2.2 cell structure

• Most cells are made up of a cell membrane, the outer boundary of the cell that separates it from neighbouring cells and the external environment.
• The cell membrane is made up of a double layer of lipid molecules and associated proteins, determines which substances can enter or exit the cell.
• Cytoplasm includes all the specialised structures suspended within it that carry out particular functions.
• Cytosol is the thick fluid within the cell membrane, made up of 75 - 90% water.
• The cytoskeleton consists of microfilament and microtubules that give the cell its shape.
• Microfilament move materials around the cytoplasm or the whole cell.
• Microtubules are hollow rods that keep organelles in place or move them around the cell.
• The cytoskeleton assists the movement of materials, organelles, or the whole cell.
• A vesicle is a membrane bound sac that transports material into, out of, or within the cell.
• The Golgi body is a flattened, membranous bag stacked on top of each other that modifies proteins that come from ribosomes and packages them in vesicles for secretion from the cell.
• Mitochondria are spherical or elongated structures spread throughout the cytoplasm that release energy for the cell through respiration and provide a large surface area for chemical reactions to occur.
• The nucleus contains the genetic material (mostly dna).
• The nuclear membrane is a double membrane that separates the nucleus from the cytoplasm.
• Nuclear pores are gaps in the nuclear membrane to allow large molecules to pass.
• The nucleolus is mainly composed of rna.
• Nucleoplasm suspends the dna and nucleolus within the nucleus.
• Lysosomes are small spheres that contain enzymes that are able to break down proteins, lipids, nucleic acids and some carbohydrates.
• Centrioles are a pair of cylindrical structures, usually located near the nucleus, involved in the reproduction of the cell.
• The endoplasmic reticulum (er) provides a surface on which chemical reactions can occur and the channels between the paired membranes act as storage or transportation of materials.
• Ribosomes are small and spherical and may be free throughout the cytoplasm but most are attached to membranes.
• Cilia are fine projections that move either the whole cell or substances over the surface of the cell.
• Flagella are fewer, longer projections.
• Inclusions are substances that are not a part of the cell structure but are found in the cytoplasm.
• All these structures of the cell work together to meet the cell's needs and allow it to fulfil its function.