CBSE Notes

By going through these CBSE Class 11 Biology Notes Chapter 11 Transport in Plants, students can recall all the concepts quickly.

Transport in Plants Notes Class 11 Biology Chapter 11

→ Plants obtain a variety of inorganic elements (ions) and salts from their surroundings especially from the air, water, and soil. The movement of these nutrients from the environment into the plant as well as from one plant cell to another plant cell essentially involves movement across a cell membrane.

→ Transport across cell membrane can be through diffusion, facilitated transport, or active transport.

→ Water and minerals absorbed by roots are transported by the xylem and the organic material synthesized in the leaves is transported to other parts of the plant through phloem.

→ Passive transport (diffusion, osmosis) and active transport are the two modes of nutrient transport across cell membranes in living organisms. In passive transport, by diffusion nutrients move across the membrane without any use of energy as it is always down the concentration gradient and hence entropy-driven. This diffusion of substances depends on their size, solubility in water or organic solvents.

→ Osmosis is the special type of diffusion of water across a semipermeable membrane which depends on pressure gradient and concentration gradient.

→ Inactive transport, energy in the form of ATP is utilized to pump molecules against a concentration gradient across membranes.

→ Water potential is the potential energy of water that helps in the movement of water. It is determined by solute potential and pressure potential.

→ The behavior of the cells depends on the surrounding solution. If the surrounding solution of the cell is hypertonic, it gets plasmolyzed. The absorption of water by seeds and dry wood takes place by a special type of diffusion called imbibition.

→ In higher plants, there is vascular system xylem and phloem responsible for translocation. Water minerals and food cannot be moved within the body of a plant by diffusion alone.

→ They are therefore transported by a mass flow system movement of substance in bulk from one point to another as a result of pressure differences between the two points.

→ Water absorbed by root hairs moves deeper into the root by two distinct pathways i.e. apoplast and symplast.

→ Various ions and water from soil can be transported up to a small height in stems by root pressure.

→ The transpiration pull model is the most acceptable to explain the transport of water. Transpiration is the loss of water in the form of vapors from the plant parts through stomata.

→ Temperature, light, humidity, wind speed, and a number of stomata affect the rate of transpiration. Excess water is also removed through the tips of leaves of plants by guttation.

→ Phloem is responsible for the transport of food (primarily) sucrose from the source to the sink.

→ The translocation in phloem is bi-directional; the source-sink relationship is variable. The translocation phloem is explained by the pressure-flow hypothesis.

→ Transpiration: Transpiration is the evaporative loss of water by the plants. It occurs mainly through the stomata in the leaves.

→ Guttation: Oozing of droplets along the leaf margin on the vein endings at night is called guttation.

→ Diffusion: Movement of molecules of a substance from its place of high concentration to its place of low concentration till equilibrium is reactions between the two regions.

→ Osmosis: Movement of water molecules from a dilute solution to a concentrated solution through a semi-permeable membrane.

→ Plasmolysis: Shrinkage of the protoplasm when the cell is placed in a hypertonic solution is called plasmolysis.

→ Root pressure: As various ions from the soil are actively transported into the root’s vascular tissue, water follows (its potential gradient) and increases the pressure inside the xylem. This positive pressure is called root pressure.

→ Carpathian strip: The endodermis, is impervious to water because of a band of suberised matrix called the Casparian strip.

→ Mycorrhiza: A mycorrhiza is a symbiotic association of a fungus with a root system.

→ Translocation: The bulk movement of substances through the conducting or vascular tissues of plants is called translocation.

→ Turgor pressure: Water diffuses into the cell causing the cytoplasm to build up a pressure against the wall, which is called turgor pressure.

→ Facilitated diffusion: Membrane proteins provide sides at which such molecules across the membrane. They do not set up a concentration gradient: a concentration gradient must already be present for molecules to diffuse even if facilitated by the proteins. This process is called facilitated diffusion.

By going through these CBSE Class 11 Biology Notes Chapter 10 Cell Cycle and Cell Division, students can recall all the concepts quickly.

