Macromolecules and Biochemistry: Structure, Function, and Key Concepts

Ch5 Pearson Study Guide from Study Guide

Macromolecules in Biology

Overview of Biological Macromolecules

Biological macromolecules are large, complex molecules essential for life. They include carbohydrates, lipids, proteins, and nucleic acids, each with unique structures and functions.

• Organic Molecule: A molecule containing carbon atoms, typically found in living organisms.

• Macromolecule: A large molecule formed by polymerization of smaller subunits (monomers).

• Biomolecule: Any molecule produced by living organisms, including macromolecules.

Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as energy sources and structural components.

• Monosaccharides: Simple sugars (e.g., glucose, fructose, galactose, ribose, deoxyribose).

• Disaccharides: Two monosaccharides joined by a glycosidic linkage (e.g., sucrose, lactose, maltose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, glycogen, cellulose, chitin).

• Dehydration Synthesis: Reaction that joins monomers by removing water.

• Hydrolysis: Reaction that breaks polymers into monomers by adding water.

Example: Starch is a storage polysaccharide in plants; glycogen is the storage form in animals.

Lipids

Lipids are hydrophobic molecules, including fats, oils, and steroids. They function in energy storage, membrane structure, and signaling.

• Saturated Fatty Acids: No double bonds between carbon atoms; solid at room temperature.

• Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.

• Triglyceride: Composed of three fatty acids bonded to a glycerol molecule.

• Phospholipid: Contains a phosphate group; major component of cell membranes.

• Steroids: Lipids with a four-ring structure (e.g., cholesterol, sex hormones).

Example: Phospholipids form the bilayer of cell membranes, providing structural integrity and regulating transport.

Proteins

Proteins are polymers of amino acids and perform a wide range of functions, including catalysis, transport, and structural support.

• Amino Acid: Building block of proteins; contains an amino group, carboxyl group, and R group.

• Peptide Bond: Covalent bond joining amino acids in a protein.

• Polypeptide: Chain of amino acids.

• Protein Structure:

  • Primary: Sequence of amino acids.

  • Secondary: Alpha helix and beta sheet formed by hydrogen bonding.

  • Tertiary: 3D folding due to interactions among R groups.

  • Quaternary: Association of multiple polypeptide chains.

Example: Hemoglobin is a protein that transports oxygen in the blood.

Nucleic Acids

Nucleic acids store and transmit genetic information. The two main types are DNA and RNA.

• Nucleotide: Monomer of nucleic acids; consists of a pentose sugar, phosphate group, and nitrogenous base.

• DNA (Deoxyribonucleic Acid): Contains deoxyribose sugar; bases are adenine, thymine, cytosine, guanine.

• RNA (Ribonucleic Acid): Contains ribose sugar; bases are adenine, uracil, cytosine, guanine.

• Phosphodiester Bond: Links nucleotides in a nucleic acid chain.

• ATP (Adenosine Triphosphate): Energy-carrying molecule in cells.

Example: DNA stores genetic information; RNA is involved in protein synthesis.

Key Chemical Reactions and Properties

Dehydration Synthesis and Hydrolysis

These reactions are essential for building and breaking down macromolecules.

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Equation for Dehydration Synthesis:

$\text{Monomer}_1 + \text{Monomer}_2 \xrightarrow{\text{Dehydration}} \text{Polymer} + H_2O$

Equation for Hydrolysis:

$\text{Polymer} + H_2O \xrightarrow{\text{Hydrolysis}} \text{Monomer}_1 + \text{Monomer}_2$

Structure and Function Relationships

Levels of Protein Structure

Proteins have four levels of structure, each contributing to their function.

• Primary Structure: Linear sequence of amino acids.

• Secondary Structure: Local folding into alpha helices and beta sheets.

• Tertiary Structure: Overall 3D shape of a single polypeptide.

• Quaternary Structure: Arrangement of multiple polypeptide subunits.

Comparison Table: Macromolecules

Macromolecule	Monomer	Bond Type	Main Function	Example
Carbohydrate	Monosaccharide	Glycosidic linkage	Energy storage, structure	Starch, cellulose
Lipid	Fatty acid, glycerol	Ester bond	Energy storage, membranes	Triglyceride, phospholipid
Protein	Amino acid	Peptide bond	Catalysis, structure, transport	Hemoglobin, keratin
Nucleic Acid	Nucleotide	Phosphodiester bond	Genetic information	DNA, RNA

Sample Problems and Applications

Practice Questions

Understanding these concepts is essential for success in biology. Practice questions may include:

• Identifying the correct structure and function of macromolecules.

• Matching monomers to their polymers.

• Describing the levels of protein structure.

• Comparing saturated and unsaturated fatty acids.

• Explaining the role of ATP in cellular energy.

Example: Which carbohydrate is the main energy-storage molecule in plants? Answer: Starch.

Additional info:

• Some content inferred from context and standard biology curriculum, such as the definition of macromolecules and the function of ATP.

• Practice questions and answer key suggest a focus on foundational biochemistry and molecular biology concepts.