Cell Cycle, Signaling, Photosynthesis & Respiration – Master Vocabulary

Vocabulary flashcards covering key terms from the lecture on cell division, cell signaling, photosynthesis, and cellular respiration. Use them to reinforce definitions and conceptual understanding before your exam.

Genome

The complete genetic information of a cell or organism.

Chromosome

DNA wrapped around proteins; the visible ‘package’ for genetic material during mitosis.

Somatic Cell

Any body cell other than a reproductive (gamete) cell.

Gamete

A reproductive cell (sperm or egg) containing half the organism’s chromosomes.

Chromatin

DNA-protein complex that forms chromosomes; diffuse in interphase.

Nucleosome

DNA wound around an octet of histones; basic unit of chromatin packing.

Prokaryotic DNA

Single, circular DNA molecule found in bacteria and archaea.

Histone

Positively charged protein that helps package eukaryotic DNA.

Scaffolding Protein

Non-histone protein maintaining overall chromosome structure.

Centrosome

Microtubule-organizing center and origin of the mitotic spindle.

Centriole

Triplet-microtubule cylinder inside animal centrosomes (absent in plants).

Aster

Radial array of short microtubules extending from each centrosome during mitosis.

Sister Chromatids

Identical copies of a duplicated chromosome joined at the centromere.

Centromere

Specialized DNA sequence where sister chromatids are most closely attached.

Interphase

G1, S, and G2 phases; cell growth, DNA replication, preparation for mitosis.

G1 Phase

First gap; major cell growth and normal metabolism.

S Phase

DNA synthesis phase where chromosomes are duplicated.

G2 Phase

Second gap; cell prepares for mitosis, builds spindle components.

Mitosis

Nuclear division producing two genetically identical nuclei.

Prophase

Chromatin condenses; nucleolus disappears; spindle begins to form.

Prometaphase

Nuclear envelope fragments; spindle microtubules attach to kinetochores.

Metaphase

Chromosomes align on the cell’s equatorial (metaphase) plate.

Anaphase

Sister chromatids separate and move toward opposite poles.

Telophase

Chromosomes de-condense; nuclear envelopes reform; spindle disassembles.

Cytokinesis

Division of cytoplasm; cleaves animal cells via cleavage furrow, plants via cell plate.

Cleavage Furrow

Contractile actin-myosin ring pinching animal cells in cytokinesis.

Cell Plate

Vesicle-derived partition that forms new wall between daughter plant cells.

Protein Kinase

Enzyme that activates or deactivates proteins by adding phosphate groups.

Cyclin

Regulatory protein whose levels fluctuate and activate Cdks.

Cyclin-Dependent Kinase (Cdk)

Kinase active only when bound to a cyclin; drives cell-cycle events.

MPF

Maturation-promoting factor; Cdk-cyclin complex triggering mitosis at G2 checkpoint.

Density-Dependent Inhibition

Phenomenon where crowded cells stop dividing.

Anchorage Dependence

Requirement that cells attach to a surface before they divide.

Benign Tumor

Mass of abnormal cells that remains at original site.

Malignant Tumor

Cancerous growth that invades and impairs organ function.

Metastasis

Spread of cancer cells to distant sites via blood or lymph.

Signal Transduction

Series of molecular events converting a signal on a cell’s surface to a specific response.

Reception

Stage where a signaling molecule (ligand) binds to a receptor protein.

Transduction

Relay of signal via cascade of molecular interactions in the cell.

Response

Cellular activity (e.g., gene expression, enzyme activation) triggered by a signal.

Ligand

Molecule that specifically binds to a receptor.

G Protein-Coupled Receptor (GPCR)

Seven-pass membrane receptor that activates a G protein upon ligand binding.

G Protein

Molecular switch using GDP/GTP to relay signals from GPCRs.

Receptor Tyrosine Kinase (RTK)

Dimers that autophosphorylate tyrosines and activate multiple pathways.

Ligand-Gated Ion Channel

Membrane receptor that opens/closes ion channel upon ligand binding.

Second Messenger

Small, diffusible molecule or ion relaying signals inside cells (e.g., cAMP, Ca2+).

cAMP

Cyclic AMP; widely used second messenger made from ATP by adenylyl cyclase.

Adenylyl Cyclase

Membrane enzyme converting ATP to cAMP after G-protein activation.

Protein Kinase A

cAMP-activated kinase that phosphorylates many target proteins.

Phosphodiesterase

Enzyme that degrades cAMP to AMP, terminating the signal.

Inositol Triphosphate (IP3)

Second messenger that releases Ca2+ from ER stores.

