Chapter 6

Question 1

Two Types of Energy

Answer 1

Kinetic:
Energy of motion
Mechanical

Potential:
Stored energy
Chemical - comprised of organic molecules

Question 2

Relationship between chemical and mechanical energy

Answer 2

Animals convert chemical (potential) energy into a type of kinetic energy (mechanical). Example when a moose walks

Question 3

First Law of Thermodynamics or Law of Conservation of Energy

Answer 3

Energy cannot be created or destroyed but energy can be changed from one form to another

Question 4

What is an example of the First Law of Thermodynamics

Answer 4

Solar Energy flowing from the sun some is dissipated and becomes heat and other is converted by the plant into chemical (potential) energy. The moose converts a portion of this chemical energy into mechanical of motion and most of the chemical energy dissipates into heat.

Question 5

Heat is

Answer 5

Disorderly energy that cannot be easily used

Question 6

Second Law of Thermodynamics - Law of Entropy

Answer 6

Every energy transformation (solar to chemical, solar to heat, etc.) there is a loss of usable energy

Waste energy goes to increase disorder

Entropy - is a scientific concept that is most commonly associated with a state of disorder, randomness, or uncertainty.

Question 7

Example of Entropy Law

Answer 7

The second law tells use that glucose tends to break apart into carbon dioxide and water over time. Because glucose is more organized and structured, and therefore less stable than its breakdown products.

Question 8

Explain the importance of entropy to a living system

Answer 8

Organisms that consume potential energy that is originally provided by the sun and sun energy is converted to potential energy in a more stable form which is easily converted to mechanical energy. A living cell can function because it serves a a temporary repository of order, purchased at the cost of constant flow of energy

Question 9

What is Metabolism?

Answer 9

Sum of cellular chemical reactions in cell

Reactants participate in a reaction

Products form as result of a reaction

Question 10

Relationship between Reactants and Products

Answer 10

Reactants are substances that participate in a reactions, which products are the substances that form as a result of a reactions.

Question 11

What is Free energy

Answer 11

Free energy is the amount of energy available to perform work

Question 12

Metabolism includes two types of reactions

Answer 12

Exergonic Reactions - Products have less free energy than reactants —release energy

Endergonic Reactions - Products have more free energy than reactants —require an input of energy

Question 13

What is ATP

Answer 13

Adenosine (Adenine and ribose) triphosphate - three phosphate groups

High energy compound used to drive metabolic reactions

Constantly being generated from ADP*

ADP - adenosine diphosphate composed of adenosine and two phosphate groups and is more stable and has lower potential energy.

Question 14

What is the ATP Cycle

Answer 14

in cells ATP carries energy between exergonic reactions (release energy) and endergonic reactions.

When a phosphate group is removed by hydrolysis*, ATP releases the appropriate amount of energy for most metabolic reactions.

The hydrolysis of ATP releases previously stored energy allowing the change of in free energy to do work.

Creation of ATP from ADP and inorganic phosphate requires energy input from other sources

*is any chemical reaction in which a molecule of water breaks one or more chemical bonds

Question 15

What are Coupled reactions

Answer 15

Energy released by an exergonic reaction captured in ATP

ATP is used to drive an endergonic reaction

in other words ATP breakdown is coupled to the energy requiring reaction, such that both the energetically favorable and unfavorable reactions occur in the same place, at the same time. ATP’s phosphate groups releases more energy than the amount consumed by the engergy-requireing reactions, the net reaction is exergonic, entropy increases, and both reactions proceed.

Question 16

Work-Related Functions of ATP

Answer 16

Primarily to perform cellular work
Chemical Work - Energy needed to synthesize macromolecules
Transport Work - Energy needed to pump substances across plasma membrane
Mechanical Work - Energy needed to contract muscles, beat flagella, etc

Question 17

What is an enzyme

Answer 17

is a molecule that speeds up a chemical reactions without itself being affected by the reaction.

Most enzymes are proteins.

Question 18

Metabolic Pathways

Answer 18

Reactions usually occur in a sequence

Products of an earlier reaction become reactants of a later reaction

Such linked reactions form a metabolic pathway

   Begins with a particular reactant,
   Proceeds through several intermediates, and 
   Terminates with a particular end product

Each reaction in a metabolic pathway requires a unique and specific enzyme

The end product will not be formed unless ALL enzymes in the pathway are present and functional

Question 19

What are substrates?

Answer 19

The reactants in an enzymatic reaction are called substrates for the enzyme.

The substrates for the first reaction are converted into products and those products then serve as the substrates for the next enzyme-catalyzed reactions.

Question 20

Energy of Activation

Answer 20

Molecules frequently do not react with one another unless they are activated in some way

 Energy must be added to at least one reactant to initiate the reaction
   Energy of activation

Enzyme Operation:
Enzymes operate by lowering the energy of activation
Accomplished by bringing the substrates into contact with one another

IMPORTANT to note that the enzyme has no effect on the energy content of the product, rather it only influences the rate of reaction

Question 21

What are enzymes referred as?

