Biochem 3 Flashcards

A healthy adult finishes dinner at 7 PM. At what point does their physiology transition into the fasting state?
A. 8–9 PM
B. 7:30 PM
C. The next morning
D. About 2–4 hours later

One hour after a carbohydrate-heavy meal, a student notes her finger-stick glucose is falling from its 30-minute peak. What timing rule-of-thumb best explains this?
A. Blood glucose begins to fall about 1 hour after a meal
B. Glucose cannot fall until hepatic glycogen is depleted
C. Glucose only falls after 4–6 hours
D. Glucose only falls with exercise

Early fasting is characterized by which hormonal shift?
A. Cortisol ↓, epinephrine ↑
B. Insulin ↑, glucagon ↓
C. Insulin ↓, glucagon ↑
D. Thyroxine ↓, growth hormone ↑

A 19-year-old presents for morning labs after a 10-hour fast. The principal hepatic mechanism sustaining euglycemia right now is:
A. Glycogenolysis
B. Lipolysis
C. Gluconeogenesis only
D. Ketogenesis

During an overnight fast, adipocytes mobilize their stored energy. Which pathway and products are correct?
A. Proteolysis → glucose, urea & β-hydroxybutyrate for export
B. Lipolysis → fatty acids, glycerol & β-hydroxybutyrate for export
C. Glycogenolysis → free glucose & β-hydroxybutyrate for export
D. Ketogenesis → acetoacetate & β-hydroxybutyrate for export

As fasting lengthens through the day, which substrate increasingly supplies energy?
A. Circulating glucose
B. Amino acids
C. Fatty acids
D. Ketone bodies

A healthy adult has consumed no calories since 10 PM and presents at 8 AM for testing. The major fuel currently supplying energy is:
A. Ketone bodies
B. Amino acids
C. Fatty acids
D. Glucose

Even in fasting, which tissues continue to oxidize glucose (primary/sole)?
A. Liver and adipose
B. Brain and red blood cells
C. Skeletal and cardiac muscle
D. Kidney cortex and myocardium

After a short fast, you have increased β-oxidation. Which tissues are directly oxidizing fatty acids in this state?
A. Skeletal muscle and liver
B. Brain and RBCs
C. Brain and skeletal muscle
D. RBCs and adipose tissue

After a 48-hour fast, serum β-hydroxybutyrate is elevated. Which organ is the predominant source?
A. Skeletal muscle
B. Liver
C. Adipose tissue
D. Kidney medulla

Endogenous hepatic glucose production during fasting depends primarily on:
A. Glycolysis and ketogenesis
B. Lipolysis and proteolysis
C. Cori cycle and gluconeogenesis
D. Glycogenolysis and gluconeogenesis

The process of synthesizing glucose from non-carbohydrate precursors is termed:
A. Glycogenolysis
B. Glycolysis
C. Gluconeogenesis
D. Ketogenesis

Which list correctly identifies the major carbon sources for gluconeogenesis?
A. Lactate, glycerol, amino acids
B. Fatty acids, ketone bodies, cholesterol
C. Fructose, galactose, mannose
D. Citrate, malate, fumarate

When amino acid carbons are used to make glucose, their nitrogen is primarily excreted as:
A. Ammonia
B. Urea
C. Creatinine
D. Uric acid

A clinician defines the metabolic state of “starvation” by duration alone. Which threshold matches that definition?
A. ≥12 hours without food
B. ≥3 days without food
C. ≥24 hours without food
D. ≥7 days without food

During starvation, skeletal muscle continues to oxidize fatty acids but specifically reduces its use of:
A. Glucose
B. Lactate
C. Glycerol
D. Ketone bodies

As skeletal muscle spares ketone bodies, circulating levels of that substrate:
A. Rise, allowing the brain to oxidize it for energy
B. Fall, forcing more hepatic gluconeogenesis
C. Remain unchanged due to urinary excretion
D. Oscillate with circadian cortisol

Compared with early fasting, hepatic gluconeogenesis during prolonged starvation changes because:
A. Muscle increases amino acid donation
B. Insulin rises and suppresses fatty acid use
C. RBCs switch to fatty acid oxidation
D. The brain increasingly uses ketone bodies

The degradation of stored hepatic glycogen to release glucose is called:
A. Gluconeogenesis
B. Glycolysis
C. Glycogenolysis
D. Lipolysis

