Anatomy & Physiology: Organization, Biomolecules, and Metabolism Study Guide

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Organization of the Body

Systems and Functions

The human body is organized into systems that function together to ensure survival. Each system is composed of organs that work collaboratively to perform essential physiological tasks.

System Function: Systems as a whole allow the organism to survive. Example: The respiratory and circulatory systems work together to deliver oxygen to cells.
Simplification by Classification: Complex systems are easier to understand when broken down into constituent parts and classified (e.g., 200+ types of cells sorted into 4 main categories).

Cell Types and Tissues

Cells are classified into four basic types, each with distinct structure and function.

Nervous Tissue: Neurons and supporting cells; found in the brain, spinal cord, and nerves.
Muscle Tissue: Skeletal (voluntary), cardiac, and smooth (involuntary) muscle cells.
Epithelial Tissue: Covers body surfaces and lines cavities; involved in protection, secretion, and absorption.
Connective Tissue: Supports and binds other tissues (e.g., bone, fat, blood).

Tissue: A group of similar cells that function as a unit.

Organ: Composed of at least two tissue types; performs a specific function (e.g., heart, skeletal muscle).

Organ System: A collection of organs with a common task (e.g., the cardiovascular system).

Internal and External Environments

The body separates internal and external environments with a continuous epithelial membrane.

External Environment: Anything outside the epithelial membrane (e.g., air in lungs, GI tract contents).
Internal Environment: The environment within the epithelial membrane (e.g., blood, interstitial fluid).

Fluid Exchange and Compartments

Fluid exchange allows nutrients and oxygen to move in and wastes to move out.

Level	Examples
External	Air, GI tract contents
Plasma	Fluid portion of blood
Tissue fluid	Interstitial fluid
Cell	Intracellular fluid

Homeostasis

Mechanisms of Exchange

Homeostasis is the maintenance of a stable internal environment. It involves the exchange of nutrients, oxygen, and wastes between compartments.

Absorption: Nutrients and secretion (enzymes) in the GI tract.
Filtration: Movement of water and solutes (e.g., in kidneys).

Fluid Compartments

Intracellular Fluid (ICF): Fluid within cells.
Extracellular Fluid (ECF): Fluid outside cells, including plasma (in blood vessels) and interstitial fluid (between cells).

Homeostatic Control

Homeostasis is maintained by feedback mechanisms:

Negative Feedback: Reduces the error signal between the actual and set point value (e.g., body temperature regulation, blood glucose control).
Positive Feedback: Amplifies changes; not typically used for homeostasis (e.g., childbirth, LH & estrogen secretion).

Components of Homeostatic Systems

Receptors: Detect changes in the environment.
Integrating Centers: Process information and coordinate responses.
Effectors: Carry out responses to restore homeostasis.

Biomolecules

Carbohydrates

Carbohydrates are carbon-containing molecules synthesized by living things. They serve as a major energy source.

Monosaccharides: Simple sugars (e.g., glucose).
Disaccharides: Two monosaccharides linked (e.g., lactose).
Polysaccharides: Long chains of monosaccharides (e.g., glycogen).

Lipids

Lipids are hydrophobic molecules that include triglycerides, phospholipids, eicosanoids, steroids, and ketones.

Triglycerides: Energy storage; composed of glycerol and three fatty acids.
Phospholipids: Major component of cell membranes; amphipathic.
Steroids: Hormones and membrane components (e.g., cholesterol).
Saturated vs. Unsaturated Fatty Acids: Saturated have no double bonds; unsaturated have one or more double bonds.

Proteins

Proteins are polymers of amino acids with diverse functions, including catalysis, structure, and signaling.

Peptide Bonds: Link amino acids (see Figure 2.9).
Protein Structure: Primary, secondary, tertiary, and quaternary levels.
Importance: Structure determines function; temperature and pH can affect protein structure.

Nucleic Acids

Nucleic acids (DNA, RNA, ATP) store and transfer genetic information and energy.

