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Summary

• Cells are the basic units of complex organisms.
• The human body is composed of “organs + skeleton”, while the cell is composed of “organelles + cytoskeleton”.
• The cell organelles are classified to membranous and non-membranous organelles.

The plasmalemma:

• consists of a phospholipid bilayer + proteins + carbohydrates (glycolipids or glycoproteins).
• The plasmalemma protects the structural integrity, facilitates movements, and regulates cell-cell interactions, signal transduction, performs phagocytosis, pinocytosis, and exocytosis.

Mitochondria

• are self-replicating (by fission) membranous organelles.
• has outer smooth and an inner irregular folded membrane.
• They release ATP (energy) and usually found where metabolic activity is high.

Ribosomes

• are small particles. About 12 nm wide and 25 nm long
• their function is proteins synthesis.

Endoplasmic reticulum

is a membranous network and may be rough (rER) or smooth (sER).

The rER 

• is covered with ribosomes.
• is responsible for synthesis of proteins.

The sER 

• has no ribosomes.
• Synthesize steroid hormones & phospholipids.
• Oxidation, conjugation, and methylation processes

The Golgi Apparatus

•  is membranous organelle.
• Composed of series of multiple curved cisternae.
• It has a immature convex surface + a mature concave face.