Cell Organelles

Cell Organelles

Nucleus

• The nucleus contains the organisms hereditary material and controls the cells activities. It's usually between 10 and 20µ 
• It's surrounded by a double membrane called the nuclear envelope and the nuclear envelope is continuous with the endoplasmic reticulum. The nuclear envelope controls the entry and exit of materials in and out of the nucleus.
• The nuclear envelope is interdispersed by pores that allow large molecules such as mRNA to leave the nucleus
• Most of the nucleus is made up of a granular material called nucleoplasm
• When the chromosomes are unwound as they usually are unless the cells dividing, they're referred to as chromatin
• Within the nucleus is a dark-staining area called the nucleolus which manufactures ribosomal RNA and assembles ribosomes
• The nucleus acts as the cells control centre through the production of mRNA and the nucleus is a store of genetic material. It's responsible for manufacturing rRNA and ribosomes.

Mitochondria

• Mitochondria is a double-membraned structure. It's inner membrane is highly infolded to create fingers called cristae.
• The inner space is refererd to as the matrix.
• Cristae increase the surface area available for the attachment of enzymes involved in respiration.
• The matrix contains protein, lipids and traces of DNA that allow mitochondria to produce their own proteins.
• Mitochondria perform respiration and are found in high concentrations in cells that have a high level of metabolic activity such as muscle cells
• Mitchondria are responsible for the production of ATP, which is the energy currency of living organisms

Endoplasmic Reticulum

• This spreads throughout the whole of the cytoplasm
• It's a 3D network of cavities - some small and sac-like, others long and tubular and all are surrounded by a membrane
• The endoplasmic reticulum links with the nuclear membrane and makes up a large part of the transport system within a cell as well as being the site of synthseis for many important chemicals
• The amount and type of endoplasmic reticulum in a cell gives an indication as to the job that the cell does within the body

Rough Endoplasmic Reticulum

• Rough Endoplasmic Reticulum is studded on its outside membrane with ribosomes. The ribosomes make proteins by translating small pieces of mRNA.
• The rough E.R then isolates and transports these proteins once they have been made.
• Some proteins such as digestive enzymes and hormones aren't used inside the cell that makes htem so they have to be secreted, which means moving them out of the cell without interfering with the cells activities, this is an example of exocytosis
• Many other proteins are needed within the cell.
• The rough endoplasmic reticulum has a large surface area for the synthesis of all of these proteins, and once made the rough endoplasmic reticulum stores or transports these proteins both within the cell and from inside to the outside of the cell
• Cells that secrete materials such…