Hlth Basic Human Nutrition - Unit 4 (Ch. 6)

Front 1

Chemical difference between protein & carbs/fat

Back 1

Chemically, proteins contain nitrogen (N) atoms in addition to the same atomsas carbohydrates and lipids—carbon (C), hydrogen (H), and oxygen (O).

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Chemical structure of amino acids (protein)

Back 2

All amino acids have the same basic structure; a central carbon (C) atom with a hydrogen atom (H), an amino group (NH2), and an acid group (COOH) attached to it. But carbon atoms must havefour bonds, so a fourth attachment is necessary. This fourth site distinguisheseach amino acid from the others. --> unique "side group"

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Unique side groups

Back 3

The side groups on the central carbon vary from one aminoacid to the next, making proteins more complex than either carbohydrates or lip-ids. A protein, is made up of about 20 different amino acids, each with a different sidegroup (a polysaccharide on the other hand may be several thousand units long,but each unit is a glucose molecule just like all the others)

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Nonessential Amino Acids

Back 4

More than half of the amino acids are nonessential,meaning that the body can synthesize them for itself (given nitrogen to form andfragments from carbohydrate or fat).

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1) proteins:

2) amino acids:

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1) compounds composed of carbon, hydrogen,oxygen, and nitrogen atoms, arranged into amino acids linkedin a chain.

2) amino acids: building blocks of proteins. Eachcontains an amino group, an acid group, a hydrogen atom, anda distinctive side group, all attached to a central carbon atom.

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Essential Amino Acids

Back 6

There are 9 amino acids that the human body eithercannot make at all or cannot make in sufficient quantity to meet its needs. Thesenine amino acids must be supplied by the diet.

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Conditionally Essential Amino Acids

Back 7

Sometimes a nonessential amino acid be-comes essential under special circumstances.

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peptide bond:

Back 8

a bond that connects the acid end of oneamino acid with the amino end of another, forming a link in aprotein chain.

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1) dipeptide:

2) tripeptide:

3) polypeptide:

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1) two amino acids bonded together.

2) three amino acids bonded together.

3) many (10 or more) amino acids bonded together.

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Primary Structure of proteins:

Back 10

The primary structure of a protein is determined by the sequence of amino acids.

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Secondary Structure of proteins —Polypeptide Shapes:

Back 11

The secondary structure of proteins is determined by weak electrical attractions within the polypeptide chain. As positively charged hydrogens attract nearby negatively charged oxygens, sections of the polypeptide chain twist into a helix or fold into a pleated sheet, for example. These shapes give proteins strength and rigidity.

Front 12

Tertiary Structure of proteins—Polypeptide Tangles

Back 12

The tertiary structure of proteins oc-curs as long polypeptide chains twist and fold into a variety of complex, tangledshapes. Some side groups are attracted to water molecules; they are hydrophilic. Otherside groups are repelled by water; they are hydrophobic.

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Quaternary Structure of proteins —Multiple Polypeptide Interactions

Back 13

The quaternary structure of proteinsinvolves the interactions between two or more polypeptides. One molecule ofhemoglobin is made of four associated polypeptidechains, each holding the mineral iron

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hemoglobin:

Back 14

the globular protein of thered blood cells that carries oxygen from the lungs to the cellsthroughout the body.

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denaturation:

Back 15

the change in aprotein’s shape and consequent loss of its function broughtabout by heat, agitation, acid, base, alcohol, heavy metals, orother agents. In the body, proteins are denatured when they are exposed to stom-ach acid.

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the 3 protein structures

Back 16

The shape of each polypeptide chain is determined by anamino acid sequence (primary structure) that twists into ahelix (secondary structure) and bends itself into a ballshape (tertiary structure).

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Protein Digestion: In the Stomach

Back 17

Major event in stomach = the partial breakdown(hydrolysis) of proteins. Hydrochloric acid uncoils (denatures) each protein’stangled strands so that digestive enzymes can attack the peptide bonds. It also converts the inactive form of the enzyme pepsinogen to itsactive form, pepsin. Pepsin cleaves proteins—large polypeptides—into smallerpolypeptides and some amino acids.

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Protein Digestion: In the Small Intestine

Back 18

When polypeptides enter the small intestine, several proteases hydrolyze them further into short peptide chains, tripeptides,dipeptides, and amino acids. Then peptidase enzymes from the intestinal cells split most of the dipeptides and tripeptides into single amino acids.Only a few peptides escape digestion and enter the blood intact

Front 19

Protein Absorption

Back 19

A number of specific carriers transport amino acids into the intestinal cells. Once inside the intestinalcells, amino acids may be used for energy or to synthesize needed compounds.

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When is the specific function of a protein determined?

