Cell Biology I

Cells

  • Basic structural and functional unit of life.

  • Can be unicellular or multicellular.

  • Types of cells:

    • Prokaryotic (bacteria)

    • Eukaryotic (plant and animal)

  • All cells contain:

    • Plasma membrane

    • Cytosol

    • Ribosomes

    • Chromosomes

Size and Scale

  • Sizes of various cells:

    • Human height: 10 m

    • Length of some nerve/muscle cells: 1 m

    • Common cell sizes: 10 µm (most plant and animal cells), 1 µm (most bacteria), 100 nm (ribosomes)

Body Systems

Types of Systems

  • Structural Systems: e.g., skeletal, muscular, integument, cardiovascular.

  • Coordinating Systems: e.g., nervous, endocrine.

  • Visceral Systems: e.g., digestive, respiratory, urinary, reproductive.

Hierarchical Organization

  • Cells → Tissues → Organs → Organ Systems → Organisms

  • Example: Kidneys → Urinary System

Cell Functions

  • Cells: Building blocks of life capable of nutrition intake, reproduction, energy use, growth, and environmental response.

  • Microscope required to visualize cells.

Types of Cells

  • Macrophage: Fights disease.

  • Fibroblast: Builds scar tissue.

  • Epithelial Cells: Line and cover organs.

  • Neuron: Sends electrical impulses.

  • Erythrocyte: Carries oxygen.

  • Sperm Cell: Male gamete.

  • Neutrophil: White blood cell.

  • Osteocyte: Bone cell.

  • Adipocyte: Stores fats.

  • Myocyte: Muscle cells.

Cell Membrane Structure

  • Composed of a phospholipid bilayer; selectively permeable.

  • Regulates inbound and outbound traffic through methods like:

    • Exocytosis: Secretion of large molecules.

    • Endocytosis: Intake of large molecules.

    • Passive and Active Transport: Transfers small molecules with/without energy.

Biomolecules in Cells

  • Major types: DNA, RNA, Proteins, Carbohydrates, Lipids.

  • Functions of biomolecules:

    • DNA: Genetic material.

    • RNA: Protein synthesis.

    • Proteins: Enzymes, hormones, transporters.

    • Carbohydrates: Energy storage.

    • Lipids: Membrane components, energy storage.

Nucleus

  • Largest organelle, control center of the cell.

  • Contains genetic information (DNA).

  • Surrounded by nuclear envelope with pores for material transfer.

  • Contains nucleolus, synthesizes ribosomal subunits.

Organelles

  • Membrane-bound compartments carrying out essential functions.

  • Key organelles:

    • Mitochondria

    • Ribosomes

    • Endoplasmic reticulum (rough and smooth)

    • Golgi apparatus

    • Lysosomes

Endoplasmic Reticulum (ER)

  • Network of interconnected membranes.

  • Rough ER: Studded with ribosomes; protein synthesis.

  • Smooth ER: Lipid synthesis; detoxification.

Golgi Apparatus

  • Flat, stacked membranous sacs involved in protein sorting and packing.

  • Forms secretory vesicles for protein export.