Survival Needs and Requirements for Life

Five Survival Needs

Organisms require certain conditions to survive and maintain homeostasis. These survival needs are fundamental for cellular and systemic function.

• Nutrients: Chemical substances used for energy and cell building.

• Oxygen: Required for cellular respiration and energy production.

• Water: The most abundant chemical in the body, vital for chemical reactions and transport.

• Stable Body Temperature: Necessary for proper metabolic reactions.

• Appropriate Atmospheric Pressure: Essential for breathing and gas exchange.

Five Things Necessary for Life

In addition to survival needs, life requires certain processes and conditions:

• Metabolism: All chemical reactions in the body.

• Responsiveness: Ability to sense and respond to stimuli.

• Movement: Includes locomotion and movement of substances.

• Growth: Increase in size and number of cells.

• Reproduction: Production of offspring.

Homeostasis and Feedback Loops

Homeostasis

Homeostasis is the maintenance of a stable internal environment despite external changes. It is achieved through feedback mechanisms.

• Negative Feedback: Reduces the effect of the stimulus (e.g., regulation of body temperature).

• Positive Feedback: Enhances the effect of the stimulus (e.g., blood clotting, childbirth).

Example: When body temperature rises, negative feedback mechanisms (such as sweating) help lower it back to normal.

Basic Chemistry for Anatomy & Physiology

Elements and Subatomic Particles

An element is a pure substance consisting of only one type of atom. Atoms are composed of:

• Proton: Charge: +1, Weight: 1 amu, Location: Nucleus

• Neutron: Charge: 0, Weight: 1 amu, Location: Nucleus

• Electron: Charge: -1, Weight: ~0 amu, Location: Electron cloud/orbitals

Types of Mixtures

Mixtures are combinations of two or more substances physically blended together.

• Solutions: Homogeneous mixtures (e.g., salt water).

• Colloids: Heterogeneous mixtures with larger particles (e.g., cytoplasm).

• Suspensions: Particles settle out over time (e.g., blood).

Chemical Bonds

Chemical bonds hold atoms together in molecules and compounds.

• Ionic Bonds: Transfer of electrons between atoms, forming charged ions.

• Covalent Bonds: Sharing of electrons between atoms.

• Hydrogen Bonds: Weak attractions between polar molecules.

Chemical Reactions

Chemical reactions involve the making or breaking of bonds between atoms.

• Synthesis Reaction: (e.g., formation of proteins from amino acids)

• Decomposition Reaction: (e.g., breakdown of glycogen)

• Exchange Reaction:

Endergonic vs. Exergonic Reactions

Reactions can be classified by their energy changes:

• Endergonic: Absorb energy; products have more energy than reactants.

• Exergonic: Release energy; products have less energy than reactants.

Example: ATP synthesis is endergonic; ATP hydrolysis is exergonic.

Factors Influencing Chemical Reaction Rates

• Temperature: Higher temperature increases reaction rate.

• Concentration: Higher concentration increases reaction rate.

• Catalysts: Enzymes speed up reactions.

• Particle Size: Smaller particles react faster.

Properties of Water Vital to Life

• High Heat Capacity: Absorbs and releases heat slowly.

• Polarity/Solvency: Universal solvent for many substances.

• Chemical Reactivity: Participates in hydrolysis and dehydration reactions.

• Cushioning: Protects organs (e.g., cerebrospinal fluid).

Acids, Bases, and pH

Acids and bases are substances that alter the concentration of hydrogen ions in a solution.

• Acids: Release ions; pH < 7.

• Bases: Release ions; pH > 7.

• pH Scale: Measures hydrogen ion concentration;

Example: Stomach acid (pH ~2) vs. blood (pH ~7.4).

Buffers

Buffers resist changes in pH by absorbing or releasing ions.

• Example: Bicarbonate buffer system in blood:

Biomolecules: Structure and Function

Carbohydrates

• Monomers: Monosaccharides (e.g., glucose).

• Polymerization: Joined by dehydration synthesis to form disaccharides and polysaccharides.

Example: Glucose + Glucose Maltose + Water

Lipids

• Fatty Acids: Long hydrocarbon chains with a carboxyl group.

• Triglycerides: Glycerol + 3 fatty acids.

• Phospholipids: Glycerol + 2 fatty acids + phosphate group; major component of cell membranes.

Proteins

• Monomers: Amino acids.

• Polymerization: Joined by peptide bonds (dehydration synthesis).

• Protein Folding: Process by which a polypeptide assumes its functional shape (primary, secondary, tertiary, quaternary structure).

Nucleic Acids

• Monomers: Nucleotides (composed of a sugar, phosphate, and nitrogenous base).

• Polymerization: Joined by phosphodiester bonds to form DNA and RNA.

Cell Structure and Function

Cellular Components Outside the Cell

• Extracellular Matrix: Network of proteins and carbohydrates outside cells.

• Interstitial Fluid: Fluid between cells.

• Cell Junctions: Structures connecting cells.

Plasma Membrane

The plasma membrane is a selectively permeable barrier that surrounds the cell.

• Phospholipid Bilayer: Provides fluidity and barrier function.

• Proteins: Serve as channels, receptors, and enzymes.

• Carbohydrates: Involved in cell recognition.

• Cholesterol: Stabilizes membrane fluidity.

Specialized Cell Junctions

• Tight Junctions: Prevent leakage between cells.

• Desmosomes: Anchor cells together.

• Gap Junctions: Allow communication between cells.

Diffusion and Osmosis

• Diffusion: Movement of molecules from high to low concentration.

• Simple Diffusion: Direct movement through membrane.

• Facilitated Diffusion: Movement via protein channels.

• Osmosis: Diffusion of water across a selectively permeable membrane.

Example: RBC in hypertonic solution shrinks; in hypotonic solution swells; in isotonic solution remains unchanged.

Sodium-Potassium Pump

The sodium-potassium pump is an active transport mechanism that moves out and into the cell against their concentration gradients, using ATP.

• Function: Maintains electrochemical gradients essential for nerve impulse transmission.

• Mechanism: 3 out, 2 in per ATP hydrolyzed.

Equation:

*Additional info: Some explanations and examples were expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.*