Free Energy & Thermodynamics
What is the amount of energy available to do work in a biological system?
Free energy (Gibbs free energy)
What molecule most commonly drives endergonic reactions in cells?
ATP
Oxidation involves the loss of what?
Electrons
What are the three main sources of fuel intake?
Carbohydrates, proteins and lipids
Which organ acts as the metabolic hub for absorbed nutrients?
Liver
What is the measure of disorder caused by the continual loss of energy during transformations?
Entropy
What do enzymes lower to increase the rate of a reaction?
Activation energy
What is the final electron acceptor in oxidative phosphorylation?
Oxygen (O₂)
Which dietary fuel provides the greatest amount of energy per gram?
Fats
What is the primary storage polysaccharide in animals?
Glycogen
A reaction has a negative ΔG and releases energy. What type of reaction is it?
Exergonic reaction
In ATP + glucose → glucose 6-phosphate + ADP, what bond-breaking event is directly coupled to phosphate addition onto glucose?
Breaking of a phosphate bond on ATP
Which electron carrier is primarily associated with catabolic pathways?
NADH
Which enzyme deficiency causes lactose intolerance?
Lactase
What fuel does the brain primarily rely on under normal conditions?
Glucose
A reaction has a positive ΔG. What must happen before it can proceed spontaneously in a cell?
It must be coupled to an exergonic reaction so that the overall ΔG is negative.
What process couples ATP synthesis to diffusion of protons across a membrane gradient?
Chemiosmosis
Which metabolic pathway produces NADPH in plants and animals?
Pentose phosphate pathway
Which three enzymes complete the final digestion of starch-derived carbohydrates to simple sugars in the small intestine?
Maltase, α-glucosidase and α-limit dextrinase.
During fasting, what process in the liver raises blood glucose using amino acids from muscle?
Gluconeogenesis
Glucose → glucose 6-phosphate has ΔG = +13.8 kJ/mol and ATP hydrolysis has ΔG = −30.5 kJ/mol. What is the overall ΔG when the reactions are coupled?
−16.7 kJ/mol
Place these events in order: proton pumping, ATP production by oxidative phosphorylation, electron transport chain.
Electron transport chain → proton pumping → oxidative phosphorylation (ATP production).
Name the three universal electron carriers that are reduced during redox reactions.
NADH, NADPH and FADH₂
A carbohydrate is resistant to digestion and absorption in the small intestine but may undergo complete or partial fermentation in the large intestine. What is it?
Dietary fibre
During fasting, what sequence occurs after liver glycogen is depleted?
Muscle protein breakdown → amino acids exported to the liver → gluconeogenesis increases blood glucose