CH.8 Protein

complete proteins

(relating to protein quality) they contain all 9 essential amino acids in appropriate proportions ex: eggs are high in protein quality b/c they contain all 9 essential amino acids in amounts and proportions that best support protein synthesis in the body. Other high-quality protein include animal foods (meat, fish, dairy, eggs) and plant based foods like soy, quinoa, and amaranth

Dipeptide

2 amino acids

Essential Amino Acids

9 of 20 amino acids that cannot be produced by the human body and therefore must be obtained from food; they include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine

o Atrophic gastritis

A condition that results in insufficient hydrochloric acid production by the stomach

black beans.

Each of the following food choices is a source of complete proteins, EXCEPT: beef. black beans. eggs. quinoa. yogurt.

e. Both b and c are true.

Nick lifts weights and takes a daily protein supplement in addition to his 30% protein weight-maintenance diet. Taking the protein supplement: a. is an effective practice to add muscle weight without exercise. b. is not necessary because his intake is already in excess of the RDA. c. provides additional calories that can contribute to fat stores. d. will increase his athletic performance. e. Both b and c are true.

a change in shape of protein structure due to heat, light, motion, or change in pH.

Protein denaturation refers to: the lack of one or more essential amino acids in a food. the process of adding an amino acid to a food that is not naturally present. a change in shape of protein structure due to heat, light, motion, or change in pH. breakdown of muscle mass during caloric restriction. the conversion of protein to glucose or fatty acids.

0.8 g/kg/d. The AMDR for protein is 10% to 35% of total calories.

RDA for adults is

• Much of the structural material in the body is provided by protein; its constituents are found in muscle, bone, hair, skin, and fingernails. • They also carry out critical functions, such as facilitating chemical reactions through enzymes: regulating most body and cellular functions by hormones, maintaining fluid balance, fighting off bacteria, and blood clotting. • On a larger scale, allow body to move

Roles of Protein in the Body

• PEPTIDE BOND: The bond that forms between 2 amino acids in formation of a protein molecule. o Peptides: short chain of amino acids attached together Dipeptide-2 amino acids What is the largest protein fragment that can be absorbed into the mucosal cells lining the small intestine? Tripeptide-3 amino acids; largest protein fragments to be absorbed into mucosal cells Polypeptide-many amino acids; ALL PROTEINS = polypeptides o The sequence of amino acids and types of amino acid distinguish one protein from another o 20 total amino acids

What is a chain of amino acids called?

Tripeptide(3 amino acids; largest protein fragments to be absorbed into mucosal cells)

What is the largest protein fragment that can be absorbed into the mucosal cells lining the small intestine?

• Interactions between these amino acids in sequence cause the protein to fold into a 3d shape. ***SHAPE determines FUNCTION of protein***; sequence of amino acids determines 3D shape of protein

What provides the information necessary to specify the three-dimensional shape of a protein?

nitrogen

____________ is the key element that distinguishes protein from other macronutrients

Marasmus

a condition caused by inadequate intake of protein, calories, and other nutrients; it is characterized by emaciation.

• Nitrogen balance

a reflection of protein intake versus protein breakdown and is influenced by diet, hormones and growth factors, and muscle contractions

: a molecule containing a central carbon atom (C), an amino group that contains an atom of nitrogen (written as chemical formula NH2), an acid group (COOH), and a variable side chain ONLY the SIDE chain differs for each amino acid, giving each its unique properties

building blocks of protein/amino acids

a) stomach b) lumen c) mucosal cells

digestion of protein begins in the ____a______, where proteins are denatured and fragmented, continues in the _____b____ of the small intestine, and is completed within the ______c______ of the small intestine.

Polypeptide

many amino acids; ALL PROTEINS =

adequate diet, hormones and growth factors, plus muscle contractions

o Three factors are required to retain body proteins (lean body mass)

Messenger Ribonucleic Acid (mRNA)

type of RNA that carries the genetic code for a specific protein from the nucleus to the cytoplasm where proteins are made.

plant-based

• Adopting a more ___________ diet ,ay help align our protein intake w/ RDA and provide other health advantages

edema

swelling caused by excess fluid trapped in body tissues. When a protein in blood, called ALBUMIN, gets too low, fluid is retained in extremities and __________ occurs.

