Gap junctions are are closed at high  concentrations and open at low  concentrations.

Kinases are enzymes that add phosphate groups to molecules. Phosphatases remove phosphate groups from molecules. Common reducing agents in biological systems are , , and antioxidant molecules such as vitamins C and E. Transferases catalyze reactions in which one part of a molecule is transferred elsewhere on that same molecule or onto another molecule.

The action of a phosphatase is to remove a phosphate group from a molecule. A kinase adds phosphate groups, an isomerase rearranges bonds, a ligase forms a chemical bond, and a lyase breaks a chemical bond.

The potassium channel is initially  wide at its entry point - this already excludes many molecules that are not . As molecules travel further down the channel, though, the channel becomes much tighter and essentially only allows for  to continue. However,  is surrounded by water molecules. sheds these water molecules caged around it in order to move through the channel, thereby maintaining specificity for potassium and excluding water from the channel.

Vitamins D, E, A, and K are all fat soluble vitamins. Vitamin A (retinol) plays an important role in the visual pigments within the rods and cones of the retina. Deficiency of this vitamin produces night blindness, as these important retinal cells are unable to function properly.

Nucleic acids are a type of macromolecules that make up the genetic material. This is their main function. Unlike the other three macromolecules (carbohydrates, lipids, and proteins), nucleic acids are not used for energy production; therefore, the results stated in this question don’t seem valid.

Both DNA and RNA are made up of nucleic acids. Recall that all nucleic acids are made up of nucleotides, which are made up of phosphate group, nitrogenous base, and pentose sugar. The difference between DNA and RNA is that the pentose sugar in DNA is deoxyribose whereas pentose sugar in RNA is ribose. Also, RNA contains uracil nitrogenous base instead of the thymine found in DNA.

The main function of nucleic acid is to form the genetic material. Recall that DNA is utilized to make RNA (also made up of nucleic acid) during transcription. There are three kinds of RNA molecules: mRNA, tRNA, and rRNA. mRNA is used to synthesize proteins, tRNA facilitates protein synthesis, and rRNA makes up ribosomes; therefore, nucleic acids are important for formation of ribosomes. Remember that nucleic acids are not used to synthesize ATP or store energy in any form.  ATP itself is a nucleoside triphosphate, not a nucleic acid.

This question is asking us to identify a false function of nucleotides. As such, we'll need to consider each answer choice, one by one, in order to see which are true and which aren't.

One function that most people would immediately associate with nucleotides is the carrying of genetic information. In DNA, the order of nucleotides is what makes genes unique in terms of what proteins they code for. DNA sequences also play a regulatory role in gene expression, but ultimately, the sequence of nucleotides is what allows hereditary information to be passed to offspring.

Some of the other functions of nucleotides may not be readily apparent, but we'll go through each of them. For one thing, nucleotides can act as energy carriers. For instance, ATP is a nucleotide containing three phosphate groups along with the sugar ribose and the nitrogenous base adenine. ATP is the main energy-carrying molecule in cells, as it provides energy for many chemical reactions.

Nucleotides can also act as enzyme cofactors, otherwise called coenzymes. These coenzymes are an important component of the enzymes in which they are associated with, and help the enzyme to perform its proper function. Some examples of nucleotide coenzyems are nicotinamide adenine dinucleotide (NADH) and Coenzyme A (CoA), as in acetyl-CoA, an important intermediate in oxidative phosphorylation.

Additionally, the cyclic nucleotide cyclic-AMP (cAMP) is an important second messenger in signal transduction cascades that involve G proteins. During the cascade, levels of cAMP increase and lead to the activation of protein kinase A (PKA), which subsequently goes on to phosphorylate many other proteins within the cell.

Finally, it's important to take note of the false function of nucleotides (and the correct answer). Nucleotides do not play a role in maintaining the fluidity of cell membranes. Rather, a lipid molecule called cholesterol is responsible for this function.

The name ATP (adenosine triphosphate) tells you much of what you need to answer this question. It contains the base adenine, and three phosphate units. The phosphate units store the majority of its energy through phosphoanhydride bonds. ATP is also regarded as a short term energy molecule, and is readily used by the body. Finally, ATP contains a five-carbon ribose, not a six-carbon glucose ring.