LS Bio 1.2

A group of students completed two experiments. Their notes are below:

Experiment 1:

• * Hydrogen peroxide was poured on a slice of raw potato.

• * The peroxide bubbled vigorously.

• * The peroxide was broken down into water and oxygen.

• Experiment 3:

• * A slice of raw potato was heated and then hydrogen peroxide was poured on it.

• * There was no visible reaction.

• Which statement explains the results of these experiments?

• Heating the potato had no effect on the potato enzymes.

• Heating the potato caused the hydrogen peroxide to evaporate, so the reaction did not occur.

• Heating the potato caused the potato enzymes to release the water and oxygen from the hydrogen peroxide.

• Heating the potato caused a shape change in the potato enzymes, so they could no longer function properly.

An enzyme has an optimal temperature of 25 degrees Celsius. During an experiment, which action would most likely increase the rate of the reaction?

• decreasing the light intensity

• increasing the temperature above 25 degrees Celsius

• decreasing the amount of substrate available

• increasing the temperature from 15 degrees Celsius to 25 degrees Celsius

Under which condition is the speed of cellular chemical reactions within a cell most likely to decrease?

• The rate of cell division increases.

• The concentration of reactants decreases.

• The enzyme involved increases in quantity.

• The products of the reaction decrease.

Hydrogen peroxide naturally breaks down into oxygen and water over time. When exposed to the enzyme catalase, hydrogen peroxide is rapidly converted into oxygen and water.

What feature of catalase most likely is responsible for the change in the rate of conversion of hydrogen peroxide into water and oxygen?

• Catalase speeds up the conversion of hydrogen peroxide into water and oxygen by decreasing the reaction's activation energy.

• Catalase bonds permanently with the reactants causing hydrogen peroxide to rapidly break down by increasing the activation energy.

• Catalase has a flexible structure that allows it to bind and convert any small hydrogen containing compound into water and oxygen.

• Catalase remains intact, so small amounts of it convert large amounts of hydrogen peroxide into water and oxygen immediately.

A scientist wants to test the effect of temperature on human enzyme action. The scientist sets up an experiment to measure the rate of enzyme activity at 10^o intervals from 0^oC to 100^oC. The graph shows the results.

Based on the data, what can be concluded?

• • The enzyme begins to work at 10^oC.

• • This enzyme ceases to function at 60^oC.

• • The highest activity occurs between 20^oC and 40^oC.

• • The optimum temperature for enzyme activity is 25^oC.

The graph shows the action of trypsin at different pH levels.

Based on the data, what can be concluded?

• • Trypsin works best around a pH of 6.

• • Trypsin works best around a pH of 8.

• • Trypsin does not work under acidic conditions.

• • Trypsin does not function under basic conditions.

A scientist obtained bean seeds and exposed them to varying temperatures ranging from 0^oC to 50^oC. The rate of germination of the seeds was found to be different.

• • Cellulose needs a certain temperature to function efficiently.

• • Acids are ineffective once a specific temperature is reached.

• • Glucose breakdown is affected by temperature.

• • Enzyme activity differs at certain temperatures.

Tags

NGSS.HS-PS1-5

Baby food manufacturers sometimes use proteases in their products. Proteases function by catalyzing the breakdown of protein, making digestion easier for babies. What type of molecule are proteases?

• • enzymes

• • hormones

• • reactants

• • substrates

Enzymes catalyze chemical reactions in the human body. Which statement best describes how enzymes work?

• • They speed up chemical reactions by increasing the activation energy.

• • They slow down chemical reactions by increasing the activation energy.

• • They slow down chemical reactions by lowering the activation energy.

• • They speed up chemical reactions by lowering the activation energy.

Tags

NGSS.HS-PS1-5

Bananas will turn brown when cut open because enzymes are released from the cut cells that react with other molecules in the fruit. A caterer, preparing fruit trays for a banquet, adds lemon juice (citric acid) to the cut bananas to prevent the reaction.

Which explanation best describes why the lemon juice prevents the browning?

• • Adding lemon juice lowers the pH which slows enzyme activity.

• • Lemons have different enzymes than bananas so no reaction occurs.

• • The addition of lemon juice reduces the temperature of the bananas which slows enzyme activity.

• • Cut bananas are composed of different proteins than whole bananas so no reaction occurs.

Tags

NGSS.HS-PS1-5