SC.912.L.18.11 Enzymes

The diagram below represents the effect of pH on the activity of a digestive enzyme.

Pepsin is a digestive enzyme found in the stomach. Which statement describes why the enzyme activity changes when the pH increases?

• Enzyme activity decreases because the enzyme unfolds.

• Enzyme activity decreases because there is less substrate available.

• Enzyme activity decreases because there is a decrease in OH^- ions.

• Enzyme activity decreases because there is an increase in H⁺ ions.

The graph below shows the rate of reaction versus enzyme concentration for a biochemical reaction.

What is the best explanation of the relationship between rate of reaction and enzyme concentration?

• At low enzyme concentrations, there is less competition for the enzyme active site, and the reaction rate is high.

• As enzyme concentration decreases, the substrates will fill all available enzyme active sites, thus halting the reaction rate.

• As enzyme concentration increases, there are more enzyme active sites available, and the reaction can proceed at a faster rate.

• At high enzyme concentrations, there are many enzyme active sites that are not occupied by a substrate, so the reaction rate is slow.

The graph below shows the breakdown of a protein in the human stomach without a digestive enzyme. Which graph shows the reaction if an enzyme were present?

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Tags

NGSS.HS-PS1-5

A digestive enzyme that is released into the small intestines by the pancreas is used to break down proteins. Data from a chemical reaction with the digestive enzyme are shown in the graph below.

According to the graph, which conclusion can be made about this digestive enzyme?

• It functions most efficiently from pH 7.0 to pH 9.0.

• It will work best if pH levels increase above pH 10.0.

• It breaks down the most proteins between pH 1.0 and pH 5.0.

• It is effective at breaking down proteins from pH 1.0 to pH 10.0.

Which of these explains why an increase in temperature above a certain point will cause an enzyme to denature?

• High heat causes the shape of the protein to change.

• High heat causes the activation energy level to decrease.

• High heat causes the substrate for the enzyme to be used up.

• High heat causes the substrate and the enzyme to fuse together.

A catalyst is a substance that enables a chemical reaction to proceed at a faster rate. How do enzymes enable a chemical reaction to proceed at a faster rate? 

• by lowering activation energy

• by increasing activation energy

• by altering the shape of the substrate

• by altering the shape of the active site

Tags

NGSS.HS-PS1-5

Lipase is an enzyme found in the human digestive tract that breaks down lipids into glycerol.  A student tested lipase to see how it functioned at different temperatures.  The student combined lipase and lipids in test tubes at varying temperatures.  The student then tested each set with indicators which revealed the presence of lipids or glycerol.  The results are given below.

Based on these results, what is the optimum (best) temperature range for lipase to function? 

• 0-15 degrees Celsius

• 0-60 degrees Celsius

• 15-45 degrees Celsius

• 45-60 degrees Celsius

The graph below shows how the activity level of three different enzymes varies with pH.

Based on the information in the graph, what can be determined about the activity of these enzymes?

• Each enzyme is active within a certain pH range.

• Enzyme C is most active at a neutral pH.

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  Each enzyme will react at all pH levels.

• Enzyme B will react only at pH 7.

Baby food manufacturers sometimes use proteases in their products.  Proteases catalyze the breakdown of the proteins in these, making digestion easier for infants.

 

Proteases are which of the following types of molecules.

• enzyme

• fatty acid

• carbohydrate

• nucleic acid

Some bacteria live in hot springs. Their cells contain enzymes that function best at  temperatures of 70 °C or higher.  At the temperature of 50 °C, how will the enzymes in these bacterial cells most likely be affected?

• The enzymes will be destroyed by lysosomes.

• The enzymes will lose their bond structure and fall apart

• The enzymes will require less energy to function than at 70 °C

• The enzymes will not increase the rate of reactions as much as they would at 70 °C