Metabolism and Hormonal Regulation Quiz

Integration of Metabolism

• Metabolism is the sum of all chemical reactions in an organism
• Integrated metabolic processes in the body involve multiple organs working together

Cellular Level Metabolism

• Enzymatic roles, flux of metabolites in pathways, regulation through feedback mechanism and transport of metabolites
• Various specific tissues and organs play different roles
• Hormonal regulation of metabolism affects the whole organism and body mass control

Neuronal vs. Hormonal Signaling

• Neuronal signaling occurs through neurotransmitters affecting nearby cells (short distance)
• Hormonal signaling uses hormones traveling through the bloodstream to affect distant cells or organs (long distance)

Hormone-Receptor Interactions

• Varying receptor types on different cells lead to varying responses
• Hormones bind to specific receptors with high affinity, needing only low hormone amounts
• Receptors are intracellular or extracellular, affecting cell functions

"Downstream" Events, Following Hormone Binding

• Secondary messengers, like cAMP and IP3, are released inside the cell and affect enzyme activity
• Receptor Tyrosine Kinase activity leads to cell responses
• Hormone-gated ion channels can open or close to change membrane potential
• Adhesion receptor interactions affect the cytoskeleton
• Steroid hormone receptors in the nucleus can change gene expression

Three Classes of Mammalian Hormones

• Endocrine hormones are released into the blood stream and travel to affect distant cells or organs
• Paracrine hormones diffuse in the extracellular space and affect nearby cells
• Autocrine hormones affect the cell producing them

Peptide and Amine Hormones

• Peptide hormones include insulin, glucagon, somatostatin, etc.
• Epinephrine (adrenaline) is an amine hormone
• They bind to membrane receptors; this activates second messenger pathways impacting many targets

Insulin as a Peptide Hormone

• Synthesized on ribosomes in the pancreas, processed into active form
• Stored in secretory vesicles in the pancreas
• Has 51 amino acids; A and B chains are similar across species

Newer Insulins

• Rapid-acting analogs (Lispro, Aspart, Glulisine) have faster onset
• Long-acting analogs (glargine, detemir) have extended duration of action
• Analogs change amino acid sequence to modify activity

Epinephrine and Norepinephrine

• Catecholamine hormones made in the adrenal medulla from L-tyrosine
• Stored and released like peptide hormones
• Bind to extracellular receptors to trigger secondary messenger systems similar to peptide hormones

Paracrine Hormones

• Include prostaglandins, thromboxanes, leukotrienes
• Made in response to stimuli near the site of release
• Affect local tissues (inflammation, smooth muscle contraction, etc.)

Steroid Hormones

• Derived from cholesterol
• Bind to carrier proteins to travel through the bloodstream
• Enter the nucleus and act on nuclear receptors to change gene expression
• Some bind plasma receptors affecting various tissues

Retinoid Hormones

• Derived from vitamin A (retinol), which derives from –carotene
• Act on nuclear receptors affecting cell growth and differentiation in tissues with rapid growth

Thyroid Hormones

• Thyroid hormones (T3 and T4) have iodine atoms
• T4 gets converted to T3
• Act on nuclear receptors changing enzyme expression and energy regulation
• Lack of iodine can lead to goiter

Nitric Oxide

• Made from arginine
• Acts locally near release
• Enters cells and activates guanylyl cyclase
• Increases cGMP, relax smooth muscle and lowering blood pressure

Major Endocrine Glands

• Brain (hypothalamus, pituitary)
• Thyroid, parathyroid
• Adrenals, pancreas, adipose tissue
• Ovaries/Testes

Top-Down vs. Bottom-Up Hormonal Signaling

• Top-down signals originate in the brain and affect the body
• Bottom-up signals originate in the body and affect the brain

Hormones and Target Tissues

• Overview of hormone pathways, targets, roles

Muscle Metabolism

• Stores relatively small amounts of glycogen (1–2% of mass)
• Heart muscle is primarily aerobic
• Light activity uses fatty acids and ketone bodies
• Heavy activity uses glycogen and produces lactate

Cori Cycle

• Cycle between muscle and liver involving lactate
• Muscle uses glycogen for energy during activity
• Liver converts lactate into glucose for further use
• Uses ATP during recovery

Brain Metabolism

• Requires constant energy from glucose or ketone bodies
• No glycogen storage, relying on incoming energy sources
• Important for action potentials

Blood Insulin Increased (Well-fed State)

• Increased insulin to control blood glucose levels
• Glucagon decreases, allowing for glucose being used by cells

The Well-Fed Lipogenic Liver

• Insulin promotes glycogen synthesis, inhibits fat breakdown in adipose tissue
• Muscle cells take up glucose
• Liver takes up glucose, synthesizes glycogen
• Adipocytes, take up glucose, use it to create glycerol for fat synthesis

Effects of Insulin on Blood Glucose

• Promotes glucose uptake in muscle, adipose tissue
• Enhances glycogen synthesis in liver and muscle
• Suppresses glycogen breakdown
• Promotes glycolysis, and acetyl-CoA production

Insulin and Amylin

• Insulin and amylin are secreted together by beta cells
• Amylin affects gastric emptying, glucagon secretion and appetite

The Fasting State

• Glycogenolysis and gluconeogenesis contribute to the glucose levels
• Adipose releases fatty acids
• Muscle breaks down proteins, amino acids to glucose and ketone bodies
• Brain uses ketone bodies and glucose for function

ATP Equivalents

• ATP produced from glucose metabolism and ketone bodies
• Caloric values associated with carbohydrates, protein, and fats

Available Metabolic Fuels

• Comparison of metabolic fuel availability between normal and obese individuals

Fuel Metabolism in Prolonged Fasting and Type 1 Diabetes

• Fat becomes the primary energy source when glycogen stores are depleted
• Ketone bodies increase while blood glucose decreases
• Insulin output decreases but glucagon increases

Graph of Plasma Concentrations during Starvation

• Graph of various substances' concentrations over days of starvation

Tissues Involved (Well-fed vs. Starvation)

• Shows the involved metabolic pathways in the body during both states

Drugs and Diseases

• Includes diabetes, inflammation, and various other conditions, and their respective drug therapy

Nutritional Quality of Proteins

• Essential amino acids simultaneously needed for protein synthesis
• Quality assessed through essential amino acids, digestibility, and chemical score
• Animal proteins generally have higher biological value

Nutritional Quality of Proteins (Quality, Source)

• Comparing the chemical score and biological value of proteins in various food sources
• Animal sources tend to have higher biological values.

Plant Protein Quality

• Plant proteins often have lower biological value than animal sources
• Combining plant protein sources with complementary amino acid profiles can be beneficial

Nutritional Quality of Proteins, Obesity

• Emphasizes that obesity results from excess caloric intake over expenditure
• 1 pound of fat equates to 3500 calories