lecture 23 and 24 objectives Flashcards
Define metabolism, anabolism, and catabolism, and provide examples of anabolic and catabolic reactions.
o Metabolism is the sum of all chemical reactions that occur within a cell or organism, including those involved in the synthesis and breakdown of molecules to produce energy.
o Anabolism is the process of building larger molecules from smaller ones, requiring energy input. Example: Protein synthesis, where amino acids are assembled into proteins.
o Catabolism is the breakdown of larger molecules into smaller ones, releasing energy. Example: Glycolysis, where glucose is broken down into pyruvate to release energy.
Compare and contrast the roles of enzymes and cofactors in metabolic processes.
o Enzymes are proteins that catalyze biochemical reactions, speeding up metabolic processes by lowering activation energy. They are highly specific to substrates.
o Cofactors are non-protein molecules that assist enzymes in their catalytic activity. These can be inorganic ions (e.g., magnesium, zinc) or organic molecules (coenzymes like NAD+). Enzymes without cofactors are often inactive.
Explain the roles of coenzyme A, nicotinamide adenine dinucleotide (NAD), and flavin adenine dinucleotide (FAD) in metabolism.
o Coenzyme A is involved in the transport of acyl groups (e.g., acetyl groups) in metabolic reactions, such as in the citric acid cycle (Krebs cycle).
o NAD+ is a coenzyme that carries electrons in redox reactions, such as in glycolysis and the citric acid cycle, and is reduced to NADH.
o FAD is another electron carrier, similar to NAD+, that is reduced to FADH2 during the citric acid cycle.
Describe the processes of oxidation, reduction, decarboxylation, deamination, and phosphorylation.
o Oxidation is the loss of electrons or hydrogen atoms, often associated with the addition of oxygen to a molecule (e.g., glucose oxidation in cellular respiration).
o Reduction is the gain of electrons or hydrogen atoms, often associated with the removal of oxygen.
o Decarboxylation is the removal of a carboxyl group (COOH), releasing carbon dioxide. Example: In the citric acid cycle, pyruvate undergoes decarboxylation to form acetyl-CoA.
o Deamination is the removal of an amino group (NH2) from an amino acid, leading to the formation of ammonia. Example: In protein metabolism, excess amino acids undergo deamination.
o Phosphorylation is the addition of a phosphate group (PO4) to a molecule, often activating or deactivating enzymes. Example: ATP is involved in many phosphorylation reactions.
what does Aerobic respiration do
Aerobic respiration involves the complete oxidation of glucose in the presence of oxygen to produce ATP.
Describe the processes of aerobic respiration (e.g., citric acid [Krebs, tricarboxylic acid or TCA] cycle, electron transport chain) in the oxidation of glucose to generate ATP.
o Glycolysis: Glucose is broken down into two molecules of pyruvate, generating 2 ATP and 2 NADH.
o Pyruvate Decarboxylation: Each pyruvate is converted to acetyl-CoA, releasing CO2 and generating NADH.
o Citric Acid Cycle (Krebs cycle): Acetyl-CoA enters the cycle, generating 4 NADH, 1 FADH2, and 1 ATP (per turn) and releasing CO2.
o Electron Transport Chain (ETC): NADH and FADH2 donate electrons to the ETC in the inner mitochondrial membrane. The flow of electrons pumps protons (H+) across the membrane, creating a proton gradient that drives ATP synthesis via ATP synthase. Oxygen is the final electron acceptor, forming water. Gives off 32 ATP, 6 water, 2 FAD, 10NAD
what is anaerobic respiration
Anaerobic respiration occurs when oxygen is unavailable, and glucose is metabolized through glycolysis to produce ATP.
Describe the processes of anaerobic respiration (e.g., glycolysis) in the oxidation of carbohydrates to generate ATP.
In glycolysis, one molecule of glucose is converted into two molecules of pyruvate, generating 2 ATP and 2 NADH.
In the absence of oxygen, pyruvate is converted into lactate (in animals) or ethanol and CO2 (in yeast) through lactic acid fermentation or alcoholic fermentation, respectively. This allows NAD+ to be regenerated for further glycolysis.
Describe metabolic pathways that produce or store glucose (e.g., glycogenesis, glycogenolysis, gluconeogenesis)
o Glycogenesis is the process of synthesizing glycogen from glucose, which occurs in the liver and muscles when glucose is abundant.
o Glycogenolysis is the breakdown of glycogen into glucose-1-phosphate, which can be converted to glucose-6-phosphate and used for energy during fasting or exercise.
o Gluconeogenesis is the synthesis of glucose from non-carbohydrate precursors (e.g., amino acids, lactate) mainly in the liver during fasting.
Describe the anabolic and catabolic processes of fat metabolism (e.g., lipolysis, lipogenesis) and how these processes interact with carbohydrate metabolism.
o Lipolysis is the breakdown of triglycerides into glycerol and fatty acids, which can be used for energy production.
o Lipogenesis is the process of synthesizing fatty acids and triglycerides from acetyl-CoA and glycerol, often in the liver and adipose tissue.
o Fat metabolism interacts with carbohydrate metabolism through processes like β-oxidation, where fatty acids are broken down to acetyl-CoA, which can enter the citric acid cycle for ATP production. Additionally, excessive carbohydrate intake can promote lipogenesis, and fasting can stimulate lipolysis.
Describe the anabolic and catabolic processes of protein metabolism (e.g., deamination, transamination) and how these processes interact with carbohydrate metabolism.
o Protein catabolism involves the breakdown of proteins into amino acids, which can undergo deamination (removal of the amino group) and be converted into intermediates like pyruvate or acetyl-CoA for energy production.
o Transamination is the transfer of an amino group from one amino acid to a keto acid, facilitating the synthesis of non-essential amino acids.
o Protein metabolism interacts with carbohydrate metabolism, as amino acids can be converted into glucose through gluconeogenesis or can enter the citric acid cycle for ATP production.
Compare and contrast carbohydrate, fat, and protein metabolism in the fed (absorptive) and fasted (post-absorptive) states
Fed state (absorptive): After a meal, insulin levels rise, promoting the storage of glucose as glycogen (glycogenesis), the synthesis of fats (lipogenesis), and protein synthesis.
Carbohydrates are mainly stored as glycogen, fats as triglycerides, and proteins are synthesized for growth and repair.
Fasted state (post-absorptive): In the absence of food, glucagon levels rise, stimulating the breakdown of glycogen into glucose (glycogenolysis), the release of fatty acids from adipose tissue (lipolysis), and the breakdown of proteins for gluconeogenesis.
The body shifts to using stored energy (glycogen, fat, and proteins) to maintain blood glucose levels and provide energy.
