Biology 1 - Metabolism Chapter 8 Quiz

Biology 1 - Cells, Molecular Biology and Genetics (Biol 1000)

• Course instructor: Dr. Michael Cardinal-Aucoin
• Course offering: Winter 2025
• Course code: Biol 1000

Metabolism (Chapter 8)

• Metabolism is the totality of an organism's chemical reactions
• Metabolism transforms matter and energy
• Metabolism is an emergent property of life that arises from interactions between molecules within the cell.
• Metabolic pathways are organized into steps catalyzed by specific enzymes, which are typically regulated at the level of one of these enzymes.

Overview of Metabolism

• Catabolism breaks down substances, such as in digestion
• Anabolism builds up substances, for example protein synthesis in muscle
• Catabolic pathways release energy by breaking down complex molecules into simpler compounds
• Cellular respiration involves the breakdown of glucose in the presence of oxygen to form CO2, water, and ATP.

Basic Thermodynamics and Energy

• All chemical systems (e.g., organisms, cells) contain energy, which is also referred to as enthalpy (H).
• Cells convert energy from one form to another. Forms include kinetic energy (movement), chemical energy (stored in chemical bonds), light energy, and electrochemical potential energy (e.g., concentration gradient).
• Energy can be transferred or transformed but it cannot be created or destroyed (First Law of Thermodynamics).
• During every energy transfer or transformation, some energy is unusable and is often lost as heat (Second Law of Thermodynamics).
• Entropy is a measure of disorder.
• Gibbs free energy (ΔG) is the proportion of a system's energy that can perform work. A negative ΔG means the reaction is spontaneous. A positive ΔG means the reaction is non-spontaneous.

Exergonic and Endergonic Reactions

• Exergonic reactions release energy (ΔG < 0) and are spontaneous.
• Endergonic reactions absorb energy (ΔG > 0) and are non-spontaneous.
• Gibbs free energy is the difference in energy between reactants and products.

Enzymes

• Enzymes are proteins that accelerate a chemical reaction by decreasing the activation energy (Ea).
• Enzymes do not alter the free energy (ΔG) of the reaction.
• The activation energy (Ea) is the minimum amount of energy required before collisions between reactants will give rise to products.
• The active site is the region of an enzyme where the substrate binds.
• Induced fit of a substrate allows the enzyme to better catalyze the reaction.
• Enzymes can be affected by cofactors and coenzymes.
• Enzymes are specific and can exhibit different optimal conditions such as temperature and pH.
• Feedback inhibition involves the end product of a metabolic pathway inhibiting an earlier step in the pathway.
• Enzymes can be regulated through phosphorylation.

Enzyme Action

• Various factors can affect enzyme activity, including substrate concentration, competitive inhibition, allosteric activation, and phosphorylation.

ATP

• ATP is the energy currency of the cell and is used to do work.
• Cells use ATP to do chemical work (e.g., polymerization), transport work (e.g., transporting substances), and mechanical work (e.g., moving structures like cilia).
• ATP drives endergonic reactions by the reaction of ATP hydrolysis (breaking down)
• ATP is a renewable resource regenerated in the cell by adding a phosphate group to ADP.