Chapter 4 proteins

All proteins are composed of ______

amino acids

Like carbohydrates and fats, proteins have a basic structure of ?

carbon, hydrogen, and oxygen

Complete proteins are primarily of animal origin; examples include:

egg, milk, cheese, meat, poultry, fish

Hydrochloric acid begins the unfolding and denaturing of the complex protein chains. This unfolding makes the individual peptide bonds what?

more available for enzymatic action

Because proteins are relatively large, complex molecules, they are occasionally subject to what?

mutations or malformations in structure; for ex. protein-folding mistakes involved in Alzheimer's disease, cystic fibrosis, and other hereditary diseases

The normal pH of blood is what?

between 7.35 and 7.45; however, constant metabolic functions throughout the body release acidic and alkaline substances, thereby affecting the overall acidity and alkalinity of blood.

Body protein (ex. the lean mass of muscles) accounts for approximately three fourths of the dry matter in most tissues, excluding what?

bone and adipose tissue

Enzymes that are necessary for the digestion of protein are called?

proteases

The largest dry-weight portion of the body is _______.

protein

Key nutrients to consider for practicing vegetarians are what?

protein iron zinc calcium vitamin D vitamin B12 omega-3 fatty acids see page 48 table 4-1

Define incomplete proteins

protein foods that are deficient in one or more of the 9 indispensable amino acids

Define complete proteins

protein foods that contain all 9 indispensable amino acids in sufficient quantity and ration to meet the body's needs

define deamination

the removal of the nitrogen-containing part (amino group) from an amino acid; the remaining non-nitrogen residue will be used to make carbohydrates or fat, or it may be reattached to make another amino acid, if necessary

Dietary proteins are classified as 'complete or incomplete proteins' depending on what?

their amino acid composition

List of incomplete protein foods

these are primarily of plant origin: grains, legumes, nuts, seeds

Define lacto-ovo-vegetarian

these are vegetarians who follow a food pattern that allows for the consumption of dairy products and eggs. Their mixed diet consists of plant and animal food sources that exclude meat, poultry, pork, and fish only.

The RDA for both men and women is set at ?

0.8 g of high-quality protein per kilogram of desirable body weight per day Dietary recommendations are higher for infants and for pregnant and breastfeeding women in order to meet metabolic needs

Which 3 factors influence the body's requirement for protein?

1) tissue growth 2) the quality of the dietary protein 3) the additional needs that result from illness or disease--page 49

polypeptides are chains of up to _______ amino acids linked together

100

unlike carbs and fats, proteins is approximately ______% nitrogen

16%; protein is the primary source of nitrogen in the diet

The available fuel factor of protein is _______.

4 kcal.g

There are how many essential amino acids that must be supplied to the body through diet?

9; these amino acids are aka indispensable

List the 6 dispensable amino acids

Alanine Aspartic acid Asparagine Glutamic acid Serine Tyrosine

List the 5 conditionally amino acids

Arginine Cysteine Glutamine Glycine Proline

Religions related to a vegetarian diet

Buddhists, Hindus, Seventh-Day Adventists

The body's tissue proteins are constantly being broken down into amino acids through ______, and they are then resynthesized into tissue proteins as needed through ____.

Catabolism/anabolism

The comparative quality of protein foods may be assessed using several different methods; list 4 examples

Chemical score Biologic value Net protein utilization Protein efficiency ratio

List the 9 indispensable amino acids

Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine

What proteins are necessary to transport fats in the water-soluble blood supply?

Lipoproteins

The word amino refers to compounds that contain what?

Nitrogen

Children are at the highest risk for malnutrition because of their high needs during rapid growth and development; however PEM can affect anyone at any point throughout the life cycle. Those who can be affected by PEM?

People w/ poor nutrient intake (ex. the elderly, those w/ eating disorders) Individuals with elevated protein needs during infection or disease (ex. acquired immunodeficiency syndrome, cancer, liver failure)

________ are proteins hat play a major function in the metabolism of glucose.

Peptide hormones (ex. insulin, glucagon)

Malnutrition, illness, and starvation are examples of what?

Periods when negative nitrogen balance may occur

Define Vegan

Vegans follow a strict vegetarian diet and consume no animal foods. Their food pattern consists entirely of plant foods (ex. whole or enriched grains, legumes, nuts, seeds, fruits, vegetables). The use of soybeans, soy milk, soybean curd (tofu), and processed soy protein products enhances the nutritional value of the diet. Careful planning and sufficient food intake ensure adequate nutrition.

