Biology Chapter on Water and Carbohydrates

Water

• Makes up 80% of a cell's contents
• Is an excellent solvent, allowing for the dissolving of useful substances, which facilitates transport within the cell.
• Plays a crucial role in temperature regulation thanks to its high specific heat capacity and high latent heat of evaporation.
• High specific heat capacity means that a large amount of energy is required to raise the temperature of water by 1°C, making it a stable environment for living organisms.
• High latent heat of evaporation means a significant amount of energy is needed to break the bonds between water molecules during evaporation, leading to a cooling effect.
• The cohesive (attraction between water molecules) and adhesive (attraction between water molecules and other surfaces) properties of water are essential for its flow and transport of substances.
• Water's lower density when frozen insulates aquatic organisms under ice.

Carbohydrates

• Consist of carbon, hydrogen, and oxygen.
• Serve as both energy storage and structural support within cells.
• Monosaccharides, the building blocks of carbohydrates, are simple sugars, including hexose sugars like glucose.
• Glucose exists in two forms, alpha and beta.
• Ribose, a five-carbon sugar, is found in RNA nucleotides.
• Monosaccharides are linked by glycosidic bonds to form polysaccharides.
• Starch, the main energy storage material in plants, is a mixture of amylose and amylopectin.
  • Amylose, a long unbranched chain of alpha-glucose molecules linked by 1,4-glycosidic bonds, coils into a compact structure, making it ideal for storage.
  • Amylopectin, also composed of alpha-glucose, features branching, allowing enzymes to break down the glycosidic bonds more rapidly.
• Glycogen, the primary energy storage material in animals, is similar to amylopectin but even more branched, ensuring rapid access to energy.
• Cellulose, a major component of plant cell walls, consists of long, unbranched chains of beta-glucose molecules held together by hydrogen bonds. Its rigid structure provides support for plant cells.

Lipids

• They are composed of carbon, hydrogen, and oxygen.
• They are made of glycerol and three fatty acids, linked by ester bonds.
• They serve as energy storage, structural components of cell membranes, and hormones.
• Triglycerides, composed of glycerol and three fatty acids, store a large amount of energy due to the hydrocarbon tails of the fatty acids.
• Phospholipids, similar to triglycerides but with one fatty acid replaced by a phosphate group, are the primary components of cell membranes.
  • The phosphate group is hydrophilic (water-loving), while the fatty acid tails are hydrophobic (water-fearing). This dual nature forms the phospholipid bilayer, the basis of cell membrane structure.
• Cholesterol, found in cell membranes, strengthens and stabilizes the membrane by fitting between phospholipids, making the membrane less fluid and more rigid.

Proteins

• Polymers composed of amino acid monomers.
• Dipeptides consist of two amino acids, while polypeptides contain more than two.
• All amino acids share a common structure with carbon, oxygen, hydrogen, and nitrogen.
• Peptide bonds link individual amino acids together to form proteins.
• The primary structure of a protein is the specific sequence of amino acids in a polypeptide chain, unique for each protein.
• The secondary structure of a protein arises from hydrogen bonds between amino and carboxyl groups, resulting in folding patterns like alpha helices and beta-pleated sheets.
• The tertiary structure involves further coiling and folding of the secondary structure due to interactions like hydrogen bonds, hydrophobic/hydrophilic interactions, and disulfide bonds between cysteine molecules.
• The quaternary structure is the arrangement of multiple polypeptide chains, if a protein is composed of more than one.
• Globular proteins, with their round and compact structure, are soluble and easily transported. Examples include amylase, insulin, and hemoglobin.
• Fibrous proteins, characterized by their tough, ladder-like structure, are insoluble and relatively unreactive. Examples include collagen, keratin, and elastin.

Explore the vital roles water and carbohydrates play in cellular processes and life. This quiz covers water's properties, including its solvent capabilities, temperature regulation, and molecular behavior, along with an introduction to carbohydrates. Test your understanding of these essential biomolecules and their importance to organisms.