BIOL 228 Lecture 4 Exam Flashcards

How many molecules of CO2 are produced from the complete aerobic oxidation of one molecule of glucose?

6 molecules of CO2.

What is the most common and efficient method of ATP production in human cells?

Aerobic cellular respiration.

Where are hexokinase and pyruvate dehydrogenase located, and what do they catalyze?

Hexokinase is located in the cytoplasm (cytosol) and catalyzes the first step of glycolysis (phosphorylating glucose to glucose-6-phosphate).

Pyruvate dehydrogenase is located in the mitochondrial matrix and catalyzes the intermediate decarboxylation step that converts pyruvate to acetyl-CoA.

What are the 4 stages of cellular respiration, their cellular locations, and key outputs?

1. Glycolysis (Cytoplasm, anaerobic): Splits 6-carbon glucose into two 3-carbon pyruvate molecules; yields a net gain of 2 ATP (substrate-level) and 2 NADH.

2. Decarboxylation / Intermediate Step (Mitochondrial matrix): Strips 1 carbon from each pyruvate as CO2, reduces NAD+ to NADH, and attaches the 2-carbon acetyl group to Coenzyme A to form Acetyl-CoA.

3. Citric Acid / Krebs Cycle (Mitochondrial matrix): Oxidizes Acetyl-CoA completely into CO2, generating NADH, FADH2, and 2 ATP (via GTP) per glucose.

4. Electron Transport Chain / ETC (Inner mitochondrial membrane): Uses electrons from NADH and FADH2 to pump H+ into the intermembrane space, driving ATP synthase (oxidative phosphorylation).

What is the net ATP yield for complete aerobic oxidation vs. anaerobic metabolism per glucose molecule?

Complete aerobic oxidation yields 30–32 net ATP (historically cited as 36–38).

Anaerobic metabolism yields only 2 net ATP (from glycolysis alone) and reduces pyruvate to lactic acid (lactate), regenerating NAD+.

At rest, what is skeletal muscle tissue's preferred fuel molecule and why?

Fatty acids (broken down via beta-oxidation) as its primary energy source to spare blood glucose for the brain.

Triglycerides and steroids are primary structural classes of which macromolecule?

Lipids.

What holds the largest energy reserve in the body?

Lipids (triglycerides stored in adipose tissue) at ~9 kcal/gram.

What is Vitamin C (ascorbic acid) essential for, and what does its deficiency cause?

It is a water-soluble antioxidant essential for collagen synthesis and connective tissue repair; deficiency causes scurvy.

What are nonessential amino acids?

Amino acids that the human body can synthesize internally (primarily in the liver via transamination) and therefore do not strictly have to be consumed in the diet.

Where does the vast majority of nutrient, vitamin, mineral, and water absorption occur?

Across the mucosa of the small intestine (duodenum and jejunum).

What are the fat-soluble vitamins, and how are they absorbed and stored?

Vitamins A, D, E, and K; absorbed alongside dietary lipids via micelles and chylomicrons, and stored in the liver and adipose tissue.

What does Vitamin A deficiency cause?

Night blindness (nyctalopia) due to impaired rhodopsin regeneration in retinal rods, as well as dry, keratinized epithelium.

What does Vitamin K deficiency cause and why?

Bleeding and coagulation disorders because Vitamin K is required by the liver to synthesize clotting factors (II, VII, IX, X).

What is iodine, and what does its deficiency cause?

An essential trace mineral (micromineral) required for the synthesis of thyroid hormones (T3 and T4); deficiency causes goiter and hypothyroidism.

What is positive nitrogen balance, and when does it occur?

Occurs when nitrogen intake exceeds nitrogen excretion, indicating active tissue growth and protein synthesis (seen in growing children, pregnancy, and tissue healing).

What are Recommended Daily Allowances (RDAs)?

Standardized daily nutrient intake levels established to meet the nutritional needs of nearly all (97–98%) healthy individuals in a specific age and sex group.

What dietary guide officially replaced the older Food Pyramid?

MyPlate (organized into five food groups: fruits, vegetables, grains, protein, dairy).

How does the body maintain homeostasis in the fed (absorptive) state?

