Euchromatin is “light” chromatin that represents DNA that is currently active for transcription. The fact that it is “light” implies that it is relatively decondensed and accessible by polymerases. Euchromatin is generally present during interphase, when most transcription and replication takes place, and is converted to heterochromatin during mitosis.

Translation occurs outside of the nucleus and uses mRNA as a template, not DNA.

The smooth endoplasmic reticulum contains enzymes responsible for the metabolism of small chemical molecules such as alcohol, pharmaceutical drugs, and environmental contaminants. Expansion of the smooth endoplasmic reticulum can occur under conditions of new and continued exposure to a given chemical or stimulus as an adaptation to metabolize and eliminate the drug or chemical.

Smooth endoplasmic reticulum is particularly abundant in hepatocytes, or liver cells. Blood absorbs nutrients and ingested toxins from the small intestine and immediately travels to the liver through the portal vein. Hepatocytes then filter and metabolize the absorbed toxins before they can circulate through the body.

Mitochondria and chloroplasts are organelles within eukaryotic and plant cells, respectively. All eukaryotic organisms contain mitochondria, but only photoautotrophs will contain chloroplasts. The function of these organelles is to produce energy for the cell to survive and function. Mitochondria produce energy through respiration and chloroplasts produce energy through photosynthesis. These organelles have their own DNA to express their own set of genes and have ribosomes to make the proteins necessary to make energy for the cell. The proteins for the electron transport chain, for example, are transcribed and translated within the mitochondrial matrix before being implanted in the inner mitochondrial membrane.

The Golgi apparatus is derived from the endoplasmic reticulum and consists of a series of flattened sacs. The function of the Golgi apparatus is to package and transport proteins to the cell surface within vesicles, which pinch off from the Golgi. These vesicles then interface with the cell membrane, releasing their contents into the extracellular space or integrating membrane proteins into the cell membrane.

The Golgi apparatus is not involved in differentiation between the smooth and rough endoplasmic reticulum. This difference comes from the presence of ribosomes, which are embedded in the surface of the rough endoplasmic reticulum, but absent from the smooth endoplasmic reticulum. The rough endoplasmic reticulum is responsible for synthesizing and modifying proteins that are destined for the Golgi apparatus for packaging. The smooth endoplasmic reticulum helps eliminate toxins from the cell.

The dense, rigid exterior is most likely describing a cell wall. Cell walls are used to protect cells and help them maintain their shape. Plant cells, fungal cells, and most prokaryotic cells have a cell wall structure, though the composition of the cell walls varies between cell types. Plants, such as ferns, use cellulose in their cell walls. Fungi, such as mushrooms, generally use chitin. Prokaryotic cell walls vary in composition, but bacteria generally use peptidoglycan, which can help in identifying bacteria via Gram staining.

Animal cells, such as those found in the liver, do not have cell walls.

The Golgi apparatus is where transport vesicles are developed and is known as the transport and processing center. Proteins and other compounds are taken to the Golgi apparatus. The Golgi has several membrane-bound sacs that allow proteins to become engulfed in vesicles or integrated into the membranes of vesicles. Complete vesicles are then transported within the cell or to the cell membrane, where they fuse and release their contents into the extracellular space. The membrane of the vesicles is incorporated into the cell membrane, along with any integrated proteins.

Lysosomes are processed in the Golgi apparatus and contain enzymes that are activated by low pH to get rid of waste and damaged organelles. The smooth endoplasmic reticulum is responsible for absorbing and removing drugs and poisons. The rough endoplasmic reticulum manufactures and modifies proteins before they are packaged in the Golgi apparatus. Ribosomes function in translation, producing proteins from mRNA.

The endomembrane system is responsible for the compartmentalization of the cell and the delivery of components to different regions of the cell. The nuclear envelope is used to partition the DNA from the cytosol. The Golgi apparatus and rough endoplasmic reticulum are used to synthesize and package proteins for vesicle transport. The smooth endoplasmic reticulum synthesizes lipids to be used in membrane structures.

Mitochondria are membrane-bound, but do not donate their membrane to the formation of cellular vesicles. They are primarily involved in energy production.

The nucleolus is a structure found inside the nucleus. It is responsible for the production of rRNA, and also constructs the subunits of ribosomes.

Mitochondria are responsible for ATP production, and various chaperone proteins are responsible for directing substance transport within a cell. Several classes of proteins in the nucleus are involved in mRNA transcription and post-transcription modification, but these processes do not involve the nucleolus.

The rough endoplasmic reticulum is given its name due to the ribosomes present within its membrane. These ribosomes are able to translate proteins, which are then modified within the endoplasmic reticulum and sent to the Golgi apparatus.

Ribosomes are the only cellular machinery capable of translating RNA into proteins.

The endoplasmic reticulum is an organelle that manufactures proteins, steroid molecules, cholesterol, and other lipids. The rough endoplasmic reticulum is embedded with ribosomes to allow polypeptides to be translated into the interior of the organelle. The smooth endoplasmic reticulum is responsible for lipid synthesis and degradation of toxins.