Cytoplasm and cytosol

• Protoplasm à cytoplasm + nucleus
• Cytosol à content of cell excluding nucleus and another membrane-bound nucleus.
• A cytoskeleton à a network of intercellular fibers that gives the cell its shape and structural rigidity.
• Cytoskeleton has 3 structures namely microtubule, microfibril, and intermediate filament.

a) Microtubule:

• Largest filament, 25nm in diameter.
• Composed of protein tubulin.
• Involved in maintaining cell shape, and movement of chromosomes, cilia, and flagella.

b) Microfilament:

• 6 nm in diameter.
• Composed of actin protein ( for muscle contraction).
• Involved in cell division, endocytosis, exocytosis, and cell locomotion.

c) Intermediate filament:

• 10-15 nm in diameter.
• Composed of different types of proteins in different cells.
• Gives mechanical strength and stability.