General Biology: Introduction to Human Biology and Chemistry of Living Things

Lecture 1: Introduction to Human Biology, Science, and Society

Characteristics of Living Organisms

Biologists identify specific characteristics that distinguish living organisms from non-living matter. These features are essential for understanding what defines life.

• Organization: Living things are composed of cells, the basic unit of life.

• Metabolism: All living organisms 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.

• Reproduction: Living things produce offspring, passing genetic information to the next generation.

• Response to Stimuli: Organisms respond to environmental changes.

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

Classification System of Living Organisms

Biologists use classification systems to organize and group living organisms based on shared characteristics.

• Taxonomy: The science of naming, describing, and classifying organisms.

• Hierarchical Levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Binomial Nomenclature: Scientific names use the genus and species (e.g., Homo sapiens).

The Scientific Method

The scientific method is a systematic approach used to investigate natural phenomena and acquire new knowledge.

• Steps:

  1. Observation

  2. Question

  3. Hypothesis

  4. Experiment

  5. Data Collection

  6. Analysis

  7. Conclusion

• Application: Used in daily life to solve problems and make informed decisions.

Dissemination of Scientific Information

Scientific information is shared through various sources, each with different levels of reliability and accessibility.

• Primary Sources: Peer-reviewed journal articles presenting original research.

• Secondary Sources: Reviews, textbooks, and summaries of research.

• Popular Sources: News articles, websites, and media reports.

• Comparison: Primary sources are most reliable; popular sources may lack scientific rigor.

Chapter 2: The Chemistry of Living Things

Basic Terminology and Atomic Structure

Understanding the chemical basis of life requires familiarity with key terms and concepts in chemistry.

• Atom: The smallest unit of matter, composed of protons, neutrons, and electrons.

• Proton: Positively charged particle in the nucleus.

• Neutron: Neutral particle in the nucleus.

• Electron: Negatively charged particle orbiting the nucleus.

• Atomic Number: Number of protons in an atom.

• Atomic Mass: Sum of protons and neutrons.

Periodic Table Interpretation

The periodic table provides information about the elements, including the number of protons, neutrons, and electrons.

• Element Symbol: One- or two-letter abbreviation (e.g., C for carbon).

• Atomic Number: Identifies the element and its number of protons.

• Atomic Mass: Used to calculate the number of neutrons: $\text{Neutrons} = \text{Atomic Mass} - \text{Atomic Number}$

Chemical Bonds

Atoms combine to form molecules through chemical bonds, which determine the properties of compounds.

• Ionic Bond: Transfer of electrons from one atom to another, resulting in charged ions.

• Covalent Bond: Sharing of electron pairs between atoms. Can be polar (unequal sharing) or nonpolar (equal sharing).

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen in water).

• Peptide Bond: Covalent bond linking amino acids in proteins.

Major Elements in the Human Body

The human body is primarily composed of four major elements.

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

Macromolecules and Their Components

Macromolecules are large, complex molecules essential for life. They are built from smaller subunits.

• Carbohydrates: Made of monosaccharides (simple sugars). Examples: glucose, fructose.

• Polysaccharides: Long chains of monosaccharides. Examples: glycogen (animal storage), starch (plant storage).

• Lipids: Include triglycerides (glycerol + 3 fatty acids), phospholipids, and steroids.

• Proteins: Composed of amino acids linked by peptide bonds.

• Nucleic Acids: DNA and RNA, made of nucleotides.

Examples of Polysaccharides

• Glycogen: Storage form of glucose in animals.

• Starch: Storage form of glucose in plants.

Dehydration Synthesis and Hydrolysis

Macromolecules are formed and broken down by specific chemical reactions.

• Dehydration Synthesis: Joining two molecules by removing a water molecule.

• Hydrolysis: Breaking a bond by adding water.

• Example: Formation of a peptide bond between amino acids via dehydration synthesis.

Saturated vs. Unsaturated Fatty Acids

Fatty acids differ in their chemical structure, affecting their physical properties and health implications.

• Saturated Fatty Acids: No double bonds between carbon atoms; solid at room temperature.

• Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature.

• Health Impact: Unsaturated fats are generally considered healthier than saturated fats.

Table: Comparison of Macromolecules and Their Components

Macromolecule	Monomer	Example	Function
Carbohydrate	Monosaccharide	Glucose, Starch, Glycogen	Energy storage, structure
Lipid	Fatty acid, Glycerol	Triglyceride	Energy storage, insulation
Protein	Amino acid	Enzymes, Hemoglobin	Catalysis, transport, structure
Nucleic Acid	Nucleotide	DNA, RNA	Genetic information

Peptide Bonds in Proteins

A peptide bond is a covalent bond formed between two amino acids during protein synthesis.

• Formation: Occurs via dehydration synthesis, releasing a water molecule.

• Structure: Links the carboxyl group of one amino acid to the amino group of another.

Hydrogen Bonding in Biological Molecules

Hydrogen bonds play a crucial role in the structure and function of biological molecules.

• Water Molecules: Hydrogen bonds give water its unique properties (e.g., high boiling point, cohesion).

• Proteins and DNA: Hydrogen bonds stabilize secondary and tertiary structures.

Reactants, Substrates, and Products in Chemical Reactions

Chemical reactions in biology involve the transformation of reactants (substrates) into products.

• Reactant (Substrate): Substance that undergoes change during a reaction.

• Product: Substance formed as a result of the reaction.

• Example: In cellular respiration, glucose (reactant) is converted to carbon dioxide and water (products).

Isomers

Isomers are molecules with the same chemical formula but different structural arrangements.

• Example: Glucose and fructose are isomers (both C6H12O6).

Summary Equation Example

General equation for dehydration synthesis:

• $\text{Monomer}_1 + \text{Monomer}_2 \rightarrow \text{Polymer} + \text{H}_2\text{O}$

Additional info: Some terminology and examples were expanded for clarity and completeness, including the table comparing macromolecules and the summary equation for dehydration synthesis.