Energy and Metabolism

KEY WORDS:EnergyFree Energy (ΔG)Potential energyKinetic energyEnzymeSubstrateActivation energyExergonic reactionEndergonic reactionCatalystATP/ ADP

Energy

•The capacity to do work•Move matter

Types of energy

Question: __________ is an example of kinetic energy, and __________ is an example of potential energy.

1. Fire; a piece of wood

2. A loaded gun; a flying bullet

3. A rock on top of a hill; a rock rolling down the hill

4. None of these are correct.

5. All of these are correct.

•Kinetic

•Potential

Chemical Energy•Stored in chemical bonds -high energy electrons

•Some molecules store a lot of energy

•Some molecules store much less

Carbos, lipids

Carbon dioxide, water

Chemical Energy

•Energy can be transferred/transformed

Sugar + oxygen carbon dioxide + water + heat

C6H12O6 + O2 CO2 + H2O + Energy

First Law of Thermodynamics:

Energy: neither created nor destroyed

• Converted from one form to another• Exchanged between substances

All exchanges of energy increase the entropy of the universe

Entropy:•Disorder or randomness of a system

•Heat is most disorganized form of energy

•Reactions that ↑ entropy happen spontaneously & release energy

Second Law of Thermodynamics:

Two laws of thermodynamics

Energy Transformed

Exergonic Reactions

•Release energy

•“Spontaneous”

•Usually breakdown of complex molecules

Endergonic Reactions

•Not “Spontaneous”

•Usually involve synthesis of complex molecules

6CO2 + 6H2O C6H12O6 + 6O2

•Require energy

+ Energy

1. CO2 and H2O Glucose 2. Amino acids Proteins3. Triglycerides Fatty acids4. Ions moving across membrane from an

area of high concentration to an area of low concentration.

Question: Which of the following reactions is endergonic?

Question:

Which of the following reactions releases energy?

1. CO2 and H2O Glucose

2. Amino acids Proteins

3. Triglycerides Fatty acids

4. Ions moving across membrane from an area of high concentration to an area of low concentration.

Coupled Reactions

glucose

CO2 + H2O

Energy

Exergonic Endergonic

Energy

Amino acids

Protein

Exergonic provides energy for the endergonic

Living organisms

Metabolism •All chemical reactions in an organism

Anabolism Catabolism

Living organisms •Capture energy to drive chemical reactions.

EnergyEnergy

EnergyEnergy

•Convert “raw” energy into usable form•Sunlight, food ATP

The structure and hydrolysis of ATP

ATP: the Cell’s Rechargeable Battery

• ATP energy

ADP charged battery dead battery

• This energy can then be used to run an energy requiring reaction.

The ATP cycle

1. is never lost or gained, but is only transformed2. always requires an ultimate source such as

the sun3. can never be gained, but can be lost4. can never really be harnessed5. can never be transformed

According to the first law of thermodynamics, energy

1. Some energy is lost, but other energy is created.2. Some energy must come from the sun.3. Some energy is transformed into heat.4. Energy is gained for future use.5. Some energy is permanently and completely

destroyed.

Each time there is a chemical reaction, some energy is exchanged. According to the second law of thermodynamics, with each exchange

1. mechanical energy2. heat3. complex carbohydrates4. chemical bond energy5. amino acids

ATP stores energy in the form of

The complexity of metabolism

Equation: Gibb’s Free Energy

ΔG = ΔH – TΔSEnergy

available for work

All energy

Energy NOT

available for work

The relationship of free energy to stability, work capacity, and spontaneous change

Energy changes in exergonic and endergonic reactions

Energy profile of an exergonic reaction

Disequilibrium and work in closed and open systems

Is ΔG for an exergonic reaction positive or negative?

What is the difference between:

AnabolismCatabolismMetabolism

From an energy perspective, when is equilibrium reached?

Enzymes

KEY WORDS:

EnzymeActivation energyCatalystSubstrateActive siteInduced fitCoenzymeAllosteric siteCompetitive inhibitorNoncompetitive inhibitorFeedback inhibition

Enzymes and Shape

Active Site

Induced fit: “Handshake” between substrate and enzyme

Activation Energy

Activation Energy

Net Energy Released

Enzymes•Proteins that speed up chemical reactions (catalysts)

•Lower activation energy for a reaction

• S = Substrates (reactants) enter reaction.

• P = Product (what you get at the end) result

• E = Enzymes mediate specific steps

sucrasesucrose + H2O glucose + fructose

E + S ES E + P

Enzyme reactions can be simplified as:

The catalytic cycle of an enzyme

Enzymes

Key Points:

•Catalyze reactions

•Don’t change reactions•Same net release/use of energy

•Enzymes are not changed by reaction

•Each enzyme catalyzes a specific chemical reaction

Enzymes lower the barrier of activation energy

1. lowering the temperature2. lowering the pressure3. using an enzyme4. changing the amount of the reactants5. supplying ATP

Which of the following will lower the activation energy of a reaction in a cell?

1. lowering the temperature2. lowering the pressure3. using an enzyme4. changing the amount of the reactants5. supplying ATP

Which of the following will lower the activation energy of a reaction in a cell?

1. accelerate specific chemical reactions2. are not chemically altered by binding with a

substrate3. lower the activation energy of specific chemical

reactions4. all of the above5. a and c only

Enzymes

4 Things that Affect Enzyme Activity

1. Substrate concentration

2. Enzyme concentration

3. pH

4. Temperature

Shape of enzyme(Protein denatured)

Environmental factors affecting enzyme activity

Enzyme Regulation

• Enzymes can be turned on and off

• Regulated by other molecules in the cell

• Examples: – Allosteric regulation– Feedback inhibition– Inhibitors

Inhibition of enzyme activity

Allosteric regulation of enzyme activity

Feedback inhibition

If an enzyme solution is saturated with substrate, the most effective way to obtain an even faster yield of products is:

a) Add more enzyme

b) Heat the solution

c) Add more substrate

d) Add an allosteric inhibitor

e) Add a noncompetitive inhibitor

An enzyme accelerates a metabolic reaction by

a) Altering the overall free energy change for the reaction

b) Making an endergonic reaction occur spontaneously

c) Lowering the activation energy

d) Pushing the reaction away from equilibrium

e) Making the substrate molecule more stable

Some bacteria are metabolically active in hot springs because

a) They are able to maintain a cooler internal temperature

b) High temperature facilitates active metabolism w/o need of catalysis

c) Enzymes have high optimal temperatures

d) Enzymes are insensitive to temperature

1. consists of a series of chemical reactions2. uses a number of enzymes3. involves the modification of a series of substrates4. proceeds by means of each enzyme leaving a

succeeding reaction to a different enzyme5. all of the above

Glycolysis is a metabolic pathway that helps living things extract energy from food. From this we know that glycolysis