Atoms, Ions and Chemical Bonds

Page 2: Water

• Water is the major constituent of the body, accounting for $65\%$ to $75\%$ of the total weight of an average adult.
• Of this water, two-thirds is intracellular (in the intracellular compartment).
• The remainder is extracellular, referring to blood and tissue fluids.
• Dissolved in this water are many:
  • Organic molecules: carbohydrates, lipids, proteins, nucleic acids.
  • Inorganic molecules and ions such as atoms.

Page 3: Atoms and Subatomic Particles

• ATOM: the smallest particle that characterizes a chemical element; cannot be cut into smaller particles.
• Modern atoms consist of subatomic particles:
  • Electrons: negative charge; extremely small, size currently unmeasurable.
  • Protons: positive charge; about $1836$ times more massive than electrons.
  • Neutrons: no charge; similar size to protons.
• Protons and neutrons form a dense, massive atomic nucleus (nucleons).
• Electrons form a much larger electron cloud surrounding the nucleus.

Page 4: Atomic Mass and Atomic Number

• Atomic mass: the sum of the protons and neutrons in an atom (often referred to as the mass number).
• Atomic number: the number of protons in an atom.
• Example: Carbon has six protons; atomic number = $6$.

Page 5: Isotopes

• Isotopes have nuclei with the same number of protons (same atomic number) but different numbers of neutrons.
• Therefore, isotopes have different mass numbers, which reflect the total number of nucleons (protons + neutrons).

Page 6: Chemical Bonding

• Chemical compounds are formed by the joining of two or more atoms.
• Covalent bond: one or more pairs of electrons are shared by two atoms.
• Ionic bond: one or more electrons are transferred from one atom to another, creating positive and negative ions that attract each other.
• Other types of bonds include hydrogen bonding.

Page 7: Acids

• Acids are ionic compounds that break apart in water to form hydrogen ions $H^+$.
• Strength of an acid is based on the concentration of $H^+$ in solution; more $H^+$ = stronger acid.
• Examples: $\text{HCl}$ (hydrochloric acid) in water.
• Characteristics of acids:
  • Taste sour.
  • React strongly with metals (e.g., Zn + HCl).
  • Strong acids are dangerous and can burn skin.
• Examples of acids: 1) Vinegar 2) Stomach acid (HCl) 3) Citrus fruits.

Page 8: Bases and Neutralization

• Bases are ionic compounds that dissociate to form hydroxide ions $OH^-$ in water.
• Strength of a base is determined by the concentration of $OH^-$; greater concentration = stronger base.
• Example: Sodium hydroxide in water $\text{NaOH}$ (a strong base).
• Solutions containing bases are often called alkaline.
• Characteristics of bases:
  • Taste bitter.
  • Feel slippery.
  • Strong bases are dangerous and can burn skin.
• Examples: 1) Sodium hydroxide 2) Ammonia
• Neutralization reactions: acids and bases react to form salt and water when hydrogen and hydroxide ions are present in equal amounts.
  • Example: $\mathrm{HCl + NaOH \rightarrow NaCl + H_2O}$

Page 9: pH Scale, Buffers, and Blood pH

• pH scale measures the strength of acids/bases via hydrogen ion concentration; ranges from $0$ (strongest acid) to $14$ (strongest base); $7$ is neutral.
• Buffers stabilize pH by resisting changes in $[H^+]$.
• Buffer system in blood plasma: reversible reaction involving bicarbonate $\text{HCO}<em>3^-$ and carbonic acid $\text{H}</em>2\text{CO}_3$.
  • Reaction (simplified): $\text{HCO}<em>3^- + H^+ \rightleftarrows H</em>2CO_3$
• Blood pH: arterial pH normally remains remarkably constant at $pH = 7.40 \pm 0.05$.
• Lactic acid and other organic acids are produced by cells and secreted into blood.