Elevated blood glucose stimulates pancreatic beta cells to secrete insulin, which promotes cellular glucose uptake, glycogenesis, lipogenesis, and protein synthesis.

What is the first step of fatty acid metabolism, and what occurs during beta-oxidation?

First step: Activation of the fatty acid in the cytosol by attaching Coenzyme A to form fatty acyl-CoA (requires ATP) so it can enter the mitochondrion.

Beta-oxidation: The mitochondrial matrix pathway that cleaves fatty acid chains two carbons at a time into Acetyl-CoA molecules to enter the Citric Acid Cycle.

What are the functions of VLDL and HDL?

VLDL (Very Low-Density Lipoprotein): Synthesized by the liver to transport endogenous triglycerides to peripheral tissues (especially adipose tissue).

HDL (High-Density Lipoprotein): Synthesized by the liver and intestine to scavenge excess cholesterol from peripheral tissues and transport it back to the liver for excretion (good cholesterol).

What are the major metabolic functions of the liver?

Regulates blood glucose (glycogenesis, glycogenolysis, gluconeogenesis), synthesizes plasma proteins (albumin, clotting factors), deaminates amino acids and converts toxic ammonia into urea, metabolizes lipids/cholesterol, stores fat-soluble vitamins and iron, and detoxifies drugs/alcohol.

What happens when more glucose is consumed than immediately needed?

It is first stored as glycogen via glycogenesis (in liver and skeletal muscle); once glycogen stores are full, excess glucose is converted into triglycerides via lipogenesis and stored in adipose tissue.

What does Basal Metabolic Rate (BMR) measure, and how do surface area and temperature affect it?

Measures the minimum resting energy expenditure (heat production) required to sustain vital functions while awake and fasting. It is directly proportional to body surface area (smaller individuals have higher surface-area-to-volume ratios, lose heat faster, and have higher BMRs per unit mass). Elevated body temperature (fever) increases cellular enzymatic reaction rates and raises BMR.

How do sweating and shivering function as autonomic thermoregulatory adaptations, and what brain region controls temperature?

Sweating promotes evaporative heat loss when overheated; shivering generates metabolic heat through rapid, involuntary skeletal muscle contractions when cold.

The hypothalamus (specifically the preoptic area) acts as the body's thermostat.

What are coenzymes?

Non-protein organic molecules (often derived from B vitamins, such as NAD+, FAD, and Coenzyme A) that bind to enzymes and transfer electrons or functional groups during metabolic reactions.

What is the intermediate step of aerobic cellular respiration?

Oxidative decarboxylation of pyruvate into Acetyl-CoA (removes CO2 and produces NADH).

What is glycogenesis?

The anabolic synthesis of glycogen chains from glucose monomers, stimulated by insulin in liver and muscle cells.

Break down the exact ATP yield for 1 molecule of glucose under aerobic vs. anaerobic catabolism.

Complete aerobic oxidation: 30–32 net ATP (2 from glycolysis, 2 from the citric acid cycle, 26–28 from oxidative phosphorylation).

Anaerobic catabolism: 2 net ATP (from glycolysis) and produces lactic acid (lactate).

What continuous supply does glycolysis depend upon?

Oxidized NAD+ to accept electrons during the oxidation of glyceraldehyde-3-phosphate (regenerated via the ETC aerobically or via lactate fermentation anaerobically).

What is the final electron acceptor in aerobic respiration, and which ion accumulates during electron transport phosphorylation?

Molecular oxygen (O2) accepts electrons at the end of the ETC and combines with H+ ions to form water (H2O).

Hydrogen ions (protons, H+) are pumped across the inner mitochondrial membrane and accumulate in the intermembrane space to create the proton-motive force.

What processes make up carbohydrate metabolism?

Glycolysis, gluconeogenesis (making new glucose from non-carbohydrates like amino acids/glycerol), glycogenesis, and glycogenolysis (breaking down glycogen into glucose).

What are chylomicrons?

Large lipoprotein particles assembled inside intestinal enterocytes that transport absorbed dietary triglycerides and cholesterol through lacteals (lymphatics) into the bloodstream.

Define the 4 mechanisms of body heat loss.

Convection: Transfer of heat by the movement of a fluid (liquid or gas currents) between areas of different temperatures.

