General Biology: Foundations, Chemistry of Life, and Cell Structure

Introduction to Life and Biological Organization

Traits of Living Things

All living organisms share a set of fundamental characteristics that distinguish them from non-living matter.

• Respond to stimuli: Ability to sense and react to environmental changes.

• Made of cells: Composed of one or more cells, the basic unit of life.

• Reproduce: Capable of producing offspring.

• Able to grow and develop: Undergo regulated growth and development.

• Metabolize: Carry out chemical reactions to obtain and use energy.

• Homeostasis: Maintain stable internal conditions.

• Adapt: Evolve over generations in response to the environment.

Domains of Life

All life is classified into three major domains based on cellular organization and genetics.

• Archaea

• Bacteria

• Eukarya

Cell Types and Domains

Archaea and Bacteria: Prokaryotic Cells

Both Archaea and Bacteria are unicellular organisms lacking membrane-bound organelles. Their DNA is free within the cell.

• Archaea: Often found in extreme environments (e.g., hot springs, high salinity, high temperatures).

• Bacteria: Found in a wide variety of environments.

Prokaryotic Cells Overview

• Very simple cell structure.

• Lack a nucleus; DNA is in a single circular chromosome.

• Generally unicellular.

Eukarya: Eukaryotic Cells

• Can be unicellular or multicellular.

• Have membrane-bound organelles, including a nucleus (DNA inside nucleus).

• Divided into kingdoms: protists, fungi, animals, plants.

Eukaryotic Cells Overview

• More complex than prokaryotic cells.

• Contain a nucleus with multiple DNA strands.

The Scientific Method

Steps of the Scientific Method

1. Observation

2. Question

3. Hypothesis

4. Experiment

5. Results

6. Conclusion

Basic Chemistry for Biology

Atoms and Elements

• Atoms: Smallest unit of matter, composed of protons, neutrons, and electrons.

• Protons: Positively charged, located in the nucleus.

• Neutrons: Neutral charge, located in the nucleus.

• Electrons: Negatively charged, located in the electron cloud.

• Atomic number: Number of protons in an atom.

• Mass number: Sum of protons and neutrons in an atom.

• Atomic mass: The atom's total mass.

• Element: Substance that cannot be broken down by chemical reactions.

Isotopes

• Atoms of the same element with different numbers of neutrons (same number of protons).

• Changing the number of protons changes the element; changing neutrons creates isotopes; changing electrons creates ions.

Energy in Atoms

• Energy: Capacity to cause change.

• Potential energy: Energy that matter has due to its position or structure.

• Electrons have more energy the farther they are from the nucleus.

Valence Electrons and Chemical Behavior

• Valence electrons: Electrons in the outermost shell, determine chemical behavior.

• Atoms with full valence shells are inert (nonreactive).

• Common valences: Hydrogen (1), Carbon (4), Nitrogen (3), Oxygen (2).

Bonds

• Covalent bonds: Electrons are shared between atoms to fill valence shells.

• Single, double, and triple bonds refer to the number of electron pairs shared.

• Ionic bonds: Electrons are transferred, creating ions that attract each other.

• Hydrogen bonds: Weak bonds between a hydrogen atom covalently bonded to one atom and attracted to another electronegative atom.

Electronegativity and Bond Polarity

• Electronegativity: Atom's attraction for electrons in a covalent bond.

• Nonpolar covalent bonds: Electrons shared equally.

• Polar covalent bonds: Electrons shared unequally, creating partial charges.

• Ionic bonds: Electrons transferred, forming charged ions.

Water and Life

Properties of Water

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other substances.

• Water expands when frozen.

• Water can make hydrogen bonds.

• Water is a universal solvent, dissolving many substances.

• Hydrophilic: Substances that dissolve in water.

• Hydrophobic: Substances that do not dissolve in water.

Living Matter and Trace Elements

• C, H, O, and N make up 96% of living matter.

