Biology 2404 A&P Basics

The function of the GI tract is to breakdown nutrients into smaller, simpler molecules in the process of digestion for absorption into the blood or lymphatics in order to make these chemicals available to the body tissues. Most body cells convert the digested nutrients into the chemical energy compound ATP or use nutrients to replace and repair in the building of cells and tissues.

The major groups of nutrients fall into several categories.

Carbohydrates, Fats, Proteins, Nucleic Acids, Minerals, Vitamins, and Water.

Carbohydrates are the primary source of energy.

Three classes consist of the Monosaccharides, disaccharides, and poly saccharides.

Examples of each follows:

Monosaccharides: glucose, fructose, galactose, mannose, and xylose

Disaccharides: maltose (two glucose molecules)

Sucrose (glucose + fructose)

Lactose (glucose + galactose)

Polysaccharides: starch, glycogen, cellulose, inulin, xylans

Fats are composed of a large group of compounds based on fatty acids. The two major groups of importance in diets are cholesterol and triglycerides.

Cholesterol functions in cell membrane, steroid hormone structure, & bile salts

Triglycerides function in energy source & carriers of fat soluble vitamins

Two major groups of triglycerides are unsaturated and saturated fats.

This structure is based on carbon to carbon bonds in the fatty acid chains.

Single carbon to carbon bonds form saturated fats and are solids at room temperature.

Double carbon to carbon bonds form the unsaturated fats and are liquids at room temp.

Examples of saturated fats are butter and margarine.

Unsaturated fats are the oils such as sunflower, safflower, peanut, olive and

vegetable oils.

Form micelles during the digestive process to increase surface area for digestion.

Proteins are composed of combinations of the twenty amino acids. Some of these amino acids are essential, that is required in the diet, while others are nonessential, that is, not required in the diet because the liver can convert the essential amino acids to the other nonessential amino acids.

Proteins are in two major functional groups: linear/structural proteins and globular/active proteins. The amino acid chain folds to create a 3-D structure and each level of folding are a named structural level (primary, secondary, tertiary, and quaternary). If the configuration is disrupted, chemical bonds are broken and denaturing of the protein takes place. Causes for this denaturing can be mechanical, pH changes, temperature changes, and exposure to alcohol or detergents. Examples of the two major classes of proteins are:

Linear / Structural: collagen, keratin, microtubules, cytoskeleton

Globular / Active: enzymes, transport proteins, defense proteins, clotting proteins

Nucleic Acids are based on chains of nucleotides: 5-Carbon sugar, phosphate, and a nitrogen base. The two types of nucleic acids are DNA and RNA. These were discussed in earlier chapters so refer back regarding their location, structure, and function. The DNA of an individual’s cell is never used as a nutrient for energy production. RNA’s can be recycled and reused in energy pathways.

ENERGY DYNAMICS

All the chemical reactions that take place in the body are termed metabolism and are driven by enzymes and ATP energy. In catabolism, molecular bonds are broken in a decomposition reaction that releases stored energy. In anabolic reactions, substrates are formed or synthesized into larger molecules and energy is stored in these chemical bonds. The endothermic storage or exothermic release of energy in the form of ATP is inefficient and heat is released as one of the energy products. Heat generated is used to maintain optimal body temperature for the body’s chemical reactions and is distributed by the plasma of the blood to all body tissues. The body temperature level is set and regulated at specific areas in the hypothalamus. Any excess heat must be lost to the environment through the skin, respiratory, GI, and urinary tract. Most of the excess body heat is lost through the skin by blood flow changes in the upper dermal regions.

The four methods and definitions of heat loss are:

Radiation heat moves from higher temperature to cooler temperature

Evaporation sweating and the water is changed to from a liquid to a vapor

Convection air movement

Conduction transfer of heat when objects touch

If heat conservation is needed, heat loss can be minimized by changes in blood flow. Vasoconstriction moves blood away from the dermis and heat is retained in the body core.

Increases in body temperature are termed fever and abnormal increases in temperature are termed hyperthermia. Decreases in body temperature are called hypothermia.

