Biological Molecules PDF

Biological Molecules Biological molecules are the building blocks of life, they play essential roles in various biological processes, including metabolism, energy storage, and information transfer within cells. Living organisms have 4 classes of these large molecules: 1. Carbohydrates 2. Lipids...

Biological Molecules Biological molecules are the building blocks of life, they play essential roles in various biological processes, including metabolism, energy storage, and information transfer within cells. Living organisms have 4 classes of these large molecules: 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic acids All of these classes are (huge biological molecules) Macromolecules except lipids. Biological Molecules ´ Carbohydrates, Proteins, and Nucleic acids are polymers (large molecules consisting of many identical building blocks linked together by covalent bonds, the monomers) ´ Biological molecules are composed of the following elements; Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), and Sulpher (S). In addition to other trace elements. ´ These elements combine in various configurations to form various biological molecules essential for life. 1. Carbohydrates ´ Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen in a ratio of approximately 1:2:1. ´ They serve as a primary source of energy for living organisms and play structural roles in cells. Carbohydrates can be classified into three main groups: ´ Monosaccharides ´ Disaccharides ´ Polysaccharides 1. Carbohydrates Monosaccharides The simplest carbohydrates consist of single sugar units (monomers). Are the building blocks for more complex carbohydrates. Examples include glucose, fructose, and galactose. ´ Glucose: the important source of energy of living cells. ´ Galactose: structurally similar to glucose, differing only in the orientation of one hydroxyl group. ´ Fructose: known as fruit sugar due to its high concentration in fruits and honey. 1. Carbohydrates Fructose: ´ In the body, fructose is metabolized primarily in the liver, where it can be converted into glucose, used for energy production, or stored as glycogen. ´ Excessive consumption of fructose, especially in the form of high-fructose corn syrup, has been linked to various health issues, including obesity, type 2 diabetes, and non-alcoholic fatty liver disease. 1. Carbohydrates Disaccharides Formed of 2 monomers of Monosaccharide sugar linked together by a glycosidic covalent bond. Examples include maltose, sucrose, and lactose. ´ Maltose (malt sugar): formed by the linking between 2 molecules of glucose. ´ Sucrose (table sugar): is the most prevalent disaccharide, formed of 2 monomers of glucose and fructose. ´ Lactose (milk sugar): formed of glucose and galactose. 1. Carbohydrates Polysaccharides Macromolecules, polymers (hundred to a few thousand monosaccharides) joined by glycosidic linkages. Some are storage materials, Other polysaccharides are structure-building materials. A- Storage Polysaccharides: 1. The starch: a storage form of glucose in plants (root & Seeds). 2. Glycogen: a storage form of glucose in animals and humans, mainly stored in the liver and muscle cells. 1. Carbohydrates B- Structural Polysaccharide: 1. Cellulose: is the main component of the cell walls of plant cells, and helps in supporting it. 2. Chitin: forms the exoskeleton of arthropods (insects & spiders). Is used to make a strong and flexible surgical thread that decomposes after the wound heals. 1. Carbohydrates Functions of Carbohydrates 1. It is the primary source of energy for cells. 2. They represent the energy storage of the cells. 3. The structure and support of cells and tissues. 4. Play a role in cell-cell recognition and communication. 5. They are involved in cell adhesion, immune response, and cell signaling. 6. Source of dietary fibers. 2. Lipids ´ Large biological molecules but are not true polymers. ´ Hydrophobic hydrocarbon (poorly mixed with water), non-polar molecules. ´ It includes: ´ Fats ´ Phospholipids ´ Steroids 2. Lipids a. Fats: ´ Formed from two types of molecules, glycerol and fatty acids (3 fatty acids to each glycerol molecule). ´ Stored in fat cells to form adipose tissue. ´ A fatty acid has (16 or 18) carbon atoms in length. ´ Fatty acids may be saturated (no double bonds between carbon atoms, C - C ), solid at room temperature, or unsaturated (has one or more double bonds, C = C), liquid at room temperature. ´ Most animal fats are saturated as lard and butter. ´ The fats of plants and fishes are generally unsaturated (oils). 