Nutrition and Biochemistry

Nutrition Overview

• Macronutrients, needed in large amounts, include lipids, carbohydrates, and proteins, and their caloric content can be measured using a calorimeter.
• Micronutrients, needed in small amounts, consist of vitamins and minerals.

Biochemistry Basics

• Organic matter contains carbon-hydrogen bonds and forms the foundation of life, including macronutrients.
• Inorganic matter lacks carbon-hydrogen bonds, but is still essential for life processes.
• Monomers are the building blocks of macromolecules, dimers consist of two monomers, and polymers are made of three or more monomers.

Carbohydrates

• Carbohydrates are composed of carbon, hydrogen, and oxygen in a 1:2:1 ratio.
• The body needs carbohydrates in monomer form (glucose).
• Carbohydrates function as an energy source.
• Carbohydrates are also known as saccharides, named according to the number of sugar monomers they contain.
• Monosaccharides consist of one sugar monomer and have a ring structure, providing fuel.
• The body can readily use glucose, but must convert fructose and galactose before use.
• Disaccharides are composed of two sugar monomers linked by glycosidic bonds.
• Maltose is glucose + glucose, sucrose is glucose + fructose, and lactose is glucose + galactose.
• Polysaccharides are made of many sugar monomers bonded with covalent and hydrogen bonds.
• Starch and cellulose are found in plants, while glycogen is found in animals.
• Starch is used for energy storage in plants and is easily digested, while cellulose provides structure in plants (fiber), is indigestible, but promotes gut health.
• Glycogen is used for energy storage in animals and is broken down when blood sugar is low.

Carbohydrate Tests

• Benedict's test detects reducing sugars, reacting to monosaccharides, maltose, and lactose, requires heat, and changes color (blue is negative; green, yellow, orange, and red indicate increasing sugar concentrations).
• The iodine test identifies starch, with a blue-black color indicating a positive result and reddish-brown a negative result.

Proteins

• Proteins build, maintain, and repair the body, forming enzymes, hormones, hemoglobin, pigments, and muscle fibers.
• Proteins consist of amino acids, of which there are 20 different types.
• Eight are essential (obtained from the diet), and 12 are non-essential (synthesized by the body).
• Two amino acids join to form a dipeptide with a peptide bond, and multiple amino acids form a polypeptide (protein).
• Proteins have four levels of structure: primary (amino acid sequence), secondary (folded or pleated), tertiary (3D shape based on R group bonds), and quaternary (two or more tertiary structures).

Protein Denaturation

• Proteins need a specific 3D shape to function (tertiary or quaternary structure).
• Denaturation involves the loss of a protein's 3D shape, affecting R groups and reverting to primary and secondary structures.
• Denaturation can be caused by heat, pH changes, heavy metals, radiation, or mechanical force.
• Coagulation is a permanent change where liquid protein turns solid.

Protein Test

• The Biuret test detects peptide bonds, with a positive result indicated by a pink or purple color and a negative result by a blue color.

Lipids

• Lipids are hydrophobic, including fats, oils, phospholipids, waxes, and steroids.
• Lipids contain many carbon-hydrogen bonds, so yield lots of energy when broken down.
• Lipids function in energy storage, membrane structure, protecting and insulating organs, transporting fat-soluble vitamins, and waterproofing.
• Simple lipids include triglycerides (fats and oils) and waxes, while complex lipids include phospholipids, and derived lipids include steroids.

Triglycerides

• Triglycerides are made of glycerol and three fatty acid tails.
• Saturated fats have lots of hydrogen atoms, are hard to mobilize, solid at room temperature, and raise LDL (“bad cholesterol”).
• Unsaturated fats are liquid at room temperature and lower LDL, including monounsaturated (missing one hydrogen) and polyunsaturated (missing multiple hydrogens) fats.

Cholesterol

• Cholesterol is made by the liver and obtained in the diet.
• Cholesterol maintains cell membrane fluidity and structure, makes steroid hormones, bile, and vitamin D.
• Cholesterol is carried in the bloodstream by HDL (good cholesterol that carries excess cholesterol to the liver) and LDL (bad cholesterol that builds up in artery walls).

Lipid Test

• Lipids leave translucent marks on paper bags.
• A positive test shows a clear ring, while a negative test shows nothing.

