Levels of Organization and Homeostasis

Levels of Organization

• Atoms and molecules are the basic chemical building blocks (e.g., proteins, lipids, carbohydrates, nucleic acids).
• Cells are the basic units of life. Unicellular organisms consist of one cell, while multicellular organisms have multiple cells.
• Tissues are groups of similar cells working together to perform specific functions (e.g., epithelial, connective, muscle, nervous tissue).
• Organs are structures composed of various tissues performing a specific role (e.g., heart, lungs, skin, stomach).
• Organ systems are groups of organs working together (e.g., cardiovascular, respiratory, digestive systems).
• An organism is the complete living being composed of organ systems interacting.

Homeostasis

• Homeostasis is the body's ability to maintain a stable internal environment despite external changes (e.g., temperature, blood glucose, pH).
• Homeostasis is maintained via feedback loops involving receptors, control centers (e.g., brain), and effectors.
• Disturbed homeostasis results in illness, disease, and even death.

Feedback Loops

• Feedback loops maintain homeostasis by detecting changes and initiating corrective processes.
• Factors like heart rate (HR) are monitored by sensors.
• Controlled centers like the brain process information and initiate responses.
• Effectors restore conditions to their normal values.
• Typically feedback mechanisms are negative, meaning they work to reverse a change.

Anatomical Planes

• Sagittal Plane: divides the body into right and left portions.
• Frontal Plane: divides the body into anterior (front) and posterior (back) portions.
• Transverse Plane: divides the body into superior (upper) and inferior (lower) portions.

Chemical Bonds

• Atoms form chemical bonds to achieve a stable electron configuration (octet rule).
• Atoms with incomplete outer shells are reactive and want to bond.
• Ionic bonds occur from the exchange of electrons, forming positively and negatively charges ion.
• Covalent bonds form when atoms share pairs of electrons.
• Hydrogen bonds are weak attractions between a hydrogen atom and an electronegative atom like oxygen or nitrogen.

Chemical Reactions

• Chemical reactions involve breaking and forming chemical bonds, either releasing or requiring energy.
• Catabolism involves breaking down molecules and releasing energy.
• Anabolism involves building molecules and requiring energy.
• Decomposition reactions break down complex molecules into smaller ones.
• Synthesis reactions combine small molecules to form larger ones (dehydration synthesis).

Water Properties

• Water is a polar molecule with unequal electron sharing, resulting in partial charges.
• Water is a universal solvent, dissolving many ionic and polar compounds.
• Water has a high heat capacity (ability to absorb heat without large temperature increases.)
• Water has a high heat of vaporization requiring a lot of energy to turn into gas.
• Water molecules exhibit cohesion and adhesion. Cohesion is the attraction between like molecules (e.g., water and water.) Adhesion is the attraction between unlike molecules (e.g., water and a glass surface.)
• Water has surface tension due to the hydrogen bonding between water molecules.

Organic Compounds

• Carbohydrates: primary energy source; composed of carbon, hydrogen, and oxygen; often in a (CH₂O)n ratio.
  • Monosaccharides (simple sugars): building blocks (glucose).
  • Disaccharides (double sugars): formed from two monosaccharides (sucrose).
  • Polysaccharides (complex carbohydrates): long chains of monosaccharides (starch, glycogen, cellulose).
• Lipids: diverse hydrophobic group; composed primarily of carbon and hydrogen; insoluble in water.
  • Fatty acids: unbranched hydrocarbon chains with a carboxyl group; saturated (no double bonds) or unsaturated (double bonds between carbons).
  • Triglycerides: three fatty acids attached to glycerol; major energy storage.
  • Phospholipids: two fatty acids and a phosphate group attached to glycerol; primary component of cell membranes.
  • Steroids: four interconnected rings of carbon atoms (cholesterol, hormones).
• Proteins: composed of amino acids linked by peptide bonds; crucial for structure, function, and regulation.
• Nucleic acids: store and transmit genetic information; composed of nucleotides (DNA, RNA).

Cellular Respiration

• Glycolysis: glucose breakdown into pyruvic acid; occurs in the cytosol; yields a small amount of ATP.
• Formation of Acetyl CoA: conversion of pyruvic acid into acetyl CoA which enters the citric acid cycle.
• Citric Acid Cycle: completes oxidation of glucose to acetyl CoA, releasing CO₂ and producing electron carriers (NADH and FADH₂); takes place in mitochondria.
• Electron Transport Chain: electrons from NADH and FADH₂ are passed along a chain, generating a proton gradient; ATP synthesis occurs through oxidative phosphorylation; takes place in mitochondria.

Gluconeogenesis

• Gluconeogenesis is the process of making new glucose from non-carbohydrate sources (e.g., amino acids, glycerol)

Explore the hierarchical organization of life from atoms to organisms. Understand how cells form tissues, tissues form organs, and organs form systems. Learn about homeostasis, the body's mechanism for maintaining a stable internal environment through feedback loops.