Cell Cycle and Cell Division Notes Class 11 Biology Chapter 10

→ According to the cell theory, cells arise from pre-existing cells. The process by which this occurs is called cell division.

→ Any sexually reproducing organism starts its life cycle from a single-celled zygote.

→ Cell division does not stop with the formation of the mature organism but continues throughout its life cycle.

→ The stages through which a cell passes from one division to the next are called the cell cycle.

→ The cell cycle is divided into two phases called

1. interface a period of preparation for cells division, and
2. Mitosis the actual period of cell division.

→ Interphase is further subdivided into G₁, S₁, and G₂ G₁ phase is the period when the cell grows and carries out normal metabolism.

→ Most of the organelle duplication also occurs during this phase.

→ S phase marks the phase of DNA replication and chromosome duplication. The G₂ phase is the period of cytoplasmic growth.

→ Mitosis is also divided into four stages namely prophase, metaphase, anaphase, and telophase. Chromosome condensation occurs during prophase.

→ Simultaneously, the centrioles move to the opposite poles.

→ The nuclear envelope and the nucleolus disappear and the spindle fibers start appearing.

→ Metaphase is marked by the alignment of chromosomes at the equatorial plate.

→ During anaphase, the centromeres divide and the chromatids start moving towards two opposite poles.

→ Once the chromatids reach the two poles, the chromosomal elongation starts, nucleolus, and the nuclear membrane reappear.

→ This stage is called telophase.

→ Nuclear division is followed by the cytoplasmic division and is called cytokinesis

→ Mitosis thus is the equational division, in which the chromosome number of a parent is conserved in the daughter cell.

→ In contrast to mitosis, meiosis occurs in the diploid cells, which are destined to form gametes. It is called the reduction division since it reduces the chromosome number by half while making the gametes.

→ In sexual reproduction when the two gametes fuse the chromosome number is restored to the value in the parent cell.

→ Meiosis is devided into two phases-meiosis 1 and meiosis II. In the first meiotic division the homologous chromosomes pair to form bivalents, and undergo crossing over.

→ Meiosis I has long prophase, which is divided further into five phases. These are leptotene, zygotene, pachytene, diplotene and diakinesis.

→ During metaphase I the bivalents arrange an equatorial plate. This is followed by anaphase 1 in which homologous chromosomes move to opposite poles with both their chromatids.

→ Each pole receives half the chromosome number of the parent cell.

→ In telophase I the nuclear membrane and nucleolus reappear.

→ Meiosis II is similar to mitosis.

→ During anaphase II the sister chromatids separate. Thus at the end of meiosis four haploid cells are formed.

→ Equational division: M phase is the most dramatic period of the cell cycle, involving a major reorganization of virtually all cell components. Since the chromosome, number (ploidy) of parent and progeny cell is the same it is also called equational division.

→ Cytokinesis: Mitosis accomplishes the segregation of duplicated chromosomes into daughter nuclei (Karyokinesis), but the cell itself is divided into two daughter cells by a separate process called cytokinesis at the end of which cell division is complete.

→ Cell-plate: The formation of the new cell wall begins with the construction of a simple precursor, called the cell plate that represents the middle lamella between the walls of two adjacent cells.

→ Syncytium: In some organisms’ karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises which is called syncytium.

→ Meiosis: The specialized kind of cell division that reduces the chromosome number by half, resulting in the production of haploid daughter cells, is called meiosis.

→ Meiosis I and Meiosis II: Meiosis involves two sequential cycles to nuclear and cell division, called meiosis I and meiosis II but only a single cycle of DNA replication.

→ Synapsis: Zygotene is the second stage of prophase I during which certain chromosomes start pairing together and this process of association is called synapsis.

→ Synaptonemal complex: Electron complex structure called synaptonemal complex.

→ Bivalent: The complex formed by a pair of synapsed homologous chromosomes is called a bivalent or a tetrad.

→ Interkinesis: The stage between the two meiotic divisions is called interkinesis and is generally short-lived.

→ Crossing Over: Exchange of similar segments between non-sister chromatids of homologous chromosomes usually takes place during the Pachytene stage.

By going through these CBSE Class 11 Biology Notes Chapter 9 Biomolecules, students can recall all the concepts quickly.

