Biological Macromolecules and Enzyme Function: Study Notes

Biological Macromolecules

Overview of Macromolecules

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

• Carbohydrates: Provide energy and structural support.

• Lipids: Store energy, form cell membranes, and act as signaling molecules.

• Proteins: Perform a wide range of functions, including catalysis, transport, and structural roles.

• Nucleic Acids: Store and transmit genetic information.

Functional Groups in Biological Molecules

Functional groups are specific groups of atoms within molecules that have characteristic properties and chemical reactivity.

Name	Structure	Example	Function
Carboxyl	COOH	Amino acids, fatty acids	Acts as an acid, donates H+
Phosphate	PO4	ATP, nucleic acids	Transfers energy between molecules
Hydroxyl	OH	Alcohols, carbohydrates	Makes molecules polar, forms hydrogen bonds
Sulfhydryl	SH	Cysteine (amino acid)	Forms disulfide bonds in proteins
Amino	NH2	Amino acids	Acts as a base, accepts H+

Additional info: Functional groups determine the chemical behavior of organic molecules.

Properties of Water

Water is vital for life due to its unique properties, which arise from its polarity and ability to form hydrogen bonds.

• Cohesion: Water molecules stick together, aiding transport in plants.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature changes, stabilizing environments.

• Solvent Properties: Water dissolves many substances, facilitating chemical reactions.

Carbohydrates

Structure and Function

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen, typically in a 1:2:1 ratio. They serve as energy sources and structural components.

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

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

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

Example: Starch is a storage polysaccharide in plants; glycogen serves a similar function in animals.

Lipids

Structure and Function

Lipids are hydrophobic molecules, including fats, oils, phospholipids, and steroids. They are important for energy storage, membrane structure, and signaling.

• Fats: Composed of glycerol and fatty acids; store energy.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Four fused carbon rings; include hormones like cholesterol.

Additional info: Lipids are insoluble in water due to their nonpolar nature.

Proteins

Structure and Levels of Organization

Proteins are polymers of amino acids linked by peptide bonds. Their structure determines their function.

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Local folding (α-helix, β-sheet) stabilized by hydrogen bonds.

• Tertiary Structure: 3D shape formed by interactions among R groups.

• Quaternary Structure: Association of multiple polypeptide chains.

Example: Hemoglobin is a protein with quaternary structure, composed of four polypeptide subunits.

Protein Functions

• Enzymes: Catalyze biochemical reactions.

• Transport: Carry substances (e.g., hemoglobin transports oxygen).

• Structural: Provide support (e.g., collagen in connective tissue).

• Signaling: Hormones and receptors.

Nucleic Acids

Structure and Function

Nucleic acids, including DNA and RNA, store and transmit genetic information. They are polymers of nucleotides, each consisting of a sugar, phosphate group, and nitrogenous base.

• DNA: Double helix, stores genetic information.

• RNA: Single-stranded, involved in protein synthesis.

Example: mRNA carries genetic instructions from DNA to ribosomes for protein synthesis.

Enzymes

Enzyme Structure and Function

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy. They are highly specific for their substrates.

• Active Site: Region where substrate binds and reaction occurs.

• Induced Fit Model: Enzyme changes shape to better fit the substrate.

• Catalysis: Enzymes lower the activation energy required for reactions.

Equation:

$E + S \rightarrow ES \rightarrow E + P$

Where E = enzyme, S = substrate, ES = enzyme-substrate complex, P = product.

Factors Affecting Enzyme Activity

• Temperature: Each enzyme has an optimal temperature; high temperatures can denature enzymes.

• pH: Each enzyme has an optimal pH range.

• Substrate Concentration: Increased substrate increases reaction rate up to a saturation point.

• Inhibitors: Molecules that decrease enzyme activity (competitive and noncompetitive inhibitors).

ATP: The Energy Currency

ATP (adenosine triphosphate) stores and transfers energy within cells. Hydrolysis of ATP releases energy for cellular processes.

Equation:

$ATP + H_2O \rightarrow ADP + P_i + \text{energy}$

Where ADP = adenosine diphosphate, $P_i$ = inorganic phosphate.

Summary Table: Macromolecules and Their Functions

Macromolecule	Monomer	Function	Example
Carbohydrate	Monosaccharide	Energy, structure	Glucose, starch
Lipid	Fatty acid, glycerol	Energy storage, membranes	Triglyceride, phospholipid
Protein	Amino acid	Catalysis, structure, transport	Enzyme, hemoglobin
Nucleic Acid	Nucleotide	Genetic information	DNA, RNA