Organic compounds

The chemicals found in living things are called organic compounds because they contain carbon and are related to life. Among the numerous types of organic compounds, four major categories are found in all living things: They are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

Carbohydrates are a crucial class of organic compounds essential for energy provision and structural functions in living organisms.

Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the ratio of hydrogen atoms to oxygen and carbon atoms is 2:1.

Carbohydrates consist of smaller units called saccharides and are classified into three groups based on the number of saccharide units they contain.

Structure and Classification of Carbohydrates

1, Monosaccharides (Single Sugars)

Monosaccharides are the simplest form of carbohydrates, consisting of single sugar molecules. They are the building blocks for more complex carbohydrates. Examples of monosaccharides include:

• Glucose: The most important monosaccharide is glucose, a carbohydrate and a primary energy source for cells. Glucose is the basic form of fuel in living things.
• Fructose: Found in fruits and honey, often combined with glucose in various forms of sugar.
• Galactose: A component of lactose, found in milk.

2, Disaccharides (Double Sugars)

Disaccharides consist of two monosaccharide molecules linked together. They are formed through a dehydration reaction, where a water molecule is removed during the bonding process. Examples of disaccharides include:

• Maltose: Composed of two glucose molecules, found in malted foods and beverages.
• Sucrose: Common table sugar, composed of glucose and fructose.
• Lactose: Found in milk, composed of glucose and galactose

3, Polysaccharides (Many Sugars)

Polysaccharides are long chains of monosaccharide units linked together. They serve various functions such as energy storage and providing structural support. Examples of polysaccharides include:

• Starch: A storage form of glucose in plants, found in foods like potatoes and grains.
• Glycogen: A storage form of glucose in animals, stored primarily in the liver and muscles.
• Cellulose: A structural component of plant cell walls, indigestible by humans but important for dietary fiber.

Test for Carbohydrates: Glucose

Benedict’s Solution Test

The Benedict’s test is a simple method to detect the presence of glucose, a reducing sugar, in a solution. Benedict’s solution is a blue liquid that changes color when it reacts with reducing sugars like glucose.

Materials:

• Benedict’s solution (blue liquid)
• Sample solution (e.g., fruit juice)
• Test tube
• Water bath
• Heat source

Procedure:

1. Prepare a Water Bath: Heat some water in a container to create a water bath.
2. Measure Benedict’s Solution: Pour 5 cm³ of Benedict’s solution into a test tube.
3. Add Test Solution: Add a few drops of the sample solution (e.g., fruit juice) to the test tube with Benedict’s solution.
4. Heat the Mixture: Place the test tube into the water bath. Ensure the water is hot but not boiling.
5. Observe the Color Change: After a few minutes, observe the color change in the solution.

Results Interpretation:

• Blue: No glucose present.
• Green: Trace amounts of glucose.
• Yellow: Moderate amount of glucose.
• Orange-Red: High concentration of glucose.

Test for Carbohydrates: Starch

The Iodine Solution Test
The iodine test is used to detect the presence of starch in a sample. Iodine solution is a brown liquid that changes color when it comes into contact with starch.

Below are the Materials used
a, Iodine solution (brown liquid)
b, Sample (e.g., peeled potato or piece of bread)
c, Dish or plate
d, Dropper

The Procedure to follow:
1, Prepare the Sample: Place a peeled potato or a piece of bread on a dish or plate.
2, Add Iodine Solution: Using a dropper, place a few drops of iodine solution on the sample.
3, Observe the Color Change: Look for a color change in the sample where the iodine solution was applied.
4, Results Interpretation:
No color change (brown): means there is no starch present in the sample.
Blue/Black: means starch is present.

Lipids (Fats and Oils)

Lipids (fats and oils) are organic compounds, essential for various biological functions, including providing energy for living organisms, insulating body organs, and transporting fat-soluble vitamins through the blood. They also play a crucial role in cell membrane structure. Lipids are hydrophobic, meaning they do not dissolve in water, but they are soluble in non-polar solvents such as Hexane. Diethyl ether, Toluene, Chloroform and Benzene. Examples of lipids include cooking oils like sunflower oil, butter and margarine.

