Biochemical Tests for Food Macromolecules with Examples

Biochemical Tests for Food Macromolecules with Examples


A macromolecule is a molecule that has a huge number of atoms. Macromolecules have more than 100 constituent atoms on average. When applicable, macromolecules and their components have considerably different properties than smaller molecules.

Carbohydrates, lipids, proteins, and nucleic acids are the four major types of biological macromolecules. Each is a significant component of the cell and performs various tasks. When added together, these molecules make up the majority of a cell’s mass. Biological macromolecules are made up of carbon making them organic. Hydrogen, oxygen, nitrogen, phosphorus, sulfur, and other minor elements may also be present.

Organic molecules in organisms have various functions depending on their chemical structures and properties.

This blog post discusses the various biological food macromolecules and provides various examples on tests to check for their presence. As you follow along, remember that our qualified writers are always ready to help in any of your nursing assignments. All you need to do is place an order with us!

Types of Biological Macromolecules.


Carbohydrates are macromolecules that are recognizable to most people. Carbohydrates are an essential part of our diet; natural sources of carbohydrates include grains, fruits, and vegetables. Carbohydrates, notably glucose, a simple sugar, offer energy to the body. Carbohydrates play a variety of roles in humans, animals, and plants.

The formula for carbohydrates is (CH2O)n, where n is the number of carbon atoms in the molecule. In other words, the carbon-to-hydrogen-to-oxygen ratio in carbohydrate molecules is 1:2:1.

Carbohydrates also serve additional purposes in living things. Ribose, deoxyribose, and the five-carbon monosaccharides are integrated into the nucleic acid structure found in every living cell. Furthermore, in plants, the polysaccharide cellulose, which is a long polymer made up of glucose, acts as a hard structural substance. Humans lack the digestive enzymes needed to break down cellulose in food, commonly known as dietary fiber. Dietary fiber, on the other hand, aids in the maintenance of a healthy gut flora, which benefits the digestive and immunological systems. Some animals and fungi, like plants, use another polysaccharide called chitin as a structural component. Arthropods use chitin to develop and maintain their exoskeletons, while fungi use it to keep their cell walls stiff.

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Categories of Carbohydrates


Monosaccharides are simple sugars, with glucose being the most common. The number of carbon atoms in monosaccharides ranges typically from three to six. The suffix -ose is found at the end of most monosaccharide names. They are classified as trioses (three carbon atoms), pentoses (five carbon atoms), or hexoses (six carbon atoms) depending on the number of carbon atoms in the sugar.

C6H12O6 is the chemical formula for glucose. Glucose is a significant source of energy for most living things. Energy is liberated from glucose during cellular respiration and used to help create adenosine triphosphate (ATP). Photosynthesis is the process through which plants convert carbon dioxide and water into glucose, which is then used to meet the plant’s energy needs. Excess glucose is frequently stored as starch, which is broken down by creatures that graze on plants.

Monosaccharides can take the form of a linear chain or a ring-shaped molecule; in aqueous solutions, the ring form is most common.

Other monosaccharides include galactose (a component of lactose or milk sugar) and fructose (found in fruit). Despite having the identical chemical formula (C6H12O6), glucose, galactose, and fructose differ structurally and chemically (and are known as isomers) due to different atom positions in the carbon chain.


When two monosaccharides undergo a dehydration event, disaccharides are formed (a reaction to remove a water molecule occurs). During this reaction, one monosaccharide’s hydroxyl group (–OH) reacts with a hydrogen atom of another monosaccharide, releasing a molecule of water (H2O) and producing a covalent link between the two sugar molecules.

Lactose, maltose, and sucrose are examples of common disaccharides. Lactose is a disaccharide made up of glucose and galactose monomers. Milk contains it naturally. Maltose, often known as malt sugar, is a disaccharide that results from the dehydration of two glucose molecules. Sucrose, or table sugar, is the most common disaccharide, consisting of glucose and fructose monomers.


Polysaccharides are the most common type of carbohydrate found in nature. The most prevalent polysaccharide, cellulose, is a major structural component in plants, consisting of several units of glucose linked together.

A polysaccharide is a lengthy chain of monosaccharides joined by covalent bonds. The chain can be branched or unbranched, and several forms of monosaccharides can be found within it. Polysaccharides have the potential to be massive molecules. Polysaccharides include starch, glycogen, cellulose, and chitin.


Plants store carbohydrates in the form of starch, which is made up of amylose and amylopectin (both polymers of glucose). Plants can produce glucose, and any surplus glucose is stored as starch in various plant sections, including the roots and seeds. Animals ingest starch, which is broken down into smaller molecules like glucose. The glucose can subsequently be absorbed by the cells.


