Introduction to Biology and Water's Properties

• Biology is the scientific study of life, exploring its diverse forms and processes

Themes in the Study of Life

• Biology's scope is vast, ranging from microscopic molecules to the global ecosystem
• Evolution is the core theme, explaining the unity and diversity of life
• New properties emerge at each level in the biological hierarchy
• Life's processes involve the expression and transmission of genetic information
• Life requires the transfer and transformation of energy and matter
• Organisms interact with each other and their environments
• Science is a process of inquiry that includes observation, experimentation, and analysis

Water

• Water is essential for life due to its unique properties
• Water molecules are polar, with partial positive charges on hydrogen and a partial negative charge on oxygen
• Hydrogen bonds form between water molecules, contributing to cohesion
• Cohesion results in surface tension, allowing some organisms to walk on water
• Water has a high specific heat, meaning it can absorb or release a lot of heat without changing temperature much
• This helps stabilize temperatures in organisms and environments
• Water has a high heat of vaporization, requiring much energy to evaporate
• Evaporation cools surfaces, like leaves or human skin
• Water is less dense as a solid than as a liquid
• Ice floats, insulating water below and allowing aquatic life to survive in winter
• Water is a versatile solvent due to its polarity
• It can dissolve ionic compounds and polar molecules
• Hydrophilic substances have an affinity for water
• Hydrophobic substances do not mix with water
• Acids increase the H+ concentration in water, while bases reduce it
• The pH scale measures acidity and alkalinity
• Buffers minimize pH changes by accepting or donating H+ ions

Carbon

• Carbon is the backbone of life, forming large, complex and diverse molecules
• Carbon has 4 valence electrons, allowing it to form 4 covalent bonds
• Carbon can bond with other carbon atoms, forming chains or rings
• Isomers are compounds with the same molecular formula but different structures and properties

The Structure and Function of Large Biological Molecules

• Large biological molecules are polymers, chains of repeating monomers
• Carbohydrates include sugars and polymers of sugars
• Monosaccharides are simple sugars like glucose and fructose
• Polysaccharides are complex carbohydrates like starch, glycogen, and cellulose
• Lipids are hydrophobic molecules, and include fats, phospholipids, and steroids
• Fats are composed of glycerol and fatty acids and store energy
• Saturated fatty acids have no double bonds, while unsaturated have one or more
• Phospholipids have a polar head and a nonpolar tail, forming cell membranes
• Steroids have a carbon skeleton of four fused rings, such as cholesterol
• Proteins are polymers of amino acids
• Amino acids have an amino group, a carboxyl group, and a variable R group
• Peptide bonds link amino acids together
• A protein's structure determines its function
• There are four levels of protein structure: primary, secondary, tertiary, and quaternary
• Nucleic acids store and transmit genetic information
• DNA and RNA are polymers of nucleotides
• Nucleotides consist of a sugar, a phosphate group, and a nitrogenous base
• DNA is double-stranded, with the bases adenine (A), guanine (G), cytosine (C), and thymine (T)
• RNA is single-stranded, with uracil (U) instead of thymine

The Eukaryotic Cell

• Eukaryotic cells have internal membranes that compartmentalize functions
• The nucleus contains the cell's DNA and controls the cell's activities
• Ribosomes synthesize proteins
• The endoplasmic reticulum (ER) is a network of membranes involved in protein and lipid synthesis
• The Golgi apparatus modifies, sorts, and packages proteins
• Lysosomes contain enzymes that digest cellular waste
• Vacuoles store water, ions, and other molecules
• Mitochondria generate ATP through cellular respiration
• Chloroplasts (in plant cells) perform photosynthesis
• The cytoskeleton provides structural support and facilitates movement
• The plasma membrane is the outer boundary of the cell, controlling what enters and exits

Bacteria and Archaea

• Bacteria and Archaea are prokaryotic cells, lacking a nucleus and other membrane-bound organelles
• Bacteria have peptidoglycan in their cell walls
• Archaea have unique lipids in their cell membranes
• Prokaryotes reproduce asexually through binary fission
• Genetic variation arises through mutation, transduction, transformation, and conjugation
• Prokaryotes play important roles in ecosystems as decomposers, producers, and pathogens
• Some bacteria are beneficial, such as those in the human gut that aid in digestion, while others can cause infections that result in diseases
• Archaea are found in extreme environments, such as hot springs and salt lakes
• Many archaea are methanogens, producing methane as a waste product

Explore the fundamental aspects of biology, from its broad scope to the central theme of evolution. Understand how emergent properties arise in the biological hierarchy and the importance of genetic information. Learn about water's unique properties, including polarity, hydrogen bonds, and cohesion, vital for life.