Biomolecules Notes Class 11 Biology Chapter 9

→ Although there is a bewildering diversity of living organisms, their chemical composition and metabolic reactions appear to be remarkably similar.

→ The elemental composition of living tissues and non-living matter appear also to be similar when analyzed qualitatively.

→ The most abundant chemical in living organisms is water. There are thousands of small molecular weight (<1000Da) biomolecules.

→ Amino acids, monosaccharide and disaccharide sugars, fatty acids, glycerol, nucleotides, nucleosides, and nitrogen bases are some of the organic compounds seen in living organisms.

→ There are 21 types of amino acids and 5 types of nucleotides. Fats and oils are glycerides in which fatty acids are esterified to glycerol. Phospholipids contain, in addition, a phosphorylated nitrogenous compound.

→ Only three types of macromolecules i.e., proteins, nucleic acids, and polysaccharides are found in living systems.

→ Lipids, because of their association with membranes separate in the macromolecular fraction. Biomacromolecules are polymers. They are made of building blocks that are different. Proteins are heteropolymers made of amino acids.

→ Nucleic acids (RNA and DNA) are composed of nucleotides. Biomacromolecules have a hierarhy of structures i.e., primary, secondary, tertiary and quaternary structures.

→ Nucleic acids serve as genetic material. Polysaccharides are components of the celt wall in plants, fungi and also of the exoskeleton of arthropods.

→ They also are storage forms of energy (e.g. starch and glycogen.) Proteins serve a variety of cellular functions. Many of them are enzymes, some are antibodies, some are receptors, some are hormones and some others are structural proteins.

→ Collagen is the most abundant protein in the animal world and Rubisco is the most abundant protein in the whole biosphere.

→ Enzymes are proteins that catalyze biochemical reactions in the cells. Ribozymes are nucleic acids with catalytic power.

→ Proteinaceous enzymes exhibit substrate specificity, require optimum temperature and pH for maximal activity. They are denatured at high temperatures.

→ Enzymes lower the activation energy of reactions and enhance greatly the rate of the reactions.

→ Nucleic acids carry hereditary information and are passed on from parental generation to progeny.

→ Biomolecules: All the carbon compounds that we get from living tissues can be called ‘biomolecules’.

→ a-amino acids: Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon i.e., the a-carbon. Hence they are called a-amino acids.

→ Nucleosides: Some of these are nitrogen bases-adenine, guanine, cytosine, uracil, and thymine. When found attached to a sugar, they are called nucleosides.

→ Primary metabolites: In animal tissues, one notices the presence of all such categories of compounds. These are called primary metabolites.

→ Secondary metabolites: When one analyses plant, fungal and microbial cells, one would see thousands of compounds other than these called primary metabolites, e.g., alkaloids, flavonoids, rubber, essential oils, antibiotics, coloured pigments, scents, gums, spices. These are called ‘secondary metabolites.

→ Biomacromolecules: One, those which have molecular weights less than one thousand and are usually referred to as macromolecules or simply as biomolecules while those which are found in the acid-insoluble fraction are called macromolecules or as biomacromolecules.

→ Glycogen: Animals have another variant called glycogen.

→ Deoxyribonucleic acid/ Ribonucleic acid: A nucleic acid containing deoxyribose is called deoxyribonucleic acid (DNA) while that which contains ribose is called ribonucleic acid (RNA).

→ Quaternary structure: The manner in which these’ individual folded polypeptides or subunits are arranged with respect to each other is the architecture of a protein otherwise called the quaternary structure of a protein.

→ Phosphodiester: The bond between the phosphate and hydroxyl group of sugar is an ester bond. As there is one such ester bond on either side, it is called the phosphodiester bond.

→ Metabolic pathway: A multistep chemical reaction when each of the steps is catalyzed by the same enzyme complex or different enzymes is called a metabolic pathway.

→ Isomerases: Includes all enzymes catalyzing the interconversion of optical, geometric, or positional isomers.

→ Ligases: Enzymes catalyzing the linking together of 2 compounds e.g., enzymes that catalyze joining of C-O, C-S, C-N, PO, etc. bonds.

