Question

Define Golgi apparatus, mitochondria, nucleus,endoplasmic reticulum, plastics,ribosomes

Answer 1

Golgi Apparatus:

The Golgi apparatus or Golgi complex is found in the Cytoplasm. It is a flattened, layered sac-like organelle that takes proteins and carbohydrates and modifies and packages them. The Golgi apparatus is a system of membranes working close with the endoplasmic reticulum it modifies the proteins and carbohydrates.

The Golgi Apparatus or Golgi Complex basically functions as a "packaging center" for the cell, attaching "address labels" (functional groups) to various cell products to direct them to their respective locations, and "packaging" the products into vacuoles to ensure delivery. Anatomically, the Golgi Complex consists of layers of lipid membrane stacked one one top of another, with a cis face and a trans face. As the molecular product being packaged moves through the complex, various enzymes act upon it to induce vacuole formation and functional group attachment.


Mitochondria:

Mitochondria are organelles that are scattered throughout the cell, all cells have mitochondria. This is where chemical reactions occur that transfer energy from organic compounds to ATP. ATP controls most of the reactions that occur inside of the cell. Mitochondria is surrounded by two membranes. Mitochondria have their very own DNA, and new mitochondria are born when existing ones grow and divide.

It is responsible for a cell's metabolism. It synthetizes ATP through a protein called ATP synthase. Mitochondria have a double membrane. An outer membrane and a folded inner membrane. The internal membrane, called the cristae is invaginated (folded or creased), to maximize surface area enabling it to hold more ATP synthases. It is called as "the powerhouse of the cell" which is present in the eukaryotic organisms. It has matrix inside the inner membrane



Nucleus:

The Nucleus is enclosed in a phospholipid bilayer (Nuclear Envelope) and has pores in the membrane. Inside of the Nucleus it consists of a Nucleolus and Chromosomes (DNA) . The whole nucleus is said to be like a "control center" to the cell and keeps the Chromosomes protected as well.

The nucleus contains genetic material or DNA in the form of chromatin, or, during mitosis or late interphase, chromosomes. All transcription and replication of genetic material takes place within the nucleus, as does RNA processing. The nucleolus also resides within the nucleus, and is responsible for RNA transcription and folding. Translation of RNA transcripts takes place outside of the nucleus.



Endoplasmic Reticulum:

The Endoplasmic Reticulum (ER) acts as a transport from the nucleus and ribosomes to the Golgi apparatus. There are two types of endoplasmic reticulum:

The first is the rough endoplasmic reticulum, or rough ER. The rough ER is covered with ribosomes giving it its rough appearance. The rough ER transports materials throuth the cell and produces proteins in sacks, which are then sent to the Golgi body or into the cell membrane. The rough ER is connected to the Nuclear membrane as well as the smooth ER.

The second type of ER is the Smooth Endoplasmic Reticulum or smooth ER. The smooth ER does not have ribosomes on its surface. It makes up proteins and lipids that get exported by the cell. The smooth ER also controls the level in the muscles and detoxifies poisons, alcohol, and drugs.



Plastids:

Plastids are membrane bound organelles used in storage and food production. These are similar to entire prokaryotic cells - for example, like mitochondria they contain their own DNA and self-replicate. Plastids are found only in the plant cell, not in animalcell. They include:

• Chloroplasts - convert light/food into usable energy. (ATP production)
• Leucoplasts - store starch, proteins and lipids.
• Chromoplasts - contain pigments. (E.g. providing colors to flowers)

Ribosomes:

Ribosomes are responsible for protein synthesis. They are comprised of interacting protein and nucleic acid chains. Broadly, ribosomes are comprised of a large and a small subunit. The small subunit functions to attach to the mRNA strand and hold it in place during translation, while the large subunit holds and manufactures the growing polypeptide chain. The large subunit is further subdivided into the A (aminoacyl), P (peptidyl), and E (exit) binding sites.

Aminoacyl Binding Site The aminoacyl binding site binds a charged tRNA whose anticodon matches the codon in the A site.

Peptidyl Binding Site The peptidyl binding site contains the molecular machinery that transfers the bound polypeptide from the tRNA to the polypeptide chain, and holds the growing chain in place.

Exit Site The exit site is the terminal binding site for tRNA, where discharged tRNA's are released from the translation complex.

Ribosomes are attached to the rough ER and are free floating in the cytoplasm. Ribosomes are very tiny and don't consist of membranes.Ribosomes are in your face, hair, skin, and eyes. Ribosomes job is to help with protein synthesis and to make proteins.