General Biology: Macromolecules, Cell Structure, Membranes, and Metabolism Study Guide

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Chapter 5: Biological Macromolecules

Monomer vs Polymer

Biological macromolecules are large molecules composed of smaller subunits called monomers. When monomers join together, they form polymers through specific chemical reactions.

Monomer: A small molecule that can bind to others to form a polymer (e.g., glucose, amino acids).
Polymer: A large molecule made up of repeating monomer units (e.g., starch, proteins).

Synthesis and Breakdown of Polymers

Dehydration: Chemical reaction that joins monomers by removing a water molecule.
Hydrolysis: Chemical reaction that breaks polymers into monomers by adding water.
Example Equation:

Carbohydrates

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

Structure and Function: Provide energy (glucose), store energy (starch, glycogen), and provide structure (cellulose, chitin).
Linkage: Glycosidic bonds connect monosaccharides.
Composition and Ratio: General formula is .
Types:
- Monosaccharide: Single sugar unit (e.g., glucose, fructose).
- Disaccharide: Two monosaccharides joined (e.g., sucrose = glucose + fructose).
- Oligosaccharide: 3-10 monosaccharides.
- Polysaccharide: Many monosaccharides (e.g., starch, glycogen, cellulose, chitin).
Storage Polysaccharides: Starch (plants), glycogen (animals).
Structural Polysaccharides: Cellulose (plants), chitin (fungi, arthropods).

Lipids

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

Fats (Triglycerides):
- Structure: Glycerol + 3 fatty acids.
- Function: Energy storage, insulation, protection.
- Linkage: Ester bonds.
- Saturated vs Unsaturated Fatty Acids: Saturated have no double bonds (solid at room temp); unsaturated have one or more double bonds (liquid at room temp).
Phospholipids:
- Structure: Glycerol, 2 fatty acids, phosphate group.
- Function: Main component of cell membranes; form bilayers.
- Behavior in Bilayer: Hydrophilic heads face water, hydrophobic tails face inward.
Steroids:
- Structure: Four fused carbon rings.
- Examples: Cholesterol, steroid hormones (e.g., estrogen, testosterone).

Proteins

Proteins are polymers of amino acids that perform a vast array of functions, including catalysis, structure, transport, and signaling.

Structure and Function: Determined by amino acid sequence and folding.
Linkage: Peptide bonds between amino acids.
Monomer vs Polymer: Amino acid (monomer), polypeptide/protein (polymer).
Structure of Amino Acid: Central carbon, amino group, carboxyl group, hydrogen, R group (side chain).
20 Amino Acids:
- Categories: Non-polar, polar, acidic, basic, aromatic.
- Naming: 3-letter and 1-letter abbreviations.
- Classification: Know which amino acids fall into each category.

Nucleic Acids

Nucleic acids (DNA and RNA) store and transmit genetic information.

Structure and Function: Polymers of nucleotides; DNA stores genetic info, RNA involved in protein synthesis.
Linkage: Phosphodiester bonds between nucleotides.
DNA vs RNA:
- Nucleotide vs Nucleoside: Nucleotide = base + sugar + phosphate; nucleoside = base + sugar.
- Bases: Purines (A, G) vs Pyrimidines (C, T, U).
- Sugars: Deoxyribose (DNA) vs Ribose (RNA).
- Strands: DNA is double-stranded, RNA is usually single-stranded.
- Base Pairing: A-T (DNA), A-U (RNA), G-C.
Gene Expression: DNA → RNA → Protein (Central Dogma).

Chapter 6: Cell Structure

Cell Theory

All living organisms are composed of cells, which are the basic units of life.

Eukaryotic vs Prokaryotic: Eukaryotes have a nucleus and membrane-bound organelles; prokaryotes do not.

The Nucleus

Structure: Nuclear envelope, nucleolus, chromatin.
Function: Stores genetic material, site of RNA synthesis.

