Organizations of Life

Hierarchy of Life

Atom - Molecule - Macromolecule - Organelle - Cell- Tissue -Organ -Organ system- Organism

Inorganic Chemistry

Inorganic Chemistry: Mostly concerned with non-carbon-containing substances, but includes carbon monoxide, carbon dioxide, and bicarbonate ions.

Oxygen (O_2O_2): Inorganic molecule consisting of two oxygen atoms bound together by a double covalent bond. Required in the final step of cellular respiration to extract energy from food to make ATP.

Carbon Dioxide (CO_2): Consists of one carbon atom bound to two oxygen atoms. Produced when food molecules (e.g., glucose) are metabolized within cells; eliminated as a metabolic by-product via blood to the lungs and exhaled during respiration.

Water (H_2O): Inorganic molecule consisting of one oxygen atom joined by polar covalent bonds to two hydrogen atoms.

Functions: Stabilizes body temperature, provides protection, facilitates chemical reactions, and transports substances.

Organic Chemistry

Organic Chemistry: Organic molecules contain carbon atoms bound together by covalent bonds. The four major groups are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates: Provide the body with energy. Monosaccharides are the building blocks that form disaccharides and polysaccharides.

Lipids: Provide energy (fats), serve as structural components (phospholipids), and regulate physiological processes (eicosanoids and steroids).

Building blocks of fats: Glycerol (three-carbon molecule with a hydroxyl group attached to each carbon) and fatty acids (carbon chain with a carboxyl group attached at one end).

Proteins: Regulate chemical reactions (enzymes), act as structural components, and cause muscle contraction.

Building blocks: Amino acids joined by peptide bonds.

Structures: Primary, secondary, tertiary, and quaternary structures.

Enzymes: Large molecules (usually proteins) that act as catalysts to increase the rate of chemical reactions without being permanently changed. They work by lowering the activation energy (the minimum energy necessary to start a chemical reaction).

Nucleic Acids: The basic unit is the nucleotide (monosaccharide with an attached phosphate and organic base).

DNA: Contains deoxyribose and adenine, thymine, guanine, or cytosine. Double-stranded molecule that serves as the genetic material of cells.

RNA: Contains ribose and adenine, uracil, guanine, or cytosine (uracil replaces thymine).

Cell Structure and Functions

Main Functions of the Cell: Cell metabolism and energy use, synthesis of molecules, communication, reproduction and inheritance.

Plasma Membrane: Lipid bilayer composed of phospholipids and cholesterol with embedded proteins. Forms the outer boundary controlling entry and exit of substances, attaches to other cells/molecules, aids in intercellular communication/identification, and catalyzes chemical reactions.

Cytoplasm & Cytosol: Cytosol consists of water with dissolved ions and molecules (colloid with suspended proteins). Contains enzymes that catalyze the synthesis and breakdown of molecules.

Nucleus: Control center of the cell; contains genetic information.

Cytoplasmic Organelles:

Ribosome: Composed of rRNA and proteins (large and small subunits). Located on the ER or free in cytoplasm. Site of protein synthesis.

Rough Endoplasmic Reticulum (Rough ER): Membranous tubules and flattened sacs with attached ribosomes. Transports and modifies proteins.

Smooth Endoplasmic Reticulum (Smooth ER): Membranous tubules and flattened sacs without ribosomes. Manufactures lipids and carbohydrates, detoxifies harmful chemicals, and stores calcium.

Golgi Apparatus: Flattened membrane sacs stacked on each other. Modifies proteins and lipids and packages them into vesicles for distribution.

Lysosome: Membrane-bound vesicle pinched off from Golgi apparatus containing digestive enzymes.

Peroxisome: Membrane-bound vesicle; site of lipid and amino acid degradation; breaks down hydrogen peroxide.

Proteasomes: tube like protein complexes in cytoplasm that break down proteins.

Mitochondria: Double-membrane structure with inner cristae. Major site of ATP synthesis.

Centrioles: Pair of cylindrical organelles in the centrosome consisting of triplets of parallel microtubules. Serve as centers for microtubule formation and determine cell polarity during cell division.

Movement Through the Plasma Membrane

Selectively Permeable Membrane: Allows specific substances to pass while restricting others to maintain intracellular fluid composition.

Passive Transport: Movement of molecules down a concentration gradient without requiring energy.

Active Transport: Movement of molecules against a concentration gradient using energy.

Transport Mechanisms

Diffusion: Movement of ions/molecules from an area of higher concentration to lower concentration in a solution.

Solution: Mixture of liquids, gases, or solids uniformly distributed.

Solute: Substance dissolved in solution.

Solvent: Substance that dissolves the solute.

Concentration Gradient: Difference in concentration between two points divided by distance.

Permeability: Lipid-soluble molecules diffuse directly through the lipid bilayer; non-lipid-soluble molecules require membrane channels or transport proteins.

Osmosis: Movement of water across a selectively permeable membrane. Uses water channels called aquaporins for rapid movement.

Osmotic Pressure: Force required to prevent water movement across a membrane.

Hypotonic Solution: Lower solute concentration than body fluids; water enters cell causing it to swell or burst (lyse).

Isotonic Solution: Equal solute concentration; no net water movement.

Hypertonic Solution: Higher solute concentration than body fluids; water leaves cell causing it to shrink (crenate).

Mediated Transport: Transport proteins assist movement across the membrane.

Characteristics: Specificity (moves specific ions/molecules), Competition (similar molecules compete for transport), Saturation (rate limited by available transport proteins).

Channel Proteins: Form membrane channels (e.g., ion channels) for passage.

Carrier Proteins (Transporters): Bind to specific molecules on one side, change shape, and release them on the other side (e.g., uniporter moving glucose).

ATP-Powered Pumps: Use energy from ATP breakdown to move substances against concentration gradient (active transport).

Secondary Active Transport: Uses energy from an established gradient (e.g., Na^+-K+pump setting up a Na+gradient) to move another substance (e.g., glucose via symporter) against its gradient.

Vesicular Transport: Movement of materials by membrane-bound sacs (vesicles).

Endocytosis: Vesicle transport into cells (includes Phagocytosis for solid particles and Pinocytosis for liquid).

Exocytosis: Vesicle transport of materials out of cells.