Radiation: Emission of infrared electromagnetic heat waves from the body surface to cooler surroundings without physical contact (~60% of resting heat loss).

Conduction: Direct transfer of thermal energy between two objects in physical contact.

Evaporation: Heat loss occurring as liquid water (sweat or insensible moisture) absorbs thermal energy to vaporize into gas.

What are the organs of excretion, and what is the sequence of organs for urine formation and passage?

Organs of excretion: Primarily the kidneys (nitrogenous wastes, ions, water), aided by the lungs (CO2), skin/sweat glands (water, salts, small amounts of urea), and the liver/GI tract (bile pigments, solid wastes).

Sequence: Kidneys → Ureters → Urinary Bladder → Urethra.

What are the major functions of the kidneys?

Filter blood plasma and excrete metabolic wastes (urea, uric acid, creatinine); regulate blood volume, blood pressure, and plasma osmolarity; maintain electrolyte balance (Na+, K+, Ca2+) and acid-base pH; perform gluconeogenesis during fasting; secrete renin (blood pressure) and erythropoietin (EPO) (RBC production).

How do the kidneys respond to low blood pressure?

Granular (juxtaglomerular) cells secrete the enzyme renin into the bloodstream, activating the Renin-Angiotensin-Aldosterone System (RAAS) to cause vasoconstriction and increase Na+/water retention.

Where are the kidneys located, and what are their protective layers from deep to superficial?

Location: Retroperitoneal (behind the parietal peritoneum) on the posterior abdominal wall between vertebrae T12 and L3 (right kidney sits slightly lower due to the liver).

Layers (Deep to Superficial):

1. Fibrous (Renal) Capsule (prevents infection spread) →

2. Perirenal Fat Capsule (cushions and holds kidney in place) →

3. Renal Fascia (outer dense connective tissue anchoring the kidney).

Describe the renal pyramids and the renal corpuscle.

Renal pyramids: 8 to 18 cone-shaped striated tissue masses in the renal medulla whose tips (renal papillae) drain urine into minor calyces.

Renal corpuscle: Located exclusively in the renal cortex; consists of a tuft of fenestrated capillaries (the glomerulus) surrounded by a double-walled cup (Bowman's / glomerular capsule).

Describe the histological linings and permeability of the PCT, Nephron Loop, and Cortical vs. Juxtamedullary nephrons.

PCT: Simple cuboidal epithelium with dense microvilli (brush border) to maximize surface area for bulk reabsorption.

Nephron Loop (Loop of Henle): Thin descending limb (simple squamous epithelium; permeable to water, impermeable to solutes) and thick ascending limb (simple cuboidal/columnar; impermeable to water, actively pumps out Na+, K+, and Cl-). Cortical nephrons: ~85% of nephrons; short loops barely penetrating the outer medulla (whereas juxtamedullary nephrons have long loops plunging deep into the medulla to concentrate urine).

How do principal cells in the late DCT and collecting duct respond to ADH, Aldosterone, and Cortisol?

Respond to ADH by inserting aquaporin-2 water channels into apical membranes (increasing water reabsorption); respond to Aldosterone (a mineralocorticoid; cortisol can weakly cross-react at high levels) by increasing Na+ reabsorption and K+ secretion.

Where is the Juxtaglomerular Apparatus (JGA) located, and what are its two cell types?

Located where the ascending limb/early DCT contacts the afferent arteriole at the vascular pole. Granular (juxtaglomerular) cells: Enlarged smooth muscle mechanoreceptors in the afferent arteriole wall that sense BP and secrete renin. Macula densa: Tall, closely packed chemoreceptor cells in the ascending limb/DCT wall that monitor filtrate NaCl concentration and regulate afferent arteriole diameter (tubuloglomerular feedback).

What is the sequence of blood flow through the kidney?

Renal Artery → Segmental Artery → Interlobar Artery → Arcuate Artery → Cortical Radiate (Interlobular) Artery → Afferent Arteriole → Glomerulus → Efferent Arteriole → Peritubular Capillaries / Vasa Recta → Cortical Radiate Vein → Arcuate Vein → Interlobar Vein → Renal Vein.

