Elements found in Living Systems The three commonest chemical elements of life are : Carbon Hydrogen Oxygen They are part of all the main organic compounds in living organism
Examples of Chemical Elements and Their Roles Element Role in plants and animals NitrogenPart of the amine groups of amino acids and therefore proteins. CalciumNeeded to make the mineral that strengthens bones and teeth. PhosphorusPart of the phosphate groups in ATP and DNA molecules. IronNeeded to make Hemoglobin and thus to carry oxygen in blood. SodiumUsed in neurons ( nerve cells) for the transmission of nerve impulses.
Organic and inorganic compounds: Living organisms contain many chemical compounds. Some on them are organic and some inorganic: Organic: compounds containing carbon that are found in living organism. ex. Proteins, Carbohydrates, Lipids and Nucleic Acids
Inorganic compounds: There are a few carbon compounds that are inorganic even though they can be found in living organisms: These are single carbon compounds that are also widely found in the environment. Carbon Dioxides Carbonates and Hydrogen Carbonates
Subunits of Organic Compounds: The molecules of many organic compounds are large and may seem complex, but they are built up using small and relatively simple subunits: Important Subunits Protein Subunits: Amino Acids
Proteins are instrumental in about everything that an organism does. These functions include structural support, storage, transport of other substances, intercellular signaling, movement, and defense against foreign substances. Proteins are the overwhelming enzymes in a cell and regulate metabolism by selectively accelerating chemical reactions. Humans have tens of thousands of different proteins, each with their own structure and function.
Function of Proteins: A protein’s specific conformation determines its function. In almost every case, the function depends on its ability to recognize and bind to some other molecule. For example, antibodies bind to particular foreign substances that fit their binding sites. Enzyme recognize and bind to specific substrates, facilitating a chemical reaction. Neurotransmitters pass signals from one cell to another by binding to receptor sites on proteins in the membrane of the receiving cell.
Proteins have four main structures:
The primary structure of a protein is its unique sequence of amino acids. Lysozyme, an enzyme that attacks bacteria, consists on a polypeptide chain of 129 amino acids. The precise primary structure of a protein is determined by inherited genetic information. Fig. 5.18
Examples of Carbohydrates Monosaccharides Glucose, fructose, and ribose Disaccharides Sucrose (glucose + fructose) Polysaccharides Starch (made of glucose subunits) Glycogen (made of glucose subunits, but linked differently from starch)
Functions of Carbohydrates: Transport – glucose is carried by the blood to transport energy to cells throughout the body. Energy Storage – Energy is stored in the form of glycogen in liver cells
Function of Lipids: Energy storage – in the form of fat in humans and oil in plants. Heat Insulation – a layer of fat under the skin reduces heat loss. Bouyancy – Lipids are less dense than water so help animals to float.
saturated fatty acid - a hydrogen at every possible position.
unsaturated fatty acid - formed by the removal of hydrogen atoms from the carbon skeleton.
Carbohydrates and Lipids in Energy Storage Advantages ofAdvantages of LipidsCarbo’s 1. More energy per gram, 1. Carbohydrates are more stores of lipids are easily digested than lipids lighter then stores of so the energy stored by Carbo’s that contain the them can be released more Same amount of energy. Rapidly. 2. Lipids are insoluble in 2. Carbohydrates are soluble water, so they do not in water so are easier to cause problems with transport to and from Osmosis in cells storage. 3. Energy storage for 3. Energy storage for short Long-term periods.
Nucleotide subunits: 3 parts These make up the rungs of the ladder Pyrimidines C, T and U Purines A and G These make up the backbone of DNA Deoxyribose or Ribose Phosphate Group
There are two types of nucleic acids: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). DNA provides direction for its own replication. DNA also directs RNA synthesis and, through RNA, controls protein synthesis.
Genes code for proteins: The amino acid sequence of a polypeptide is programmed by a gene. A gene consists of regions of DNA, a polymer of nucleic acids. DNA (and their genes) is passed by the mechanisms of inheritance.
How Larger Molecules are made: Condensation Reactions In a condensation reaction two molecules are joined together to form a larger molecule. Water is also formed in the reaction.
Creating a Dipeptide: Condensation of two Amino Acids to form a dipeptides and water + H 2 O
Further condensations forming a Polypeptide
Condensation can be used to build Carbohydrates Disaccharide Polysaccharides
and Lipids forming Triglycerides
Hydrolysis Reactions: Large molecules such as polypeptides, polysaccharides and triglycerides can be broken down into smaller molecules by hydrolysis reactions. Water molecules are used up. Reverse of Condensation Polypeptides + Water Dipeptides or Amino Acids Polysaccharides + Water Disaccharides and Monosaccharides Glycerides + Water Fatty Acids + Glycerol