CBSE Class 11 Biology Notes Chapter 9 Biomolecules

CBSE Class 11 Biology Notes Chapter 9: In CBSE Class 11 Biology Notes Chapter 9 about Biomolecules, you learn about the important molecules that make life possible. These molecules, like carbohydrates, lipids, proteins, and nucleic acids, are essential for many functions in living things.

CBSE Class 11 Biology Notes Chapter 9 Biomolecules Overview

CBSE Class 11 Biology Notes Chapter 9 Biomolecules PDF

CBSE Class 11 Biology Notes Chapter 9 PDF

CBSE Class 11 Biology Notes Chapter 9 Biomolecules

Biomolecules

Analysis of chemical composition

Proteins

Structure of amino acid

Formation of peptide bond

Primary Structure : This level refers to the linear sequence of amino acids linked together by peptide bonds.

Secondary Structure : At this stage, the protein begins to fold into more complex shapes, typically forming alpha-helices or beta-sheets. These structures are stabilized by hydrogen bonds between the carbonyl and amino groups along the polypeptide backbone.

Tertiary Structure : This level involves the three-dimensional arrangement of the entire protein molecule, including interactions between amino acid side chains. Stabilizing forces such as hydrophobic interactions, hydrogen bonds, electrostatic interactions, van der Waals forces, and covalent bonds help maintain the structure.

Quaternary Structure : Some proteins consist of multiple polypeptide chains that come together to form a functional protein complex. The interactions between these individual chains, such as hydrophobic interactions and hydrogen bonds, contribute to the quaternary structure. Examples include hemoglobin, which is composed of four subunits.

Levels of protein organization

• Fibrous Proteins : These proteins have an elongated, rod-like shape and are insoluble in water. They primarily serve structural and protective roles in the body.
• Globular Proteins : These proteins have a more spherical shape and are soluble in water. They perform a wide range of functions, including enzymatic activity, transport, and immune response.

Nucleic acids

Structure of nucleotide

Structure of Double-Stranded DNA

B DNA:

• The long polynucleotide strands coil around an axis.
• The two strands are arranged in an antiparallel manner, meaning they run in opposite directions.
• Adenine nucleoside base pairs with thymine, while guanine base pairs with cytosine.
• Adenine and thymine are held together by two hydrogen bonds, while guanine and cytosine are held together by three hydrogen bonds.

Z DNA:

• This DNA structure is thinner compared to B DNA.
• The purine and pyrimidine bases are arranged alternately.
• The DNA has a high salt concentration to stabilize its structure.

RNA

Carbohydrates

Some common saccharides

Structure of starch

In animals, energy is stored in the form of glycogen, mainly in muscle and liver tissues. Similar to starch, glycogen consists of two different polymers: amylose and amylopectin. It has a highly branched structure, as depicted in Fig. 9. Cellulose, another polysaccharide found in plant cells,  as a structural component. It is composed of unbranched polymer chains of glucose units, providing strength and rigidity to plant cells. Chitin is a linear polysaccharide found in the exoskeleton of insects and crustaceans. It is composed of N-acetyl-D-glucosamine residues. Reducing sugars, such as monosaccharides, have the ability to reduce ferric or cupric ions. In contrast, non-reducing sugars like sucrose lack this ability.

Lipids

Lipids are compounds that are poorly or completely insoluble in water but soluble in non-polar solvents like chloroform, ether, or benzene.

Biological Functions of Lipids

Lipids serve several important biological functions:

Energy Storage: Lipids are a primary storage form of energy in organisms. They can be stored in adipose tissue and mobilized when energy is needed, providing a long-term energy reserve.

Structural Component of Membranes: Lipids, particularly phospholipids, are essential components of cell membranes. They form the lipid bilayer, which provides structural integrity to cell membranes and regulates the passage of molecules in and out of cells.

