The Nucleus and Endoplasmic Reticulum
The nucleus
* The largest cell organelle * The nucleus houses nearly all the cell’s genetic material * It has the instructions for making proteins Part of the nucleus | function | Chromatin | * The chromatin consists of DNA and proteins. * Some of these proteins controls the activities of the cell * When cells divide, chromatin condenses into visible chromosomes * The chromatin shows up as dark patches when it is stained. | Nucleolus | * The nucleolus makes RNA and ribosomes-these pass into the cytoplasm and proteins are assembled on them (protein synthesis) * The nucleus is a dense, spherical structure inside the nucleus * In some cells there may be two nucleus’s | Nuclear envelope | * This is a structure made of two membranes, the inner nuclear envelope and the outer nuclear envelope. * There is a fluid between the two membranes | Nuclear pore | * A lot of hole pass right through the nuclear envelope these are known as the nuclear pores * These holes are large enough for relatively large molecules to pass through such as hormones, ribosomes and mRNA | Nucleoplasm | * The cytoplasm-like material within the nucleus * It is enveloped by the nuclear envelope * Substances like enzymes are dissolved in it |
Endoplasmic reticulum * The cytoplasm is a highly organised material consisting of a soluble ground substance called the cytosol * It contains an elaborate system of parallel flattened cavities lined with a thin membrane these are called cisternae * The cavities are interconnected and the membrane is continuous with the nuclear membrane Smooth endoplasmic reticulum | Rough endoplasmic reticulum | * An extensive system of membranes running through the cytoplasm. | * Same basic structure as SER with extensive layers of membrane stacks (cisternae) | * Does not contain any ribosomes and so appears smooth | * Has ribosomes studding the surface and thus appears rough
* The largest cell organelle * The nucleus houses nearly all the cell’s genetic material * It has the instructions for making proteins Part of the nucleus | function | Chromatin | * The chromatin consists of DNA and proteins. * Some of these proteins controls the activities of the cell * When cells divide, chromatin condenses into visible chromosomes * The chromatin shows up as dark patches when it is stained. | Nucleolus | * The nucleolus makes RNA and ribosomes-these pass into the cytoplasm and proteins are assembled on them (protein synthesis) * The nucleus is a dense, spherical structure inside the nucleus * In some cells there may be two nucleus’s | Nuclear envelope | * This is a structure made of two membranes, the inner nuclear envelope and the outer nuclear envelope. * There is a fluid between the two membranes | Nuclear pore | * A lot of hole pass right through the nuclear envelope these are known as the nuclear pores * These holes are large enough for relatively large molecules to pass through such as hormones, ribosomes and mRNA | Nucleoplasm | * The cytoplasm-like material within the nucleus * It is enveloped by the nuclear envelope * Substances like enzymes are dissolved in it |
Endoplasmic reticulum * The cytoplasm is a highly organised material consisting of a soluble ground substance called the cytosol * It contains an elaborate system of parallel flattened cavities lined with a thin membrane these are called cisternae * The cavities are interconnected and the membrane is continuous with the nuclear membrane Smooth endoplasmic reticulum | Rough endoplasmic reticulum | * An extensive system of membranes running through the cytoplasm. | * Same basic structure as SER with extensive layers of membrane stacks (cisternae) | * Does not contain any ribosomes and so appears smooth | * Has ribosomes studding the surface and thus appears rough