Chapter 19 - Regulation of Metabolism

Flashcards about the regulation of metabolism

Metabolism

All of the chemical reactions in the body.

Plasma

Circulating glucose, fatty acids, and AAs used by the body’s cells for the production of energy via cell respiration.

Energy reserves in cells, such as triglycerides, carbohydrates, and proteins

Broken down via catabolism

Energy reserves (stores, storage)

Synthesized after a meal, via anabolism.

Absorptive State

“feasting/fed,” when nutrients are absorbed into the bloodstream from the GI tract during the 4 h period following a meal

Postabsorptive State

“fasting,” after the absorptive state, when the GI tract is empty of nutrients and the body’s reserves supply energy

Glucagon and insulin

Hormones that regulate the transition between fasting and feasting and maintain homeostasis of glucose.

Alpha cells of pancreatic islets (islets of Langerhans)

Secrete glucagon.

Beta cells of pancreatic islets

Secrete insulin.

Insulin

Increased secretion during absorptive state, when blood glucose is high (140-150 mg/dl).

Glucose

Insulin promotes storage of glucose as glycogen in liver and muscles = glycogenesis (anabolism)

Glucose

Adipose-tissue cells (adipocytes) transform glucose to fat (triglycerides) which is stored in adipose tissue = lipogenesis (anabolism)

Proteins

Insulin promotes cellular uptake of AAs and their incorporation into proteins = protein synthesis (anabolism)

Lipids

Insulin promotes conversion of lipids + glucose into triglycerides to be stored in adipose tissue = lipogenesis (anabolism)

Glycogenolysis

Hydrolysis of glycogen in liver to increase blood glucose (glucose from glycogenolysis in skeletal muscle is used locally)

Gluconeogenesis

Synthesis of glucose from AAs, glycerol, pyruvate, and lactate, in liver and kidneys

Glucose sparing

Most tissues (except nervous) can use free fatty acids (from lipolysis) for energy instead of glucose.

Ketogenesis

Synthesis of ketone bodies from fatty acids, used as an alternative energy source during prolonged fasting (esp. nervous tissue)

Lipolysis

Breakdown of stored fat.

Diabetes Mellitus

Chronic high blood glucose, hyperglycemia

Type 1 diabetes mellitus (T1DM, insulin- dependent)

Insulin deficiency due to autoimmune destruction of beta cells, so insulin must be injected, pumped, or inhaled

Type 2 diabetes mellitus (T2DM, non-insulin -dependent)

Insulin is present but target cells are resistant to insulin, so blood glucose concentration remains high

Ketosis

Ketone body concentration is elevated because increased lipolysis (due to lack of insulin) releases fatty acids, which are converted to ketone bodies (acidic).

Glucosuria

Amount of glucose filtered into urine exceeds maximum for reabsorption in kidneys.

Ketoacidosis

Ketones in breath can occur if there is not enough bicarbonate to neutralize acid from ketone bodies.

Cholesterol

Found in plasma membrane

Cholesterol

Basis for steroids and bile salts

LDL is the “bad cholesterol.”

Excess leads to atherosclerosis

HDL is the “good cholesterol.”

excess cholesterol from organs is attached to return it to the liver

Leptin

Key hormone for long-term regulation synthesized in adipocytes and released in proportion to the amount of fat being stored, acts on hypothalamus to decrease appetite/food intake and increase metabolic rate