26/10/2013 · Hint 2
The cytoplasm is the internal region of the cell bounded by the plasma membrane, excluding the interior of the nucleus and the interior regions of organelles and the endomembrane system. The cytoplasm contains ribosomes, tRNAs and mRNAs for protein synthesis, the cytoskeleton, many metabolic enzymes, and proteins that function in cell signaling. The cytoplasm is so crowded with macromolecules that it has the consistency of a hydrated gel; much of the water molecules are associated with other molecules.
Biology - The Endomembrane System and Proteins
The system is defined more accurately as the set ofmembranes that form a single functional and developmental unit,either being connected together directly, or exchanging materialthrough .Importantly, the endomembrane system does not include the membranesof or .The nuclear envelope is a membrane containing two layers, thatencompasses the contents of the nucleus.The endoplasmic reticulum (ER) is a synthesis and transportorganelle that branches into the cytoplasm in plant and animalcells.The Golgi apparatus is a series of multiple compartments wheremolecules are packaged for delivery to other cell components or forsecretion from the cell.Vacuoles, which are found in both plant and animal cells (thoughmuch bigger in plant cells), are responsible for maintaining theshape and structure of the cell as well as storing wasteproducts.A vesicle is a relatively small, membrane-enclosed sac that storesor transports substances.The plasma membrane, also referred to as the cell membrane, is aprotective barrier that regulates what enters and leaves thecell.There is also an organelle known as the that is only found in fungi, and is connected with hyphal tipgrowth.In endomembranes are rare, although in many photosynthetic bacteriathe plasma membrane is highly folded and most of the cell cytoplasmis filled with layers of light-gathering membrane.These light-gathering membranes may even form enclosed structurescalled in.The organelles of the endomembrane system are related throughdirect contact or by the transfer of membrane segments as vesicles.
The internal environment of a living cell is made up of a fluid, jelly-like substance called cytosol, which consists mainly of water, but also contains various dissolved nutrients and other molecules. The cell contains an array of cellular organelles, each one performing a unique function and helping to maintain the health and activity of the cell. The cytosol and organelles together compose the cell’s cytoplasm. Most organelles are surrounded by a lipid membrane similar to the cell membrane of the cell. The endoplasmic reticulum (ER), Golgi apparatus, and lysosomes share a functional connectivity and are collectively referred to as the endomembrane system. There are two types of ER: smooth and rough. While the smooth ER performs many functions, including lipid synthesis and ion storage, the rough ER is mainly responsible for protein synthesis using its associated ribosomes. The rough ER sends newly made proteins to the Golgi apparatus where they are modified and packaged for delivery to various locations within or outside of the cell. Some of these protein products are enzymes destined to break down unwanted material and are packaged as lysosomes for use inside the cell.