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Questions and Answers
What is primarily synthesized through substrate-level phosphorylation?
What is primarily synthesized through substrate-level phosphorylation?
Which reaction involves the loss of hydrogen atoms and electrons?
Which reaction involves the loss of hydrogen atoms and electrons?
What role do B vitamin coenzymes play in redox reactions?
What role do B vitamin coenzymes play in redox reactions?
In which cellular locations does substrate-level phosphorylation occur?
In which cellular locations does substrate-level phosphorylation occur?
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What is the primary outcome of oxidation in oxidation-reduction reactions?
What is the primary outcome of oxidation in oxidation-reduction reactions?
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What is the primary function of the electron transport chain in cellular respiration?
What is the primary function of the electron transport chain in cellular respiration?
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Which phase of oxidative phosphorylation involves the use of a proton gradient to synthesize ATP?
Which phase of oxidative phosphorylation involves the use of a proton gradient to synthesize ATP?
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What is the net yield of ATP from glycolysis after accounting for the activation energy used?
What is the net yield of ATP from glycolysis after accounting for the activation energy used?
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How much ATP is typically produced by oxidative phosphorylation from one molecule of glucose?
How much ATP is typically produced by oxidative phosphorylation from one molecule of glucose?
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What is the total ATP yield from one glucose molecule during cellular respiration, including all stages?
What is the total ATP yield from one glucose molecule during cellular respiration, including all stages?
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Which of the following statements about NADH and FADH2 is correct?
Which of the following statements about NADH and FADH2 is correct?
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What is the role of ATP synthase in oxidative phosphorylation?
What is the role of ATP synthase in oxidative phosphorylation?
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What is the average cost of ATP during the shuttle process of electrons across the mitochondrial membrane?
What is the average cost of ATP during the shuttle process of electrons across the mitochondrial membrane?
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What effect does hyperkalemia have on the resting membrane potential (RMP) in neurons?
What effect does hyperkalemia have on the resting membrane potential (RMP) in neurons?
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How does acidosis affect extracellular fluid (ECF) potassium levels?
How does acidosis affect extracellular fluid (ECF) potassium levels?
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Where in the kidneys is potassium balance primarily regulated?
Where in the kidneys is potassium balance primarily regulated?
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What is the consequence of hypokalemia on muscle responsiveness?
What is the consequence of hypokalemia on muscle responsiveness?
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Why do kidneys have a limited ability to retain potassium?
Why do kidneys have a limited ability to retain potassium?
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What is the function of the filtration membrane in the renal corpuscle?
What is the function of the filtration membrane in the renal corpuscle?
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Which structure provides the visceral layer of the glomerular capsule?
Which structure provides the visceral layer of the glomerular capsule?
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Which statement best describes the fate of large particles in the filtration process?
Which statement best describes the fate of large particles in the filtration process?
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What is the role of the efferent arteriole in the context of the renal corpuscle?
What is the role of the efferent arteriole in the context of the renal corpuscle?
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What is primarily retained in the bloodstream during the filtration process?
What is primarily retained in the bloodstream during the filtration process?
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What type of receptors do the macula densa cells contain?
What type of receptors do the macula densa cells contain?
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What do granular cells in the juxtaglomerular complex primarily sense?
What do granular cells in the juxtaglomerular complex primarily sense?
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Which enzyme is contained within the secretory granules of granular cells?
Which enzyme is contained within the secretory granules of granular cells?
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What role do extraglomerular mesangial cells play in the juxtaglomerular complex?
What role do extraglomerular mesangial cells play in the juxtaglomerular complex?
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The function of the macula densa is primarily to detect changes in what aspect of the filtrate?
The function of the macula densa is primarily to detect changes in what aspect of the filtrate?
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Which of the following correctly describes electrolytes?
Which of the following correctly describes electrolytes?
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What is an example of a nonelectrolyte?
What is an example of a nonelectrolyte?
