Cell Biology Terms Starting With V
Cell Biology Glossary: V
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Vacuole
/ VAK-yoo-ohl / · Latin: vacuolum (small vacuum)
Vacuole vacuole is a membrane-bound storage sac inside a cell; plant cells often have a large central vacuole that stores water and helps support the cell.
The large central vacuole of plant cells can comprise 50 to 90 percent of cell volume and maintains turgor pressure, the hydrostatic pressure that prevents wilting and maintains plant rigidity. Vacuoles store diverse substances including glucose, proteins, pigments, alkaloids, and other secondary metabolites depending on cell type and function. The vacuolar membrane tonoplast selectively accumulates ions and solutes that lower water potential and draw water into the vacuole osmotically.
Animal cells contain small vacuoles used primarily for temporary storage or osmoregulation, whereas fungal cells have a large vacuole similar to plants.
A plant central vacuole can occupy most of the cell's volume. It helps maintain turgor pressure, which supports soft plant tissues.
Central Vacuole →Vacuoles are only storage bags. Vacuoles can also regulate pH, digest materials, recycle molecules, and control water balance.
In Elodea leaf cells, the central vacuole pushes chloroplasts toward the cell edge. This arrangement can make chloroplast movement easier to observe.
Differences Between Plant and Animal Cells →Vesicle
/ VES-ih-kul / · Latin: vesicula (small bladder)
Vesicle vesicle is a small membrane-bound sac found in eukaryotic cells like human liver cells that temporarily stores or transports proteins, lipids, and other molecules between cellular compartments such as the endoplasmic reticulum, Golgi apparatus, and cell membrane.
Vesicles form through budding when coat proteins including COPII, COPI, or clathrin cause membrane curvature and pinching off from donor compartments such as the ER, Golgi, or plasma membrane. Specific cargo proteins contain sorting signals recognized by coat proteins and adaptor complexes, allowing selective packaging of materials into vesicles. SNARE proteins on vesicle and target membranes recognize each other and catalyze membrane fusion that releases vesicle contents into the target compartment.
This vesicular transport system delivers lipids and proteins to appropriate locations, maintains organelle structure and composition, and enables secretion and endocytosis.
Vesicles are small membrane-bound sacs that move materials inside cells. They can bud from one membrane and fuse with another.
Vesicles are random bubbles. Vesicle formation and targeting are controlled by specific proteins and signals.
At nerve endings, synaptic vesicles store neurotransmitters. When a signal arrives, some vesicles fuse with the membrane and release their contents.
Fun Facts About the Nervous System →Vimentin
/ vim-EN-tin / · Latin vimentum, twig or flexible rod; -in, protein suffix
Vimentin is a protein that forms strong fibers called intermediate filaments in many cells; fibers help support cell shape.
Vimentin proteins assemble into intermediate filaments approximately 10 nanometers in diameter that form an extensive network throughout the cytoplasm, extending from the nuclear envelope to the plasma membrane. These filaments provide mechanical support that lets cells withstand shear stress and stretching forces, particularly important in fibroblasts and other connective tissue cells. During cell migration and epithelial-mesenchymal transition, its organization changes and epithelial-mesenchymal transition, enabling cells to adopt elongated shapes for movement.
Phosphorylation of vimentin by multiple kinases can cause filament disassembly and reorganization in response to cellular signals.
Vimentin is an intermediate filament protein common in many mesenchymal cells. It helps cells resist mechanical stress and maintain shape.
Vimentin is found in every cell type equally. It is especially associated with connective-tissue-derived cells and cells undergoing certain shape changes.
In fibroblasts, vimentin filaments form part of the internal support network. This helps the cells withstand stretching as they move through connective tissue.
Voltage Clamp
/ VOHL-tij KLAMP / · volt (after Alessandro Volta) + Middle Dutch klampe (clasp)
A voltage clamp is a method for studying ion currents. It holds a cell's membrane voltage at a chosen value. A feedback amplifier injects current to keep that voltage fixed. The injected current mirrors the current flowing through ion channels. Researchers can then measure channel currents at each voltage. Kenneth Cole and George Marmont devised it in 1947.
Classic setups use two electrodes inside the cell. One records voltage while the other passes current. An amplifier compares the reading with the command voltage.
Hodgkin and Huxley used the method on squid axons. Five papers in 1952 explained how ionic currents drive spikes. Their model also captured fast inactivation of sodium current.
Modern versions clamp single cells or tiny membrane patches. Pharmacologists test channel-blocking drugs this way. Toxin researchers use it to measure blocked currents.
Hodgkin and Huxley shared the 1963 Nobel Prize. John Eccles shared that physiology prize with them. Each laureate received one third of the award. The squid giant axon was the first preparation clamped.
Many students think a voltage clamp measures voltage. It actually fixes the voltage and measures current. The current reveals how many channels open and when.
The longfin inshore squid (Doryteuthis pealeii) has giant axons. These nerve fibers can reach 1.5 millimeters in diameter. A typical 0.5-millimeter axon conducts about 25 meters per second. The axons trigger the squid’s jet-propelled escape. Their size lets researchers thread clamp electrodes inside.
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