After 72 hours without food, which tissue still relies exclusively on glucose oxidation?
A. Hepatocytes
B. Type I skeletal fibers
C. Cardiac myocytes
D. Red blood cells

Which interval best defines the postprandial state?
A. The hour before a meal
B. The period following a meal
C. The 4th–6th hour after an overnight fast
D. The 12th hour after a meal

A 64-year-old burn patient surviving on minimal calories for several days shows a shift away from amino acid catabolism despite persistent caloric deficit. What best describes this adaptation in starvation?
A. Protein autophagy predominance
B. Obligatory proteolysis for gluconeogenesis
C. Net conversion of amino nitrogen to uric acid
D. Protein sparing

What does PEM stand for?
A. Protein-energy malnutrition
B. Polymicrobial enteric malabsorption
C. Post-exertional myopathy
D. Pan-endocrine malfunction

A global health program screens undernourished adults by body mass index and assigns severity. Which statement best describes how PEM is classified?
A. By mid–upper arm circumference alone
B. By serum albumin quartiles
C. By BMI into Grades I–III
D. By skinfold thickness tertiles

A 29-year-old with reduced intake has BMI 17.0–18.4 kg/m². Which PEM grade applies?
A. Grade III
B. Grade I
C. Grade II
D. Not PEM

An 18-year-old with chronic food insecurity has BMI between 16.0–16.9 kg/m². What is the correct PEM grade?
A. Not PEM
B. Grade I
C. Grade III
D. Grade II

A hospitalized elder presents with BMI below 16 kg/m². Which PEM grade is most accurate?
A. Grade III
B. Grade II
C. Grade I
D. Not PEM

Which statement about creatinine production is most accurate?
A. Released variably depending on meal timing proportional to muscle mass
B. Generated primarily by the liver at a near-constant rate proportional to muscle mass
C. Released from muscle at a near-constant rate proportional to muscle mass
D. Generated in kidney proportional to GFR and muscle mass

A 56-year-old with suspected renal disease has rising serum creatinine. Which best describes creatinine removal in normal physiology?
A. Hepatic conjugation with bilirubin
B. Pulmonary exhalation as CO₂
C. Enterohepatic cycling and fecal loss
D. Renal clearance with appearance in urine

In a primary-care panel, several patients show elevated creatinine. What does this most directly suggest?
A. Increased hepatic urea synthesis
B. Impaired renal function
C. Increased muscle mass
D. Lab artifact unique to serum samples

A laboratory validation study compares methods for creatinine measurement in body fluids. Which reaction is classically used?
A. Biuret reaction
B. Benedict’s test
C. Jaffe reaction
D. Molisch test

A neuropharmacology exam asks which substrate most neurons are fundamentally unable to oxidize. The correct answer is:
A. Glucose
B. Ketone bodies
C. Fatty acids
D. Lactate

A hepatology consult explains why nitrogen handling is crucial during catabolism: the liver converts toxic ammonia primarily into which small molecule for safe excretion?
A. Creatinine
B. Uric acid
C. Allantoin
D. Urea

After a carbohydrate-rich meal, a healthy adult’s liver glycogen can rise to approximately:
A. 40–60 g
B. 200–300 g
C. 120–150 g
D. 350–450 g

The same individual completes an overnight fast. Approximate hepatic glycogen content now is:
A. ~80 g
B. ~10 g
C. ~200 g
D. ~150 g

A physiology slide labeled “after an overnight fast” depicts the canonical metabolic state at that timepoint. Which term best matches the label?
A. Refeeding state
B. Postprandial state
C. Basal (postabsorptive) state
D. Starvation state

During a 24–48 hour fast, adipose tissue provides a carbon backbone for gluconeogenesis by releasing glycerol. This glycerol chiefly originates from:
A. Hepatic glycogenolysis
B. Muscle proteolysis
C. Cori cycle
D. Lipolysis of adipose triacylglycerols

A sprinter finishes repeated 400-m intervals; blood tests show increased lactate. In routine physiology, lactate is also a major product of glycolysis in which cells?
A. Renal cortex cells
B. Red blood cells
C. Hepatocytes
D. Adipocytes