Back 20

During protein synthesis

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Protein synthesis

Back 21

Depends on a diet that providesadequate protein and essential amino acids.

The instructions for making every protein in a person’s body are transmitted byway of the genetic information received at conception.

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Transforming the information in DNA into the appropriate sequence of amino acids needed to make a specific protein (protein synthesis)

Back 22

2 major steps.

1) transcription: a stretch of DNA is used asa template to make messenger RNA. Messenger RNA then carries the code into the body of the cell, where it attachesitself to one of the ribosomes (a protein-making machine).

2) translation: Situated on a ribosome, messenger RNA specifies the sequence in which theamino acids "line up" for the synthesis of a protein.

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Lining Up the Amino Acids (protein synthesis)

Back 23

Other forms of RNA, called transfer RNA, collectamino acids from the cell fluid and take them to messenger RNA. Each of the 20amino acids has a specific transfer RNA. When the messenger RNA calls for a specific amino acid, the transfer RNA carrying that amino acid moves into position

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transcription:

Back 24

the process of messenger RNA being madefrom a template of DNA.

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translation:

Back 25

the process of messenger RNA directing thesequence of amino acids and synthesis of proteins.

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sickle-cell anemia:

Back 26

A hereditary form of anemiacharacterized by abnormal sickle- or crescent-shaped redblood cells. Sickled cells interfere with oxygen transportand blood flow. Symptoms are precipitated by dehydrationand insufficient oxygen (as may occur at high altitudes) andinclude hemolytic anemia (red blood cells burst), fever, andsevere pain in the joints and abdomen.

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Sequencing Errors

Back 27

The sequence of amino acids in each protein determinesits shape, which supports a specific function.

An error in the amino acid sequence results in an altered protein - sometimes with dramatic consequences.

Example: sickle-cell anemia caused abnormal protein hemoglobin

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Gene Expression

Back 28

When a cell makes a protein,scientists say that the gene for that protein has been “expressed.”

Cells can regulate gene expression to make the type of protein,in the amounts and at the rate, they need. Nearly all of the body’scells possess the genes for making all human proteins, but eachtype of cell makes only the proteins it needs.

= the process by which a cell converts thegenetic code into RNA and protein.

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Roles of Proteins

Back 29

Act as Structural Materials, As Enzymes, As Hormones (e.g. insulin), As Regulators of Fluid Balance, As Acid-Base Regulators, As Transporters, As Antibodies, As a Source of Energy and Glucose,

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Roles of Proteins - as Structural Materials

Back 30

Tobuild a bone or a tooth, cells first lay down a "matrix" ofthe protein "collagen" and then fill it with crystals of calcium, phosphorus, magnesium, fluoride, and other minerals. Proteins are also needed for replacing dead or damaged cells.

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matrix:

Back 31

the basic substance that gives form toa developing structure; in the body, the formative cells fromwhich teeth and bones grow.

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collagen

Back 32

the structural protein from whichconnective tissues such as scars, tendons, ligaments, and thefoundations of bones and teeth are made. It provides the material of ligaments and tendons and thestrengthening “glue” between the cells of the artery walls (that enables the arteries to withstand the pressure of the blood surging through them).

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Roles of Proteins - as Enzymes

Back 33

Enzymes not only break downsubstances, but they also build substances (like bone) and transform one substance into another(e.g. amino acids into glucose). Breakingdown reactions are catabolic, whereas building upreactions are anabolic.

Like the ministerand the judge, enzymes themselves are not altered by the reactions they facilitate.They are catalysts, permitting reactions to occur more quickly and efficiently.

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Roles of Proteins - As Regulators of Fluid Balance

Back 34

Proteins help to maintain thebody’s fluid balance. Normally, proteins are found primarilywithin the cells and in the plasma.

Being large, proteins do not normally cross the wallsof the blood vessels.

During times of critical illness or protein malnutrition, however, plasma proteins leak out of the blood vesselsinto the spaces between the cells.

Because proteins attract water,fluid accumulates and causes swelling. Swelling due to an excess offluid in the tissues is known as edema.

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fluid balance:

Back 35

maintenance of the proper types and amountsof fluid in each compartment of the body fluids

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Roles of Proteins - As Acid-Base Regulators

Back 36

Proteins also help to maintain the balance between acids and bases within the body fluids. The more hydrogen ions (H+), the more acidic the solution and the lower thepH.

By accepting and releasing hydrogen ions, proteinsact as buffers, maintaining the acid-base balance of the blood and body fluids.

Front 37

1) acids:

2) bases:

3) buffers:

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1) compounds that release hydrogen ions in a solution.

2) compounds that accept hydrogen ions in a solution.

3) compounds that keep a solution’s pH constant whenacids or bases are added.

