Nutrition: Carbohydrates Overview

Introduction

• Four primary food substances are essential to maintain human life: carbohydrates, lipids, proteins, and water.

Carbohydrates

• Composed of carbon, hydrogen, and oxygen.
• Found in rice, bread, fruit, and other food sources.
• Three classes: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides (Simple Sugars)

• Glucose: Sweetest simple sugar, broken down during respiration to release energy.
• Fructose: Commonly found in fruit and honey.
• Galactose: Intermediate in the digestion of starch.

Disaccharides (Double Sugars)

• Maltose: Composed of glucose + glucose, commonly known as malt sugar.
• Sucrose: Composed of glucose + fructose, commonly known as table sugar.

Polysaccharides

• Starch: Major food reserve in plants, composed of glucose.
• Glycogen: Major carbohydrate stored in animals, composed of glucose.
• Cellulose: Makes up the cell wall of plants, composed of glucose, indigestible by humans.

Water

• Makes up 75% of the human body.
• A vital substance for the body.

Functions of Water

• Good solvent:
  • Medium for metabolic reactions.
  • Dilutes waste substances to prevent them from harming the body.
• Temperature regulator:
  • Water has a high heat capacity, helping to maintain body temperature.
• Strong surface tension:
  • Strong attraction between water molecules.
  • Allows water to rise readily by capillary action.
• Transporter: Water in the blood carries nutrients from food to tissues throughout the body.
• Lubricant:
  • Synovial fluid lubricates joints for easy movement.
  • Water moistens food during digestion, aiding in swallowing and waste elimination.

ATP (Adenosine Triphosphate)

• The primary source of energy for biological activities of the cell.
• ATP ⇔ ADP + Pi + energy.
• ADP (adenosine diphosphate) functions as an energy storage mechanism.

Nucleic Acids

• Two types: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).
• DNA acts as the genetic material of all organisms.
• The relationship between DNA, RNA, and protein is described by the Central Dogma:
  • Transcription: DNA is transcribed into RNA.
  • Translation: RNA is translated into protein.

Mineral Salts and Ions

• Mineral salts and ions contribute to various essential functions.

Examples:

• Calcium: Constituent of bones and teeth, involved in blood clotting, and muscle contraction.
• Chlorine: Maintains the balance between anion and cation.
• Phosphate: Constituent of nucleic acids, ATP, bones, and teeth.
• Fluorine: Important for improving tooth decay resistance.
• Iodine: Component of growth hormone and thyroxine.
• Iron: Constituent of many enzymes, haemoglobin, and myoglobin.

Cells & Tissues

• The basic unit of life is the cell.

Generalized Human Cell & Organelles

• Cell Membrane/Plasma Membrane: Covers the surface of cells, encloses cytoplasm. Composed of a phospholipid bilayer with embedded proteins. Functions in controlling the movement of substances into and out of the cell.
• Cytoplasm: Fluid, jellylike substance between the cell membrane and the nucleus, where organelles are suspended. Function: Serves as a matrix for chemical reactions.
• Nucleus: The largest organelle; contains DNA. Functions: directs cell activities and contains DNA for protein synthesis.
• Mitochondrion: Rod-shaped structure bound by two membranes, responsible for releasing energy from food molecules and transforming it into ATP.
• Endoplasmic Reticulum (ER): A network of interconnected membranes throughout the cytoplasm.
  • Rough ER (RER): Contains ribosomes, helps synthesize proteins.
  • Smooth ER (SER): Lacks ribosomes, involved in the synthesis and metabolism of carbohydrates, lipids, and other non-protein materials.

Summary of Organelle Functions:

• Plasma (Cell) Membrane: Controls materials in and out of the cell.
• Cytoplasm: Serves as a matrix substance for chemical reactions.
• Endoplasmic Reticulum (ER):
  • Rough ER: Assists protein synthesis.
  • Smooth ER: Metabolizes nonpolar compounds.
• Ribosome: Protein synthesis.
• Golgi Complex: Synthesizes carbohydrates and packages molecules for secretion.
• Mitochondrion: Transforms energy from food to ATP.
• Lysosome: Digests foreign molecules, worn, and damaged organelles.
• Nucleus: Contains DNA and directs cell activity.
• Nuclear Membrane: Controls material in and out of the nucleus.
• Nucleolus: Produces ribosomal RNA for ribosomes.

Levels of Cellular Organization

• Chemical level: Atoms combine to form molecules (e.g., oxygen, hydrogen, proteins, carbohydrates).
• Cellular level: Molecules make up cell organelles (e.g., nucleus, cell membrane), resulting in cells (e.g., neurons, muscle cells).
• Tissue level: Similar cell types grouped together (e.g., nervous tissue, muscle tissue).
• Organ level: Different tissue types working together (e.g., heart, liver, brain, lung).
• Organ system level: Different organs working together to perform a specific function (e.g., nervous system, digestive system).
• Organismal level: The complete, living organism (e.g. a human).

