Carbohydrates include the monosaccharide glucose and polysaccharides starch and glycogen.  Amino acids contain nitrogen and are the building blocks of polypeptides.

Carbon dioxide is not very soluble in water, so it is carried in the blood almost exclusively as carbonic acid. While some carbon dioxide is bound to hemoglobin, the majority of it is carried in the blood as the bicarbonate ion, which is the blood's main buffer. Note the following chemical equilibria:

A redox or oxidation-reduction reaction involves the transfer of electrons from one substance to another. The loss of an electron from a substance is called oxidation. The gain of electrons to another substance is called reduction. A mnemonic that is often useful in remembering this is: OIL RIG, where Oxidation Is Loss of electrons and Reduction Is Gain of electrons.   

A redox or oxidation-reduction reaction involves the transfer of electrons from one substance to another. The loss of an electron from a substance is called oxidation. The gain of electrons to another substance is called reduction. A mnemonic that is often useful in remembering this is: OIL RIG, where Oxidation Is Loss of electrons and Reduction Is Gain of electrons.

A redox or oxidation-reduction reaction involves the transfer of electrons from one substance to another. The loss of an electron from a substance is called oxidation. The gain of electrons to another substance is called reduction. A mnemonic that is often useful in remembering this is: OIL RIG, where Oxidation Is Loss of electrons and Reduction Is Gain of electrons. Here, substance A gains an electron and is thus reduced by substance B. As a result, substance B is oxidized by substance A. The substance that is reduced is also known as the oxidizing agent, since it causes the oxidation of the other substance.

Reduction is the gain of electrons. Thus the substance that is reduced may become more negatively charged or less positively charged. However, the only possible answer of the choices is that it can become more negatively charged.

A redox or oxidation-reduction reaction involves the transfer of electrons from one substance to another. The loss of an electron from a substance is called oxidation. The gain of electrons to another substance is called reduction. A mnemonic that is often useful in remembering this is: OIL RIG, where Oxidation Is Loss of electrons and Reduction Is Gain of electrons. Here, substance A gains an electron and is thus reduced by substance B. As a result, substance B is oxidized by substance A. The substance that is oxidized is also known as the reducing agent, since it causes the reduction of the other substance.

Substance A is an oxidizing agent. When a substance acts as an electron acceptor it is an oxidizing agent. This is because it causes the oxidation of substance B upon accepting an electron. If the substance acts as an electron donor then it is a reducing agent. Recall the mnemonic: OIL RIG; Oxidation Is Loss of electrons, Reduction Is Gain of electrons. Acids and bases involve the exchange of electron pairs, or hydrogens not single electrons.

An electron donor is a reducing agent. That is because it is causing another substance (the electron acceptor) to be reduced. The electron acceptor is called the oxidizing agent. Recall the mnemonic: OIL RIG; Oxidation Is Loss of electrons, Reduction Is Gain of electrons. Acids and bases involve the exchange of electron pairs, or hydrogens not single electrons.

When a substance acts as an electron acceptor it is an oxidizing agent. This is because it causes the oxidation of the substance from which it accepted the electron upon accepting an electron. If the substance acts as an electron donor then it is a reducing agent. Recall the mnemonic: OIL RIG; Oxidation Is Loss of electrons, Reduction Is Gain of electrons.