Photosynthesis, Cell Cycle, and Cellular Reproduction

Vocabulary practice flashcards covering photosynthesis (light-dependent reactions and Calvin cycle), eukaryotic cell cycle phases, checkpoints, cancer genetics, chemotherapy history, and prokaryotic binary fission.

Thylakoid Membrane

The specialized chloroplast membrane where light-dependent reactions take place, converting light energy into chemical energy stored in ATP and NADPH.

Stroma

The fluid-filled region of the chloroplast where the Calvin cycle (light-independent reactions) occurs, utilizing ATP and NADPH to synthesize glucose.

Photosystem II (PS II)

A protein-pigment complex that absorbs sunlight to initiate the light-dependent reactions by splitting water ($H_2O$) into oxygen ($\frac{1}{2}O_2$), protons ($H^+$), and high-energy electrons.

Photosystem I (PS I)

A multiprotein complex that absorbs sunlight to re-energize electrons, facilitating the reduction of $NADP^+$ into the energy-rich carrier NADPH.

ATP Synthase (Photosynthesis)

A membrane-bound enzyme complex through which protons flow from the thylakoid space back into the stroma down their concentration gradient, driving the phosphorylation of ADP and $P_i$ into ATP.

Rubisco

The key enzyme that catalyzes Stage 1 (Carbon Fixation) of the Calvin cycle by attaching three $CO_2$ molecules to ribulose-1,5-bisphosphate (RuBP).

Reduction (Calvin Cycle)

Stage 2 of the Calvin cycle, where chemical energy from 6 ATP and reducing electrons from 6 NADPH are consumed to convert fixed carbon molecules into higher-energy 3-carbon sugars.

RuBP (Ribulose-1,5-bisphosphate)

The 5-carbon acceptor molecule regenerated during Stage 3 of the Calvin cycle using 3 ATP, enabling the continuous fixation of incoming $CO_2$.

$G_1$ Phase (First Gap)

The initial growth stage of interphase characterized by cellular growth, active protein synthesis, preparation for DNA replication, and a terminal restriction checkpoint.

S Phase (Synthesis)

The middle stage of interphase during which DNA replication occurs, leading to the duplication of chromosomes into identical sister chromatids as well as the replication of centrosomes.

$G_2$ Phase (Second Gap)

The final stage of interphase involving continued cell enlargement and protein synthesis specifically dedicated to preparing the cell for mitosis, monitored by a final pre-mitotic checkpoint.

Prometaphase

The mitotic transition stage during which kinetochores appear at centromeres, spindle microtubules attach to kinetochores, and chromosomes begin aligning as centrosomes move to opposite cell poles.

Anaphase

The stage of mitosis where cohesin proteins degrade, allowing sister chromatids to separate and be pulled toward opposite poles while non-kinetochore fibers elongate the cell.

Cleavage Furrow

A shallow contractile ring groove formed during animal cell cytokinesis that constricts the plasma membrane to pinch the parent cell into two separate daughter cells.

Cell Plate

A dividing partition assembled from fusing Golgi vesicles in plant cells during cytokinesis to construct a new internal cell wall between two daughter cells.

$G_0$ Phase

A quiescent, non-dividing phase outside the active cell cycle that cells enter either temporarily or permanently, typical of mature neurons and cardiac muscle cells.

$G_1$ Checkpoint

A cell cycle restriction point assessing cell size, nutrient reserves, and DNA integrity, regulated by molecular components including Cyclin D, CDK4/6, and Rb.

Metaphase (M) Checkpoint

The mitotic spindle checkpoint that verifies proper chromosome alignment along the metaphase plate and secure kinetochore attachment, mediated by APC/C, securin, and separase.

Proto-oncogenes

Normal regulatory genes involved in signal transduction that promote standard cell division, which turn into oncogenes driving excessive cell proliferation when mutated.

RAS Gene Family

A group of proto-oncogenes whose proteins normally toggle between active GTP-bound and inactive GDP-bound states, but when mutated remain constitutively locked 'ON' in the GTP-bound form, stimulating continuous cell proliferation.

Tumor Suppressor Genes

Genes (such as p53, Rb, and BRCA1/2) that prevent abnormal cell proliferation by halting cell division, coordinating DNA repair, and initiating apoptosis; loss of their function can lead to cancer.

p53

A tumor suppressor protein that pauses the cell cycle upon detecting cellular damage (such as DNA lesions or hypoxia) to allow repair, triggering apoptosis if the damage is irreparable.

Lucy Wills

The researcher who discovered folic acid, a nutrient whose uptake inhibition in tumor cells was shown to restrict tumor progression.

Jane C. Wright

The scientist who identified methotrexate as the first chemotherapy drug and established systematic dosage protocols and administration sequences to treat cancer.

Binary Fission

The asexual reproduction method utilized by prokaryotes, where a single circular chromosome replicates starting at the origin of replication, the cell elongates, and the cytoplasm divides.

FtsZ Protein

A bacterial protein (filamenting temperature-sensitive mutant Z) that relies on GTP to assemble a Z-ring at the cell midpoint, recruiting division proteins and serving as an antibiotic target due to its homology to eukaryotic tubulin.

Septum (Binary Fission)

The dividing cross-wall synthesized by plasma membrane and cell wall materials under the direction of the FtsZ ring, culminating in the separation of two prokaryotic daughter cells.