolites within it that in the surrounding system. Accordingly, diffusion will cause the concentrations of metabolites to equilibrate between the cell and its surroundings. Since the cell cannot get rid of the metabolites through its cell wall it will instead dilute the metabolites by taking in more water. Increasing its water intake past capacity causes the cell to lyse.

8. Passive transport requires no energy and relies on the natural diffusion of substances across the cell membrane (such as water and some waste products). Active transport requires energy; the cell must expend energy to maintain a certain concentration of metabolites or to transport large molecules across the cell wall.