Biology -Unit 2 Topic 3

Some single-celled organisms and all multicellular organisms such as humans are made up of eukaryotic cells. A eukaryotic cell always contains:

A nucleus, containing genetic material surrounded by a double envelope.

Organelles (structures) in the cytoplasm, each surrounded by one or two membranes.

Animal Cell Ultrastructure.

ultrastructure is the name for the fine structure that is revealed when using a powerful microscope such as an electron microscope.

Here are some of its organelles:

Nucleus - surrounded by a double membrane (envelope). There are pores in this nuclear envelope. There is a dark staining area , called the nucleolus within the nuclear envelope.

Centrioles - Two hollow cylinders, arranged at right angles to each other.

Lysosome - Enclosed by a single membrane and contains digestive enzymes.

Golgi apparatus - Series of single, curved sacs enclosed by a membrane. Each sac is smaller than the previous one. Many vesicles cluster around the golgi apparatus.

Mitochondria - Surrounded by a double membrane (envelope). Inner membrane folded into finger like projections , these are called cristae. Central area contains contains a jelly called the matrix. floating in the matrix are :

ribosomes.

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