Protein: The Primary Material of Life

Transcription

1 Protein: The Primary Material of Life -Composed of: carbon, hydrogen, oxygen, nitrogen -Two types of protein: Working & Structural Working Proteins: -Enzymes -Transport Vehicles -Cellular Pumps -Antibodies -Hormones -Oxygen Carriers Structural Proteins: -Tendons & Ligaments -Core of bone & teeth -Filaments of Hair -Nails, scars, and more -Structure of Protein: Nitrogen means amine-containing, thus amino acids, which are the building blocks of protein. All amino acids have the same backbone: Amine group (nitrogen) Carbon Acid group It s the side chain connected to the carbon that makes amino acids different. There are 20 different side chains, which make up 20 different proteins, thus, an infinite # of proteins are available -our bodies form 10-50,000 unique proteins! Essential AA s: We must eat these, 9 essential AA s Nonessential: Body makes 11 AA s itself Some proteins are (-), (+), or neutrally charged. Peptide bonds are formed between amino acids to form a protein 3% of our population are vegetarian: about 6-8 Million people; of which 3 million are Vegan.

2 Recycling amino acids: - Food proteins are dismantled after digestion to use amino acids - Body proteins, after their work is completed, is dismantled for reuse of amino acids. - The cells reuse AA s to build proteins it needs - No carbs? No fat? Body will break down its own protein for energy use, but it is very selective; uses blood proteins first, & saves the heart and other organs last. Gluconeogenises How do amino acids build proteins? - Amino acids link together by a peptide bond between amine group and acid group. - Not a straight chain; forms coils, ribbons-up into globule, as pos. & neg. charges attract or repel one another. From several doz. AA s to 300 AA s Variety of proteins is endless and perform different tasks - Most interesting: enzymes, which is a catalyst. Enzymes facilitate a chemical reaction without itself being altered. -Think of the alphabet: 26 letters make up words, protein have more possibilities than that. Inherited amino acid sequences - The sequence of amino acids that make up a protein molecule is specified by heredity. For each protein, there is only one proper AA sequence. If a wrong AA is inserted, the result could be disastrous, such as sickle cell anemia: valine replaces glutamine, and hemoglobin can no longer carry & release oxygen. -Each person is different, because of the minute differences in body proteins, which are determined by your genetic code you got from your parents.

3 Digestion & Absorption of Proteins: - Mouth crushes and adds saliva to protein in mouth - When protein hits the stomach, it must be denatured in order to be used by the body. Denaturation distorts the protein shape & is brought on by heat, alcohol, acids in the stomach, bases, salts of heavy metals or other agents. Acids in the gut attacks peptide bonds to separate aa s, and breaks protein into: single aa s dipeptides tripeptides polypeptides (more than 10 aa s long) - Then aa s are absorbed thru the sm. intestine wall, & into blood stream - Cells can then take what they need for their specific type of work. Digestibility of Food Proteins: 1. Animal protein - over 90% 2. Legumes- 80% 3. Grains & plants % - as per PER: Protein Efficiency Ratio: egg white, ground beef, chicken products, fat-free milk & tuna fish - cooking with moist heat improves digestibility, dry heat impairs it - must be accompanied by vitamins & minerals to be used efficiently Protein Quality: -Complete proteins: carry all the essential aa s: fish, meat, poultry, egg, cheese, soy -Incomplete proteins: lacking or low in essential aa s: plant sources can be combined to produce complementary proteins, i.e. legumes & grains, do not need to be eaten together, just in a day s regular diet. How Much Protein Do I Need? -Determined by nitrogen-balance study, pg. 194 Your weight divided by 2.2 = X.8 = grams/day Approx. 30 grams = one ounce

4 Consuming Too Little Protein - PEM: protein-energy malnutrition, aka protein-calorie malnutrition 33,000 children die each day from starvation-malnutrition causes - Marasmus: calorie-deficiency disease, starvation, skin and bones - Kwashiorkor: protein loss, often called second baby syndrome, as 1st baby is weaned from breast milk as soon as the second baby comes along. Characterized by edema in belly and legs, fatty liver, and general wasting. Consuming Too Much Protein - Overconsumption of protein offers no benefits, and may cause risks such as: developing heart disease from over-consumption of fats, esp. sat. fats develop atherosclerosis from high cholesterol and sat. fats worsens kidney problems, or alter functioning of healthy kidneys cause weight gain may accelerate bone loss in adults (still under investigation)

5 Roles of protein in the body 1. Supports Growth & Maintenance: AA s build: proteins of new tissue, i.e.: embryo, growing child, new blood, scars, hair, nails, and replace worn out cells (cells arise, live, die). 2. Builds Enzymes, Hormones, and Other Compounds: Enzymes: act as chemical catalysts Hormones: act as messengers, made from glands 3. Builds Antibodies: Antibodies are protein guards; they recognize every protein in the body that belongs in their body and leaves it alone, but it is able to spot a foreigner, an antigen from bacteria, virus, toxins, and then makes more antibodies to inactivate antigens. 4. Maintain Acid-Base Balance: Blood proteins act as buffers, which keeps ph constant. Buffers pick up hydrogens (acid) & release them again when there are too few (base). 5. Provides Energy: When aa s are needed for energy, amine group (nitrogen) is stripped off & used elsewhere, or excreted as urea by the kidneys. The remains are: carbon, oxygen and hydrogen, which can then be converted to glucose for energy. This takes place only if fat and carbs are not present - NG! promotes wasting of valuable organs. 6. Maintain Fluid & Electrolyte Balance: Proteins attract water; they help to keep the balance of fluids in and out of cells. Edema: too much fluid outside of cell, aka swelling. 7. Blood Clotting

6 Amino Acids: Be able to recite all of these verbally after the test for ten extra points. Print this out and bring it with you. Essential: Histadine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Valine Nonessential: Alanine Arginine Asparagine Aspartic acid Cysteine Glutamic Acid Glutamine Glycine Proline Serine Tyrosine