A neurologist emphasizes fuel flexibility of the brain during prolonged fasting. Which statement is accurate?
A. Neurons can use ketone bodies to a limited extent
B. Neurons routinely oxidize long-chain fatty acids
C. Neurons rely on fatty acid β-oxidation during sleep
D. Neurons convert ammonia directly to urea

A hospital lab expands specimen types for creatinine testing. In which matrices is creatinine appropriately measured?
A. Bile, plasma, serum, and urine
B. Cerebrospinal fluid, plasma, serum, and urine
C. Plasma, serum, and urine
D. Saliva, serum, and urine

A patient with advanced hepatic dysfunction accumulates ammonia during catabolic stress. What hepatic process counters nitrogen toxicity?
A. Transamination to essential amino acids
B. Conversion of nitrogen to urea
C. Incorporation into creatinine
D. Oxidation to nitric oxide

As insulin falls and glucagon rises during fasting, adipose triacylglycerols are mobilized primarily by:
A. Proteolysis
B. Autophagy
C. Glycogenolysis
D. Lipolysis

Lipolysis of adipose triacylglycerols yields which two major products?
A. Glucose and lactate
B. Acetyl-CoA and acetoacetate
C. Fatty acids and glycerol
D. Alanine and urea

In prolonged fasting, most fatty acids arriving at the liver are preferentially:
A. Converted to ketone bodies rather than fully oxidized to CO₂
B. Stored as hepatic triacylglycerol
C. Exported unchanged in chylomicrons
D. Desaturated to monounsaturates for membrane repair

Hepatic acetyl-CoA is converted into which ketone bodies?
A. Lactate and pyruvate
B. Propionate and acetate
C. Acetone and lactate
D. Acetoacetate and β-hydroxybutyrate

Which structural classification is correctly paired?
A. Acetone—β-ketoacid; acetoacetate—ketone; β-hydroxybutyrate—dialcohol
B. β-Hydroxybutyrate—reduced hydroxy acid; acetoacetate—β-ketoacid; acetone—simple ketone
C. Acetoacetate—aldehyde; β-hydroxybutyrate—tertiary alcohol; acetone—carboxylic acid
D. Acetone—secondary alcohol; β-hydroxybutyrate—ketone; acetoacetate—diacid

In a 4-day fast, a patient’s fruity breath odor increases. The volatile compound arises primarily from:
A. Enzymatic oxidation of β-hydroxybutyrate
B. Pyruvate decarboxylation
C. Peroxisomal β-oxidation
D. Nonenzymatic decarboxylation of acetoacetate

Regarding acetone handling in humans, the most accurate statement is that it is:
A. Rapidly incorporated into gluconeogenesis
B. The principal fuel for myocardium in fasting
C. Expired in breath and not significantly metabolized
D. Cleared renally as acetoacetate

Which statement best describes prealbumin?
A. Principal plasma oncotic protein
B. Acute-phase reactant from muscle
C. Liver-derived protein transporting thyroid hormone
D. Vitamin A–transporting protein synthesized in adipose

To screen for protein malnutrition, clinicians typically measure:
A. Transferrin and haptoglobin
B. Albumin and prealbumin
C. Ceruloplasmin and fibrinogen
D. Retinol-binding protein and ferritin

Why is prealbumin more sensitive than albumin for acute changes in protein status?
A. Albumin has a relatively long half-life
B. Prealbumin is not liver-derived
C. Albumin is unaffected by stress or surgery
D. Prealbumin does not bind hormones

In systemic illness (hepatic disease, renal disease, surgery), serum albumin and prealbumin typically:
A. Increase due to catabolic signaling
B. Remain unchanged
C. Decrease
D. Oscillate with circadian cortisol only

After 3–5 days of fasting, the body’s overall fuel use shifts to:
A. Increased ketone body utilization system-wide
B. Exclusive glucose oxidation
C. Predominant amino acid oxidation
D. Decreased ketone use with greater reliance on fatty acids

During extended fasting, gluconeogenesis becomes the only source of blood glucose primarily because:
A. Liver glycogen stores are depleted after ~30 hours, so glycogenolysis is no longer available
B. Muscle exports free glucose via GLUT4, so glycogenolysis is no longer available
C. The kidney ceases to produce glucose, so glycogenolysis is no longer available
D. Ketone bodies inhibit glycolysis in RBCs, so glycogenolysis is no longer available

