Ch. 2 Chemistry Comes Alive

Marieb - Human Anatomy & Physiology 11th Edition

Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Not the one you use?Change textbook

Marieb, Hoehn 11th Edition

Ch. 2 Chemistry Comes Alive

Problem 16

Chapter 2, Problem 16

A chemist, during the course of an analysis, runs across a chemical composed of carbon, hydrogen, and oxygen in the proportion 1:2:1 and having a six-sided molecular shape. It is probably:
a. A pentose
b. An amino acid
c. A fatty acid
d. A monosaccharide
e. A nucleic acid

Verified step by step guidance

Step 1: Identify the elemental ratio given in the problem: carbon, hydrogen, and oxygen in the proportion 1:2:1. This ratio is a key clue to the type of molecule.

Step 2: Recall that carbohydrates typically have the general formula \(C_nH_{2n}O_n\), which matches the 1:2:1 ratio of carbon to hydrogen to oxygen atoms.

Step 3: Consider the molecular shape described as six-sided. This suggests a ring structure with six atoms, which is common in monosaccharides like glucose that form six-membered rings (hexoses).

Step 4: Evaluate the options: a pentose is a five-carbon sugar, an amino acid contains nitrogen and does not follow the 1:2:1 ratio, a fatty acid has a different elemental composition, and nucleic acids are polymers containing nitrogenous bases and phosphate groups.

Step 5: Conclude that the molecule is most likely a monosaccharide, as it fits both the elemental ratio and the six-sided ring structure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Empirical Formula and Molecular Composition

The empirical formula represents the simplest whole-number ratio of elements in a compound. A ratio of carbon, hydrogen, and oxygen as 1:2:1 is characteristic of carbohydrates, especially monosaccharides, which often follow the general formula Cn(H2O)n.

Monosaccharide Structure and Characteristics

Monosaccharides are simple sugars with a basic formula of (CH2O)n, commonly forming ring structures with six atoms (five carbons and one oxygen). Their six-membered ring shape (pyranose form) is typical for glucose and related sugars.

Distinguishing Biomolecules by Composition and Structure

Different biomolecules have distinct elemental ratios and structures: amino acids contain nitrogen, fatty acids have long hydrocarbon chains with few oxygens, nucleic acids contain nitrogen and phosphorus, while pentoses are five-carbon sugars. Recognizing these differences helps identify the compound.

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Introduction to Biomolecules

Related Practice

Textbook Question

Which of the following covalently bonded molecules are polar?

(a)

(b)

(c)

(d)

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Textbook Question

Identify each reaction as one of the following:

a. A synthesis reaction

b. A decomposition reaction

c. An exchange reaction

(1) 2Hg + O₂ → 2HgO

(2) HCl + NaOH → NaCl + H₂O

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Textbook Question

How many moles of aspirin, C₉H₈O₄, are in a bottle containing 450 g by weight? (Note: The approximate atomic weights of its atoms are C = 12, H = 1, and O = 16.)

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Textbook Question

What are hydrogen bonds and how are they important in the body?

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Textbook Question

A deficiency in this element can be expected to reduce the hemoglobin content of blood:

a. Fe

b. I

c. F

d. Ca

e. K

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