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1) acidosis:

2) alkalosis:

Back 38

1) higher-than-normal acidity in theblood and body fluids.

2) higher-than-normal alkalinity (base)in the blood and body fluids.

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Roles of Proteins - As Transporters

Back 39

The protein hemoglobin carries oxygen from the lungs to the cells. The lipoproteins transport lipids around the body. Special transport proteins carry vitamins and minerals.

Some transport proteins reside in cell membranes and act as “pumps,” picking up compounds on one side of the membrane and releasing them on the otheras needed.

Each transport protein is specific for a certain compound or group ofrelated compounds.

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Roles of Proteins - As Antibodies

Back 40

Proteins also defend the body against disease. When the body detects invading antigens, it manufacturesantibodies, giant protein molecules designed to combat them. These work so swiftly and efficiently that in a healthy individual, most diseases never get started. Without sufficient protein, though, the body cannot maintain its army of antibodies to resist infectious diseases.

Each antibody is designed to destroy a specific antigen.

Once the body hasmanufactured antibodies against a particular antigen,it “remembers” how to make them. Consequently, the next time the body encounters that same antigen, it produces antibodies even more quickly: the body develops a molecular memory, known as immunity.

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immunity:

Back 41

the body’s ability to defend itself against diseases

Front 42

Roles of Proteins - As a Source of Energy and Glucose

Back 42

Proteins will be sacrificed to provide energy and glucose during times of starvation or insufficient carbohydrate intake (break down proteins to make amino acid to make glucose). This way, protein can maintainblood glucose levels, but at the expense of losing lean body tissue.

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protein turnover:

Back 43

The process of proteins being continually made and broken down within each cell

= the degradation and synthesis of protein

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Proteinbreakdown releases:

Back 44

amino acids.

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amino acid pool:

Back 45

the supply of amino acids derived from food proteins or body proteins that collect in the cellsand circulating blood and stand ready to be incorporated inproteins and other compounds or used for energy.

(The broken down amino acids mix with amino acids fromdietary protein to form an “amino acid pool”)

Front 46

nitrogen balance:

Back 46

the amount of nitrogen consumed (N in)as compared with the amount of nitrogen excreted (N out) in agiven period of time. goes hand in hand with protein turnover.

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Positive nitrogen status

Back 47

If the body synthesizes more than it degrades, protein is added. E.g. in growing infants, children,adolescents, pregnant women

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Negative Nitrogen status

Back 48

When nitrogen excretion exceeds their nitrogen intake

E.g. in people starving or suffering other severe stresses such as burns, injuries, infections, and fever;

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amino acid tyrosine

Back 49

used tomake the neurotransmitters norepinephrine and epinephrine as well as the pigment melanin, which is responsible for brown hair, eye, and skin color.

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Using Amino Acids to Make Fat

or how do protein-rich foods can contribute to weight gain?

Back 50

Amino acids may be converted to fat when energy and protein intakes exceed needs and carbohydrate intake is adequate.

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deamination

Back 51

When amino acids are broken down, they are first deaminated = stripped of their nitrogen-containing amino groups .

Two products result: ammonia (NH3); and a keto acid (or another carbon structure without its amino group)

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Keto acids

Back 52

= A carbon structure without its amino group.

Can enter a number of metabolic pathways.

May be used for energy orfor the production of glucose, ketones, cholesterol, or fat.

They may also be usedto make nonessential amino acids.

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Using Amino Acids to Make Proteins and Nonessential Amino Acids

Back 53

If anessential amino acid is missing, the body may break down some of its own proteins to obtain it.

Occurs through "transamination" reactions (like cells making an amino acid from a keto acid if nitrogen is available, or by transferring an amino group (from the amino acid) to its corresponding keto acid.

Front 54

Converting Ammonia to Urea

Back 54

Deamination produces ammonia, a toxic compound.

Because ammonia is a base, excessive quantities upset the blood’s critical acid-base balance.

To prevent this,the liver combines ammonia with carbon dioxide to make urea, a much lesstoxic compound.

Front 55

Excreting Urea

Back 55

Liver cells release urea into the blood, where it circulates until it passes through the kidneys. The kidneys then filter urea out of the blood for excretion in the urine.

This division of labor allows easy diagnosisof diseases of both organs. In liver disease, blood ammonia is high; in kidneydisease, blood urea is high.

Urea is the body’s principal vehicle for excreting unused nitrogen, and theamount of urea produced increases with protein intake. To keep urea in solution, the body needs water.

Front 56

high-quality proteins

Back 56

provide enough of all the essential amino acids needed tosupport the body’s work (while low-quality proteins don’t).

=dietary proteins containing all theessential amino acids in relatively the same amounts thathuman beings require. They may also contain nonessentialamino acids.

