Quiz 2 Flashcards
Vesicles
Vesicles store, transport, or digest cellular products and waste. The membrane enclosing the vesicle is similar to that of the plasma membrane, and vesicles can fuse with the plasma membrane to release their contents outside of the cell. Vesicles can also fuse with other organelles within the cell. A vesicle can be visualised as a bubble of liquid within another liquid, a supramolecular assembly made up of many different molecules. More technically, a vesicle is a small membrane-enclosed sack that can store or transport substances. Vesicles can form naturally because of the properties of lipid membranes (see micelle), or they may be prepared. Artificially prepared vesicles are known as liposomes. Most vesicles have specialized functions depending on what materials they contain.
Endomembrane system
The endomembrane system is composed of the different membranes that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryotes the organelles of the endomembrane system include: the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vacuoles, vesicles, and the cell membrane. The system is defined more accurately as the set of membranes that form a single functional and developmental unit, either being connected together directly, or exchanging material through vesicle transport.
Rough ER
The rough endoplasmic reticulum manufactures membranes and secretory
proteins
. In certain
leukocytes
(white blood cells), the rough ER produces
antibodies
. In pancreatic cells, the rough ER produces insulin. The rough and smooth ER are usually interconnected and the proteins and membranes made by the rough ER move into the smooth ER to be transferred to other locations.
Smooth ER
The smooth ER has a wide range of functions including
carbohydrate
and
lipid
synthesis. It serves as a transitional area for vesicles that transport ER products to various destinations. In liver cells the smooth ER produces enzymes that help to detoxify certain compounds. In
muscles
the smooth ER assists in the contraction of muscle cells, and in
brain
cells it synthesizes male and female hormones.
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. Secreted extracellular proteins are often glycosylated. In proteins that have segments extending extracellularly, the extracellular segments are also glycosylated. Glycoproteins are often important integral membrane proteins, where they play a role in cell–cell interactions. Glycoproteins are also formed in the cytosol, but their functions and the pathways producing these modifications in this compartment are less well understood.[2
Transport vesicles
Transport vesicles can move molecules between locations inside the cell, e.g., proteins from the rough endoplasmic reticulum to the Golgi apparatus.
Membrane-bound and secreted proteins are made on ribosomes found in the rough endoplasmic reticulum. Most of these proteins mature in the Golgi apparatus before going to their final destination which may be to lysosomes, peroxisomes, or outside of the cell. These proteins travel within the cell inside of transport vesicles.
Golgi apparatus
The Golgi apparatus or Golgi complex is found in most cells. It is another packaging organelle like the endoplasmic reticulum (ER). The Golgi apparatus gathers simple molecules and combines them to make molecules that are more complex. It then takes those big molecules, packages them in vesicles, and either stores them for later use or sends them out of the cell. It is also the organelle that builds lysosomes (cell digestion machines). Golgi complexes in the plant may also create complex sugars and send them off in secretory vesicles. The vesicles are created in the same way the ER does it. The vesicles are pinched off the membranes and float through the cell.
Cis face
The cis face of a Golgi stack is the end of the organelle where substances enter from the endoplasmic reticulum for processing,
Trans face
while the trans face is where they exit in the form of smaller detached vesicles. Consequently, the cis face is found near the endoplasmic reticulum, from whence most of the material it receives comes, and the trans face is positioned near the plasma membrane of the cell, to where many of the substances it modifies are shipped. The chemical make-up of each face is different and the enzymes contained in the lumens (inner open spaces) of the cisternae between the faces are distinctive.
Lysosome
Lysosomes - Little Enzyme Packages
Simple Structure of a lysosome You will find organelles called lysosomes in nearly every animal-like eukaryotic cell. Lysosomes hold enzymes that were created by the cell. The purpose of the lysosome is to digest things. They might be used to digest food or break down the cell when it dies. lysosome is basically a specialized vesicle that holds a variety of enzymes. The enzyme proteins are first created in the rough endoplasmic reticulum. Those proteins are packaged in a vesicle and sent to the Golgi apparatus. The Golgi then does its final work to create the digestive enzymes and pinches off a small, very specific vesicle. That vesicle is a lysosome. From there the lysosomes float in the cytoplasm until they are needed. Lysosomes are single-membrane organelles. Since lysosomes are little digestion machines, they go to work when the cell absorbs or eats some food. Once the material is inside the cell, the lysosomes attach and release their enzymes. The enzymes break down complex molecules that can include complex sugars and proteins. But what if food is scarce and the cell is starving? The lysosomes go to work even if there is no food for the cell. When the signal is sent out, lysosomes will actually digest the cell organelles for nutrients.
Phagocytosis
Phagocytosis is a cell taking in a large object that it will eventually digest. The classic example is an amoeba eating a bacterium. First, the cell senses the bacterium because of chemicals in the environment. The cell then moves towards the prey. Once contact is made, the amoeba slowly wraps its cell membrane around the object. When the membranes reach out for the prey, they are called pseudopodium. When the cell membrane surrounds the object, the object has actually been sealed in a new vesicle.
The final step is digestion of the prey. If a cell does not act quickly, the bacterium could begin to reproduce. Lysosomes quickly attach to the vesicle of food and release digestive enzymes. The enzyme action is called an oxidative burst. The food is then broken down and the amoeba absorbs the nutrients. Waste particles remain in the vesicle and can then be sent out of the cell.
Food vacuoles
a membrane-enclosed cell vacuole with a digestive function, containing material taken up in by the process of phagocytosis.The food vacuole, or digestive vacuole, is an organelle found in parasites that cause malaria. During the stage of the parasites’ lifecycle where it resides within a human (or other mammalian) red blood cell, it is the site of haemoglobin digestion and the formation of the large haemozoin crystals that can be seen under a light microscope.[1]
Contractile vacuole
A membrane-bound organelle found in certain protists that pumps fluid in a cyclical manner from within the cell to the outside by alternately filling and then contracting to release its contents at various points on the surface of the cell. It functions in maintaining osmotic equilibrium.
Central vacuole
f you’ve ever looked at a diagram of a plant cell, you probably noticed one organelle that stands out and is larger than all of the others. This organelle is known as the central vacuole. The central vacuole is a membrane-bound organelle containing water and other enzymes that function during the life of the plant. Structurally, the central vacuole is surrounded by a phospholipid bilayer.
Central vacuole
f you’ve ever looked at a diagram of a plant cell, you probably noticed one organelle that stands out and is larger than all of the others. This organelle is known as the central vacuole. The central vacuole is a membrane-bound organelle containing water and other enzymes that function during the life of the plant. Structurally, the central vacuole is surrounded by a phospholipid bilayer.
