nut chapter 6 lecture

8/13/2019 Nut Chapter 6 Lecture

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2010 Pearson Education, Inc.

Chapter 6: Proteins and

Amino Acids


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What Are Proteins?

Large molecules

Made up of chains of amino acids

Are found in every cell in the body

Are involved in most of the bodys functions and lifeprocesses

The sequence of amino acids is determined by DNA


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Structure of Proteins

Made up of chains of amino acids; classified by number of

amino acids in a chain Peptides: fewer than 50 amino acids

- Dipeptides: 2 amino acids

- Tripeptides: 3 amino acids

- Polypeptides: more than 10 amino acids

Proteins: more than 50 amino acids

- Typically 100 to 10,000 amino acids linked together

Chains are synthesizes based on specific bodily DNA Amino acids are composed of carbon, hydrogen, oxygen,

and nitrogen


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Structural Differences Between Carbohydrates,Lipids, and Proteins

Figure 6.1


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The Anatomy of an Amino Acid

Figure 6.2b


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Peptide Bonds Link Amino Acids

Form when the acid group (COOH) of one amino acid joins

with the amine group (NH2) of a second amino acid Formed through condensation

Broken through hydrolysis


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Condensation and Hydrolytic Reactions

Figure 6.3


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10/53 2010 Pearson Education, Inc.

Structure of the Protein

Four levels of structure

Primary structure Secondary structure

Tertiary structure

Quaternary structure

Any alteration in the structure or sequencing changes

the shape and function of the protein



Denaturing

Alteration of the proteins shape and thus functions

through the use of Heat

Acids

Bases

Salts

Mechanical agitation

Primary structure is unchanged by denaturing


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Denaturing a Protein

Figure 6.5



Quick Review

Proteins are chains of combination of amino acids

Amino acids contain carbon, hydrogen, oxygen, nitrogen,and sometimes sulfur

Unique amino acids consist of a central carbon with acarboxyl group, a hydrogen, a nitrogen-containing amine

group, and a unique side chain There are 20 side chains and 20 unique amino acids

9 essential amino acids

11 nonessential amino acids- At time these become conditionally essential

Amino acids link together with peptide bonds bycondensation and break apart by hydrolysis


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Quick Review

Attractions and interactions between the side chains cause

the proteins to fold into precise three-dimensional shapes Protein shape determines its function

Proteins are denatured and their shapes changed by

Heat

Acids

Bases

Salts

Mechanical agitation


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Protein Digestion: Part 1

Figure 6.6


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Figure 6.6


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Figure 6.6


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Figure 6.6


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Amino Acid Absorption

Amino acids are absorbed in the small intestine

Amino acids are transported to the liver from the intestinesvia the portal vein

In the liver, amino acids are

Used to synthesize new proteins

Converted to energy, glucose, or fat

Released to the bloodstream and transported to cellsthroughout the body

Occasionally proteins are absorbed intact


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Amino Acid Metabolism

Liver metabolizes amino acids, depending on bodily needs

Most amino acids are sent into the blood to be picked upand used by the cells

Amino acid pool is limited but has many uses

Protein turnover the continual degradation and

synthesizing of protein


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Deamination

When the amino acid pool reaches capacity the amino acids

are broken down to their component parts for other uses First deamination must occur

Carbon-containing remnants are

Converted to glucose, if they are glucogenic amino acids,

through gluconeogensis

Converted to fatty acids and stored as triglycerides inadipose tissue

M b li F f A i A id


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Metabolic Fate of Amino Acids

Figure 6.7


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Quick Review

During digestion

Proteins are broken down to amino acids with the help of- Gastric juices

- Enzymes in the stomach and small intestine

- Enzymes from the pancreas and small intestine lining

Limited supply of amino acids exist in the amino acid pool The amino acid pool acts as a reservoir for protein

synthesis

Surplus amino acids are

Deaminated- Used for glucose or energy

- Stored as fat

- Nitrogen is converted to urea and excreted in urine


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How Does the Body Use Protein?

Functions of protein

Provide structural and mechanical support Maintain body tissues

Functions as enzymes and hormones

Help maintain acid base balance

Transport nutrients

Assist the immune system

Serve as a source of energy when necessary


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Quick Review

Protein plays many important roles in the body, including:

Helping facilitate muscular contraction Promoting satiety and appetite control


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How Much Protein Do You Need?

