Lecture on Organelles and Compartmentalization

Mitochondria

• Structure
  • Has two membranes: outer and inner.
  • Inner membrane is highly folded into structures called cristae.
  • Folds increase surface area for more ATP production.
  • Compartments
    • Matrix: Inside the inner membrane, site for link reaction and Krebs cycle.
    • Intermembrane space: Space between inner and outer membranes, crucial for establishing proton gradient for ATP production.
• Function
  • Cristae increase surface area for electron transport chain and ATP production.
  • Matrix concentrates enzymes for metabolic processes.
  • Intermembrane space aids rapid development of a proton concentration gradient.

Chloroplast

• Structure
  • Double membrane, with outer and inner membranes close together forming the chloroplast envelope.
  • Contains chlorophyll in thylakoids for light absorption.
  • Thylakoids are disk-like structures, stacked into grana.
  • Stroma: fluid-filled space surrounding grana.
• Function
  • Thylakoids store chlorophyll for light absorption leading to photosynthesis.
  • Small space in thylakoids helps in ATP production due to proton gradient.
  • Stroma contains enzymes for the Calvin cycle.

Nucleus

• Structure
  • Double membrane with large pores made by integral proteins.
  • Contains nucleolus, site of ribosome production.
• Function
  • Pores allow transport of large molecules like mRNA out of the nucleus.
  • Double membrane structure is easily dissolved and reformed during mitosis.

Ribosomes

• Location
  • Found free-floating in the cytoplasm or attached to the rough ER.
• Function
  • Cytoplasmic ribosomes synthesize proteins for internal cell use.
  • Rough ER ribosomes synthesize proteins for secretion outside the cell.

Golgi Apparatus

• Structure
  • Composed of a network of flattened sacs with vesicles.
• Function
  • Receives and modifies proteins from the ER.
  • Repackages proteins into vesicles for secretion via exocytosis.

Vesicles

• Role
  • Formed during endocytosis and exocytosis.
  • Transport molecules within cells, such as between rough ER and Golgi.
  • Contribute to cell growth by fusing with cell membrane.

Key Concept: Form and Function

• Each organelle's structure (form) aids its specific function in the cell.
• Understanding these helps in grasping cellular processes and efficiency.