General Biology: Core Concepts and Terminology Study Guide

Macromolecules

Polymer Classes and Non-Polymer Macromolecules

Biological macromolecules are large molecules essential for life, often formed by polymerization of smaller subunits.

• Carbohydrates: Polymers made of monosaccharide units. Example: Starch, glycogen.

• Proteins: Polymers of amino acids. Example: Hemoglobin.

• Nucleic acids: Polymers of nucleotides. Example: DNA, RNA.

• Lipids: Not true polymers; composed of fatty acids and glycerol. Example: Phospholipids, triglycerides.

Additional info: Lipids are grouped as macromolecules due to their size and biological importance, but they do not form polymers by repetitive monomer linkage.

Carbohydrates

Aldoses and Ketoses

Monosaccharides are classified based on the location of their carbonyl group.

• Aldose: Sugar with an aldehyde group (e.g., glucose).

• Ketose: Sugar with a ketone group (e.g., fructose).

Example: Glucose is an aldose; fructose is a ketose.

Organic Chemistry Fundamentals

Asymmetrical (Chiral) Carbon

An asymmetrical carbon, also called a chiral carbon, is a carbon atom attached to four different groups.

• Chiral center: Source of stereoisomerism in organic molecules.

• Example: The alpha carbon in amino acids (except glycine) is chiral.

Proteins

Amino Acid Structure

Amino acids are the building blocks of proteins, each with a central (alpha) carbon bonded to four groups.

• Amino group ($-NH_2$)

• Carboxyl group ($-COOH$)

• Hydrogen atom

• R group (side chain, variable)

Visual identification: Look for the central carbon with these four attachments.

Polypeptide Composition

Polypeptides are chains of amino acids linked by peptide bonds.

• Peptide bond: Covalent bond between the carboxyl group of one amino acid and the amino group of another.

• Primary structure: Sequence of amino acids.

Chemical Activity of Amino Acids

The chemical activity of an amino acid is determined by its R group (side chain).

• Polar, nonpolar, acidic, or basic properties affect protein folding and function.

Types of R Groups

Amino acid R groups can be classified as:

• Nonpolar (hydrophobic)

• Polar (hydrophilic)

• Acidic (negatively charged)

• Basic (positively charged)

Nucleic Acids

DNA Base Pairing and Hydrogen Bonds

DNA consists of two strands held together by base pairing.

• Adenine (A) pairs with Thymine (T) via 2 hydrogen bonds.

• Guanine (G) pairs with Cytosine (C) via 3 hydrogen bonds.

Base Pair	Hydrogen Bonds
A-T	2
G-C	3

Cell Biology

Basic Features Shared by All Cells

All cells possess certain fundamental structures:

• Plasma membrane

• Cytoplasm

• Genetic material (DNA)

• Ribosomes

• Ability to reproduce

Prokaryotic vs. Eukaryotic Cells

Cells are classified as prokaryotic or eukaryotic based on structural differences.

Feature	Prokaryotic	Eukaryotic
Nucleus	Absent	Present
Organelles	Absent	Present
Size	Smaller	Larger
Examples	Bacteria, Archaea	Plants, Animals, Fungi

Organelles: Functions and Identification

Major organelles and their functions:

• Nucleus: Stores genetic material, controls cell activities.

• Mitochondria: Site of cellular respiration, ATP production.

• Chloroplasts: Site of photosynthesis (plants, algae).

• Endoplasmic reticulum (ER): Protein and lipid synthesis.

• Golgi apparatus: Modifies, sorts, and packages proteins.

• Lysosomes: Digestion and waste removal.

• Ribosomes: Protein synthesis.

• Vacuoles: Storage and structural support (plants).

Additional info: Visual identification often relies on shape, location, and internal structure in micrographs.

Mitochondria and Chloroplast Compartments

• Mitochondria: Outer membrane, inner membrane, intermembrane space, matrix, cristae.

• Chloroplasts: Outer membrane, inner membrane, stroma, thylakoid membrane, grana.

Cytoskeleton and Motor Proteins

The cytoskeleton provides structural support and facilitates movement.

• Microtubules, microfilaments, intermediate filaments: Main components.

• Motor proteins: Kinesin, dynein, myosin—move cargo along cytoskeletal tracks.

Extracellular Matrix (ECM)

The ECM is a network outside animal cells that provides structural and biochemical support.

• Components: Collagen, proteoglycans, fibronectin, integrins.

• Functions: Cell adhesion, communication, structural support.

Plasma Membrane

Composition and Structure

The plasma membrane is a selectively permeable barrier composed mainly of phospholipids.

• Phospholipid bilayer: Hydrophilic heads, hydrophobic tails.

• Proteins: Integral and peripheral, for transport and signaling.

• Cholesterol: Modulates fluidity.

• Carbohydrates: Cell recognition.

Transport Across Membranes

Diffusion, Osmosis, and Tonicity

Transport processes regulate movement of substances across cell membranes.

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Tonicity: Relative concentration of solutes; affects water movement.

Directional water flow: Water moves from hypotonic (low solute) to hypertonic (high solute) solutions.

Equation for osmosis:

$ext{Water potential} ( ext{Ψ}) = ext{Ψ}_s + ext{Ψ}_p$

where $ext{Ψ}_s$ is solute potential and $ext{Ψ}_p$ is pressure potential.

Summary

Be familiar with all bolded terms and their associated information from lectures, as these are foundational for understanding cell structure, function, and molecular biology.