Chemistry and Biology Fundamentals

Fundamentals of Chemistry, Biology, and A&P

• The body has levels of organization, starting with the chemical level (atoms and molecules) and building to the cellular, tissue, organ, organ system, and organism levels.
• Molecules form through covalent bonds (sharing electrons), ionic bonds (transferring electrons), or hydrogen bonds (weak attractions).
• Free radicals are unstable molecules formed during normal metabolism or from environmental factors and can damage cells.
• Antioxidants, like vitamins C and E, neutralize free radicals.
• Acids release hydrogen ions (H⁺) in a solution, while bases accept hydrogen ions or release hydroxide ions (OH⁻).
• The pH scale measures acidity from 0-14, with acids having pH7, and neutral solutions at pH=7.
• Buffering systems, such as bicarbonate, protein, and phosphate buffers, maintain stable pH levels in the body.
• The cell membrane, made of a phospholipid bilayer with proteins, regulates what enters and exits the cell.
• Passive transport includes simple diffusion, facilitated diffusion, and osmosis.
• Active transport requires ATP and includes primary active transport (like the Na⁺/K⁺ pump) and secondary active transport.
• Endocytosis involves the cell engulfing material, while exocytosis involves the cell releasing material.
• Epithelial tissue covers surfaces, lines cavities, and forms glands.
• Connective tissue supports, binds, and protects various body parts, including bone, blood, and cartilage.
• Muscle tissue enables movement and is categorized as skeletal (voluntary, striated), cardiac (involuntary, striated), or smooth (involuntary, non-striated).
• Nervous tissue conducts electrical impulses in the brain, spinal cord, and nerves.

Digestion and Absorption

• Digestion breaks down food into nutrients, and absorption moves these nutrients into the blood or lymph.
• Mechanical digestion involves physical breakdown, while chemical digestion uses enzymes and acids.
• Nutrients are absorbed mainly in the small intestine.
• The mouth chews food, and saliva starts digesting carbohydrates and fats.
• The esophagus moves food to the stomach.
• The stomach mixes food and releases acid and enzymes to break down proteins and fats.
• The small intestine is the primary site of digestion and absorption, using enzymes from the pancreas and bile from the liver.
• The large intestine absorbs water and minerals and houses gut bacteria.
• The rectum and anus store and remove waste.
• The liver makes bile to digest fats, and the gallbladder stores and releases bile.
• The pancreas produces digestive enzymes and neutralizes stomach acid.

Carbohydrates

• Carbohydrates provide the body’s main fuel, especially for the brain and muscles.
• Extra glucose is stored as glycogen in the liver and muscles.
• Carbohydrates prevent the body from breaking down muscle for energy and support digestive health through fiber.
• Simple carbohydrates (sugars) are found in fruits, milk, and processed foods, including glucose, fructose, sucrose, and lactose.
• Complex carbohydrates (starches and fiber) are found in whole grains, vegetables, and legumes, providing longer-lasting energy.
• Whole grains contain all parts of the grain, offering more fiber and nutrients; refined grains have bran and germ removed; enriched grains have some vitamins and minerals added back.
• 45-65% of total daily calories should come from carbohydrates.
• Women should aim for 25g/day of fiber, and men should aim for 38g/day.
• Limit added sugars to less than 10% of daily calories.
• Digestion of carbohydrates begins in the mouth with salivary amylase.
• In the small intestine, pancreatic amylase breaks starch into simple sugars.
• Enzymes (maltase, sucrase, lactase) break sugars into glucose, which is then absorbed into the blood.
• The liver converts fructose and galactose into glucose for energy.
• Insulin (lowers blood sugar) is released by the pancreas when blood sugar is high, helping cells absorb glucose.
• Glucagon (raises blood sugar) is released by the pancreas when blood sugar is low, signaling the liver to release stored glucose.
• Epinephrine (adrenaline) increases blood sugar during stress or exercise.
• Cortisol and growth hormone help regulate blood sugar levels over time.

