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

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