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Critical Thinking

MicrobiologyCritical Thinking

Critical Thinking


The structural formula shown corresponds to penicillin G, a narrow-spectrum antibiotic that is given intravenously or intramuscularly as a treatment for several bacterial diseases. The antibiotic is produced by fungi of the genus Penicillium. (a) Identify three major functional groups in this molecule that each comprise two simpler functional groups. (b) Name the two simpler functional groups composing each of the major functional groups identified in (a).

A complex chemical figure begins with a ring of Cs; each C is double bonded to one other C.  Off this ring is a CH2, then a C with a double bonded O, then an NH, then a C in a square. This square has Cs in 3 corners and an N in the fourth. The top left C is attached to the previous components discussed here, the bottom left C is double bonded to an O. The top right C is bound to an S, which is bound to a C, which is bound to a CH, which is bound to the N in the square. Back to the C that is attached to the S – this C is bound to two CH3s. The C attached to the N is bound to a C that is double bonded to an O and bound to an OH.

The figure depicts the structural formulas of glucose, galactose, and fructose. (a) Circle the functional groups that classify the sugars either an aldose or a ketose, and identify each sugar as one or the other. (b) The chemical formula of these compounds is the same, although the structural formula is different. What are such compounds called?

Galactose has 6 carbons with a double bonded O at carbon 1; all other carbons have one OH. The difference between glucose and galactose is the direction of the OH groups. Fructose has 6 carbons with a double bonded O at carbon 2; all other carbons have one OH.

Structural diagrams for the linear and cyclic forms of a monosaccharide are shown. (a) What is the molecular formula for this monosaccharide? (Count the C, H and O atoms in each to confirm that these two molecules have the same formula, and report this formula.) (b) Identify which hydroxyl group in the linear structure undergoes the ring-forming reaction with the carbonyl group.

A chain of 5 Carbons. Carbon 1 has a double bonded O and an H. Carbons 2, 3, and 4, each have an OH above the chain and an H below. Carbon 5 has an OH and 2 Hs. The second image is a pentagon. The top point is an O. Moving clockwise, each of the next 3 points are attached to an OH and an H. The last point is attached to an H and a CH2OH.

The term “dextrose” is commonly used in medical settings when referring to the biologically relevant isomer of the monosaccharide glucose. Explain the logic of this alternative name.


Microorganisms can thrive under many different conditions, including high-temperature environments such as hot springs. To function properly, cell membranes have to be in a fluid state. How do you expect the fatty acid content (saturated versus unsaturated) of bacteria living in high-temperature environments might compare with that of bacteria living in more moderate temperatures?


Heating a protein sufficiently may cause it to denature. Considering the definition of denaturation, what does this statement say about the strengths of peptide bonds in comparison to hydrogen bonds?


The image shown represents a tetrapeptide. (a) How many peptide bonds are in this molecule? (b) Identify the side groups of the four amino acids composing this peptide.

A green 5-C chain linked to an NH linked to a black 2 C chain linked to an NH linked to a black 2 C chain linked to an NH linked to a blue 5 C chain.
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