A scientist observes some cells under a compound microscope and needs to determine if they are bacteria or yeast. Aside from size, what chemical compounds (not organelles!) would positively identify the cell as either a bacterium or a yeast?

The chemical compounds that will help differentiate a yeast from a bacteria is chitin and murein.

Chitin is found in fungi which is the kingdom  yeast belongs to. It is a polysaccharide tightly packed in the exoskeleton and consists of chains of modified glucose known as N-acetylglucosamine.

Murein is a structure  which consists of sugar and amino acids. Murein forms a layer outside the plasma membrane of bacterial cell. Bacteria lacks chitin and Yeast lacks murein which makes it a good way of differentiating between bacteria and yeast.

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chitin and murein

Explanation:

The chemical compounds that distinguish bacteria cell from yeast cell are  

chitin and murein

Chitin is a polysaccharide present in the exoskeleton of fungi made up of chains of modified glucose known as N-acetylglucosamine. N-acetylglucosamine is derived from glucose

While murein is a mesh like structure made up of sugar and amino acids. Murein forms a layer outside the plasma membrane of bacterial cell.  

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.