Question

1. Which of the following are consistent with the laws of thermodynamics?

Energy can not be created or destroyed, but it can be transformed from one form to another
Energy can be created, but a cell must do work in order to accomplish this
Entropy decreases with every energy transformation
Once energy has been used to do work, it is destroyed.

2. Which of the following statements about individual enzymes is NOT true

They are organic compounds, usually made of protein
They are biological catalysts which increase the rates of chemical reactions
Any given enzyme can function at any pH
Enzymes denature if exposed to high temperature

3. Pepsin (an enzyme found in the stomach) acts best at pH of about 2, but is not active at pH 7 because...

It has become denatured
The high pH acts as a non-competitive inhibitor
Feedback inhibition
Substrates break down at pH higher than 5

4. ATP is important in cells because...

It is an inorganic cofactor
It transfers energy released from endergonic reactions to power exergonic reactions
It is an enzyme
It transfers energy released from exergonic reactions to power endergonic reactions

Answer 1

1. First option is correct because it is correctly defining the first and second law of thermodynamics. Energy can neither be created nor be destroyed but can be converted from one form to another.

Second option is incorrect and last option is incorrect because both of them are talking about creation and destruction of energy which is never possible.

Third option is incorrect because entropy increases with transformation. Entropy is the randomness of the molecules present in a reaction.

2. Third option is incorrect because enzymes cannot work at any temperature and pH. All the enzymes work at a specific temperature and specific pH called as optimum temperature and optimum pH. Any deviation from the value of the optimum temperature and pH results in the loss of three dimensional structure of enzyme and therefore loss of its catalytic activity.

3. If pepsin enzyme is working best at a pH of 2, it means this is its optimum pH. If we will increase the pH beyond two, then the three dimensional structure will be lost and the enzyme will be denatured. It will not be able to perform its catalytic activity. If we lower the pH less than 2, then the enzyme will become inactive and again it will not be able to catalyse reactions.

4. ATP is the energy currency of the cell. It is synthesized by The breakdown of glucose into carbon dioxide and water during cellular respiration in mitochondria. It synthesis is an exergonic reaction. It transferred the energy stored in it to endergonic reactions for the formation of complex Polymers using simple monomers.

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