All Free Biology MCQs with Answers

• A. Glucose
• B. Galactose
• C. Fructose
• D. Ribose

Explanation: Glycogen is a storage form of glucose primarily found in the liver and muscle tissues. It is a polysaccharide made up of long chains of glucose units linked together. During hydrolysis, these glucose units are released as the glycosidic bonds are broken. The other options, such as galactose, fructose, and ribose, are different types of sugars not related to glycogen's composition.

• A. Polysaccharides
• B. Monosaccharides
• C. Oligosaccharides
• D. Sucrose

Explanation: The correct answer is monosaccharides. Monosaccharides, such as glucose and fructose, are the simplest form of carbohydrates and cannot be broken down into simpler sugars through hydrolysis. In contrast, polysaccharides are complex carbohydrates that consist of multiple monosaccharide units and can be hydrolyzed into simpler sugars. Oligosaccharides, being composed of a few monosaccharide residues, can also be hydrolyzed. Similarly, sucrose, a disaccharide, can be hydrolysed into glucose and fructose.

• A. Phosphodiester bond
• B. Peptide bond
• C. Ionic bond
• D. Glycosidic bond

Explanation: The correct answer is the glycosidic bond, which is the covalent bond that forms between two monosaccharide subunits, allowing them to link together to form larger carbohydrate molecules like disaccharides and polysaccharides. This bond is crucial in the formation of complex carbohydrates. The other options are incorrect: phosphodiester bonds connect nucleotides in DNA and RNA, peptide bonds connect amino acids in proteins, and ionic bonds occur between charged ions, not between sugar molecules.

• A. Green vegetables
• B. Grapes
• C. Rice
• D. All of these

Explanation: Green vegetables, such as spinach, kale, and broccoli, are excellent for diabetic control because they are low in carbohydrates and sugar, and they have a low glycemic index, which means they do not cause significant spikes in blood sugar levels. In contrast, grapes and rice have higher sugar and carbohydrate content, which can lead to increased blood sugar levels. Therefore, green vegetables are the best choice for managing diabetes.

• A. Grains
• B. Fruits and tubers
• C. Seeds
• D. All of the above

Explanation: The correct answer is all of these. Grains, fruits, tubers, and seeds all contain starch, though the concentration and prominence as a dietary source vary. Grains such as rice and wheat are staple sources of starch in many diets, while tubers like potatoes and certain fruits like bananas are also significant contributors. Seeds may contain starch, but they are generally not as prominent a source compared to grains and tubers. Hence, all the listed options contribute to starch intake.

• A. Lactose
• B. Sucrose
• C. Glucose
• D. Maltose

Explanation: Table sugar is chemically known as sucrose, which is a disaccharide made from one molecule of glucose and one molecule of fructose. It is the most common form of sugar used in cooking and baking. Lactose is not the correct answer, as it is found in milk. Glucose, a monosaccharide, is a single sugar unit and not the composition of table sugar. Maltose is also incorrect, as it consists of two glucose units and is typically found in malted beverages.

• A. Cellulose
• B. Galactose
• C. Sucrose
• D. Starch

Explanation: In plant cells, excess glucose is primarily stored as starch, which is a polysaccharide. This allows plants to store energy for later use. Starch is the correct answer because it serves as the primary storage form of glucose in plants.Cellulose, on the other hand, is used to construct plant cell walls and does not serve as an energy storage molecule. Galactose is a simple sugar that is not used for storage in plants. Sucrose is used for the transport of sugars but not for long-term storage.

• A. Lactose
• B. Sucrose
• C. Glucose
• D. Fructose

Explanation: The correct answer is lactose, which is not typically found in plants. Lactose is a sugar found in milk, produced by mammals, and is not a component of plant biology. In contrast, sucrose, glucose, and fructose are all sugars that are commonly found in plants. Sucrose is often extracted from sugarcane and sugar beets, glucose is a fundamental sugar in cellular respiration and photosynthesis, and fructose is abundant in fruits.

• A. Iodine test
• B. Benedict's test
• C. Biuret test
• D. Sudan III test

Explanation: Among the listed tests, only the iodine test detects starch by producing a blue-black colour. This occurs because iodine molecules fit into the helical structure of amylose, forming a coloured complex. The other tests-Benedict's for sugars, Biuret for proteins, and Sudan III for lipids-are specific to different types of biomolecules and do not detect starch.

• A. Nucleic acids
• B. Actin filaments
• C. Lipids
• D. Carbohydrates

Explanation: Carbohydrates are the correct answer because they are often referred to as 'carbon-water' molecules due to their chemical composition. They are made up of carbon, hydrogen, and oxygen, often in the ratio of Cn(H2O)n, which makes them an immediate source of energy in the form of sugars. Nucleic acids, actin filaments, and lipids serve different roles in the body and are not primarily used as immediate energy sources like carbohydrates.