General Biology: Key Concepts and Study Guide

Study Guide - Smart Notes

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This section introduces the fundamental properties of life and the scientific methods used in biological research.

Properties of Life: Living organisms share characteristics such as organization, metabolism, growth, adaptation, response to stimuli, and reproduction.
Scientific Investigations: Biologists use the scientific method, which involves observation, hypothesis formation, experimentation, and analysis to understand biological phenomena.
Evidence-Based Reasoning: Conclusions in biology are drawn from systematic observation and experimental evidence.

This section covers the structure of atoms, the nature of chemical bonds, and the importance of molecules in biology.

Structure of an Atom: Atoms consist of a nucleus (protons and neutrons) and electrons in orbitals.
Elements: Pure substances consisting of only one type of atom; essential elements for life include carbon, hydrogen, oxygen, and nitrogen.
Chemical Bonds: Atoms form molecules via covalent (sharing electrons), ionic (transfer of electrons), and hydrogen bonds (attraction between polar molecules).
Compounds: Substances formed from two or more different elements bonded together.
Macromolecules: Large molecules such as proteins, nucleic acids, carbohydrates, and lipids are built from smaller subunits (monomers).

Proteins are essential macromolecules with diverse functions, determined by their structure and chemical properties.

Amino Acids: Building blocks of proteins; their solubility and interaction depend on side chain properties.
Levels of Protein Structure:
- Primary: Sequence of amino acids.
- Secondary: Local folding (α-helix, β-sheet) stabilized by hydrogen bonds.
- Tertiary: Overall 3D shape due to side chain interactions.
- Quaternary: Association of multiple polypeptide chains.
Protein Folding and Denaturation: Proper folding is crucial for function; denaturation (unfolding) leads to loss of function.
Protein Functions: Enzymes, structural support, transport, signaling, and immune response.

Carbohydrates are organic molecules that serve as energy sources and structural components in cells.

Monosaccharides: Simple sugars (e.g., glucose, fructose) with structural variations.
Polysaccharides: Long chains of monosaccharides; storage (starch, glycogen) and structural (cellulose, chitin) roles.
Structure-Function Relationship: The structure of carbohydrates determines their function in energy storage, cell structure, and recognition.

Lipids are hydrophobic molecules important for energy storage, membrane structure, and signaling.

Major Types of Lipids: Fats (triglycerides), steroids, phospholipids.
Phospholipids: Amphipathic molecules forming the bilayer of cell membranes; spontaneous formation in water due to hydrophobic and hydrophilic regions.
Biological Molecules: Four main categories: carbohydrates, lipids, proteins, nucleic acids.
Water Properties: Polarity, hydrogen bonding, high specific heat, cohesion, adhesion, and solvent abilities.
Fatty Acids: Saturated (no double bonds), unsaturated (one or more double bonds); influence membrane fluidity and function.
Cholesterol: Modifies membrane fluidity and is a precursor for steroid hormones.

Cell membranes regulate the movement of substances and maintain cellular homeostasis.

Osmosis: Diffusion of water across a selectively permeable membrane.
Passive Transport: Movement of substances down their concentration gradient without energy input (includes simple and facilitated diffusion).
Active Transport: Movement of substances against their concentration gradient, requiring energy (usually ATP).
Carrier Proteins: Facilitate transport of specific molecules across membranes.
Sodium-Potassium Pump: Uses ATP to move Na+ out and K+ into the cell, establishing an electrochemical gradient.

Comparison of Passive and Active Transport

Feature	Passive Transport	Active Transport
Energy Requirement	No	Yes (ATP)
Direction	Down concentration gradient	Against concentration gradient
Examples	Osmosis, simple diffusion, facilitated diffusion	Sodium-potassium pump, proton pump

Key Equation: Sodium-Potassium Pump

The sodium-potassium pump hydrolyzes ATP to transport ions: