wall

Xylem

... vessel element disintegrates, the thickened cell wall remains, forming a nonliving passage for the flow of water. Vessel elements form in plant parts that no longer elongate. Vessel elements are usually wider, shorter, thinner walled, and less tapered than tracheids . They are aligned end to end, form...

Virus

... —bacterial viruses—attach to the cell wall surface in specific places. Once attached, enzymes make a small hole in the cell wall, and the virus injects its DNA into the cell. Other viruses (such as HIV ) enter the host via endocytosis , the process whereby cells take in material from the ex...

Vacuole

...) is to keep a turgor pressure against the cell wall (thanks to water storage); if it fails at this (b...lso helpful for cellular elongation: when the cell wall is degraded (not entirely) by the action of auxins , this now less rigid wall is expanded by the pr...

Twin

...n two fertilized eggs are implanted in the uterine wall at about the same time, within the same menstrual cycle , or in rare cases within one menstrual cycle of each other. The two eggs form two zygotes, and these twins are therefore also known as dizygotic . Dizygotic twins are no more similar ge...

Turgor

...ell than outside), causing it to expand. The cell wall of a plant cell restricts the expansion, causing the cell to press against the wall. The resulting pressure is called turgor. The osmotic pressure π of a dilute solution can be calculated using the formula where M is the molarity R...

Plasmolysis

.... It is the cell membrane peeling off of the cell wall and the vacuole collapsing. Plasmolysis occurs ...ium and nitrate ions freely permeate the cell wall and encounter the selectively permeable plasma membrane . The large vacuole in the center of the ...

Cell membrane

... in yeast, bacteria and plants an additional cell wall forms the outermost boundary, providing primarily mechanical support. The plasma membrane is only about 10 nm thick and may be discerned only faintly with a transmission electron microscope . One of the key roles of the membrane is to maintain th...

Phloem

...cylindrical cells, with large pores in the cell wall at either end. They are almost entirely dead, and have no organelles. All of their functions of a sieve-tube element are carried out by its (much smaller but quite living) companion cell. While movement of water and minerals through the xylem is dr...

Osmosis

...ally equalled by the pressure exerted by the cell wall , creating a steady state . In fact, osmotic pres...- the cell membrane has completely left the cell wall due to lack of water pressure on it. In unusual environments, osmosis can be very harmful to organi...

Magnetic resonance imaging

...stenosis (abnormal narrowing) or aneurysms (vessel wall dilatations, at risk of rupture). The main uses of MRA is to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, and the kidneys. A variety of techniques can be used to generate the pictures, such as administration of a p...

Meiosis

...rioles. Nuclear envelopes reform; cleavage or cell wall formation eventually produces a total of four daughter cells, each with an haploid set of chromosomes. Significance of meiosis If meiosis did not occur, fusion of the gametes would not result in a diploid condition (2n) but 4n. Meiosis also pro...

Lung

...f the lungs and the outer layer is attached to the wall of the chest cavity. The two layers are separated by a thin space called the pleural cavity that is filled with pleural fluid ; this allows the inner and outer layers to slide over each other, and prevents them from being separated easily. The lef...

Lichen

...) . Crustose and foliose lichens on a wall Foliose lichen on basalt Usnea australis , a fruticose form, growing on a tree branch Lichens are symbiotic organisms made up by the association of microscopic green algae or cyanobacteria and filamentous fungi...

Kidney

...e glomerulus and the neighbouring Bowman's capsule wall to produce the glomerular filtrate, which enter th...apillae : The small conical projections along the wall of the renal sinus. They have openings through which urine passes into the calyces. (singular - pap...

Insulin

...on arterial muscle tone – forces arterial wall muscle to relax, increasing blood flow, especially in micro arteries; lack of insulin reduces flow by allowing these muscles to contract Regulatory action on blood glucose Despite long intervals between meals or the occasional consumption of mea...

Glucose

...bed into the bloodstream through the intestinal wall . Some of this glucose goes directly to fuel brain cells , while the rest makes its way to the liver and muscles , where it is stored as glycogen ("animal starch"), and to fat cells , where it is stored as fat . Glycogen is the body's auxilia...

Cell membrane

... in yeast, bacteria and plants an additional cell wall forms the outermost boundary, providing primarily mechanical support. The plasma membrane is only about 10 nm thick and may be discerned only faintly with a transmission electron microscope . One of the key roles of the membrane is to maintain th...

Diffusion

...um atoms inside a balloon can diffuse through the wall of the balloon and escape, resulting in the balloo... There is a concentration gradient in the balloon wall because the balloon was filled up with helium, and thus there is plenty of helium on the inside, but...

Cytosol

...ane , the cytoskeleton, the tonoplast or the cell wall (if present), are used to counteract the osmotic pressure. Details The cytosol is 20% to 30% protein . Normal human cytosolic pH is (roughly) 7.0 (i.e. neutral), whereas the pH of the extracellular fluid is 7.4....

Cytoskeleton

...la the mitotic spindle synthesis of the cell wall in plants. The prokaryotic cytoskeleton The c...recruiting other proteins that produce a new cell wall between the dividing cells. MreB and ParM Prokaryotic actin-like proteins, such as MreB , are ...

Cell growth

...almost all plant cells are inside of a solid cell wall . Under the influence of certain plant hormones the cell wall can be remodeled, allowing for increases in cell size that are important for the growth of some plan...

Biomechanics

...ia. For example, at the tissue level, the arterial wall can be modeled as a continuum . This assumption b...untarily contracted cells are located in the heart wall and operate in concert to develop synchronized beats. This is attributable to a refractory period be...