biolab midterms

Carbohydrates

Is a group of organic compounds that

contains carbon, hydrogen and oxygen;

sugars, starches, celluloses, and gums

contain these elements and serve as a

major source

Main source of energy of the muscles

Molisch Test Def

Chemical test which is used to check for

the presence of carbohydrates in a given

analyte

Concentrated sulfuric acid (H2SO4) is

added to the analyte

An appearance of reddish violet or violet

ring indicates a positive reaction of

Molisch’s reagent

Iodine Test Def

is a simple chemical test used to detect

the presence of starch in a sample.

It gives a characteristic blue-black color, indicating the presence of starch.

Starch reacts with iodine solution forms

complex colour solution

Tollen’s Test Def

To detect reducing sugars, specifically

aldoses (sugars with an aldehyde group).

Carbohydrates react with Tollens

reagent and forms a silver mirror on the

inner walls of the test tube.

This confirms the presence of reducing

sugars.

Fehling’s Test Def

This test is given by reducing sugars.

Fehling’s solution is added and heated in

water bath.

The formation of red precipitate

confirms the presence of reducing

sugars.

Benedict’s Test Def

Used to identify reducing sugars

(monosaccharides and some

disaccharides)

Red precipitate of cuprous oxide is

formed.

Barfoed’s Test Def

is used to distinguish between

monosaccharides and disaccharides

based on their ability

Any slight change in coloration is an

indication of positive results

Lipids

Lipids are the organic biomolecules

soluble in non-polar solvents

 The qualitative analysis of lipids helps

us determine the presence or absence of

lipid

 Hydrophobic molecules

o non-polar substances that do not

mix with water

Greece Spot Test Def

a simple qualitative test used to detect

the presence of lipids (fats and oils) in a

sample.

 Lipids do not evaporate, they leave a

permanent translucent stain on paper

Polar Solvent

Lipids do not dissolve because

they lack charged or polar

functional groups to form

hydrogen bonds with water.

Non polar solvent def

Lipids dissolve easily because

they share similar hydrophobic

interactions, allowing them to

mix uniformly.

Soluble

A substance that dissolves in a solvent to form a homogeneous solution

Insoluble

A substance that does not dissolve in a solvent, remaining separate or forming a suspension.

Sudan Red Test Def

is a qualitative test used to detect the

presence of lipids.

Sudan Red is a lipid soluble dye. When it is added to a mixture of lipids and water, the dye will move into the lipid layer coloring it red

TEST FOR THE PRESENCE OF

CHOLESTEROL IN FOOD def

Cholesterol reacts with acetic anhydride and

concentrated sulfuric acid, producing a green or blue-green color, confirming the presence of cholesterol.

Greenish color indicates the presence of cholesterol

UNSATURATION BROMINE WATER TEST def

This test will validate the presence of

unsaturated fatty acids

 Colorless- the oil contains unsaturated

fatty acids

 Unsaturated lipids react with bromine,

leading to decolorization.

 Saturated lipids do not react, and

bromine water remains brown.

AMMONIUM MOLYBDATE TEST

 is a qualitative test used to detect the

presence of phospholipids

 The test is specific to phospholipids

 Yellow precipitate indicates a positive

reaction of fatty acids

Protein

Large organic compounds composed of

amino acids

 Vital components of cells used by

organisms for all biological processes

 Speeds up biochemical reactions to

regulated body metabolism

 Other proteins are used in cell signaling,

immune responses, cell adhesions, and

the cell cycle

URINE PROTEIN

is a rapid, qualitative or semi-

quantitative test used to detect

proteinuria (the presence of abnormal

levels of protein in the urine).

 It is a key diagnostic tool for evaluating

kidney function and detecting

underlying systemic diseases

Biuret’s Test Def

Qualitative test used to detect the

presence of proteins and peptides in a

solution.

 It is based on the reaction between

copper ions (Cu²⁺) and peptide bonds in

an alkaline medium.

 Positive result for the presence of

protein is purple color.

Xanthoproteic Acid Test Def

is a qualitative test used to detect

aromatic amino acids (such as tyrosine,

tryptophan, and phenylalanine) in

proteins.

 It is based on the reaction of these amino

acids with concentrated nitric acid

(HNO₃), which forms a yellow-colored

nitro compound.

 Yellow color tyrosine

 Orange color: tryptophan

Cystine def

 is used to detect the presence of cystine,

a sulfur-containing amino acid found in

some proteins.

 The presence of disulfide bonded

cysteine in proteins will give a black

precipitates as a positive result

 Reacts with lead acetate to form black

lead sulfide precipitate

Ninhydrin Test Def

is a qualitative test used to detect free

amino acids and proteins with free

amino groups .

 It is widely used in biochemistry to

analyze amino acid composition and

detect proteins, peptides, and amines.\

 Violet or purple color presence of α-

amino acids or proteins

Million’s Test Def

 is a qualitative test used to detect the

presence of tyrosine, an aromatic amino

acid found in proteins

 This test gives a red precipitate or a red

solution

 The positive reaction happens when

phenol group of tyrosine reacts with

nitrate and forms a phenol complex with

mercury (I) and mercury (II) ions.

 False positives may occur with phenol-

containing compounds (e.g., some plant

extracts).

Denaturation of proteins

 Is a process in which protein or nucleic

acids lose their secondary structure by

application of some external stress or

compound.

 Different chemicals can disrupt the

structure of proteins by interfering with

hydrogen bonds, ionic bonds,

hydrophobic interactions, or disulfide

bonds

Causes of protein denaturation

Strong acids or bases: Extreme acidic or basic conditions disrupt ionic bonds and hydrogen bonding

High concentration of inorganic salts

Organic solvents: Alcohol, Acetone,Chloroform

Temperature: High temperatures increase molecular motion, breaking weak interactions like hydrogen bonds