Biology Chapter: Cells and Organisms

Cells: The Basic Units of Life

• Cells are the fundamental building blocks of all living organisms.
• They are the smallest unit capable of independent life.
• Cells can be distinguished by size, shape, structure, and function.

Types of Organisms

• Prokaryotic: Lack a nucleus, single-celled, small size, examples include Bacteria and Archaea.
• Eukaryotic: Have a nucleus, can be single-celled or multicellular, larger in size, examples include Protista, Fungi, Plantae, and Animalia.

The Chemical Components of Cells

• Essential Elements: C, H, O, and N make up the majority of an organism's atoms.
• Electrolytes: K, Na, Cl, Mg, P, Ca, Fe, and I are important for various cellular functions.
• Covalent Bonds: Electrons are shared equally or unequally between atoms.
  • Non-polar: Electrons are shared equally (e.g., C-C, C-H bonds).
  • Polar: Electrons are shared unequally due to differences in electronegativity.
• Ionic Bonds: Atoms gain or lose electrons, forming charged ions that attract each other.
• Hydrogen Bonds: Weak interactions between a hydrogen atom and a highly electronegative atom (like oxygen or nitrogen).

Essential Molecules

• Proteins: Large, complex molecules made up of amino acids.
  • Functions: Regulation, structure, signaling, transport, catalysis, motor proteins.
  • Enzymes: Biological catalysts that speed up chemical reactions.
    • Specificity: Enzymes catalyze specific reactions.
    • Reversible reactions: Enzymes can facilitate both forward and reverse reactions.
    • Coenzymes: Some enzymes require a coenzyme or cofactor for activity.
    • Factors affecting enzyme activity: Temperature, pH, enzyme concentration, substrate concentration.
• Nucleotides: Monomers of nucleic acids (DNA and RNA).
  • Components: Nitrogenous base, sugar, phosphate groups.
  • RNA: A, G, C, U, mostly single-stranded.
  • DNA: A, G, C, T, double-stranded helix.
• ATP: Adenosine triphosphate is the primary energy carrier in cells.

Eukaryotic Cell Structure

• Cell Wall: Found in plants, fungi, and bacteria, provides protection, structure, and support.
  • Composed of: Cellulose (plants), chitin (fungi), peptidoglycan (bacteria).
• Cell Membrane: Encloses the cell and regulates what enters and exits.
  • Composed of: Phospholipid bilayer with embedded proteins.
• Cytoplasm: The gel-like substance within the cell that houses the organelles.
• Nucleus: Contains the cell's genetic material (DNA).
• Ribosomes: Sites of protein synthesis.
• Endoplasmic Reticulum (ER): Network of membranes involved in protein synthesis and lipid metabolism.
  • Rough ER: Has ribosomes attached, involved in protein synthesis.
  • Smooth ER: Lacks ribosomes, involved in lipid synthesis and detoxification.
• Golgi Apparatus: Processes and packages proteins and lipids for secretion or delivery to other organelles.
• Lysosomes: Contain digestive enzymes that break down cellular waste products and ingested materials.
• Peroxisomes: Small vesicles involved in fatty acid and alcohol metabolism, cholesterol synthesis, and amino acid digestion.
• Mitochondria: Powerhouses of the cell, responsible for cellular respiration and energy production.
• Chloroplasts: Found in plant cells, responsible for photosynthesis.
• Vacuoles: Storage compartments for water, nutrients, and waste products.
• Cilia and Flagella: Hair-like or whip-like structures for movement.
• Cytoskeleton: Network of protein fibers that provides structural support and enables cell movement.
  • Microtubules: Hollow tubes made of tubulin, involved in cell shape, organelle movement, and cell division.
    • Functions: Mitotic spindle formation, cilia and flagella structure, viral movement.
  • Microfilaments: Solid rods made of actin, involved in muscle contraction, cell shape, and movement.
    • Functions: Muscle contraction, cytoplasmic streaming.
  • Intermediate Filaments: Resilient networks of protein fibers, providing structural support and resisting mechanical stress.
    • Functions: Structural support, resistance to mechanical stress.

Explore the fundamental units of life with this quiz on cells. You will learn about the differences between prokaryotic and eukaryotic organisms and the essential chemical components that make up cells. Test your understanding of these foundational concepts in biology.