LESSON 3 - ENERGY & ENZYMES

WHAT IS ENERGY?

The capacity to do work or be transferred as heat and can be converted from one form to another

WHAT IS KINETIC ENERGY?

The energy of motion

WHAT IS POTENTIAL ENERGY?

Stored energy

WHAT ARE THE ENERGY LEVELS OF THE ELECTRONS OF AN ATOM?

WHAT IS AN ISOLATED SYSTEM?

Does not exchange matter or energy with its surroundings

WHAT IS A CLOSED SYSTEM?

Exchanges energy but not matter with surroundings

WHAT IS AN OPEN SYSTEM?

Exchanges energy and matter with surroundings and is the most important thing in biology

WHAT IS THERMODYNAMICS?

The study of energy transformations or changes

WHAT IS THE FIRST LAW OF THERMODYNAMICS?

Energy can be transferred or transformed from one form into another, but it cannot be created or destroyed

WHAT IS ENTROPY (S)?

• The tendency of energy to become dispersed or spread out

• Measure of disorder or randomness

• Most increase through transformation of energy into heat

WHAT IS THE SECOND LAW OF THERMODYNAMICS?

• Each time energy is transferred or transformed, some are lost as entropy (becomes unavailable to do work)

  • Can never have 100% efficiency

  • Increases the entropy (disorder) of a system + surroundings

WHAT ARE SPONTANEOUS REACTIONS?

• Occur without a constant input of energy

• Means energetically favourable

• Reactions tend to be spontaneous if products have less potential energy than reactants

• Reactions tend to be spontaneous when products are less ordered than reactants

• Entropy, or S: Amount or randomness or disorder

WHAT IS ENTHALPY (H)?

Is the total heat or total energy content

Total Energy = Usable Energy + Unusable Energy

H = G + TS

ENERGY CONTENT

• Total Energy = Enthalpy (H)

• Usable Energy = Free Energy (G)

• Unusable Energy = Entropy (S)

• Temperature (T)

WHAT ARE ENDOTHERMIC REACTIONS?

Transformations that result in a system taking up heat from its surroundings (+ve ΔH)

• Products have less total/thermal energy than reactants (+ve ΔH)

• Requires input of energy 

• Tend to be non-spontaneous

WHAT ARE EXOTHERMIC REACTIONS?

Transformations that release heat to the surroundings (-ve ΔH)

• Products have less total/thermal energy than reactants (-ve ΔH)

• Energy released 

• Tend to be spontaneous 

HOW DOES A REACTION BECOME SPONTANEOUS?

If entropy increases, reaction becomes spontaneous

WHAT IS FREE ENERGY (G)?

• Energy available to do work (G) = Total energy (H) - Energy lost to entropy (TS): G = H – TS

• Thermodynamics is the study of energy transformations or changes. Therefore:

ΔG = ΔH - TΔS

• Δ (delta) – change (final state – initial state)

• ΔG – change in free energy, the amount of energy available to do work (Hibbs Free Energy)

• ΔH – change in enthalpy, total energy available 

• T – absolute temperature (degree Kelvin)

• ΔS – change in entropy, degree of disorder

WHAT ARE EXERGONIC REACTIONS?

• Amount of energy released (-ΔG)

• Spontaneous 

• Release energy 

• Energy reactants > products 

• ΔG negative 

WHAT ARE ENDERGONIC REACTIONS?

• Amount of energy available to do work (+ΔG)

• Non-spontaneous 

• Requires an input of energy 

• Energy products > reactants 

• ΔG positive 

EXPLAIN DIFFUSION ACROSS A MEMBRANE

WHAT IS EQUILIBRIUM?

Is state of maximum stability

• Point is reach when reactants are converted to products and products are converted back to reactants at equal rates (ΔG = 0)

• Point is also reach when the concentration of a molecule is the same on both sides of a membrane, and rate of movement is the same in both directions

  • At equilibrium, a system has no capacity to do work

  • At the point of equilibrium, molecules do not stop reacting

  • At equilibrium, the rate of the forward reaction equals the rate of the backward reaction

  • As a system moves toward equilibrium, the free energy change (energy available to do work, ΔG) of the system becomes lower

  • At equilibrium, there is no drive for change in the forward or reverse directions, ΔG = 0

EXPLAIN EQUILIBRIUM IN LIVING SYSTEMS

• Living systems are highly organized (maintain low entropy)

• Living systems are OPEN, which means they bring in both energy and matter from surroundings and use them to do work and maintain an organized state

• They release energy and disordered molecules into the environment (surroundings); therefore, the second law of thermodynamics is upheld, as the entropy of the system and surroundings increases

WHY DO WE NEED TO EAT?