The single biggest determinant of how long a person can survive fasting is:
A. Basal metabolic rate
B. Hepatic glycogen starting level
C. Amount of adipose tissue
D. Daily sodium intake

Another factor that influences survival time during starvation is:
A. Serum potassium
B. Body protein levels
C. Vitamin C reserves
D. Hair keratin content

Which statement about fatal starvation is most accurate?
A. Death occurs after 10% body-weight loss in all adults
B. Death occurs at BMI 15 for men and 13 for women
C. Death occurs with selective adipose loss of ~20%
D. Death typically follows ~40% body-weight loss

BMI thresholds associated with death by starvation are approximately:
A. 13 for men, 11 for women
B. 11 for men, 13 for women
C. 16 for men, 14 for women
D. 18.5 for both sexes

Compared with a 24-hour fast, which change is expected in prolonged fasting?
A. Muscle use of ketone bodies increases
B. Brain use of glucose increases
C. Muscle protein degradation decreases
D. Liver production of urea increases

Compared with a 24-hour fast, hepatic gluconeogenesis during prolonged fasting generally:
A. Increases due to rising cortisol alone
B. Decreases as the brain increases ketone use
C. Is unchanged because RBC needs are fixed
D. Stops once glycogen is gone

A 17-year-old with restrictive eating presents with BMI 15.9 kg/m², bradycardia, and distorted body image. Which feature is part of the diagnostic profile of anorexia nervosa?
A. Hyperphagia with normal body weight
B. Lack of concern about thinness
C. Persistent fear of gaining weight
D. Absence of body image disturbance

A 19-year-old runner with severe weight loss develops secondary amenorrhea. In anorexia nervosa, the immediate physiologic cause is most directly:
A. Decreased estradiol synthesis in adipocytes
B. Excess prolactin
C. Hypothyroidism
D. Reduced LH/FSH secretion by the anterior pituitary

In clinical nutrition, the most widely used biochemical marker to estimate body muscle mass is:
A. 24-hour urinary creatinine excretion
B. Serum albumin
C. Prealbumin (transthyretin)
D. Transferrin saturation

To assess muscle mass depletion, creatinine output is normalized to:
A. Ideal body weight, yielding the Creatinine Height Index (CHI)
B. Height, yielding the Creatinine Height Index (CHI)
C. Waist circumference, yielding the Creatinine Height Index (CHI)
D. BMI category, yielding CHI tiers

A patient excretes 80-90% of the expected creatinine for a healthy same-sex, same-height control (after multiplying by 100). What is the CHI category?
A. Normal
B. Mild deficit
C. Moderate deficit
D. Severe deficit

A patient excretes 60–80% of the expected creatinine for a healthy same-sex, same-height control (after multiplying by 100). What is the CHI category?
A. Normal
B. Mild deficit
C. Moderate deficit
D. Severe deficit

A patient excretes <60% of the expected creatinine for a healthy same-sex, same-height control (after multiplying by 100). What is the CHI category?
A. Normal
B. Mild deficit
C. Moderate deficit
D. Severe deficit

Post-meal endocrine changes most consistent with your notes are:
A. Glucagon ↑, insulin unchanged
B. Insulin ↑, glucagon ↓
C. Insulin ↓, glucagon ↑
D. Both hormones decrease

During an overnight fast, which tissues use fatty acids as their principal fuel?
A. Brain and RBCs
B. Liver and skeletal muscle
C. Brain and liver
D. RBCs and skeletal muscle

Falling blood glucose during fasting triggers release of which hormone—and from which cells?
A. Insulin from β-cells
B. Glucagon from α-cells
C. Cortisol from zona fasciculata
D. Epinephrine from chromaffin cells

After ~3 days of fasting, the liver provides an alternative fuel for the brain by releasing:
A. VLDL
B. Free cholesterol
C. Short-chain fatty acids
D. Ketone bodies

By ~3 days of fasting, liver glycogen is depleted. Therefore, blood glucose is supplied by:
A. Glycogenolysis
B. Gluconeogenesis
C. Glycolysis
D. Cori cycle in brain

Glucagon stimulation of adipose tissue supplies the liver with which gluconeogenic carbon source?
A. Propionate
B. Malate
C. Glycerol
D. Butyrate

