Since substance A ends up being positively charged, that means it must have lost or donated a negatively charged electron, thus it is oxidized and, is the reducing agent. Substance B ends up being negatively charged, so that means it gained an negatively charged electron, thus it is reduced and, is the oxidizing agent.

During the redox reaction chlorine becomes the negatively charged chloride ion, so we know that it has gained an electron. This means that it underwent reduction and is an oxidizing agent. Sodium loses an electron since it becomes positively charge, thus we know it has been oxidized and is the reducing agent.

This is an example of an oxidation-reduction reaction or redox reaction. In a redox reaction, a negatively charged electron from one substance (sodium in this case) is transferred to another substance (chlorine in this case). This results in a positively charge sodium ion and a negatively charge chloride ion.

Since substance A is losing an electron it is undergoing oxidation (oxidation is loss of electrons). Substance B is gaining an electron and so it is undergoing reduction (reduction is gain of electrons). Substance A is the reducing agent because it causes the reduction of substance B, and substance B is the oxidizing agent because it causes the oxidation of substance A.

Since substance B is losing an electron it is undergoing oxidation (oxidation is loss of electrons). Substance A is gaining an electron and so it is undergoing reduction (reduction is gain of electrons). Substance B is the reducing agent because it causes the reduction of substance A, and substance A is the oxidizing agent because it causes the oxidation of substance B.

Since substance A ends up being positively charged, that means it must have lost or donated a negatively charged electron, thus it is oxidized and, is the reducing agent. Substance B ends up being negatively charged, so that means it gained an negatively charged electron, thus it is reduced and, is the oxidizing agent.  

During the redox reaction chlorine becomes the negatively charged chloride ion, so we know that it has gained an electron. This means that it undergone reduction and is an oxidizing agent. Sodium loses an electron since it becomes positively charge, thus we know it has been oxidized and is the reducing agent.

Desmosomes are the primary junction that helps keep tissues that are under a lot of stress, like skin, intact. Although tight junctions typically accompany desmosomes, their primary function is to prevent substances from passing between cells. Gap junctions are used for communication between cells, and intercalated discs are only found in cardiac muscle tissue.

The lysosome is an organelle that is used to digest broken cellular machinery or foreign particles. It maintains an acidic environment inside by pumping hydrogen ions in, not out. This environment helps denature the things it needs to digest, and is the most effective pH for the digestive enzymes that are inside.

The other structures do not maintain acidic environments, and would need the capability of removing protons.

The simple answer here is that all of these organelles have a membrane, except for ribosomes. Nuclei, mitochondria, chloroplasts, and cells as a whole have transmembrane proteins spanning the lipid bilayer, which can be used for transport or other purposes. Ribosomes are mostly comprised of rRNA and do not have membranes; thus, they will not bear transmembrane proteins.