What roles do carbohydrates play in biology?
Carbohydrates are composed of carbon, hydrogen, and oxygen with a ratio of one oxygen and two hydrogen atoms for each carbon atom: CH2O. Short chains of carbohydrates are monosaccharides (mah nuh SA kuh ridz), or simple sugars.
A disaccharide (di SA kuh rid) is two monosaccharides linked together. Longer carbohydrate chains are called polysaccharides.
Carbohydrates serve as energy sources for organisms. Also, carbohydrates provide structural support in the cell walls of plants and in the hard shells of shrimp, lobsters, and some insects.
What is the main function of lipids?
Lipids are molecules made mostly of carbon and hydrogen. Fats, oils, and waxes are all lipids. The main function of lipids is to store energy. A lipid called a triglyceride (tri GLIH suh rid) is a fat when solid and an oil when liquid. Plant leaves are coated with lipids called waxes to prevent water loss.
Saturated and Unsaturated Fats When the carbon atoms in a fat cannot bond with any more hydrogen atoms, the fat is a saturated fat. The carbon atoms of unsaturated fats can bond with more hydrogen atoms.
Phospholipids A lipid called a phospholipid is responsible for the structure and function of the cell membrane. Lipids do not dissolve in water. This characteristic enables lipids to serve as barriers in biological membranes.
Steroids Cholesterol and hormones are types of steroids, another group of lipids. In spite of its bad reputation, cholesterol provides the starting point for other important lipids, such as the hormones estrogen and testosterone.
What compounds make up proteins?
A protein is made of small carbon compounds called amino acids. Amino acids are made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfur.
Amino Acids There are 20 different amino acids. Proteins are made of different combinations of all 20 amino acids. Covalent bonds called peptide bonds join amino acids together to form proteins.
Protein Structure A protein’s amino acid chain folds into a three-dimensional shape. The figure below shows two basic protein shapes—the helix and the pleat. A protein might contain many helices, pleats, and folds. Hydrogen bonds help the protein hold its shape.
Protein Function Proteins are involved in nearly every function of your body. Your muscles, skin, and hair are made of proteins. Your cells contain about 10,000 different proteins that serve many functions.
• provide structural support;
• transport substances inside the cell and between cells;
• communicate signals within the cell and between cells;
• speed up chemical reactions;
• control cell growth.
What roles do nucleic acids play in organisms?
Nucleic acids are the fourth group of biological macromolecules. Nucleic acids are complex macromolecules that store and transmit genetic information. Repeating subunits, called nucleotides, make up nucleic acids.
Nucleotides are composed of carbon, nitrogen, oxygen, phosphorus, and hydrogen. All nucleotides have the three units shown in the figure below—a phosphate, a nitrogenous base, and a sugar.
To form a nucleic acid, the sugar of one nucleotide bonds to the phosphate of another nucleotide, as illustrated in the figure on the right. The nitrogenous base sticks out from the chain. It is available to bond with bases in other nucleic acids.
Two types of nucleic acids are found in living things. One is deoxyribonucleic (dee AHK sih rib oh noo klay ihk) acid, or DNA. The other is ribonucleic (rib oh noo KLAY ihk) acid,
DNA is the “genetic code.” DNA stores all the instructions for organisms to grow, reproduce, and adapt. The main function of RNA is to use the information stored in DNA to make proteins.