N1-BIO 121: Anatomy & Physiology II - Chapter 25: Nutrition Study Notes

N1-Unit 4: Nutrition in Anatomy & Physiology II

Nutrients

• Nutrient:

  • Definition: A substance present in food that is utilized by the body for promoting growth, maintenance, and repair.

• Essential Nutrients:

  • Definition: Substances that the body cannot synthesize and must be included in the diet.

• Micronutrients:

  • Definition: Vitamins and minerals that are required by the body in very small amounts.

Carbohydrates

Carbohydrate Structure

• Types of Carbohydrates:

  • Monosaccharides:

  • Definition: Simple sugars that are water-soluble.

  • Examples:

    • Glucose, Fructose, Galactose

    • Chemical formula: C6H{12}O_6

  • Disaccharides:

  • Definition: Composed of two monosaccharides; water-soluble.

  • Examples:

    • Sucrose, Lactose, Maltose

    • Chemical formula for disaccharides: C{12}H{22}O_{11}

  • Complex Carbohydrates:

  • Definition: Long chains of monosaccharides; not water-soluble (insoluble).

  • Examples: Starch, Cellulose, Glycogen

Carbohydrate Functions

• Cellular Fuel:

  • Starch, glycogen, and disaccharides are broken down into monosaccharides for absorption.

  • Monosaccharides can be converted to glucose by the liver, which is used to produce ATP (adenosine triphosphate) during cellular respiration.

• Energy Storage:

  • When energy is not immediately needed, monosaccharides are combined into long chains of glycogen for storage in the liver and skeletal muscle, until needed for ATP production.

  • Excess carbohydrates, when glycogen stores are full, are converted to fat and stored in adipose tissues.

• Nucleic Acid Synthesis:

  • Monosaccharides are needed for the formation of ribose and deoxyribose, sugars found in RNA and DNA.

Other Functions of Carbohydrates

• Glycosylation:

  • Definition: The process of binding carbohydrates to proteins or lipids, forming glycoproteins and glycolipids.

  • Importance: Necessary for the correct function of certain structures, such as proper protein folding and functioning of glycoproteins on cell membrane surfaces.

• Roughage (Fiber):

  • Definition: The body cannot digest cellulose, thus it passes through the digestive system and adds bulk to feces—important for healthy digestion.

Lipids

Introduction to Lipids

• Types of Lipids:

  • Triglycerides

  • Steroids

  • Phospholipids

  • Eicosanoids

• Dietary Composition:

  • About 95% of dietary lipids are triglycerides, while the others also play crucial roles.

• Hydrophobic Nature:

  • All lipids are hydrophobic (water-fearing) substances.

Essential Fatty Acids

• Types:

  • Alpha-linolenic acid: Omega-3 fatty acid.

  • Linoleic acid: Omega-6 fatty acid.

• Dietary Importance:

  • Essential fatty acids cannot be synthesized by the body, thus must be obtained through diet; good sources include seeds, nuts, and legumes.

• Functions:

  • Necessary for the formation of important eicosanoids, such as prostaglandins, which are vital for blood clotting.

Steroids

• Structure:

  • Composed of four hydrocarbon rings with various other groups attached.

• Cholesterol:

  • An important component of cell membranes and a precursor for steroid hormones and bile salts.

  • Dietary cholesterol is primarily derived from animal sources, particularly liver and egg yolks (absent in plants).

  • Functions:

  • Bile salts facilitate digestion and absorption of lipids.

  • Hormones: Includes sex hormones like estrogen, progesterone, and testosterone.

Lipoproteins

• Functionality of Lipoproteins:

  • Fats travel around the body in association with cholesterol and proteins, forming lipoproteins.

• Types:

  • High-density lipoproteins (HDL):

  • Known as "good cholesterol"; efficiently transports fats throughout the body.

  • Low-density lipoproteins (LDL):

  • Referred to as "bad cholesterol"; can tend to form plaque deposits on blood vessel walls.