• Organisms never reach equilibrium (ΔG = 0); life requires a constant supply of energy

• A significant portion of the energy we consume in food is used to maintain a low entropy, highly organized state for our cells

EXPLAIN THE FLOW OF ENERGY THROUGH THE BIOSPHERE

• Photosynthesis: Captures light energy and uses it to convert carbon dioxide into carbohydrates

• Cellular Respiration: Breaks down carbohydrates and transforms the energy into ATP

WHAT ARE METABOLIC PATHWAYS?

Series of sequential reactions in which products of one reaction are used immediately as reactants for the next reaction in the series

WHAT ARE CATABOLIC PATHWAYS?

Energy is released by breakdown of complex molecules to simpler compounds

WHAT ARE ANABOLIC PATHWAYS?

Consumes energy to build complicated molecules from simpler ones

WHAT IS CATABOLISM?

Breakdown of molecules into smaller unites, releasing energy

WHAT IS ANABOLISM?

Building of more complex molecules/macromolecules from smaller units, requiring an input of energy

WHAT IS METABOLISM?

Collection of all chemical reactions present within a cell or organism

WHAT IS ATP HYDROLYSIS?

Is an exergonic reaction that can be coupled to make otherwise endergonic reactions proceed spontaneously

WHAT IS ENERGY COUPLING?

The coupling of an endergonic reaction to an exergonic reaction

EXPLAIN THE ATP/ADP CYCLE?

WHAT ARE ENZYMES?

Are a special group of proteins that can increase the rate of chemical reactions

WHAT ARE ENZYME-CATALYZED REACTIONS?

• Enzymes bind to a reactant (substrate)

• After binding to reactant, and ultimately releasing the product(s), the enzyme is uncharged

• Highly specific, recognizing a unique substrate or a class of similar substrates

WHAT IS ACTIVATION ENERGY (EA)?

Initial energy investment required to start a reaction

WHAT ARE BIOLOGICAL CATALYSTS?

• Catalyst: Chemical agent that speeds up the rate of reaction without itself being chemically altered

• Enzymes: Biological catalysts

EXPLAIN THE RATE OF REACTION

WHAT IS ENZYME SPECIFICITY?

• Active site of enzyme combines briefly with reactants (substrates)

• After releasing the product, the enzyme is unchanged

EXPLAIN THE CATALYTIC CYCLE OF ENZYMES

WHAT ARE ENZYME COFACTORS?

Non protein groups necessary for catalysis to occur

WHAT ARE COFACTORS?

Metallic ions (Mg2+, Fe2+, Cu2+, Zn2)

WHAT ARE COENZYMES?

Organic cofactors like vitamins

WHAT IS TRANSITION STATE?

Occurs during catalysis where the substrate and active site form

WHAT ARE THE 3 MAJOR MECHANISMS THAT ENZYMES FACILITATE THE FORMATION OF THE TRANSITION STATE?

1. Bringing the reacting molecules into close proximity

2. Exposing the reactant molecules to altered environments that promote their interactions

3. Changing the shape of a substrate molecule

WHAT HAPPENS WHEN SUBSTRATE CONCENTRATION IS LOW?

• Enzymes and substrate collide infrequently

• Reaction rate slows

WHAT HAPPENS WHEN SUBSTRATE CONCENTRATION IS HIGH?

• Enzymes become saturated with reactants

• Rate of reaction levels off

WHAT CAN ENZYME AND SUBSTRATE CONCENTRATIONS DO?

WHAT ARE ENZYME INHIBITORS?

Are nonsubstrate molecules that can bind to an enzyme and decrease its activity

WHAT ARE COMPETITIVE INHIBITION?

Inhibitor competes with normal substrate for active site

WHAT ARE NONCOMPETITIVE INHIBITION?

Inhibitor does not compete with normal substrate for active site, but combines with sites elsewhere on enzyme

EXPLAIN COMPETITIVE INHIBITION OF ENZYME ACTIVITY