• Trace elements (e.g., iron, zinc, cobalt, boron, fluorine) are required in small amounts but are essential for life.

Biological Molecules

Polymers and Monomers

• Monomers: Small, repeating units that make up polymers.

• Polymers: Long molecules consisting of monomers linked by covalent bonds.

• Dehydration reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers by adding water.

7 Biological Chemical Groups

• Hydroxyl Group: –OH, polar, forms hydrogen bonds.

• Carbonyl Group: C=O, found in sugars.

• Carboxyl Group: –COOH, acts as an acid.

• Amino Group: –NH2, acts as a base, part of amino acids.

• Sulfhydryl Group: –SH, forms disulfide bridges in proteins.

• Phosphate Group: –OPO32–, contributes negative charge.

• Methyl Group: –CH3, affects gene expression.

Carbohydrates

• Monosaccharides: Simple sugars, basic unit of carbohydrates.

• Polysaccharides: Long chains of monosaccharides (e.g., cellulose, starch, glycogen).

• Disaccharides: Two monosaccharides joined by glycosidic linkage.

Proteins

• Composed of amino acids linked by peptide bonds.

• Functions: transport, structure, movement, enzymes.

• Primary structure: Linear chain of amino acids.

• Secondary structure: Alpha helices and beta sheets.

• Tertiary structure: 3D shape stabilized by side-chain interactions.

• Quaternary structure: Two or more polypeptides.

Lipids

• Include fats, phospholipids, and steroids.

• Fats: Glycerol + 3 fatty acids (triglycerides), used for energy storage.

• Saturated fats: No double bonds, solid at room temperature.

• Unsaturated fats: Double bonds, liquid at room temperature.

• Phospholipids: Make up cell membranes.

• Steroids: Four fused carbon rings (e.g., cholesterol).

Nucleic Acids

• DNA: Stores genetic information, made of nucleotides.

• RNA: Messenger of genetic information.

• Nucleotide: Building block of DNA and RNA (phosphate, sugar, nitrogenous base).

• Central Dogma: DNA (transcription) → mRNA (translation) → protein.

• Base pairing: A-T, C-G.

Table: Biological Macromolecules and Their Building Blocks

Monomer	Polymer	Bond	Examples
Amino acid	Protein, polypeptide	Peptide	Enzymes
Nucleotide	Nucleic acid	Phosphodiester	DNA, RNA
Monosaccharide	Polysaccharide	Glycosidic	Glucose, glycogen
Fatty acid	Fats, triglyceride, phospholipid	Ester	Fats

Cell Structure and Function

Endomembrane System

• Plasma membrane: Outer boundary, regulates entry/exit of substances.

• Cytoplasm: Region between plasma membrane and nucleus.

• Cytosol: Jelly-like fluid in which organelles are suspended.

• DNA: Genetic material stored in the nucleus (eukaryotes) or nucleoid (prokaryotes).

Organelles and Their Functions

• Nucleus: Contains DNA, site of transcription.

• Endoplasmic Reticulum (ER):

  • Smooth ER: Lipid synthesis, detoxification, no ribosomes.

  • Rough ER: Protein synthesis, has ribosomes.

• Golgi Apparatus: Modifies, sorts, and ships proteins and lipids.

• Lysosomes: Digestive organelles, break down macromolecules.

• Vacuoles: Storage and transport in plant and some animal cells.

• Ribosomes: Protein synthesis; can be free in cytosol or bound to ER.

• Mitochondria: Site of cellular respiration, produces ATP.

• Chloroplasts: Site of photosynthesis in plants and algae.

Modern Cell Theory

1. Organisms are made of cell(s).

2. Cells are the smallest unit of life.

3. All cells come from pre-existing cells.

4. Cells contain genetic information (DNA).

5. All cells have similar structures.

6. Energy flow of life occurs through cells.

Additional info:

• Some context and explanations have been expanded for clarity and completeness.

• Table entries and some definitions have been inferred and elaborated for academic quality.