Overview of Cell Biology Concepts

Sep 17, 2024

Notes on Cell Biology Lecture

Key Concepts

  • Cells: Smallest living units of an organism.
  • Common Features of All Cells:
    • Cell membrane: Separates the cell's interior from the environment.
    • Cytoplasm: Jelly-like fluid inside the cell.
    • DNA: Genetic material of the cell.

Categories of Cells

  1. Eukaryotic Cells:
    • Have organelles, including the nucleus.
    • More complex cells found in plants and animals.
    • Organelles are specialized parts with unique functions.
  2. Prokaryotic Cells:
    • Lack a nucleus and membrane-enclosed organelles.
    • Have genetic material not contained within a nucleus.
    • Always unicellular, e.g., bacteria.

Organelles Overview

  • Organelle: A specialized part of a cell ("little organ").

Nucleus

  • Control center of the cell.
  • Contains DNA and dictates cellular activities.
  • Chromatin: Tangled form of DNA inside the nuclear membrane.
  • DNA condenses into chromosomes during cell division.
  • Contains nucleolus: Structure where ribosomes are made.

Ribosomes

  • Synthesizes (makes) proteins.
  • Can be free in cytoplasm or attached to Endoplasmic Reticulum (ER).

Endoplasmic Reticulum (ER)

  • Membrane-enclosed passageway for transporting materials.
  • Rough ER: Has ribosomes attached.
  • Smooth ER: Lacks ribosomes.

Golgi Apparatus (Golgi Body)

  • Receives proteins from ER, customizes them into usable forms (folding, adding lipids/carbohydrates).

Vacuoles

  • Sac-like structures for storage.
  • Central Vacuole (in plants): Stores water.

Lysosomes

  • Garbage collectors of the cell.
  • Contain enzymes to break down damaged cell parts.

Mitochondria

  • Powerhouse of the cell.
  • Site for cellular respiration; produces ATP (energy molecules).
  • Cells requiring more energy have more mitochondria.

Cytoskeleton

  • Maintains cell shape.
  • Composed of microfilaments (thread-like proteins) and microtubules (thin hollow tubes).

Chloroplasts

  • Found in photoautotrophic organisms (plants).
  • Site of photosynthesis; contains chlorophyll (green pigment).

Cell Wall

  • Exclusive to plant cells; provides shape, support, and protection.
  • Animal cells do not have a cell wall.

Unique Structures in Cells

  • Cilia: Microscopic hair-like projections that help trap and expel particles (e.g., in respiratory tract).
  • Flagella: Tail-like structures for cell movement (e.g., sperm cell).

Summary

  • Eukaryotic Cells: Have nucleus and membrane-bound organelles (plants, animals).
  • Prokaryotic Cells: Unicellular, lack a nucleus and organelles (bacteria).
  • All cells have cell membrane, cytoplasm, and genetic material.
  • Both plant and animal cells have mitochondria; only plant cells have chloroplasts.