Levels of Organization in the Body (Summary)

• Chemical: Atoms form molecules.
• Cell: Molecules form cells.
• Tissue: Similar cells grouped together.
• Organ: Different tissues working together.
• Organ system: Different organs working together to perform a specific function.
• Organism: All organ systems working together.

The Primary Tissues

• Four types of tissues found in the human body.

1. Muscle Tissue:

• Specialized for contraction.
• Types:
  • Skeletal Muscle: Attached to bones by tendons, responsible for voluntary movement.
  • Cardiac Muscle: Found in the heart, responsible for involuntary pumping of blood.
  • Smooth Muscle: Found in the digestive tract, blood vessels, and urinary and reproductive systems, responsible for involuntary movement.

2. Nervous Tissue:

• Composed of neurons (nerve cells) and supportive cells.
• Neurons: Responsible for generating and conducting electrical impulses and neural signals.
• Supportive Cells: Provide support and nourishment for neurons.

3. Epithelial Tissue:

• Two categories: epithelial membranes and glands.
• Epithelial Membranes: Cover body surfaces and line the cavities (lumens) of hollow organs.
  • Simple Membranes: One cell layer thick.
  • Stratified Membranes: Multiple cell layers thick.
• Types based on cell shape:
  • Squamous Epithelium: Flattened cells, found in capillary walls, pulmonary alveoli, and the epidermis of skin.
  • Columnar Epithelium: Tall, column-shaped cells, found lining the digestive tract.
  • Cuboidal Epithelium: Cube-shaped cells, found lining kidney tubules and ducts of exocrine glands.
  • Transitional Epithelium: Can stretch, found in the bladder and ureters.
• Replacement of Cells: These epithelial layers are constantly losing and renewing cells.

4. Connective Tissue:

• Consists of connective tissue cells and large amounts of extracellular material located in the spaces between cells.
• Types:
  • Connective Tissue Proper: Contains a matrix of collagen and tissue fluid.
    • Loose Connective Tissue (Areolar Tissue): Found in the dermis of skin.
    • Dense Connective Tissue: e.g., tendons and ligaments.
  • Cartilage: Provides support and flexibility, often found in joints.
    • Hyaline Cartilage: Glass-like, found in the nose, trachea, and articular joints.
    • Elastic Cartilage: Flexible, found in the ear and epiglottis.
    • Fibrocartilage: Tough, found in intervertebral discs.
  • Bone: Hard connective tissue responsible for support and protection.
  • Blood: Unique connective tissue made up of plasma and blood cells.

Chemistry of Life

• Four essential food substances in humans: carbohydrates, lipids, proteins, water
• Carbohydrates: contain carbon, hydrogen and oxygen; found in rice, bread, fruits
  • Three classes:
    • Monosaccharides (simple sugars): Example: glucose, fructose. Glucose is the major end-product of carbohydrate digestion, fructose is commonly found in fruits and honey.
    • Disaccharides (double sugars): Examples: maltose, sucrose. Maltose is an intermediate in starch digestion, sucrose is commonly known as table sugar.
    • Polysaccharides: Examples: starch, glycogen, cellulose. Starch is a major food reserve in plants, glycogen is the major carbohydrate stored in animals, cellulose is indigestible by humans and makes up the cell wall of plants.
• Lipids: made up of carbon, hydrogen, and oxygen; insoluble in water, but soluble in organic solvents like alcohol.
  • Two types:
    • Fats: semi-solid at room temperature
    • Oils: liquid at room temperature
  • Triglyceride: a subcategory of lipid made up of three fatty acid molecules and one glycerol molecule
• Lipids have various functions in the body: food reserve and energy source, structural materials (phospholipids are important cell membrane components), metabolic regulators (e.g., sex hormones), water-proof layer (sebaceous glands secrete oil in mammals), and protection (fat surrounds internal organs like the kidney, acting as shock absorbers).
• Proteins: contain carbon, hydrogen, oxygen, and nitrogen; sometimes contain sulfur and phosphorus.
  • The basic units of proteins are amino acids.
  • Amino acids join together to form polypeptides.
  • Polypeptides link to form proteins.
• Denaturation: the loss of a protein molecule's specific three-dimensional conformation. This leads to the loss of the protein's biological activity.
  • The amino acid sequence remains unaffected during denaturation.
• Renaturation: regaining the biological activities of a protein.
• Factors causing protein denaturation: heat, radiation, extreme pH, mechanical force, chemicals (e.g., nonpolar solvents and detergents).
• Water: makes up 75% of the human body; vital substance
• Water functions:
  • Good solvent: a medium for metabolic reactions, dilutes waste substances preventing harm to the body
  • Temperature regulator: water has a high heat capacity, helps maintain body temperature
  • Strong surface tension: strong attraction between water molecules, water rises readily by capillary action.
  • Transporter: water in the blood carries nutrients from food to tissues throughout the body
  • Lubricant: synovial fluid helps joints move easily, water moistens food in the digestive tract (e.g., saliva makes swallowing easy).
• ATP (adenosine triphosphate): the source of energy for biological activities in a cell.
  • ATP <=> ADP + Pi + energy
  • ADP (adenosine diphosphate)
• Converting ADP to ATP is a method for energy storage until needed.
• Nucleic acids: two types:
  • Deoxyribonucleic acid (DNA): acts as the genetic material of all organisms.
  • Ribonucleic acid (RNA)
• DNA, through transcription and translation processes leads to the synthesis of proteins.
• Mineral Salts and Ions:
  • Calcium: constituent of bones and teeth, involved in blood clotting and muscle contraction
  • Chlorine: maintains the balance between anion and cation
  • Phosphate: constituent of nucleic acids, ATP, bones, and teeth
  • Fluorine: Important in improving resistance to tooth decay
  • Iodine: a component of the growth hormone and thyroxine
  • Iron: a constituent of many enzymes, hemoglobin and myoglobin