Answer 21

The catalysts of chemical reactions

Question 22

Enzyme-Substrate Complex

Answer 22

Only one small part of the enzyme, called the active site, associates directly with the substrate.

Induced fit model
Causes the active site to change shape
Shape change forces substrates together, initiating
bond

After the reaction has completed, the active site returns to its original state

Note only a small amount of enzyme is actually needed in the cell, because enzymes are not used up by the reaction; they are merely enable it to happen quicker.

Question 23

What is the difference between Degradation and Synthesis

Answer 23

Degradation:
Enzyme complexes with a single substrate molecule
Substrate is broken apart into two product molecules

Synthesis:
Enzyme complexes with two substrate molecules
Substrates are joined together and released as a single product molecule

Question 24

Factors Affecting Enzyme Activity

Answer 24

-Substrate concentration
Enzyme activity increases with substrate
concentration due to more frequent collisions

• Temperature
  Enzyme activity increases with temperature
  Body temperature of ectothermic animals (iguanas)
  often limits their reaction
  Body temperature of endothermic animals (polar
  bears) promotes rates of reaction

-pH
Most enzymes perform optimally at a particular pH

Question 25

Factors Affecting Enzyme Activity

Answer 25

Cells can regulate the presence/absence of an enzyme
Cells can regulate the concentration of an enzyme
Cells can activate or deactivate some enzymes

Question 26

What are Enzyme Cofactors

Answer 26

many enzymes require the presence of an inorganic ion or a nonprotein organic molecule at the active site in work properly.

These necessary ions or molecules are called cofactors.

Cofactors at the active site may participate in the reaction.

Non organic ions include metals such as copper, zinc or iron.

Question 27

What are Coenzymes

Answer 27

Coenzymes are nonprotein organic molecules

Vitamins are small organic compounds required in the diet for the synthesis* of coenzymes

Absence of certain vitamins will cause enzymatic activity to decrease resulting in a cell disorder–scurvy

*the composition or combination of parts or elements so as to form a whole

Question 28

Phosphorylation

Answer 28

Phosphorylation – some enzymes require addition of a phosphate group. in other words, phosphorylation is the attachment of a phosphate group to a molecule or an ion.[

Question 29

What is an enzyme inhibition

Answer 29

Enzyme inhibition occurs when a molecule (the inhibitor) binds to the enzyme and decreases its activity

Question 30

Two Types of Inhibition (Reversible enzyme inhibition)

Answer 30

Competitive inhibition – the substrate and the inhibitor are both able to bind to active site

Noncompetitive inhibition – the inhibitor does not bind at the active site, but at an allosteric* site

*A site that is NOT active site (active site being the small part of the enzyme that associates directly with the substrate)

Question 31

Irreversible Inhibition

Answer 31

Materials that irreversibly inhibit an enzyme are known as poisons

Cyanide inhibits enzymes required for ATP production

Nerve gas irreversibly inhibits acetylcholinesterase required by the nervous system

Question 32

Oxidation-Reduction

Answer 32

Oxidation-reduction (redox) reactions:
Electrons pass from one molecule to another
The molecule that loses an electron is oxidized
The molecule that gains an electron is reduced
Both take place at same time
One molecule accepts the electron given up by the other

Easy way to remember what is happening in redox reactions is the term OIL RIG

Oxidation Is Loss Reduction Is Gain

Question 33

Electron Transport Chain

Answer 33

Consists of membrane-bound carrier proteins found in mitochondria and chloroplasts

Physically arranged in an ordered series

Question 34

Relating Chloroplasts to electron transport chain

Answer 34

Chloroplasts in plants capture solar energy and use it to convert water and carbon dioxide into carbohydrate. In other words chloroplasts are able to capture solar energy and convert it to the chemical energy of ATP, which is used along the hydrogen atoms to reduce (reduction) carbon dioxide. Oxygen is a by-product that is released.

The energy that living organisms utilize to support themselves only because carbohydrates can be oxidized in mitochondria

Question 35

Relating Mitochondria to electron transport chain

Answer 35

Mitochondria, present in both plants and animals, oxidize carbon-hydrates and use the released energy to build ATP molecules. In this reaction, glucose has lost hydrogen atoms (oxidized) and oxygen has gained hydrogen atoms (been reduced).

Question 36

ordered series of electron transport chain

Answer 36

Starts with high-energy electrons

Pass electrons from one carrier to another
Electron energy used to pump hydrogen ions (H+) to
one side of membrane
Establishes an electrochemical gradient across the
membrane
The electrochemical gradient is used to make ATP
from ADP – Chemiosmosis

Ends with low-energy electrons and high-energy ATP