2. Lipids b. Phospholipids ´ Essential for cells because they make up plasma membranes. ´ 2 fatty acids to each glycerol molecule. ´ Amphipathic molecules, are composed of a phosphate group head and a hydrocarbon tail. ´ The head is hydrophilic (has an affinity for water) while the tail is hydrophobic (excluded from water) 2. Lipids Phospholipids https://www.thoughtco.com/phospholipids-373561 https://ib.bioninja.com.au/phospholipids/ 2. Lipids c. Steroids ´ Are lipids characterized by a carbon skeleton consisting of four fused rings. ´ Insoluble in water also like other lipids. ´ Example: Cholesterol 1. Common component of the animal cell membranes. 2. Synthesized in the liver and obtained from the diet. 3. A high level of cholesterol in the blood may lead to atherosclerosis. 4. Precursor for many steroid hormones as cortisone and testosterone. 2. Lipids Steroids https://www.shutterstock.com/search/steroid-molecule 2. Lipids Functions of Lipids: 1. Particularly triglycerides, serve as a highly concentrated energy storage form. 2. Lipids contribute to the structure and function of cell membranes. 3. Cholesterol helps to regulate membrane fluidity and stability. 4. Insulation and protection. 5. Hormone production (steroids). 3. Proteins ´ The most abundant molecules in living tissue (account for more than 50% of the dry mass of most cells). ´ Polymer macromolecules (polypeptide chains), formed of monomers of amino acids attached by peptide bonds. Arranged in a linear structure. ´ Most of the enzymes are proteins that regulate metabolism by acting as catalysts (chemical agents that speed up chemical reactions). ´ Other examples of proteins include hormones, plasma proteins, antibodies, actin, and myosin. 3. Proteins https://www.news-medical.net/life-sciences/Protein-Structure-and-Function.aspx 3. Proteins Functions of proteins 1. Enzymatic Activity: act as biological catalysts. 2. Provide structural support and stability to cells, tissues, and organs (collagen & keratin). 3. Facilitate the transport of molecules across cell membranes. 4. Act as signaling molecules (hormones) that regulate various physiological processes. 5. Immune responses such as antibodies. 6. Proteins like actin and myosin are responsible for muscle contraction and movement. 7. Transcription factors bind to DNA and regulate the transcription of genes 4. Nucleic acids ´ Are macromolecules that exist as polymers called Polynucleotides. ´ Each polynucleotide consists of monomers called nucleotides. ´ Nucleic acids store and transmit hereditary information. ´ There are two types of nucleic acids: 1. Deoxyribonucleic acid (DNA). 2. Ribonucleic acid (RNA). 4. Nucleic acids Nucleotide: Is composed of three parts: 1. Nitrogenous base, 2. Five-carbon sugar (pentose sugar), 3. Phosphate groups. Each nucleotide has only one phosphate group. Nucleoside: is the portion of nucleotide without any phosphate group. 4. Nucleic acids Nucleotide 4. Nucleic acids Nitrogenous bases & Pentose sugar ´ It has one or two rings that include nitrogen atoms. ´ Two families, purines and pyrimidines. ´ Pyrimidines have one six-membered ring of carbon and nitrogen atoms. It contains cytosine (C), thymine (T), and uracil (U). ´ Purines have a six-membered ring fused to a five-membered ring. It contains adenine (A) and guanine (G). 4. Nucleic acids Pentose Sugar Nitrogenous bases  4. Nucleic acids Structure of DNA & RNA ´ DNA is a double helix structure (spiral), the 2 strands run in opposite directions to each other (5’ to 3’) and (3’ to 5’), i.e. antiparallel. ´ The 2 strands form one complete turn every 3.4 nm. DNA RNA Have (A), (G), (C), and (T) Have (A), (G), (C), and (U) Deoxyribose sugar Ribose sugar Double strand Single strand Long polynucleotide chain Short polynucleotide chain Comparison between DNA & RNA 4. Nucleic acids Structure of DNA & RNA https://www.technologynetworks.com/genomics/articles  4. Nucleic acids ´ Nitrogenous bases of the 2 opposite strands in the helix attached by hydrogen bond. ´ In the double helix, Adenine (A) always pairs with thymine (T) by 2 hydrogen bonds, and guanine (G) pairs with cytosine (C) by 3 hydrogen bonds. ´ In one DNA strand, nucleotides are attached to each other by covalent phosphodiester bond. ´ The distance between 2 successive base pairs is 0.34 nm. ´ The width of DNA double helix is 2 nm. 4. Nucleic acids https://www.researchgate.net/figure/Double-stranded-DNA-detailed-structure_fig1_336118086