General Biology: Core Concepts and Terminology Study Guide

Macromolecules

Classes of Macromolecules

Macromolecules are large, complex molecules essential for life. Most biological macromolecules are polymers, composed of repeating subunits.

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

• Proteins: Polymers of amino acids. Example: Enzymes, 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 with macromolecules due to their size and biological importance, but they do not form polymers by repetitive monomer linkage.

Carbohydrates

Aldoses and Ketoses

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

• Aldoses: Monosaccharides with an aldehyde group at the end (e.g., glucose).

• Ketoses: Monosaccharides with a ketone group within the carbon chain (e.g., fructose).

Organic Chemistry Basics

Asymmetrical (Chiral) Carbon

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

• Chirality leads to molecules with non-superimposable mirror images (enantiomers).

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

Proteins

Amino Acid Composition

Amino acids are the building blocks of proteins, each with a specific structure.

• Amino group ($-NH_2$)

• Carboxyl group ($-COOH$)

• Hydrogen atom

• R group (side chain, variable)

• Central (alpha) carbon

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).

• R group properties: Can be nonpolar, polar, acidic, or basic.

• Example: Acidic R groups donate protons; basic R groups accept protons.

Types of R Groups

• Nonpolar: Hydrophobic, e.g., leucine.

• Polar: Hydrophilic, e.g., serine.

• Acidic: Negatively charged, e.g., glutamic acid.

• Basic: Positively charged, e.g., lysine.

Nucleic Acids

DNA Base Pairing

DNA consists of two strands held together by hydrogen bonds between complementary bases.

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

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

Cell Biology

Basic Features Shared by All Cells

All cells, regardless of type, share certain fundamental features.

• Plasma membrane

• Cytoplasm

• Genetic material (DNA)

• Ribosomes

• Metabolic machinery

Prokaryotic vs. Eukaryotic Cells

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

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Organelles	Few, non-membrane bound	Many, membrane-bound
Size	Smaller	Larger
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Cell Organelles

Organelles are specialized structures within eukaryotic cells, each with distinct functions.

• Nucleus: Stores genetic material, controls cell activities.

• Mitochondria: Site of cellular respiration, ATP production.

• Chloroplasts: Site of photosynthesis (in plants and algae).

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

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

• Lysosomes: Digestion and waste removal.

• Peroxisomes: Breakdown of fatty acids and detoxification.

• Ribosomes: Protein synthesis.

Additional info: Visual identification of organelles is often required in exams; focus on shape and location within the cell.

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 within cells.

• Microfilaments (actin filaments): Cell shape, movement.

• Microtubules: Organelle movement, cell division.

• Intermediate filaments: Mechanical strength.

• Motor proteins: Move along cytoskeletal filaments (e.g., kinesin, dynein, myosin).

Extracellular Matrix (ECM)

The ECM is a network of proteins and carbohydrates outside animal cells, providing structural and biochemical support.

• Components: Collagen, proteoglycans, fibronectin, integrins.

• Functions: Cell adhesion, communication, tissue support.

Plasma Membrane

Composition

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

• Phospholipid bilayer: Hydrophilic heads, hydrophobic tails.

• Proteins: Integral and peripheral, involved in 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 in solution compared to the cell.

Solution Type	Effect on Cell	Water Flow
Isotonic	No net change	Equal in and out
Hypotonic	Cell swells	Water flows into cell
Hypertonic	Cell shrinks	Water flows out of cell

Equation for diffusion rate:

$J = -D \frac{dC}{dx}$

Where $J$ is the flux, $D$ is the diffusion coefficient, and $\frac{dC}{dx}$ is the concentration gradient.

Summary

Be familiar with all bolded terms and their associated information, as well as visual identification of structures and understanding of their functions.