Metabolic rate is the amount of heat production used to quantify the measure of metabolic activity. The minimal energy required for existing cell processes while sitting or lying quietly is called the basal metabolic rate. Metabolic rate will change with exercise, age, body surface area (configuration), hormones, types of food eaten, climate, and ANS-sympathetic activation.

Most foods are fuel for the body and rated according to the energy they supply when metabolized or burned. Energy is used for muscle activity, brain functions, maintenance of body temperature, running active transport movements of substances, repair and regeneration, ion pumps, cellular division, and almost every cell process and tissue/organ activity. The amount of energy released from foodstuffs is expressed in units called Calories or Kilocalories. A Calorie (Kilocalorie) is equal to 1000 calories. A calorie is the unit of heat needed to raise one gram of H2O one degree Celsius.

Thermodynamics is the study of energy and its transformation. As you discovered in the chemistry chapter, energy is defined as the capacity to do work or generate heat. Throughout the earlier chapters energy was shown and used in its various forms: heat, light, mechanical, electrical and chemical. Food energy was stored as chemical energy and when metabolized is converted to heat and mechanical energy. The heat generated helps maintain proper body temperature for enzymes to direct the chemical reactions of the body.

Enzymes

Enzymes enable reactions which normally occur slowly or not at all at body temperatures to take place at greatly increased speeds. Enzymes are named or classified according to the reaction they catalyze or after the substrate or reactants. Most enzymes end with the suffix –ase.

Examples of enzymes:

Hydrolases (hydrolysis, break down compounds using water)

Oxidases (oxidation, electrons are lost)

Ureases (substrate used is urea)

Nucleases (substrate used are nucleic acids, RNA)

Enzymes are globular proteins and contain the active site for the reactants. Many enzymes require co-enzymes such as Vitamins or metal cations to become fully functional. Because enzymes are proteins they can be denatured (chemical bonds forming the 3-D structure) by high temperatures and changes in pH.

During the chemical digestion processes, enzymes are needed to break down the larger molecules into smaller molecules. In the GI tract, the smaller molecules can then be absorbed into the blood and lymphatics. Major enzymes for the macromolecules are:

Amylase from the saliva and pancreas for CH20 digestion

Lipase from the saliva and pancreas for Fat digestion, once emulsified by bile from the liver and gall bladder.

Pepsin from the stomach, Proteases and Peptidases from the pancreas for protein digestion.

Other enzymes used in digestion are from the lining of the small intestine. This portion of the lining is called the brush border, so the enzymes are termed the brush border enzymes and function to complete chemical digestion of these nutrients.

Besides energy production, organic molecules can be used to make necessary materials for cells and tissues. The major organic macromolecules broken down for energy or substrate materials are:

Carbohydrates (CH2O) Simple Sugars such as Glucose, Fructose

Fats as Triglycerides Glycerol and Fatty Acids

Proteins as Peptides based on Amino Acids

Uses of Macromolecules

Glucose

1) ATP energy in glycolyis and aerobic respiration

2) Changed to a 5 carbon Pentose sugar for DNA, RNA

Fats

1) Adipose tissue for cushion, protection, Energy storage

2) Phospholipids for cell membrane, myelin

3) Cholesterol for steroid hormones, bile, cell membranes

4) Eiconosoids for local hormones

5) Energy processes

Glycerol in glycolysis

Fatty Acids as 2 carbon fragments to create new fats, Keto acids, Ketones

Amino Acids

1) New proteins:

keratin, melanin of the skin

collagen in the dermis, tendon, and ligaments

myosin, actin, myoglobin of muscle

hemoglobin for RBC

antibodies from WBC

clotting proteins such as prothrombin and fibrinogen

albumin for capillary dynamics

enzymes

hormones

2) Energy processes

Keto acids, Ketones

Ammonia that is converted to urea

Important metabolic reactions for energy production are:

Glycolysis

Aerobic Respiration

Deamination

Beta Oxidation

Glycolysis

Glycolysis is the breakdown of glucose into pyruvate. It is an anaerobic process that occurs in the cytoplasm of cells. Two ATP are required to start the process and four ATP are made for a net gain of 2 ATP molecules.