• A higher protein intake (~1.2 g/kg/d) for adults older than 65 or 70 yrs appears to be of benefit in maintaining a healthy body weight and protecting against frailty by reducing the loss of lean body mass, improve functionality, and reduce the risk of disability and death, particularly when combined w/ resistance training program o b/c of decreases in physical activity and a number of other factors, most elderly individuals experience a loss of lean body mass, primarily from skeletal muscle which is associated w/ high risk of disability and death. • For middle aged (50-65yrs) individuals however, consuming protein in line w/ RDA (0.7-0.8 g/kg/d) is actually beneficial for prevention of cancer, overall mortality, and possibly diabetes. This protein intake less than what is already consumed by most US adults • Health benefits of both a higher protein intake in older adults and lower protein intake for middle-aged adults are maximized when plant foods make up the majority of food intake.

Seniors May Benefit From Higher Intakes of Protein

10% to 35% of total calories.

The Institute of Medicine has established that a safe range of protein intake is: 10% to 25% of total calories. 10% to 35% of total calories. 15% to 30% of total calories. 15% to 35% of total calories. 20% to 40% of total calories.

PEPTIDE BOND

The bond that forms between 2 amino acids in formation of a protein molecule.

INCOMPLETE proteins

(relating to protein quality) foods w/ lower protein quality; lack or supply low amounts of one or more of the 9 essential amino acids thus disrupting or limiting protein synthesis o Most plant foods are incomplete proteins and vary in types ond proportions of amino acids they contain. HOWEVER, all essential amino acids needed for protein synthesis can be supplied by consuming two or more "complementary" protein plant foods (for ex: rice and beans provide protein complementation which have different limiting amino acids). This explains why vegans can still meet protein requirements

translation

(step 2 protein synth) 2nd step in protein synthesis in which the information in messenger RNA is translated into a protein

• Long-term studies of weight loss suggest high-protein diets may help take weight off at first, but over time, studies show little difference between diets higher and lower in protein in maintaining weight loss • Some high-protein diets don't provide the variety of foods needed to adequately meet all nutritional needs. • High-protein diets are often rich in saturated fat and cholesterol but low in fiber, phytochemicals, and certain vitamins and minerals, since people are eating fewer grains, vegetables, and fruits. As a result, the American Heart Association does NOT recommend high-protein diets, since the typical intake may put people at risk of cardiovascular problems

High-Protein Diets

• Kwashiorkor

a condition caused by an inadequate protein intake with reasonable caloric intake. In other words, when someone doesn't eat enough protein but they meet their energy needs, usually through carbohydrates o it is characterized by a swollen belly, caused by edema and a fatty liver in developing countries who eat mostly grains, and who are often shorter, more prone to infections, and experience changes in hair color and flaky skin.

Protein Turnover

the continuous breakdown and re-assembly of proteins in the body o although we consume about 70grams to 100grams of protein daily, approximately 300 grams of proteins in cells and fluids throughout the body are broken down and resynthesized each day o most amino acids released breakdown of body proteins are reused in production of new proteins, but some amino acids are metabolized (chemically altered), which prevents them from being used for protein synthesis. These modified amino acids must be replaced from dietary proteins to provide sufficient amino acids to remake all body proteins that were broken down

Divide your current body weight in pounds by 2.2 to convert to kilograms, and then multiply that number by 0.8grams of protein per kilogram of body weight per day (g/kg/d) (ex: If weight in pounds is 170lbs (1kg =2.2lbs): 170/2.2 = 77.3 kg77.3 kg × 0.8 = 61.84 grams of protein per day)

• How to calculate RECOMMENDED DIETARY ALLOWANCE (RDA) for protein:

o In many cases, the metabolism of amino acids requires that they first be stripped of their amino group, which leaves a CARBON SKELETON used primarily to synthesize glucose to maintain blood glucose levels when carbohydrate intake is low, or to a lesser degree, as a direct source of energy o In times of energy ABUNDANCE, the body may also convert amino acids to fatty acids that are then stored in adipose tissues as triglycerides

• If amino acids generated from protein breakdown are reused for protein synthesis, why is it necessary for a nongrowing adult to eat any protein?

