Homework 2 Fall09

Homework 2 Fall09 - MCB301 Fall 2009 Homework #2 due Sept...

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MCB301 Fall 2009 Homework #2 due Sept 14/15 (25 pts total) Enzymes and Adaptation (7 pts total) 1. What are exoenzymes and why are they important for the growth of bacteria. (2 pts) Exoenzymes are enzymes involved in catalyzing biochemical reactions that are excreted out of the cell. (1 pt) Exoenzymes are important for breaking down large substrates into smaller units that can be more easily brought into the cell. (1 pt) 2. Why does Escherichia coli not need to excrete amylase to survive in its natural habitat? (1 pt) Starch (the substrate of amylase) is not normally found in its habitat (1 pt). Starch found in ingested foods is already broken down to simple organic molecules by the time it reaches the colon. E. coli can utilize the simple organic molecules. 3. Why is the ability to grow using only fermentative metabolism important to Escherichia coli ? (1 pt) Escherichia coli is a bacterium that inhabits the colon which is an anaerobic environment. There is no oxygen available for aerobic respiration, so it must grow by fermentation (1 pt). 4. Why do bacteria that are oxidative usually grow better than bacteria that are only fermentative? (1 pt) Oxidative growth (e.g., aerobic respiration) results in the production of much more energy (i.e., ATP) than fermentative growth. (1 pt) The greater amount of energy produced, the greater amount of biosynthetic reactions can occur (i.e., growth). 5.
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Homework 2 Fall09 - MCB301 Fall 2009 Homework #2 due Sept...

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