Cellular Respiration

Cellular respiration is the fourth phase of respiration and is divided into the Kreb’s Cycle and Oxidative Phosphorylation. Oxygen is required and the process occurs in the mitochondria. Pyrvate is converted to pyruvic acid. Pyruvic acid is then converted to a 2 carbon acetyl CoA that enters the first part of aerobic respiration. During the Kreb’s cycle, carbons are removed as CO2 and hydrogens are split to create H+ and an electron for the electron transport chain. In oxidative phosphorylation, the movement of the electron in the electron transport creates energy trapped in the ATP bonds and also releases heat. The Oxygen accepts the electron to become negative. The O2- and the H+ then combine to form water.

The complete reaction is written as:

C6H12O6 (Glucose) + O2 + CO2 + ATP + Heat + Water

Deamination

Deamination involves removing excess or old amino acids and using the byproducts in an energy pathway. The amine (NH2) group of the amino acid is removed. The remaining part of the amino acid becomes an intermediary in the glycolytic or Krebs cycle for energy production. The NH2 is converted to ammonia (NH3) in the liver and then to urea for elimination in the kidney.

Beta Oxidation

Beta oxidation involves breakdown of the fatty acids of the triglyceride into the 2 carbon acetyl group. A coenzyme is attached to help with transport and is identified as coenzyme A (CoA). Acetyl CoA can enter the Krebs Cycle for energy processes or be used to make other types of fats.

Other Important Nutrients

Water, also identified as H2O, functions as a solvent (dissolving solution), creates the basis of normal pH for the body, helps form the plasma of blood, and maintains a cohesive forces created by polar covalent bonds. These bonds enable water to maintain a high energy of boiling and a low point for freezing which means that it takes a lot of energy to get water to boil and in reverse, a lot of energy must be released before water freezes. Thus the three states of water are solid, liquid, and gas (vapor).

Vitamins

are organic molecules and many are used as coenzymes

Fat Soluble vitamins: A, D, E, K

Water soluble vitamins: B complex, C

Vitamin A used to make part of the photopigment of eyes

B complex most are involved with metabolic reactions

Vitamin C helps in formation of collagen, Iron absorption

Vitamin D needed for the absorption of Calcium and Phosphorus

Vitamin E antioxidant, needed for wound healing

Vitamin K used in formation of clotting factors

Minerals are inorganic molecules that form ions of salts and are classified as bulk or trace minerals depending on the amount required

Bulk Minerals Function or use

Sodium Na++ nerves and muscle excitability

Calcium Ca++ nerves excitability and muscle contraction

Potassium K+ nerves and muscle excitability

Chloride Cl- balance + charges

Sulphur S links antibody chain

Magnesium Mg++ nerves excitability and muscle contraction

Phosporus P bones, teeth, ATP, cell membrane

Trace Minerals

Iron Fe+++ hemoglobin, binds O2

Iodine I thyroid hormones

Manganese Mn coenzyme for fat synthesis

Copper Cu coenzyme for protein synthesis

Cobalt Co part of B12 vitamin

Zinc Zn skin and hair, wound healing

Flourine F part of tooth structure

Selenium Se antioxidant

Chromium Cr glucose metabolism, HDL to LDL

Medical Terminology

apo- from sacchar/o- sugar

peps/i- digest gluc/o, glyc/o- sugar

glycogen/o glycogen bil/i- bilirubin

flav- yellow stear, steat/o- fat

Exercises/Activities

I. Experiments

II. Diet Analysis (Diet Balancer program)

III. Blood work on glucose, albumin, cholesterol, FA, bile acids

Concept Map: Make a concept map of digestive metabolism using the secretion, source, location, end product, and use of metabolite. Include this concept map in your LAR lab report (if selected) as a document insert or as an additonal PDF scanned document.

Applications

Obesity Pancreatic Insufficiency

Keto acidosis HDL, LDL

Fever Hyperthermia, Heat Stroke, Heat Exhaustion

Hypothermia Anorexia Nervosa

Bulimia Steatorrhea

Dyspepsia Polyphagia

Careers:

Registered Dietician

Nutrionist

WWW

http://www.room42.com/nutrition/basal.shtml