You have a 12.5% w/v solution and a 3% w/v solution in stock. What volumes of each solution do you need to mix to make 855 mL of a 7% solution? Please round answers to the nearest whole number.

Absorption ointment bases are anhydrous preparations that can incorporate significant amounts of water or aqueous solutions to form water-in-oil (w/o) emulsions. Common examples include Aquaphor and Eucerin, which utilize lanolin or petrolatum derivatives as the primary vehicle. These bases are highly emollient, greasy, and difficult to wash off with water, making them ideal for treating severely dry skin or protecting compromised barriers.

Rationale:

A. Yellow Ointment, also known as simple ointment, consists of yellow wax and petrolatum. It is a strictly oleaginous base and does not possess the specific emulsifiers, like lanolin alcohols, found in the products pictured. Yellow Ointment lacks the water-incorporating capacity that characterizes the advanced repair and healing ointments shown in the exhibits.

B. Water-soluble bases, such as Polyethylene Glycol (PEG) ointment, are completely greaseless and consist of only water-soluble components. The products shown, Aquaphor and Eucerin, contain petrolatum, which is a lipid-based ingredient. Therefore, they are not water-soluble and cannot be categorized as greaseless, washable vehicles in a pharmaceutical context.

C. Absorption ointment bases is the correct classification for these products because they are designed to absorb aqueous fluids into the lipid phase. Aquaphor is an anhydrous absorption base that forms an emulsion when water is added, providing a protective occlusive layer. These bases are essential for rehydrating the stratum corneum by preventing transepidermal water loss.

D. Oleaginous ointment bases, such as white petrolatum or Vaseline, are strictly oily and contain no emulsifiers to pick up water. While absorption bases are lipid-heavy, they differ by their ability to internalize water. The products pictured contain specialized ingredients that allow them to function as emulsion precursors, distinguishing them from simple hydrocarbons.

E. Water-removable ointment bases are oil-in-water emulsions, commonly referred to as "vanishing creams." These can be easily rinsed from the skin with water because the aqueous phase is external. The pictured ointments are greasy and occlusive, meaning they stay on the skin surface and resist simple water rinsing, unlike water-removable creams.

Fermentation is a metabolic process that allows cells to produce ATP in the absence of oxygen. It involves the reduction of pyruvate to regenerate NAD+ from NADH, which is essential for glycolysis to continue. Different microorganisms utilize different pathways; yeasts typically perform alcoholic fermentation, while many bacteria and animal muscle cells perform lactic acid fermentation. These pathways are crucial for survival in hypoxic environments.

Rationale:

A. Glycerol is a three-carbon alcohol primarily involved in lipid synthesis and is not a standard end-product of pyruvate fermentation. While it can be a minor byproduct in some industrial yeast fermentations, it is not the primary yield of the anaerobic pathways tested here. Pyruvate is typically diverted toward simpler organic acids or alcohols.

B. Oxaloacetate is an intermediate in the Citric Acid Cycle and gluconeogenesis. Its production from pyruvate requires the enzyme pyruvate carboxylase and occurs under aerobic conditions or for anaplerotic reactions. It is not a product of fermentation, as fermentation aims to dump electrons rather than continue into oxidative metabolism.

C. Ethanol is a primary product of alcoholic fermentation performed by organisms like Saccharomyces cerevisiae. In this two-step process, pyruvate is first decarboxylated and then reduced. Ethanol serves as the electron sink, allowing the cell to maintain its redox balance while producing a small amount of energy from glucose catabolism.

D. CO2 (carbon dioxide) is released during the first step of alcoholic fermentation when pyruvate is converted to acetaldehyde by pyruvate decarboxylase. This gas production is responsible for the leavening of bread and the carbonation in fermented beverages. It is a key volatile byproduct of the anaerobic breakdown of carbohydrates in specific microorganisms.

E. Lactate is the product of homolactic or heterolactic fermentation, commonly found in Lactobacillus species. Pyruvate is reduced directly to lactate by the enzyme lactate dehydrogenase. This reaction is the primary way many bacteria and mammalian cells regenerate oxidized NAD+ during periods of oxygen deprivation or high metabolic demand.