General Biology Study Guide: Introduction to Life, Chemistry of Life, Macromolecules, and Cell Structure

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Chapter 1: Introduction to Life on Earth

Characteristics of Life

Living organisms share several key characteristics that distinguish them from non-living matter. Understanding these traits is fundamental to biology.

Complex, organized structure: Living things are highly organized, often composed of one or more cells.
Ability to acquire material and energy: Organisms obtain energy and materials from their environment and transform them for growth and maintenance.
Ability to maintain internal stability (homeostasis): Organisms regulate their internal environment to maintain stable conditions necessary for life.
Response to stimuli: Living things can detect and respond to changes in their environment.
Growth: Organisms increase in size and/or number of cells.
Reproduction: Organisms produce offspring, either sexually or asexually. DNA serves as the genetic blueprint for inheritance.
Ability to evolve: Populations of organisms change over time through evolution, adapting to their environment.

Levels of Biological Organization

Biological systems are organized in a hierarchy from smallest to largest:

Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ systems → Organisms → Populations → Communities → Ecosystems → Biosphere

Autotrophs vs. Heterotrophs

Autotrophs: Organisms that produce their own food (e.g., plants via photosynthesis).
Heterotrophs: Organisms that obtain food by consuming other organisms.

Domains of Life

All living organisms are classified into three domains:

Bacteria
Archaea
Eukarya

Binomial Nomenclature

This system uses two names (genus and species) to give each organism a scientific name, e.g., Homo sapiens.

Scientific Method and Scientific Theory

Hypothesis: An educated guess based on prior knowledge and observation.
Scientific theory: A well-substantiated explanation of some aspect of the natural world, based on a body of evidence.

Chapter 2: Atoms, Molecules, and Life

Structure of Atoms

Atoms are the basic units of matter, composed of protons, neutrons, and electrons.

Protons: Positively charged particles in the nucleus.
Neutrons: Neutral particles in the nucleus.
Electrons: Negatively charged particles orbiting the nucleus.

Chemical Bonds

Ionic bonds: Formed by the transfer of electrons between atoms.
Covalent bonds: Formed by the sharing of electrons between atoms.
Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., oxygen or nitrogen).

Properties of Water

Universal solvent: Water's polarity allows it to dissolve many substances.
High specific heat: Water resists temperature changes due to hydrogen bonding.
Floating ice: Ice floats because it is less dense than liquid water, insulating aquatic life below.

pH Scale

The pH scale measures the concentration of hydrogen ions () in a solution.

As increases, pH decreases.
pH scale ranges from 0 (acidic) to 14 (basic).

Buffers

Buffers help maintain a stable pH in biological systems by accepting or donating hydrogen ions.

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons. Some isotopes are used in biological applications, such as cancer treatment.

Chapter 3: Macromolecules

Organic Molecules

Organic molecules are carbon-based and include carbohydrates, lipids, proteins, and nucleic acids.

Macromolecules and Their Functions

Carbohydrates: Energy storage and structural support.
Lipids: Energy storage, insulation, and cell membrane structure.
Proteins: Enzymes, structural components, transport, and signaling.
Nucleic acids: Store and transmit genetic information.

Monomers and Polymers

Monomers: Building blocks of macromolecules (e.g., amino acids, monosaccharides, nucleotides).
Polymers: Chains of monomers (e.g., proteins, polysaccharides, DNA).

Dehydration Synthesis and Hydrolysis

Dehydration synthesis: Joins monomers by removing water.
Hydrolysis: Breaks polymers into monomers by adding water.

Protein Structure

Proteins have four levels of structure:

Primary structure: Sequence of amino acids.
Secondary structure: Regular folding patterns (alpha helices, beta sheets) stabilized by hydrogen bonds.
Tertiary structure: Overall 3D shape due to interactions among R groups.
Quaternary structure: Association of multiple polypeptide chains.

Saturated vs. Unsaturated Fats

Saturated	Unsaturated
No double bonds between carbons	One or more double bonds between carbons
Usually solid at room temperature	Usually liquid at room temperature

ATP

ATP (adenosine triphosphate) is the main energy source for cellular processes.

Chapter 4: Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells

Prokaryotes	Eukaryotes
No nucleus or nuclear envelope	Nucleus with nuclear envelope
DNA in a "nucleoid region"	DNA within the nucleus

Plasma Membrane Functions

Isolates the cell's internal contents from the external environment
Regulates the flow of materials into and out of the cell
Allows communication with other cells

Endomembrane System

Nuclear envelope
Endoplasmic reticulum (rough and smooth)
Golgi apparatus
Lysosomes
Vacuoles

Protein Secretion Pathway

Newly synthesized protein moves through the ER membrane into the ER.
Protein is pinched off the ER and travels to the Golgi apparatus in a vesicle.
Vesicle carries the protein to the plasma membrane for export.

Cytoskeleton

The cytoskeleton is a network of protein fibers and filaments that provide structural support and facilitate movement within the cell.

Plasmids

Plasmids are small rings of DNA found in prokaryotes, often carrying genes for antibiotic resistance.

Organelles with Their Own DNA

Mitochondria: Site of cellular respiration; produce ATP.
Chloroplasts: Site of photosynthesis in plants and algae.

Both organelles can grow and reproduce independently within the cell.

Nucleolus

The nucleolus is a region within the nucleus where ribosomal RNA is synthesized and ribosome assembly begins.

Difference Between Mitochondria and Chloroplasts

Mitochondria: Convert chemical energy from food into ATP via cellular respiration.
Chloroplasts: Convert light energy into chemical energy (sugars) via photosynthesis.