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Which electrolyte dissociates into the greatest number of particles in solution?
Which electrolyte dissociates into the greatest number of particles in solution?
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How does the osmotic power of electrolytes compare to that of nonelectrolytes?
How does the osmotic power of electrolytes compare to that of nonelectrolytes?
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Which ion is most abundant in intracellular fluid (ICF)?
Which ion is most abundant in intracellular fluid (ICF)?
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What distinguishes electrolytes from nonelectrolytes regarding fluid shifts?
What distinguishes electrolytes from nonelectrolytes regarding fluid shifts?
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Which statement about bicarbonate (HCO3) is correct?
Which statement about bicarbonate (HCO3) is correct?
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Which of the following pairs correctly identifies the particle count of NaCl and MgCl2 in solution?
Which of the following pairs correctly identifies the particle count of NaCl and MgCl2 in solution?
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In which bodily fluid is chloride (Cl−) concentration typically higher?
In which bodily fluid is chloride (Cl−) concentration typically higher?
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Study Notes
Anabolism and Catabolism
- Anabolism is the synthesis of large molecules from small ones. Proteins are synthesized from amino acids.
- Catabolism is the hydrolysis of complex structures to simpler ones. Proteins are broken down into amino acids. Hydrolysis breaks down polymers.
Cellular Respiration
- Cellular respiration is a catabolic breakdown of food fuels. Energy from food is captured to form ATP in cells.
- The goal of cellular respiration is to trap chemical energy in ATP.
- Energy can also be stored in glycogen and fats which can be broken down later.
Processing Nutrients
- There are three stages in processing nutrients:
- Stage 1: digestion, absorption, and transport to tissues
- Stage 2: cellular processing (in the cytoplasm)
- Synthesis of lipids, proteins, and glycogen, or
- Catabolism (glycolysis) into pyruvic acid and acetyl CoA
- Stage 3: oxidative breakdown of intermediates into CO2, water, and ATP; occurs in the mitochondria
- Cellular respiration consists of glycolysis of stage 2 and all of stage 3. All eventually converge into a common pathway.
Oxidation-Reduction Reactions
- Oxidation reactions involve the gain of oxygen or loss of hydrogen atoms (electrons).
- Oxidation-reduction (redox) reactions happen when one substance loses electrons while another substance gains electrons. Oxidized substances lose electrons and energy while reduced substances gain electrons and energy.
- Redox reactions are usually catalyzed by enzymes requiring a B vitamin coenzyme.
ATP Synthesis
- Two mechanisms are used to make ATP from captured energy that is liberated during cellular respiration:
-
- Substrate-level phosphorylation
- High-energy phosphate groups directly transferred from phosphorylated substrates to ADP.
- Example: phosphagen system in skeletal muscle.
-
- Oxidative phosphorylation
- More complex process that produces most ATP.
- Chemiosmotic process: movement of substances across membranes is coupled to chemical reactions.
- Energy released from oxidation of food is used to create a steep H+ concentration gradient across inner mitochondrial membrane by pumping H+ across it.
-
Oxidation of Glucose
- Glucose is catabolized by the following reaction: C₆H₁₂O₆ + 6O₂ → 6H₂O + 6CO₂ + 32 ATP + heat.
- Complete glucose catabolism requires three pathways:
- Glycolysis: Glucose is split in half
- Krebs Cycle (Citric acid cycle): Many intermediates are produced.
- Electron transport chain and oxidative phosphorylation
- The three stages are linked to generate most of body's ATP.
Glycogenesis, Glycogenolysis, and Gluconeogenesis
- Glycogenesis: stores glucose by making glycogen to store excess glucose. Mostly occurs in liver and skeletal muscle cells.
- Glycogenolysis: Breakdown of glycogen, via glycogen phosphorylase, when blood glucose is low.
