Answer and Explanation:
Ribosomes are the primary structure for protein synthesis. They can be found in the rough endoplasmic reticulum or floating in the cytosol.
Free ribosomes are not attached to any cytoplasmic structure or organelle. They synthesize proteins only for internal cell use. Other ribosomes are attached to the membrane of the endoplasmic reticulum and they are in charge of synthesizing membrane proteins or exportation proteins. Free and attached ribosomes are identical and they can alternate their location. This means that although free ribosomes are floating in the cytosol, eventually, they can get attached to the endoplasmic reticulum membrane.
Synthesis of proteins that are destined to membrane or exportation starts in the cytoplasm with the production of a molecule portion known as a <u>signal aminoacidic sequence</u>. This signal sequence varies between 13 and 36 amino acids, is located in the <u>amino extreme</u> of the synthesizing protein, and when it reaches a certain length, it meets the <u>signal recognizing particle</u>. This particle joins the signal sequence of the protein and leads the synthesizing protein and associated ribosome to a specific region in the Rough endoplasmic reticulum where it continues the protein building. When they reach the membrane of the endoplasmic reticulum, the signal recognizing particle links to a receptor associated with a pore. Meanwhile, the ribosome keeps synthesizing the protein, and the enlarged polypeptidic chain goes forward the reticulum lumen through the pore. While this is happening, another enzyme cuts the signal sequence, an action that requires energy from the ATP hydrolysis. When the new protein synthesis is complete, the polypeptide is released into the reticulum lumen. Here it also happens the protein folding (which is possible by the formation of disulfide bridges of proteins are formed) and the initial stages of glycosylation (the oligosaccharide addition).
Once membrane proteins are folded in the interior of the endoplasmic reticulum, they are packaged into vesicles and sent to the Golgi complex, where it occurs the final association of carbohydrates with proteins. The Golgi complex sends proteins to their different destinies. Proteins destined to a certain place are packaged all together in the same vesicle and sent to the target organelle. In the case of membrane proteins, they are packaged in vesicles and sent to the cell membrane where they get incrusted.
There are certain signal sequences in the <u>carboxy-terminal extreme</u> of the protein that plays an important role during the transport of membrane proteins. A signal as simple as one amino acid in the c-terminal extreme is responsible for the correct transport of the molecule through the whole traject until it reaches the membrane.
Answer:
D. Useless
Explanation:
According to Dictionary.com, “in vain” is defined as “without real significance, value, or importance; baseless or worthless.”
Answer:
A
Explanation:
Stretching of the atrium and ventricle muscles
Answer: promoting the rapid resynthesis of ATP, by the action of creatine kinase.
Explanation:
Adenosine triphosphate (ATP) is the main form of chemical energy, its hydrolysis remaining highly exergonic. The maintenance of cellular homeostasis mechanisms, that adjust the generation processes of ATP, responds to the energy demand.
Creatine phosphate (CrP) was discovered in 1927 in the muscle tissue. Free creatine (Cr) is generated from the breakage of (CrP) during muscle contraction. Since the PCr / CK (Creatine kinase) system has a high rate of ATP generation, it is particularly important in situations of high metabolic demand, such as high-intensity physical exercise, when the ATP utilization rate exceeds its generation capacity by other metabolic pathways.
Hi! Spores are produced by sporophyte, or the spore bearing generation. Spores can be found in non seed bearing plants; like liverworts, hornworts, mosses and ferns. In ferns, you could physically find spores on the underside of the frond. These sporangia may clump together as well, to form sori. I hope this helps, let me know if you have more questions!
