Properties of Water and Macromolecules

Water is essential for life. Its special properties make water the single most important molecule in plant life. Which of the following properties of water enables it to move from the roots to the leaves of plants?

• Water expands as it freezes.

• Water exhibits cohesive behavior.

• Water is an excellent solvent.

• Water is able to moderate temperature.

Large bodies of water, such as lakes and oceans, do not quickly fluctuate in temperature. What is the reason for this phenomenon?

• A. Water is an acid.

  
  

• B. Water is a versatile solvent.

  
  

• C. Water has a high heat capacity.

  
  

• D. Water acts as a buffer.

  
  

Why does ice stay at the top of oceans instead of sinking to the bottom?

• Ice is colder than liquid water.

• Ice is more dense than liquid water.

• Ice is warmer than liquid water.

• Ice is less dense than liquid water.

Water is often called the 'universal solvent' because many substances can be dissolved in water. What property of water allows it to be such a versatile solvent?

• purity

• high heat capacity

• polarity and cohesion

• expansion upon freezing

As food travels through the digestive system, it is exposed to a variety of pH levels. The stomach has a pH of 2 due to the presence of hydrochloride acid (HCI), and the small intestine has a pH ranging from 7 to 9. HCI converts pepsinogen into pepsin, an enzyme that digests proteins in the stomach. Which of the following most likely happens to pepsin as it enters the small intestine?

• It becomes inactive.

• Its shape changes to engulf large proteins.

• Its activity increases to digest more proteins.

• It begins to replicate.

In living cells, enzymes act as catalysts, which may reduce the amount of activation energy required for a chemical reaction to occur. In the graphs below, pathway x is a solid line representing the uncatalyzed reaction. The dotted line shows the catalyzed reaction. Which graph best illustrates the changes in a reaction when the catalyst reduces the amount of energy required?

• A

• B

• C

• D

The diagram below shows the general structure of an amino acid. Which type of molecule is formed from amino acids?

• lipids

• proteins

• carbohydrates

• nucleic acids

You are analyzing a compound in the laboratory. You find that it is made up of carbon, hydrogen, and oxygen in a ratio of two hydrogen atoms for each carbon atom. How will you classify the compound?

• lipid

• protein

• carbohydrate

• nucleic acid

RNA and DNA are which type of macromolecules?

• carbohydrate

• nucleic acid

• lipid

• protein

What will most likely happen if an appropriate enzyme is added to a chemical reaction?

• A. The reaction rate will increase.

  
  

• B. The equilibrium of the reaction will be maintained. 

  
  

• C. The reaction rate will decrease.

  
  

• D. The reaction will stop.