- Gluconeogenesis: Forming new glucose from non-carbohydrate sources (fats and protein). Occurs in liver when blood glucose levels drop, protecting against hypoglycemia. This is essential for the nervous system.
Lipid Metabolism
- Lipids provide a higher energy yield than glucose or protein catabolism. Fat catabolism yields 9 kcal per gram versus 4 kcal per gram of carbohydrate or protein.
- Glycerol breakdown can be treated as glucose.
- Fatty acids undergo beta oxidation within mitochondria to produce ketones.
Lipogenesis
- Triglyceride synthesis occurs when cellular ATP and glucose levels are high.
- Dietary glycerol and fatty acids are stored as triglycerides in adipose tissue and other parts of the body.
- Glucose is easily converted to fat because acetyl CoA is intermediate in glucose catabolism and a starting point for fatty acid synthesis.
Lipolysis
- Lipolysis is the breakdown of stored fats into glycerol and fatty acids. It's the reverse of lipogenesis.
- Fatty acids are especially preferred as fuel by the liver, heart, and resting skeletal muscle, compared to glucose.
- Increased lipolysis occurs when carbohydrate intake is inadequate, resulting in ketogenesis, where acetyl CoA can convert to ketone bodies (ketones).
- Accumulation of ketones results in metabolic acidosis.
Body Fluid Compartments
- Infants are 73% or more water, with lower body fat and bone mass.
- Adult males have approximately 60% water, while adult females have ~50% water.
- Adipose tissue is the least hydrated of all tissues.
- Total body water in adults averages approximately 40 Liters. Water content decreases to about 45% in old age.
- Major fluid compartments of the body: intracellular fluid (ICF), interstitial fluid (IF), and plasma.
Composition of Body Fluids
- Electrolytes dissociate into ions in water (examples: inorganic salts, acids, bases, some proteins.)
- Ions conduct electrical current and have a greater osmotic power than nonelectrolytes.
- Dissociation into more than two ions gives a considerable osmotic power capable of causing fluid shifts. (NaCl → Na+ + Cl-; MgCl₂ → Mg²+ + 2Cl⁻).
Water Balance and ECF Osmolality
- Water intake must equal water output (~2500 ml/day).
- Water intake is primarily from ingested foods and beverages, with some produced by cellular metabolism (metabolic water).
- Water output includes urine (~60%), insensible water loss, perspiration, and feces.
- Osmolality is maintained around 280-300 mOsm. A rise in osmolality stimulates thirst and causes ADH release. A decrease in osmolality causes thirst inhibition and ADH inhibition.
Regulation of Water Intake
- Thirst is the primary driver for water intake, governed by the hypothalamic thirst center.
- Hypothalamic osmoreceptors are activated by increased plasma osmolality, dry mouth, and decreased blood volume/pressure.
Regulation of Sodium Balance
- Sodium is the most abundant cation in ECF.
- In maintaining ECF volume and water distribution, Na is important. Changes in plasma Na+ levels affect ECF and IF volumes.
- Important for blood pressure and blood volume.
- Aldosterone and angiotensin II control blood pressure and blood volume through regulating Na+ reabsorption by the kidneys.
- Atrial natriuretic peptide (ANP) released by atrial cells decreases blood pressure and volume by increasing Na+ and water excretion.
Regulation of Potassium Balance and Acid-Base Balance
- Potassium (K+) plays an important role in regulating resting membrane potential (RMP) in neurons and muscle cells, and is a crucial part of the body's buffer system.
- Imbalances (hyperkalemia or hypokalemia) disrupt normal electrical conduction, leading to potentially severe issues.
- ECF K⁺ levels rise with acidosis and fall with alkalosis.
- K+ balance is controlled in cortical collecting ducts.
- Kidneys have limited ability to hold onto K+ which can lead to its deficiency if not replaced in diet
- pH affects all body fluids' functional proteins and biochemical reactions, so maintaining proper pH is crucial in maintaining health. A proper pH is 7.4, with the typical range varying ever so slightly.