→ Substrate: The chemical which is converted into a product is called a ‘substrate’.

→ Inhibition/Inhibitor: When the binding of the chemical shuts off enzyme activity, the process is called inhibition and the chemical is called an inhibitor.

By going through these CBSE Class 11 Biology Notes Chapter 8 Cell: The Unit of Life, students can recall all the concepts quickly.

Cell: The Unit of Life Notes Class 11 Biology Chapter 8

→ All organisms are composed of cells.

→ Some are composed of a single cell and called unicellular organisms while others, like us, are composed of many cells and called multicellular organisms.

→ The cell is the fundamental structural and functional unit of all living organisms.

→ Unicellular organisms explain that a cell is capable of independently existing and of performing the essential functions of life.

→ Robert Hooke was the first person to describe the cell in 1865 when he used a microscope built by him to examine a thin slice of cork.

→ In 1831, Robert Brown made an important discovery when he reported the presence of a small sphere in the cells of the orchid root. This rounded body which later came to be called the ‘nucleus’ was thought to be of common occurrence in the cells.

→ In 1838, Matthias Schleiden, a German Botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the different tissues of the plant.

→ Same time, Theodore Schwann (1839), a British Zoologist, also studied different types of animal cells. He observed the nuclei in these cells had a thin outer layer which is today known as the ‘plasma membrane’.

→ Schwann proposed the hypothesis that the bodies of animals and ( plants are composed of cells and products of cells.

→ Schleiden and Schwann combined their views and formulated the cell theory.

→ In 1855 when Rudolf Virchow first explained that cells divided and new cells are formed the pre-existing cells.

→ Cell theory as understood today is:

1. all living organisms are composed of cells and products of cells,
2. all cells arise from pre-existing cells.

→ A typical cell consists of a cell membrane, nucleus, and cytoplasm. Plant cells have a cell wall.

→ Cells are specialized to perform different functions and their shape and size may vary accordingly.

→ Cells are not only the building blocks of an organism but also the functional unit of life.

→ Cells vary in their shape, size, and activities/functions. Based on the presence or absence of a membrane-bound nucleus and other organelles, cells and hence organisms can be named eukaryotic or prokaryotic.

→ A typical eukaryotic cell consists of a cell membrane, nucleus, and cytoplasm.

→ Plant cells have a cell wall outside the cell membrane.

→ The plasma membrane is selectively permeable and facilitates the transport of several molecules. The endomembrane system includes ER, Golgi complex, lysosomes, and/vacuoles.

→ All the cell organelles perform different but specific functions. Centrosome and centriole form the basal body of cilia and flagella that facilitate locomotion.

→ In animal cells, centrioles also form spindle apparatus during cell division. The nucleus contains nucleoli and chromatin networks. It not only controls the activities of organelles but also plays a major role in heredity.

→ The endoplasmic reticulum contains tubules or cisternae. They are of two types: rough and smooth.

→ The Golgi body is a membranous organelle composed of flattened sacs. The secretions of cells are packed in them and transported from the cell.

→ Lysosomes are single membrane structures containing enzymes for the digestion of all types of macromolecules. Ribosomes are involved in protein synthesis.

→ Plastids are pigments containing organelles found in plant cells only. In-plant cells, chloroplasts are responsible for trapping light energy essential for photosynthesis.

→ The nucleus is enclosed by a nuclear envelope, a double membrane structure with nuclear pores. The inner membrane encloses the nucleoplasm and the chromatin material.

→ Cellular: A honeycomb-like structure with an empty compartment which Hooke called ‘cellular- a Latin word for a small room.

→ Plasma membrane: The nuclei in these cells had a thin outer layer which is today known as the ‘plasma membrane.

→ Organelles: Certain cellular functions are associated with different types of distinct structures called organelles present in the cytoplasm.

→ Peptidoglycan: The cell wall is rigid because of the presence of special macromolecules called peptidoglycan.

→ Polyribosomes: The ribosomes are the site of protein synthesis. Several ribosomes may attach to a single mRNA and form a chain called polyri¬bosomes or polysomes.