Glycogen, which is made up of glucose monomers, is the storage form of glucose in humans and other animals. Glycogen is the animal equivalent of starch, and it is a highly branched molecule that is stored mostly in the liver and muscle cells. Glycogen is broken down to release glucose when glucose levels drop.


Cellulose is one of the most common biopolymers found in nature. Plant cell walls are primarily formed of cellulose, which gives the cell its structural support. Cellulosic materials such as wood and paper are abundant in nature. Cellulose is made up of glucose monomers that are joined together by bonds formed by carbon atoms in the glucose molecule.

In cellulose, every other glucose monomer is flipped over and densely packed as extended long chains. This is what gives cellulose its rigidity and excellent tensile strength, both of which are critical for plant cells. Dietary fiber is cellulose that passes through our digestive system. While human digestive enzymes cannot break down the glucose-glucose linkages in cellulose, herbivores such as cows, buffalos, and horses can digest cellulose-rich grass and use it as a food source. Certain bacteria live in the rumen (a portion of a herbivore’s digestive tract) and secrete the enzyme cellulase in these animals.

Functions of Carbohydrates

The body’s leading roles in carbohydrates are to generate energy, store energy, secure the body’s protein storage, assemble macromolecules, and promote lipid metabolism.

Carbohydrates provide energy to all somatic cells. Most cells prefer glucose as their primary source of energy over fatty acids. Other cells, such as red blood cells and the brain, make energy solely from glucose. Somatic cells break down the chemical bonds in glucose and release energy in a controlled manner.

When the body stores enough energy to function correctly, excess glucose is stored in the liver and muscle cells, primarily in the form of glycogen. Glycogen is widely diverged to allow rapid degradation whenever cells need energy. 

Some of the glucose absorbed by the body forms ribose and deoxyribose. The two sugars are important components of ATP, RNA, and DNA. Glucose is also used in NADPH production, acting as a cofactor for chemical reactions and quenching the body against reactive oxygen species (ROS).

The availability of adequate glucose levels prevents the breakdown of proteins as a means of energy production by somatic cells. Elevated blood sugar also limits the use of lipids as an energy source. High blood sugar levels stimulate insulin release, which signals the body’s cells to use glucose as energy.

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Proteins are one of the most abundant organic molecules in biological systems and have the most diverse functions of macromolecules. Proteins can be structural, regulatory, contractile, or protective. They can be used for transportation, storage, or membranes. Or they can be toxins or enzymes. Each cell in a living system can contain thousands of different proteins, each with its own unique function. Their structure is as different as their function. However, they are all polymers of amino acids arranged in a linear sequence.

There are 20 chemically different amino acids that form long chains, and the order of the amino acids is arbitrary, so the functions of proteins are very diverse. For example, proteins can function as enzymes or hormones. Enzymes produced by living cells are catalysts for biochemical reactions (such as digestion) and are usually proteins. Each enzyme is specific to the substrate on which it acts (the reactant that binds to the enzyme). Enzymes can break molecular bonds,  rearrange bonds, and form new bonds. An example of an enzyme is salivary amylase, which breaks down amylose, a component of the starch.

Hormones are chemical signaling molecules. Usually, proteins or steroids, secreted by endocrine glands or groups of endocrine cells that control or regulate specific physiological processes such as growth, development, metabolism, and reproduction. For example, insulin is a protein hormone that maintains blood sugar levels.

Proteins come in a variety of shapes and molecular weights. Some proteins are spherical, while others are fibrous in nature. For example, hemoglobin is a globular protein, but the collagen found in our skin is a fibrous protein. The shape of a protein is important for its function. Changes in temperature, pH, and exposure to chemicals can cause permanent changes in protein shape, resulting in loss of function or denaturation (more on this later). All proteins are composed of different arrangements of the same 20 amino acids.

Amino acids are the monomers that makeup proteins. Each amino acid has the same basic structure consisting of an amino group (-NH2), a carboxyl group (-COOH), and a central carbon atom bonded to a hydrogen atom. Each amino acid also has another variable atom or group of atoms attached to a central carbon atom known as the R group. The R group is the only structural difference between the 20 amino acids. Otherwise, the amino acids are the same.

Functions of Protein.

Oxygen transport- hemoglobin, a protein in red blood cells, plays an important role in oxygen transport by acting as a carrier from the lungs to tissues.