- Imbalances result in respiratory and metabolic acidosis/alkalosis. The symptoms resulting from these conditions can range from mild to seriously debilitating.
Chemical Buffer Systems
- Chemical buffer systems provide the first line of defense against pH changes, acting quickly.
- Important buffer systems: bicarbonate buffer system, phosphate buffer system, and protein buffer system.
Renal Clearance
- Renal clearance is the volume of plasma the kidneys clear of a substance over time.
- Inulin is a freely filtered marker to estimate kidney function by measuring its clearance rate.
- If clearance is less than 125 ml/minute, then the substance or compound is actively reabsorbed by the kidney. If equal to 125 ml/minute, there is no reabsorption or secretion taking place. If clearance is greater than 125 ml/minute, then there is secretion occuring.
Urine
- Urine is a waste product that displays a myriad of characteristics that may indicate a disease or illness.
- Normal urine solutes include Na⁺, K⁺, PO₄⁻³, SO₄⁻², Ca²⁺, Mg²⁺, and HCO₃⁻.
- Abnormal concentrations of solutes or the presence of abnormal components such as blood proteins, WBCs, and bile pigments often indicate a pathology.
- Normal urine has a slightly acidic pH, between 4.5 and 8.0.
- Urine has a slight aromatic odor fresh and may change over time due to bacteria.
- Specific gravity of urine varies from 1.001 to 1.035, as it has more solutes than water.
Nephrons and Renal Processes
- Nephrons are the primary functional units of the kidney.
- Three major renal processes:
- Filtration: takes place in the glomerulus. Large materials are left behind in the bloodstream
- Reabsorption: substances needed by the body (e.g., water, nutrients) are reabsorbed into the blood.
- Secretion: substances that are harmful to the body are actively moved from the blood into the filtrate.
Regulation of Glomerular Filtration
- Intrinsic controls maintain almost constant filtration rate (GFR) when mean arterial pressure (MAP) is within the normal range (80-180 mm Hg). This occurs by way of myogenic mechanism (smooth muscle response to stretching) and tubuloglomerular feedback mechanism (macula densa cells detecting NaCl levels in filtrate).
- Extrinsic mechanisms (e.g., sympathetic nervous system, hormones) indirectly regulate GFR by maintaining systemic blood pressure. This ensures constant GFR despite variations in blood pressure and blood volume.
Tubular Reabsorption
- Sodium (Na⁺) reabsorption plays a crucial role in reabsorbing almost every other substance due to its active transport and the subsequent indirect transport of the other substances.
- Secondary active transport takes advantage of this electrochemical gradient for the transport of various substances using cotransporters.
- Glucose, amino acids, some ions, and vitamins are reabsorbed using secondary active transport along with sodium (Na+).
Tubular Secretion
- Tubular secretion is reabsorption in reverse, providing a “second chance” to add selected substances to the filtrate.
- In the proximal convoluted tubule, substances such as K⁺, H⁺, NH₄⁺, creatinine, organic acids, and bases are secreted.
- Substances such as HCO₃⁻ are synthesized in the tubule cells and secreted, helping control blood pH.
Regulation of Urine Concentration and Volume
- Fluid flows in opposite directions in adjacent segments of the same tube, creating a countercurrent multiplier and exchanger.
- The countercurrent multiplier establishes an osmotic gradient within the renal medulla, allowing the kidney to excrete varying concentrations of urine.
- The countercurrent exchanger preserves this gradient by reducing the loss of solutes into vasa recta.
- Collecting ducts use the gradient to adjust urine concentration as needed.
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Description
Test your knowledge on cellular respiration processes, particularly substrate-level phosphorylation and the electron transport chain. This quiz covers various reactions involved in ATP synthesis and the role of coenzymes in redox reactions. Challenge yourself with questions about ATP yield and the importance of NADH and FADH2.
