Ch. 2 The Chemical Level of Organization

Martini - Fundamentals of Anatomy and Physiology 12th Edition

Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook

Martini, Nath, Bartholomew 12th Edition

Ch. 2 The Chemical Level of Organization

Problem 29

Chapter 2, Problem 29

A sample that contains an organic molecule has the following constituents: carbon, hydrogen, oxygen, nitrogen, and phosphorus. Is the molecule more likely to be a carbohydrate, a lipid, a protein, or a nucleic acid?

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Identify the key elements present in the molecule: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P).

Recall the typical elemental composition of the four major organic macromolecules: carbohydrates (C, H, O), lipids (C, H, O), proteins (C, H, O, N), and nucleic acids (C, H, O, N, P).

Note that carbohydrates and lipids do not contain nitrogen or phosphorus, while proteins contain nitrogen but not phosphorus, and nucleic acids contain both nitrogen and phosphorus.

Based on the presence of both nitrogen and phosphorus, conclude that the molecule is most likely a nucleic acid.

Understand that nucleic acids (DNA and RNA) are composed of nucleotides, which include a phosphate group (phosphorus), a nitrogenous base (nitrogen), and a sugar (carbon, hydrogen, oxygen).

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Key Concepts

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

Elemental Composition of Biomolecules

Different classes of biomolecules have characteristic elemental compositions. Carbohydrates mainly contain carbon, hydrogen, and oxygen; lipids also primarily contain these three elements; proteins contain carbon, hydrogen, oxygen, and nitrogen; nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus. Recognizing these elemental patterns helps identify the type of molecule.

Role of Phosphorus in Biomolecules

Phosphorus is a key element found predominantly in nucleic acids and some lipids (like phospholipids). Its presence alongside nitrogen strongly suggests the molecule could be a nucleic acid, as proteins generally do not contain phosphorus. Understanding the significance of phosphorus helps narrow down the molecule's identity.

Distinguishing Biomolecule Classes by Functional Groups

Biomolecules differ in their functional groups and structures: carbohydrates have hydroxyl and carbonyl groups; lipids are mostly hydrophobic with long hydrocarbon chains; proteins contain amino and carboxyl groups; nucleic acids have phosphate groups and nitrogenous bases. Identifying these groups based on elemental composition aids in classifying the molecule.

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Functional Groups

Related Practice

Textbook Question

In an exergonic reaction,

(a) Large molecules are broken down into smaller ones.

(b) Small molecules are assembled into larger ones.

(d) Molecules move from reactants to products and back.

(e) Energy is released during the reaction.

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Textbook Question

A certain reaction pathway consists of four steps. How would decreasing the amount of enzyme that catalyzes the second step affect the amount of product produced at the end of the pathway?

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Textbook Question

The hydrogen bonding that occurs in water is responsible for all of the following except

(a) The high boiling point of water

(b) The low freezing point of water

(d) The ability of water to dissolve inorganic salts

(e) The surface tension of water

Textbook Question

Explain the differences among nonpolar covalent bonds, polar covalent bonds, and ionic bonds.

Textbook Question

An important buffer system in the human body involves carbon dioxide (CO₂) and bicarbonate ion (HCO₃^-) in the reversible reaction

CO₂ + H₂O ⇌ H₂CO₃ ⇌ H⁺ + HCO₃^-

If a person becomes excited and exhales large amounts of CO₂, how will the pH of the person's body be affected?

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Textbook Question

An atom of the element calcium has 20 protons and 20 neutrons. Determine the following information about calcium:

(a) Number of electrons

(b) Atomic number

(d) Number of electrons in each energy level

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