Protein is used to build special ________ and ________ as part of the body's immune system to help defend against disease and infection.

WBCs (lymphocytes) and antibodies

Define trypsin

a protein-splitting enzyme secreted as the inactive proenzyme trypsinogen by the small pancreas and that is activated and works in the small intestine to reduce proteins to shorter-chain polypeptides and dipeptides

Define chymotrypsin

a protein-splitting enzyme secreted as the inactive zymogen chymotrypsinogen by the pancreas; after it has been activated by trypsin, it acts in the small intestine to continue breaking down proteins into shorter-chain polypeptides and dipeptides

Define aminopeptidase

a specific protein-splitting enzyme secreted by glands in the walls of the small intestine that breaks off the nitrogen-containing amino end (ex. NH2) of the peptide chain, thereby producing smaller-chained peptides and free amino acids

Define carboxypeptidase

a specific protein-splitting enzyme secreted by the inactive zymogen procarboxypeptidase by the pancreas; after it has been activated by trypsin, it acts in the small intestine to break off the acid (ex. carboxyl) end of the peptides chain, thereby producing smaller-chained peptides and free amino acids

Proteins, after digestion/absorption, reassemble in a specific order to form what?

a variety of new proteins as needed by the body

Hydrochloric acid also provides the acid medium that is necessary to convert pepsinogen to what?

active pepsin; the gastric enzyme specific to proteins

Glands in the intestinal wall produce what two protein-splitting enzymes to complete the breaking down of protein and polypeptides and free the remaining amino acids?

aminopeptidase dipeptidase

Enzymes that are necessary for the digestion of carbohydrates are called?

amylase

define enterokinase

an enzyme produced and secreted in the duodenum in response to food entering the small intestine; it activates trypsinogen to its active form of trypsin

define zymogens

an inactive enzyme precursor

define proenzyme

an inactive precursor (ex. a forerunner substance from which another substance is made) that is converted to the active enzyme by the action of an acid, another enzyme, or other means

Define net protein utilization

based on the biologic value and the degree of the protein's digestibility

define biologic value

based on the nitrogen balance

define protein efficiency ratio

based on the weight gain of a growing test animal in relation to its protein intake

The specific types of protein found in different foods is unique; for ex. ________ is the protein found in cheese/milk and _______ is in egg whites, and ______ is found in wheat products.

casein in milk/cheese albumin in egg whites gluten in wheat products

Rennin and calcium act on the _______ of milk to produce a curd

casein; by coagulating milk into a more solid curd, rennin prevents the food from passing too rapidly from the infant's stomach to the small intestine.

list common foods that contain aspartame

chewing gum diet soda frozen desserts gelatins puddings sugar-free candies yogurt

Kwashiorkor is more common among children who are what?

children 18 and 24 months who have been breastfed all their lives, and who are then rapidly weaned, often because of the arrival of a younger sibling.

What is the DRIs for proteins

children and adults should obtain 10%-35% of their total caloric intake from protein

Soy is a plant protein and is a _______ protein.

complete; Soy products are the only plant sources of complete proteins. This is why it is easy for vegans/vegetarians to maintain a healthy protein balance in their diet without consuming animal products.

To maintain nitrogen balance, the part of the amino acid that contains nitrogen may be removed by ________, converted into ammonia, and then excreted as urea in the urine.

deamination

define chemical score

derived from the amino acid pattern of the food; a high-quality protein food, such as an egg (w/ a value of 100), is compared w/ other foods according to their amino acid rations

Two amino acids joined together are called a ____

dipeptide

Characteristics of marasmus:

emaciated appearance with little or no body fat; this is a chronic form of energy and protein deficiency (starvation), stunted growth and development are more severe with this form of malnutrition. effects all ages w/ inadequate food sources

In addition to its basic tissue-building function, protein has other critical body functions related to what?

energy water balance metabolism the body's defense system

Trypsin, which is secreted first as inactive trypsinogen, is activated by the enzyme ___________

enterokinase

Protein makes up the bulk of the muscles, internal organs, brain, nerves, skin, hair, and nails; and it is also a vital part of regulatory substances such?

enzymes, hormones, and blood plasma

The body's nitrogen balance indicates how well its tissues are being maintained. The intake and use of dietary protein are measured by the amount of nitrogen supplied by food protein and the amount of nitrogen-what

excreted in the urine; for ex. 1g. of urinary nitrogen results from the digestion and metabolism of 6.25g of protein. Thus, if 1g of nitrogen is excreted in the urine for every 6.25g of protein consumed, the body is said to be in nitrogen balance.

