Comprehensive Biology 181 Study Notes: Fundamentals of Life, Cell Theory, and Biological Chemistry

Biology

The scientific study of life and living organisms.

Cell

The smallest, membrane-bound functional unit capable of performing chemical reactions required to grow, function, and reproduce.

Mitosis

A cellular division mechanism producing identical somatic daughter cells.

Meiosis

A cellular division mechanism producing haploid gametic cells for sexual reproduction.

Central Dogma of Molecular Biology

The directional pathway of genetic information flow universal to living organisms: $\text{DNA} \rightarrow \text{mRNA} \rightarrow \text{Protein}$.

Last Universal Common Ancestor (LUCA)

The common ancestor from which all biological classification stems, originating approximately $3.8\text{ billion years ago}$.

Prokaryotic Cells

Small, structurally simple single-celled organisms in domains Bacteria and Archaea that lack major membrane-bound organelles or an enclosed nucleus.

Eukaryotic Cells

Complex organisms in domain Eukarya featuring prominent membrane-bound organelles, including a true nucleus.

Ribosomes

Non-membrane-bound macromolecular structures that catalyze protein synthesis by translating mRNA sequences.

Mitochondria

Double-membrane eukaryotic organelles responsible for cellular respiration and ATP energy generation.

Chloroplast

Photosynthetic organelles in plant cells and protists containing $2\text{ to }3$ membranes that convert light energy into chemical energy.

Organelle Compartmentalization

The physical separation of biological reactions within eukaryotic membrane-bound organelles to protect molecules, isolate incompatible pathways, and optimize reaction rates.

Semiautonomous Organelles

Organelles such as mitochondria and chloroplasts that contain their own circular DNA, specialized ribosomes, and divide independently within the cell.

Surface Area to Volume Ratio ($SA:V$)

A physical restriction on cell size where volumetric growth outpaces surface area expansion, requiring cells to remain small to maintain efficient chemical exchange.

Atomic Number

The total number of protons contained within the nucleus of an atom, defining the identity of a chemical element.

Mass Number

The total sum of protons and neutrons present within an atom's nucleus.

Isotopes

Variants of a single element containing identical proton counts (atomic number) but differing neutron counts (mass number).

Ionic Bond

A chemical bond formed by the complete transfer of valence electrons between atoms, resulting in electrostatic attraction between oppositely charged ions.

Nonpolar Covalent Bond

A chemical bond formed when valence electrons are shared equally between two nuclei with identical or near-identical electronegativities.

Polar Covalent Bond

A chemical bond formed when valence electrons are shared unequally between atoms with different electronegativities, generating partial electrical charges.

Electronegativity

The quantitative pull or inherent ability of an atom to attract shared electrons toward itself within a chemical bond.

Hydrogen Bond

A weak non-covalent attraction between a partial positive charge $\delta^+$ on a hydrogen atom in a polar bond and a partial negative charge $\delta^-$ on an electronegative atom ($O$ or $N$).

Amphipathic

Describing molecules that possess both distinct hydrophilic (polar/charged) and hydrophobic (nonpolar) regions, such as phospholipids.

Dehydration Synthesis

A biochemical condensation reaction that forms a covalent bond between monomers while releasing a water molecule ($-H_2O$).

Hydrolysis

A biochemical reaction that breaks covalent bonds in polymers into individual monomers by consuming a water molecule ($+H_2O$).

Biology

The scientific study of life and living organisms.

Cell

The smallest, membrane-bound functional unit capable of performing chemical reactions required to grow, function, and reproduce.

Mitosis

A cellular division mechanism producing identical somatic daughter cells.

Meiosis

A cellular division mechanism producing haploid gametic cells for sexual reproduction.

Central Dogma of Molecular Biology

The directional pathway of genetic information flow universal to living organisms: $\text{DNA} \rightarrow \text{mRNA} \rightarrow \text{Protein}$.

Last Universal Common Ancestor (LUCA)

The common ancestor from which all biological classification stems, originating approximately $3.8\text{ billion years ago}$.

Prokaryotic Cells

Small, structurally simple single-celled organisms in domains Bacteria and Archaea that lack major membrane-bound organelles or an enclosed nucleus.

Eukaryotic Cells

Complex organisms in domain Eukarya featuring prominent membrane-bound organelles, including a true nucleus.

Ribosomes

Non-membrane-bound macromolecular structures that catalyze protein synthesis by translating mRNA sequences.

Mitochondria

Double-membrane eukaryotic organelles responsible for cellular respiration and ATP energy generation.

Chloroplast

Photosynthetic organelles in plant cells and protists containing $2\text{ to }3$ membranes that convert light energy into chemical energy.

Organelle Compartmentalization

The physical separation of biological reactions within eukaryotic membrane-bound organelles to protect molecules, isolate incompatible pathways, and optimize reaction rates.

Semiautonomous Organelles

Organelles such as mitochondria and chloroplasts that contain their own circular DNA, specialized ribosomes, and divide independently within the cell.

Surface Area to Volume Ratio ($SA:V$)

A physical restriction on cell size where volumetric growth outpaces surface area expansion, requiring cells to remain small to maintain efficient chemical exchange.

Atomic Number

The total number of protons contained within the nucleus of an atom, defining the identity of a chemical element.

Mass Number

The total sum of protons and neutrons present within an atom's nucleus.

Isotopes

Variants of a single element containing identical proton counts (atomic number) but differing neutron counts (mass number).

Ionic Bond

A chemical bond formed by the complete transfer of valence electrons between atoms, resulting in electrostatic attraction between oppositely charged ions.

Nonpolar Covalent Bond

A chemical bond formed when valence electrons are shared equally between two nuclei with identical or near-identical electronegativities.

Polar Covalent Bond

A chemical bond formed when valence electrons are shared unequally between atoms with different electronegativities, generating partial electrical charges.

Electronegativity

The quantitative pull or inherent ability of an atom to attract shared electrons toward itself within a chemical bond.

Hydrogen Bond

A weak non-covalent attraction between a partial positive charge $\delta^+$ on a hydrogen atom in a polar bond and a partial negative charge $\delta^-$ on an electronegative atom ($O$ or $N$).

Amphipathic

Describing molecules that possess both distinct hydrophilic (polar/charged) and hydrophobic (nonpolar) regions, such as phospholipids.

Dehydration Synthesis

A biochemical condensation reaction that forms a covalent bond between monomers while releasing a water molecule ($-H_2O$).

Hydrolysis

A biochemical reaction that breaks covalent bonds in polymers into individual monomers by consuming a water molecule ($+H_2O$).