The amino acid in the shortest supply relative to its requirement

• Limiting Amino Acid

actin and myosin

• Protein serves as a structural part of skeletal muscles and bone (along w/ many tissues, organs, blood cells, hair, and nails). Two proteins, ______________, compose ~50% of total muscle proteins and they are the primary proteins that enable muscles to contract

transcription

(step 1 protein synth) Segments of DNA called genes provide the "Instructions" for the assembly of amino acids into particular proteins. The instructions are transcribed into mRNA a. Deoxyribonucleic Acid (DNA): Nucleic acid that stores the bodies genetic info; it is made of a double strand of nucleotides subunits. b. Messenger Ribonucleic Acid (mRNA): type of RNA that carries the genetic code for a specific protein from the nucleus to the cytoplasm where proteins are made.

Nonessential ("dispensable") Amino Acids

11 amino acids that the body can manufacture and therefore need not be obtained through diet

Tripeptide

3 amino acids; largest protein fragments to be absorbed into mucosal cells

nitrogen balance

: A measure of nitrogen intake (primarily from protein) minus nitrogen excretion in urine and feces; reflects if a body is gaining, losing or maintaining protein. How scientists can measure in urine to study protein turnover Nitrogen losses from less significant sources (sweat, skin, hair, nails, breath, saliva, mucus and other secretions) are estimated As nongrowing, weight-stable adults, we have approximately the same amount of total protein in our body from day to day, so we are in nitrogen balance, such that the amount of nitrogen we consume (Nin) is equal to the nitrogen we excrete (Nout), or Nin = Nout. o Three factors are required to retain body proteins (lean body mass): adequate diet, hormones and growth factors, plus muscle contractions. a growing child, a pregnant woman, or someone who is just starting a resistance-training (weight-lifting) program will be increasing their mass of total body proteins, so they must excrete less nitrogen than they consume, or Nin is greater than Nout. --Low-calorie diets for weight loss lead to negative nitrogen balance.

• Denaturation

: the process by which the shape of a protein is altered; this can be caused by exposure to heat, extreme changes of pH, light, acid or chemical reaction o _______________ Can cause proteins to function improperly; ex: heat or change in pH could destroy the function or damage the protein hemoglobin, which carries oxygen in the blood o In our bodies, ___________- by stomach acid (hydrochloric acid) unfolds a food protein in the stomach. Unfolding allows the enzyme PEPSIN, produced by cells lining the stomach, to access the peptide bonds and increase the digestibility of the protein o Once the protein fragments enter the small intestine, enzymes released from the pancreas (proteases) break the strings of amino acids into peptides (short chains of amino acids). These peptides are digested further by enzymes on surface of intestinal mucosa, and dipeptides, tripeptides (largest protein fragments to be absorbed into mucosal cells), and individual amino acids are then absorbed by mucosal cells of small intestine with assistance of various transport proteins. o From mucosal cells the amino acids are transported into blood by additional transport proteins

serving as a store of excess amino acids.

Functions of protein do NOT include: serving as an energy source. serving as a structural component of hair and fingernails. serving as a store of excess amino acids. serving as hormones. catalyzing chemical reactions in the body.

nitrogen.

Like carbohydrates and fat, protein is composed of carbon, hydrogen, and oxygen. Protein differs in that it also contains: calcium. chloride. nitrogen. phosphorus. sodium.

is characterized by deficiency in most nutrients, including protein.

Marasmus is characterized by deficiency in most nutrients, including protein. is characterized by sufficient total caloric intake, but deficient intake in protein. is associated with a swollen belly appearance. only occurs in children. may occur when consuming excess calories from carbohydrates.

can be manufactured in the body.

Nonessential amino acids: are incomplete proteins. are extra essential amino acids. can be manufactured in the body. enhance muscle development. are found only in plant foods.

Deoxyribonucleic Acid (DNA)

Nucleic acid that stores the bodies genetic info; it is made of a double strand of nucleotides subunits.