Healthy, nonpregnant adults

Should consume enough to replace what is used everyday

The goal is nitrogen balance

Pregnant woman, people recovering from surgery or injury,

and growing children

Should consume enough to build new tissue

Nit B l d I b l


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Nitrogen Balance and Imbalance

Figure 6.12


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Not All Protein Is Created Equal

High quality protein

Is digestible Contains all essential amino acids

Provides sufficient protein to synthesize nonessentialamino acids

It helps to be aware of:

Amino acid score

Limiting protein

Protein digestibility corrected amino acid score(PDCAAS)

Biological value of protein rates absorption and retentionof protein for use


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Protein Quality

Complete proteins

Contain all nine essential amino acids Usually animal source are complete proteins

Are considered higher quality

Incomplete proteins

Low in one or more essential amino acid

Usually plant sources are incomplete


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Protein Needs

Protein intake recommendations

1035% of total daily kilocalories Adults over 18

- 0.8 g/kg daily

American College of Sports Medicine, the AmericanDietetic Association, and other experts advocate

50100% more protein for competitive athletesparticipating in endurance exercise or resistance exercise

Typically this population eats more and therefore getsadditional protein


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Quick Review

Protein quality is determined by digestibility and types and

amounts of amino acids Animal protein is more easily digested and complete

Plant proteins are typically incomplete, except soy

Plant proteins can be complemented with proteins from

other plant sources or animal source to improve theirquality

Adults should consume 0.8 g/kg/d of protein

Men and women in the United States tend to over consume

protein


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Best Sources of Protein

Proteins are abundant in

Dairy foods Meats

Poultry

Meat alternatives such as dried beans, peanut butter,nuts, and soy

3 oz serving of cooked meat, poultry, or fish

Provides 2125 grams of protein

About 7 g/oz About the size of a deck of cards

Adequate amount for one meal



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Figure 6.14


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Quick Review

A well-balanced diet can meet daily protein needs

Best source of protein are animal products Eggs

Lean meats

Low-fat or fat-free dairy products

Plant proteins such as soy, grains, and vegetables supplysubstantial proteins

Most people consume adequate protein from their diet anddo not need protein supplements


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Protein Bars

Are marketed as convenient and portable

Can be High in saturated fat and/or sugar

Low in fiber

Expensive

A peanut butter sandwich is portable and lower in saturatedfat and sugar and higher in fiber than some protein bars


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Eating Too Much Protein

Risk of heart disease

Risk of kidney stones Risk of calcium loss from bones

Risk of colon cancer

Displacement of other nutrient-rich, disease preventingfoods


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Types of PEM: Kwashiorkor


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Types of PEM: Kwashiorkor

Severe protein deficiency

Generally result of a diet high in

grains and deficient in protein Symptoms range from

Edema in legs, feet, and stomach

Muscle tone and strength

diminish Hair is brittle and easy to pull out

Appear pale, sad, and apathetic

Prone to infection, rapid heartrate, excess fluid in lungs,

pneumonia, septicemia, andwater and electrolyte imbalances(Image from http://www.thachers.org/pediatrics.htm)

Figure 6.16

Types of PEM: Marasmus


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Types of PEM: Marasmus

Results from a severe deficiencyin kilocalories

Frail, emaciated appearance Weakened and appear apathetic

Many cannot stand withoutsupport

Look old

Hair is thin, dry, andlackssheen

Body temperature and blood

pressure are low

Prone to dehydration,infections, and unnecessary

blood clotting

Figure 6.17


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Treatment for PEM

Medical and nutritional treatment can dramatically reduce

mortality rate Should be carefully and slowly implemented

Step 1 Address life-threatening factors

- Severe dehydration

- Fluid and nutrient imbalances

Step 2 Restore depleted tissue

- Gradually provide nutritionally dense kilocalories andhigh-quality protein

Step 3 Transition to foods and introduce physicalactivity


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Vegetarian Diet

People choose vegetarian diets for a variety of reasons

Ethical Religious

Environmental

Health

Vegetarians must consume adequate amounts of a varietyof food and should plan meals well


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P i l B fi Ri k f V i Di


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- Cancer

- Stroke

- Obesity

Potential Benefits, Risks of a Vegetarian Diet

Benefits of a healthy vegetarian diet

Reduced risk of- Heart disease

- High blood pressure

- Diabetes

Potential risks of a vegetarian diet

Underconsumption of certain nutrients

- Protein- Vitamin B12

Vegetarian Food Guide Pyramid


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Vegetarian Food Guide Pyramid

Figure 6.18

S


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Soy

Soy is increasing in popularity in the United States

High-quality protein source Low in saturated fat

Contains isoflavones

Phytoestrogens

May reduce risk of heart disease

Some research suggests it may reduce the risk of cancer

Some concern it may promote breast cancer

Q i k R i


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Riboflavin

Vitamin B12

Vitamin A

Omega-3 fatty acids

Quick Review

Vegetarian diets can be a healthy eating style that may help

reduce the risk of some chronic disease Some vegetarians abstain from all animal products

Some vegetarians eat eggs and dairy in limited amounts

Vegetarians must plan their diets carefully to meet their

nutrient needs, especially Protein

Iron

Zinc

Calcium

Vitamin D

P tti It All T th


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Putting It All Together

Majority of daily kilocalories should come from

carbohydrate-rich foods Fat intake should be no more than about one-third of daily

kilocalories

Protein should provide the rest of the daily kilocalories

P tti It All T th


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Putting It All Together

Best plan for a healthful diet

Eat an abundance of- Grains (at least whole grains)

- Vegetables

- Fruits

Eat modest amounts of- Commercially made bakery and snack items

- Vegetables with creamy sauces or added butter

- Sweets

Choose low-fat dairy products, lean meat, poultry, andfish to minimize the intake of heart-unhealthy saturatedfats

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