Anatomy and Physiology I

💀Anatomy and Physiology I Unit 2 – The Chemical Level of Organization

The Chemical Level of Organization explores the fundamental building blocks of life. It covers atoms, molecules, and chemical bonds, explaining how these components interact to form the substances that make up living organisms. This unit delves into the elements and molecules found in the human body, chemical reactions in biological systems, pH balance, and organic compounds. It also introduces energy and metabolism basics, providing a foundation for understanding human physiology.

Key Concepts and Terminology

  • Matter anything that occupies space and has mass
  • Atoms the smallest unit of matter that retains the properties of an element
  • Elements substances that cannot be broken down into simpler substances by chemical means (oxygen, carbon, hydrogen)
  • Molecules two or more atoms held together by chemical bonds
  • Compounds molecules that contain at least two different elements (water, glucose)
  • Chemical bonds attractive forces that hold atoms together in molecules or compounds
    • Covalent bonds involve the sharing of electrons between atoms
    • Ionic bonds involve the transfer of electrons from one atom to another
  • Chemical reactions processes in which one or more substances are converted into one or more different substances
  • Metabolism the sum of all chemical reactions that occur in the body to maintain life

Atomic Structure and Chemical Bonds

  • Atoms consist of protons, neutrons, and electrons
    • Protons positively charged particles located in the nucleus
    • Neutrons neutral particles located in the nucleus
    • Electrons negatively charged particles that orbit the nucleus in shells
  • Atomic number the number of protons in an atom determines the element's identity
  • Mass number the sum of the number of protons and neutrons in an atom
  • Isotopes atoms of the same element with different numbers of neutrons
  • Chemical bonds form when atoms share, gain, or lose electrons to achieve a stable electron configuration
  • Covalent bonds occur when atoms share electrons
    • Single covalent bonds involve the sharing of one pair of electrons (H₂)
    • Double covalent bonds involve the sharing of two pairs of electrons (O₂)
  • Ionic bonds occur when electrons are transferred from one atom to another, creating ions (NaCl)

Elements and Molecules in the Human Body

  • The human body is composed of various elements, with oxygen, carbon, hydrogen, and nitrogen being the most abundant
  • Trace elements are required in small amounts for proper functioning (iron, zinc, copper)
  • Water (H₂O) is the most abundant molecule in the body, making up ~60% of total body weight
    • Water serves as a solvent, reactant, and product in many biological processes
    • Water helps regulate body temperature through evaporation and perspiration
  • Glucose (C₆H₁₂O₆) is a simple sugar that serves as a primary energy source for cells
  • Amino acids are the building blocks of proteins and contain an amino group (NH₂) and a carboxyl group (COOH)
  • Nucleotides are the building blocks of nucleic acids (DNA and RNA) and consist of a nitrogenous base, a sugar, and a phosphate group

Chemical Reactions in Biological Systems

  • Chemical reactions involve the breaking and forming of chemical bonds
  • Reactants the substances that enter a chemical reaction
  • Products the substances that are formed as a result of a chemical reaction
  • Enzymes biological catalysts that speed up chemical reactions without being consumed in the process
    • Enzymes work by lowering the activation energy required for a reaction to occur
    • Enzymes are highly specific, typically catalyzing only one type of reaction
  • Metabolism involves two types of chemical reactions: anabolism and catabolism
    • Anabolism building complex molecules from simpler ones, requiring energy input
    • Catabolism breaking down complex molecules into simpler ones, releasing energy
  • Cellular respiration a series of catabolic reactions that break down glucose to release energy in the form of ATP