→ Pilin: The pills are elongate tubular structures made of a special protein called pinin.

→ Cell wall: The plant cells possess a conspicuous thick layer of cellulose covering the cell membrane called the cell wall.

→ Passive transport: Many molecules can move passively across the membrane without any requirement of energy called passive transport.

→ Endomembrane System: Each of the membranous organelles is distinct in terms of their structure and function but many of these are considered together as a part of the so-called Endomembrane system because their functions are coordinated.

→ Endoplasmic Reticulum (ER): The electron microscopic study of the variety of eukaryotic cells revealed the presence of a network or reticulum of the tiny tubular structure scattered in the cytoplasm and hence, called the Endoplasmic Reticulum.

→ Exocytosis: The hydrolytic enzymes present in the phagosomes partially digest the engulfed material a residual body is formed, which is usually eliminated from the cell by a process called exocytosis.

→ Turgor pressure: Vacuoles also exert a hydrostatic pressure called the turgor pressure that gives mechanical support to the cell.

→ Matrix: Each mitochondrion is a double membrane-bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments i.e. the outer compartment and the inner compartment called the matrix.

→ Hub: The central part of the centriole is also, proteinaceous called the hub.

→ Nucleus: The eukaryotic cells usually possess a large-sized, almost centrally located, and densely stained organelle containing the genetic material called the nucleus.

→ Histones: The biochemical analysis of the isolated chromatin has revealed that it contains DNA and some basic protein called histones.

→ Kinetochore: Every chromosome essentially has a primary constriction of the centromere on the sides of which disc-shaped structures called the kinetochore.

By going through these CBSE Class 11 Biology Notes Chapter 7 Structural Organisation in Animals, students can recall all the concepts quickly.

Structural Organisation in Animals Notes Class 11 Biology Chapter 7

→ Cells, tissues, organs and organ systems split up the work in a way that ensures the survival of the body as a whole and exhibit division of labour.

→ A tissue is defined as a group of cells along with intercellular substances performing one or more functions in the
body.

→ Epithelia are sheet-like tissues lining the body’s surface and its cavities, ducts and tubes. Epithelia have one free surface facing a body fluid or the outside environment. Their cells are structurally and functionally connected at junctions.

→ Diverse types of connective tissues bind together, support, strengthen, protect and insulate other tissue in the body. Soft connective tissues consist of protein fibres as well as a variety of cells arranged in a ground ‘ substance.

→ Cartilage, bone, blood, and adipose tissue are specialised connective tissues. Cartilage and bone are both structural materials.

→ Blood is a fluid tissue with transport functions.

→ Adipose tissue is a reservoir of stored energy. Muscle tissue, which can contract (shorten) in response to stimulation, helps in the movement of the body and specific body parts.

→ Skeletal muscle is the muscle tissue attached to bones. Smooth muscle is a component of internal organs. The cardiac muscle makes up the contractile walls of the heart. Connective tissue covers all three types of tissues. Nervous tissue exerts the greatest control over the response of the body. Neurons are the basic units of nervous tissue.

→ Earthworm, cockroach and frog show characteristic features in body organisation. In Pheretima Posthuma (earthworm), the body is covered by a cuticle.

→ All segments of its body are alike except the 14th, 15th and 16th segment, which are thick and dark and glandular, forming clitellum.

→ A ring of S-shaped chitinous setae is found in each segment. These setae help In locomotion. On the ventral side, spermathecal openings are present in between the grooves of 5 and 6, 6 and 7, 7 and 8 and 9 segments.

→ Female genital pores are present in the 14th segment and male genital pores in the 18th segment.

→ The alimentary canal is a narrow tube made of the mouth, buccal cavity, pharynx, gizzard, stomach, intestine and anus. The blood vascular system is of closed type with heart and valves. The nervous system is represented by the ventral nerve cord.

→ The earthworm is hermaphrodite. Two pairs of testes occur in the 10th and 11th segment, respectively. A pair of ovaries are present on the 12 and 1.3th intersegmental septum. It is a protandrous animal with cross-fertilisation. Fertilisation and development take place in the cocoon secreted by the glands of the clitellum.