Enzymes

• Enzymes are proteins that act as catalysts, speeding up chemical reactions.
• Enzymes are highly specific to their substrates.
• Active sites on enzymes interact with substrates by providing a location for interaction, bringing substrates together, and enhancing reaction efficiency.
• The induced fit model describes how the active site changes shape slightly for a better fit with the substrate.
• Cofactors and coenzymes help enzymes function by donating or receiving electrons (coenzymes are organic, cofactors are inorganic).
• Enzyme efficiency is affected by temperature, pH, and enzyme concentration.
• Competitive inhibitors bind to the active site, while non-competitive inhibitors bind elsewhere and change the active site's shape.

Metabolic Pathways

• Series of chemical reactions within a cell.
• A substrate is changed so it can go to the next enzyme in the chain until the final product if formed
• In feedback inhibition, the final product acts as an inhibitor in the pathway.

Digestion

• Digestion breaks down food into simple monomers, absorbs nutrients into the blood, and transports them into cells.
• Digestion involves ingestion (eating), digestion (physical and chemical breakdown), absorption (nutrient uptake in the small intestine), and egestion (waste removal).
• The gastrointestinal tract contains glands and accessory glands (saliva, stomach lining, pancreas, small intestine lining in the GI tract; saliva, pancreas, gallbladder, liver are accessory).

Digestion: The Mouth

• Mechanical digestion occurs.
• The tongue positions food, mixes it with saliva, and moves the bolus to the back of the throat, also providing taste.
• Salivary glands (3 pairs) produce saliva with water, antibacterial agents, and salivary amylase (breaks down starch).
• Swallowing is voluntary until the bolus enters the pharynx, the epiglottis closes the trachea, and peristalsis moves food down.

Digestion: The Stomach

• The bolus goes down the esophagus and enters the stomach through the cardiac sphincter
• Protein breakdown begins.
• The stomach is a thick-walled muscle with a 1.5 L capacity.
• Sensory cells produce HCl (hydrochloric acid) via gastric glands.
• Pepsinogen converts to pepsin (active enzyme).
• Mucus protects stomach walls from HCl.
• Gastrin triggers gastric juice release upon contact with food.
• No macronutrients are absorbed—only small amounts of drugs and alcohol.
• Chyme exits through the pyloric sphincter to the small intestine.

Digestion: The Small Intestine

• Most digestion and absorption occurs.
• Fat digestion begins.
• The small intestine consists of the duodenum, jejunum, and ileum.
• The duodenum receives substances from the liver, gallbladder, and pancreas to digest chyme.
• Liver makes bile and stores it in the gallbladder.
• Bile emulsifies fats so they can be broken down.
• The bile duct merges with the pancreatic duct to deposit into the duodenum at the ampulla of Vater.
• Pancreas secretes 28 enzymes, including bicarbonate, to lower the chyme's pH, in response to secretin secretion by the duodenum, and also makes insulin.
• The pancreas makes enzymes that digest lipids.
• The ileum and jejunum absorb macronutrients via villi and microvilli to increase surface area.

Digestion: The Large Intestine

• The large intestine absorbs fluids, synthesizes vitamins using bacteria, forms stool, and eliminates waste.
• It consists of the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anus.
• The appendix is an exit of the SI, that gives healthy bacteria to the LI.

Circulatory System

• The circulatory system dissolves and transports nutrients to cells and transports waste to the lungs, liver, and kidneys for removal.
• The heart pumps blood throughout the body and is found in the thoracic cavity of cardiac muscle.
• Arteries carry blood from the heart, and veins carry blood to the heart.
• The pericardium is a bag that surrounds, lubricates, and protects the heart.

Heart Structure

• Atria are thin-walled filling chambers, while ventricles are thick-walled pumping chambers.
• The septum separates the left and right sides (left has higher pressure/oxygenated blood, right deoxygenated).
• The right side receives blood from the superior and inferior vena cava, blood enters the right ventricle through the tricuspid valve and then goes though the pulmonary valve to the pulmonary arteries to the lungs.
• Oxygenated blood from the lungs enters the left atrium via pulmonary veins
• Blood from the atrium goes through the bicuspid valve to the ventricle
• Blood then goes through the aortic valve which enters the aorta and then is sent to the whole body

Valves

• Atrioventricular valves prevent backflow into the atria, while semilunar valves ensure blood flows correctly into the arteries.
• The "lub" sound is the closing of AV valves, and the "dub" sound is the closing of semilunar valves.

Circulation Routes

• Systemic circulation sends blood to the body and back to the heart.
• Pulmonary circulation sends blood to the lungs and back to the heart.
• Coronary circulation supplies blood to the heart itself.