Protein functions as an enzyme -Enzymes catalyze certain biochemical reactions and speed them up. Each enzyme has a specific binding site that binds to a specific substrate, such as the lock key. The

Protein also functions as an antibody -Antibodies are an important component of humoral immunity. They recognize and bind to specific foreign antigens, marking them for destruction by other immune cells.

Proteins are part of the body’s structure, such as ligament collagen and hair cell keratin.

Shrinkable proteins promote muscle cell contraction and individual intracellular movement. 

Protein also makes receptors, which are important components of signaling pathways.


Lipids, which comprise fats, oils, and waxes, are another class of biological macromolecules. Lipids are hydrophobic compounds composed primarily of carbon and hydrogen atoms. Triglycerides, phospholipids, and steroids are the three major kinds of lipids.

Lipids are a varied category of chemicals that share a common characteristic. Because lipids are nonpolar molecules, they are hydrophobic (“water-fearing”) and insoluble in water. Because they are hydrocarbons with solely nonpolar carbon-carbon or carbon-hydrogen bonds, this is the case. In a cell, lipids serve a variety of roles. Fats are lipids that cells employ to store energy for long-term use. Plants and animals use lipids to protect themselves from the elements. Because of their water-repellent properties, they aid in keeping aquatic birds and mammals dry. Lipids are also significant components of the plasma membrane and are the building blocks of numerous hormones. Fats, oils, waxes, phospholipids, and steroids are all lipids.

The most common type of lipid is a triglyceride, which includes fats from animals and oils from plants. Triglycerides generally function as long-term energy storage molecules, with the exception of refractory waxes, which are used instead as water repellents in both plants and animals. Triglycerides contain three saturated or unsaturated fatty acid chains bound to glycerol molecules. A saturated fatty acid chain is a linear molecule with the largest number of hydrogen atoms, and each carbon in the chain is connected by a single bond. Unsaturated fatty acid chains, on the other hand, are twisted due to the presence of at least one double bond. In addition, unsaturated fats can become “trans” fats when the hydrogen atoms around the double bond face each other. Trans fats occur naturally but are produced during the industrial production of hydrogen-saturated vegetable oils. Like saturated fats, trans fats are relatively linear and therefore stack very well. However, trans fats cause the following problems in human heart health: B. It damages the inner wall of the artery and causes inflammation during digestion.

Phospholipids are similar to triglycerides, but one of the fatty acid chains has been replaced by a phosphate-containing polar group. Therefore, phospholipids have a hydrophilic head and two hydrophobic fatty acid tails. These properties of phospholipids are important for the structure and function of cell membranes.

Steroids are lipids composed of condensed carbon rings with different functional groups. Cholesterol is a steroid that is also a component of cell membranes. In addition, cholesterol is used to synthesize other steroids, including sex hormones such as estrogen and testosterone. Cholesterol is essential for cell membrane structure and hormone synthesis, but high levels of plasma cholesterol are associated with the accumulation of plaque in blood vessels and the cause of coronary artery disease.

Lipids functions

Lipids serve as a store of primary energy. The excess energy after eating is digested and stored in adipose tissue. Fat can clog without water between molecules and can store more energy per unit than carbohydrates.

Lipids play an important role in regulating body function and signal transduction. Triglycerides maintain body temperature even when the outside temperature changes. Triacylglycerols help in the production of hormones. It also helps in the regulation of hormones. For example, adipose tissue produces leptin, which controls appetite. Fat supports the generation of nerve impulses, aids in the formation of nerve cell membranes, and allows electrical impulses to be transmitted in the brain.

Lipids also improve the absorption of fat-soluble molecules-improved absorption leads to increased bioavailability. Some phytochemicals, such as fat-soluble vitamins A, D, E, K, and lycopene, need to absorb fat effectively.

Glycerophospholipids form the major components of the structure of cell membranes and organelle membranes. Phospholipids improve the fluidity of cell membranes. Lipids also regulate the permeability of cell membranes.

Essential fatty acids such as linolenic acid and linolenic acid form eicosanoids such as thromboxane and prostaglandins. These play important roles in fever, pain, and blood clotting.

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 Nucleic acid

Nucleic acid is a macromolecule that is important for the continuation of life. They carry the genetic blueprint of the cell and carry instructions on how the cell functions. The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is a genetic material found in all living organisms,  from unicellular bacteria to multicellular mammals. RNA, another type of nucleic acid,  is primarily involved in protein synthesis. DNA molecules do not leave the nucleus but instead use  RNA mediators to communicate with the rest of the cell. Other types of RNA are also involved in protein synthesis and its regulation.