DNA: Double-stranded; stores genetic information.
RNA: Single-stranded; involved in protein synthesis.
ATP: Main energy currency of the cell.

Cell Structure and Organelles

Plasma Membrane

The plasma membrane separates the cell from its environment and regulates movement of substances.

Components: Phospholipid bilayer, proteins, carbohydrates, cholesterol.
Functions: Barrier, communication, transport.

Organelles

Nucleus: Contains genetic material.
Ribosomes: Protein synthesis.
Endoplasmic Reticulum (Rough/Smooth): Protein and lipid synthesis.
Golgi Apparatus: Modifies and packages proteins.
Lysosomes/Peroxisomes: Digestion and detoxification.
Cytoskeleton: Structure, movement, and transport within the cell.

Cell Adhesion Structures

Tight Junctions: Seal adjacent cells to prevent leakage.
Desmosomes: Provide mechanical strength.
Gap Junctions: Allow communication between cells.

Metabolism and Enzymes

Metabolism Overview

Metabolism includes all chemical reactions in the body, divided into catabolism (breakdown) and anabolism (synthesis).

Catabolism: Breakdown of molecules to release energy.
Anabolism: Synthesis of complex molecules from simpler ones.

Types of Reactions

Hydrolysis: Catabolic; breaks bonds using water.
Condensation: Anabolic; forms bonds, releasing water.
Phosphorylation/Dephosphorylation: Addition/removal of phosphate groups.
Oxidation-Reduction: Transfer of electrons; oxidation is loss, reduction is gain of electrons.

Energy and Thermodynamics

Potential vs. Kinetic Energy: Stored vs. energy in motion.
First Law: Energy cannot be created or destroyed.
Second Law: Energy spreads out; some lost as heat.

Enzymes

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

Properties: Specificity, saturation, regulation by temperature and pH.
Models: Induced fit model explains enzyme-substrate interaction.
Coenzymes: Non-protein helpers (e.g., vitamins).

Regulation of Enzyme Activity

Allosteric Regulation: Binding at a site other than the active site changes enzyme activity.
Covalent Regulation: Chemical modification (e.g., phosphorylation).
Feedback Inhibition: End product inhibits an earlier step.

Cellular Respiration and Energy Metabolism

ATP and Energy Storage

ATP is the main energy currency of the cell, generated by substrate-level and oxidative phosphorylation.

Central Reaction:

Glucose Oxidation Pathway

Glycolysis: Occurs in cytoplasm; breaks glucose into pyruvate.
Linking Step: Pyruvate converted to acetyl-CoA.
Krebs Cycle: Acetyl-CoA enters cycle; produces NADH, FADH2, CO2.
Oxidative Phosphorylation (ETC): Electrons transferred to oxygen; produces most ATP.

Oxygen: Final electron acceptor in the ETC. In its absence, anaerobic metabolism occurs (e.g., lactic acid fermentation).

Other Metabolic Pathways

Glycogenolysis: Breakdown of glycogen to glucose.
Gluconeogenesis: Formation of glucose from non-carbohydrate sources.
Lipolysis: Breakdown of lipids for energy.
Protein Catabolism: Amino acids can be used for energy or converted to glucose.

Diabetes and Glucose Regulation

Type 1 Diabetes: Insulin deficiency; high blood glucose.
Type 2 Diabetes: Insulin resistance; high blood glucose.
Gestational Diabetes: Occurs during pregnancy; risk for type 2 diabetes later.
Diabetes Insipidus: Reduced ADH signaling; not related to blood glucose.
HbA1c: Glycated hemoglobin; indicates long-term glucose control.

Summary Table: Major Biomolecules

Type	Monomer	Function	Example
Carbohydrates	Monosaccharide	Energy, structure	Glucose, glycogen
Lipids	Fatty acid, glycerol	Energy storage, membranes	Triglyceride, phospholipid
Proteins	Amino acid	Catalysis, structure, signaling	Enzymes, hemoglobin
Nucleic Acids	Nucleotide	Genetic information, energy	DNA, RNA, ATP

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