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limiting amino acid

Back 57

An essentialamino acid supplied in less than the amount needed to support protein synthesis.

Four amino acids are most likely to belimiting:

• Lysine

• Methionine

• Threonine

• Tryptophan

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reference protein

Back 58

Standard against which to measure thequality of other proteins.

The quality of a food protein is determined by comparing itsamino acid composition with the essential amino acid requirements of preschool-age children

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complementary proteins:

Back 59

two or more dietary proteinswhose amino acid assortments complement each other so that the essential amino acids missing from oneare supplied by the other.

E.g. Grains have the opposite strengthsand weaknesses than legumes, making them a perfect match.

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Consequences of proteindeficiency

Back 60

slowed growth, impaired brain and kidney functions, poorimmunity, and inadequate nutrient absorption.

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Heart Disease & protein

Back 61

Elevated levels of the amino acid homocysteine may bean independent risk factor for heart disease, heart attacks, and sudden death inpatients with heart disease. It is also associated with increased oxidative stress and inflamma-tion.

In contrast to homocysteine, the amino acid arginine may help protect againstheart disease by lowering blood pressure and homocysteine levels.

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Adult Bone Loss (Osteoporosis) & protein

Back 62

Bones need both protein and calcium.

When protein intake is high, calcium excretion increases.

The problem may reflect too little calcium, not too much protein.

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Kidney Disease & protein

Back 63

A high protein intakedoes not cause kidney disease, but it does increase the work of the kidneys.

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RDA for protein:

Back 64

0.8 g/kg/day • 10 to 35% of energy intake.

Gets raised during growth,so it increases for infants, children, adolescents, and pregnant and lactatingwomen.

It is recommended that 10-35% of total caloric intake be derived from protein. Hence, if a person eats 2000 kcal/day, 10% of total calories = 200 kcal. 200kcal from protein = 50 g of protein.

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The two reasons the body needs dietary protein

Back 65

First,dietary protein is the only source of the essential amino acids, and second, it is theonly practical source of nitrogen with which to build the nonessential amino acids

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protein/carbohydrate/fat intake as a percentage of energy

Back 66

Be careful when judging protein (or carbohydrate or fat) intake as a percentage of energy.

Always consider the number of grams as well, and compare itwith the RDA

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% Daily Value for protein

Back 67

Not mandatory on all labels but is required whenever a food makes a protein claim or is intended for childrenyounger than 4 years old.

When a % Daily Value isstated for protein, it reflects both quantity and quality.

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Forming a Protein

Back 68

Two amino acids can link up at the carboxyl (COOH) end of one and the amino (NH2) group of another.

In a condensation reaction, a hydrogen is removed from one amino acid, and a hydroxyl group is removed from the other to produce a "dipeptide", containing a newly formed peptide bond, and a molecule of water.

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Vegetarian:

Back 69

people who exclude meat, poultry, fish or other animal derived foods from their diet

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Lactovegetarian:

Back 70

people who include milk and milk products but exclude meat, poultry, fish, seafood and eggs from their diet

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Lacto-ovo-vegetarian:

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people who include milk and milk products as well as eggs in their diet, but exclude meat, poultry, fish and seafood

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Vegan (pure vegetarians, strict vegetarians):

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people who exclude all animal derived foods from their diets

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Pescovegetarian (or pescetarian):

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individuals who eat fish and seafood but exclude meat from their diets. These individuals generally eat eggs, milk and milk products.

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Important Concepts for Vegetarian Diet Planning:

Back 74

obtaining adequate amounts of the following: protein – complimentary proteins, energy to spare-protein, calcium, zinc, iron, Vitamin B12, vitamin D, and omega 3 Fatty acids

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Kwashiorkor

Back 75

= a sudden protein deficiency and acute or sudden deprivation of food. Generally affects 1-3 year old children. Often occurs when weaned off breastfeeding because a second child is born. Edema and an enlarged liver contribute to the appearance of a swollen belly. (Edema occurs as a result of albumin and plasma protein loss thereby contributing to leaking of fluid into the interstitial spaces. Enlarged and fatty liver occurs as a result of decreased synthesis of protein-fat transporters, preventing transport of fat from the liver)

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Marasmus

Back 76

= a severe and chronic deprivation of protein and energy, along with vitamins and minerals. It commonly affects children less than 2 years old and results in severe weight loss, muscle wasting, and changes to the skin and hair.

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Protein-energy malnutrition (PEM)

Back 77

= a deficiency in protein, energy or both. Acute PEM is caused by a recent severe food deprivation often characterized by children who are thin for their height. Chronic PEM is long-term food deprivation is often characterized by children being short for their age.

Front 78

What is the protein RDA for someone who weighs 60kg?

Back 78

60kg x 0.8g/kg = 48 g of protein per day.