Factors affect enzymatic speed
1-Temperature and optimal pHA high temperature generally results in an increase in enzyme activity ,but ,if the temperature rises beyond a certain point ,enzymes activity eventually levels out and then declines rapidly because the enzymes is denatured ,in this case ,enzymes shape changes and then it can no longer bind substrate molecules efficiently .
Changes in PH can also affect enzyme activity ,each enzyme has an optimal PH activity ,e.g., a change in pH can alter the ionization of hydrogen bond between R group of protein molecule ,and disrupt the normal interaction ,and denaturation occurs.
2-Amount of the enzyme
Cellular mechanisms control both enzyme concentration and activity. Concentration increase when genes are turned on and protein {enzyme } production occurs ,and decreases when genes are turned off and protein production does not occur ,regulation of enzyme activity is by phosphorylation .3-Enzyme inhibitors
Inhibition is a common means by which cells regulate enzyme activity. Enzyme inhibition may be reversible or irreversible ,there are two major types of reversible inhibition ,competitive and non competitive .The first one a compound similar in structure to the substrate which forms a complex with the enzyme .
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In non competitive inhibition ,the inhibitor and the substrate are not structurally related ,and the inhibitor bind to a different site than the substrate.
Irreversible inhibition involves either the denaturation of the enzyme or the formation of a covalent bond with the enzyme .As the product is used up ,inhibition is reduced and more products can be produced.
4-Cofactors and coenzymes
Many enzymes required a non protein cofactor to assist them in carrying out their function . Some cofactors are ions : Mg+ ,K+ , Ca+,are involved in enzymatic reactions .
Coenzymes are organic molecules that bind to enzymes and serve as carrier for chemical groups or electrons .Coenzymes participate directly in the reaction .The function of the coenzymes is to accept two electrons and a hydrogen ion from the substrate .
Energy release
Substrate + NAD + enzyme oxidized substrate + NADH
This is a degradation reaction {oxidation} that release energy ,the two electrons of NADH can then be transfer to a second molecule which will become reduced {i.e. it gains electrons}.
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Another coenzyme called FAD { flavin adinine dinucleotide } also carries high energy electrons ,both NAD+ and FAD are involved in aerobic respiration ,a metabolic pathway in mitochonderia by which substrates are oxidized in a step by step manner to carbon dioxide and water .NAD+ and FAD are electron carries that take electrons to the electron transport system in mitochonderia ,this system release energy that is used to produce ATP molecules .
Vitamin {vit:life} are relatively small organic molecules that are required in trace amount in our diet and in the diet of other animals for synthesis of coenzymes in cells is similarly dependent on our intake of vitamins these vitamins are of particular cellular interest .
The deficiency of any one of these vitamins result in a lack of the co enzymatic and therefore a lack of certain enzymatic actions .
In human ,this result in vitamin deficiency syndromes :Niacin deficiency results in a skin disease called pellagra , Riboflavin deficiency results in cracks at the corners of the mouth .{Coenzymes are non-protein molecules that assist enzymes in performing their reaction}.
Cellular differentiation and tissue formation
A fertilized egg (zygote) is a single cell whose cellular descendant are capable of forming all different cell types within in the body .The long list of possibilities includes skin cells ,muscle cells ,glandular cells ,bone cells ,liver and so on ,such a list of possibilities constitutes theAssist .professor
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potentiality of a cell or group of cells .Within a developing multicellular organism ,cells that are dividing also become different .Differentiation take place in steps (steps in the process of gene expression at which regulation can take place ) .At each successive cell division and differentiation the range of possible future identities for that cell lineage is narrowed ,until the potentiality narrows to a single cell type .Once a cell lineage has differentiated as muscle cells for example ,all progeny cells are committed to being muscle cells .Like cell division ,differentiation is tightly regulated by the control of gene expression .Much of what we know about cell differentiation has came from embryology ( the study of the development of an organism from a zygote ).
Potentiality determination
The zygote has maximum potentiality because it gives rise to all cell types and may thus be called totipotent . The potentiality of cells has been investigated by transplanting cells from the embryos of experimental animals .Up until the eight cell stage ,each of the cells in a mammalian embryo is totipotent and could develop into a complete organism .As the cells continue to divide ,they first form a hollow ball called a blastula .Cells in a blastula are no longer totipotent .Soon they begin to differentiate and form tissue layer (endoderm ,mesoderm ,and ectoderm ) ,a process that begins at a landmark called the dorsal lip.Cells in each layer are restricted to becoming certain types of tissues .At the
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stages were the hallow ball embryo has formed differentiated cell layers it is called a gastrula .
A group of cells removed from the ectodermal layer of the embryo at the gastrula stage and transplanted else where on the same embryo can form various tissue types ,but only types that are ectodermal .
Such cells are said to be pluripotent because their potentiality is still quite broad but not as broad as that of the zygote ,each of the gastrula cell layers is pluripotent ,destined to become certain types of cells .Cells transplanted at a later time have a further narrowed potentiality .An ectodermal cell is restricted to one of two groups ,epidermal cells or cells of nervous system .Finally at a still later stage ,the fate of these cells is completely determined ,so that eye lens cells for example can form only eye lens tissue .
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