Arteries

• Thick-walled with muscle, high pressure and speed, low area.
• Constrict and dilate to move blood.
• Arterioles are smaller branches that open or close based on body needs.
• Atherosclerosis: Clotting buildup on the walls of the arteries.
• Completely blocked: Heart attack or stroke.

Veins

• Thin-walled with valves.
• Other muscles pump the blood back to the heart
• Low pressure, medium speed, but limited area.
• Venules branch off of capillary beds.

Capillaries

• Blood vessels connecting arterioles and venules, allowing one RBC at a time.
• Site of exchange.
• Moderate pressure, slow speeds, and large area.
• Only 1% are open due to not enough blood filling them all.
• Precapillary sphincters control blood flow.

Blood Pressure (BP)

• Force exerted on artery walls, measured in systolic over diastolic pressure (average 120/80).
• Pulse averages 70 bpm.

Factors Affecting BP

• Cardiac output (5L/min) depends on stroke volume (blood per pump) and heart rate (speed).
• Kidneys maintain normal blood volume.
• Hemorrhaging and dehydration decrease BP.
• Arterial resistance (vessel tightness) changes pressure based on vasoconstriction and vasodilation.

Regulatory Mechanisms

• Detect changes and take the body back to normal.
• Baroreceptors monitor BP in the carotid artery, aorta, and kidneys, sending signals to the medulla oblongata.
• Thermoregulation occurs in the skin and is controlled by the hypothalamus.
• Vasodilation & Sweating results in body cooling, vasoconstriction and shivering results in body warming.

Heart Rate (HR)

• HR is controlled by a pacemaker in the SA node, sending signals to the AV node (with a delay), then to the bundle of His, and finally to the Purkinje fibers to contract the ventricles.
• The medulla oblongata controls speed.
• The sympathetic nervous system (stress) and adrenaline speed up HR via vasoconstriction.
• The parasympathetic nervous system (relaxation) slows down HR via vasodilation.

Blood

• Blood composition includes 55% plasma (90-95% water, 5-10% solutes) and 45% cells and formed elements.
• All blood components are stem cells made in the bone marrow.

Erythrocytes (RBCs)

• Biconcave to increase surface area.
• Enucleated (no nucleus, therefore can't divide).
• Packed with hemoglobin containing iron to bind O2.
• Anemia is a low RBC count due to blood loss or nutritional deficiency.
• Sickle cell anemia involves incorrectly formed RBCs.

Leukocytes (WBCs) and Clotting

• Thrombin and calcium activate fibrinogen to form fibrin threads, which create clots.
• Once clotted the threads pull together, then fibrin dissolves.

Antigens and Antibodies

• RBCs have protein markers called antigens (A or B, or both, or neither).
• The body makes antibodies to attack foreign antigens, using self-antigen markers.
• There are four blood types (A, B, AB, O) and eight groups (+ or -).
• The Rhesus factor determines + or - blood type (presence = positive, absence = negative).
• Positive blood can receive both + and - blood, while negative blood can only receive negative blood.
• Agglutination occurs when an antibody finds and attacks its target antigen.

Immunity

• Pathogens cause diseases, recognized by the body via their protein coat.
• The body creates self-antigens and attacks foreign antigens.

First Line of Defense

• The first line of defense consists of physical (skin, mucus, wax, cilia, coughing, sneezing) barriers.
• The first line of defense consists of chemical (fatty acids skin, lysozymes in tears) barriers.

Second Line of Defense

• Macrophages eat pathogens and place markers on their antigens for helper T cells.
• White blood cells signal the hypothalamus to increase temperature to slow down bacteria.
• Inflammation.

Third Line of Defense

• Foreign antigens are recognized, and antibodies are made.
• B cells are modified in the spleen, and T cells are modified in the thymus.
• Helper T cells find foreign antigens on macrophages.
• Helper T cells signal B cells to make specific antibodies.
• Antibodies immobilize pathogens, which are then eaten by macrophages.

Antibodies

• Proteins made in response to antigens
• Y-shaped with a constant region (for macrophage attachment) and two antigen-specific binding regions.

Vaccines

• Injected with a weakened/killed virus to be easily eliminated and remembered quickly fought.

Immune System Disorders

• Allergies are when the body mistakes harmless cells of harmful invaders.
• AIDS (acquired immunodeficiency syndrome) destroys helper T cells.
• SCID (severe combined immunodeficiency) is a condition when the body can't produce T or B cells.