Download Factors affect enzymatic speed

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Dr.A. Basit. A.Sammed
Factors affect enzymatic speed
1-Temperature
and optimal pH
A 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 ,enzyme’s 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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Assist .professor
Dr.A. Basit. A.Sammed
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+² ,K+² , Ca+²,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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Assist .professor
Dr.A. Basit. A.Sammed
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 the
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Dr.A. Basit. A.Sammed
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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Dr.A. Basit. A.Sammed
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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