Chapter 3: The Chemistry of Life - Organic Compounds and Carbohydrates

Flashcards covering polymers, condensation and hydrolysis reactions, monosaccharides, disaccharides, and polysaccharides from Chapter 3: The Chemistry of Life.

What is the relationship between macromolecules, polymers, and monomers?

Macromolecules are giant biological molecules consisting of thousands of atoms; most macromolecules are polymers, which are formed by linking small organic compounds called monomers.

Approximately how many simple monomers construct the complex organic compounds in organisms, and how many are amino acids?

Organisms construct thousands of different complex organic compounds from about $40$ small, simple monomers, including the $20$ monomers called amino acids that form proteins.

What occurs during a condensation reaction (dehydration synthesis)?

Monomers are covalently linked together while the equivalent of a molecule of water ($H_2O$) is removed.

How does a hydrolysis reaction break down polymers into monomers?

In a reaction regulated by a specific enzyme, water is added to break bonds: a hydrogen ($H$) from a water molecule attaches to one monomer, and a hydroxyl group ($-OH$) from water attaches to the adjacent monomer.

Are condensation and hydrolysis reactions catalyzed by the same enzymes?

No, condensation and hydrolysis reactions are catalyzed by different specific enzymes.

What is the characteristic ratio of atoms in carbohydrates, and what formula represents it?

Carbohydrates contain carbon, hydrogen, and oxygen atoms in a ratio of approximately one carbon to two hydrogens to one oxygen ($1:2:1$), represented by the empirical formula $(CH_2O)_n$.

How many carbon atoms do monosaccharides typically contain?

Monosaccharides typically contain from $3$ to $7$ carbon atoms.

What functional groups are attached to the carbon skeleton of a monosaccharide?

A hydroxyl group ($-OH$) is bonded to each carbon except one, which is double-bonded to an oxygen atom to form a carbonyl group ($C=O$).

What distinguishes an aldehyde monosaccharide from a ketone monosaccharide?

An aldehyde sugar has its carbonyl group at the terminal end of the carbon chain, whereas a ketone sugar has its carbonyl group located at an internal position within the chain.

By convention, where does the numbering of the carbon skeleton of an open-chain sugar begin?

Numbering begins with the carbon at or nearest the carbonyl end of the open chain.

What are two common trioses (three-carbon sugars), and how are they classified?

Glyceraldehyde (an aldehyde) and dihydroxyacetone (a ketone), both having the molecular formula $C_3H_6O_3$.

How does deoxyribose ($C_5H_{10}O_4$) differ structurally from ribose ($C_5H_{10}O_5$)?

Deoxyribose has one less oxygen atom than ribose; a hydrogen atom ($H$) is attached to carbon $2$ instead of a hydroxyl group ($-OH$).

Why are glucose and fructose classified as structural isomers?

They share the identical molecular formula ($C_6H_{12}O_6$) but have their atoms arranged differently: glucose is an aldehyde with a terminal carbonyl oxygen, while fructose is a ketone with its carbonyl oxygen linked to an internal carbon.

How do glucose and galactose differ structurally?

They are enantiomers (mirror images) that differ in the spatial arrangement of the hydroxyl group and hydrogen attached to asymmetrical carbon atom $4$.

How is a glucose ring formed in aqueous solution?

Glucose forms a ring consisting of five carbons and one oxygen when atoms undergo rearrangement, allowing a covalent bond to form between carbon $1$ and the oxygen attached to carbon $5$.

What is the structural difference between $\alpha$-glucose and $\beta$-glucose?

In $\alpha$-glucose, the hydroxyl group on carbon $1$ is located on the opposite side of the ring plane from the $-CH_2OH$ side group; in $\beta$-glucose, this hydroxyl group is on the same side as the $-CH_2OH$ side group.

What is a glycosidic linkage, and where does it typically form in a disaccharide?

A glycosidic linkage consists of a central oxygen covalently bonded to two carbons (one in each ring); it generally forms between carbon $1$ of one monosaccharide and carbon $4$ of the other.

What are the specific monosaccharide components of maltose, sucrose, and lactose?

Maltose consists of two covalently linked $\alpha$-glucose units; sucrose consists of a glucose unit combined with a fructose unit; lactose consists of one glucose unit and one galactose unit.

What are the chemical equations representing the digestive hydrolysis of maltose and sucrose?

$\text{Maltose} + \text{water} \rightarrow \text{glucose} + \text{glucose}$ and $\text{Sucrose} + \text{water} \rightarrow \text{glucose} + \text{fructose}$.

What is a polysaccharide, and what are three primary examples?

A polysaccharide is a macromolecule consisting of repeating units of simple sugars (usually thousands of glucose units) arranged as a single long chain or a branched chain; examples include starches, glycogen, and cellulose.