Lipids are composed of carbon, hydrogen, and oxygen, with the ratio of hydrogen to oxygen being greater than 2:1. Structurally, a lipid molecule consists of one glycerol molecule bonded to three fatty acid molecules.

Types of Lipids

1, Saturated fats

Saturated fats are characterized by single bonds in the fatty acid chains and are predominantly derived from animal sources. These fats are typically solid at room temperature, so foods like butter and cheese remain firm when not heated. The structure of saturated fats allows them to pack tightly together, contributing to their solid state.

2, Unsaturated fats,
Unsaturated fats, on the other hand, have one or more double bonds in the fatty acid chains and are mainly derived from plant sources. These double bonds create kinks in the fatty acid chains, preventing the molecules from packing closely together, which is why unsaturated fats are usually liquid at room temperature. Examples of unsaturated fats include olive oil, canola oil, and sunflower oil, all of which remain liquid and are commonly used in cooking and food preparation.

Cholesterol and heart disease:

Cholesterol is a lipid that appears as a white, wax-like substance in the human body and is a vital component of cell membranes. However, excessive intake of saturated fats can lead to elevated cholesterol levels in the blood. When cholesterol levels are too high, it can cause fatty deposits to form in the arteries, a condition known as atherosclerosis.

These fatty deposits narrow the arteries, restricting blood flow and increasing the risk of cardiovascular problems. This interference with blood transport can ultimately lead to serious health issues, including heart attacks.

For example, consuming large amounts of foods high in saturated fats, such as butter and fatty meats, can significantly raise cholesterol levels, highlighting the importance of a balanced diet for heart health.

Steps to Test for Fats

1, Grind the Test Material: Begin by grinding the test material, such as peanuts, to increase its surface area.

2, Add Solvent: Place a small amount of the ground material into a test tube and add about 5 cm³ of ether or ethanol.

3, Shake and Stand: Shake the test tube thoroughly and let it stand for a few minutes to allow the fat to dissolve into the solvent.

4, Filter the Solution: Filter the solution to remove any solid particles.

5, Apply Filtrate: Place a few drops of the filtrate (the liquid that has passed through the filter) onto a clean piece of filter paper.

6, Observe: Allow the ether or ethanol to evaporate. A translucent, greasy stain will form on the filter paper if fats are present in the test material.

Proteins.

Proteins are complex molecules consisting of carbon, hydrogen , oxygen , and nitrogen. Additionally, some proteins may contain phosphorus, sulfur, and iron, contributing to their diverse functions and structures.

Structure:

Proteins are constructed from long chains of smaller units called amino acids, which serve as the fundamental building blocks, or monomers, of proteins. These amino acid chains fold into intricate three-dimensional shapes, which are crucial for their specific functions.

Amino Acids:

There are approximately 20 different types of amino acids found in proteins. Each amino acid has a unique structure and side chain, known as the R-group, which determines its properties and interactions within a protein molecule.

Sequence and Type:

The sequence and type of amino acids within a protein chain dictate its overall structure and function. The specific arrangement of amino acids influences the protein’s shape, stability, and ability to interact with other molecules in biological processes.

Peptide Bond:

The bond that forms between two amino acids is known as a peptide bond. This bond is essential for the formation of protein structures and the stability of the protein molecule.

Peptide Formation:

When two amino acids join together through a peptide bond, they form a dipeptide. Similarly, the combination of three amino acids results in a tripeptide. A polypeptide refers to a longer chain of amino acids linked by multiple peptide bonds, ultimately forming a protein molecule with its unique structure and function.

In the polypeptide diagram above, amino acids are shown as separate or individual units connected by peptide bonds.

A peptide bond is a linkage formed between two amino acids. on the other hand, a polypeptide chain is a longer, continuous, unbranched chain of amino acids linked by peptide bonds.

