Structure of an Epithelial cell.

Structure of an Epithelial Cell:
Nucleus: The function of a nucleus is to act as the control centre of the cell, by producing mRNA, and therefore, protein synthesis. Also, to produce ribosomal RNA and ribosomes, and retain the cell’s genetic material in the form of DNA and chromosomes.
Its structure aids this, as it has the nuclear envelope, which is a double membrane, where all the reaction take place in the nucleus, it controls what goes in and out of the nucleus, and it connected with the endoplasmic reticulum, and has ribosomes on it. It has nuclear pores, to allow large molecules out, such as messenger RNA. It has nucleoplasm, the material that makes up the bulk of it, jelly like. It contains Chromatin (the nucleoplasm) which contains DNA, as it is the diffuse form that chromosomes take when the cell is not dividing. The nucleolus is a spherical body within the nucleoplasm which makes ribosomal RNA and ribosomes.
Mitochondrion: Function is to produce ATP for respiration from carbohydrates. The structure applies to this function as it has a double membrane, the outer controls what goes in and out, and the inner is folded to from Cristae, which increase the surface area, so more can be taken in, and provide a large surface area for the attachment of enzymes. The enzymes involved in respiration are found in the matrix of the mitochondria, and this is where they produce their own proteins (control it).
Endoplasmic Reticulum: Function of the rough one is to provide a large surface area for the synthesis of proteins and glycoproteins, and to provide a pathway for the transport of materials through the cell. The smooth one store and transport lipids, and store and transport carbohydrates.
It spreads through the cytoplasm of the cell and is continuous with the nuclear membrane. Large sheet like membranes = large surface areas for storage. Often have larger ER’s in cells like secretory cells which contain and store large amounts of carbohydrates, proteins, and lipids.
Golgi Apparatus: Add carbohydrates to proteins to form glycoproteins. They produce secretory enzymes, such as those secreted by the pancreas (pancreatic amylase,) to secrete carbohydrates, to transport, modify, and store lipids, and to form Lysosomes. The structure relates to this because: It’s made up of stacks of flattened sacs, or cisternae, with small rounded structures called vesicles. Proteins and lipids produced by the endoplasmic reticulum pass through in a sequence, and the golgi modifies them, then ‘labels’ them, so they can be accurately sorted and sent to the right places. Once sorted, they are put into vesicles and transported the vesicles can move to the cell surface where they can release their contents to the outside.
Lysosomes form when the vesicles of the Golgi apparatus contain enzymes like lipase and protease. Up to 50 enzymes can be in a lysosome. They isolate them and either releases them outside, or in a phagocytic vessel. They break down cells after they die, break down worn out organelles release enzymes to the outside of the cell to destroy material around it, and break down materials ingested by phagocytic cells.
Microvilli: finger like projections that increase surface area.
You can relate the cell ultra structure to the function by indications such as how many of a certain organelle it contain, like if there is a lot of mitochondria, as they produce ATP, it would be thought that, needing a lot of it, that cell has a high metabolic rate.
1) Ribosomes are important in protein synthesis.
2) Three carbohydrates absorbed by the epithelial cell of the small intestine are Glucose, Galactose, and Fructose.
3) A) It posses structures called Cristae = Mitochondria. B) It contains chromatin = nucleus. C) Rough Endoplasmic Reticulum. D) It digests worn out organelles = Lysosome.
4) A sperm cell would have a well developed nucleus, as, to fertilise, it give DNA in the form of chromosomes, which is in chromatin in the nucleus, so this would have to be developed. Also, it would need mitochondria, as it moves using a flagellum, and the beating of this pushes it forward, but it would need an energy source, which mitochondria have, in the form of ATP, so it would have a lot of these, as it is almost in constant motion.
5) It would have a developed golgi apparatus, as these are what produce Lysosomes, and it needs lots of Lysosomes, as Lysosomes break down the material that phagocytic cells such as white blood cells, ingest.
6) Liver cells that manufacture proteins and lipids at a rapid rate would need a developed endoplasmic reticulum, as the rough deals with synthesising proteins, and the smooth synthesises lipids, and it would also need a developed Golgi Apparatus, as the golgi apparatus stores, modifies and transports proteins and lipids.