Chapter 3 - Metabolism and Energy

Question 1

Metabolism

Answer 1

The sum of all chemical reactions in a cell or organism

Question 2

Energy

Answer 2

Is the ability to do work

Question 3

Types of Energy

Answer 3

• Kinetic Energy
• Potential Energy

Question 4

Kinetic Energy

Answer 4

The energy of motion

eg. Waves in the ocean, falling rocks, molecules and ions moving in a solution, heart muscles contrating

Question 5

Potential Energy

Answer 5

The stored energy that an object possesses as a result of its position relative to other objects or to its internal structure

eg. Chemical potential energy stored in the electrons and protons that make up atoms and molecules, gravitational potential energy

Question 6

First Law of Thermodynamics

Answer 6

The principle that states that energy can be transferred or transformed but it cannot be destroyed

eg. Photosynthesis - converting light energy into chemical potential energy, cellular respiration 0 converting glucose (chemical potential energy) into ATP (chemical potential energy), food chains - herbivores eat plants and the chemical potential energy from the plants is transferred to them

Question 7

Energy and Chemical Bonds

Answer 7

• Conversion of energy from one form to another depends on the breaking and formation of chemical bonds
• During a chemical reaction, the amount of potential energy available changes
  
  • Eg. Diver Example - The
    potential energy directly
    related to height of the
    diver above water
• The potential energy of electrons depends on their location with respect to the atomic nuclei. The farther away electrons are from the nucleus of an atom, the more potential energy they have
• The potential energy of outer electrons increases when they absorb energy or are in an ‘excited’ state

Question 8

Energy Changes During a Chemical Reaction E

Answer 8

• During a chemical reaction, some bonds are broken and new bonds are formed
• For bonds to break in reactants energy must be absorbed (energy is required to pull an electron from an atom)
• When bonds form in products energy is released
• The breaking of a chemical bond always requires additional energy. However, when electrons form a new bond, they move closer to the nucleus of another atom and release energy

Question 9

Bond Energy

Answer 9

A measure of the strength or stability of a covalent bond. It is measured in units of kJ/mol and is equal to the amount of energy absorbed per mole when the bond between atoms is broken or formed

Question 10

Activation Energy

Answer 10

The minimum amount of energy that chemical reactants must absorb in order for the chemical reaction to begin (minimum amount of energy to break chemical bonds in reactants).

Question 11

Transition Site

Answer 11

A temporary condition during a chemical reaction in which the bonds in the reactants are breaking and the bonds in the products are forming

Question 12

Exothermic Reaction

Answer 12

A chemical reaction in which the energy is released leaving the products with less chemical potential energy than the reactants

Question 13

Endothermic Reaction

Answer 13

A chemical reaction in which energy is absorbed, giving the products more chemical potential energy than the reactants

Question 14

Second Law of Thermodynamics

Answer 14

In every energy transfer or conversion, some of the useful energy in the system becomes unusable and increases the entropy of the universe

eg. The engine of a car converts only 25% of potential energy in gasoline into kinetic energy, cells convert 40% of the potential energy of glucose into usable energy through cellular respiration

Question 15

Entropy

Answer 15

• The release of unusable energy, in the form of random particle motion during an energy transformation, leads to an increase in the disorder, or randomness, of the system
• In thermodynamics, the degree of disorder is a measurable quantity called entropy

Question 16

When Does Entropy Occur

Answer 16

• Entropy of a system and its surroundings increases whenever there is any change, such as a chemical reaction
• All systems in the universe will tend towards disorder. - - Disorder increases when an orderly arrangement of objects becomes more randomly assorted

Question 17

Entropy and Chemical and Physical Changes

Answer 17

• Entropy is usually associated with the breaking down of large particles into smaller ones, or the spreading out of particles
• Entropy and Physical Changes: change of state and diffusion
• Entropy and Chemical Changes: solids react to form liquids or gasses, and liquids react to form gaseous products, the total number of product molecules is greater than the total number of reactant molecules

Question 18

Entropy and Living Things

Answer 18

• According to the 2nd law of thermodynamics, the overall entropy of a system is always increasing
• Living things bring in energy and matter and use them to establish order out of disorder
• By doing so, the entropy of the organism decreases, but the overall entropy of the universe increases

Question 19

Spontaneous Changes

Answer 19

• The 1st and 2nd law of thermodynamics allow us to predict whether a chemical or physical change can occur without the continuous input of additional energy
• A spontaneous change is a change that will once begun, continue on its own under a given set of conditions; it does not require a continuous supply of energy
  
  • Eg. Burning a match,
    diving into a swimming
    pool, a nail rusting

Question 20

Non-Spontaneous Changes

Answer 20

Cannot occur without a continual supply of energy

Eg. Boiling water on the stove (the change of state requires a continuous input of energy), a messy room becoming tidy, photosynthesis

Question 21

How to Determine if a Change will Continue Spontaneously or Not

Answer 21

Three factors determine whether a change will continue
- Energy changes
- Entropy
- Temperature

Question 22

Gibbs Free Energy

Answer 22

• Useful energy that is not lost in energy transformations and is still available to do work in a system is called free energy
• The free energy value of a chemical reaction provides us with useful information in the study of metabolism: it tells us which types of reactions provide fuel for our bodies
• Free energy is represented by the symbol G, for the physicist who developed the concept, Josiah Willard Gibbs

Question 23

Free Energy and Living Organisms

Answer 23

In living organisms, free energy is responsible for the chemical and physical work required in activities such as
- Synthesis of molecules
- Reproduction
- Movement

Question 24

Change in Free Energy

Answer 24

• The change in free energy (delta G) can be represented by - delta G = G final state - G initial state
• The change in free energy represents the difference in the free energy of the final state of the molecules as compared to the free energy of the initial state
• Negative Value: Can be used to do work in other reactions (occur spontaneously)
• Positive Value: Must gain free energy for the reaction to occur (does not occur spontaneously)