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Questions and Answers
What is the role of lipoprotein lipase in relation to chylomicrons?
What is the role of lipoprotein lipase in relation to chylomicrons?
What happens to chylomicrons after they have delivered triglycerides to the tissues?
What happens to chylomicrons after they have delivered triglycerides to the tissues?
How does VLDL contribute to lipid metabolism?
How does VLDL contribute to lipid metabolism?
What triggers the release of triglycerides from VLDL into tissues?
What triggers the release of triglycerides from VLDL into tissues?
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Which form of lipoprotein is primarily responsible for cholesterol delivery to extrahepatic tissues?
Which form of lipoprotein is primarily responsible for cholesterol delivery to extrahepatic tissues?
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What is the primary function of hydroxyacyl-CoA dehydrogenase in fatty acid metabolism?
What is the primary function of hydroxyacyl-CoA dehydrogenase in fatty acid metabolism?
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What initiates the process of fatty acid synthesis when glucose levels are excessive?
What initiates the process of fatty acid synthesis when glucose levels are excessive?
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During the conversion of citrate to Acetyl-CoA in the cytoplasm, which enzyme is responsible for splitting citrate?
During the conversion of citrate to Acetyl-CoA in the cytoplasm, which enzyme is responsible for splitting citrate?
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What is the rate-limiting step in fatty acid biosynthesis?
What is the rate-limiting step in fatty acid biosynthesis?
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Which of the following correctly describes the transformation of oxaloacetate after it cannot return to the mitochondria?
Which of the following correctly describes the transformation of oxaloacetate after it cannot return to the mitochondria?
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Study Notes
Hormone Synthesis and Degradation
- Hormones are biochemical mediators produced by endocrine glands, acting on target organs/receptors
- Hormones can be synthesized from various precursors, including amino acids (e.g., tyrosine, tryptophan) and lipids (e.g., cholesterol)
- Hormones have distinct structures and mechanisms of action, impacting target cell function
- Hormones’ synthesis and degradation are tightly regulated through feedback mechanisms
Hormone Classification
- Amino acid-derived hormones: Catecholamines (e.g., epinephrine, norepinephrine), thyroid hormones (e.g., thyroxine), and melatonin
- Peptide hormones: A variety of hormones with diverse functions (e.g., insulin, glucagon, oxytocin, ADH)
- Steroid hormones: Derived from cholesterol; include sex hormones (e.g., testosterone, estrogen, progesterone) and adrenal hormones (e.g., cortisol, aldosterone)
- Other hormones: Derived from arachidonic acid, including prostaglandins, thromboxanes, and leukotrienes
Hormone Action
- Ligand-gated ion channels: Hormones binding to receptors alters ion permeability, leading to rapid changes in membrane potential (e.g., neurotransmitters)
- G protein-coupled receptors: Hormones trigger intracellular signaling cascades via G proteins, activating enzymes (e.g., adenylate cyclase, phospholipase C) and generating secondary messengers (e.g., cAMP, DAG, IP3)
- Enzyme-linked receptors: Hormones act as substrates for receptor enzymes, often initiating signaling cascades (e.g., receptor tyrosine kinases)
- Nuclear hormone receptors: Hormones directly affect gene expression by binding to receptors within the nucleus (e.g., steroids)
Hormone Regulation and Feedback
- Feedback mechanisms constantly regulate hormone levels to maintain homeostasis
- Direct feedback: The hormone produced affects the gland that produced the hormone (e.g., glucose and insulin)
- Indirect feedback: Other hormones in a signaling pathway affect the production of the original hormone (e.g., hypothalamic-pituitary-adrenal axis)
- Regulation through receptor numbers: Too much hormone leads to fewer receptors (downregulation) and vice-versa (upregulation)
Disorders of Hormone Action
- Hyposecretion: Insufficient hormone production
- Hypersecretion: Excessive hormone production.
- Examples include diabetes insipidus, Cushing's syndrome, and dwarfism (impaired growth hormone production)
Metabolism of Hormones
- Hormones are frequently metabolized in the liver and kidneys or other target tissues
- Degradation methods include various chemical processes
- Metabolism is important for regulating hormone levels and signaling pathways
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