Chapter 15: Biochemistry

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Chapter Overview & SLOs

What is biochemistry? Biochemistry is the branch of chemistry that studies the chemical processes and substances that occur within living organisms. It focuses on biomolecules such as carbohydrates, proteins, lipids, and nucleic acids.

Why do living organisms need food? Food provides:

• Energy for metabolism, movement, growth, and cellular processes (via ATP)
• Building blocks for growth and repair of tissues
• Nutrients to regulate bodily functions like immune response, hormone production, and enzyme activity

What is a balanced diet? A balanced diet is one that includes all essential nutrients in appropriate proportions for optimal health:

• Carbohydrates (45-65% of daily calories)
• Proteins (10-35% of daily calories)
• Fats (20-35% of daily calories)
• Vitamins and minerals (micronutrients)
• Water

What are carbohydrates? Carbohydrates are the primary energy source for living organisms. They are broken down into glucose for immediate energy and stored as glycogen in the liver and muscles for later use.

• Monosaccharides: Simple sugars like glucose ($C_6H_{12}O_6$), fructose, galactose
• Disaccharides: Two sugar units like sucrose (glucose + fructose), lactose (glucose + galactose)
• Polysaccharides: Long chains like starch, glycogen, and cellulose
• Energy yield: $4$ calories per gram
• Carbohydrate metabolism produces ATP (adenosine triphosphate), the energy currency of cells

What are proteins? Proteins are made up of amino acids and perform various essential functions in the body:

| Function | Example | Description | |----------|---------|-------------| | Structural support | Collagen | Provides strength to skin, bones, tendons, and ligaments | | Enzymatic catalysis | Amylase | Breaks down starch into sugars in the digestive system | | Oxygen transport | Hemoglobin | Carries oxygen from lungs to tissues | | Immune function | Immunoglobulins (antibodies) | Defend against pathogens and foreign substances | | Hormonal regulation | Insulin | Regulates blood glucose levels | | Muscle contraction | Actin, Myosin | Enables muscle movement | | Energy yield: $4$ calories per gram | | |

What are lipids (fats and oils)? Lipids are hydrophobic organic compounds that serve multiple functions:

• Energy storage: Provide $9$ calories per gram (more than twice the energy of carbohydrates and proteins)
• Thermal insulation: Subcutaneous fat helps maintain body temperature
• Protection: Cushions and protects delicate organs (heart, kidneys)
• Vitamin carrier: Provide essential fat-soluble vitamins: A, D, E, K
• Hormone synthesis: Required for production of steroid hormones (estrogen, testosterone)
• Cell membrane structure: Phospholipids form the bilayer of cell membranes
• Cholesterol synthesis: Important for cell membrane fluidity and hormone production

What are nucleic acids (DNA and RNA)? Nucleic acids store and transmit genetic information.

DNA (Deoxyribonucleic Acid):

• Functions as the genetic blueprint of the cell
• Stores instructions for making all proteins
• Contains four nitrogenous bases: Adenine (A), Guanine (G), Cytosine (C), Thymine (T)
• Double helix structure
• Base pairing: A-T, G-C

RNA (Ribonucleic Acid):

• Translates genetic information from DNA to synthesize proteins
• Contains bases: Adenine (A), Guanine (G), Cytosine (C), Uracil (U) (instead of Thymine)
• Types of RNA:
  • mRNA (messenger RNA): Carries genetic code from DNA to ribosomes
  • tRNA (transfer RNA): Brings amino acids to ribosomes during protein synthesis
  • rRNA (ribosomal RNA): Forms part of ribosomes

Comparison of DNA and RNA:

| Feature | DNA | RNA | |---------|-----|-----| | Full name | Deoxyribonucleic acid | Ribonucleic acid | | Sugar | Deoxyribose | Ribose | | Bases | A, G, C, T | A, G, C, U | | Structure | Double helix | Single strand | | Function | Genetic blueprint | Protein synthesis |

How do carbohydrates function as an energy source for athletes?

• Carbohydrates are broken down into glucose for immediate energy during high-intensity activity
• Excess glucose is stored in the liver and muscles as glycogen
• Glycogen stores sustain energy during prolonged exercise and delay fatigue
• Carbohydrate loading before competitions maximizes glycogen stores

These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.

• How do we identify the essential functions of proteins? Proteins provide structural support (e.g., collagen in skin, bones, tendons), act as enzymes for catalysis (e.g., amylase breaks down starch), transport molecules like oxygen (e.g., hemoglobin in blood), and perform immune functions via immunoglobulins (antibodies).
• How do we evaluate the importance of lipids in living cells? Lipids serve as energy storage ($9$ calories/gram, twice that of carbohydrates), act as thermal insulators under the skin, protect delicate organs (heart, kidneys), provide essential fat-soluble vitamins such as A, D, E, and K, and are necessary for the synthesis of hormones and cholesterol.
• How do we differentiate between the two main types of nucleic acids? DNA (deoxyribonucleic acid) serves as the genetic blueprint storing instructions in nucleotide base sequences (Adenine A, Guanine G, Cytosine C, Thymine T), while RNA (ribonucleic acid) translates this information to synthesize proteins via mRNA (messenger), tRNA (transfer), and rRNA (ribosomal).
• How do carbohydrates function as a primary energy source? Carbohydrates are broken down into glucose for immediate energy and stored in the liver and muscles as glycogen to sustain high-intensity physical activity, delay fatigue, and produce ATP through cellular respiration.

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