The Major Biomolecules (and how we Digest them)

There are 4 major Biomolecules: -Carbohydrates -Lipids (Fats) -Proteins -Nucleic Acids

Carbohydrates -Carbohydrates are the sugars produced by primary producers through photosynthesis and the fuel for Cellular Respiration. -Digestible carbohydrates include sugars and starches. -Fruits, Vegetables, and Milk Products, are natural sources of sugar -Grains have high concentrations of starches

Carbohydrates: Monosaccharides Carbohydrates are built by the 3 basic sugar monomers: (Note: All are C6H12O6) Glucose, Fructose, and Galactose

Carbohydrates: Disaccharides -2 monosaccharides combine to form Disaccharide molecules Glucose + Glucose = Maltose (Malts) Glucose + Fructose = Sucrose (Table Sugar) Glucose + Galactose = Lactose (Milk)

Carbohydrates: Digestion -Chemical Digestion of Carbohydrates occurs in 3 stages: -Mouth: Salivary Amylase -Small Intestine: Pancreatic Amylase -Villi and Microvilli: Membrane-Bound Enzymes

Carbohydrates: Absorption & Storage -After being absorbed into the bloodstream by the small intestine, sugars travel through the hepatic portal vein to the liver. -In the liver, sugars are recombined and stored as complex molecules called Glycogen -HOMEOSTASIS: The Pancreas controls the uptake and the release of blood sugars by the liver.

Proteins -All living cells have proteins (Plant and Animal) -Common Foods with High amounts of proteins are: Eggs, Nuts, Beans, Dairy Products, and Meats -The Many Roles of Proteins: Repair and Build Body Tissues, Hormone Regulation, Enzyme Activity, Immune System Support, Energy

Proteins: Structure -Proteins are large molecules made up of subunits called amino acids (Over 100 in nature) -There are 20 unique amino acids that the body uses, each with its own unique structure VIDEO 2min -In order to absorb protein from food, we must break them apart into their individual amino acids. -Our bodies cannot synthesize (make) 8 of the 20 amino acids, and must obtain them from food: These are called ESSENTIAL AMINO ACIDS

Proteins: Digestion -Chemical Digestion of Proteins occurs in 3 places: -Stomach: Glands release Pepsin enzyme -Small Intestine: Pancreas releases proteases -Villi and Microvilli: Membrane-bound enzymes

Proteins: Absorption -Amino acids are absorbed individually or in groups of 2-3 into the capillaries of the villi -They are taken to the liver through the hepatic portal vein

Lipids (Fats) -Lipids are Fats -They are found in many foods: Meats, Eggs, Dairy, Avocados, Nuts, Seeds, Main Component of Oils

Lipids: Roles in the Body -Provide a concentrated source of Energy -Regulate Body Temperature (insulate) -Protect Vital Organs -Help produce body cells -Transport Fat Soluble Vitamins -Used in the production of Hormones and Vitamins

Lipids: Molecular Structure -The most common type of lipid molecule is the triglyceride, composed of one Molecule of glycerol and 3 fatty acid chains -An important feature of lipid molecules is that the glycerol head is hydrophilic (water liking), and the fatty acid chains are hydrophobic (water fearing)

Lipids: Digestion -Lipids do not dissolve in water (water insoluble) -Bile salts are produced by the liver and secreted by the gall bladder to break up lipids into small droplets that can be absorbed into the bloodstream

Lipids: Digestion -The smaller droplets are called micelles -The pancreas secretes lipases that break down the lipid molecules into 2 fatty acid chains and a Monoglyceride -They then diffuse through the villi into the bloodstream

Lipids: Absorption -Because lipids are insoluble, they don’t diffuse like sugars and amino acids in the bloodstream, instead, they are put back together as triglycerides, mixed with cholesterol, fat-soluble vitamins, and wrapped in a layer of proteins to make a transport protein called a Chylomicron