W4 Energy & Metabolism Flashcards
Define the first and second laws of thermodynamics.
How do these laws relate to the concept of entropy?
First Law of Thermodynamics: Energy cannot be created or destroyed; it can only be transferred or transformed. This law is also known as the principle of energy conservation
Second Law of Thermodynamics: In any energy transfer or transformation, the total entropy (disorder) of an isolated system always increases over time. This means that while order can be created locally (such as in living cells), the overall disorder in the universe increases
Relation to Entropy: The second law implies that processes tend to move towards increased entropy. In biological systems, energy input is required to maintain or increase order locally, while the overall entropy of the system increases.
Explain the role of enzymes in metabolic pathways.
How do they affect activation energy and reaction rates?
Enzymes are biological catalysts that speed up metabolic reactions by lowering the activation energy required for the reactions to proceed
They work by binding to substrates, stabilizing the transition state, and thereby reducing the energy barrier needed for the reaction
Enzymes do not change the equilibrium of a reaction but make it reach equilibrium faster. They help in finding substrates quickly due to rapid diffusion and the availability of substrates
What is Gibbs free energy (ΔG) and how does it determine whether a reaction is spontaneous or nonspontaneous?
Gibbs Free Energy (ΔG): It is a thermodynamic quantity defined as ΔG = ΔH - TΔS, where ΔH is the change in enthalpy, T is the temperature in Kelvin, and ΔS is the change in entropy
Spontaneous Reactions: If ΔG is negative, the reaction is spontaneous and will proceed without external energy input
Nonspontaneous Reactions: If ΔG is positive, the reaction is nonspontaneous and requires energy input to proceed
Describe the process of glycolysis
- how much do you need to start?
- how much energy does it generate?
-what is the net gain?
How does it relate to ATP production?
Glycolysis is the breakdown of glucose into two molecules of pyruvate, occurring in the cytosol
Initial Investment: It requires an investment of 2 ATP molecules to initiate the process
Energy Generation: In the subsequent reactions, 4 ATP molecules are produced through substrate-level phosphorylation, and 2 NADH molecules are generated
Net Result: The net gain is 2 ATP and 2 NADH per molecule of glucose
What happens to pyruvate in the presence and absence of oxygen?
Presence of Oxygen = TCA cycle
Pyruvate is transported to the mitochondria, where it is converted to acetyl-CoA and enters the citric acid cycle (TCA cycle). This process leads to further production of ATP through oxidative phosphorylation
Absence of Oxygen: Pyruvate undergoes fermentation in the cytosol, resulting in lactate (in animals) or ethanol (in yeast). This process regenerates NAD+ to allow glycolysis to continue but produces only 2 ATP per glucose molecule
How is glycolysis related to ATP production?
Relation to ATP Production: Glycolysis is the first step in cellular respiration and provides the pyruvate and NADH needed for further ATP production in the mitochondria.
Where does the electron transport, TCA cycle, oxidative phosphorylation, protein gradient, pyruvate formation and glycolysis happen?
- electron transport = inner MM
- TCA cycle = mitochondrial matrix
- oxidative phos. = inner MM
- proton gradient = inner MM
- pyruvate = cytosol
- glycolysis = cytosol
- Explain oxidative phosphorylation and its role in ATP production
Electron Transport Chain: NADH and FADH2 donate electrons to the chain, which are transferred through various protein complexes, ultimately reducing oxygen to water.
= in the inner mitochondrial membrane
Proton Gradient: The electron transfer creates a proton gradient across the membrane, which drives protons through ATP synthase
= inner mitochondrial membrane
ATP Synthase: The movement of protons through ATP synthase generates mechanical energy, which is used to phosphorylate ADP to ATP
Role in ATP Production: This is the primary method for generating ATP, producing approximately 32 ATP molecules from one molecule of glucose.
How does the body handle excess energy, and what role does glycogen play in energy storage?
Excess Energy Handling: Excess energy is stored as glycogen in the liver and muscles or converted to fat for long-term storage
Glycogen: Glycogen is a polysaccharide stored in the liver and muscles that serves as a readily available source of glucose when needed, such as between meals or during intense physical activity.
What is the difference between NADH and NADPH in cellular metabolism?
NADH: Primarily involved in catabolic reactions and energy production, such as the electron transport chain in oxidative phosphorylation
NADPH: Used mainly in anabolic reactions, such as biosynthesis of lipids and nucleic acids. It acts as a reducing agent in these processes
