PROTEIN

Structure of Protein

• Contains carbon, hydrogen, oxygen, nitrogen, and usually sulfur• iron, copper, phosphorus, or zinc

Structure of Protein

• Protein is made of chains of amino acids• “building blocks” of protein

• Created from 4 bonds around a carbon atom1. Carboxyl group (-COOH)

2. Amine group (-NH2)

3. Single hydrogen bond

4. Variable side group (letter “R”)• Makes one amino acid different from another

Structure of Protein• Watch the following:

https://www.youtube.com/watch?v=FKwSIu_XxnY

**will not need to know quaternary structure

Structure of Protein: Amino Acids

20 amino acids identified in the human body• 11 made by the body

• NONESSENTIAL or DISPENSABLE• Do not need to be a part of our diet

• 9 must be consumer from our foods• ESSENTIAL or INDISPENSABLE• Body cannot grow new tissue or maintain health without

these amino acids

Structure of Protein: Amino Acids

• Peptide bonds: bonds between two amino acids• Connects amine group of one amino acid to carboxyl group of another

• Water is the by product• Peptide bonds create:

• Dipeptide: 2 amino acids• Polypeptide: chain of multiple

amino acids bound together

Complete vs. Incomplete• Contains all indispensable

amino acids• Most from animal sources

• Eggs, milk, fish, poultry, meats

• Few plant products include:• Quinoa, amaranth, soybeans,

buckwheat, hempseed, chia

• Lacking 1 or more indispensable amino acid

• Found in grains and vegetables

• Important for vegetarians to combine 2 of the following within 24 hours to get the benefits of complete protein• Legumes• Grains• Nuts or seeds• Dairy

Grains Oats Rice Corn Cereal

Whole wheatBarley

MilkCheeseYogurt

Ice creamPudding

LegumesDried peas

Kidney beansGarbanzo beans

Peanuts

Seeds& Nuts

Pumpkin Sesame Sunflower Walnuts Poppy Pecan

Types of Vegetarians

• Pollo – does not eat red meat and fish (eats chicken)

• Pesco pollo – does not eat red meat (eats chicken & fish)

• Lacto – does not eat meat, fish, poultry, or eggs/foods containing eggs (eats dairy products like milk, cheese, & yogurt)

• Lacto ovo – does not eat meat, fish, and poultry (eats dairy product & eggs)

• Vegan – avoids eating all animal products

Protein Structures• Due to folding of chains of amino acids• Primary structure of proteins is the order the amino acids occur in the chain

• Secondary structure due to hydrogen bonding between amino acid side chains• Forms in 3 patterns:

1. Random coil (no specific

shape like a twisted Slinky)

2. Helix (coil like a Slinky)

3. Pleated sheet (paper fan)

Structure of Protein

• Tertiary Structure• Globular proteins- do not tend to form links that will

create a protein network• Ex: hemoglobin and lipoprotein

• Fibrous proteins- usually made from helix strands. Strong and part of connective tissue• Ex: collagen and elastin

Denaturation of a Protein• Watch the following:

https://www.youtube.com/watch?v=3IL_Df5ouUc

Denaturation of a Protein

• Denaturation: any change of the shape of the protein molecule without breaking its peptide bonds• Molecules unravel themselves and lose their coiled structure• Usually not reversible

Denaturation of a Protein

• Usually not reversible• Return to its original shape when:

• Denaturation is slight• Involve only hydrogen bond interactions

• Ex: lightly beating egg whites & gelatin

• Hold its shape when:• Protein interact with other proteins while unfolded• Breaking disulfide cross-links• Often during coagulation

Methods of Denaturation

1. Temperature• Heat is the most common agent• Rate of increase is 600 times for every 10°C rise in

temperature

2. Mechanical actions• Beating, rolling, and kneading

3. Chemical methods• Lowering pH

4. Other physical methods• Sound waves and irradiation

Coagulation of Proteins

• Results when a liquid protein forms clots• Occurs when a protein is heated

• Examples: curdling milk to form cheese or cooking an egg.

• When a protein is agitated• When chemicals, such as acids, are added to a protein

Coagulation of Proteins

• Milk proteins:• Casein: will not coagulate unless high concentrations of salt or acids are present

• Whey protein: coagulated by heat and responsible for film on bottom and sides of containers of heated milk

Coagulation of Proteins

• Over coagulation• Changes taste and texture of foods• Can ruin a recipe

• Overheated meat becomes tough/dry• Over agitation of meringue causes clots to form• Overcooked or overworked cheese results in rubbery texture

Functions of Protein in Foods

1. Form gels

2. Texturize

3. Emulsify

4. Form foams

5. Develop gluten

1. Form Gels

• Protein gelatin made from collagen extracted from the bones and hides of animals

• Gelatin protein can be heated in water and then cooled

• Milk and sugar can be heated to make pudding/custard

2. Texturize

• Proteins can be texturized through denaturation• This process is used to make

• soybeans into meat substitutes• processed cheeses

3. Emulsify

• Stable mixture of a fat and water based liquid• Emulsifier: molecule that has a polar end and a non

polar end• require heat or mechanical action to denature and form

the emulsion• Egg yolks are an excellent emulsifier, as is milk and cheese

• Food products such as ice cream and mayonnaise require emulsifiers to stay together

4. Form Foams

• Foam is a gas suspended in a liquid or semi solid• Foams can be made by:

• using eggs or dairy • incorporating air• mechanical agitation• by a sudden release in pressure (aerosol can)

• Examples of foams are: meringues, marshmallows, whipped cream, and bread

5. Develop Gluten

• Gluten: elastic protein formed when wheat flour is combined with moisture and stirred/kneaded• It coagulates when baked and forms an airy texture, such as bread

Protein in the Body

1. Support growth and repair

2. Fight disease

3. Maintain fluid and mineral balance

4. Maintain pH balance

5. Control bodily functions

6. Provide energy

1. Growth and Repair• Provides nitrogen and amino acids for growth and repair

of the body• 10,000 proteins have been identified in a single cell• Used to make muscle fibers, connective tissue, cell walls,

and red & white blood cells• Hair cells and nails also have a lot of protein• Whenever the body is injured, under stress, or ill; the

need for protein increases• Most body cells are replaced within a seven year period• Cells lining the intestinal tract are replaced every 3 days• Blood cells are replaced every 3-4 months

2. Fight Disease• Antibodies are a type of protein made by the body when a

disease or toxin is present• The body reproduces more antibodies for the next time

that the same germ comes into the body• A key function of protein is to protect the body from germs

and disease• Builds cells necessary to help get rid of parasites,

bacteria, and viruses• Only complete protein will give you these benefits

3. Maintain Body Fluid & Mineral Balance

• Help control movement of water and minerals in/out of cells• Too much water in cells – they burst• Too little fluid – they will die

• Maintaining the right mineral balance is important for nerves, brain, and muscles to function normally

4. Maintaining pH Balance

• Proteins are very important to maintain your pH balance

• Foods high in protein form acid and when eaten they cause acid pH• Therefore, balanced protein intake is necessary to

maintain a proper pH level• Too much protein can cause blockages in blood

5. Control Bodily Functions

• Control hormones• Regulates glucose levels in the blood• Controls growth, regulated reproductive system, and

other critical body functions

• Control enzymes• Necessary for most chemical reactions that occur within

the body

6. Provide Energy

• Body doesn’t store extra protein or turn it into muscle

• When you consume extra protein, your body can change the amino acids into an energy source

• NH2 is turned into ammonia, the C=O becomes part of a compound known as ketones

• Both ammonia and ketones put a strain on the kidneys