• More than 60% of protein Americans consume is from animal products such as meat and dairy foods and combined w/ protein found in plant foods, most of us exceed the RDA for protein • Adopting a more PLANT-BASED diet ,ay help align our protein intake w/ RDA and provide other health advantages o Protein Quality: a measure of how well a protein meets our needs for protein synthesis; based on the proportion of essential amino acids present --- Ex: eggs are high in protein quality b/c they contain all 9 essential amino acids in amounts and proportions that best support protein synthesis in the body. Other high-quality protein include animal foods (meat, fish, dairy, eggs) and plant based foods like soy, quinoa, and amaranth = COMPLETE proteins in that they contain all 9 essential amino acids in appropriate proportions INCOMPLETE proteins= foods w/ lower protein quality; lack or supply low amounts of one or more of the 9 essential amino acids thus disrupting or limiting protein synthesis o Most plant foods are incomplete proteins and vary in types ond proportions of amino acids they contain. HOWEVER, all essential amino acids needed for protein synthesis can be supplied by consuming two or more "complementary" protein plant foods (for ex: rice and beans provide protein complementation which have different limiting amino acids). This explains why vegans can still meet protein requirements • Limiting Amino Acid: The amino acid in the shortest supply relative to its requirement

Protein Quality

• Body needs amino acids from the diet to replace proteins that are lost when cells from our skin and those lining our gastrointestinal tract are shed • Dietary proteins also needed to allow for accumulation of additional body protein mass that occurs with growth, pregnancy, increasing muscle mass, and to support the growth of hair and nails as well as for wound healing • EXCESS proteins are used as an energy source or stored as fat. • PROTEIN TURNOVER: the continuous breakdown and re-assembly of proteins in the body o although we consume about 70grams to 100grams of protein daily, approximately 300 grams of proteins in cells and fluids throughout the body are broken down and resynthesized each day o most amino acids released breakdown of body proteins are reused in production of new proteins, but some amino acids are metabolized (chemically altered), which prevents them from being used for protein synthesis. These modified amino acids must be replaced from dietary proteins to provide sufficient amino acids to remake all body proteins that were broken down

Protein Turnover

• Not consuming enough protein prevents us from being able to synthesize the proteins we need to meet physiological demands, and this results in detrimental effects in body structure and function • Kwashiorkor: a condition caused by an inadequate protein intake with reasonable caloric intake. In other words, when someone doesn't eat enough protein but they meet their energy needs, usually through carbohydrates o it is characterized by a swollen belly, caused by edema and a fatty liver in developing countries who eat mostly grains, and who are often shorter, more prone to infections, and experience changes in hair color and flaky skin. • Marasmus: a condition caused by inadequate intake of protein, calories, and other nutrients; it is characterized by emaciation. • Protein malnutrition in "malnutrition hotspots" are a complex mixture of environmental, economic, social and political factors • In developed countries like US, most protein deficiencies occur in alcoholics who swap food for alcohol, and in people w/ long-term illnesses, malabsorption, or injuries that prevent them from eating well

Protein-Deficiency Diseases

• Protein Synthesis

The process of building peptide chains and proteins from amino acids using information provided by genes; synthesis is a 2 step process of transcription and translation o 2 steps of ____________. 1. Transcription: Segments of DNA called genes provide the "Instructions" for the assembly of amino acids into particular proteins. The instructions are transcribed into mRNA. a. Deoxyribonucleic Acid (DNA): Nucleic acid that stores the bodies genetic info; it is made of a double strand of nucleotides subunits. b. Messenger Ribonucleic Acid (mRNA): type of RNA that carries the genetic code for a specific protein from the nucleus to the cytoplasm where proteins are made. 2. Translation: 2nd step in protein synthesis in which the information in messenger RNA is translated into a protein --Once the synthesis of protein is completed, it has not necessarily taken its final form; unique nature of each amino acid in sequence prevents protein from remaining in straight line o Ex: some proteins, such as hemoglobin, contain more than one protein chain linked together

translation.