What is unique about glomerular capillaries, and what happens if the glomerulus is obstructed?

Unlike systemic capillary beds between an arteriole and venule, the glomerulus is fed and drained by two arterioles (wider afferent, narrower efferent), maintaining high pressure (~55 mmHg) for filtration. Obstruction blocks blood flow and filtration, causing GFR and urine output to drop sharply (oliguria/anuria) while backing up hydrostatic pressure into the afferent arteriole.

What are the 3 steps of urine formation and the tubular path of filtrate?

Steps: 1. Glomerular Filtration → 2. Tubular Reabsorption → 3. Tubular Secretion. Path: Bowman's Capsule → PCT → Nephron Loop → DCT → Collecting Duct → Papillary Duct → Minor Calyx → Major Calyx → Renal Pelvis → Ureter.

What are the 3 layers of the filtration membrane?

1. Fenestrated Glomerular Endothelium (pores allow solutes through while blocking blood cells). 2. Basement Membrane (negatively charged gel matrix blocking large plasma proteins like albumin). 3. Podocytes (visceral layer of Bowman's capsule; foot processes/pedicels interdigitate to form narrow filtration slits covered by slit diaphragms).

Calculate Net Filtration Pressure (NFP) and state the daily GFR.

NFP = HPg - (OPg + HPcs) = 55 - (30 + 15) = +10 mmHg. Daily GFR averages 125 mL/min, producing ~180 liters of filtrate per day (99% reabsorbed).

Explain the myogenic response and the effects of ANP on the kidneys.

Myogenic response: Vascular smooth muscle in the afferent arteriole automatically constricts when stretched by rising systemic BP (and dilates when pressure drops) to keep GFR constant. Atrial Natriuretic Peptide (ANP): Released by cardiac atria in response to high blood volume/stretch; dilates afferent arterioles, constricts efferent arterioles (increasing GFR), and inhibits renin, aldosterone, and Na+ reabsorption to promote natriuresis (Na+ loss) and lower BP.

Distinguish reabsorption vs. secretion, explain glucose reabsorption/renal threshold, and describe protein recapture.

Reabsorption moves useful substances from filtrate back into peritubular blood; secretion moves wastes, drugs, H+, and K+ from peritubular blood into filtrate. Basolateral Na+/K+-ATPase pumps drive secondary active symport (SGLT) of 100% of filtered glucose in the PCT. The renal threshold (~180–200 mg/dL for glucose) is the plasma concentration where carriers saturate; excess spills into urine (glucosuria). Small filtered proteins are engulfed via receptor-mediated endocytosis in the PCT, broken down into amino acids inside lysosomes, and released into peritubular capillaries.

Explain the countercurrent multiplier, vasa recta, water reabsorption types, urea excretion, and pregnancy tests.

Countercurrent multiplier: Descending and ascending limbs of juxtamedullary loops establish a steep osmotic gradient in the medulla (300 mOsm/L in cortex to 1200 mOsm/L in deep medulla). Vasa recta: Countercurrent exchanger that preserves this gradient without washing out solutes. Obligatory water reabsorption (~85%): Occurs automatically via osmosis in PCT and descending loop. Facultative water reabsorption (~15%): Regulated by ADH in the collecting duct. PTH: Acts on DCT to increase Ca2+ reabsorption. Urea: ~50% is passively reabsorbed in PCT and recycled in medulla; ~50% is excreted. Pregnancy test: Detects human chorionic gonadotropin (hCG) in urine.

How is GFR measured, and what is the formula for renal plasma clearance?

Measured using inulin (a plant polysaccharide freely filtered and neither reabsorbed nor secreted, so its clearance equals GFR); endogenous creatinine is used clinically. Clearance formula: C = U × V / P.

What are the normal pH and specific gravity of urine?

pH: Typically slightly acidic at ~6.0 (normal range 4.5 to 8.0). Specific gravity: 1.003 to 1.030 (relative to distilled water at 1.000).

Describe the ureter wall layers, transitional epithelium, and urinary bladder/trigone anatomy.

