General Biology: Cell Energetics, Cell Division, and Genetics

Vocabulary practice flashcards covering photosynthesis, cellular respiration, the eukaryotic cell cycle, mitosis, meiosis, and Mendelian genetics.

Photosynthesis

The metabolic process of synthesizing organic molecules from inorganic molecules using light energy, performed by plants, algae, and cyanobacteria.

Chloroplast

A specialized membrane-bound organelle that carries out photosynthesis in plants and many protists.

Thylakoid Membrane

The internal membrane system of the chloroplast where chlorophyll and other pigments absorb solar energy to drive the light reactions.

Stroma

The semifluid matrix surrounding the thylakoid membranes in a chloroplast where the Calvin cycle reactions build sugars such as glucose.

Light Reactions

The stage of photosynthesis occurring in the thylakoid membrane where absorbed light energy is transferred to ATP and NADPH while water is split, releasing $O_2$.

Photolysis

The light-driven splitting of water molecules in photosystem II into oxygen and hydrogen ions ($H^+$), which supplies replacement electrons and releases $O_2$.

Chlorophyll

The primary photosynthetic pigment in plants that absorbs violet and red light within the $380\text{--}750\text{ nm}$ range while reflecting green light.

Carotenoids

Accessory photosynthetic pigments that absorb green and blue light while reflecting yellow to orange wavelengths, becoming visible in autumn when chlorophyll degrades.

Carbon Dioxide Fixation

The first step of the Calvin cycle in which an enzyme attaches $CO_2$ to RuBP to form an unstable 6-carbon molecule that promptly splits into two molecules of 3PG.

Carbon Dioxide Reduction

The second step of the Calvin cycle where 3PG is converted into G3P using electrons from NADPH and energy from ATP.

G3P (Glyceraldehyde-3-Phosphate)

The 3-carbon carbohydrate end product of the Calvin cycle that photosynthesizers can use to form glucose, sucrose, starch, cellulose, fatty acids, and amino acids.

RuBP (Ribulose 1,5-Bisphosphate)

The 5-carbon starting molecule of the Calvin cycle that fixes carbon dioxide and is regenerated using G3P and ATP.

Cellular Respiration

An aerobic process that consumes oxygen to break down glucose into carbon dioxide and water, releasing energy stored as ATP ($C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{energy}$).

Oxidation

A chemical reaction defined by the removal of hydrogen atoms and the loss of electrons from a molecule.

Reduction

A chemical reaction defined by the addition of hydrogen atoms and the gain of electrons by a molecule.

Glycolysis

The first phase of cellular respiration occurring in the cytoplasm of prokaryotes and eukaryotes, which breaks one 6-carbon glucose into two 3-carbon pyruvates.

Energy-Investment Steps

The initial reactions of glycolysis where $2\text{ ATP}$ transfer phosphate groups to glucose to activate it for subsequent cleavage.

Energy-Harvesting Steps

The terminal reactions of glycolysis where substrate-level ATP synthesis produces $4\text{ ATP}$ (yielding a net gain of $2\text{ ATP}$) and $2\text{ NADH}$.

Preparatory Reaction

The mitochondrial matrix stage where pyruvate is oxidized into acetyl-CoA, producing $2\text{ NADH}$ and giving off $2\text{ }CO_2$ per glucose molecule.

Citric Acid Cycle (Krebs Cycle)

The cyclical metabolic pathway in the mitochondrial matrix that turns twice per glucose, converting two acetyl groups into $4\text{ }CO_2$, $2\text{ ATP}$, $6\text{ NADH}$, and $2\text{ FADH}_2$.

Cristae

The invaginated folds of the inner mitochondrial membrane that house the electron transport chain and ATP synthase complexes.

Electron Transport Chain (Aerobic Respiration)

A series of membrane carriers in the cristae that accept electrons from NADH and $FADH_2$, using the released energy to pump $H^+$ and generate an electrochemical gradient.

Oxygen (in Aerobic Respiration)

The terminal electron acceptor in the mitochondrial electron transport chain that combines with electrons and hydrogen ions to produce water.

Chromatin

Thin, uncoiled threads of eukaryotic genomic DNA complexed with histone proteins present in the nucleus during interphase.

Nucleosome

A structural repeating unit of chromatin consisting of a length of DNA coiled around a core of histone proteins.

Sister Chromatids

Two identical copies of a duplicated chromosome joined together at a shared centromere before being separated during cell division.

Centromere

The constricted chromosome region where sister chromatids are held together and where spindle fibers attach during division.

Cell Cycle

An orderly repeating sequence of events consisting of interphase ($G_1$, $S$, $G_2$) and the mitotic ($M$) stage that produces two daughter cells.

Interphase

The non-dividing phase of the cell cycle comprising $G_1$ (growth and organelle doubling), $S$ (DNA replication), and $G_2$ (synthesis of proteins for division).

Mitosis

Eukaryotic nuclear division that allocates identical copies of parent chromosomes into two new nuclei, preserving the chromosome number.

