Proteins

Protein

compounds composed of carbon, hydrogen, oxygen, and nitrogen atoms

Some also contain sulfur atoms

How do protein arrange themselves?

Arranged as strands of amino acids

Amino acids

The building blocks of proteins

What does amino mean?

Nitrogen containing

How many amino acids and side chains are there?

20

What makes amino acids essential?

The body can’t make them

How are non essential amino acids made?

The body can make them when it has nitrogen and backbone fragments

Why is protein quality important?

Protein quality is important because it we can’t synthesize it easily

Are amino acid sequences interchangeable?

No

Dipeptide

2 amino acids

Tripeptide

3 amino acids

Polypeptide

4+ amino acids

90% found in our body

What happens to amino acids once we break them down?

The amino acids join the amino acid pool to be used by the body later

True/false:

Protein are part of every cell

True

True/false:

~ 30% of our total body weight is protein?

False; ~20%

What are the many forms protein come in?

• enzymes

• Antibodies

• Hormones

• Transport vesicles

• Oxygen carries

• Tendons/ligaments

• Scars

• Cores of bones/teeth

  • Filaments of hair

Function of Body Proteins

1) Growth and Maintanence

2) Enzymes

3) Hormones

4) Antibodies

5) Fluid Balance

6) Acid-Base Balance

7) Transport Proteins

😎 Energy Source

Function of Body Proteins: Growth and Maintenance

new body tissues are made of proteins—during growth, loss of tissue (burns, wounds), hair and nails, skin, etc.

Function of Body Proteins: Enzymes

1.ALL enzymes are proteins!

•Work as catalysts to help chemical reactions take place - “biological spark plugs”

•Surface of the enzyme is contoured so that it can only recognize the substance it works on

Functions of Body Proteins: Hormones

Similar to enzymes, but not all are made from protein

Do not catalyze reactions directly – instead act as messengers that respond to maintain a normal body environment (ex. blood glucose)

Functions of Body Proteins: Antibodies

large proteins that are produced by one type of immune cell in response to invasion of the body by unfamiliar molecules (antigens)

Can develop an immunity to that antigen

Functions of Body Proteins: Fluid Balance

To remain alive, a cell must contain a constant amount of fluid; proteins attract water

•Too much fluid may

cause the cell to rupture

•Too little fluid would make

it unable to function

Functions of Body Proteins: Acid-base Balance

proteins act as buffers to maintain the blood’s normal pH

•Pick up H ions when too much acid in the blood

Release H ions when pH is too high

Functions of Body Proteins: Transport Proteins

moves nutrients and other molecules in and out of cells (ex. sodium-potassium pump)

Functions of Body Proteins: Energy Source

•Used when insufficient CHO and fat

•Sufficient fat and CHO = “protein-sparing”

•AA are degraded for energy: amine group turns into urea (principle N waste product, made in liver, excreted by kidneys)

•Remaining C,H,O are available for energy

•Energy deficiency (starvation) always accompanied by protein deficiency

•Excess AA → glucose/glycogen or fat

AA shortage → breaks down body tissues

Denaturation

Change in shape of protein brought on by heat, alcohol, acids, bases, salts, or other agents

1st step in protein breakdown

Protein digestion/metabolism: Mouth

In the mouth, chewing crushes and softens protein rich foods and mixes them with saliva

Protein metabolism/digestion: stomach

Stomach acid denatures the protein stands. The enzyme pepsin breaks the protein strands down. A mucous lining on the stomach walls protects the stomach’s own proteins from both harsh stomach and and protein digesting enzymes

Protein metabolism/digestion: small intestine

Fragments of proteins are split into free amino acids with the help of proteases from the enzyme and pancreas.

Protein metabolism/digestion: large intestine

Carries any undigested protein residue our of the body

What are pepsin, proteases, and peptides?

• pepsin- enzyme in the stomach

• Proteases- enzymes from pancreas and small intestine

  • Peptidases- enzymes on surface of small intestine

What are the 3 important characteristics of dietary protein?

1.Should supply at least the 9 essential AA

2.Should supply enough other AA to make the N available for the synthesis of nonessential AA the cell may need

3.Should be accompanied by enough food energy (from CHO and fat) to prevent sacrifice of its own AA for energy

Complete proteins

Contain all essential AA in the right proportion relative to need (animal and soy protein)

Incomplete proteins

Lack or low in 1 or more essential AA

Limiting AA

Essential AA in shortest supply; limits the body’s ability to make proteins

Complimentary proteins

2 or more foods proteins whose AA assortments provide all of the essential AA

Biological value

assessed by determining how well a given food or mixture supports nitrogen retention

Reference protein

•egg white protein, the standard for which other proteins are compared to determine protein quality

What is the DRI for protein intake

10-35% total calories

RDA for protein intake

•0.8g/kg of desirable body wt per day

Uses desirable vs. actual because it is proportional to lean body mass

Calculate the RDA protein intake for someone who is 150 lbs?

Why doe people choose vegetarian diets?

For religious, ethical, or health reasons

Goals for people on vegetarian diets

•Obtain neither too few nor too many calories

•Obtain adequate quantities of protein

Obtain the needed vitamins and minerals

Vegetarian protein foods are higher in ____ , richer in certain vitamins and minerals, and lower in ____ compared to meats

Fiber, fats

If a vegetarian diet is followed properly, it may lead to lower rates of…

heart disease, cancer, diabetes, and obesity

More likely to be at desirable ____ , have lower _____ levels, and lower blood _____

Weight, cholesterol, pressure