PROTEIN LECTURE: - 1st substance discovered to be a nutrient we needed- long history - We used to measure food beneficially in protein amounts. STRUCTURE- Composed of amino acids (AA). Subunits/building blocks- 20 amino acids. 9 are essential. 11 are nonessential. - All composed of carbon, hydrogen, and oxygen (like lipids and CHO), but ALSO NITROGEN! And sulfur. o Nitrogen is distinguishing feature of AA. o To find protein content, analyze for nitrogen in a food. - Has different side chains on every AA. Gives different chemical properties, theside chain is where they get their names. - Amino acids are joined by peptide bond… called a peptide!- Peptide: short chain of AAo EX: insulin. 51 amino acids. - Protein: Long chain of AAo May be hundreds or thousands long. Big complex moleculeso Sequence of AA is unique to each different protein. Carried in DNA.o DNA’s Job: carries sequences for proteins! Genes specify proteins. o 60,000 proteins in human body- Very complex structures: o 1st part: AA sequence. Some attractions, some repulsions. Forces built in. Forces make it a complex structure (like a coil or phone chord). o 2nd part: coil that formedo 3rd part: coils coil! Coil’s twist themselves. EX: Pleated sheets.o Sequence of AA completely determines properties of protein.  Ability to work with other AA’s is the reactivity of it. DIGESTION AND ABSORPTION- Stomach acid (hydrochloric acid) denatures the protein. o Breaks down the coil and makes a long single strand. o The bonds are broken by protease that’s produced in the stomach. o Also proteases created by pancreas go into small intestine to really finish the job- broken into short peptides or amino acids. o Can’t absorb a whole protein- must be broken down. o That’s why we inject insulin- straight to blood stream, otherwise by mouth it’d be broken down and not used.FUNCTIONS- Ton’s of functions. Very versatile. o Blood clotting proteins. Blood transport proteins. Proteins bind to the things they’re in charge of. Protein delivers it safely so it doesn’t harm parts of the body they’re not supposed to.  EX: Lipoproteins. Don’t want them in the wrong place. They bind to a protein which keeps them in right spots- Muscles, connective tissues, ligaments, cell membranes (lipids with proteins embedded in them)- Maintain fluid balance. Attract and hold fluid well—through osmosis. o Force on fluid that makes water attracted to proteins. Osmotic pressure generated keep fluid in the bloodstream = good  o Starving people with bloated bellies- edema- fluid accumulation- Acid-Base balance. Proteins act as buffers. o Balances hydrogen and hydroxyl ions through absorption. - Enzymeso Very specific action. Facilitates reactions and is not used up in processo Can speed up or slow down reaction. - Hormoneso Insulin. System wide effect. - Neurotransmitters are amino acids. o Synapse is area that nerve impulse travels across. Does this through the neurotransmitters. Allows us more control over the nature of the nerve impulse. o Different protein amounts can increase or diminish responses. - Immune system: o Fights off antigens (foreign proteins). Antibodies (Which are proteins) fight off the antigens. o Protein deficiency depresses immune system gets sick!- Energyo Less than 10% of Energy.  Most comes from CHO’s or Fat (brain needs CHO’s)o Used if glycogen in the liver is used up. Out of glucose. Resort to gluconeogenesis. Synthesis of glucose from amino acids/muscle.  Can never make glucose out of fat.  CAN make glucose out of carbs and then protein.  Why meal skipping/ low carb slows metabolism.  “Carbohydrates spare protein”REQUIREMENTS: RDA: based on age, weight 0.8g per kilogram of body weight. 60kilograms then 0.8x60 grams per day.o Weigh more, more protein.  More active needs more protein. (Ignored for RDA).  For average body weights: o RDA for Males- 63 grams per day o RDA for Females- 44 grams per day - Protein needs are met after 1200 calories. Daily intake gives you all you need.PROTEIN SOURCES- Chronically excessive= bad. No benefit. - Excess protein can turn into fat. - Meat fish eggs dairyPROTEIN QUALTIY- Quality depends on how good it does with Essential Amino Acids (EAA)o “Indispensable” amino acids. o 9 of them. o You cannot make them. Can’t synthesize. Must eat. o (other 11 you can make with right materials). - A complete protein supplies all 9 - Biological Value (BV)- measures the nitrogen. - Limiting Amino Acid- when you run out of an amino acid needed in a sequence. Completely stops synthesis. 1 you run out of first. - Chemical Score- See amino acid amounts/composition. Compare against an egg (perfect protein with value of 100). o Milk- 93 Fish- 76 Beef 74 Soy Beans 73 Whole wheat 65o If you ate only milk, You’d use 93%, excrete 7%o Animal protein- high qualityo Plant protein- low quality. VEGETARIAN - Lactovegetarians- plants and dairy products. Good amounts of protein - Lacto-ovo-vegetarians- plants, milk, and eggs. Good amounts!- Vegans- Problems. Only plants. Only low quality proteins. - Animal Proteins- Meat, fish, poultry, eggs, diaryo High BV. High Fat. High Cholesterol. Low fiber/carbs. - Plant Proteins- Soy beans, grains, nuts, legumes (beans), veggies.o Lower BV. Lower in fat and cholesterol. High fiber/complex carbs.o Even though low protein, they’re great overall. Other benefits. - Protein complementarityo Practice of combining 2 incomplete proteins to improve supply of limiting amino acids! Each supplements the other. o Must pair them right, get high BV! Eaten over course of the day will complement each other. No need for precise planning and timing.  EX: grains and legumes. Rice and Beans. - You can get needs met by other things, but you have to eat the things you maynot be used to eating (legumes). - Pregnancy needs are higher, kid needs are higher with vegan diets (lower energy density with vegan diets). PROTEIN ENERGY MALNUTRITION (PEM)- Usually deficient in energy/calories/food. - Poverty or famine. - Two types: Both: increased infection, reduced work capacity, o Marasmus- Skin and Bones. o Kwarshiarkar- abdominal edema (accumulation of fluid). Force of fluid through osmosis. Osmotic pressure which brings fluid into blood. Protein deficient= can’t balance, and water leaks out of bloodstream into