Metabolic Functions and Erythropoiesis
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What is the purpose of renal clearance measurement?

  • To assess the overall health of the kidney tissues
  • To determine the volume of plasma cleared of a substance per minute (correct)
  • To measure blood pressure in the renal arteries
  • To quantify the amount of waste in the kidneys

    • Which substance indicates active secretion if its clearance is above 125 ml/min?

  • Electrolytes
  • Creatinine (correct)
  • Inulin
  • Glucose

    • What are the four groups of kidney function tests?

  • Filtration, absorption, secretion, excretion
  • Glomerular, tubular, blood analysis, urine analysis (correct)
  • Acid-base balance, electrolytes, volume, metabolic
  • Ultrasound, CT scan, MRI, biopsy

    • How is the Glomerular Filtration Rate (GFR) commonly estimated?

    <p>Using parameters of renal biomarkers in blood tests</p> Signup and view all the answers

    What happens to glucose in the renal system?

    <p>It is reabsorbed completely</p> Signup and view all the answers

    Which kidney function involves the preparation of an ultra filtrate?

    <p>Filtration</p> Signup and view all the answers

    What is a significant factor determining renal homeostasis?

    <p>Extracellular volume</p> Signup and view all the answers

    What does a urine analysis typically evaluate?

    <p>Volume, pH, specific gravity, osmolality</p> Signup and view all the answers

    What is the main reason GFR is considered the best measure of glomerular function?

    <p>It is determined by measuring the clearance of inulin, which is freely filtered but not secreted or reabsorbed.</p> Signup and view all the answers

    Which condition occurs when GFR decreases by 30% from normal levels?

    <p>Moderate renal insufficiency with asymptomatic patients</p> Signup and view all the answers

    What factor does NOT influence creatinine clearance (CC)?

    <p>Body metabolism</p> Signup and view all the answers

    How is creatinine clearance (CC) defined mathematically?

    <p>CC = UxV/P</p> Signup and view all the answers

    Which of the following is true regarding the estimated Glomerular Filtration Rate (eGFR)?

    <p>It can be calculated using the Cockcroft–Gault formula based on creatinine and individual characteristics.</p> Signup and view all the answers

    What is the primary product of gluconeogenesis in the renal cortex?

    <p>Glucose-6-phosphate</p> Signup and view all the answers

    Which substrate is predominantly utilized for gluconeogenesis in the liver?

    <p>Lactate</p> Signup and view all the answers

    What effect does reduced intracellular fluid pH have on renal gluconeogenesis?

    <p>Markedly increases the rate</p> Signup and view all the answers

    Which of the following is a major source of ATP production in the renal proximal convoluted tubule (PCT)?

    <p>Mitochondrial β-oxidation of free fatty acids</p> Signup and view all the answers

    What happens to free fatty acids (FFAs) delivered to the kidney in excess of its energy needs?

    <p>They are esterified and stored as triglycerides</p> Signup and view all the answers

    Which of the following substrates is utilized for gluconeogenesis specifically in the renal cortex?

    <p>α-ketoglutarate</p> Signup and view all the answers

    What is one of the differences in the regulation of gluconeogenesis between the liver and renal cortex?

    <p>The substrates utilized</p> Signup and view all the answers

    Which of the following statements is true regarding glycogen metabolism in the kidney?

    <p>Kidney has little phosphorylating capacity</p> Signup and view all the answers

    What is the primary site of ammoniagenesis in the kidneys?

    <p>Proximal convoluted tubule (PCT)</p> Signup and view all the answers

    Which enzyme is responsible for breaking down glutamine into glutamate and NH3?

    <p>Glutaminase</p> Signup and view all the answers

    What is the mechanism by which ammonium ions are secreted into the tubular lumen?

    <p>By substituting for H+ on the Na+/H+ exchanger</p> Signup and view all the answers

    How does the kidney primarily eliminate acidity?

    <p>By synthesizing and excreting NH3</p> Signup and view all the answers

    What characterizes metabolic acidosis?

    <p>Too much acid production or inadequate removal of acid</p> Signup and view all the answers

    Which of the following describes respiratory alkalosis?

    <p>Increased CO2 exhalation due to respiratory disorders</p> Signup and view all the answers

    What is a consequence of the kidneys' inability to form bicarbonate?

    <p>Metabolic acidosis</p> Signup and view all the answers

    Which of the following statements about acidosis and alkalosis is true?

    <p>Acidosis can lead to a blood pH below 7.4.</p> Signup and view all the answers

    What is the primary function of erythropoietin?

    <p>Increase hemoglobin and red blood cell synthesis</p> Signup and view all the answers

    What is angiotensinogen and where is it synthesized?

    <p>A precursor for angiotensin synthesized in the liver</p> Signup and view all the answers

    How does angiotensin II primarily affect the adrenal cortex?

    <p>It stimulates aldosterone release</p> Signup and view all the answers

    What role does renin play in the RAAS system?

    <p>It cleaves angiotensinogen to form Ang I</p> Signup and view all the answers

    What is the molecular weight of erythropoietin?

    <p>30.4 KDa</p> Signup and view all the answers

    What is the primary action of angiotensin-converting enzyme (ACE)?

