Alterations in Intracellular Functions and Fluid and Solute Balance

A curated set of practice questions and answers covering key concepts from Alterations in Intracellular Functions and Fluid and Solute Balance, including osmosis/osmolality, acid-base disorders, hypoxia, metabolic pathways, RAAS/ADH/SIADH, electrolyte disturbances, and cellular electrical properties.

What is the normal blood pH range to memorize for acid/base assessment?

7.35 to 7.45.

What is homeostasis in the context of cellular physiology?

Maintenance of a stable internal environment (fluids, electrolytes, pH, and ATP supply) through compensatory mechanisms to stay within narrow limits.

What are two common sequelae of hypoxia on cellular metabolism?

Shift to anaerobic glycolysis with lactic acid production causing metabolic acidosis and reduced ATP production.

Define osmosis.

Movement of water across a semipermeable membrane from a region of lower solute concentration to higher solute concentration.

What is the normal osmolality range for body fluids?

280–295 mosmol/kg.

What does tonicity describe and what is the normal isotonic reference for blood?

Tonicity describes effective osmolality; normal isotonic reference is 0.9% NaCl (normal saline).

What triggers the renin-angiotensin-aldosterone system (RAAS)?

Low blood volume/BP, low renal perfusion, or high plasma osmolality that stimulates renin release.

What are the two main actions of angiotensin II?

Peripheral vasoconstriction and stimulation of aldosterone release.

What is the role of aldosterone in fluid balance?

Increases Na+ (and water) reabsorption in the kidneys, raising circulatory volume and reducing urine output.

What is the function of antidiuretic hormone (ADH)?

Promotes water reabsorption in the renal collecting ducts, aiding fluid retention.

What is SIADH and its consequence?

Syndrome of inappropriate ADH secretion causing water retention and hyponatremia with fluid volume excess.

How does hypoproteinemia affect plasma oncotic pressure and fluid shifts?

Low plasma proteins reduce oncotic pressure, promoting fluid movement from blood into interstitial space and causing edema.

What solutes contribute to osmolality, and what is the practical takeaway?

Electrolytes (Na+, K+, Cl-, etc.), glucose, urea, and proteins; osmolality governs water movement (osmosis) in the body.

What is back-up plan #1 during hypoglycemia and what process does it involve?

Glycogenolysis—the breakdown of glycogen to glucose to raise blood glucose.

What is back-up plan #2 during hypoglycemia and what process does it involve?

Gluconeogenesis—the production of glucose from non-carbohydrate sources.

Name the counterregulatory hormones that raise blood glucose during hypoglycemia.

Epinephrine, cortisol, growth hormone, and glucagon.

What happens to cellular metabolism under hypoxic conditions?

Glycolysis proceeds anaerobically, yielding 2 ATP per glucose and accumulating lactate, leading to acidosis.

Define ketogenesis and ketone bodies.

Ketogenesis is the production of ketone bodies from fatty acids; ketones provide limited energy but are acids that can cause acidosis.

What are common signs of metabolic acidosis?

Headache, decreased BP, hyperkalemia, muscle twitching, warm/flushed skin, nausea, vomiting, diarrhea, altered LOC, and Kussmaul respirations.

What are common etiologies of metabolic acidosis?

Diabetic ketoacidosis (DKA), lactic acidosis, kidney failure, severe diarrhea, and poisons/drug overdoses.

How does metabolic acidosis typically attempt to compensate?

By increasing respiratory rate and depth to blow off CO2 (respiratory compensation).

What characterizes metabolic alkalosis and its common cause?

High pH with high HCO3-; commonly due to vomiting or excessive bicarbonate intake; compensated by reduced respiratory rate.

What is respiratory acidosis and its compensatory mechanism?

Low pH due to hypoventilation/CO2 retention; kidneys compensate by increasing HCO3- reabsorption.

What is respiratory alkalosis and its compensatory mechanism?

High pH due to hyperventilation/CO2 loss; kidneys compensate by decreasing HCO3- reabsorption or excretion.

What is the normal range for serum bicarbonate (HCO3-)?

22–28 mEq/L.

What is the normal serum osmolality range?