Page 10: Carbohydrates and Energy

• Carbohydrates are the body’s major energy source.
• Composition: carbon (C), hydrogen (H), and oxygen (O).
• Energy yield: approximately $4\ \text{kcal/g}$ of carbohydrates.
• Carbohydrates come in various sizes:
  • Monosaccharides (simple sugars).
  • Disaccharides (two sugar molecules).
  • Sucrose is a common disaccharide (table sugar).
  • Other examples: glucose and fructose (monosaccharides); lactose (milk); maltose (in beer).
  • Larger carbohydrates: polysaccharides (many sugar molecules).

Page 11: Carbohydrate Metabolism Disorders

• Carbohydrates provide sugars such as glucose, sucrose, fructose for energy.
• Some sugars require enzymatic breakdown before use.
• If needed enzymes are absent (often due to inherited disorders), sugars may accumulate and cause problems.

Page 12: Galactosemia

• Galactosemia is an inherited autosomal recessive trait.
• Due to lack of the enzyme galactose-1-phosphate uridyl transferase.
• Galactose can be found freely in food or produced from lactose breakdown.
• Body uses glucose for energy; in galactosemia, galactose accumulates and becomes toxic, leading to abnormal chemicals.

Page 13: Clinical Signs, Symptoms, and Treatment

• Symptoms arise from galactose and other toxic compounds: swollen/inflamed liver, kidney failure, ovarian failure in girls, impaired mental growth, cataracts.
• Treatment: restrict galactose and lactose from the diet for life.

Page 14: Protein Roles I – Binding, Transport, and Storage; Molecular Switching; Coordinated Motion

• Binding, transport, and storage:
  • Small molecules are often carried by proteins; example: hemoglobin transports oxygen to tissues.
  • Many drugs are bound to serum albumins in plasma.
• Molecular switching:
  • Conformational changes in response to pH or ligand binding control cellular processes.
• Coordinated motion:
  • Muscle contraction is mediated by sliding motion of two protein filaments, actin and myosin.

Page 15: Protein Roles II and Marasmus

• Structural support: collagen strengthens skin and bone.
• Immune protection: antibodies are protein structures that react with foreign substances.
• Generation and transmission of nerve impulses:
  • Some amino acids act as neurotransmitters.
  • Receptors for neurotransmitters and drugs are proteins (example: acetylcholine receptor in postsynaptic neurons).
• Control of growth and differentiation:
  • Proteins regulate growth, differentiation, and DNA expression (e.g., insulin, thyroid-stimulating hormone).
• Nutritional note: marasmus can occur if protein and caloric intake are both inadequate.

Page 16: Marasmus (Clinical Syndrome)

• Marasmus: severe protein-energy malnutrition characterized by energy deficiency.
• Cachexia: a related wasting syndrome.
• Clinical signs:
  • Dry skin, loose skin folds in areas like gluteal and axillary regions.
  • Drastic loss of adipose tissue from typical fat stores (buttocks, thighs).
  • Irritable, fretful, and extremely hungry.
  • Hair may show alternating pigmented/depigmented bands (flag sign) or flaky skin.

Page 17: Metabolic Disturbances and Treatment in Malnutrition

• Metabolic disturbances include little or no water retention.
• Potassium and sodium depletion may occur with persistent diarrhea.
• Serum protein levels are diminished.
• As wasting progresses, liver amino acid pool depletes; liver suffers acute depletion.
• Treatment: correct electrolyte imbalance, followed by a gradual feeding program (similar approach to kwashiorkor).

Page 18: Lipids – Structure and Storage

• Lipids (fats and oils): high-energy molecules composed mainly of carbon, hydrogen, and oxygen.
• Lipids are insoluble in water but soluble in certain organic solvents due to fewer oxygen atoms.
• Basic structure: glycerol backbone with three fatty-acid chains; forms triglycerides (triacylglycerols).
• Triglycerides are the major form of energy storage.
• Lipids are categorized as saturated or unsaturated based on fatty-acid structure.
• Lipids can be broken down into fatty acids for energy.

