PHAR 412 Bioenergetics: Gibbs Free Energy, Glycolysis, and Fuel Storage

What is bioenergetics?

The study of the transformation of energy in living organisms.

What is the difference between direct chemical combustion of glucose and cellular combustion?

Direct combustion produces carbon dioxide and heat, while cellular combustion produces ATP and involves substrate-level and oxidative phosphorylation.

What is free energy change (∆G)?

The change in energy that occurs during a reaction, indicating the spontaneity of the reaction.

What is standard free energy change (∆Go′)?

The free energy change measured under standard conditions, providing a fixed value for each reaction.

What does the equilibrium constant (Keq) represent?

The ratio of product concentrations to substrate concentrations at equilibrium.

What is the reaction quotient (Q)?

The ratio of product concentrations to substrate concentrations at any point in a reaction.

How can you categorize a reaction based on its ∆G value?

A reaction is exergonic if ∆G is negative and endergonic if ∆G is positive.

What is Le Chatelier's Principle?

A principle stating that if a system at equilibrium is disturbed, the system will shift to counteract the disturbance.

What are the storage forms of glucose?

Glycogen and starch are the primary storage forms of glucose.

What is the net reaction formula for glucose combustion?

Glucose + Oxygen → Carbon dioxide + Heat.

What is the significance of ΔG0' in predicting reaction favorability?

It indicates the favorability of a reaction; more negative values suggest a greater tendency for products to form.

How does ΔG0' relate to reaction speed?

ΔG0' does not indicate reaction speed; enzymes can speed up reactions without changing ΔG0'.

What does a negative ΔG value indicate about a reaction?

It indicates that the reaction will spontaneously proceed in the forward direction.

What does the term 'exergonic reaction' mean?

A reaction that releases energy, often in the form of heat or work.

How can you calculate the product/substrate ratio at equilibrium?

Using the ΔG0' value and the equilibrium expression.

What is the relationship between ΔG0' and Keq?

ΔG0' is related to Keq; a more negative ΔG0' corresponds to a larger Keq.

What is the formula for calculating ratios from ΔG0' values?

The ratio can be derived from the exponential function of ΔG0' values.

What does a ΔG0' value of -10 indicate?

It indicates a very high product/substrate ratio at equilibrium (20999307).

What is the unit of ΔG0'?

It is typically expressed in kcal/mol or kJ/mol.

What is the role of enzymes in reactions?

Enzymes lower the activation energy, increasing the speed of the reaction without altering ΔG.

What does the term 'activation energy' refer to?

The minimum energy required for a reaction to occur.

What is the significance of the Gibbs Free Energy in metabolic reactions?

It helps predict the direction and spontaneity of biochemical reactions.

How does temperature affect ΔG0'?

Changing temperature can alter the ΔG0' value and thus the favorability of a reaction.

What is the importance of understanding metabolic pathways?

It is crucial for comprehending how energy is produced and utilized in biological systems.

What is substrate-level phosphorylation?

A process of generating ATP by transferring a phosphate group directly to ADP from a substrate.

What is oxidative phosphorylation?

A metabolic pathway that uses energy released by the electron transport chain to produce ATP.

What is the product/substrate ratio at equilibrium for the reaction involving Glucose 6-Phosphate and Fructose 6-Phosphate?

The equilibrium ratio is 2.74.

What happens to the ratio of F-6-P/G-6-P if more Fructose 6-Phosphate is added?

The ratio will be higher than 2.74, or Q will be higher than Keq.

What occurs when the reaction quotient Q exceeds the equilibrium constant Keq?

The reaction will proceed backward until it reaches the equilibrium ratio again.

What is the standard condition value of RT given in the notes?

RT is 0.593.

What does ΔG represent in the context of chemical reactions?

ΔG represents the change in Gibbs Free Energy.

What is the relationship between ΔG and the spontaneity of a reaction?

If ΔG is negative, the reaction proceeds spontaneously in the forward direction.

What does the reaction quotient (Q) indicate?

Q indicates the ratio of products to reactants at any point in the reaction.

How does the equilibrium constant (Keq) differ from the reaction quotient (Q)?

Keq is the ratio of products to reactants at equilibrium, while Q can be at any point in the reaction.

What is the significance of the Gibbs Free Energy value at equilibrium?

At equilibrium, ΔG is equal to zero.

What happens to the Gibbs Free Energy value if the reaction is spontaneous?

The Gibbs Free Energy value will be negative.

What does a positive ΔG indicate about a reaction?

