Seminar 2 Flashcards
Can you name the three major endogenous energy stores?
Three Major Endogenous Energy Stores
1. Glycogen
2. Triglycerides (fat)
3. Muscle protein (used in energy emergencies)
Can you explain how the three major endogenous energy stores differ in size (e.g. weight in (kilo)grams of the substrate stored within (not the organs themselves!)) and stored energy (kcal)?
Glycogen- Liver: ~100g/kg; Muscle: ~400g/kg
2,000 kcal stored energy
Fat (TG)
Storage Varies widely, 12–15 kg in average person
100,000–135,000 kcal stored energy
Protein
Stored From muscle tissue, 6 kg usable
24,000 kcal stored energy
Can you name the organ and specific cells where two important hormones for regulation are secreted?
Insulin
• Secreted by: Beta cells in the pancreas (Islets of Langerhans)
• Glucagon
• Secreted by: Alpha cells in the pancreas (Islets of Langerhans)
Can you explain the main action of these two hormones in controlling whether the three endogenous energy stores store or release substrates?
Insulin
Promotes storage of energy after a meal
Increases glycogen synthesis, lipogenesis, protein synthesis
Anabolic
Glucagon
Promotes release of energy during fasting
Stimulates glycogenolysis, lipolysis,
Catabolic
Can you describe which specific enzymes the two hormones regulate to direct storage or release - particularly following the consumption of a mixed meal?
Insulin activates and glucagon inhibits:
Glycogen synthase (glycogen synthesis )
Phsophofructokinase-1.(Glycolysis)
Acetyl CoA carboxylase (lipogenesis)
Glucagon activates and Insulin inhibits:
Glycogen phosphorylase (glycogen breakdown)
PEP carboxykinase (gluconeogenesis)
Hormone sensitive lipase (lipolysis)
Can you explain the protocol of an oral glucose tolerance test (OGTT)?
Used to assess insulin response and glucose handling
1. Overnight fast (8–12 hours) 2. Baseline blood glucose measured 3. Drink 75g glucose solution (adults) 4. Blood samples taken at 0, 30, 60, 90, and 120 minutes 5. Measure plasma glucose at each time point
Can you define healthy and unhealthy outcomes of the OGTT?
Healthy Glucose Level
<100 mg/dL (<5.6 mmol/L) when fasted
<140 mg/dL (<7.8 mmol/L) after 2 hours
Unhealthy
≥200 mg/dL (≥11.1 mmol/L) after 2 hours = Diabetes
140–199 mg/dL (7.8–11.0 mmol/L) after 2 hours = Prediabetes
≥126 mg/dL (≥7.0 mmol/L) fasted = Diabetes
Can you plot blood concentration of glucose after a mixed meal
Glucose: Sharp rise (30–60 min), then falls as insulin clears it
Can you plot blood concentration of chylomicrons after a mixed meal
Chylomicrons: Rise more slowly (~2–3 hours), then decrease as they are cleared
Can you plot blood concentration of VLDL after a mixed meal
VLDL: Increases later (3–6 hours), as liver packages leftover carbs into fat
Can you plot blood concentration of free fatty acids/NEFA after a mixed meal
NEFA (Free fatty acids): Decrease after the meal due to insulin inhibiting lipolysis
