jimtrue.com : school : HS1322 : CH05: Protein

Posted by Jim True on October 20, 2009 9:19 PM. Last Updated October 20, 2009 9:19 PM

Disclaimer for all material noted here is at the bottom of this web page.

CH05: Protein

An essential part of all living cells; found in animals and some plants. Amino acids are building blocks of protein; protein is a chain of amino acids connected by peptides.

• Essential part of all living cells found in animals and plants
• Protein is in your skin, hair, nails, muscles, etc.
• Made of amino acids - amino acids contain nitrogen, which is necessary for life
• Particularly rich in animal foods - meats, poultry, eggs, etc.

Part of a Protein

• Proteins often contain 35 to several hundred or more amino acids
• Amino Acid - Amino Acid - Amino Acid
• Peptide bonds: the bonds that form between adjoining amino acid

Essential & NonEssential Amino Acids

• 20 Amino Acids; Figure 5.2
• 9 Essential/11 nonessential
• Essential: acids that either cannot be made in the body or cannot be made in the quantities needed by the body
• Nonessential: these amino acids can be made IN the body
• One or more may become essential, conditionally essential

Proteins

• Protein fragments with 10 or more amino acids are called: Polypeptides
• Each of the over 50,000 different proteins in the body contains its own unique number and sequence of amino acids

Functions of Protein

• Acts as structural component of the body
• Builds and maintains the body tissues
• Found in many enzymes and hormones, and all antibodies
• Transports iron, fats, minerals and oxygen (taxicabs)
• Maintains fluid and acid-base balance
• Helps blood clot
• Provides energy as last resort

How Enzymes Work

• Enzymes contain a special pocket called the active site
• Fits into a specific substance
• The substance breaks down, but the enzyme stays the same

Nutrition Science Focus: Proteins

• Primary structure of protein: the number of sequence of the amino acids
• Secondary structure: the bending of the protein chains
• Tertiary structure: the folding and twisting of the protein chain that makes the protein able to perform it's function in the body

Nutrition Science Focus: DNA

• Deoxyribonucleic Acid
• 23 pairs of chromosomes

Digestion, Absorption & Metabolism

• Stomach
• Hydrochloric Acid denatures protein enough so enzymes can enter and do their work
• Hydrochloric Acid also activates pepsinogen to pepsin - an enzyme that splits peptide bonds
• Small Intestine
• Proteases split up proteins into short, peptide chains and amino acids
• Brush border of small intestine make sever peptidases - enzymes that bread down short peptide chains into amino acids, dipeptides, and tripeptides
• As dipeptides and tripeptides enter the intestinal cells, they are split into amino acids
• Amino acids travel in blood to liver and body cells
• Amino acid pool provides cells with a supply of amino acids

Protein in Food

• Animal foods: complete proteins, rich protein sources (beef, pork, poultry, fish, milk and eggs)
• Plant foods: incomplete proteins (beans, peas, nuts)

One ounce of meat, poultry or fish -

• 1 egg
• 1/4 cup cooked dry beans or tofu
• 1 tablespoon of peanut butter
• 1/2 ounce nuts or seeds
• Need 0.36g for each pound of weight

Complementary Proteins

• Beans is incomplete protein, rice cooked with it to give you a complete protein

Protein and Health

• Eating too much protein has no benefits and may result in:
  • Excessive kcalories
  • Excessive fat if you are eating too much high fat animal foods
  • Calcium loss
• High intakes of animal proteins are associated with certain cancers, such as cancer of the colon
• Eating too little protein can:
• slow down the protein rebuilding and repairing process
• Weaken the immune system
• Eating too little protein in many developing countries leads to PEM (Protein Energy Malnutrition) (Disorders in children: Kwashiorkor/Marasmus)

Dietary Recommendations for Protein

• RDA: 0.8 g/kg or 0.36 g/lb body weight
• Nitrogen balance
• Positive N Balance: body will excrete/secrete less protein than you take in (pregnancy and developmental stages of growth)
• Negative N Balance: body will excrete/secrete more protein than you take in (happen during starvation or during certain illness)
• AMDR (Acceptable Macronutrient Distribution Range) for Protein:
• Children from 1-3 years old: 5 to 20%
• Children from 4-18 years old: 10 to 30%
• Adults: 10 to 35%

Ingredient Focus: Meat, Poultry & Fish

• Most fish is lower in fat, saturated fat and cholesterol than are meat and poultry
• When choosing beef, you will get the least fat from eye of round, followed by top round and bottom round
• Meat is a good source of protein, iron, copper, zinc, and some of the B vitamins
• Chicken and turkey are rich in protein, niacin and Vitamin B6. Also good sources of riboflavin, vitamin B12, iron, zine, and magnesium
• Fish are excellent sources of protein, low in kcalories, and good sources of certain vitamins and minerals

Chicken and Turkey

• chicken is twice as fatty as turkey. The skin of chicken and turkey contains much of the bird's fat
• White meat chicken and turkey have less fat than dark meat
• Ground turkey or chicken have varying amounts of fat

# 1 cause of death in US is Cardiovascular Disease; #2 is Cancer

Steps to prepare Healthy Meat, Poultry & Fish

• Select a lean cut
• Use flavorful rubs and marinades
• Choose a cooking method that will provide a flavorful, moist product and that adds little or no fat to the food
• Think of how to flavor the dish (ie herbs and spices, smoking, etc.)
• Fish must be cooked very carefully and not overdone. Serve immediately

Culinary Science: Denaturation

• A process in which a protein uncoils and loses its shape
• Denaturation causes the protein to lose its ability to function

Food Facts: Soybeans

• Tofu, soy sauce, miso, tempeh, textured vegetable protein (tvp), meat analogs

Disclaimer: These are MY notes taken from classroom lectures while I'm in the classroom. While I'm perfectly happy to share my notes with my classmates and I know I take very good notes, you should still make every effort to attend the class and TAKE YOUR OWN NOTES. I will not transcribe everything the instructor says in the classroom, and I will NEVER post pre-exam reviews. My notes will not replace the value of actually attending class and taking your own class notes.I also cannot attest to their accuracy, other than they are what was provided in the lecture; you should not reference my notes as "expert opionion" by any means, and if you notice an error or omission, please do me the favor of e-mailing me with the correction and I will re-post my notes. End of Disclaimer.