Biomolecules
Can you recall? Page No. 59
1. Which are different cell components?
Answer: The different cell components include the cell membrane, nucleus, cytoplasm, mitochondria, chloroplasts (in plant cells), endoplasmic reticulum, Golgi apparatus, lysosomes, ribosomes, and cell wall (in plant cells).
2. What is the role of each component of cell?
Answer:
- Cell membrane: Regulates entry and exit of substances, maintains cell integrity.
- Nucleus: Stores genetic material (DNA), controls cell activities.
- Cytoplasm: Site of metabolic reactions, contains organelles.
- Mitochondria: Produces ATP via cellular respiration.
- Chloroplasts: Conducts photosynthesis in plant cells.
- Endoplasmic reticulum: Synthesizes proteins (rough ER) and lipids (smooth ER).
- Golgi apparatus: Modifies, packages, and transports proteins/lipids.
- Lysosomes: Degrades waste materials.
- Ribosomes: Synthesizes proteins.
- Cell wall: Provides structural support in plant cells.
Can you tell? Page No. 62
1. Enlist the natural sources, structural units, and functions of the following polysaccharides:
a. Starch
- Natural Source: Plants (e.g., potatoes, grains).
- Structural Units: α-glucose.
- Function: Energy storage in plants, broken down to glucose for energy.
b. Cellulose
- Natural Source: Plant cell walls (e.g., cotton, wood).
- Structural Units: β-glucose.
- Function: Structural component, provides rigidity and strength to plant cell walls.
c. Glycogen
- Natural Source: Animal liver and muscles.
- Structural Units: α-glucose.
- Function: Energy storage in animals, hydrolyzed to glucose as needed.
2. The exoskeleton of insects is made up of chitin. This is a …….
a. mucoprotein b. lipid
c. lipoprotein d. polysaccharide
Answer: d. polysaccharide
(Chitin is a heteropolysaccharide composed of N-acetylglucosamine units.)
3. List names of structural polysaccharides
Answer:
- Cellulose (plant cell walls).
- Chitin (insect exoskeletons, fungal cell walls).
- Peptidoglycan (bacterial cell walls).
- Hyaluronic acid (connective tissues).
4. What are carbohydrates?
Answer: Carbohydrates are biomolecules made of carbon, hydrogen, and oxygen (general formula: Cx(H2O)y), with a hydrogen-to-oxygen ratio of 2:1, serving as energy sources, structural components, and storage molecules.
5. Write a note on disaccharide and glycosidic bond.
Answer: Disaccharides are carbohydrates formed by the condensation of two monosaccharides, releasing a water molecule, and are linked by a glycosidic bond (a covalent bond between the hydroxyl groups of sugars). Examples include sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two glucose units). They are soluble in water, broken down in the small intestine into monosaccharides for energy, with sucrose being non-reducing and lactose/maltose being reducing sugars.
Find out Page No. 63
1. Why do high cholesterol levels in the blood cause heart diseases?
Answer: High cholesterol levels in the blood can lead to the buildup of cholesterol plaques in arteries, a condition known as atherosclerosis. These plaques narrow and harden the arteries, restricting blood flow to the heart, which can cause heart diseases such as coronary artery disease or heart attacks. Additionally, cholesterol deposits may contribute to inflammation and clot formation, further increasing the risk.
2. Polyunsaturated fatty acids are believed to decrease blood cholesterol levels. How?
Answer: Polyunsaturated fatty acids (PUFAs), such as linoleic acid, help reduce blood cholesterol by increasing the activity of enzymes that metabolize cholesterol in the liver. They also promote the formation of high-density lipoproteins (HDL), which remove excess cholesterol from the bloodstream. By replacing saturated fats in the diet, PUFAs lower low-density lipoproteins (LDL), reducing overall cholesterol levels.
Can you tell? Page No. 63
1. Differentiate between the saturated and unsaturated fats.
Answer: Saturated Fats:
- Structure: No double bonds between carbon atoms in the fatty acid chain, fully saturated with hydrogen.
- Physical State: Solid at room temperature (e.g., butter, lard).
- Examples: Palmitic acid, stearic acid.
- Health Impact: Can increase blood cholesterol levels, raising heart disease risk.
Unsaturated Fats:
- Structure: Contain one or more double bonds in the fatty acid chain, reducing hydrogen saturation.
- Physical State: Liquid at room temperature (e.g., oils).
- Examples: Oleic acid (monounsaturated), linoleic acid (polyunsaturated).
- Health Impact: Help lower bad cholesterol (LDL), beneficial for heart health.
2. What are lipids? Classify them and give at least one example of each.
Answer: Definition: Lipids are greasy substances with long hydrocarbon chains containing carbon, hydrogen, and oxygen, with a hydrogen-to-oxygen ratio greater than 2:1, soluble in non-polar solvents, serving as energy stores, structural components, and signaling molecules.
Classification:
- Simple Lipids: Esters of fatty acids with alcohols.
- Example: Triglycerides (fats, e.g., vegetable oil), Waxes (e.g., beeswax).
- Compound Lipids: Contain additional groups like phosphate or sugar.
- Example: Phospholipids (e.g., lecithin), Glycolipids (e.g., cerebrosides).
- Derived Lipids: Derived from simple or compound lipids.
- Example: Cholesterol (sterol).
Can you tell? Page No. 64
1. All proteins are made up of the same amino acids; then how proteins found in human beings and animals may be different from those of other ?
