Basic Bio, I will rate you. 1-With an understanding of the central dogma of life
ID: 87671 • Letter: B
Question
Basic Bio, I will rate you.
1-With an understanding of the central dogma of life, can you explain how elucidating the sequence of the protein insulin allowed scientists to ultimately clone the human insulin gene?
2-Are ribosomes membranous or nonmembranous organelles? What is the difference between fixed and free ribosomes? What are the structural and functional differences between smooth and rough endoplasmic reticulum?
3-What is the function of the Golgi apparatus? Are all proteins that leave the Golgi destined to leave the cell? If not, what are all of the potential fates of proteins that leave Golgi?
4-What is the difference between a primary lysosome and a secondary lysosome? What is difference in hydrogen ion concentration between a lysosome and the cytosol of the cell?
5-Peroxisomes produce antioxidants? Where are the oxidants generated that these antioxidants combat? Why are oxidants (or free radicals) so dangerous to the human body? What is a good example a vital function of free radicals in the body?
6-Can you explain how the mitochondria in your cells were once free-living bacteria? What are the lines of evidence that support the endosymbiotic theory
Explanation / Answer
Answer 1 ) Elucidation of the DNA sequence of insulin gene allows to chemically synthesize two artificial mini-genes (chain A and chain B of insulin). These mini-genes are inserted into plasmids and can be transferred into two separate bacterial hosts (E.coli). The bacterial cell produces two chains of human insulin. The transgenic bacteria are cloned so that they make multiple copies of the two chains. After the two chains have been produced separately, the cultures can be mixed and a chemical treatment can be employed to generate the dilsulphide bonds linking the two chains.
Answer 2) Ribosomes are non-membranous organelles. These are granule like structures either occurring freely in cytoplasm (free ribosomes) or attached (fixed ribosomes) to the endoplasmic reticulum (rough endoplasmic reticulum). Proteins that are manufactured by fixed ribosomes enter the endoplasmic reticulum where they are modified and packaged for secretion. Fixed ribosomes also translate proteins that move out of the cell. Free ribosomes play a role in translating mRNA for proteins that stay in the cytosol.
Rough endoplasmic reticulum, have ribosomes on the surface and is present attached to the nuclear membrane. It is mainly involved in synthesizing proteins that are supposed to be transported outside the cell. Smooth endoplasmic reticulum does not contain ribosomes, it helps in storage of proteins and lipids.
Answer 3) The function of Golgi apparatus is to process proteins (removal of sugars from proteins known as glycosylation, addition of sulphate groups known as sulphation, addition of phosphate groups known as phosphorylation) made by the endoplasmic reticulum before transporting them to their final destination – lysosomes, plasma membrane or package for secretion. Some modifications act as signals for proteins to reach destinations within the cell.
Answer 4) Lysosomes are membrane bound organelles found in cytoplasm of eukarotic cells that contain digestive enzymes (acid hydrolases). These are also known as suicide bags since they play a role in autolysis. Primary lysosomes are sac like structures containing enzymes synthesized by ribosomes. Secondary lysosomes are formed by fusion of primary lysosomes with phagosomes. The hydrogen ion concentration (pH) inside the lysosome is 4.8 while the cytosol has a slightly alkaline pH of 7.2. The lysosome maintains this pH by pumping hydrogen ions from the cytosol across lysosomal membrane via proton pumps and chloride ion channels.
Answer 5) Peroxisomes are single, membrane bound organelles. The main functions include breakdown of poor substrates for mitochondrial beta oxidation, such as very long chain fatty acids, polyunsaturated fatty acids and branched chain fatty acids. Free radicals are generated during production of ATP in mitochondria. These are harmful as they damage the vital organic molecules. However they are also beneficial as the play a critical role in stimulation of phagocytosis, initiation of drug detoxification process and initiation of signal transduction process.
Answer 6) It has been hypothesized that mitochondria were free living organisms since there are many similarities between prokaryotes and mitochondria. They are considered to have originated from proteobacteria (Rickettsiales) through endosymbiosis. The following evidences support the endosymbiotic theory :