    <p>To convert Ang I to Ang II</p> Signup and view all the answers

    Which of the following statements about angiotensin III is false?

    <p>It is more potent than Ang II in stimulating aldosterone secretion</p> Signup and view all the answers

    What effect does aldosterone have on potassium levels in the body?

    <p>It increases potassium excretion</p> Signup and view all the answers

    Which statement correctly describes angiotensin IV?

    <p>It stimulates AT4R and inhibits AT1R</p> Signup and view all the answers

    What triggers the release of renin from the juxtaglomerular apparatus?

    <p>Decreased renal perfusion pressure</p> Signup and view all the answers

    Study Notes

    Metabolic Functions

    • Carbohydrate, lipid, and protein metabolism are essential for producing energy and maintaining homeostasis.

    Erythropoietin Synthesis

    • Erythropoietin (EPO) is a peptide hormone with a molecular weight of 30.4 kDa, consisting of 165 amino acids.
    • Also known as haematopoietin or haemopoietin, EPO is primarily secreted by the kidneys in response to cellular hypoxia.
    • EPO stimulates erythropoiesis, promoting hemoglobin and red blood cell synthesis in the bone marrow.

    RAAS System

    • The Renin-Angiotensin-Aldosterone System (RAAS) regulates blood pressure and fluid balance through hormonal actions.
    • It stimulates the production of angiotensin II and aldosterone, crucial for maintaining electrolyte balance.

    Angiotensinogen (AGT)

    • AGT is a liver-synthesized α2-globulin with 485 amino acids, including a 33 amino-acid signal peptide.
    • It serves as the precursor for angiotensin and belongs to the serpin family (serpin A8).
    • The first 12 amino acids of AGT are critical for its activity.

    Renin

    • Renin is a 340 amino acid proteolytic enzyme (37 kDa) released from the juxtaglomerular apparatus of the kidney in response to decreased renal perfusion pressure.
    • It cleaves AGT to form angiotensin I (Ang I).

    Angiotensin-Converting Enzyme (ACE)

    • ACE converts Ang I to angiotensin II (Ang II) by removing two C-terminal residues, primarily occurring in the lungs.
    • ACE is also present in endothelial cells, kidney epithelial cells, and the brain.

    Angiotensin II

    • Ang II is an octapeptide and a potent vasoconstrictor, acting on AT1R and AT2R receptors.
    • It promotes aldosterone release, influencing sodium and potassium homeostasis.
    • Ang II stimulates ADH secretion, further enhancing water retention.
    • Metabolized to Ang III and angiotensin 1-7 in tissues, which can catabolize into smaller peptides.

    Angiotensin III

    • Ang III is formed from Ang II by aminopeptidase A (APA) and binds to AT1R and AT2R.
    • It plays a significant role in central regulation of hypertension and vasopressin release.

    Angiotensin IV

    • Formed from Ang III by aminopeptidase N (APN), Ang IV binds to AT4R and AT2R while inhibiting AT1R.

    Renal Gluconeogenesis

    • The renal cortex has gluconeogenic enzymes (including glucose-6-phosphatase), facilitating glucose production from pyruvate, lactate, and other substrates.
    • Renal gluconeogenesis primarily serves to regulate blood pH, especially during acidosis.

    Lipid Metabolism

    • Kidney's PCT utilizes mitochondrial β-oxidation of free fatty acids (FFA) for ATP production, significantly contributing to renal oxygen consumption.
    • Excess circulating FFAs can be stored as triglycerides in lipid droplets.

    Ammoniagenesis

    • Occurs in the proximal convoluted tubule, generating ammonium from glutamine via glutaminase and glutamate dehydrogenase.
    • Ammonium ions help buffer urinary pH and are excreted in exchange for sodium ions.

    Acid-Base Balance

    • Disturbances in acid-base balance lead to acidosis (pH < 7.4) or alkalosis (pH > 7.4).
    • Metabolic and respiratory acidosis/alkalosis arise from different physiological causes.

    Kidney Function Summary

    • Kidneys filter, reabsorb, and synthesize key substances like glucose and hormones, including erythropoietin and renin.
    • They play a critical role in maintaining extracellular volume, acid-base status, blood pressure, and electrolyte balance.

    Renal Function Biomarkers

    • Kidney function tests are crucial for evaluating renal performance, categorized into glomerular function tests, tubular function tests, blood analysis, and urine analysis.

    Glomerular Filtration Rate (GFR)

    • GFR assesses glomerular function and is commonly estimated through inulin clearance.
    • Normal GFR is vital for renal health, with decreases indicating renal insufficiency.

    Creatinine Clearance (CC) Test

    • Creatinine clearance estimates the volume of plasma cleared of creatinine per minute, reflecting kidney efficiency.
    • Normal CC ranges from 120-145 ml/min, influenced by muscle mass and other factors.

    Diagnostic Importance

    • Monitoring GFR and CC values can help identify and manage renal conditions, guiding treatment and assessment of kidney health.

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    Description

    This quiz covers essential metabolic functions, specifically focusing on carbohydrate, lipid, and protein metabolism. It also explores erythropoietin synthesis, its role in red blood cell production, and details on the RAAS system. Test your knowledge on these vital biological processes!

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