Answer: Proteins in humans and animals differ from those in other organisms due to variations in the sequence, number, and arrangement of the same 20 amino acids in their polypeptide chains. These differences lead to unique primary, secondary, tertiary, and quaternary structures, which determine specific functions, such as hemoglobin in humans versus chlorophyll-binding proteins in plants. Genetic variations across species further contribute to the diversity in protein structure and function.
2. What are conjugated proteins? How do they differ from simple ones? Give one example of each.
Answer: Conjugated proteins consist of a simple protein combined with a non-protein prosthetic group, enabling specialized functions, e.g., haemoglobin (globin protein + haem). Simple proteins, on the other hand, yield only amino acids upon hydrolysis and lack a prosthetic group, e.g., albumin (egg albumin). The key difference is the presence of a non-protein component in conjugated proteins, which imparts additional functionality compared to the purely amino acid-based simple proteins.
3. Which of the following is a simple protein
a. nucleoprotein
b. mucoprotein
c. chromoprotein
d. globulin
Answer: d. globulin
Explanation:
- Nucleoprotein: Conjugated protein (protein + nucleic acid).
- Mucoprotein: Conjugated protein (protein + carbohydrate).
- Chromoprotein: Conjugated protein (protein + pigment, e.g., haem).
- Globulin: Simple protein, yields only amino acids on hydrolysis, found in blood and tissues.
Can you tell? Page No. 67
1. Describe the structure of DNA molecule as proposed by Watson and Crick.
Answer: Watson and Crick proposed that DNA is a double helix composed of two antiparallel polynucleotide strands twisted around each other, with a sugar-phosphate backbone on the outside and nitrogenous bases paired inside. The strands are held together by hydrogen bonds (adenine pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds), with one complete turn of the helix measuring 34 Å, a nucleotide spacing of 3.4 Å, and a diameter of 20 Å. The 3′ end of one strand aligns with the 5′ end of the other, ensuring complementary base pairing for genetic stability and replication.
2. Difference between DNA and RNA is because of
a. sugar and base
b. sugar and phosphate
c. phosphate and base
d. sugar only
Answer: a. sugar and base
- Explanation: DNA contains deoxyribose sugar and thymine as a base, while RNA contains ribose sugar and uracil instead of thymine.
3. Differentiate between DNA and RNA.
Answer: DNA:
- Sugar: Deoxyribose.
- Strands: Double-stranded, forming a double helix.
- Bases: Adenine, thymine, guanine, cytosine.
- Function: Hereditary material, stores genetic information.
- Location: Primarily in the nucleus, also in mitochondria and chloroplasts.
RNA:
- Sugar: Ribose.
- Strands: Single-stranded, may fold or be double-stranded in some viruses.
- Bases: Adenine, uracil, guanine, cytosine.
- Function: Involved in protein synthesis (mRNA, rRNA, tRNA).
- Location: Synthesized in the nucleus, functions in the cytoplasm.
4. What is nucleotide? How is it formed? Mention the names of all nucleotides.
Answer:
- Definition: A nucleotide is the basic unit of nucleic acids, consisting of a 5-carbon sugar, a phosphate group, and a nitrogenous base.
- Formation: A nucleotide is formed when a nitrogenous base attaches to the 1′ carbon of the sugar (forming a nucleoside), and a phosphate group attaches to the 5′ carbon of the sugar.
- For example, in DNA, adenine binds to deoxyribose to form deoxyadenosine, which combines with a phosphate to form deoxyadenosine monophosphate (dAMP).
Names of Nucleotides:
- DNA Nucleotides: Deoxyadenosine monophosphate (dAMP), Deoxythymidine monophosphate (dTMP), Deoxyguanosine monophosphate (dGMP), Deoxycytidine monophosphate (dCMP).
- RNA Nucleotides: Adenosine monophosphate (AMP), Uridine monophosphate (UMP), Guanosine monophosphate (GMP), Cytidine monophosphate (CMP).
Can you tell? Page No. 70
1. Which enzyme is needed to digest food reserve in caster seed?
a. amylase b. diastase
c. lipase d. protease
Answer: c. lipase
- Explanation: Castor seeds store lipids (oils) as their primary food reserve, and lipase is the enzyme required to break down these lipids into fatty acids and glycerol for energy.
2. Co-enzyme is ———
a often a metal b. often a vitamin
c. always as organic molecule
d. always an inorganic molecule
Answer: b. often a vitamin
- Explanation: Co-enzymes are organic compounds, often derived from vitamins (e.g., nicotinamide adenine dinucleotide (NAD) from vitamin B3), that are tightly bound to enzymes and assist in their catalytic activity.
3. List the important properties of enzymes.
Answer:
- Proteinaceous Nature: Most enzymes are proteins, except ribozymes (RNA-based).
- Three-Dimensional Conformation: Enzymes have specific 3D structures with active sites for substrate binding.
- Catalytic Property: Enzymes speed up biochemical reactions without being consumed, remaining unchanged after the reaction.
- Specificity of Action: Each enzyme catalyzes a specific reaction or group of substrates (e.g., sucrase acts on sucrose).
- Sensitivity to Temperature and pH: Enzymes have optimal temperature (20–35°C) and pH (e.g., pepsin at pH 2), with activity declining outside these ranges.
- High Efficiency: A small amount of enzyme can catalyze the transformation of a large quantity of substrate (e.g., sucrase hydrolyzes 100,000 times its weight in sucrose).
4. Name the chemical found in the living cell which has necessary message for the production of all enzymes required by it.
Answer: DNA found in the nucleus of a living cell has necessary message for the production of all enzymes required by it. DNA forms mRNA through the process of transcription. This mRNA through the process of translation forms proteins.
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