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Michaelis-Menten constant

2014-10-16T11:18:55Z

130298308:

The Michaelis-Menten describes and enzyme reaction and is as follows:

 

=== V= Vmax[S]/Km[S] ===

V= is the rate of the reaction

Vmax= is the maximal rate of the reaction

Km= the concentration at which Vmax is 1/2

 

Using the Km, this equation is useful to tell the affinity an enzyme has for its substrate. If the Km is high, this means the concentration at which 1/2Vmax is reached is high, so the affinity the enzyme has for its substrate is low (because a lot of substrate is needed to reach 1/2 Vmax). If Km is low, this means the affinity is high, because less substrate was needed to get to half the maximal rate of the reaction (Vmax).

Down, J.E and Riggs, D.S. 1965, A comparison of estimates of Michaelis-Menten kinetic constants from various linear transformations. The Journal of Biological chemistry. 240 (2),

Michaelis-Menten constant

2014-10-16T11:08:39Z

130298308: Created page with "The Michaelis-Menten describes and enzyme reaction and is as follows: === V= Vmax[S]/Km[S] === V= is the rate of the reaction Vmax= is the maximal rate of the reaction Km..."

The Michaelis-Menten describes and enzyme reaction and is as follows:

=== V= Vmax[S]/Km[S] ===

V= is the rate of the reaction

Vmax= is the maximal rate of the reaction

Km= the concentration at which Vmax is 1/2

Using the Km, this equation is useful to tell the affinity an enzyme has for its substrate. If the Km is high, this means the concentration at which 1/2Vmax is reached is high, so the affinity the enzyme has for its substrate is low (because a lot of substrate is needed to reach 1/2 Vmax). If Km is low, this means the affinity is high, because less substrate was needed to get to half the maximal rate of the reaction (Vmax).

F-actin

2013-11-28T20:21:31Z

130298308: Created page with "Actin is one of the proteins composing the cytoskeleton. Actin filaments are polymers made up of globular actin monomers called G-actin. When these polymerise, using ATP, they fo..."

Actin is one of the proteins composing the cytoskeleton. Actin filaments are polymers made up of globular actin monomers called G-actin. When these polymerise, using ATP, they form actin filaments, referred to as F-actin; filamentous actin. Under the right conditions, G-actin will self-assemble and form F-actin. Two actin filaments then form a double helix. 

 

The function of actin filaments is to provide the cell with strength, shape and movement. Actin underlies the plasma membrane, and can form many cell surface projections such as lamellopodia, filopodia (for movement), stereocilia (eg response to sound in the inner ear) and microvilli (to increase the surface area to make absorption more efficient). Actin filaments are also responsible for the division of cells after nuclear division has occured. This happens by actin forming a contractile ring, separating the two cells.

 

Actin filaments are also extremely important in muscle contraction, as this is where myosin binds to induce contraction.

 '''References''' Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., Walter, P., (2008) Molecular biology of the cell, 5th edition. New York: Garland Science

Berg, J.M., Tymoczko J.L., Stryer, L., (2012), Biochemistry, 7th edition, Houndsmills: W.H. Freeman and Company