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Biology Exam Revision : Cell Membrane

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Biology Exam Revision
Cells
Cell Membrane The cell membrane surrounds the cytoplasm of a cell, separating its contents from the environment around it. The cell surface membrane consists of two layers of phospholipids and regulates what can enter and leave the cell. It is a semi-permeable membrane embedded with proteins, including receptors on the outer surface.

Nucleus The nucleus is the ‘brain’ of the cell. It is a large, round organelle and is surrounded by the nuclear envelope (a double membrane). The nuclear envelope allows the exchange of materials between the nucleus and cytoplasm through its large, nuclear pores. The nucleus contains DNA therefore the information to regulate the metabolism and reproduction for the cell. It also contains a dark staining area called the nucleolus. The nucleolus produces ribosomes.

Mitochondrion The mitochondrion has a double membrane surrounding its ellipse shape. Some of the reactions of aerobic respiration (the process living things go through to use food energy) occur in the mitochondrion and they are the ‘powerhouses’ of the cell. They produce energy in the form of ATP.

Ribosomes Ribosomes are the site of protein synthesis and are made up of two subunits. One of these units is large, and the other is small. These subunits consist of protein and ribosomal RNA. Ribosomes can be found floating free in a cell, or attached to the endoplasmic reticulum.

Rough Endoplasmic Reticulum The rough endoplasmic reticulum is covered with
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