Properties of Life and Biological Molecules

Characteristics of Living Things

All living organisms share certain fundamental properties that distinguish them from non-living matter.

• Cellular Organization: Living things are composed of one or more cells, which are the basic units of life.

• Metabolism: Organisms carry out chemical reactions to obtain and use energy.

• Homeostasis: Maintenance of stable internal conditions.

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Reproduction: Ability to produce new organisms.

• Response to Stimuli: React to environmental changes.

• Evolution: Populations change over time through adaptation and natural selection.

Atomic Structure

Atoms are the basic units of matter, consisting of protons, neutrons, and electrons.

• Nucleus: Contains protons (+) and neutrons (neutral).

• Electron Cloud: Electrons (-) orbit the nucleus in energy levels.

• Atomic Number: Number of protons in the nucleus.

• Mass Number: Sum of protons and neutrons.

Chemical Bonds

Atoms interact to form molecules through chemical bonds, which can be classified as ionic, covalent, or hydrogen bonds.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions.

• Covalent Bonds: Formed when atoms share electrons.

• Polar Covalent Bonds: Electrons are shared unequally, resulting in partial charges.

• Nonpolar Covalent Bonds: Electrons are shared equally.

• Hydrogen Bonds: Weak attractions between partially charged regions of molecules, especially in water.

Water: Properties and Importance

Water is essential for life due to its unique chemical and physical properties.

• Cohesion: Water molecules stick to each other via hydrogen bonds.

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water absorbs and retains heat, stabilizing temperatures.

• Solvent Properties: Water dissolves many substances, facilitating chemical reactions.

• Acid-Base Reactions: Water can participate in acid-base chemistry, acting as both an acid and a base.

Acids, Bases, and pH

Acids and bases are important in biological systems for maintaining pH balance.

• Acid: Substance that donates protons (H+).

• Base: Substance that accepts protons.

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic).

Biological Macromolecules

Carbon and Its Versatility

Carbon atoms can form diverse structures due to their ability to make four covalent bonds.

• Chains and Rings: Carbon forms long chains and ring structures, serving as the backbone for organic molecules.

• Functional Groups: Specific groups of atoms attached to carbon skeletons impart unique properties.

Polymers and Monomers

Biological macromolecules are polymers made from repeating monomer units.

• Polymerization: Monomers are joined by dehydration synthesis (removal of water).

• Depolymerization: Polymers are broken down by hydrolysis (addition of water).

Carbohydrates

Carbohydrates are energy sources and structural components in cells.

• Monosaccharides: Simple sugars (e.g., glucose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Polysaccharides: Long chains of monosaccharides (e.g., starch, cellulose).

Proteins and Amino Acids

Proteins are polymers of amino acids and perform diverse functions in cells.

• Amino Acids: Building blocks of proteins; differ by their side chains (R groups).

• Peptide Bonds: Link amino acids together.

• Protein Structure: Four levels—primary, secondary, tertiary, and quaternary.

• Function: Enzymes, structural support, transport, signaling.

Protein Folding and Function

• Primary Structure: Sequence of amino acids.

• Secondary Structure: Alpha helices and beta sheets formed by hydrogen bonding.

• Tertiary Structure: Overall 3D shape due to interactions among side chains.

• Quaternary Structure: Association of multiple polypeptide chains.

Lipids

Lipids are hydrophobic molecules important for energy storage and membrane structure.

• Fatty Acids: Long hydrocarbon chains; can be saturated or unsaturated.

• Triglycerides: Three fatty acids linked to glycerol.

• Phospholipids: Major component of cell membranes; have hydrophilic heads and hydrophobic tails.

• Steroids: Lipids with four fused rings (e.g., cholesterol).

Cell Structure and Function

Cell Membrane Structure

The cell membrane is a selectively permeable barrier composed of a phospholipid bilayer with embedded proteins.

• Phospholipid Bilayer: Hydrophilic heads face outward, hydrophobic tails face inward.

• Proteins: Integral and peripheral proteins serve as channels, receptors, and enzymes.

• Fluid Mosaic Model: Describes the dynamic nature of membrane components.

Membrane Transport

Cells regulate the movement of substances across membranes through various transport mechanisms.

• Passive Transport: Movement down a concentration gradient; includes diffusion and osmosis.

• Facilitated Diffusion: Transport via membrane proteins.

• Active Transport: Movement against a gradient using energy (ATP).

• Endocytosis and Exocytosis: Bulk transport of materials into and out of the cell.

Equation for Diffusion Rate:

Where is the flux, is the diffusion coefficient, and is the concentration gradient.

Prokaryotic vs. Eukaryotic Cells

Cells are classified as prokaryotic or eukaryotic based on their structure.

Eukaryotic Organelles and Functions

Eukaryotic cells contain specialized organelles that perform distinct functions.

• Nucleus: Stores genetic material (DNA).

• Mitochondria: Site of cellular respiration and energy production.

• Endoplasmic Reticulum (ER): Synthesizes proteins and lipids.

• Golgi Apparatus: Modifies, sorts, and packages proteins.

• Lysosomes: Digest cellular waste.

• Chloroplasts: Site of photosynthesis in plant cells.

Integration of Organelle Functions

Eukaryotic organelles work together to maintain cellular activities and homeostasis.

• Proteins synthesized in the ER are modified in the Golgi and transported to their destinations.

• Energy produced in mitochondria powers cellular processes.

• Genetic information in the nucleus directs cell function and division.

Summary Table: Macromolecules and Their Functions

Additional info: Academic context and examples have been added to expand upon the brief points in the original file and to ensure the notes are self-contained for study purposes.