practicals biochem

• Parallax error is a deceptive change in the relative position of an object with a change in the position of the observer.
• In manual pipetting, parallax error can occur when the meniscus of a volumetric glassware, like a pipette, is not at eye level, leading to inaccurate readings.
• If the meniscus is above eye level, an increased volume measurement will be made, while if the eye is above the meniscus, a lower volume reading will be made.
• Volumetric pipettes are classified as transfer pipettes, while serological pipettes are classified as graduated or measuring pipettes.
• Pipette calibration marks: Up to the last highest volume, up to the tip
• Volumes of liquid: Single volume, fixed; Multiple volumes
• TD (To deliver): Only the liquid that freely drains from the tip
• After draining a "to contain" pipette, the residual liquid in the tip should be blown out
• BLOW OUT and NON-BLOW OUT PIPETTES: Marked by double etched rings or none
• Air displacement pipettes have an air cushion between the piston and the sample
• To avoid errors in accuracy and precision when using a mechanical pipette, the air displacement pipette's operating technique should be followed correctly
• Do not "pop" the plunger as it can lead to fluid entering the shaft and damaging the piston, reducing accuracy.
• Fast aspiration can lead to bubbles, which also reduce accuracy.
• Never tilt or lay a pipette down that has fluid in the tip as it can lead to liquid in the shaft, piston damage, and inaccuracy.

  
  

  <Title>: Pipette Calibration Method and Principle
• Gravimetric method is used for pipette calibration.
• An aliquot of distilled water is placed in a vessel and its weight is measured using an analytical balance.
• The weight is then converted to mass and then to volume using standard conversion factors or software packages.
• Carbohydrates can be classified based on reactivity as reducing and non-reducing sugars.
• Reducing sugars are capable of reducing ferric or cupric ions.
• Reducing sugars have a free aldehyde group that enables them to act as reducing agents.
• The free anomeric carbon of the disaccharide or polysaccharide chain, which is not involved in the glycosidic linkage, is referred to as the reducing end of the chain.
• All disaccharides, except sucrose and trehalose, are reducing sugars.
• All sugars that act as reducing agents undergo mutarotation.
• Non-reducing sugars are not capable of reducing ferric or cupric ions.
• Maltose is a reducing agent because it has one anomeric carbon that can open to form an aldehyde group.
• Maltose has glucose units joined in a head-to-tail fashion through an a-1,4-glycosidic linkage.
• Sucrose is not a reducing agent because it has an a-1, B-2 glycosidic linkage formed by the OH group on the anomeric carbon.
• Seliwanoff's test: A strong acid is used in the Seliwanoff's test to dehydrate ketose sugars and produce furfurals or their derivatives, which react with resorcinol in the reagent to yield a cherry-red hue complex.
• Starch monomeric units: Amylose is composed of straight chain polymers of D-glucose subunits, while amylopectin is composed of branched-chain polymers of D-glucose subunits.
• Differences between amylose and amylopectin: Amylose is water-soluble, while amylopectin is water-insoluble. Amylose does not exhibit gelling when hot water is added, while amylopectin exhibits gelling. Addition of iodine solution turns amylose blue, but does not produce a blue color in amylopectin.
• Biuret test is a chemical test used to determine the presence of a peptide bond in a substance.
• The Biuret test can be extended to quantitatively measure the concentration of total proteins using spectrometric methods.
• Proteins contain the elements carbon, hydrogen, and oxygen.
• Proteins undergo various reactions that can be used to determine their composition and properties.
• Amino acids contain nitrogen and have a specific conformation around a central carbon atom.
• Each amino acid consists of a central carbon atom connected to a side chain, a hydrogen, a nitrogen-containing amino group, and a carboxylic acid group.
• Amino acids differ from each other based on the specific side chain bonded to the carbon center.
• R denotes the alkyl group in amino acids.
• Amino acids can behave as both acids and bases due to the presence of nitrogen in the amine group and oxygen in the carboxylic group.
• Amino acids are acidic due to the behavior of hydrogens.