pH and Buffers in Human Physiology

  • pH a measure of the concentration of hydrogen ions (H⁺) in a solution
    • pH scale ranges from 0 to 14, with 7 being neutral, < 7 acidic, and > 7 basic
  • Acids substances that donate hydrogen ions (H⁺) to a solution (hydrochloric acid)
  • Bases substances that accept hydrogen ions (H⁺) from a solution (sodium hydroxide)
  • Buffers solutions that resist changes in pH when small amounts of acids or bases are added
    • Buffers work by absorbing excess H⁺ or OH⁻ ions, maintaining a relatively stable pH
  • The human body maintains a narrow pH range (7.35-7.45) in the blood and other tissues for optimal function
    • Bicarbonate buffer system helps maintain blood pH by absorbing or releasing H⁺ ions
    • Respiratory system helps regulate blood pH by adjusting the rate and depth of breathing, affecting CO₂ levels
  • Acidosis a condition in which the blood pH falls below 7.35, can be caused by metabolic or respiratory disorders
  • Alkalosis a condition in which the blood pH rises above 7.45, can be caused by metabolic or respiratory disorders

Organic Compounds and Biomolecules

  • Organic compounds contain carbon and are the building blocks of life
  • Carbohydrates organic compounds composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio (glucose, starch)
    • Monosaccharides simple sugars that serve as the building blocks of more complex carbohydrates (glucose, fructose)
    • Disaccharides formed when two monosaccharides are joined by a glycosidic bond (sucrose, lactose)
    • Polysaccharides long chains of monosaccharides (starch, cellulose, glycogen)
  • Lipids organic compounds that are insoluble in water and include fats, oils, and waxes
    • Triglycerides consist of three fatty acids attached to a glycerol backbone, serve as energy storage and insulation
    • Phospholipids consist of two fatty acids and a phosphate group attached to a glycerol backbone, form cell membranes
  • Proteins organic compounds composed of amino acids linked by peptide bonds
    • Enzymes, hormones, and antibodies are examples of proteins with specific functions in the body
  • Nucleic acids organic compounds that store and transmit genetic information (DNA, RNA)

Energy and Metabolism Basics

  • Energy the capacity to do work or cause change
  • ATP (adenosine triphosphate) the primary energy currency of the cell
    • ATP consists of an adenosine molecule and three phosphate groups
    • Energy is released when the terminal phosphate group is removed, forming ADP (adenosine diphosphate)
  • Cellular respiration the process by which cells break down glucose to release energy in the form of ATP
    • Glycolysis the first stage of cellular respiration, occurs in the cytoplasm and produces 2 ATP
    • Citric acid cycle the second stage of cellular respiration, occurs in the mitochondrial matrix and produces 2 ATP and high-energy electrons
    • Electron transport chain the final stage of cellular respiration, occurs in the mitochondrial inner membrane and produces the majority of ATP (34 ATP)
  • Metabolism the sum of all chemical reactions in the body, including anabolism and catabolism
  • Basal metabolic rate (BMR) the minimum amount of energy required to maintain life at rest
  • Thermic effect of food (TEF) the increase in energy expenditure associated with digesting, absorbing, and processing nutrients

Clinical Applications and Disorders

  • Metabolic disorders conditions that affect the body's ability to process and use nutrients (diabetes, phenylketonuria)
    • Diabetes a disorder characterized by high blood glucose levels due to insufficient insulin production or insulin resistance
    • Phenylketonuria an inherited disorder that affects the metabolism of the amino acid phenylalanine, leading to intellectual disability if untreated
  • Acid-base imbalances conditions in which the blood pH deviates from the normal range (acidosis, alkalosis)
    • Metabolic acidosis can be caused by diabetic ketoacidosis, lactic acidosis, or renal failure
    • Respiratory alkalosis can be caused by hyperventilation due to anxiety, pain, or high altitudes
  • Electrolyte imbalances conditions in which the levels of ions in the body are too high or too low (hyponatremia, hyperkalemia)
    • Hyponatremia low blood sodium levels, can be caused by excessive water intake, diuretic use, or hormonal disorders
    • Hyperkalemia high blood potassium levels, can be caused by renal failure, tissue damage, or certain medications
  • Nutritional deficiencies conditions that occur when the body lacks essential nutrients (iron-deficiency anemia, scurvy)
    • Iron-deficiency anemia occurs when the body lacks sufficient iron to produce hemoglobin, leading to fatigue and weakness
    • Scurvy a condition caused by vitamin C deficiency, characterized by weakened connective tissue and poor wound healing


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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.