Anatomy & Physiology: Foundations, Cellular Processes, and Laboratory Principles

Introduction, Homeostasis, and Feedback

Homeostasis and Feedback Mechanisms

Homeostasis is the process by which living organisms maintain a stable internal environment despite changes in external conditions. Feedback mechanisms are essential for regulating physiological variables.

• Homeostasis: The maintenance of a constant internal environment (e.g., temperature, pH, glucose levels).

• Feedback Loops: Systems that respond to changes by initiating responses that restore balance.

• Positive Feedback: Amplifies changes (e.g., blood clotting, childbirth).

• Negative Feedback: Counteracts changes to maintain stability (e.g., regulation of blood glucose).

• Responsiveness: The ability of feedback loops to detect and respond to changes in variables.

• Antagonistic Effectors: Opposing effectors that help maintain homeostasis (e.g., insulin and glucagon).

Chemical Nature of the Body

Atomic Structure and Chemical Bonds

Atoms are the basic units of matter, and chemical bonds form when atoms share or transfer electrons to achieve stability.

• Atomic Structure: Protons, neutrons, and electrons; electron shells determine reactivity.

• Chemical Bonds: Ionic, covalent, and hydrogen bonds.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Acids, Bases, pH Scale: Acids donate protons, bases accept protons; pH measures hydrogen ion concentration.

Organic Molecules and Macromolecules

Organic molecules contain carbon backbones and functional groups that confer specific properties. Four major macromolecules are essential for life.

• Carbohydrates: Energy source; building blocks are monosaccharides.

• Lipids: Energy storage, membrane structure; building blocks are fatty acids and glycerol.

• Proteins: Structure, enzymes, signaling; building blocks are amino acids.

• Nucleic Acids: Genetic information; building blocks are nucleotides.

• Polymerization: Formation of large molecules from smaller subunits (e.g., dehydration synthesis).

Life and Death of Cells

Cell Structure and Function

Cells are the basic units of life, with specialized organelles performing distinct functions.

• Cytoskeleton: Provides structural support and facilitates movement.

• Organelles: Nucleus (genetic material), mitochondria (energy production), endoplasmic reticulum (protein/lipid synthesis), Golgi apparatus (modification and transport).

Cell Division and Death

• Apoptosis: Programmed cell death, essential for development and tissue homeostasis.

• Necrosis: Uncontrolled cell death due to injury or disease.

• Hallmarks of Cancer: Uncontrolled cell division, evasion of apoptosis, and other features.

Nuclear Processes

Genetic Material and Inheritance

Genetic information is stored in DNA and transmitted through cellular processes.

• Nucleotides: Building blocks of DNA and RNA; consist of a sugar, phosphate, and nitrogenous base.

• DNA Replication: Process by which DNA is copied before cell division.

• Transcription: Synthesis of RNA from DNA template.

• Translation: Synthesis of proteins from RNA template.

• Mutations: Changes in DNA sequence; can be spontaneous or induced, with various effects.

• Differential Gene Expression: Regulation of which genes are expressed in different cell types.

Enzymes and Energy

Enzyme Function and Regulation

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• Enzyme: Protein that catalyzes reactions.

• Substrate: Molecule upon which an enzyme acts.

• Product: Result of the enzymatic reaction.

• Active Site: Region of enzyme where substrate binds.

• Affinity: Strength of substrate binding.

• Cofactor/Coenzyme: Non-protein helpers required for enzyme activity.

• Enzyme Activity Regulation: Up- and down-regulation, competitive and noncompetitive inhibition.

Michaelis-Menten Kinetics:

• Describes the rate of enzymatic reactions as a function of substrate concentration.

$V = \frac{V_{max}[S]}{K_m + [S]}$

• Endergonic vs. Exergonic Reactions: Endergonic reactions require energy input; exergonic reactions release energy.

• Laws of Thermodynamics: Govern energy transformations in biological systems.

Cellular Metabolism

Energy Storage and Metabolic Pathways

Cells store and utilize energy through metabolic pathways involving ATP and electron carriers.

• Basal Metabolic Rate (BMR): Minimum energy required for basic physiological functions.

• ATP Hydrolysis: Breaking ATP to release energy.

$ATP + H_2O \rightarrow ADP + P_i + \text{energy}$

• Phosphorylation: Addition of phosphate group to a molecule.

• Electron Carriers: NAD+, FAD; transport electrons in metabolic pathways.

• Redox Reactions: Oxidation-reduction reactions transfer electrons between molecules.

• Oxidative Phosphorylation: ATP production using electron transport chain.

• Substrate-Level Phosphorylation: Direct transfer of phosphate to ADP.

• Glycolysis, Citric Acid Cycle, ETC: Pathways for energy extraction from glucose.

• Chemiosmosis Theory: ATP synthesis driven by proton gradient across membranes.

• Fermentation: Anaerobic process for ATP production when oxygen is limited.

Membranes and Membrane Transport

Structure and Function of Membranes

Cell membranes are selectively permeable barriers composed of lipids and proteins, regulating transport and communication.

• Membrane Challenges: Maintaining integrity, selective transport, and communication.

• Components: Phospholipid bilayer, proteins, cholesterol.

Membrane Transport Processes

• Passive Diffusion: Movement of molecules down concentration gradient without energy input.

• Facilitated Diffusion: Passive transport via membrane proteins.

• Osmosis: Diffusion of water across a semipermeable membrane.

• Carrier-Mediated Transport: Involves specific membrane proteins.

• Endocytosis: Uptake of materials via vesicle formation.

• Exocytosis: Release of materials from cells via vesicles.

• Pinocytosis: Uptake of fluids by cells.

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

• Gradients: Differences in concentration or charge drive many transport processes.

Laboratory Material

Scientific Method and Experimentation

Laboratory skills are essential for understanding and applying scientific principles in Anatomy & Physiology.

• Scientific Method: Systematic approach to investigation (observation, hypothesis, experiment, analysis, conclusion).

• Experimentation: Designing and conducting experiments to test hypotheses.

Serum Analysis and Spectrophotometry

• Beer’s Law: Relates absorbance to concentration of a solute.

$A = \varepsilon l c$

• Spectrophotometer: Instrument used to measure absorbance of solutions.

• Standard Curve: Graph used to determine unknown concentrations.

• Normal Levels: Glucose, protein, cholesterol in plasma/serum.

Enzyme Function and Osmolarity

• Enzyme Activity: Factors affecting rate, substrate concentration, energy of activation.

• Osmolarity: Measure of solute concentration.

• Tonicity: Effect of solution on cell volume (isotonic, hypertonic, hypotonic).

• Penetrating/Non-Penetrating Solutes: Determines movement of water and solutes across membranes.

Example Table: Types of Membrane Transport

Transport Type	Energy Required?	Direction	Carrier Protein?
Passive Diffusion	No	Down gradient	No
Facilitated Diffusion	No	Down gradient	Yes
Active Transport	Yes (ATP)	Against gradient	Yes
Endocytosis/Exocytosis	Yes	Bulk transport	No

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