Diacylglycerol (DAG)

Lipid second messenger produced with IP3 by phospholipase C.

Calcium Ion (Ca2+)

Versatile second messenger whose cytosolic levels are tightly regulated.

Protein Phosphatase

Enzyme removing phosphate groups, turning off signaling proteins.

Signal Amplification

Process where one ligand binding event leads to large cellular output.

Cross-Talk

Interaction between different signaling pathways enhancing coordination.

Scaffolding Protein

Large relay protein holding multiple kinases to speed signaling efficiency.

Apoptosis

Programmed cell death involving DNA fragmentation and cell blebbing.

Caspase

Main protease family executing apoptosis by cleaving proteins.

Ced-9

C. elegans protein that inhibits apoptotic pathway when active.

Ced-4

C. elegans protein activating Ced-3 to start apoptosis.

Ced-3

C. elegans caspase responsible for apoptotic proteolysis.

Chloroplast

Double-membraned organelle where photosynthesis occurs in plants/algae.

Thylakoid

Flattened membrane sac inside chloroplast; site of light reactions.

Granum

Stack of thylakoids within a chloroplast.

Stroma

Fluid interior of chloroplast surrounding thylakoid stacks; Calvin cycle site.

Thylakoid Lumen

Internal space of a thylakoid where proton gradient builds.

Chlorophyll a

Main photosynthetic pigment absorbing blue-violet & red light.

Chlorophyll b

Accessory pigment broadening the spectrum of light available for photosynthesis.

Carotenoid

Accessory pigment (orange/yellow) absorbing blue/green light; protects chlorophyll.

Xanthophyll

Oxygen-containing carotenoid pigment (yellow/brown).

Phycobilin

Red/blue accessory pigment in cyanobacteria & red algae.

Anthocyanin

Flavonoid pigments giving flowers red-purple hues.

Photosystem I (PS I)

Light-capturing complex with P700 reaction center; generates NADPH.

Photosystem II (PS II)

Light-capturing complex with P680 reaction center; splits water, begins electron flow.

P700

Chlorophyll a reaction-center pair of PS I absorbing at 700 nm.

P680

Chlorophyll a reaction-center pair of PS II absorbing at 680 nm.

Noncyclic Electron Flow

Photosynthetic pathway producing ATP, NADPH, and O2 by linear electron transport.

Cyclic Electron Flow

PS I-dependent pathway producing extra ATP without NADPH or O2.

Photolysis

Light-driven splitting of water into electrons, protons, and oxygen in PS II.

Chemiosmosis

Use of a proton gradient across a membrane to drive ATP synthesis.

ATP Synthase

Enzyme complex coupling proton flow to phosphorylation of ADP.

Light-Dependent Reactions

Thylakoid reactions converting light energy to ATP and NADPH.

Calvin Cycle

Stroma reactions fixing CO2 into carbohydrate using ATP & NADPH.

Carbon Fixation

Incorporation of CO2 into organic molecules, first step of Calvin cycle.

RuBP

Ribulose-1,5-bisphosphate; 5-carbon CO2 acceptor in Calvin cycle.

PGA (3-PGA)

3-phosphoglycerate; first stable 3-carbon Calvin cycle product.

G3P (PGAL)

Glyceraldehyde-3-phosphate; 3-carbon sugar output of Calvin cycle.

Rubisco

Calvin cycle enzyme catalyzing CO2 (or O2) fixation to RuBP.

C3 Pathway

Standard Calvin cycle where first product is a 3-carbon molecule (PGA).

Photorespiration

Wasteful process where Rubisco adds O2 to RuBP, reducing photosynthetic output.

C4 Pathway

CO2-concentrating mechanism fixing carbon twice in mesophyll & bundle-sheath cells.

Oxaloacetate

Four-carbon first product of C4 carbon fixation.

Bundle-Sheath Cell

Inner leaf cell where C4 plants run the Calvin cycle.

Mesophyll Cell

Photosynthetic leaf cell that performs initial CO2 fixation in C4 plants.

CAM Pathway

Temporal CO2-concentrating strategy fixing CO2 at night, Calvin cycle by day.

Aerobic Respiration

Oxygen-requiring pathway breaking glucose to CO2 & H2O, yielding ~30-32 ATP.

Anaerobic Respiration

Energy pathway without O2, including fermentation; yields far less ATP.

Glycolysis

Cytoplasmic breakdown of glucose to two pyruvate, net 2 ATP & 2 NADH.

Pyruvate

Three-carbon end product of glycolysis.