Protection: In addition to providing structural support, certain lipids act as protective barriers. For example, lipids found in the skin help prevent water loss and protect against pathogens. In plants, lipids in the form of waxes provide a protective coating on leaves and stems, reducing water loss and protecting against pests and pathogens.

Fatty Acids

Fatty acids are fundamental building blocks of lipids, consisting of long hydrocarbon chains with a carboxyl group at one end. These chains can be either saturated or unsaturated, depending on the presence of double bonds. Unsaturated fatty acids have one or more double bonds, which introduce kinks in the chain, resulting in both polar and non-polar ends. Certain unsaturated fatty acids, like linoleate, are considered essential because mammals cannot synthesize them and must obtain them from the diet. Conversely, fatty acids that the body can synthesize are termed non-essential.

Structure of fatty acids

Triacylglycerols, or triglycerides, are another crucial lipid form, composed of fatty acid esters and glycerol. These molecules are non-polar and hydrophobic, making them excellent for energy storage due to their high energy density.

Enzymes

Enzymes are vital proteins responsible for catalyzing biochemical reactions in living organisms. They exhibit various structural levels, including primary, secondary, and tertiary structures, with an active site that binds to substrate molecules. Enzymes possess several key properties:

• Enzymes are proteins, but not all proteins are enzymes.
• They exhibit specificity towards their substrates, catalyzing specific reactions.
• Enzymes function as catalysts, accelerating chemical reactions without being consumed in the process.
• There are six major types of enzymes: oxidoreductases, transferases, hydrolases, lyases, ligases, and isomerases.
• Some enzymes require cofactors or coenzymes for their catalytic activity.
• Cofactors are non-protein molecules that bind to enzymes and activate them, while coenzymes are transiently bound organic compounds.
• Prosthetic groups are tightly bound organic substances within enzymes.

Various factors influence enzyme activity, including temperature, pH, and substrate concentration. Enzymes have optimal temperature and pH ranges for activity, and deviations can lead to inactivation. Enzyme activity can be modulated by inhibitors, such as competitive inhibitors, which compete with substrates for binding to the enzyme's active site. For instance, malonate can inhibit succinate dehydrogenase by competitively binding to its active site.

Benefits of CBSE Class 11 Biology Notes Chapter 9 Biomolecules

• The notes provide a structured overview of the chapter, helping students understand the key concepts in a systematic manner.
• They cover all essential topics and subtopics included in the CBSE Class 11 Biology syllabus for Biomolecules, ensuring that students don't miss any important information.
• The notes are written in clear and concise language, making complex concepts easier to understand and remember.
• Diagrams, figures, and tables are often included in the notes to visually represent key concepts, aiding in better comprehension and retention.
• They provide a quick reference guide for students to review important points before exams or quizzes.

CBSE Class 11 Biology Notes Chapter Wise List
Chapter 1 The Living World Notes	Chapter 11 Transport in Plants Notes
Chapter 2 Biological Classification	Chapter 12 Mineral Nutrition Notes
Chapter 3 Plant Kingdom Notes	Chapter 13 Photosynthesis in Higher Plants Notes
Chapter 4 Animal Kingdom Notes	Chapter 14 Respiration in Plants Notes
Chapter 5 Morphology of Flowering Plants Notes	Chapter 15 Plant Growth and Development Notes
Chapter 6 Anatomy of Flowering Plants Notes	Chapter 16 Digestion and Absorption Notes
Chapter 7 Structural Organisation in Animals Notes	Chapter 17 Breathing and Exchange of Gases Notes
Chapter 8 Cell the Unit of Life Notes	Chapter 18 Body Fluids and Circulation Notes
Chapter 9 Biomolecules Notes	Chapter 19 Excretory Products and Their Elimination Notes
Chapter 10 Cell Cycle and Cell Division Notes	Chapter 20 Locomotion and Movement Notes
Chapter 21 Neural Control and Coordination Notes	Chapter 22 Chemical Coordination and Integration Notes