Biology: Key Concepts in Organic Chemistry, Cell Structure, and Cell Cycle

Functional Groups

Specific clusters of atoms attached to carbon skeletons that determine a molecule's chemical behavior.

Hydroxyl Group

-OH; polar, forms hydrogen bonds, increases solubility.

Carbonyl Group

C=O; found in sugars; can be an aldehyde or a ketone.

Carboxyl Group

-COOH; acidic, can donate H⁺.

Amino Group

-NH₂; basic, picks up H⁺.

Sulfhydryl Group

-SH; forms disulfide bridges in proteins.

Phosphate Group

-PO₄²⁻; highly negative, involved in energy transfer (ATP).

Methyl Group

-CH₃; nonpolar, regulates gene expression.

Hydrogen Bonds

Weak bonds between partial positive hydrogen and partial negative oxygen or nitrogen.

Cohesion

The property of water molecules to stick together due to hydrogen bonding.

Water Structure

A water molecule has a bent shape with oxygen as partial negative and hydrogens as partial positive.

Polar Molecule

A molecule with unequal sharing of electrons, resulting in partial charges.

Nonpolar Molecule

A molecule with equal sharing of electrons, lacking partial charges.

Hydrophilic

Substances that dissolve in water, typically polar.

Hydrophobic

Substances that avoid water, typically nonpolar.

Primary Protein Structure

The amino acid sequence of a protein.

Secondary Protein Structure

The folding of the protein into α-helices and β-sheets stabilized by hydrogen bonds.

Tertiary Protein Structure

The three-dimensional folding of a protein involving various bonds and interactions.

Quaternary Protein Structure

The association of multiple polypeptides to form a functional protein.

Transcription

The process of synthesizing mRNA from DNA in the nucleus.

Translation

The process of synthesizing proteins from mRNA at ribosomes.

Codon

A sequence of three nucleotides that codes for an amino acid.

Start Codon

AUG; the codon that signals the start of translation.

Stop Codons

UAA, UAG, UGA; codons that signal the termination of translation.

Fluid-Mosaic Model

Describes the structure of cell membranes as a mosaic of diverse protein molecules embedded in a fluid phospholipid bilayer.

Enzymes

Biological catalysts that lower activation energy and are specific to substrates.

Phospholipid

A molecule with a hydrophilic head and hydrophobic tails, forming the bilayer of cell membranes.

Cytoskeleton

A network of protein filaments and tubules that provides structural support and facilitates movement within the cell.

Mitochondria

Organelles responsible for ATP production via cellular respiration, containing their own DNA.

Glycolysis

The metabolic pathway that converts glucose into pyruvate, producing ATP and NADH, occurring in the cytosol.

Electron Transport Chain (ETC)

A series of protein complexes in the mitochondria that transfer electrons, producing ATP and using oxygen as the final electron acceptor.

Oxidation

The process of losing electrons.

Reduction

The process of gaining electrons.

Fermentation

An anaerobic process that regenerates NAD⁺ and produces lactate or alcohol, yielding low ATP.

Aerobic Respiration

A process that requires oxygen and produces a high yield of ATP (30-32 ATP).

Anaerobic Respiration

A process that does not require oxygen and produces a low yield of ATP (2 ATP).

Cell Cycle

The series of phases that a cell goes through, including interphase and mitosis.

Mitosis

The process of cell division that results in two identical daughter cells.

Cyclins

Regulatory proteins that control the progression of the cell cycle by activating cyclin-dependent kinases (CDKs).

Checkpoint

Control points in the cell cycle that ensure proper division and prevent cancer.

Chromatin

The complex of DNA and proteins found in the nucleus of eukaryotic cells.

Chromosome

Condensed form of chromatin, visible during cell division.

Cytokinesis

The division of the cytoplasm, resulting in two separate daughter cells.