Cells & Tissues

• Cell membrane (Plasma Membrane): covers the surface of every living cell, encloses the cytoplasm; composed of two layers of phospholipid molecules (phospholipid bilayer); proteins are scattered amongst phospholipids, functioning as receptors and transport proteins.
  • Functions: controls the movement of materials into and out of the cells.
• Cytoplasm: fluid, jellylike substance between the cell membrane and the nucleus, in which organelles are suspended.
  • Functions: serves as a matrix substance for chemical reactions to occur.
• Nucleus: the largest organelle, contains the cell's DNA.
  • Functions: directs the cell's activities, contains DNA for protein synthesis
• Mitochondrion: rod-shaped structure, bound by two membranes; inner membrane is deeply folded
  • Functions: release energy from food molecules and convert energy into ATP; the number of mitochondria in the cell depends on the cell's energy needs.
• Endoplasmic Reticulum (ER): a network of interconnected membranes throughout the cytoplasm.
  • Rough ER (RER): area of ER where ribosomes are attached; Helps to synthesize proteins made by ribosomes.
  • Smooth ER (SER): area of ER where no ribosomes are attached; helps to synthesize and metabolize carbohydrates, lipids, and other non-protein materials.
• Organelle/component Function Summary:
  • Plasma (cell) membrane: controls materials in and out of the cell.
  • Cytoplasm: serves as a matrix substance for chemical reactions to occur
  • Endoplasmic Reticulum (ER): rough ER - assists protein synthesis; smooth ER - metabolize nonpolar compounds
  • Ribosome: protein synthesis
  • Golgi Complex: synthesizes carbohydrates and packs molecules for secretion
  • Mitochondrion: transforms energy from food to ATP
  • Lysosome: digests foreign molecules, worn, and damaged organelles
  • Nucleus: contains DNA and directs cell activity
  • Nuclear membrane: controls material in and out of the nucleus
  • Nucleolus: produces ribosomal RNA for ribosomes

Levels of Organization in the Body

• Levels of Cellular Organization:
  • Atoms: e.g., oxygen (O), hydrogen (H)
  • Molecules: e.g., proteins, carbohydrates
  • Cell organelles: e.g., nucleus, cell membrane
  • Cellular level: examples: neurons, muscle cells
  • Cell differentiation: the process that cells develop into different cell types
  • Tissue level: examples: nervous tissue, muscle tissue
  • Organ level: examples: heart, liver
  • Organ system level: examples: nervous system, digestive system
  • Organismal level: an example is the human body

Chemistry of Life

• Four primary food substances are essential for human life: carbohydrates, lipids, proteins, and water.

Carbohydrates

• Contain carbon, hydrogen, and oxygen.
• Found in rice, bread, fruits, etc.
• Three classes of carbohydrates
  • Monosaccharides (simple sugars): glucose, fructose
  • Disaccharides (double sugars): maltose, sucrose
  • Polysaccharides: starch, glycogen, cellulose
• Glucose is the major end-product of carbohydrate digestion and is broken down during respiration to release energy.
• Fructose is commonly found in fruit and honey.
• Maltose is an intermediate in the digestion of starch.
• Sucrose is commonly known as table sugar.
• Starch is the major food reserve in plants.
• Glycogen is the major carbohydrate stored in animals.
• Cellulose is indigestible by humans and makes up the cell wall of plants.

