Module 6 — Making Life Work

Why do cells need energy?

Movement, Growth, Pump oins, Perform rxns needed for metabolism

What is the name of an organism that obtains energy from the sun? Give one example.

Phototroph —> Plants!

What kind of organism obtains energy through chemical compounds? Give one example

Chemotrophs —> Animals!

What is an autotroph?

An organism that makes its own food

It can convert CO2 into glucose!

What is a heterotroph?

An organism that cannot make its own food

It must obtain its food by eating an autotroph or another heterotroph

What is the simple definition of metabolism?

The chemical processes that occur within a living organism in order to maintain life.

What does "forming pathways" in metabolism describe?

As metabolic rxns (buildup/breakdown of compounds) are continuously happening, many of them are linked in such a way that the products of one rxn are the reactants of another.

What are the two branches of metabolism?

anabolism and catabolism

Define anabolism

Building molecules from smaller units. Requires ATP

Define catabolism

Breaking down molecules into smaller units. Produces ATP

True or false: Anabolic reactions generate energy.

False. Anabolic reactions require ATP.

Potential vs. Kinetic Energy

Potential (aka chemical energy) —> Stored energy

Kinetic —> Motion

Note: energy can be converted from one form to another.

Example: Potential energy stored in our food becomes kinetic energy when we exercise and releases carbon dioxide, water, and heat as by-products

How are bond strength and potential energy linked? How does the potential energy chang between strong vs. weak bonds?

Strong bonds = less potential energy

Weak bonds = more potential energy

What chemical form does the cell use to store readily accessible energy? (Think: energy currency) Why?

ATP —> it has a very high amount of potential/chemical energy

Difference between ATP, ADP, AMP

ATP is fully charged with three phosphate molecules (tri)

ADP is half charged with two phosphate molecules (di)

AMP is almost no charge with one phosphate molecule (mono)

What is Adenosine triphosphate composed of?

an adenine molecule, a sugar molecule (ribose), and three phosphate groups

Where is the potential energy stored in ATP?

Between the phosphate groups, because they are weakly bonded.

Recall: weak bonds = high potential energy.

What is the first law of thermodynamics?

Energy can be transferred and transformed, but it cannot be created or destroyed.

When electrons move from a higher to lower energy level, what is released?

Energy is released as heat or light

What is the second law of thermodynamics?

The principle stating that every energy transfer or transformation increases the entropy of the universe, because energy cannot be changed from one form into another without a loss of usable energy (not 100% efficient)

What is Gibbs free energy (delta G)

The amount of energy available to do work

What is delta G when the products of a reaction has more free energy than the reactants?

Positive. This is thermodynamically unfavourable as it requires an input of energy. Think: biking up a hill

If the reactants have more free energy than the products, what is delta G?

Negative. This is thermodynamically favourable as it has energy available for use in other processes. Think: biking downhill.

In summary, Anabolism and Catabolism have what delta G values?

Anabolism —> Positive delta G (needs energy)

Catabolism —> Negative delta G (releases energy)

Define endergonic vs. exergonic reactions

Endergonic- when a reaction needs energy for a reaction to occur. (Describes a reaction that absorbs energy on net, because the free energy of the products is greater than the free energy of the reactants.

Exergonic- when a reaction releases energy. (Describes a reaction that releases energy on net, because the free energy of the products is less than the free energy of the reactants.

What is the formula for total energy? What about delta G? What does each variable represent?

H = G + S

(delta G) = (delta H) - (T)(delta S)

H= total energy (enthalpy)

G= energy available to do work

S= energy lost to entropy or disorder

T= absolute temperature in Kelvin

What happens when ATP is hydrolyzed?

Energy is released. The reaction is exergonic (spontaneous).

ATP + H2O ---> ADP + Pi (inorganic phosphate which has the formula H2PO4-) + Energy (7.3 kcal / mol ATP)

What is activation energy?

E (subscript a).

The minimum amount of energy needed to initiate a chemical reaction.

Chemical transformations require the breakage of certain covalent bonds within the reactant.

What does an enzyme do to the activation energy to help accelerate the reaction?

An enzyme will reduce the activation energy.

True or false: an enzyme can affect the free energy in a reaction (delta G)

False. Delta G is the same without/without an enzyme.

Give an example of a coupled reaction with ATP.

Hydrolysis of ATP drives the endergonic reaction of glucose to glucose-6-phosphate.

What is the active site on an enzyme? What does it do?

the place on the enzyme where the substrate binds. The enzyme then converts the substrate into products (catalyzing the rxn) by helping it stabilize the transition state (lowers the activation energy).

competitive vs noncompetitive inhibitors

competitive inhibitor —> binds to the active site and prevents the substrate from binding there.

noncompetitive inhibitor —> binds to a different site on the enzyme; it doesn't block substrate binding, but it causes other changes in the enzyme so that it can no longer catalyze the reaction efficiently.