Which are the three major carbon sources for hepatic gluconeogenesis in your notes?
A. Acetone, acetoacetate, β-hydroxybutyrate
B. Fructose, galactose, mannose
C. Lactate, amino acids, glycerol
D. Palmitate, oleate, stearate

A 24-year-old has had no food for 4 days. Compared with a 24-hour fast, which systemic change is expected now?
A. Muscle use of ketone bodies increases
B. Brain use of glucose increases
C. Liver gluconeogenesis increases
D. Brain use of ketone bodies increases

What is a principal function of prealbumin (transthyretin) described in your notes?
A. Main determinant of plasma oncotic pressure
B. Acute-phase rise with surgery
C. Transport of thyroid hormone
D. Storage of iron in hepatocytes

During an early-morning fast, hepatocytes raise plasma glucose by releasing it from glycogen. This process is:
A. Gluconeogenesis
B. Ketogenesis
C. Transamination
D. Glycogenolysis

A biochemist describes making glucose from glycerol and amino acids. This pathway is called:
A. Gluconeogenesis
B. Glycolysis
C. Glycogenolysis
D. Lipolysis

In hepatic handling of amino acids during catabolism, carbons go to _______, while nitrogens are converted to _______.
A. Ketone bodies; uric acid
B. Glycogen; ammonia
C. Glucose; urea
D. Lactate; nitric oxide

A disaster victim is evaluated on day 3 without food. Which combination best matches the starvation state?
A. 12–24 h; muscle uses glucose; brain uses fatty acids
B. ≥3 days; muscle uses ketone bodies; brain uses glucose
C. 24–48 h; muscle uses amino acids; brain uses lactate
D. ≥3 days; muscle uses fatty acids; brain uses ketone bodies

A healthy adult completes a 12-hour fast for labs. This corresponds to which metabolic state and hormones?
A. Starvation; high insulin, low glucagon
B. Basal state; low insulin, high glucagon
C. Postprandial; high insulin, low glucagon
D. Postabsorptive; high insulin, high glucagon

After a meal, plasma glucose peaks at ~1 hour then declines; by ~2 hours it returns to the fasting range. What fasting range did your notes specify?
A. 80–100 mg/dL
B. 60–70 mg/dL
C. 100–120 mg/dL
D. 50–60 mg/dL

Why are red blood cells obligately dependent on glucose?
A. Lack GLUT transporters
B. No mitochondria
C. Inhibit pyruvate kinase when fasting
D. Prefer β-oxidation for ATP

What is the major energy source during fasting that supplies most fuel to the body?
A. Circulating glucose
B. Amino acids from muscle
C. Adipose triacylglycerols
D. Hepatic glycogen

In the fasting state, which fuel do the kidneys preferentially oxidize?
A. Fatty acids
B. Ketone bodies
C. Glucose
D. Amino acids

Which half-life pairing is correct for these nutrition markers?
A. Prealbumin ≈ 2–3 days; albumin ≈ 14–20 days
B. Prealbumin ≈ 10–12 days; albumin ≈ 2–3 days
C. Both ≈ 7 days
D. Albumin ≈ 2–3 days; prealbumin ≈ 14–20 days

Glucagon signaling in fasting drives adipose to supply the liver’s gluconeogenesis via which carbon source?
A. Butyrate
B. Glycerol
C. Propionate
D. Fructose

After about three days of fasting when hepatic glycogen is depleted, blood glucose is supplied primarily by:
A. Glycogenolysis
B. Cori cycling in brain
C. Gluconeogenesis
D. Dietary carbohydrate

Which set correctly lists tissues that can oxidize ketone bodies for energy?
A. Skeletal muscle, kidneys, nervous system
B. Liver, RBCs, adipose tissue
C. Liver, brain only
D. RBCs and adipose tissue only

During prolonged fasting, adipose triacylglycerol supplies fatty acids and glycerol. These fates are correct:
A. Muscle: ketone bodies; Liver: CO₂ + H₂O
B. Muscle: glycogen; Liver: VLDL
C. Muscle: lactate; Liver: glucose
D. Muscle: CO₂ + H₂O; Liver: ketone bodies

A fasting patient has glucose 65 mg/dL with normal anion gap and no diabetes history. Which serum/urine finding is most likely elevated?
A. Lactate
B. Ketone bodies
C. Free glycerol
D. Insulin