Prophase

The first stage of mitosis in which chromatin condenses into visible chromosomes, the nuclear envelope disperses, and the bipolar spindle forms.

Metaphase

The mitotic stage during which duplicated chromosomes align along the spindle equator midway between the two centrosome poles.

Anaphase

The stage of mitosis where sister chromatids separate at their centromeres and are drawn by spindle microtubules to opposite poles as daughter chromosomes.

Telophase

The final stage of mitosis during which daughter chromosomes reach the spindle poles, uncoil, and are enclosed within newly forming nuclear envelopes.

Cleavage Furrow

A shallow groove that forms in the plasma membrane of dividing animal cells as a contractile ring of actin microfilaments constricts to pinch the cytoplasm in two.

Cell Plate

A membrane-bound structure assembled from fusing Golgi-derived vesicles along the equatorial plane of a dividing plant cell that develops into a new cell wall.

Contact Inhibition

A cell cycle regulatory mechanism where normal animal cells cease dividing once they make physical contact with surrounding cells in culture.

Telomeres

Repetitive DNA sequences situated at the ends of eukaryotic chromosomes that protect tips from degradation and shorten with each round of cell division.

Apoptosis

Genetically programmed cell death characterized by chromatin condensation, cell rounding, nuclear collapse, and plasma membrane blistering into blebs.

Metastasis

The dissemination of malignant cancer cells from an original tumor site into bloodstream or lymphatic vessels to establish secondary tumors elsewhere in the body.

Meiosis

A specialized two-stage nuclear division in sexually reproducing organisms that reduces the chromosome number from diploid ($2n$) to haploid ($n$) to form gametes.

Homologous Chromosomes

A pair of chromosomes carrying alleles for the same traits at identical loci, possessing matching size, length, and centromere location.

Diploid ($2n$)

A condition in which a cell contains two homologous sets of chromosomes ($2n = 46$ in humans), typical of somatic cells.

Haploid ($n$)

A condition in which a cell contains only one set of chromosomes ($n = 23$ in humans), characteristic of gametes such as sperm and eggs.

Zygote

The diploid cell produced by the fertilization of a haploid female egg by a haploid male sperm.

Synapsis

The precise pairing and physical alignment of homologous chromosome pairs that occurs during prophase I of meiosis.

Crossing-Over

The reciprocal exchange of corresponding genetic segments between nonsister chromatids of homologous chromosomes during synapsis in prophase I.

Nondisjunction

The abnormal failure of homologous chromosomes to separate during meiosis I, or sister chromatids during meiosis II, causing aneuploid gametes.

Down Syndrome

A human chromosomal disorder caused by trisomy 21, resulting from an extra copy of chromosome 21 produced through nondisjunction.

Klinefelter Syndrome

A genetic condition in sterile males caused by an extra X chromosome ($\text{XXY}$), resulting in feminized physical traits and diminished mental capacity.

Turner Syndrome

A genetic condition in females caused by monosomy X ($\text{XO}$), resulting in sterility, short stature, and a characteristic webbed neck.

Gene

A heritable unit of information located at a specific chromosomal locus that encodes instructions for a biological trait (originally called elementen by Mendel).

Allele

One of two or more alternative molecular forms of a gene located at the same locus on homologous chromosomes.

Homozygous

The genetic condition of possessing two identical alleles at a given gene locus ($AA$ or $aa$).

Heterozygous

The genetic condition of possessing two different alleles at a given gene locus ($Aa$).

Dominant Allele

An allele that masks the phenotypic expression of a recessive allele when present together in a heterozygous state.

Recessive Allele

An allele whose phenotypic expression is masked in the presence of a dominant allele and is expressed only when homozygous.

Genotype

The specific allelic composition or genetic makeup of an individual organism.

Phenotype

The observable physical, biochemical, or physiological characteristics of an organism produced by its genotype and environment.

Law of Segregation

Mendel's first law stating that diploid individuals possess two alleles for each trait, which separate during meiosis so each gamete carries only one allele.

Law of Independent Assortment

Mendel's second law stating that allele pairs for different traits segregate independently of one another during gamete formation, resulting in a $9:3:3:1$ dihybrid phenotypic ratio.

Punnett Square

A diagrammatic grid invented by Reginald Punnett used to calculate and display the statistical probabilities of offspring genotypes and phenotypes.

Incomplete Dominance

A pattern of inheritance where the heterozygous phenotype is an intermediate blend between the phenotypes of the two homozygous parents (e.g., pink snapdragons).

Codominance

A pattern of inheritance where two nonidentical alleles of a gene are fully and simultaneously expressed in heterozygotes, such as in AB blood type.

Polygenic Inheritance

A pattern of inheritance wherein a continuous phenotypic trait is governed by the additive interaction of multiple independent gene loci, resulting in a bell-shaped distribution.

Pleiotropy

A genetic condition in which a single mutant gene exerts multiple distinct and seemingly unrelated phenotypic effects throughout the body (e.g., Marfan syndrome).