280–295 mosmol/kg.

How does edema form in the setting of low plasma oncotic pressure?

Water moves from blood to interstitial space due to decreased oncotic pressure, leading to edema.

What is proteinuria and its consequence?

Loss of protein in urine due to glomerular damage, causing hypoproteinemia and edema.

What is the Na+/K+ ATPase pump and why is it essential?

It uses ATP to transport Na+ out of the cell and K+ into the cell, maintaining the resting membrane potential (~-90 mV).

What happens when ATP is deficient and the Na+/K+ pump fails?

Cell membrane becomes depolarized or abnormally polarized, impairing electrical signaling and cell function.

How does hyperkalemia affect cellular resting membrane potential?

Depolarizes cells (less negative RMP, e.g., from -90 mV toward -60 mV), increasing excitability.

How does hypokalemia affect cellular resting membrane potential?

Hyperpolarizes cells (more negative RMP, e.g., toward -120 mV), decreasing excitability.

What effect does hypocalcemia have on membrane potential and excitability?

Increases Na+ permeability, depolarizing the cell (hypopolarization) and causing tetany and hyperexcitability.

What happens in hypercalcemia regarding membrane potential and excitability?

Decreases Na+ permeability, hyperpolarizing cells and reducing excitability (possible bradycardia).

What is the Chvostek sign?

Facial muscle twitch with tapping of the facial nerve, indicating hypocalcemia.

What is tetany and what causes it?

Sustained muscle contractions due to severe hypocalcemia (and sometimes hypomagnesemia).

What is the role of ADH in SIADH?

In SIADH, excess ADH leads to water retention and dilutional hyponatremia with reduced urine output (oliguria).

What is proteinuria and its edema-related consequence?

Proteins leak into urine due to kidney/glomerular issues, causing hypoproteinemia and edema via decreased oncotic pressure.

What is isotonic IV fluid, and give an example?

An IV fluid with tonicity similar to blood; example: 0.9% NaCl (normal saline).

What are the three main body fluid compartments?

Intracellular fluid (ICF), extracellular fluid (ECF) including interstitial fluid and plasma (vascular) space.

What is osmosis governed by in the context of fluid shifts?

Osmolality determines the direction of water movement; higher osmolality draws water from lower osmolality areas.

What is the difference between isotonic, hypotonic, and hypertonic fluids?

Isotonic: same osmolality as blood (e.g., 0.9% NaCl); Hypotonic: lower tonicity (e.g., 0.45% NaCl) causing water to move into cells; Hypertonic: higher tonicity (e.g., 3% NaCl) drawing water out of cells.

What is the process of glycogenesis?

Formation and storage of glycogen from glucose in the liver and muscles.

What is glycogenolysis?

Breakdown of glycogen to glucose to supply energy.

What is glycolysis?

Metabolic pathway that converts glucose to pyruvate (or lactate under anaerobic conditions), producing ATP.

What is gluconeogenesis?

Production of glucose from non-carbohydrate precursors (backup energy source during low glucose).

What are ketone bodies and when are they produced?

Acidic energy sources produced from fatty acids during prolonged fasting or insulin deficiency; can cause ketoacidosis if excessive.

What is the role of the liver in amino acid and glucose metabolism during fasting?

Contributes to gluconeogenesis and ketogenesis when glucose is scarce.

What is the significance of acetyl-CoA in metabolism?

Central substrate linking glycolysis to the Krebs cycle and ketogenesis; produced from fatty acids and some amino acids.

What is the significance of the TCA cycle in cellular energy?

Main pathway that oxidizes acetyl-CoA to CO2, producing NADH/FADH2 for the electron transport chain and ATP.

What is the clinical relevance of ABGs (arterial blood gases)?

Measures pH, HCO3-, and PCO2 to assess acid/base status and respiratory/metabolic compensation.

What is hypoxia’s impact on cellular ATP production?

Reduces aerobic ATP production, forces anaerobic glycolysis, and promotes acidosis.

What is the significance of hypoglycemia in clinical assessment?

Counterregulatory hormones are activated to raise blood glucose, with glycogenolysis and gluconeogenesis as backup plans.