energy requirements living tissue is maintained by constant expenditure of energy (atp). atp is...

Energy Requirements

• Living tissue is maintained by constant expenditure of energy (ATP).

• ATP is Indirectly generated from – glucose, fatty acids, ketones, amino acids and

other organic molecules.

• Energy of food is commonly measured in kilocalories.

Anabolism• Synthesis (build up):

– Synthesizing:

• Proteins.

• Triglycerides.• Glycogen.

• Must occur constantly to replace molecules that are hydrolyzed.

Catabolism• Hydrolysis (break down):

– Hydrolysis reactions.

A + B + H2O OH A + H B

Gluconeogenesis − from stored Glycogen = Glycogenolysis− from stored fat = Lipolysis

Regulation of Adipose Tissue

Adipocytes secrete Leptin:

This Hormone signals the hypothalamus to indicate the level of fat storage.

Neuropeptides that stimulate appetite are inhibited by leptin.

Obesity• Obesity is often diagnosed by using using a body mass

index (BMI).• BMI = w

h 2

• W = weight in kilograms• H = height in meters

• Obesity in childhood is due to an increase in both the size and the # of adipocytes.

• Obesity defined as BMI > 30.

• Healthy weight as BMI between 19 – 25.

Energy Regulation of Pancreas

• Islets of Langerhans3 cell types:

Alpha or A glucagon.Beta or B insulin.Delta or D somatostatin.

Regulation of Insulin and Glucagon

Increased plasma glucose.• Glucose binds to receptors in cells stimulating

production and release of insulin.

Insulin: • Stimulates skeletal muscle cells and adipocytes to

incorporate a facilitated diffusion carrier for glucose.

Promotes anabolism.

Regulation of Insulin and Glucagon• Parasympathetic Nervous System:

– Stimulates insulin secretion.

• Sympathetic Nervous System:– Stimulates glucagon secretion.

• Gastric inhibitory peptide – Slows stomach functions– Stimulates insulin secretion.

• GLP-1(glucagon-like peptide-1 ):– Stimulates insulin secretion.– Slows stomach functions

• CCK: (released by duodenal mucosa when food is present) in it – causes increse saitiery (to stop eating ) Stimulates insulin secretion.

The food Absorbing State

• Insulin = major hormone promoting anabolism

• Plasma insulin increases.– Promotes cellular uptake of glucose.– Stimulates glycogen storage in the liver and

muscles.– Stimulates triglyceride storage in adipose cells.– Promotes cellular uptake of amino acids and

synthesis of proteins.

After Absorption

Maintaining plasma glucose concentration.•Plasma Glucagon increases:

–Stimulates glycogenolysis in the liver

–Stimulates gluconeogenesis (glucose from fat & protein).

–Skeletal muscle, heart, liver and kidneys use fatty acids as major source of fuel.

Diabetes Mellitus

• Chronic high plasma glucose.

• 2 forms of diabetes mellitus:– Type I: Insulin dependent diabetes (IDDM)– Type II: non-insulin dependent diabetes

(NIDDM)

Glucocorticoids

Support the effects of increased glucagon.

• Promote lipolysis and ketogenesis.

• Promote protein breakdown in the muscles.

• Promote liver gluconeogenesis.

Growth Hormone

• Somatotropin.• Inhibited by somatostatin.• Stimulates growth in children and adolescents.• Stimulated by:

– GHRH.– Increase in plasma amino acids. – Decrease in plasma glucose.

• Pulsitile, increasing during sleep, decreased during day.