Notes on Cell Organelles and Their Functions

Overview of Cell Structure

• Three Major Parts of a Cell:
  • Plasma membrane
  • Organelles
  • Cytoplasm
  • Nucleus

Cytoplasm and Cytosol

• Cytoplasm:
  • The fluid and non-living components within the cell.
  • Contains water, proteins, molecules, and ions.

Nucleus

• Control Center of the Cell:
  • Contains DNA (the genetic material).
  • DNA is crucial for protein synthesis.
  • Nucleolus:
    • Dark inner portion responsible for making ribosomal RNA (rRNA).
  • Nuclear Envelope:
    • Inner and outer membranes surrounding the nucleus.
  • Nuclear Pores:
    • Allow substances like messenger RNA (mRNA) to exit the nucleus.

Endoplasmic Reticulum (ER)

• Types:
  • Rough Endoplasmic Reticulum (RER):
    • Studded with ribosomes (protein synthesis sites).
    • Main job: Produce proteins for export.
  • Smooth Endoplasmic Reticulum (SER):
    • No ribosomes; involved in various metabolic processes.
    • In liver cells: detoxifies drugs and alcohol.
    • In muscle cells: stores calcium ions necessary for muscle contraction.

Golgi Apparatus (Golgi Complex)

• Function:
  • Modifies, sorts, and packages proteins received from the RER.
  • Proteins can be exported outside the cell or incorporated into the plasma membrane.

Ribosomes

• Sites of Protein Synthesis:
  • Found on rough ER or free in cytoplasm.
  • Ribosomes on RER produce proteins for export; free ribosomes produce proteins for internal use.

Mitochondria

• Powerhouse of the Cell:
  • Generates ATP through aerobic respiration.
  • Cells with high energy demands (e.g., muscle, neurons) contain more mitochondria.
  • Contains its own DNA (mitochondrial DNA).

Lysosomes and Peroxisomes

• Lysosomes:
  • Contains digestive enzymes to break down organic materials and worn-out organelles.
  • Involved in autophagy (self-digestion) and apoptosis (programmed cell death).
• Peroxisomes:
  • Break down inorganic materials using peroxides (e.g., hydrogen peroxide).

Cytoskeleton

• Framework of the Cell:
  • Composed of structural proteins (microtubules, actin, etc.).
  • Provides shape and support to the cell.
  • Involved in mitosis through spindle fibers.

Summary

• Main Functions of a Cell:
  • Synthesize proteins based on the genetic code from DNA.
  • Utilize mitochondria to generate energy (ATP) for cellular processes.
  • Organelles work together like an assembly line to support cell functions.