Question

1. What is activation energy?

A. The energy used by the active site to split a substrate.

B. The energy released when a substrate binds to an active site.

C. The energy required to start a metabolic reaction.

D. The energy required to raise the temperature of 1 gram of water by 1 degree Celsius.

2. Which statement defines your body's metabolic rate?

A. The speed at which chemical reactions occur when you are resting but awake

B. The number of Calories needed to keep your weight stable

C. All of the chemical reactions in your body

D. A measure of your body’s energy use

3. Which statement about enzymes is true?

A. One enzyme can catalyze many different types of reactions for a variety of substrates.

B. The shape of an enzyme determines its specificity.

C. Enzymes eliminate the activation energy barrier.

D. An enzyme molecule is permanently changed by the substrate molecule.

4. Which reaction occurs during glycolysis?

A. Glucose is converted into carbon dioxide.

B. Glucose is converted into water.

C. Glucose is converted into ATP.

D. Glucose is converted into pyruvic acid.

Answer 1

1: (c) The energy required to start a metabolic reaction.

• The activation energy is defined as the amount of energy required to start a chemical reaction, measured in joules (J) or kilojoules (kJ) per mole (the molecular weight in grams) of reactants.
• Enzymes are proteins that bind to a molecule, or substrate, to modify it and lower the energy required to make it react.
• The activation energy is affected by the enzymes.Enzymes are proteins that lower the activation energy of a chemical reaction.

2: (D) A measure of your body’s energy use   

  Metabolic rate means the amount of chemical energy liberated in the body per unit time. Chemical energy is measured in calories.The basal metabolic rate accounts for about 60 to 75% of the daily calorie expenditure by individuals.It is the amount of energy used up by the body during a unit time.

3:(D) An enzyme molecule is permanently changed by the substrate molecule

• Enzymes are globular proteins that are responsible for the speeding up of the reactions.They reduce the activation energy needed for a reaction to proceed and produce products.
• Enzymes have a region called an active site. The site is the "lock" into which a substrate "key" fits in it.The enzyme then fits closely around the substrates. This is called induced fit.
• Enzyme activity is affected by substrate type, temperature, pH and substrate concentration.

​4:(D) Glucose is converted into pyruvic acid

  Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Glycolysis consists of an energy-requiring phase followed by an energy-releasing phase.The glycolysis converts the glucose into two molecules of pyruvic acid.Glycolysis takes place in the cytosol of a cell, and it can be broken down into two main phases: the energy-requiring phase.