Triglycerides

• Composition:

  • Composed of a glycerol backbone and three fatty acid chains.

  • Mainly consist of carbon and hydrogen with minimal oxygen.

• Functions:

  • Provide protection and insulation via body fat.

  • Facilitate absorption of fat-soluble vitamins.

  • Serve as an energy source for ATP formation.

Proteins

Introduction to Proteins

• Composition:

  • Made up of chains of subunits known as amino acids.

  • Each amino acid is connected to another via peptide bonds.

• Amino Acid Structure:

  • Composed of:

  • Amine Group: NH_2

  • Carboxyl (Acid) Group: -COOH

  • R-group: Varies and makes each amino acid unique.

• Total Amino Acids:

  • There are twenty amino acids that exist naturally, which can combine in various ways to form proteins.

Types of Amino Acids

• Essential Amino Acids:

  • Must be obtained through diet as the body cannot synthesize them.

  • Includes the following: Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine.

• Conditionally Essential Amino Acids:

  • Cannot be synthesized in premature infants or individuals with specific metabolic diseases.

  • Includes: Arginine, Cysteine, Glutamine, Glycine, Proline, Tyrosine.

• Nonessential Amino Acids:

  • The body can synthesize these from other protein sources.

  • Includes: Alanine, Aspartic Acid, Asparagine, Glutamic Acid, Serine.

Nutrition

• Dietary Sources:

  • Complete Proteins:

  • Contain all essential amino acids; sources include meat, fish, poultry, milk, cheese, and eggs.

  • Incomplete Proteins:

  • Missing one or more essential amino acids; sources include rice and beans.

• Dietary Requirements:

  • Ideally constitute 10-35% of total daily kilocalories.

• Nitrogen Balance:

  • Defined as the nitrogen content of ingested protein being equal to nitrogen excreted in urine and feces.

• Negative Nitrogen Balance:

  • Results from inadequate protein intake.

Micronutrients

Vitamins

• Definition:

  • Organic molecules that exist in small quantities in foods.

• Essential Vitamins:

  • Must be obtained through diet.

• Provitamins:

  • Parts of vitamins convertible into functional vitamins by the body;

  • Examples include:

  • Beta carotene (converted into Vitamin A)

  • 7-dehydrocholesterol (converted into Vitamin D)

  • Tryptophan (converted into Niacin or Vitamin B3).

• Coenzymes:

  • Many vitamins function as cofactors—non-protein compounds binding to enzymes called coenzymes (organic cofactors).

Vitamin Classifications

• Fat-Soluble Vitamins:

  • Include Vitamins A, D, E, K

  • Absorbed along with lipids in the digestive tract.

  • Can be stored in the body for extended periods; excessive amounts can lead to toxicity.

• Water-Soluble Vitamins:

  • Include B vitamins and Vitamin C.

  • Absorbed with water in the digestive system.

  • Typically excreted in urine after a short duration, which is why B-complex vitamins often color urine bright yellow.

Minerals

• Definition:

  • Inorganic nutrients essential for normal metabolic functionalities.

• Dietary Sources:

  • Obtainable from animal and plant sources; however, minerals bound to plant fibers can be challenging to absorb.

• Functions of Minerals:

  • Establish resting membrane potentials.

  • Generate action potentials.

  • Provide strength to bones and teeth (notably phosphorus and calcium).

  • Serve as buffers.

  • Involved in osmotic (water) balance.

  • Act as cofactors (e.g., magnesium, manganese, zinc, cobalt, copper).

  • Component of hemoglobin (iron).

Mineral Nutrition

Important Minerals

Edition Notes

• Edition Date: 7/15/25

• Updates: Checked for accuracy and clarity.

• Contributors:

  • Stephen Taylor: Corrections, updates, suggestions, and edits.

  • Julie Underwood: Produced and edited content.

  • Laura Bianco

  • John Kaminski

  • The BIO 121 cross college team