Lipids

• Made up of carbon, hydrogen, and oxygen.
• Insoluble in water but dissolve readily in organic solvents like alcohol, acetone, and ethers.
• Two types of lipids:
  • Fats (semi-solid at room temperature)
  • Oils (liquid at room temperature)
• Triglycerides are a subcategory of lipids made up of three fatty acid molecules and one glycerol molecule.

Functions of Lipids

• Food reserve and energy source: fats are important food reserve materials and are used when carbohydrate storage is depleted.
• Structural materials: phospholipids are essential components of cell membranes.
• Metabolic regulators: some hormones are lipids, such as sex hormones.
• Water-proof layer: sebaceous glands in mammals secrete oil to waterproof the skin.
• Protection: fat surrounding internal organs acts as shock absorption.

Proteins

• Made up of carbon, hydrogen, oxygen, and nitrogen.
• Sometimes contain other elements: sulfur and phosphorus.
• The basic units of protein are called amino acids.
• Amino acids join together to form polypeptides.
• Polypeptides link together to form proteins.

Denaturation and Renaturation

• Denaturation: the loss of a protein molecule's specific three-dimensional conformation.
  • The amino acid sequence of the protein remains unchanged.
  • This leads to the loss of the protein's biological activities.
• Renaturation: the regain of the biological activities of a protein molecule.

Factors Causing Protein Denaturation

• Heat or radiation
• Extreme pH
• Mechanical force
• Chemicals (e.g., nonpolar solvents and detergents)

Mineral Salts and Ions

• Calcium: constituent of bones and teeth, involved in blood clotting and muscle contraction.
• Chlorine: maintains the balance between anions and cations.
• Phosphate: constituent of nucleic acids, ATP, bones, and teeth.
• Fluorine: important in improving resistance to tooth decay.
• Iodine: component of growth hormone and thyroxine.
• Iron: constituent of many enzymes, hemoglobin, and myoglobin.

Cells and Tissues

• The cell membrane (plasma membrane) encloses the cytoplasm and controls the movement of materials into and out of the cell.
• The cytoplasm is a fluid, jellylike substance between the cell membrane and the nucleus where organelles are suspended.
• The nucleus is the largest organelle containing the DNA of the cell.
• Mitochondria are rod-shaped structures that release energy from food molecules and transform it into ATP.
• The endoplasmic reticulum (ER) is a network of interconnected membranes throughout the cytoplasm.
  • Rough ER (RER) has ribosomes attached and helps synthesize proteins made by ribosomes.
  • Smooth ER (SER) lacks ribosomes and helps synthesize and metabolize carbohydrates, lipids, and other non-protein materials.

Organelle Functions

• Plasma (cell) membrane: controls materials in and out of the cell.
• Cytoplasm: serves as a matrix substance for chemical reactions to occur.
• Endoplasmic reticulum (ER): rough ER assists protein synthesis; smooth ER metabolizes nonpolar compounds.
• Ribosomes: protein synthesis.
• Golgi Complex: synthesizes carbohydrates and packs molecules for secretion.
• Mitochondrion: transforms energy from food into ATP.
• Lysosomes: digest foreign molecules, worn-out, and damaged organelles.
• Nucleus: contains DNA and directs cell activity.
• Nuclear membrane: controls material in and out of the nucleus.
• Nucleolus: produces ribosomal RNA for ribosomes.

Levels of Organization in the Body

• Levels of cellular organization:
  • Atoms (oxygen, hydrogen)
  • Molecules (proteins, carbohydrates)
  • Cell organelles (nucleus, cell membrane)
  • Cells (neurons, muscle cells)
• Cell differentiation: the process by which cells develop into different cell types.
• Tissue level:
  • Nervous tissue
  • Muscle tissue
• Organ level:
  • Heart
  • Liver
• Organ system level:
  • Nervous system
  • Digestive system
• Organismal level:
  • Human

Receptors

• Receptors are proteins that specifically bind chemical messengers with high affinity to convey signals from the outside of the cell to the inside (signal transduction pathway).
• Receptors can act as transcription factors to alter gene transcription.
• **
• Important Words:*
• Carbohydrate
• Protein
• Glucose
• Amino acid
• Fructose
• Denature
• Maltose
• Nucleic acid (DNA, RNA)
• Sucrose
• ATP
• Starch
• Glycogen
• Lipids
• Triglyceride
• Cell membrane
• Cytoplasm
• Mitochondria/Mitochondrion
• Nucleus

This quiz covers the essential role of carbohydrates in human nutrition. It highlights their composition, types, and sources, including monosaccharides, disaccharides, and polysaccharides. Test your knowledge on the different forms of carbohydrates and their significance in a balanced diet.