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The amount of substrate needed to achieve a given rate of reaction is also important. This is given by the Michaelis–Menten constant (K m), which is the substrate concentration required for an enzyme to reach one-half its maximum reaction rate; generally, each enzyme has a characteristic K M for a given substrate.
For a given enzyme concentration and for relatively low substrate concentrations, the reaction rate increases linearly with substrate concentration; the enzyme molecules are largely free to catalyse the reaction, and increasing substrate concentration means an increasing rate at which the enzyme and substrate molecules encounter one another.
The resting concentration of Ca 2+ in the cytoplasm is normally maintained around 100 nM.This is 20,000- to 100,000-fold lower than typical extracellular concentration. [1] [2] To maintain this low concentration, Ca 2+ is actively pumped from the cytosol to the extracellular space, the endoplasmic reticulum (ER), and sometimes into the mitochondria.
Calcium regulation in the human body [38] Different tissues contain calcium in different concentrations. For instance, Ca 2+ (mostly calcium phosphate and some calcium sulfate) is the most important (and specific) element of bone and calcified cartilage. In humans, the total body content of calcium is present mostly in the form of bone mineral ...
Calcium regulation in the human body. [6]The plasma ionized calcium concentration is regulated within narrow limits (1.3–1.5 mmol/L). This is achieved by both the parafollicular cells of the thyroid gland, and the parathyroid glands constantly sensing (i.e. measuring) the concentration of calcium ions in the blood flowing through them.
In biochemistry, control coefficients [1] are used to describe how much influence a given reaction step has on the flux or concentration of the species at steady state.This can be accomplished experimentally by changing the expression level of a given enzyme and measuring the resulting changes in flux and metabolite levels.
Thus, in controlling blood sugar levels, they indirectly affect the activity of HMG-CoA reductase, but a decrease in activity of the enzyme is caused by AMP-activated protein kinase, [16] which responds to an increase in AMP concentration, and also to leptin.
The human body's rate of iron absorption appears to respond to a variety of interdependent factors, including total iron stores, the extent to which the bone marrow is producing new red blood cells, the concentration of hemoglobin in the blood, and the oxygen content of the blood.