Water in Biology

Water in Biology

• Water's chemical formula is H₂O.
• Biological systems largely consist of water, with interactions involving it vital for life.
• Water's polarity stems from oxygen's electronegativity, making the oxygen side slightly negative and the hydrogens slightly positive.
• Hydrogen bonds—weak attractions between water molecules—result from this polarity, crucial for water's properties.
• Hydrophilic molecules interact favorably with water; hydrophobic molecules do not.
• Cohesion describes hydrogen bonds between water molecules; adhesion describes bonds between water and other polar surfaces.
• Cohesion leads to surface tension, making water's surface difficult to break.
• Water's polarity and hydrogen bonds give it high solvency, dissolving many substances, a "universal solvent".
• Ice is less dense than liquid water due to hydrogen bonding, a key factor in aquatic life, allowing life beneath the ice.
• Water's high specific heat and high heat of vaporization help regulate temperature, essential for homeostasis.
• Capillary action combines cohesion and adhesion to allow water to move against gravity in narrow tubes.
• Water is essential for all biological environments and interactions.

Biological Macromolecules

• Macromolecules are essential for an organism’s function, and are made up of Carbon, Hydrogen, Oxygen, and other elements.
• Carbon is central to macromolecule structure, forming up to four covalent bonds, creating carbon skeletons.
• A monomer is a single unit in a macromolecule.
• Polymers are large molecules formed by joining monomers.

Carbohydrates

• Carbohydrate chemical formula is C₆H₁₂O₆.
• Carbohydrate elements are carbon, hydrogen, and oxygen.
• Carbohydrates function as energy storage, structural materials, and raw materials.

Types of Carbohydrates

• Monosaccharides are simple sugars, the monomers of carbohydrates.
• Polysaccharides are complex carbohydrates like starch, glycogen, cellulose, and chitin, consisting of many monosaccharides.
• Glucose is a common monosaccharide; isomers have identical formulas but different structures.
• Starch is a plant energy storage polysaccharide (linear); glycogen is an animal energy storage polysaccharide (branched).
• Cellulose forms plant cell walls (linear, with beta linkages); chitin is found in exoskeletons and fungal cell walls (beta structure).
• Alpha glucose forms starch and glycogen; beta glucose forms cellulose and chitin.
• Glycosidic linkages are covalent bonds between monosaccharides, formed by dehydration synthesis.

Lipids

• Lipids are mainly composed of carbon and hydrogen, with some oxygen.
• Fats are made up of glycerol and fatty acid tails, functioning in long-term energy storage, insulation, and cushioning.
• Ester linkages bind glycerol to fatty acids.
• Saturated fats have no C=C double bonds (straight chains); unsaturated fats have C=C double bonds (bent chains).
• Phospholipids are key components of cell membranes. (glycerol + 2 fatty acids + phosphate group).
• Steroids have four fused carbon rings and include cholesterol, which is crucial for cell membranes.

Proteins

• Proteins are highly diverse biological macromolecules composed of CHON and sometimes sulfur.
• Amino acids are the monomer units of proteins, with each distinct R group, which determines function.
• Polypeptides are polymers of amino acids.
• Peptide bonds link amino acids.
• The polypeptide backbone is the repeating N-C-C sequence in a protein chain.
• N-terminus and C-terminus are the ends of a polypeptide chain.
• A protein's primary structure is its unique amino acid sequence.
• The secondary structure involves local folding like alpha helices and beta pleated sheets.
• Tertiary structure is the overall 3-D shape of a polypeptide, determined by interactions of R groups like hydrogen bonds, ionic bonds, and disulfide bridges.
• Quaternary structure describes interactions between multiple polypeptide chains in a protein.
• Denaturation is a protein's loss of shape and function due to changes in pH, temperature, or salt.

Nucleic Acids

• Nucleic acids (DNA and RNA) store and transmit genetic information.
• Nucleic acids consist of CHONP.
• Nucleotides are the monomers of nucleic acids (sugar + phosphate + nitrogenous base).
• DNA is a double helix with antiparallel strands composed of deoxyribose.
• DNA bases are adenine, guanine, cytosine, and thymine (A-T, G-C).
• RNA is single-stranded and contains ribose and the nitrogenous bases adenine, guanine, cytosine, and uracil.

Cell Structure

• Cells are the basic units of life.
• Prokaryotic cells are smaller and lack a nucleus or membrane-bound organelles.
• Eukaryotic cells are larger and complex, containing a nucleus and membrane-bound organelles.
• Organelles are specialized cell components with specific functions.
• Ribosomes are involved in protein synthesis; they are comprised of ribosomal RNA (rRNA) and proteins in large and small subunits.

Energy in Biological Systems

• Energy is the ability to do work, needed for all living systems and organisms to function.
• Energy is conserved, not created or destroyed. Organisms take in energy from the environment.
• Structure and function are related. Changes in structure can lead to changes in function.