biology quiz

At the start of a chemical reaction there was 320 kJ of energy (To1) and after the reaction (To2) was 180 kJ of energy. Use the formula To2 - To1 to determine the heat of reaction. Is this reaction endothermic or exothermic?

-140 kJ exothermic reaction since it is negative and releases energy.

At the start of a chemical reaction there was 32 kJ of energy (To1) and after the reaction (To2) was 80 kJ of energy. Graph the reaction and use the formula To2 - To1 to determine if the reaction was exothermic or endothermic.

48; since the answer is positive energy was energy gained.

calculate the activation energy if the reaction started with 125 kJ of energy and began the reaction at 200 kJ of energy.

75 kj

Identify the products in this reaction: 6H2O + 6CO2 🡪 C6H12O6 + 6O2

C6H12O6, and 6O2

Describe how temperature, pH, substrate concentration, catalysts, and competitive inhibitors affect the rate of chemical reactions.

Increasing temperature will increase the rate of reaction because molecules are moving faster and have a greater chance of colliding forming bonds, decreasing the temperature will decrease the rate of reaction because it slows particles down. pH can affect the rate of reaction by breaking the hydrogen bonds causing denatured proteins. An increase in substrate concentration will increase the rate of reaction because there are more particles to collide with each other forming bonds, a decrease in substrate concentration will decrease the rate of reaction because there are fewer particles to collide with each other. Adding catalysts will increase the rate of reaction. Competitive inhibitors will take up active sites on enzymes slowing the rate of reaction down.

Which phrase best describes an exothermic chemical reaction?

Releases more energy than it absorbs.

In the enzyme-substrate complex pictured, what is happening when the substrate is split?

The enzyme is breaking bonds in the substrate.

Given two areas with equal sunlight and available water. Area I has a high amount of atmospheric carbon dioxide while Area II has a low amount of atmospheric carbon dioxide. How does the rate of photosynthesis in Area I compare to that in Area II?

The rate of photosynthesis increases with an increase in carbon dioxide in area 1.

Pepsin, a common enzyme found in the stomach, is most active at pH values between 0.5 and 2.5. It works slowly between pH values of 2.6 and 3.4. Beyond a pH of about 3.5, it becomes completely inactive. What causes this to happen?

The shape of the enzyme is denatured, changing its active site needed for binding to specific substrates.

According to the Law of Conservation of Energy, a reaction in one direction releases more energy than it absorbs, that same reaction in the opposite direction would

absorb more energy than it releases.

Reactants bind to enzymes at the

active site

An increase in temperature results in

an increase in reaction rate.

During photosynthesis, sugar C6H12O6 is produced from carbon dioxide, water and sunlight. Which statement BEST explains what happens during photosynthesis?

atoms of compounds are rearranged to form new compounds

The activation energy needed for a chemical reaction is decreased by the presence of a

catalyst or protein enzyme

All chemical reactions must break or form

chemical bonds_

Chemical reactions can be classified as either __ or _____.

endothermic and exothermic

Chemical reactions that absorb more energy than they release are considered to be

endothermic reactions

Activation _________ is required in order for a chemical reaction to occur.

energy

Which shows a reaction during which more energy is released than absorbed? Endothermic or exothermic?

exothermic

A catalyzed reaction will have a ________________activation energy, and this leads to a(n)________________in the reaction rate.

lower and increase

An example of a reaction that releases more energy than it absorbs is

photosynthesis_

a split substrate at the end or a reaction represents what?

products

Draw an energy diagram representing an exothermic reaction. Label the parts of the diagram that show the reactant energy, the product energy, and the activation energy. Do not include an enzyme.

reactant energy= 60kJ product energy= 40kJ activation energy= 60kJ

Draw an energy diagram representing an endothermic reaction. Label the parts of the diagram that show the reactant energy, the product energy, and the activation energy. Do not include an enzyme.

reactant energy=10 kJ product energy= 20 kJ activation energy= 40 kJ

Chemical reactions change ___ and make ___

reactants and products

An example of a reaction that absorbs more energy than it releases is

respiration

The molecule that an enzyme binds to is known as its

substrate

If the activation energy of a biochemical reaction is lowered, then

the reaction will happen faster.