• A level biology,  A level biology,  Biochemistry,  Biology,  Cell biology,  O level biology,  Q & A

    What is enzyme and characteristics?

    Enzymes are biological catalysts that facilitate chemical reactions in living organisms. They are typically proteins, although some RNA molecules also have catalytic activity. Enzymes are essential for life because they speed up the reactions that are necessary for cells to function properly. Without enzymes, many biochemical reactions in the body would occur too slowly to support life. Enzymes work by lowering the activation energy required for a chemical reaction to occur. Activation energy is the amount of energy needed to start a reaction, and enzymes reduce this energy barrier, allowing the reaction to occur more quickly. Enzymes do this by binding to specific molecules, called substrates, and positioning them in…

  • plasma-membrane
    A level biology,  A level biology,  Biochemistry,  Biology,  Cell biology,  O level biology

    Plasma membrane

    Delimiting membrane or boundary of all cells providing the characteristic shape to the cell. Structure ● Composed of approx. 7 nm thick phospholipid bilayer with hydrophilic heads facing outward from both sides into aqueous environment and hydrophobic tails facing inside the bilayer. ● A symmetrical the presence of proteins, floating in the bilayer imparts a fluid mosaic pattern which comprises of (a) Integral/Intrinsic proteins spanning through the lipid bilayer, protruding both extracellular and cytoplasmic sides of membrane. (b) Peripheral/Extrinsic proteins located on outside either extracellular or cytoplasmic surface. (c) Lipid anchored proteins covalently linked to a lipid molecule of bilayer but present outside to it. ● Some oligosaccharides are covalently…

  • mutation
    A level biology,  A level biology,  Biochemistry,  Biology,  Cell biology,  Genetics,  O level biology


    Mutation is a change in the DNA sequence of an organism’s genetic material. DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development and function of all living things. DNA is made up of four chemical bases, adenine (A), cytosine (C), guanine (G), and thymine (T), which are arranged in a specific sequence to form genes. Genes are the functional units of DNA that encode specific traits and are passed on from parent to offspring. In biology, mutations can occur naturally or as a result of exposure to certain environmental factors such as radiation or chemicals. Natural mutations can arise from errors during DNA replication…

  • chromosome
    A level biology,  A level biology,  Biochemistry,  Biology,  Cell biology,  Genetics,  O level biology


    A chromosome is a structure found in cells that is made up of a long strand of DNA, which is the genetic material that contains the instructions for the development and function of all living organisms. Chromosomes are found in the nucleus of eukaryotic cells and play a crucial role in the cell cycle, replication, and transmission of genetic information. Chromosomes are tightly coiled, compact structures that can be seen under a microscope during cell division. The DNA in chromosomes is organized into segments called genes, which contain the instructions for making proteins and other essential molecules for life. Proteins play a critical role in many cellular processes, such as…

  • Diffusion
    Cell biology,  O level biology

    Diffusion – Movement of Substances

    Table of Contents Diffusion Defination Diffusion is the net movement of molecules and ions from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement. What is Diffusion  The molecules of a gas such as oxygen are moving about all the time. So are the molecules of a liquid or a substance such as sugar dissolved in water. As a result of this movement, the molecules spread themselves out evenly to fill all the available space (Figure). Diffusion This process is called diffusion. How are substances transported by diffusion? One effect of diffusion is that the…

  • Cell biology,  Video Notes


    The cells of epithelial and other tissues are held together by various types of cell junctions, that can be categorized into 3- main groups – (I) Adhesive junctions The cells of epithelial tissue and even cardiac muscles are difficult to separate due to the presence of adhesive junctions. Such junctions are of 2-types (a) Adherens junctions (b) Desmosomes (a) Adherens junctions (Zonulae adherens) – Such junctions are common in the epithelial living of intestine where they form a ‘belt’ encircling the apical portion of cells and binding them to surrounding cells. Such junctions are formed by calcium -dependant-linkages of cadherin (protein) molecules and cement the cells for providing a pathway…

  • Biochemistry,  Cell biology


    The clot or coagulam is a dark -reddish-brown ‘scum’ formed mainly by a network of threads in which dead or damaged blood elements are trapped. It is the property of plasma. Normal blood clotting time is 3−10 min. The clot inside the blood vessels is called a thrombus. A moving thrombus is called embolus. In haemophilia (a sex-linked disease) the blood clotting is delayed. According to Macferlane hypothesis, there are 13−factors responsible for blood clotting (or coagulation). The 4−factors are primary and 9−factors are accessory for this process. Primary factors Fibrinogen Prothrombin Thromboplastin (Thrombokinase) Calcium ions  The first 3−factors are proteinaceous in nature. The Prothrombin (II factor) is synthesized in…

  • types_of_carbohydrates
    Biochemistry,  Biology,  Cell biology


    Table of Contents Carbohydrates are classified into two types on the basis of molecular weight. Micromolecules – Monosaccharides and Oligosaccharides (Including Disaccharides) Macromolecules – Polysaccharides The micromolecules have the molecular weight of < 1000 Daltons whereas themacromolecules have > 1000 Daltons as molecular weight. Why do we need carbohydrates in our food? Carbohydrates provides about 50-70% of total energy. We need average carbohydrate requirement in an adult is ~ 400g per day. Essential elements in the constitution of carbohydrate – C. H. O General Formula – *Cx (H2O)y (Containing more than one-OH groups). The polyhydroxy aldehydes or ketones can also be called as saccharides 80% of the dry weight of…

  • Biochemistry,  Cell biology,  Q & A

    What is the function of the cell membrane?

    The cell membrane is otherwise called a Plasma membrane. It may be defined as the thin, elastic, semipermeable living membrane that serves as a boundary for the Cytoplasm. The Cell membrane is made up of glycoproteins and phospholipids. The Functions of the Cell membrane are as follows: Cell membrane or Plasma membrane is a semipermeable membrane present around the Protoplasm. It acts as a boundary to the cell. It gives a definite shape to the Cell. It gives Mechanical support to the Cell. It protects cell contents. It regulates the exchange of materials into and out of the cell. The Sites for cell recognition are located on the surface of the Plasma…

  • Biochemistry,  Cell biology


    OXIDATIVE PHOSPHORYLATION It is the main source of energy of our cell. Takes place in Mitochondria. Movement of protons through inner mitochondrial membrane leads to ATP production DEFINITION Oxidative phosphorylation includes the coupling of the oxidation of NADH or FADH2 by the respiratory chain with the synthesis of ATP via gradient of protons across the inner mitochondrial membrane. ELECTRON TRANSPORT CHAIN An electron transport chain consists of a properly arranged & oriented set of electron carriers transporting electrons in a specific sequence from a reduced nicotinamide coenzyme (NADH) or a reduced flavin prosthetic group (FADH2) to molecular O2. Transport chain called the mitochondrial respiratory chain, which forms the final path for electron…