Acids, Bases, Digestion, and Metabolism: Key Concepts in Anatomy & Physiology

Acids and Bases in Physiology

Definitions and Properties

Acids and bases are fundamental chemical substances that play crucial roles in physiological processes. Their behavior in solution affects pH, enzyme activity, and metabolic reactions.

• Acids: Substances that release hydrogen ions (H+) in solution, making them proton donors.

• Bases: Substances that release hydroxide ions (OH-) or accept hydrogen ions, making them proton acceptors.

Acids: Chemical Properties

• Release hydrogen ions (H+) in water.

• React with metals to produce hydrogen gas.

• Turn blue litmus paper red.

• Taste sour (e.g., vinegar, lemon juice).

• Can neutralize bases to form salt and water.

Bases: Chemical Properties

• Release hydroxide ions (OH-) in water.

• Feel slippery to the touch.

• Turn red litmus paper blue.

• Taste bitter (e.g., baking soda).

• Can neutralize acids to form salt and water.

pH Scale

The pH scale measures the concentration of hydrogen ions in a solution, indicating its acidity or alkalinity.

• Acids: pH less than 7

• Bases: pH greater than 7

• Strong acids: pH 1–3 (e.g., hydrochloric acid)

• Weak acids: pH 4–6 (e.g., acetic acid)

• Weak bases: pH 8–10 (e.g., ammonia)

• Strong bases: pH 11–14 (e.g., sodium hydroxide)

Example: pH Comparison

• Each unit decrease in pH represents a tenfold increase in hydrogen ion concentration.

• For example, a solution with pH 4 is 10 times more acidic than one with pH 5.

Homeostasis and Acid-Base Balance

Homeostasis

Homeostasis is the body's ability to maintain a stable internal environment despite external changes. Key variables include temperature, pH, hydration, and glucose levels.

• Example: Keeping blood pH between 7.35 and 7.45.

• Systems involved: Nervous, endocrine, respiratory, urinary, and cardiovascular systems.

Acid-Base Disorders

• Acidosis: Blood pH below 7.35.

• Alkalosis: Blood pH above 7.45.

• Causes include respiratory or metabolic dysfunctions.

Bicarbonate Buffer System

The bicarbonate buffer system helps maintain blood pH by balancing carbonic acid (H2CO3) and bicarbonate ion (HCO3-).

• When blood becomes acidic, carbonic acid dissociates into hydrogen and bicarbonate ions, helping regulate pH.

• In the lungs, CO2 is expelled, reducing acidity.

Formula to remember:

$H_2CO_3 \rightarrow H^+ + HCO_3^-$

Digestive System Overview

Main Organs and Functions

The digestive system breaks down food, absorbs nutrients, and eliminates waste.

• Oral Cavity (Mouth): Begins the breakdown of food through chewing and saliva.

• Pharynx and Esophagus: Transport food from the mouth to the stomach.

• Stomach: Continues mechanical and chemical digestion.

• Small Intestine: Completes digestion and absorbs nutrients into the blood.

• Large Intestine: Reabsorbs water and expels undigested food as feces.

• Rectum and Anus: Store and eliminate solid waste.

Accessory Organs

• Liver: Produces bile to break down fats.

• Pancreas: Delivers digestive enzymes to the small intestine and also has endocrine functions.

• Salivary Glands: Secrete saliva to aid in initial digestion.

• Gallbladder: Stores and releases bile from the liver.

Digestion: Mechanical vs. Chemical

Mechanical Digestion

Mechanical digestion involves the physical breakdown of food, such as chewing and mixing actions in the stomach and intestines.

• Chewing and mixing actions increase the surface area for enzyme action.

• Peristalsis: Rhythmic contractions of smooth muscle move food through the digestive tract.

Chemical Digestion

Chemical digestion uses enzymes and digestive fluids to break food into its molecular components.

• Begins in the mouth with saliva and continues in the stomach and small intestine.

• Accessory organs like the pancreas and liver contribute enzymes and bile.

Absorption and Secretion

• Absorption: Movement of digested nutrients into the blood for distribution to body cells.

• Secretion: Involves the release of digestive enzymes and fluids from organs such as the pancreas, liver, and salivary glands.

Lipid Digestion and Absorption

Location and Chemical Digestion

• Lipids are primarily broken down in the small intestine.

• Bile from the liver emulsifies fats, increasing their surface area for enzyme action.

• Pancreatic lipase breaks down lipids into fatty acids and monoglycerides.

Mechanical Digestion

• Physical breakdown of food by chewing and mixing actions.

Transport and Absorption

• Lipid breakdown products are absorbed passively through diffusion.

• Once absorbed, they are transported to the liver via blood and lymphatic fluids.

Liver's Role

• The liver processes lipids, using them for energy, synthesizing important molecules, or storing them for future energy needs.

Pancreatitis and Liver Disease

Pancreatitis

Pancreatitis is inflammation of the pancreas, linked to conditions like gallstones, heavy alcohol use, and high triglycerides.

• Health Conditions: Gallstones, high triglycerides, heavy alcohol use, genetic disorders, certain medications, and viral infections.

• Acute Pancreatitis: Sudden onset, reversible with treatment. Symptoms include severe abdominal pain, nausea, vomiting, fever, rapid heart rate.

• Chronic Pancreatitis: Long-term inflammation, leading to scarring (fibrosis) and reduced ability to produce digestive enzymes and hormones.

Liver Disease

• Non-alcoholic fatty liver disease (NAFLD): Accumulation of excess fat in liver cells not caused by alcohol.

• Non-alcoholic steatohepatitis (NASH): More severe form of NAFLD with inflammation and cell damage.

• Cirrhosis: Chronic liver damage leading to scarring and liver dysfunction. Can result from prolonged NASH or alcohol use.

Macromolecules in Food

Types and Functions

The three main macromolecules in food are carbohydrates, lipids, and proteins. These macromolecules play crucial roles in nutrition and metabolism.

• Carbohydrates: Provide energy and are used as a source of quick fuel. Broken down into glucose, which is then oxidized to produce ATP.

• Lipids: Serve as energy storage, insulation, and are important for building cell membranes and producing hormones.

• Proteins: Essential for growth, repair, and building tissues. Also play a role in metabolic processes and enzyme activity.

Metabolism and Mass Balance Model

Metabolism

Metabolism involves all chemical reactions in the body, including breaking down complex substances and building new ones. It is explained using a mass balance model, which considers the balance between substances entering and leaving the body.

• Catabolism: Breakdown of molecules to release energy.

• Anabolism: Synthesis of new molecules for growth and repair.

Table: Comparison of Acidic and Basic Properties

Property	Acids	Bases
Ion Released in Water	H+	OH-
Litmus Paper Effect	Turns blue paper red	Turns red paper blue
Taste	Sour	Bitter
pH Range	Less than 7	Greater than 7
Reaction with Metals	Produces hydrogen gas	No reaction
Neutralization	Forms salt and water with bases	Forms salt and water with acids

Additional info:

• Some context and explanations have been expanded for clarity and completeness.

• Scientific names and terms have been italicized where relevant.

• All equations are provided in LaTeX format as required.