Importance of Chemical Elements

Essential Elements in Living Organisms

Living organisms are primarily composed of a small set of chemical elements, which are crucial for biological structure and function.

• Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N): Make up 96% of body mass.

• Functions:

  • Building biological molecules (e.g., proteins, DNA, lipids).

  • Running chemical reactions (enzymes, metabolism).

  • Maintaining homeostasis (ions like Na+, K+, Ca2+).

Formation of Compounds

Compounds and Their Properties

Compounds are substances formed when two or more elements chemically bond in fixed ratios, resulting in new properties.

• Examples: H2O (water), CO2 (carbon dioxide), NaCl (sodium chloride).

• Compounds have properties distinct from their constituent elements.

Types of Chemical Bonds

Bond Types and Their Characteristics

Chemical bonds are the forces that hold atoms together in molecules and compounds.

• Ionic Bonds: Transfer of electrons; strong strength. Example: NaCl.

• Covalent Bonds: Sharing of electrons; very strong. Examples: H2O, CO2.

• Hydrogen Bonds: Weak attraction between polar molecules; individually weak, collectively strong. Example: Between water molecules.

Chemical Reactions

Nature of Chemical Reactions

Chemical reactions rearrange atoms to form new substances, changing the composition of matter by breaking and forming bonds.

• Reactants → Products: The starting substances are transformed into new products.

• Example: Cellular respiration, photosynthesis.

Water & pH

Life-Supporting Properties of Water

Water is essential for life due to its unique physical and chemical properties.

• Cohesion: Water molecules stick to each other, creating surface tension.

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water stabilizes temperature by absorbing heat.

• Ice Floats: Ice is less dense than liquid water.

• Universal Solvent: Water dissolves many substances, facilitating biochemical reactions.

pH Scale, Acids, and Bases

The pH scale measures the concentration of hydrogen ions (H+) in a solution.

• Acids: pH < 7 (high H+ concentration).

• Bases: pH > 7 (low H+, high OH- concentration).

• Each pH unit: Represents a 10-fold change in acidity.

Formula:

Biological Molecules

Chemical Groups Important to Life

Functional groups are specific groups of atoms within molecules that determine their chemical properties and reactivity.

• Hydroxyl (–OH): Found in alcohols; polar.

• Carbonyl (C=O): Found in sugars.

• Carboxyl (–COOH): Found in acids.

• Amino (–NH2): Found in proteins.

• Phosphate (–PO4): Found in DNA, ATP.

• Methyl (–CH3): Involved in gene regulation.

How Cells Build Large Molecules

Cells synthesize and break down macromolecules using specific chemical reactions.

• Dehydration Synthesis: Builds polymers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

• A small set of monomers can create a huge variety of macromolecules.

Carbohydrates

Types and Functions

Carbohydrates are organic molecules composed of sugars, serving as energy sources and structural components.

• Monosaccharides: Single sugars (e.g., glucose); function as energy sources.

• Disaccharides: Two sugars (e.g., sucrose, lactose); function in energy transport.

• Polysaccharides: Many sugars (e.g., starch, glycogen, cellulose); function in energy storage and structure.

Lipids

Types and Functions

Lipids are hydrophobic molecules important for energy storage, membrane structure, and signaling.

• Fats: Long-term energy storage.

• Phospholipids: Form cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Include hormones (e.g., estrogen, testosterone) and cholesterol.

Proteins

Structure and Functions

Proteins are polymers of amino acids with diverse functions in cells.

• Structure: Four levels—primary, secondary, tertiary, quaternary.

• Functions:

  • Enzymes (catalysis)

  • Transport (e.g., hemoglobin)

  • Structure (e.g., muscle, hair)

  • Hormones (e.g., insulin)

  • Immune defense (e.g., antibodies)

Nucleic Acids

DNA and RNA

Nucleic acids store and transmit genetic information, enabling protein synthesis.

• Made of nucleotides: Each nucleotide consists of a sugar, phosphate, and base.

• DNA: Stores genetic information.

• RNA: Transmits genetic information and helps synthesize proteins.

• Central Dogma: DNA → RNA → Protein.

Cells & Microscopy

Importance of Microscopes

Microscopes revolutionized biology by allowing scientists to observe cells and their internal structures.

• Discovery of cells.

• Observation of organelles.

• Understanding cell function and structure.

Cell Theory

Principles of Cell Theory

Cell theory is a foundational concept in biology describing the properties of cells.

1. All living things are made of cells.

2. The cell is the basic unit of structure and function.

3. Cells come from pre-existing cells.

4. Energy flow occurs within cells.

5. Hereditary information is passed from cell to cell.

6. All cells have the same basic chemical composition.

Prokaryotic vs. Eukaryotic Cells

Comparison of Cell Types

Cells are classified as prokaryotic or eukaryotic based on structural features.

Cell Membrane Structure & Function

Phospholipid Bilayer and Its Roles

The cell membrane is a dynamic structure that regulates the internal environment of the cell.

• Structure: Phospholipid bilayer with embedded proteins.

• Functions:

  • Controls what enters and exits the cell.

  • Facilitates communication.

  • Provides protection.

  • Maintains homeostasis.

Compartmentalization in Eukaryotes

Role of Organelles

Eukaryotic cells contain organelles that allow for specialized functions and increased efficiency.

• Specialized functions (e.g., energy production, protein synthesis).

• Separation of incompatible reactions.

• Increased efficiency in cellular processes.

Plant vs. Animal Cells

Structural Differences

Plant and animal cells share many features but also have distinct differences.

Chloroplasts vs. Mitochondria

Organelle Functions

Chloroplasts and mitochondria are key organelles involved in energy transformation.

Cytoskeleton Components

Structure and Function

The cytoskeleton provides structural support and facilitates movement within cells.

Cilia & Flagella

Movement Structures

Cilia and flagella are cellular appendages that facilitate movement.

• Cilia: Short, numerous; move fluid across cell surface.

• Flagella: Long, few; move the cell itself.

• Both are composed of microtubules arranged in a 9+2 pattern.