Page 14 - Cell biology PDG 2024

5) Cytoskeleton

The cytoskeleton is a complex network of interlinking protein filaments
present in the cytoplasm of all cells. It extends from the cell nucleus to
the cell membrane. In eukaryotes, it is composed of microfilaments,
intermediate filaments and microtubules, and these are all capable of
rapid growth or disassembly dependent on the cell's requirements

Function of cytoskeleton:
 Gives the cell its shape and mechanical resistance to deformation
 Stabilizes the tissue through association with extracellular
connective tissue and other cells
 The cytoskeleton has the ability to contract thus helping in the
deformation of the cell and the cell's environment and allowing
cells to migrate
 It is involved in many cell signaling pathways and endocytosis
 Helps the segregation of chromosomes during cellular division
 It can form specialized structures, such as flagella

The structure and function of the cytoskeleton can be very different,
depending on organism and cell type

6) Organelles:

A) Nucleus
 Known as the cell’s “command center,”
 The nucleus is a membrane-bound organelle that contains genetic
or the hereditary material (DNA) of eukaryotic organisms.
 It's the largest organelle inside the cell taking up about a tenth of
the entire cell volume.
 Main components of a nucleus include:

Phospholipid bilayer membrane, Nucleoplasm, Nucleolus, Chromatin

Note that some eukaryotic cells lack a nucleus and are referred to as
enucleate cells (e.g. erythrocytes)
 Nucleolus: considered as the brain of the nucleus. It represents

around 25% of the volume of the nucleus. It is mainly involved in

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