Midterm Flashcards
(81 cards)
What is glycolysis?
The metabolic process that breaks down glucose into two molecules of pyruvate
It occurs in the cytoplasm and generates ATP and NADH.
This pathway provides energy for both aerobic and anaerobic conditions
What is the importance of the Krebs cycle?
Essential for energy production, generating NADH and FADH₂
It occurs in the mitochondrial matrix and oxidizes Acetyl-CoA to CO₂
This cycle provides intermediates for biosynthsis and ATP generation
How does the electron transport chain function?
Transfers electrons from NADH and FADH₂, creating a proton gradient
This proton gradient drive ATP synthesis via ATP synthase
Oxygen is the final electron acceptor, forming water.
Define oxidative phosphorylation.
Process where ATP is synthesized using ETC and chemiosmosis
Electrons pass through the ETC, pumping protons into the intermembrane space
ATP synthase utilizes the proton gradient to generate ATP
Describe the significance of gluconeogenesis.
Synthesizes glucose from non-carbohydrate sources like amino acids and lactate
It mainly occurs in the liver and kidneys during fasting or low glucose levels
It ensures a continuous glucose supply for the brain and the RBCs
What are the key enzymes of glycolysis?
Hexokinase, phosphofructokinase-1 (PFK-1), and pyruvate kinase
Hexokinase: phosphorylates glucose, committing it to glycolysis
PFK-1: regulated glycolysis
Pyruvate kinase: catalyze the final ATP-producing step
Explain the function of hexokinase in glucose metabolism.
Phosphorylates glucose into glucose-6-phosphate in the 1st step of glycolysis
This prevents glucose from diffusing out of the cell
It has a curial role in regulating glucose utilization
What is the Cori cycle?
Recycles lactate produced by anaerobic glycolysis in muscles back to glucose
Lactate is converted into glucose in the liver and returned to muscles
This prevents lactic acid buildup and maintains glucose supply
How does the pentose-phosphate pathway work?
Generates NADPH and ribose-5-phosphate
NADPH is used for biosynthesis, while ribose-5-phosphate is essential for nucleotide synthesis
It consists of oxidative and non-oxidative phases
Describe the regulation of glycolysis.
Regulated by allosteric control of hexokinase, PFK-1, and pyruvate kinase
ATP and citrate inhibit PFK-1, while AMP and fructose-2,6-bisphosphate activate it
Insulin promotes glycolysis while glucagon inhibits it
What is the role of NADH in metabolism?
Electron carrier that donates electrons to the ETC for ATP production
Generated during glycolysis, Krebs cycle, and beta-oxidation
it is crucial for oxidative phosphorylation and energy metabolism
Define substrate-level phosphorylation.
Direct synthesis of ATP from ADP and a phosphorylated substrate
Occurs in glycolysis and the Krebs cycle
Unlike oxidative phosphorylation, it doesn’t require oxygen
How does insulin regulate glucose metabolism?
Stimulates glucose uptake, glycolysis, and glycogenesis
It inhibits gluconeogenesis and glycogenolysis
It lowers blood glucose levels by increasing glucose utilization
What are the key differences between aerobic and anaerobic respiration?
Aerobic requires oxygen and produces more ATP
38 ATP per Glucose
Anaerobic occurs without oxygen 2 ATP per Glucose and generates lactate as a byproduct.
Explain the metabolic fate of pyruvate.
Enters the Krebs cycle as Acetyl-CoA under aerobic conditions; converted to lactate under anaerobic conditions
Can also serve as a precursor for gluconeogenesis.
What is the role of glycogen phosphorylase in glycogenolysis?
Breaks down glycogen into glucose-1-phosphate
Activated by glucagon in the liver and epinephrine in muscles
It ensures glucose availability during fasting or exercise
How is the HMP pathway linked to nucleic acid synthesis?
Provides ribose-5-phosphate for nucleotide biosynthesis
Also generates NADPH, essential for DNA synthesis
it is crucial for rapidly dividing cells
Describe the biochemical significance of the TCA cycle.
Central to aerobic metabolism and ATP generation
Produces NADH and FADH₂, driving oxidative phosphorylation
Provides intermediates for biosynthetic pathways
What are the key regulatory steps of glycolysis?
Involves hexokinase, PFK-1, and pyruvate kinase
These enzymes are subject to allosteric regulation and hormonal control
ATP inhibits PFK-1, insulin promotes glycolysis
Explain the process of glycogenesis.
Synthesis of glycogen from glucose
Glycogen synthase elongates chains, while the branching enzyme introduces branches
It is promoted by insulin
What is the significance of the malate-aspartate shuttle?
Transfers NADH electrons into mitochondria
Helps maintain NAD+/NADH ratio in glycolysis
Increases ATP yield in aerobic respiration
How does lactate accumulation affect metabolism?
Leads to acidosis and muscle fatigue
Cleared via the Cori cycle in the liver
It is converted back into glucose by gluconeogenesis
Describe the structure and function of ATP synthase.
Enzyme in the mitochondrial membrane that synthesizes ATP using the proton gradient from ETC
Consists of F₀ (proton channel) and F₁ (ATP-producing unit).
What are the consequences of glucose-6-phosphatase deficiency?
Leads to glycogen storage disease type I (Von Gierke’s disease)
The liver cannot release glucose, causing hypoglycemia
Excess glycogen accumulates, leading to liver enlargement