Ureter wall: Inner mucosa (transitional epithelium), middle muscularis (inner longitudinal and outer circular smooth muscle for peristalsis), outer fibrous adventitia. Transitional epithelium (urothelium): Found in calyces, renal pelvis, ureters, bladder, and proximal urethra; flattens from dome-shaped to squamous-like cells to allow distension without tearing and forms an impermeable barrier. Bladder & Trigone: Lined by folded mucosa (rugae) and surrounded by the detrusor muscle. The trigone is a smooth, triangular floor region bounded by the two ureteral openings and internal urethral orifice that does not stretch or form rugae, acting as a funnel.

Compare the storage reflex vs. micturition reflex, and list the male urethra segments from proximal to distal.

Storage reflex: Sympathetic impulses (T11–L2) relax the detrusor and constrict the internal urethral sphincter, plus somatic pudendal nerve contraction of the external sphincter. Micturition reflex: Triggered at ~200–400 mL volume; parasympathetic impulses (S2–S4) contract the detrusor and relax the internal sphincter, while conscious somatic inhibition relaxes the external sphincter. Male urethra (proximal to distal): 1. Prostatic urethra → 2. Membranous (intermediate) urethra → 3. Spongy (penile) urethra.

What are the body fluid compartments and their percentages?

Total body water is divided into Intracellular Fluid (ICF, ~2/3) and Extracellular Fluid (ECF, ~1/3). Within ECF, interstitial fluid accounts for ~80% and blood plasma accounts for ~20%.

Define insensible water loss, facultative water loss, edema, and the thirst mechanism.

Insensible water loss: Unnoticed daily evaporation from skin and expired air (~700–900 mL/day). Facultative water loss: Variable urine volume adjusted by ADH. Edema: Abnormal fluid accumulation in the interstitial compartment. Thirst mechanism: Activated by hypothalamic osmoreceptors sensing elevated plasma osmolarity (≥1–2% rise), dry oral mucosa, and Angiotensin II.

How do drinking large volumes of water vs. running a marathon affect plasma osmolarity?

Drinking large volumes of water: Dilutes ECF, decreasing blood osmolarity (inhibits ADH, increases dilute urine output). Running a marathon: Sweating loses hypotonic fluid faster than electrolytes, concentrating blood and increasing plasma osmolarity (triggers thirst and ADH release).

Summarize the roles of Na+, K+, ADH, Ca2+, and Renin/Angiotensin II.

Na+: Primary extracellular cation; water follows Na+ osmotically, determining ECF volume and BP. K+: Primary intracellular cation critical for resting membrane potential; excessive loss (hypokalemia) causes muscle weakness and cardiac arrhythmias. ADH: Increases water reabsorption without directly pumping ions, diluting plasma Na+ (hyponatremia if excessive). Ca2+: Maintained by PTH (raises blood Ca2+ via bone resorption, renal reabsorption, and calcitriol) and Calcitonin (lowers blood Ca2+). Renin & Angiotensin II: Renin is released due to low renal BP, sympathetic stimulation, or low macula densa NaCl, generating Angiotensin II to cause vasoconstriction, stimulate thirst, and trigger aldosterone and ADH release.

Explain acid-base dynamics, the bicarbonate buffer system, and effects of a diet rich in animal protein.

Normal arterial pH is 7.35–7.45. The bicarbonate buffer system (CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-) is the main extracellular chemical buffer. A diet rich in animal protein generates nonvolatile metabolic acids (sulfuric/phosphoric acids), creating an acidic load; kidneys respond by excreting more H+ and reabsorbing/generating new HCO3-.

Compare respiratory acidosis vs. respiratory alkalosis (anxiety and high altitude) and renal compensation mechanisms.

Respiratory acidosis (most common): Caused by hypoventilation and CO2 retention (hypercapnia), shifting the buffer equation right to increase H+ and lower pH. Hyperventilation (anxiety or high altitude): Blows off excessive CO2 (hypocapnia), decreasing H+ and raising pH (respiratory alkalosis). Renal compensation for acidosis: Kidneys secrete H+ into filtrate (buffered by NH3 → NH4+ and HPO4^2-) and reabsorb/generate new HCO3- to raise pH. Renal compensation for alkalosis: Type B intercalated cells in the collecting duct secrete HCO3- into urine and retain H+ in blood to lower pH.