DNA and RNA are composed of monomers called nucleotides. Nucleotides combine together to form a polynucleotide, DNA, or RNA. Each nucleotide is composed of three components: a nitrogen base, a pentose sugar (5 carbons), and a phosphate group. Each nitrogen base of a nucleotide is attached to a sugar molecule that is attached to a phosphate group.

Functions of Nucleic acid.

Nucleotides are polymers on a nucleotide-by-nucleotide basis. Most biological processes require nucleotides. Nucleotides help repair the intestines, promote cell growth, and boost the immune system.

Nucleotides also promote muscle growth and detoxification. They also help maintain the regular metabolism of cells. Nucleotides prevent the body from being damaged by reactive oxygen species (ROS), in addition to enhancing the function of antioxidants.

DNA encodes a protein. It is deciphered by the messenger and broken down into single strands copied into RNA.

DNA replication supports functions such as cell and tissue growth and maintenance. During replication, the DNA strands unravel, and some bases remain unpartnered along the molecule. The unpaired base is then added to the free base, forming a new strand that complements the original strand. This will create a strand similar to the original strand before thawing. The result is two pairs of coiled DNA strands. DNA passes genetic information from one generation to the next (heredity). This is based on the fact that chromosomes are made from genes, and genes are made from DNA.

Messenger RNA is responsible for transcribing the DNA code into a format that can be read and used for protein synthesis. Ribosome RNA is composed of two subunits. The small subunit deciphers the genetic information of mRNA, and the large subunit binds amino acids to form a polypeptide chain. Ribosome RNA also binds to cytoplasmic proteins, resulting in ribosomes where protein synthesis takes place. Therefore, ribosomal RNA directs the translation of mRNA. Transfer RNA pairs anticodons and mRNA codons and carries the amino acids encoded by messenger RNA. Apart from its role in protein synthesis, RNA improves thermoregulation, improves cognition, and has antiviral, anti-aging, and anti-aging properties.

Biological Tests for Food Macromolecules


Procedure 1: Reducing Sugars

Benedict’s reagent can be used to detect reducing sugars and is a good indicator of the presence of some carbohydrates. The copper ions (Cu2+) in Benedict’s reagent are reduced by the monosaccharide functional groups (i.e., CHO or -C=O) to create cuprous oxide at a basic/alkaline pH (8-14). The Benedict’s reagent is reduced while the reducing sugar is oxidized in Benedict’s test for reducing sugars. With precipitation, this redox reaction produces a tractable color shift from a light blue solution to a green or reddish-orange solution. The amount of reducing sugar present is determined by the intensity of the color shift. A semi-quantitative test is what it’s termed.


•7 test tubes

•1-250ml Beaker


•Benedict’s Reagent

•Hot Plate


•Potato juice



•Starch Solution

•Reducing Sugar

Examine Reducing Sugars:

1. Obtain six test tubes and label them 1 through 6 with a wax pencil.

2. Add the test materials listed in Table 1 to each of your tubes.

3. Half fill a 250mL beaker with water. Place it on the hot plate at your station and allow it to come to a      gentle boil, designating 1 lab-group member as the “watcher.”

4. In the meantime, predict the color changes you expect to occur in each tube according to what you now know about carbohydrates from the lecture and record them in Table 1 in the “Benedict’s Test Results . Expected (color)” column. Also, as indicated in the Materials list, mark which tube you think is a positive control and which is the negative control.

5. Add 2mL of Benedict’s reagent to each tube.

6. Place all six tubes in the gently boiling water bath for 3 minutes, with the “watcher” doing their job of observing the tubes for any change in color and for even but controlled boiling during this time.

7. After 3 minutes, remove the tubes with your test tube holder and allow them to cool to room temperature in the tube rack. Record the color of each tube in Table 1 in the “Benedict’s Test Results Observed (color)”column.

Table 1

  Tube #  SolutionBenedict’s Test Results
Expected (color)Observed (color)
  110 drops potato juice  
  210 drops sucrose  
  310 drops glucose  
  410 drops distilled water  
  510 drops reducing sugar  
  610 drops starch  

The presences of reducing sugars reduce the blue copper sulphate from Benedict’s solution to a red-brown copper sulphide, which is seen as the precipitate and is responsible for the color change. 

When the solution turns red-brown means that the reducing sugars are present.


Procedure 2: Starch

Unlike the simpler mono- and disaccharides, starch is a structurally complex polymer. Iodine (iodine-potassium iodide, I2KI) reacts with the three-dimensional (3D) structure of this molecule, resulting in a color change (going from yellow to purple to blue-black) in a semi-quantitative manner.


