General Biology: Macromolecules, Proteins, and Nucleic Acids Study Guide

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Macromolecules in Biology

Definition and Types of Biomolecules

Biomolecules are large, complex molecules that are essential for life. They include carbohydrates, proteins, lipids, and nucleic acids. Each type has distinct structures and functions within living organisms.

Carbohydrates: Provide energy and structural support. Examples: glucose, cellulose, starch.
Proteins: Serve as enzymes, structural components, and signaling molecules. Examples: hemoglobin, collagen.
Lipids: Store energy, form cell membranes, and act as signaling molecules. Examples: fats, oils, phospholipids.
Nucleic Acids: Store and transmit genetic information. Examples: DNA, RNA.

Example: Glucose is a carbohydrate that provides energy for cellular processes.

Hydrophobic vs. Hydrophilic

Hydrophobic molecules repel water, while hydrophilic molecules attract water. This property affects how molecules interact in biological systems.

Hydrophobic: Nonpolar molecules, such as oils and fats.
Hydrophilic: Polar molecules, such as sugars and salts.

Example: Cell membranes contain hydrophobic lipid tails and hydrophilic phosphate heads.

Amino Acids and Proteins

Functional Groups in Amino Acids

Amino acids contain specific functional groups that determine their properties and reactivity.

Amino group (-NH2): Acts as a base.
Carboxyl group (-COOH): Acts as an acid.
R group (side chain): Determines the identity and characteristics of each amino acid.

Example: Glycine has a hydrogen atom as its R group, making it the simplest amino acid.

Peptide Bond Formation

Peptide bonds link amino acids together to form proteins. This occurs through a dehydration synthesis reaction.

Dehydration/Condensation Reaction: Water is removed as a bond forms between the carboxyl group of one amino acid and the amino group of another.

Equation:

Levels of Protein Structure

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

Level of Folding	Description	Types of Bonds
Primary	Sequence of amino acids	Peptide bonds
Secondary	Local folding into alpha helices and beta sheets	Hydrogen bonds
Tertiary	Three-dimensional folding of a single polypeptide	Hydrogen, ionic, disulfide, hydrophobic interactions
Quaternary	Association of multiple polypeptide chains	Same as tertiary

Carbohydrates

Types and Functions

Carbohydrates are classified based on their complexity and function.

Monosaccharides: Simple sugars (e.g., glucose, fructose).
Disaccharides: Two monosaccharides joined (e.g., sucrose, lactose).
Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose, glycogen).

Example: Starch is a polysaccharide used for energy storage in plants.

Bond Types in Carbohydrates

Carbohydrates are linked by glycosidic bonds, which can be broken by enzymes.

Glycosidic Bond: Covalent bond between two monosaccharides.
Enzymatic Breakdown: Amylase breaks down starch; cellulase breaks down cellulose.

Example: Humans can digest starch but not cellulose due to lack of cellulase.

Nucleic Acids

Structure of Nucleotides

Nucleotides are the building blocks of nucleic acids. Each nucleotide consists of three components:

Pentose Sugar: Deoxyribose in DNA, ribose in RNA.
Nitrogenous Base: Adenine, thymine (DNA only), uracil (RNA only), cytosine, guanine.
Phosphate Group: Links nucleotides together.

Example: ATP is a nucleotide that stores energy for cellular processes.

DNA vs. RNA Comparison

DNA and RNA differ in structure and function. The following table summarizes their differences:

Component	DNA	RNA
Pentose Sugar	Deoxyribose	Ribose
Nitrogenous Base	A, T, C, G	A, U, C, G
Strandedness	Double-stranded	Single-stranded
Functionality	Genetic information storage	Protein synthesis, gene regulation

Base Pairing Rules

Base pairing ensures accurate replication and transcription of genetic material.

DNA: Adenine (A) pairs with Thymine (T); Cytosine (C) pairs with Guanine (G).
RNA: Adenine (A) pairs with Uracil (U); Cytosine (C) pairs with Guanine (G).

Equation:

Lipids

Saturated vs. Unsaturated Fats

Lipids are classified based on the presence of double bonds in their fatty acid chains.

Saturated Fats: No double bonds; solid at room temperature. Example: butter.
Unsaturated Fats: One or more double bonds; liquid at room temperature. Example: olive oil.

Additional info: Unsaturated fats are generally considered healthier than saturated fats due to their effects on cholesterol levels.