Page 19: Saturated vs Unsaturated Fatty Acids

• Key difference: saturated fatty acids are a major factor in raising blood cholesterol levels.
  • Elevated cholesterol can contribute to atherosclerosis and heart disease.
• Not all fatty acids are harmful; some unsaturated fatty acids are essential nutrients.
• Essential fatty acids cannot be synthesized by the body and must be obtained from the diet.
• Functions of essential fatty acids include regulation of blood pressure and roles in the synthesis/repair of cell parts.

Page 20: Lipid Disorders

• Lipid disorder refers to high blood cholesterol and triglycerides.
• Associated with increased risk of atherosclerosis and heart disease.

Page 21: Atherosclerosis

• Atherosclerosis: fatty material deposits along artery walls, forming plaque.
• Plaque thickens and hardens arteries, reducing elasticity and blood flow.
• If coronary arteries narrow, blood flow to the heart may slow or stop, causing chest pain (stable angina), shortness of breath, heart attack, and other symptoms.
• Plaque pieces can break away and form clots, potentially causing stroke, heart attack, or pulmonary embolism.

Page 22: Ketone Bodies

• Ketone bodies are three water-soluble compounds produced when fatty acids are broken down for energy.
• They are used as an energy source in the heart and brain; particularly vital for the brain during fasting.
• The three ketone bodies are:
  • acetoacetate
  • beta-hydroxybutyrate
  • acetone (though beta-hydroxybutyrate is technically a carboxylic acid, not a ketone).

Page 23: Ketone Bodies in Heart and Brain; Ketosis and Ketoacidosis

• Ketone bodies can be used for energy in the heart and brain via reconversion to acetyl-CoA and entry into the Krebs cycle.
• The heart relies heavily on ketone bodies for energy; the brain uses ketone bodies when glucose is insufficient (e.g., during fasting).
• Ketogenesis is the production of ketone bodies and is normal in small amounts.
• Ketosis: accumulation of ketone bodies that is not yet dangerously acidic.
• Ketoacidosis: larger amounts of ketone bodies lower the body’s pH to dangerous levels.

Page 24: Ketone Bodies in Diabetes and Pathophysiology

• In some diabetes cases, insufficient insulin leads to poor glucose delivery to tissues.
• As a compensatory mechanism, the body breaks down muscle and fat, producing ketone bodies.
• Ketone bodies include beta-hydroxybutyric acid, acetoacetic acid, and acetone; released into bloodstream and excreted in urine (some via lungs).
• Without treatment, glucose and ketone levels may become dangerously high.
• Factors like stress and illness increase risk of glucose and ketone buildup.
• When glucose and ketone levels are high, conditions include:
  • Hyperglycemia: too much sugar in blood
  • Ketoacidosis: too many ketone bodies in blood
  • Ketonuria: ketone bodies in urine
• When ketone is excreted, sodium is excreted with it.

Page 25: Symptoms and Treatment of Ketone/Glucose Overload

• Symptoms of glucose and ketone-body overload:
  • Thirst and frequent urination
  • Dehydration
  • Nausea and vomiting
  • Heavy breathing
  • Dilation of pupils and confusion due to ketone-induced toxicity
  • Fruity breath (acetone) detectable from lungs
  • Progression to coma and death if untreated
• Treatment: insulin and intravenous fluids to restore normal blood sugar and resolve ketoacidosis and ketonuria.

Page 26: Phospholipids and Steroids

• Phospholipids: a class of lipids; major component of all biological membranes, alongside glycolipids, cholesterol, and proteins.
• Steroids: structurally distinct from triglycerides or phospholipids.
• Cholesterol is an important molecule because it serves as a precursor for steroid hormones produced by the gonads and adrenal cortex.

Page 27: Prostaglandins

• Prostaglandins are lipid compounds derived enzymatically from fatty acids; found in virtually all tissues and organs.
• Roles include:
  • Constriction or dilation of vascular smooth muscle cells
  • Sensitization of spinal neurons to pain
  • Constriction of smooth muscle
  • Regulation of inflammatory mediation
  • Regulation of calcium movement
  • Regulation of hormone regulation
  • Control of cell growth