Chapter 24: Metabolism Overview in BIOL2111

Macronutrients

Nutrients required in large amounts, including carbohydrates, lipids, and proteins.

Micronutrients

Nutrients required in smaller amounts, including vitamins and minerals.

Water

60% by volume of food eaten.

Energy from Carbohydrates

4 kcal/g.

Energy from Lipids (Fats)

9 kcal/g.

Energy from Proteins

4 kcal/g.

Types of Carbohydrates

Includes monosaccharides, disaccharides, and polysaccharides.

Glucose

Used for ATP production by cells; excess is converted to glycogen or fat.

Triglycerides

Main form of fat storage in the body.

Saturated Fats

Found in animal products like meat and dairy.

Unsaturated Fats

Found in seeds, nuts, and most vegetable oils.

Cholesterol

Dietary source includes egg yolk, meats, and produces 85% of blood cholesterol.

Essential Fatty Acids

Linoleic Acid (Omega-6) and Linolenic Acid (Omega-3).

Complete Proteins

Proteins that contain all essential amino acids, such as eggs and milk.

Incomplete Proteins

Proteins that lack one or more essential amino acids, such as legumes and nuts.

Vitamins

Organic compounds that act as coenzymes and antioxidants.

Water Soluble Vitamins

Includes B-complex and Vitamin C.

Fat Soluble Vitamins

Includes Vitamins A, D, E, and K.

Minerals

Inorganic elements required for various bodily functions.

Anabolism

Metabolic process that builds up molecules.

Catabolism

Metabolic process that breaks down molecules.

ATP Synthesis

Includes substrate-level phosphorylation and oxidative phosphorylation.

Glycolysis

Conversion of glucose to 2 pyruvic acids, occurring in the cytosol.

Citric Acid Cycle

Occurs in the mitochondrial matrix and involves 8 steps.

Lipid Oxidation

Involves glycerol and fatty acids for energy production.

Ketosis

Condition where ketones accumulate in the blood, often due to starvation or carbohydrate restriction.

Protein Synthesis

Occurs at ribosomes where peptide bonds link amino acids.

Hormone levels change with aging

Alters rate of protein anabolism

Formation

Lifetime = cells synthesize ~500 - 1000 lbs of protein

Nonessential amino acids

Keto acids from citric acid cycle + amine groups

Complete set of amino acids

Required for protein synthesis

Absorptive State

Carbohydrates used = ATP, stored = Glycogen or Fat

Fats in Absorptive State

Chylomicrons in lymph; some fatty acids & glycerol = anabolic; most enter adipose tissue for storage

Amino Acids in Absorptive State

Liver = deaminates AA → Keto acids; liver uses some AA to synthesize plasma proteins; most AA used to synthesize proteins in other body cells

Insulin

Director of events in the absorptive state; secreted by pancreatic Islet Beta cells

Diabetes Mellitis

Disorder characterized by inadequate insulin production or abnormal insulin receptors

Effects of Diabetes Mellitis

Glucose = unavailable to most cells; blood glucose levels high; large amounts glucose in urine

Postabsorptive State

Blood glucose sources include glycogenolysis in liver and skeletal muscle, lipolysis in adipose tissue & liver, and catabolism of cellular proteins

Glycogenolysis

Liver glycogen stores = 1st line of reserves; can maintain blood sugar levels ~ 4 hrs

Glucagon

Targets liver & adipose tissue; stimulates gluconeogenesis & glycogenolysis in hepatocytes and lipolysis in adipocytes

Cholesterol Function

Structural basis of bile salts, & steroid hormones; major component of plasma membranes

Cholesterol Sources

15% from diet; 85% liver (mostly) & other body cells (intestinal cells)

Cholesterol Levels

Total < 200 mg/dL; HDL > 60 mg/dL; LDL < 160 mg/dL

Energy Balance

Energy intake = Energy output for weight stability; energy intake > energy output leads to weight gain; energy intake < energy output leads to weight loss

Body Mass Index (BMI)

BMI = wt(lb) x 705/ht (inches)²; 25 - 30 = Overweight; > 30 = Obese

Short-Term Controls of Food Intake

Neural controls include vagus nerve; hormonal controls include insulin & CCK vs ghrelin, glucagon, epinephrine

Long-Term Controls of Food Intake

Insulin inhibits NPY release; Leptin secreted by adipose tissue in response to ↑ in body fat mass

Basal Metabolic Rate (BMR)

Measured in post-absorptive state after > 12 hrs fasting, reclined, at comfortable temperature; reported in Kcal/m²/h

Heat Exchange

Includes radiation, conduction, convection, and evaporation

Temperature Regulation

Heat promoting mechanisms include cutaneous vasoconstriction, shivering, and adrenal medulla release of E and NE

Hypothermia

Low body temp due to prolonged uncontrolled exposure to cold; signs include decreased vital signs and drowsiness

Fever

Controlled hyperthermia resulting from infection, cancer, allergic reaction, or CNS injury

Phenylketonuria (PKU)

Genetic disorder where tissue cells are unable to use AA phenylalanine due to a defective enzyme

Galactosemia

Inability to transform galactose to glucose due to abnormal or lack of needed liver enzymes

Glycogen Storage Disease

Normal glycogen synthesis but lacking an enzyme to convert back to glucose, leading to excessive glycogen storage

Metabolic Syndrome

Cluster of 5 risk factors that double the risk of heart disease & stroke and increase risk of Type II DM 5x