Dr. Sajid Ali

2022-01-28 18:41:21 Open / Comment

2022-01-28 18:19:18 Factor Affecting Enzyme Activity

1. Temperature
Enzymes are sensitive to temperature
Optimum temperature is 25′-40′
Low temperature enzymes are inactivates
High temperature enzymes are denatures

2. Hydrogen Ion Concentration (pH)
Different enzymes have different optimum pH
Some enzyme prefer acidic pH for Optimum activity E.g. Pepsin (pH 1.2-1.8)
Some enzyme prefer alkaline pH for Optimum activity E.g. Trypsin (pH 8.6-8.8)
Some enzyme prefer Neutral pH for Optimum activity E.g. amylase (pH 6.8)

3. Substrate Concentration
Increase in the substrate concentration increases the activity of the enzyme until all the active sites of the enzyme molecule are saturated with the substrate.
After this saturation the rate of enzymatic reaction becomes steady.
Then, the addition of the substrate will not have a positive effect on the velocity of reaction.

4. Water
Enzyme activity is suppressed in the absence of water
In dry seeds, the enzymes are almost inactive

5. Accumulation of End Products
The end product accumulation retards the enzymatic activity
The active sites of the enzymes become crowded with the products
Thus, the substrate molecules will have comparatively lesser chances of combining with the active sites

6. Inhibitors
Inhibitors in the reaction can inhibit enzymatic activity
Inhibitors are of different types: i) Competitive inhibitors ii) Noncompetitive inhibitors and iii) Allosteric inhibitors Open / Comment

2022-01-28 18:19:06 Enzyme Inhibitors and Types Short Notes

What is enzyme inhibitors?
Enzyme Inhibitors reduce the rate of an enzyme on the substrate
This effect may be permanent or temporary
Types of Enzyme Inhibition
1. Competitive Inhibition
2. Noncompetitive Inhibition
3. Allosteric Inhibition

I) Competitive Inhibition
Inhibitor bind to active site of enzyme and block binding of the substrate
Inhibitors have a similar shape to the substrate molecule
Competitive Inhibition is usually temporary
Level of inhibition depends on the relative concentrations of substrate

II) Noncompetitive Inhibition
Inhibitor doesn’t block the substrate from binding to the active site
Inhibitor binding to a site other than the active site
Binding of the inhibitor causes a conformational change to the enzyme’s active site
As a result of this change, the active site and substrate no longer share specificity, meaning the substrate cannot bind
As the inhibitor is not in direct competition with the substrate, increasing substrate levels cannot mitigate the inhibitor’s effect


III) Allosteric Inhibition
Alosteric means other site
These enzymes have two receptor sites
One site fits the substrate like other enzymes
The other site fits an inhibitor
Accumulation of the final product of the reaction is capable of inhibiting the step of reaction Open / Comment

2022-01-28 17:34:52 https://t.me/+aC1qj4GKLS43NWJl..
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2022-01-25 16:22:51 Cell Wall Structure and Function

What is Cell Wall?
Cell wall is rigid and protective layer around the plasma membrane
Discovered by Robert hooke in 1665
Cell wall non-living rigid structure
Found in plants, fungi, prokaryotes and protists
Composition of cell wall varies in different groups

Characteristics of Cell Wall
Cell wall is a rigid and protective layer around the plasma membrane
It is a non-living structure
Animal cells do not have a cell wall
Found in in most plant cells, fungi, bacteria, algae, and some archaea
Cell wall has many important functions in a cell including protection, structure, and support


Cell Wall Structure

Structure of Prokaryotes Cell Wall
Cell wall is made up of peptidoglycon
Peptidoglycan made up of polysaccharide chains cross-linked by unusual peptides containing D-amino acids
A notable difference between the cell walls of gram-positive and gram-negative bacteria is the substantially thicker peptidoglycan layer in gram-positive bacteria.
Cell wall of gram-positive bacteria contains teichoic acids

Structure of Fungi Cell Wall
Fungal cell wall is made up of three main components

Chitin
Polymers consisting mainly of unbranched chains of β-(1,4)-linked-N-Acetylglucosamine in the Ascomycota and Basidiomycota, or poly-β-(1,4)-linked-N-Acetylglucosamine (chitosan) in the Zygomycota
Both chitin and chitosan are synthesized and extruded at the plasma membrane

Glucans
Glucose polymers that function to cross-link chitin or chitosan polymers
β-glucans are glucose molecules linked via β-(1,3)- or β-(1,6)- bonds and provide rigidity to the cell wall while α- glucans are defined by α-(1,3)- and/or α-(1,4) bonds and function as part of the matrix

Proteins
Enzymes necessary for cell wall synthesis and lysis in addition to structural proteins are all present in the cell wall.
Most of the structural proteins found in the cell wall are glycosylated and contain mannose, thus these proteins are called mannoproteins or mannans.


Structure of Plant cell wall
Cell wall is made up of 4 layers
Middle lamella, primary, secondary and tertiary wall

I) Middle lamella
Cementing layer between the cells
It is made up of ca & mg pectates

II) Primary cell wall
Found in growing cell
It has high hemicelluloses & less cellulose content

III) Secondary cell wall
Found in mature cell
It has high cellulose & less hemicelluloses content

IV) Tertiary cell wall
Laid down on secondary wall
Found in tracheids of gymnosperms

What is Pits?
Cell wall is not uniform in thickness throughout
Certain places cell wall are not laid down, such places are called pits


Pits are of two types

I) Simple Pit
Pit chamber is uniform in diameter
Found in angiosperms

II) Bordered pit
Pit chamber is flask shaped
Found in gymnosperms
Number of plasmodesmata or cytoplasmic strands are present in pit

Functions of cell wall
Maintains shape of the cells
Protects cell from mechanical injury
Allows materials to pass in and out of the cell
Prevents undue expansion of cell when water enters by osmosis Open / Comment

2022-01-25 16:05:28 Dr. Sajid Ali pinned «

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2022-01-25 15:21:26

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