7 test tubes



Potato juice



Reducing Sugar

Starch Solution



1. Obtain six test tubes and label them 1 through 6.

2. Add the materials listed in Table 2 to each of your tubes.

3. Predict the color changes you expect to occur in each tube and record them in Table 2 in the “Iodine Test Results Expected (color)” column. Also, mark which tube you think is a positive control and which is the negative control.

4. Add 8 drops of iodine to each tube.

5. Record the color of each tube in Table 2 in the “Iodine Test Results Observed (color)” column.

Table 2

  Tube #  SolutionIodine Test Results  
Expected (color)Observed (color)
  110 drops potato juice  
  210 drops sucrose  
  310 drops glucose  
  410 drops distilled water  
  510 drops reducing sugar  
  610 drops starch  

 The presence of starch will change the color of the solution to a blue-black color, indicating starch has been present.


Proteins are composed of amino acids covalently linked by peptide bonds. All amino acids contain an amino group (-NH2), a carboxyl group (-COOH), and a unique side chain (R-group) by which they are categorized. Peptide bonds (O=C-N-H) form when the amino group of one amino acid reacts with the carboxyl group of another. The Biuret reagent, regularly colored blue, is used to identify proteins. When the copper ions (Cu2+) in the reagent interact with peptide bonds, violet color is produced. In order for the interaction between Cu2+ and

the peptide bonds to result in a color change, a minimum of 4-6 peptide bonds is required.

The longer the protein polypeptide chain, the greater the intensity of the reaction; thus, this test is also semi-quantitative.


5 test tubes




Amino Acid solution

Egg Albumen

Protein Solution

Procedure 3: Biuret test for protein

1. Obtain 4 test tubes and label them 1-4.

2. Add the substances listed in Table 3 to each test tube.

3. Predict the color changes you expect to occur in each tube and record them in Table 2 in the “Expected Results (color)” column. Also, mark which tube you think is a positive control and which is the negative control.

4. Add 2mL of 2.5% sodium hydroxide, followed by 3 drops of Biuret reagent, and mix.

5. Record the color of each tube in Table 3 in the “Observed Results (color)” column.

Table 3:

Tube #SolutionExpected Results (color)Observed Results (color)
  12mL egg albumen  
  22mL amino acid solution  
  3  2mL distilled water  
  4  2mL protein solution  

The presence of protein will change the color of the solution to a purple color, indicating protein has been present.

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Lipids, which include triglycerides (fats), steroids, waxes, and oils, vary in

function. Similar to carbohydrates, fatty acids bond to glycerol with the input of

energy and the formation of water. While triglycerides and oils serve as energy-

storage molecules, phospholipids aggregate to form cellular membranes, which are an important source of cholesterol, a necessary component of steroid hormones.

All lipids share one characteristic; they are insoluble in water (i.e., hydrophobic) because they have a high proportion of non-polar carbon-hydrogen bonds and can only dissolve in non-polar solvents such as ether, ethanol, and acetone. This property can be used to test unknown solutions for the presence of lipids.


2 test tubes




Vegetable oil

Procedure 4: Lipids test #1

1. Obtain two test tubes and label them 1 and 2.

2. In this exercise, you will assess the solubility of lipids in polar and non-polar solvents. Predict what you expect to occur in each tube and record your predictions in Table 4 in the “Expected Results” column.

3. Add 1mL of vegetable oil to each tube, followed by the solutions listed in Table 4. Record your observations in Table 4 in the “Observed Results” column.

Table 4:

Tube #SolutionExpected ResultsObserved Results
  15mL water  
  25mL acetone  

Lipids are insoluble in water and soluble in water but soluble in any organic solvent.


Salad oil: both EVO and Olive oil

Fat-free and regular mayonnaise

Peanut butter


Known Lipid


Brown paper squares

Procedure 5: Lipids test #2

1. Obtain squares of brown paper.

2. In this exercise, you will test whether each solution is a lipid. Predict what you expect to occur and record your predictions in Table 5 in the “Expected Results” column.

3. Add 1 drop of each solution listed in Table 5 to the brown paper. Then, label each spot with a pen or pencil so that you can keep track.

4. Hold the brown paper up to the light, and if the solution is a lipid, the area where the drop soaks in will be translucent (see-thru). If the solution is not a lipid, it will just look like wet brown paper.

5. Record your observations in Table 5 in the “Observed Results” column.

Brown paper spotsExpected ResultsObserved Results
  1 = Extra Virgin Olive oil  
  2 = Olive oil  
3 = Honey  
4 = Mayonnaise  
5 = Fat free mayonnaise  
6 = Peanut butter  
4 = Known lipid  

Spot of paper with lipid will be translucent, indicating the presence of lipids.

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