The second step of protein synthesis in which the order of amino acids added to the growing protein chain is read from (or dictated by) the information in the mRNA is termed: phosphorylation. gluconeogenesis. transcription. translation. deamination.

function

The shape of a protein is a determinant of its _______ in the body. storage form energy potential function heat production permanence

9; 11

There are 20 amino acids present in proteins; of these ______ are considered essential and are ______ considered nonessential amino acids. 7; 13 13; 7 15; 5 9; 11 11; 9

• Robert Wolfe (PhD) calculated after body-builders conference that body builders were getting more than 5x amount of protein recommended for normally active person o Body builders thought they needed it to build and maintain muscle; some studies show that if doing weight lifting or other sports, a higher protein intake helps you gain muscle faster • Protein serves as a structural part of skeletal muscles and bone (along w/ many tissues, organs, blood cells, hair, and nails). Two proteins, actin and myosin, compose ~50% of total muscle proteins and they are the primary proteins that enable muscles to contract • Protein functions that extend beyond contractile roles in muscles: o Enzymes catalyze chemical reactions in body o Hormones regulate nearly every bodily function o Hemoglobin transports oxygen o Albumin transports a variety of nutrients o Proteins also have central roles in IMMUNITY and BLOOD CLOTTING o Proteins help maintain a proper BALANCE of FLUID around the body, both inside and outside cells, which wards off swelling (such as in ankles) and supports normal blood pressure. Edema: swelling caused by excess fluid trapped in body tissues. When a protein in blood, called albumin, gets too low, fluid is retained in extremities and edema occurs.

Varied Functions of Protein

o Protein Quality: a measure of how well a protein meets our needs for protein synthesis; based on the proportion of essential amino acids present Ex: eggs are high in protein quality b/c they contain all 9 essential amino acids in amounts and proportions that best support protein synthesis in the body. Other high-quality protein include animal foods (meat, fish, dairy, eggs) and plant based foods like soy, quinoa, and amaranth = COMPLETE proteins in that they contain all 9 essential amino acids in appropriate proportions INCOMPLETE proteins= foods w/ lower protein quality; lack or supply low amounts of one or more of the 9 essential amino acids thus disrupting or limiting protein synthesis o Most plant foods are incomplete proteins and vary in types ond proportions of amino acids they contain. HOWEVER, all essential amino acids needed for protein synthesis can be supplied by consuming two or more "complementary" protein plant foods (for ex: rice and beans provide protein complementation which have different limiting amino acids). This explains why vegans can still meet protein requirements • Limiting Amino Acid: The amino acid in the shortest supply relative to its requirement

Why is the RDA for protein higher for children than it is for adults?

o Protein Quality

a measure of how well a protein meets our needs for protein synthesis; based on the proportion of essential amino acids present Ex: eggs are high in protein quality b/c they contain all 9 essential amino acids in amounts and proportions that best support protein synthesis in the body. Other high-quality protein include animal foods (meat, fish, dairy, eggs) and plant based foods like soy, quinoa, and amaranth = COMPLETE proteins in that they contain all 9 essential amino acids in appropriate proportions INCOMPLETE proteins= foods w/ lower protein quality; lack or supply low amounts of one or more of the 9 essential amino acids thus disrupting or limiting protein synthesis o Most plant foods are incomplete proteins and vary in types ond proportions of amino acids they contain. HOWEVER, all essential amino acids needed for protein synthesis can be supplied by consuming two or more "complementary" protein plant foods (for ex: rice and beans provide protein complementation which have different limiting amino acids). This explains why vegans can still meet protein requirements • Limiting Amino Acid: The amino acid in the shortest supply relative to its requirement

proteases

o In our bodies, denaturation by stomach acid (hydrochloric acid) unfolds a food protein in the stomach. Unfolding allows the enzyme PEPSIN, produced by cells lining the stomach, to access the peptide bonds and increase the digestibility of the protein Once the protein fragments enter the small intestine, enzymes released from the pancreas (_____________) break the strings of amino acids into peptides (short chains of amino acids). These peptides are digested further by enzymes on surface of intestinal mucosa, and dipeptides, tripeptides (largest protein fragments to be absorbed into mucosal cells), and individual amino acids are then absorbed by mucosal cells of small intestine with assistance of various transport proteins. o From mucosal cells the amino acids are transported into blood by additional transport proteins

