Question

Which are incorrect statements? (a) amylose is a component of cellulose (b) starch is a polymer of \(\alpha\) - glucose (c) proteins are compounds of only one type of amino acids (d) in cyclic structure of fructose, there are four carbon atoms and one oxygen atom. (a) 1,2 and 4 (b) 1,3 and 4 (c) 1,2 and 3 (d) 2,3 and 4

Short answer

Incorrect: (a), (c), (d); therefore, choice (b) is correct.

Step-by-step solution

Analyze Statement (a)

Statement (a) claims that amylose is a component of cellulose. Amylose is actually a component of starch, not cellulose. Cellulose is composed of -linked -D-glucose units, whereas amylose is made up of -linked F-D-glucose units. Therefore, statement (a) is incorrect.

Analyze Statement (b)

Statement (b) claims that starch is a polymer of 6la;glucose. Starch indeed consists of two components: amylose and amylopectin, both of which are polymers of 6la;glucose. This statement is correct.

Analyze Statement (c)

Statement (c) says that proteins are compounds of only one type of amino acids. This is incorrect as proteins are composed of 20 different types of standard amino acids linked in varying sequences and combinations, not just one type.

Analyze Statement (d)

Statement (d) states that in the cyclic structure of fructose, there are four carbon atoms and one oxygen atom. In reality, the cyclic structure of fructose contains five carbon atoms and one oxygen atom in a furanose ring. Thus, statement (d) is incorrect.

Key concepts

Carbohydrates

Carbohydrates are vital biomolecules that serve numerous functions in living organisms, primarily as a source of energy and structural components. Their simplest forms, monosaccharides, are single sugar units such as glucose and fructose. Monosaccharides can join to form disaccharides like sucrose or further polymerize into larger carbohydrates, such as starch and cellulose.
Sugar units in carbohydrates are connected through glycosidic bonds, which affect the molecule's properties and biological roles. Starch, for instance, comprises amylopectin and amylose, both polymers of glucose, but with different linkages that impact their solubility and digestibility. Cellulose, another glucose polymer, contrasts starch by the orientation of its bonds, making it a robust structural component in plant cell walls.
Understanding these differences is crucial for comprehending how carbohydrates function as energy reserves, structural units, and regulatory molecules within various biological systems.

Amino Acids and Proteins

Amino acids are the organic compounds that play a critical role in the formation of proteins, the workhorses of cellular processes. There are 20 different standard amino acids found in nature, each possessing a unique side chain that contributes to its specific properties.
Proteins are essentially long chains of amino acids folded into complex three-dimensional shapes determined by their sequence. The variety of amino acids and their combinations allow for immense diversity in protein structure, enabling proteins to fulfill countless functions, including enzymatic reactions, cell signaling, and structural roles.

• Enzymes, a type of protein, catalyze biochemical reactions, making them crucial for life's processes.
• Proteins also provide structural integrity to living organisms; keratin and collagen are examples.
• Some proteins are involved in transporting molecules across cell membranes or facilitating immune responses.

The versatility and complexity of proteins arise from the different sequences and structures that amino acids can form, highlighting the importance of amino acids in biology.

Chemical Structure Analysis

Chemical structure analysis is a fundamental practice in organic chemistry that involves uncovering the arrangement of atoms within a molecule. This analysis is essential to understand the molecular function and reactivity of chemical compounds.
Several techniques are employed in chemical structure analysis, including:

• Nuclear Magnetic Resonance (NMR) Spectroscopy: Allows chemists to determine the structure by examining the magnetic properties of atomic nuclei.
• X-ray Crystallography: Provides a 3D visualization of molecular structures by analyzing the diffraction pattern of X-rays passing through a crystallized sample.
• Mass Spectrometry (MS): Helps identify molecular composition by measuring the mass-to-charge ratio of ionized particles.
• Infrared (IR) Spectroscopy: Utilizes the interaction of infrared light with molecules to identify functional groups.

Accurate structural determination is crucial for advancing fields such as drug development, where understanding molecular interactions can lead to the creation of new pharmaceuticals that target specific biological pathways.

Polysaccharides

Polysaccharides are complex carbohydrates composed of repeated sugar units, often fulfilling structural or energy storage roles within organisms. They are categorized based on their function and composition, with notable examples including starch, glycogen, and cellulose.

• Starch: A storage polysaccharide in plants, composed of amylose and amylopectin, both polymers of α-glucose. Starch is easily digested by humans due to the presence of α-linkages.
• Glycogen: Serves a similar energy storage function in animals and fungi, its highly branched structure allows for rapid energy mobilization.
• Cellulose: A structural polysaccharide found in plant cell walls, made of β-glucose units, and is not digestible by humans but provides fiber.
• Chitin: Found in the exoskeleton of arthropods and cell walls of fungi, it provides structural integrity like cellulose.

Polysaccharides' diverse roles and structures make them integral to both plant and animal physiology, highlighting their importance in nature and potential applications in industries like food, biofuels, and materials science.