Macromolecules and Enzymes

Which are units that make up proteins?

• 
  fatty acids

• amino acids

• glucose molecule

• 
  nucleotide molecules

Salivary amylase is an enzyme in humans that breaks down starches. What substance would humans have difficulty digesting without this enzyme?

• lipids

• nucleic acids

• proteins

• carbohydrates

Which best explains why the rate of a biochemical reaction decreases at high temperatures?

• The activation energy increases.

• 
  The shape of the enzyme changes.

• The enzyme-substrate complex forms.

• The bonds between substrates are broken.

How are the functions of a carbohydrate and a lipid similar?

• 
  Both are a source of energy.

• 
  Both are replicated during meiosis.

• 
  Both lower the activation energy of reactions.

• 
  Both dissolve nutrients in the digestive system.

Biomolecules contain a variety of atoms. Which biomolecule maintains a ratio of 1 carbon atom to 2 hydrogen atoms to 1 oxygen atom?

• 
  lipid

• protein

• nucleic acid

• carbohydrate

All organisms contain DNA and RNA. What are the subunits of DNA and RNA?

• simple sugars

• amino acids

• carbohydrates

• nucleotides

Salivary amylase is an enzyme in the human body that digests carbohydrates from food. When food mixed with saliva enters the stomach, the action of salivary amylase slows dramatically. Which causes salivary amylase enzyme to stop digesting food?

• The pH of the stomach is lower than in the mouth.

• The concentration of food decreases in the stomach.

• 
  The temperature of the food increases in the stomach.

• The food is mixed more in the mouth than in the stomach.

Some individuals are unable to digest the lactose found in the milk of cows. The digestive systems of these individuals MOST likely lack which?

• 
  a lipid that coats lactose molecules

• an ability to produce lactose internally

• 
  an enzyme that catalyzes lactose breakdown

• 
  a tolerance to lactose developed during childhood

Catalase is an enzyme that speeds up the decomposition of hydrogen peroxide into water and oxygen. Students conducted two investigations to determine the ideal conditions for the function of catalase. One investigation compared catalase activity at different values of pH. The other investigation compared catalase activity at different temperatures. According to the data in the graphs, which pH and temperature combination provides the BEST conditions for catalase to function?

• pH 5 and 4°C

• pH 5 and 25°C

• pH 7 and 37°C

• pH 7 and 50°C

Illustration 1 shows sugar that has formed a bond by the action of an enzyme. Illustration 2 shows the enzyme, and Illustration 3 shows the enzyme after the addition of heat. How does the addition of heat affect the ability of an enzyme to help the sugar molecules form a bond?

• Heat allows the sugar molecules to bond more quickly.

• Heat provides places on the enzyme for other molecules to bond.

• Heat changes the enzyme so that the sugar molecules can no longer bond.

• Heat changes the chemical composition of the sugar molecules so they no longer need the enzyme.