pepsin

o In our bodies, denaturation by stomach acid (hydrochloric acid) unfolds a food protein in the stomach. Unfolding allows the enzyme __________, produced by cells lining the stomach, to access the peptide bonds and increase the digestibility of the protein o Once the protein fragments enter the small intestine, enzymes released from the pancreas (PROTEASES) break the strings of amino acids into peptides (short chains of amino acids). These peptides are digested further by enzymes on surface of intestinal mucosa, and dipeptides, tripeptides (largest protein fragments to be absorbed into mucosal cells), and individual amino acids are then absorbed by mucosal cells of small intestine with assistance of various transport proteins. o From mucosal cells the amino acids are transported into blood by additional transport proteins

digestion of protein begins in the stomach, where proteins are denatured and fragmented, continues in the lumen of the small intestine, and is completed within the mucosal cells of the small intestine.

process of digestion

10% to 35% of total kcal. (o In the United States, recent nutrition surveys report average protein intake close to 16% of total calories, with men consuming about 100g and women consuming close to 70g These protein intake levels are within the AMDR, but well above the RDA for most people. )

• Acceptable Macronutrient Distribution Range (AMDR) for protein is...

o Once the protein fragments enter the small intestine, enzymes released from the pancreas (proteases) break the strings of amino acids into peptides (short chains of amino acids). These peptides are digested further by enzymes on surface of intestinal mucosa, and dipeptides, tripeptides (largest protein fragments to be absorbed into mucosal cells), and individual amino acids are then absorbed by mucosal cells of small intestine with assistance of various transport proteins. o From mucosal cells the amino acids are transported into blood by additional transport proteins

• Atrophic gastritis is a condition that results in insufficient hydrochloric acid production by the stomach. Describe why this condition would decrease the efficiency of protein digestion.

complete or incomplete proteins

• Depending on the proportion of each of the essential amino acids present (protein quality), foods can be classified as

large molecules consisting of carbon, hydrogen, oxygen, and nitrogen assembled in one or more chains of amino acids. -o NITROGEN is the key element that distinguishes protein from other macronutrients Nitrogen supplied by the building blocks of proteins or amino acids: a molecule containing a central carbon atom (C), an amino group that contains an atom of nitrogen (written as chemical formula NH2), an acid group (COOH), and a variable side chain ONLY the SIDE chain

• Protein

o Enzymes catalyze chemical reactions in body o Hormones regulate nearly every bodily function o Hemoglobin transports oxygen o Albumin transports a variety of nutrients o Proteins also have central roles in IMMUNITY and BLOOD CLOTTING o Proteins help maintain a proper BALANCE of FLUID around the body, both inside and outside cells, which wards off swelling (such as in ankles) and supports normal blood pressure.

• Protein functions that extend beyond contractile roles in muscles:

sex, age, total calorie intake, and factors related to exercise, such as how long and hard you work out • "Athletes don't need any more protein than the average person. What an athlete can benefit from," he says, "is a higher protein intake than the average person—which I call an optimal protein intake."-- Stuart Phillips, PhD, professor of kinesiology at McMaster University in Ontario

• Protein metabolism is affected by...

carbon, hydrogen, and oxygen, but also contain nitrogen, which is supplied through amino acids, the building blocks of protein.

• Proteins are composed of

protein turnover

• Proteins in the body are constantly being broken down into amino acids and reassembled in a process called ____________

genes

• Sequences of DNA called _________ provide the instructions for the synthesis of every protein in the body. This is a two-step process that begins in the nucleus with gene transcription and is completed in the cytoplasm with translation.

shape

• The overall ________ of a protein molecule determines its function, and how it interacts with other molecules.

UREA (o When amino acids are used for energy, or to synthesize glucose or fatty acids, the amino group that was stripped off must be disposed of; otherwise it would accumulate in the body as AMMONIA which is toxic o To prevent this, the LIVER converts ammonia to less toxic substance called UREA. Urea is then released into the blood, filtered by the kidneys, and excreted in urine.)

• What is a toxic waste product of amino acid breakdown that must be excreted from the body?