Cell Biology: Molecular Genetics, Cell Division, and Bioenergetics

Comprehensive vocabulary flashcards covering DNA structure and replication, the cell cycle and mitosis, photosynthesis, and cellular respiration.

DNA (Deoxyribonucleic Acid)

A biological macromolecule made of nucleotide monomers that stores and transmits hereditary information and determines which proteins a cell produces.

Nucleotide

The repeating monomer subunit of nucleic acids, consisting of a phosphate group, a 5-carbon sugar (deoxyribose in DNA), and a nitrogenous base.

Sugar-Phosphate Backbone

The structural framework forming the outer sides of the DNA double helix, composed of alternating sugars and phosphate groups linked by covalent bonds.

Antiparallel Strands

The structural arrangement of DNA where the two complementary strands run in opposite directions, with one terminating in a $5'$ phosphate group and the other in a $3'$ hydroxyl ($-\text{OH}$) group.

Semi-Conservative Replication

The mechanism of DNA synthesis occurring during interphase where each newly formed double helix consists of one original template strand and one newly synthesized strand.

DNA Polymerase

The enzyme responsible for synthesizing new DNA strands by joining nucleotides exclusively in the $5'$ to $3'$ direction of the new strand.

Leading Strand

The continuously synthesized DNA strand that elongates toward the replication fork as the parental DNA unwinds.

Lagging Strand

The discontinuously synthesized DNA strand that is built away from the replication fork in short segments called Okazaki fragments.

Okazaki Fragments

Short stretches of newly synthesized DNA nucleotides formed discontinuously along the lagging template strand during replication.

Chromatin

The loosely packed complex of DNA and histone proteins found within the nucleus of a non-dividing eukaryotic cell.

Sister Chromatids

Two identical copies of a replicated chromosome that remain connected at a centromere until anaphase of mitosis.

Centromere

The specialized constricted region of a duplicated chromosome where sister chromatids are joined and where spindle microtubules attach.

Interphase

The preparatory portion of the cell cycle comprising $G_1$, $S$, and $G_2$ phases, during which the cell grows, performs metabolic functions, and replicates its DNA.

Prophase

The first mitotic phase, characterized by the condensation of chromatin into visible chromosomes, breakdown of the nuclear envelope, disappearance of the nucleolus, and movement of centrosomes to form the spindle apparatus.

Metaphase

The mitotic stage where spindle fibers align replicated chromosomes along the metaphase plate in the center of the cell.

Anaphase

The mitotic stage initiated by the splitting of centromeres, allowing sister chromatids to separate into individual chromosomes that are pulled to opposite cell poles.

Telophase

The final stage of mitosis during which daughter chromosomes arrive at poles, decondense back into chromatin, two new nuclear envelopes reform, and spindle fibers disassemble.

Cytokinesis

The physical division of the cytoplasm following mitosis, resulting in two genetically identical, separate daughter cells.

Cleavage Furrow

The shallow groove formed in animal cells during cytokinesis by a contractile ring composed of actin microfilaments and myosin that pinches the cell inward.

Cell Plate

A dividing structure that forms in the middle of a plant cell during cytokinesis and eventually develops into a new cell wall.

Photosynthesis

The biological process in which light energy is converted into chemical energy stored in organic molecules, represented by $6\text{ CO}_2 + 12\text{ H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{ O}_2 + 6\text{ H}_2\text{O}$.

Photoautotrophs

Organisms that utilize sunlight to synthesize organic molecules directly from inorganic substances like carbon dioxide and water.

Heterotrophs

Organisms that cannot produce their own organic food and must obtain nutrients and chemical energy by consuming other organisms.

Thylakoids

Flattened, interconnected membranous sacs within chloroplasts that contain chlorophyll and host the light reactions of photosynthesis.

Stroma

The dense fluid matrix surrounding thylakoids inside the inner membrane of a chloroplast, which houses the enzymes of the Calvin cycle.

Stomata

Microscopic pores on the surface of plant leaves through which carbon dioxide enters and oxygen and water vapor exit.

Chlorophyll a

The primary photosynthetic pigment located in thylakoid membranes that directly absorbs light energy and reflects green wavelengths.

Photophosphorylation

The production of ATP from ADP and inorganic phosphate driven by light-generated proton gradients across the thylakoid membrane during the light reactions.

Calvin Cycle

The light-independent pathway occurring in the chloroplast stroma that uses ATP and NADPH to reduce carbon dioxide into glyceraldehyde 3-phosphate (G3P).

Rubisco

The primary enzyme in the chloroplast stroma that catalyzes carbon fixation by incorporating $\text{CO}_2$ into an organic substrate.

Cellular Respiration

A catabolic pathway in which organic fuels such as glucose are broken down in the presence of oxygen to produce ATP, carbon dioxide, and water: $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{ O}_2 \rightarrow 6\text{ CO}_2 + 6\text{ H}_2\text{O} + \text{Energy}$.

Oxidation

The loss of electrons from a substance during a chemical or redox reaction.

Reduction

The gain or addition of electrons to a chemical substance during a redox reaction.

Phosphorylation

The addition of an inorganic phosphate group to an organic molecule or ADP, which often alters molecular conformation to perform cellular work.

Glycolysis

The initial cytosolic stage of cellular respiration that splits glucose into two pyruvate molecules, yielding a net of $2\text{ ATP}$ and $2\text{ NADH}$.

Alcohol Fermentation

An anaerobic catabolic pathway in which pyruvate is converted to acetaldehyde and then reduced to ethanol and $\text{CO}_2$, regenerating $\text{NAD}^+$ to keep glycolysis functioning.

Lactic Acid Fermentation

An anaerobic metabolic pathway wherein pyruvate is reduced directly by NADH to form lactate without producing $\text{CO}_2$, regenerating $\text{NAD}^+$.

Pyruvate Oxidation

The mitochondrial transition step where pyruvate is converted to acetyl CoA, producing one molecule of $\text{NADH}$ and releasing one molecule of $\text{CO}_2$ per pyruvate.

Citric Acid Cycle (Krebs Cycle)

A cyclic pathway in the mitochondrial matrix that completes the metabolic breakdown of glucose-derived acetyl groups, producing $2\text{ ATP}$, $6\text{ NADH}$, $2\text{ FADH}_2$, and $4\text{ CO}_2$ per glucose molecule.

Cristae

The folds or peninsulas of the inner mitochondrial membrane that project into the matrix and contain thousands of electron transport chain protein complexes.

Electron Transport Chain (ETC)

A sequence of electron carrier molecules embedded in the inner mitochondrial membrane that shuttle electrons down an energy gradient, generating no ATP directly.

Terminal Electron Acceptor

The final molecule in the electron transport chain that captures electrons; in aerobic cellular respiration, oxygen serves this role by binding electrons and protons to form water.

Chemiosmosis

An energy-coupling mechanism that uses energy stored in a proton ($\text{H}^+$) gradient across the inner mitochondrial membrane to drive the synthesis of ATP.

ATP Synthase

A multiprotein transmembrane complex that functions like a turbine, utilizing the flow of protons down their concentration gradient into the matrix to synthesize ATP.

Oxidative Phosphorylation

The production of ATP using energy derived from the redox reactions of the electron transport chain combined with chemiosmosis.