Lipids

• Fats provide a long-term energy source and cushions organs.
• Lipids helps maintain body temperature
• Phospholipids helps forms cell membranes and sterols help produces hormones
• Lipids also helps absorb fat-soluble vitamins (A, D, E, K).
• Saturated fatty acids are found in animal products and are solid at room temperature.
• Unsaturated fatty acids are found in plant oils and are liquid at room temperature.
• Trans fats are artificial fats in processed foods and are harmful to health.
• Triglycerides, made of 3 fatty acids + 1 glycerol molecule, are the main type of fat in food and the body.
• Phospholipids contain 2 fatty acids + a phosphate group and help transport fats in the blood.
• Sterols (cholesterol) are used to make hormones, vitamin D, and bile.
• 20-35% of daily calories should come from total fat, with less than 10% from saturated fat.
• Trans fats should be avoided.
• Omega-3 and Omega-6 fatty acids, found in fish, nuts, and seeds, are needed for brain and heart health.
• Bile emulsifies fats, and pancreatic lipase breaks triglycerides into fatty acids and glycerol in the small intestine.
• Fatty acids and monoglycerides enter intestinal cells and are repackaged into chylomicrons.
• Chylomicrons transport fats through the lymph and blood.
• Lipoproteins (LDL & HDL) move cholesterol and fats; LDL (bad cholesterol) delivers cholesterol to cells but can build up in arteries, while HDL (good cholesterol) removes excess cholesterol from the blood.

Protein

• Proteins are made of amino acids linked by peptide bonds with primary, secondary, tertiary, and quaternary structures.
• Proteins builds muscles, skin, and hair (collagen) and speed up chemical reactions as enzymes.
• They also regulates body functions (insulin) used as hormones and move substances in blood (hemoglobin carries oxygen).
• Proteins Supports immunity with antibodies and are used an energy source when carbs and fats are low.
• In transcription (nucleus), DNA makes messenger RNA (mRNA).
• During translation (ribosome), mRNA dictates the order of amino acids, and tRNA assembles them into a protein.
• The protein folds into its functional shape after translation.
• Generally, 10-35% of total daily calories should come from protein.
• Adults need 0.8 g/kg of body weight, while athletes need 1.2-2.0 g/kg.
• Complete proteins contain all essential amino acids and are found in meat, fish, eggs, dairy, soy, and quinoa.
• Incomplete proteins are missing some essential amino acids and are found in beans, nuts, and grains.
• Combining plant proteins (rice + beans) provides all essential amino acids.
• Choose lean protein sources (chicken, fish, beans) over high-fat sources.
• The hydrochloric acid (HCl) in the stomach denatures proteins, and pepsin begins breaking proteins into amino acids.
• Pancreatic enzymes (trypsin, chymotrypsin) in the small intestine break proteins into amino acids.
• Amino acids are absorbed into the blood and transported to cells.
• Amino acids are used to build new proteins, produce energy or converted to fat or glucose.
• Extra nitrogen is removed and excreted in urine.

Water + Alcohol

• Water is a universal solvent, has a high heat capacity, and acts as a lubricant.
• Water maintains body temperature, transports nutrients and waste, lubricates and cushions organs, aids digestion, and is involved in chemical reactions.
• Water balance is regulated by the thirst mechanism, hormones (ADH & Aldosterone), and electrolytes (sodium, potassium).
• Men need ~3.7 liters (125oz) per day, and women need ~2.7 liters (91 oz) per day, with more needed for exercise, heat, pregnancy, or illness.
• Ethanol is the type of alcohol found in beverages and is a depressant.
• Moderate drinking is up to 2 drinks/day for men and up to 1 drink/day for women.
• Binge drinking is 4+ drinks for women and 5+ for men in one sitting.
• Heavy drinking is more than 8 drinks/week for women and 15 for men.
• The stomach and small intestine absorb alcohol quickly into the bloodstream.
• Liver enzymes (alcohol dehydrogenase) break down alcohol at a rate of ~1 standard drink per hour.
• Excessive alcohol stays in the bloodstream, leading to intoxication.
• Short-term consequences of excessive alcohol use include impaired judgement, dehydration, and hangovers.
• Long-term consequences include liver damage, increased disease risk, brain effects (memory loss, dependence), and nutrient deficiencies.