General Biology: Core Concepts and Study Guide

Chapter 1: The Study of Life

1. Characteristics of Life

Biologists use several criteria to determine if something is alive. These characteristics help distinguish living organisms from non-living matter.

• Organization: Living things are composed of one or more cells, which are considered the basic units of life.

• Metabolism: All living things carry out chemical reactions to obtain and use energy.

• Homeostasis: The ability to maintain a stable internal environment.

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Response to Stimuli: Living things respond to environmental changes.

• Reproduction: The ability to produce new organisms, either sexually or asexually.

• Evolutionary Adaptation: Populations of living things evolve over generations.

2. Emergent Properties and Biological Hierarchy

Emergent properties are new attributes that arise at each level of biological organization, resulting from the interactions among components at the lower levels.

• Biological Hierarchy: Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

• Example: A single neuron cannot think, but a network of neurons (the brain) can produce thought.

3. Domains of Life

All living organisms are classified into three domains based on cellular organization and genetics.

• Bacteria: Prokaryotic, unicellular organisms.

• Archaea: Prokaryotic, often found in extreme environments.

• Eukarya: Eukaryotic cells, includes protists, fungi, plants, and animals.

4. Information Transfer in Biological Systems

Information is transferred within and between biological systems through genetic material and signaling molecules.

• DNA: The molecule that stores genetic information.

• Gene Expression: The process by which information from a gene is used to synthesize a functional gene product (usually a protein).

5. Structure and Function in Biology

The structure of biological molecules and systems is closely related to their function.

• Example: The shape of an enzyme's active site allows it to bind specifically to its substrate.

6. Interactions in Biological Systems

Biological systems interact at multiple levels, from molecules to ecosystems.

• Example: Predator-prey relationships in an ecosystem.

Energy flows through ecosystems, while matter cycles within them.

• Producers: Organisms (like plants) that convert solar energy into chemical energy.

• Consumers: Organisms that eat other organisms for energy.

• Decomposers: Organisms that break down dead matter, recycling nutrients.

• Ultimate Source of Energy: The sun.

8. Natural Selection and Evolution

Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring.

• Evolution: The change in the genetic composition of a population over time.

• Example: The development of antibiotic resistance in bacteria.

Chapter 2: Chemistry of Life

1. Phases of Matter

Matter exists in three primary states: solid, liquid, and gas. Each state is defined by the arrangement and movement of its particles.

2. Compounds and Elements

Elements are pure substances consisting of only one type of atom.

Compounds are substances formed from two or more elements chemically combined in fixed ratios.

• Example: Water (H2O) is a compound made from hydrogen and oxygen.

3. Elements in the Human Body

The most prevalent elements in the human body are:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

4. Atomic Structure

Atoms consist of protons, neutrons, and electrons.

• Atomic Number: Number of protons in the nucleus.

• Atomic Mass: Sum of protons and neutrons.

5. Isotopes

Isotopes are atoms of the same element with different numbers of neutrons.

• Radioactive Isotopes: Unstable isotopes that decay over time, releasing radiation. Used in medical imaging.

6. Chemical Bonds

Atoms combine through chemical bonds to form molecules.

• Ionic Bonds: Transfer of electrons from one atom to another.

• Covalent Bonds: Sharing of electrons between atoms.

• Polar Covalent Bonds: Unequal sharing of electrons.

• Non-polar Covalent Bonds: Equal sharing of electrons.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (like oxygen or nitrogen).

7. Water and Its Properties

Water is essential for life due to its unique properties, many of which arise from hydrogen bonding.

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water can absorb a lot of heat before changing temperature.

• Solvent Properties: Water dissolves many substances.

8. Acids, Bases, and pH

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

• Acid: Substance that increases H+ concentration (pH < 7).

• Base: Substance that decreases H+ concentration (pH > 7).

• Neutral: pH = 7.

Equation:

$\text{pH} = -\log_{10}[\text{H}^+]$

9. Buffers

Buffers are substances that minimize changes in pH by accepting or donating H+ ions.

Chapter 3: Biological Macromolecules

1. Carbon Chemistry and Biological Diversity

Carbon's ability to form four covalent bonds makes it the backbone of organic molecules, leading to a vast diversity of biological compounds.

2. Hydrocarbon Skeletons

Hydrocarbon skeletons can vary in length, branching, and ring structure, contributing to molecular diversity.

3. Isomers

Isomers are molecules with the same molecular formula but different structures and properties.

• Structural Isomers: Differ in covalent arrangement.

• Cis-trans Isomers: Differ in spatial arrangement around double bonds.

• Enantiomers: Mirror images of each other.

4. Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties.

• Hydroxyl (-OH)

• Carbonyl (C=O)

• Carboxyl (-COOH)

• Amino (-NH2)

• Phosphate (-PO4)

5. Macromolecules

Macromolecules are large molecules essential for life, including carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Sugars and starches, energy storage and structure.

• Lipids: Fats, oils, phospholipids, and steroids, important for membranes and energy storage.

• Proteins: Polymers of amino acids, perform a wide range of functions.

• Nucleic Acids: DNA and RNA, store and transmit genetic information.

6. Dehydration and Hydrolysis Reactions

Macromolecules are built by dehydration synthesis (removal of water) and broken down by hydrolysis (addition of water).

7. Protein Structure

Proteins have four levels of structure:

• Primary: Sequence of amino acids.

• Secondary: Local folding (alpha helices, beta sheets).

• Tertiary: Overall 3D shape.

• Quaternary: Association of multiple polypeptides.

8. Enzyme Function

Enzymes are proteins that catalyze biochemical reactions, lowering activation energy and increasing reaction rates.

9. Lactose Tolerance

Lactose tolerance in some human populations is due to the continued production of the enzyme lactase into adulthood, an example of human evolution and adaptation.

Table: Comparison of Bond Types

Bond Type	Description	Strength	Example
Ionic	Transfer of electrons	Strong (in dry conditions)	NaCl
Covalent	Sharing of electrons	Very strong	H2O
Hydrogen	Attraction between H and electronegative atom	Weak	Between water molecules