A positive ΔG indicates that the reaction is non-spontaneous in the forward direction.

What is the effect of temperature on the equilibrium constant?

The equilibrium constant changes with temperature.

What is the formula for calculating the Gibbs Free Energy change?

ΔG = ΔG° + RT ln(Q).

What does it mean if the equilibrium constant is greater than 1?

It indicates that products are favored at equilibrium.

What does it mean if the equilibrium constant is less than 1?

It indicates that reactants are favored at equilibrium.

What is the effect of adding reactants to a system at equilibrium?

Adding reactants will shift the equilibrium to the right, favoring product formation.

What is the effect of removing products from a system at equilibrium?

Removing products will shift the equilibrium to the right, favoring product formation.

What does the term 'standard conditions' refer to?

Standard conditions refer to a set of specific conditions (usually 1 M concentration, 1 atm pressure, and 25°C) under which thermodynamic values are measured.

What is the relationship between standard Gibbs Free Energy change and equilibrium?

Standard Gibbs Free Energy change indicates the favorability of a reaction under standard conditions.

What does a reaction with a ΔG° value of zero imply?

It implies that the reaction is at equilibrium under standard conditions.

What is the significance of the equilibrium ratio in biochemical reactions?

The equilibrium ratio determines the concentrations of reactants and products at equilibrium.

What happens to excess glucose in the body?

Excess glucose is taken up by the liver and converted into glycogen and triglycerides (fat).

What is glycogen?

Glycogen is a large, insoluble glucose polymer stored in cells as an emergency supply of glucose.

How long can the liver use glycogen to replenish blood glucose?

The liver can use glycogen to replenish blood glucose for up to about 24 hours after dietary fuels are depleted.

What is the energy cost of adding glucose to glycogen?

There is an energy cost of about 2 ATP for each glucose molecule added to the glycogen polymer.

What is the benefit of storing glucose as glycogen instead of free glucose?

Storing glucose as glycogen reduces osmotic pressure in cells.

How is fat synthesized from glucose?

Fat is synthesized from excess glucose mostly in the liver and stored in adipose tissue.

What is the energy loss when glucose is converted into fat?

About 20% of glucose's free energy is lost during conversion into fat.

What is the benefit of storing energy as fat?

Fat is an efficient energy storage form, with a single triglyceride molecule containing the energy of more than 10 glucose molecules.

Why do triglycerides take up less space than glycogen?

Triglycerides are hydrophobic and cluster together as lipid droplets, requiring less space and water than glycogen.

How much glycogen would be needed to store the same energy as 18 kg of fat?

It would take approximately 170 kg of glycogen to hold the same energy as 18 kg of fat.

What type of reactions move forward in glycolysis?

Glycolytic reactions move forward through push and pull mechanisms.

What is the role of enzymes in glycolytic reactions?

Enzymes facilitate the conversion of substrates in glycolytic reactions.

What is the importance of cellular fuel storage?

Cellular fuel storage is crucial for maintaining energy balance and providing energy during periods of fasting.

What is the difference between endergonic and exergonic reactions?

Endergonic reactions require energy input, while exergonic reactions release energy.

What is the significance of metabolic pathways?

Metabolic pathways are essential for converting nutrients into energy and building blocks for cellular functions.

What happens during a coupled reaction?

In a coupled reaction, an exergonic reaction drives an endergonic reaction, allowing energy transfer.

What factors influence the direction of metabolic reactions?

The direction of metabolic reactions is influenced by substrate availability, enzyme activity, and energy requirements.

What is the role of ATP in cellular metabolism?

ATP serves as the primary energy currency in cells, powering various metabolic processes.

How do cells manage energy supply and demand?

Cells regulate energy supply and demand through feedback mechanisms and metabolic pathways.

What is the relationship between glycolysis and cellular respiration?

Glycolysis is the first step in cellular respiration, breaking down glucose to produce ATP.

What is the role of the liver in glucose metabolism?

The liver plays a central role in glucose metabolism, regulating blood glucose levels and storing glycogen.

How do hormonal signals affect fuel storage?

Hormonal signals, such as insulin and glucagon, regulate fuel storage and release in the body.

What is the impact of high glucose levels on cellular osmotic pressure?

High glucose levels can increase osmotic pressure, potentially leading to cellular damage if not regulated.

What is the significance of lipid droplets in adipose cells?

Lipid droplets in adipose cells store energy efficiently and help maintain cellular homeostasis.

What is the primary function of triglycerides?

Triglycerides primarily function as long-term energy storage molecules in the body.