Ribosomes

Structure: Composed of rRNA and proteins.
Function: Protein synthesis.

The Endomembrane System

Components: Nuclear envelope, endoplasmic reticulum (rough and smooth), Golgi apparatus, lysosomes, vacuoles.
Function: Synthesis, modification, and transport of proteins and lipids.

Mitochondria, Chloroplasts, Peroxisomes

Mitochondria: Site of cellular respiration (ATP production).
Chloroplasts: Site of photosynthesis (plants, algae).
Peroxisomes: Breakdown of fatty acids, detoxification.

The Cytoskeleton

Components: Microtubules, microfilaments, intermediate filaments.
Functions: Cell shape, movement, division, organelle transport.
Microtubules: Made of tubulin; form centrosomes, centrioles, cilia, flagella.
Microfilaments: Made of actin; involved in muscle contraction, cell movement.
Intermediate Filaments: Provide structural support.

Extracellular Components

Cell Wall: Provides structure (plants, fungi, some protists).
Extracellular Matrix (ECM): Network of proteins and carbohydrates outside animal cells; provides support and signaling.
Cell Junctions: Plasmodesmata (plants), tight junctions, desmosomes, gap junctions (animals).

Chapter 7: Membranes and Transport

Passive vs Active vs Bulk Transport

Passive Transport: Movement of substances down their concentration gradient (no energy required).
Active Transport: Movement against concentration gradient (requires energy, usually ATP).
Bulk Transport: Movement of large particles via vesicles (endocytosis, exocytosis).

Plasma Membrane

Phospholipid Amphipathic Structure: Hydrophilic heads, hydrophobic tails.
Fluid Mosaic Model: Membrane is a fluid structure with proteins embedded in or attached to the bilayer.
Fluidity of Membranes: Affected by temperature, fatty acid composition, cholesterol.

Selective Permeability

Solute vs Solvent: Solute is dissolved, solvent does the dissolving (usually water).
Permeability: Small, nonpolar molecules cross easily; large or charged molecules do not.

Membrane Proteins

Peripheral vs Integral Proteins: Peripheral are on the surface; integral span the membrane.
Types: Transport, transmembrane (carrier, channel), receptor, enzymatic.

Transport Processes

Diffusion: Movement of molecules from high to low concentration.
Osmosis: Diffusion of water across a selectively permeable membrane.
Facilitated Diffusion: Passive transport via proteins.
Tonicity: Effect of solute concentration on cell volume (hypotonic, hypertonic, isotonic).
Active Transport: Requires energy; examples include Na+/K+ pump, proton pump.
Cotransport: Coupled transport of two substances (e.g., sodium-glucose cotransport).
Bulk Transport: Exocytosis (out), endocytosis (in: phagocytosis, pinocytosis, receptor-mediated).

Chapter 8: Metabolism and Enzymes

Metabolic Pathways

Catabolic Pathways: Break down molecules, release energy.
Anabolic Pathways: Build molecules, consume energy.

Forms of Energy

Kinetic Energy: Energy of motion.
Potential Energy: Stored energy.
Chemical Energy: Potential energy in chemical bonds.

Laws of Thermodynamics

First Law: Energy cannot be created or destroyed, only transformed.
Second Law: Every energy transfer increases the entropy (disorder) of the universe.

ATP and Cellular Work

ATP: Adenosine triphosphate, main energy currency of the cell.
Energy Coupling: Use of exergonic processes to drive endergonic ones.
ATP Regeneration:

Enzymes

Function: Biological catalysts that speed up chemical reactions by lowering activation energy.
Substrate Specificity: Enzymes bind specific substrates at the active site (induced fit model).
Enzyme Kinetics: Rate of reaction affected by substrate concentration, temperature, pH.
Cofactors: Non-protein helpers (metal ions, vitamins).
Regulation: Allosteric regulation (activation/inhibition), feedback inhibition.
Compartmentalization: Enzymes may be localized within specific cell compartments.