A 19-year-old with polyuria and weight loss has very high ketones and very high glucose. The most likely interpretation is:
A. Starvation state
B. Adrenal insufficiency
C. Alcoholic ketoacidosis
D. Insulin deficiency

The most widely used biochemical approach to estimate muscle mass from 24-hour urinary creatinine is called the:
A. Mid-upper arm muscle circumference index
B. Body protein reserve ratio
C. Creatinine-Height Index (CHI)
D. Nitrogen balance coefficient

In protein malnutrition, urinary levels of which compound fall proportionally to muscle loss?
A. Creatinine
B. Urea
C. Ammonia
D. Urobilinogen

Interpreting BUN: which pairing is correct?
A. Low BUN → renal failure; High BUN → liver failure
B. Low BUN → liver dysfunction; High BUN → kidney dysfunction
C. Low BUN → dehydration; High BUN → overhydration
D. Low BUN → high protein intake; High BUN → low protein intake

Interpreting creatinine: which pairing is correct?
A. Low creatinine → low skeletal muscle production; High creatinine → renal excretory failure
B. Low creatinine → renal failure; High creatinine → high muscle mass with normal kidneys
C. Low creatinine → hemolysis; High creatinine → liver failure
D. Low creatinine → dehydration; High creatinine → overhydration

A thin but otherwise healthy faster has high ketone bodies with normal/low glucose. Best interpretation:
A. Lactic acidosis
B. Ethanol intoxication
C. Starvation physiology
D. Thyrotoxic crisis

After ~30 hours of fasting, hepatic glycogen is depleted. If fasting continues, the only process providing plasma glucose is ______, and one major carbon source is ______.
A. Gluconeogenesis; amino acids
B. Glycogenolysis; lactate
C. Ketogenesis; fatty acids
D. Glycolysis; glycerol

A patient with villous blunting, low MUAMC and CHI, low albumin and prealbumin, and elevated ketones most likely has:
A. Celiac disease with adequate nutrition
B. Hyperthyroidism
C. Primary adrenal insufficiency
D. Protein-energy malnutrition (PEM)

Which list correctly names the three ketone bodies produced by the liver?
A. Pyruvate, lactate, acetate
B. Propionate, acetate, butyrate
C. Acetone, acetoacetate, β-hydroxybutyrate
D. Malate, citrate, oxaloacetate

During fasting, which fuel do the kidneys preferentially oxidize for their own energy needs?
A. Fatty acids
B. Ketone bodies
C. Glucose
D. Amino acids

A prolonged faster is cognitively intact while using ketone bodies heavily. Per your notes, the brain still needs a small amount of glucose primarily to support:
A. ATP production
B. Beta-oxidation
C. Ketone activation
D. Neurotransmitter carbon skeletons

During starvation, adipose lipolysis is active. Which substrate cannot provide net carbon for hepatic glucose production?
A. Glycerol
B. Long-chain fatty acids
C. Lactate
D. Alanine

A patient presents after severe caloric restriction with plasma glucose 65 mg/dL. Which urine finding is most expected?
A. Positive urine ketones
B. Positive urine glucose
C. Positive urine nitrites
D. Positive urine bilirubin

In prolonged fasting, some amino acids are diverted from gluconeogenesis because they are also needed for synthesis of:
A. Ketones and cholesterol
B. Glycogen and glucose
C. Purines and pyrimidines
D. Heme and neurotransmitters

In anorexia nervosa, amenorrhea is linked to low gonadotropins and typically appears when body fat drops to about:
A. 10% body weight
B. 15% body weight
C. 22% body weight
D. 35% body weight

A dietitian calculates Creatinine-Height Index (CHI). Which formula matches your notes for the CHI percentage?

A. Expected/observed × 100
B. Observed/expected × 100
C. Observed − expected × 100
D. Observed + expected ÷ 100

Which best describes creatinine in your notes?
A. Muscle degradation product
B. Dietary nitrogen store
C. Hepatic ketone precursor
D. Plasma oncotic protein

A malnourished patient has low albumin and low prealbumin. Per your notes, this most directly indicates the body’s muscle mass cannot provide enough amino acids to sustain:
A. Ketone clearance and serum proteins
B. Lipolysis signaling and serum proteins
C. Glycogen storage and serum proteins
D. Gluconeogenesis and serum proteins