→ The body of the cockroach (Periplaneta americana) is covered by a chitinous exoskeleton. It is divided into head, thorax and abdomen. Segments bear jointed appendages. There are three segments of thorax, each bearing a pair of walking legs. Two pairs of wings are present, one pair each on the 2nd and 3rd segment. There are ten segments in the abdomen.

→ The alimentary canal is well developed with a mouth surrounded by mouthparts, a pharynx, oesophagus, crop, gizzard, midgut, hindgut and anus. Hepatic cancer is present at the junction of the foregut and midgut.

→ Malpighian tubules are present at the junction of the midgut and hindgut and help in excretion. A pair of the salivary gland is present near 1 crop. The blood vascular system is of open type. Respiration takes place by a network of tracheae.

→ The trachea opens outside with spiracles. The nervous system is represented by segmentally arranged ganglia and ventral nerve cord.

→ A pair of testes are present in the 4th and 5th segments and ovaries in the 4th, 5th and 6th segment. Fertilisation is internal. Female produces 10-40 ootheca bearing developing embryos. After rupturing of single ootheca, ‘ sixteen young ones, called nymphs come out.

→ The Indian bullfrog, Rana Tigrina, is the common frog in the Indian Body that is covered by skin. Mucous glands are present in the skin which is highly vascularized and helps in respiration in water and on land.

→ The body is divisible into the head and hunk. A muscular tongue is present, which is bilobed at the tip and is used in capturing the prey. The alimentary canal consists of the oesophagus, stomach, intestine and rectum, which open into the cloaca. The main digestive glands are the liver and pancreas. It can respire in water through the skin and through lungs on land.

→ The circulatory system is closed with a single circulation. RBC, are nucleated. The nervous system is organised into central, peripheral and autonomic. The organs of the urinogenital system are kidneys and urinogenital ducts, which open into the cloaca.

→ The male reproductive organ is a pair of testes. The female reproductive organ is a pair of ovaries. A female lays 2500-3000 ova at a time. The fertilisation and development are external. The eggs hatch into tadpoles, which metamorphose into frogs.

→ Tadpole: Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult.

→ BrainBox: The brain is enclosed in a bony structure called brain box (cranium)

→ Vena-cava: Right atrium receives blood through the major veins called vena cava.

→ Sinus venous: A triangular structure called sinus Venosus joins the right atrium.

→ Pericardium: The heart has three chambers, two atria and one ventricle and is covered by a membrane called the pericardium.

→ Pulmonary respiration: The respiration by the lungs is called pulmonary respiration.

→ Summer sleep and winter sleep: The frogs are not seen during peak summer and winter. During this period they take shelter in deep burrows to protect them from extreme heat and cold. This is called summer sleep (aestivation) and winter sleep (hibernation).

→ Mimicry: Frogs have the ability to change the colour to hide from their enemies (camouflage).

→ Poikilotherms: Frogs do not have constant body temperature i.e., their body temperature varies with the temperature of the environment. Such animals are called cold-blooded or poikilotherms.

→ Oothecae: Cockroaches fertilised eggs are encased in capsules called oothecae. The ootheca is a dark reddish to the blackish-brown capsule, about 3/8″ (8mm) long.

→ Spermatophores: The sperms are stored in the seminal vesicles and are glued together in the form of bundles called spermatophores which are discharged during copulation.

→ Spiracles: The respiratory system consists of a network of the trachea, that open through 10 pairs of small holes called spiracles present on the lateral side of the body.

→ Hepatic or gastric: A ring of 6-8 blind tubules called hepatic or gastric cancer is present at the junction of foregut and midgut, which secreted digestive juice.

→ Vermicomposting: The process of increasing the fertility of the soil by the earthworms is called vermicomposting.

→ Anus: The alimentary canal opens to the exterior by a small rounded
aperture called the anus.

→ typhlosole: The characteristic feature of the intestine between 26-35 segments is the presence of an internal median fold of the dorsal wall called typhlosole.

→ Glandular epithelium: Some of the columnar or cuboidal cells get specialised for secretion and are called the glandular epithelium.