A protein consists of a chain of at least 50 or more amino acids. These amino acid chains are highly sensitive to changes in temperature and pH levels. When exposed to high temperatures or extreme pH conditions, proteins can denature, meaning they lose their specific shape and, consequently, their functionality. This loss of structure disrupts the protein’s ability to perform its biological functions effectively.

Steps to Test for Proteins using the Biuret test

1, Grind the Test Material: Grind the test material, such as beans, and add a small amount of water.
2, Boil the Mixture: Boil the ground material until it forms a thin soup.
3, Transfer to Test Tube: Pour about 5 cm³ of the soup into a test tube.
4, Add Copper Sulphate: Add a few drops of dilute copper sulphate solution to the test tube.
5, Add Sodium Hydroxide: Add 5 cm³ of sodium hydroxide solution to the mixture.
6, Shake and Heat: Shake the test tube thoroughly and then heat the mixture.
7, Observe Colour Change: A violet (purple) colour indicates the presence of proteins, while a blue colour means proteins are absent.

Enzymes

Enzymes are a type of protein that play a crucial role in various biological processes. As biological catalysts, enzymes speed up the rate of chemical reactions without being consumed in the process. This means they can be used repeatedly to facilitate numerous reactions.

In living cells, chemical reactions are known as metabolic reactions, which are essential for maintaining life. Enzymes are involved in two main types of metabolic reactions: anabolic and catabolic reactions.

Anabolic Reactions: In these reactions, enzymes help build complex molecules from simpler ones. An example of an anabolic reaction is the synthesis of proteins from amino acids.

Catabolic Reactions: In these reactions, enzymes assist in breaking down complex molecules into simpler ones. For instance, during digestion, enzymes break down large food molecules into smaller, more easily absorbed molecules. This process is essential for converting the food we eat into usable energy and nutrients.

Without enzymes, these metabolic reactions would occur too slowly to sustain life. For example, the digestion of food relies heavily on enzymes to break down complex molecules like carbohydrates, proteins, and fats into simpler molecules that the body can absorb and use. Without these enzymes, the body wouldn’t be able to efficiently process and utilize the nutrients from food.

Enzymes are therefore vital to both the synthesis and breakdown of molecules in the body, ensuring that all necessary biochemical processes occur swiftly and efficiently.

Lock-and-Key Model of Enzyme Action

The lock-and-key model is a concept used to explain how enzymes function as biological catalysts, ensuring that specific biochemical reactions occur efficiently and accurately. In this model, the substance on which an enzyme acts is known as the substrate. Each enzyme is designed to be specific to a particular substrate, meaning that only certain substrates will fit into an enzyme’s active site. This specificity ensures that enzymes only catalyze their intended reactions.

When a substrate binds to an enzyme, it forms an enzyme-substrate complex. This binding is highly specific, akin to how a key fits precisely into a lock. The active site of the enzyme provides a perfect fit for the substrate, allowing the enzyme to catalyze the reaction effectively. During the reaction, the enzyme facilitates the conversion of the substrate into the product, the substance formed as a result of the enzymatic reaction.

Once the product is formed, it leaves the enzyme’s active site. The enzyme itself remains unchanged and is free to bind with new substrate molecules, repeating the process. This reusability of enzymes is a key feature that makes them highly efficient as catalysts. The lock-and-key model highlights the precision and specificity of enzyme activity, which is essential for maintaining the proper functioning of biological systems.

Here are the key points about this model:

1, The substance on which an enzyme acts is called the substrate. Each enzyme is specific to a particular substrate.

2, The substance formed as a result of the enzymatic reaction is known as the product.

3, Enzymes are substrate-specific, meaning that a particular enzyme can only react with a specific substrate. For example, the enzyme sucrase will only react with the substrate sucrose.

4, The substrate fits precisely into the enzyme’s active site, similar to how a key fits into a lock. When the substrate and enzyme bind together, they form an enzyme-substrate complex.

5, Once the enzyme-substrate complex is formed, the enzyme catalyzes the reaction, converting the substrate into the product. After the reaction, the product leaves the enzyme.

6, After the product is released, the enzyme is free to bind with new substrate molecules and repeat the process.

