Chapter 1: What Does It Mean to Be Alive?

Key Factors of Life

Biologists define living organisms by several essential characteristics. These factors distinguish living things from non-living matter.

• Cells: The basic unit of life; all organisms are composed of one or more cells.

• Replication / Reproduction: Ability to produce offspring or replicate themselves.

• Information / Genes: Storage and transmission of genetic information (usually in DNA).

• Energy (food): Requirement for energy to drive biological processes.

• Evolution: Populations of organisms change over time through genetic variation and natural selection.

How Do Cells Come to Be?

Three major theories explain the origin and continuity of cells:

• Cell Theory: All organisms are made up of cells or preexisting cells.

• Chromosome Theory: Genetic information is passed through chromosomes; DNA is hereditary material.

• Evolution Theory: Species are related and change over time.

Processing Hereditary Information

Organisms use DNA to store and pass hereditary information. This information is used to grow, develop, and reproduce. Energy is obtained from food, sunlight, or chemicals.

• Central Dogma: Describes the flow of genetic information: DNA → RNA → Protein

• Bases in DNA: Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

Species and Evolution

Species are connected by shared ancestry. Evolution occurs when useful traits are passed down through natural selection, causing species to change over time.

• Tree of Life: Shows how all organisms are related and come from a common ancestor.

• Scientific Process: Involves making observations, asking questions, forming hypotheses, testing with experiments, and drawing conclusions.

Chapter 2: Atomic Structure and Chemical Interactions

Atoms and Bonds

Atoms are composed of protons (+), neutrons, and electrons (–). The way electrons are arranged determines how atoms bond with others, share, or transfer electrons to form molecules.

• Covalent Bonds: Atoms share electrons.

• Ionic Bonds: Atoms transfer electrons, creating charged ions.

• Hydrogen Bonds: Weak attractions between polar molecules, important in water and biological molecules.

Properties of Water

Water is essential for life due to its unique properties:

• Polarity: Water molecules have a partial positive and negative charge, allowing them to form hydrogen bonds.

• Solvent Properties: Water dissolves many substances, regulates temperature, and facilitates chemical reactions.

Chemical Reactions and Energy

• Chemical Reactions: Involve breaking and forming chemical bonds; may absorb or release energy.

• Entropy: Measure of disorder; increases in spontaneous reactions.

Origin of Life: Chemical Evolution

Experiments such as the Miller-Urey experiment show that organic molecules can form from simple gases with energy input (e.g., lightning).

• Organic Molecules: Contain carbon and are the basis of life. Their structure (shape, size, bonds) determines their function.

• Proteins: Build structures and do work.

• Sugars: Store energy.

• Nucleic Acids: Store information (DNA/RNA).

Chapter 3: Proteins and Their Structure

Amino Acids and Polypeptides

Amino acids are the building blocks of proteins. Each amino acid has a central carbon, an amino group, a carboxyl group, and a side chain (R group). Amino acids connect by peptide bonds to form polypeptides.

Levels of Protein Structure

• Primary: Sequence of amino acids.

• Secondary: Folding into alpha helices or beta sheets.

• Tertiary: 3D shape of the whole protein.

• Quaternary: When several polypeptides join together.

The way a protein folds determines its function. Incorrect folding can lead to malfunction or disease.

Protein Functions

• Enzymes: Speed up reactions.

• Antibodies: Defend the body.

• Transport proteins: Move molecules.

• Structural proteins: Provide support.

• Hormones: Send signals.

Chapter 4: Nucleic Acids and Genetic Information

Nucleotides and Nucleic Acids

Nucleotides are the building blocks of DNA and RNA. Each nucleotide contains a sugar, phosphate group, and nitrogenous base. Covalent bonds (sugar-phosphate) link nucleotides to form nucleic acids.

DNA Structure and Function

• Primary: Nucleotide sequence.

• Secondary: Double helix with base pairing (A-T and G-C).

• Tertiary: DNA folds into chromosomes.

These structures allow DNA to store, copy, and pass genetic information.

RNA Structure and Function

• Usually single stranded.

• Primary: Nucleotide sequence.

• Secondary: Folds into shapes (like hairpins).

• Tertiary: 3D forms for function.

RNA can store information, fold like proteins, and help in reactions.

RNA World Hypothesis

Scientists hypothesize that life may have started with RNA because it can both store information and act as an enzyme. RNA could have been the first molecule to carry out life processes.

Additional info:

• DNA base pairing follows specific rules: Adenine pairs with Thymine, and Cytosine pairs with Guanine.

• Proteins are polymers of amino acids; their function depends on their structure.

• Scientific method is essential for biological discovery: observation, hypothesis, experiment, analysis, conclusion.