Effect of Temperature on Enzyme Activity

The activity of enzymes is greatly influenced by temperature variations, making them highly sensitive to such changes. Here are the key points to understand:

Sensitivity to Temperature: Enzymes are proteins that can only function properly within a certain temperature range. Their activity is influenced by the surrounding temperature. Let’s look at how this works.

1, Low Temperature Inactivity: At low temperatures, most enzymes become inactive. This is because the molecules move more slowly and there is less energy available for reactions to occur, resulting in a slower rate of enzymatic activity.

2, Optimum Temperature: Each enzyme has a specific temperature range at which it works most efficiently, known as its optimum temperature. For many enzymes in the human body, this is typically between 35 ºC and 40 ºC. At this temperature range, the enzyme’s structure is ideal for binding to substrates and catalyzing reactions at the fastest rate.

3, Denaturation at High Temperatures: When the temperature rises above the enzyme’s optimum level, the enzyme can lose its shape, a process known as denaturation. When an enzyme denatures, it loses its functional structure, making it unable to bind to substrates and catalyze reactions effectively. This loss of shape and function is usually irreversible.

Enzymes in Everyday Life

Enzymes play a vital role in everyday applications, particularly in household products like biological washing powders. These washing powders contain enzymes such as lipase and protease that help break down stains on clothing. Protease, for example, breaks down protein-based stains into smaller, soluble molecules, making it easier for cleaning agents in the washing powder to remove them. This enzymatic action enhances the effectiveness of washing powders, making them essential for removing tough stains.

Nucleic Acids

Nucleic acids are essential biomolecules made up of the elements carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P). There are two primary types of nucleic acids: namely DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

1, DNA: DNA is found in the nucleus of a cell and carries genetic information that determines hereditary characteristics. It provides instructions for building and maintaining an organism.

2, RNA: RNA is found in both the nucleus and the cytoplasm of a cell. It plays a crucial role in protein synthesis, acting as a messenger that carries the genetic code from DNA to the ribosomes, where proteins are made.

Vitamins
Vitamins are organic compounds that animals require in small quantities for various bodily functions. They are essential for normal metabolism, growth, and development. Without adequate vitamins, the human body cannot function properly, leading to deficiencies and health problems. Vitamins are obtained from a balanced diet and are crucial for maintaining overall health.

Vitamins, Their Sources, and Deficiency Diseases

1, Vitamin A
Vitamin A is found in yellow vegetables such as carrots and sweet potatoes, as well as in liver. This vitamin is essential for maintaining healthy vision, especially in low-light conditions. A deficiency in Vitamin A can lead to night-blindness, where individuals have difficulty seeing in the dark due to the impaired ability of the eyes to adjust to low light levels.

2, Vitamin B1 (Thiamine)
Vitamin B1, also known as thiamine, is abundant in brown rice, whole grain bread, and legumes like beans and lentils. This vitamin plays a crucial role in energy metabolism and the proper functioning of the nervous system. A deficiency in Vitamin B1 results in beriberi, a disease that affects the cardiovascular, nervous, and muscular systems. Symptoms of beriberi include weakness, pain, and heart problems, highlighting the importance of sufficient thiamine intake.

3, Vitamin C
Citrus fruits such as oranges and lemons, along with tomatoes, are excellent sources of Vitamin C. This vitamin is vital for the synthesis of collagen, wound healing, and the maintenance of healthy skin and blood vessels. A deficiency in Vitamin C leads to scurvy, a condition characterized by fatigue, swollen gums, joint pain, and anemia. .

4, Vitamin D
Vitamin D is predominantly found in oily fish like salmon and mackerel, as well as in fortified milk. This vitamin is essential for calcium absorption and bone health. A lack of Vitamin D can cause rickets in children, a disease that results in the softening and weakening of bones, leading to bone deformities.

5, Vitamin E
Leafy green vegetables such as spinach and lettuce are rich sources of Vitamin E. This vitamin acts as an antioxidant, protecting cells from damage and playing a role in maintaining healthy skin and eyes. A deficiency in Vitamin E can lead to poor nerve conduction and anemia.