The body compartments are separated with cell membranes that are not ________ to protein

freely permeable

Characteristics of kwashiorkor include:

generalized edema and fatty liver as a result of inadequate protein intake to maintain fluid balance and to transport fat from the liver

Define PKU; Phenylketonuria

genetic disorder in which the affected individual lacks the enzyme needed to convert phenyl aline to tyrosine; therefore, tyrosine becomes an indispensable amino acid for individuals w/ PKU. A specific diet must be followed and certain food avoided as phenylalanine levels in the blood can rise to toxic levels (aspartame/phenylketonuria) see box page 43

_________ is the vital oxygen carrier in the red blood cells.

hemoglobin

What 3 agents in the gastric secretions help aid in the enzymatic breakdown of protein?

hydrochloric acid pepsin rennin

Protein-energy malnutrition (PEM) or severe acute malnutrition (SAM) may occur in a variety of situations; the most severe cases are found where?

in areas where all foods- not just protein-rich foods--are in short supply

The mechanical breakdown of proteins starts in the mouth, and the chemical digestion starts where?

in the stomach; the stomach's chief digestive function is to carry out the first state of the enzymatic breakdown of protein.

Unlike the enzymes involved in protein digestion (ex. proteases) are stored as what?

inactive proenzymes called zymogens

The 'negative' nitrogen balance occurs when the body excretes more nitrogen than it keeps. This happens when the body has what?

inadequate dietary supply of protein and/or total energy. In this case, it is necessary for the body to catabolize body tissue containing protein in order to meet other critical functions

Gelatin is an animal protein but is _______.

incomplete; it lacks the 3 essential amino acids tryptophan, valine, and isoleucine, and it only have small amounts of leucine.

A total of 20 common amino acids have been identified, all of which are vital to life and health; these are classified?

indispensable dispensable or conditionally indispensable- according to whether the body can make them

The gastric enzyme rennin is only present during what?

infancy and childhood; is especially important for the infant's digestion of milk to produce a curd.

Fluids within the body are divided into what 3 compartments

intravascular intracellular interstitial

Negative nitrogen balance is also seen in individuals when protein deficiency ---even when kilocalories from carbohydrate and fat are adequate ----causes the classic protein deficiency disease known as what?

kwashiorkor

What are 2 severe forms of PEM?

kwashiorkor (acute/fatal) marasmus (chronic)

Enzymes that are necessary for the digestion of fats are called?

lipase

A positive nitrogen balance also occurs in individuals who have been ill or malnourished and who are being "built back up" with increased ________

nourishment; in such cases, protein is used to meet increased needs for tissue building and its associated metabolic activity

Because water is attracted to protein, plasma proteins such as albumin help to control water balance throughout the body by exerting what?

osmotic pressure; this pressure maintains the normal circulation of tissue fluids within the appropriate compartments

Protein digestion begins in the acidic medium of the stomach, and it is completed in the 'alkaline' medium of the small intestine. Enzymes from the secretions of both the ______ and the _____ take part in this process.

pancreas and small intestine

Each amino acid is joined by a _____

peptide bond

When food high in protein are eaten, the protein is broken down into amino acids by breaking the _______ during the digestive process.

peptide bonds

The "active" trypsin works on proteins and large polypeptides fragments that arrive from the _________

stomach

A 'positive' nitrogen balance exists when the body holds on to more nitrogen than it excretes, thus storing more nitrogen in the form of protein (by building tissue) than it is losing (by breaking down tissue) this situation occurs normally during periods of what?

rapid growth, such as infancy, childhood, adolescence, pregnancy, and lactation

Hundreds for amino acids are linked together to form a _______

single protein

Some proteins contain small but valuable amounts of which minerals?

sulfur phosphorus iron iodine

Define dispensable amino acids

the 5 amino acids that the body can synthesize from other amino acids that are supplied through the diet and thus do not have to be consumed on a daily basis

Define conditionally indispensable amino acids

the 6 amino acids that normally considered dispensable amino acids because the body can make them; however, under certain circumstances (ex. illness) the body cannot make them in high enough quantities, and they become indispensable (cannot do without) in the diet

Define indispensable amino acids

the 9 amino acids that must be obtained from the diet because the body does not make adequate amounts to support body needs

The enzymes needed for protein digestion cannot be stored in an 'active' form because?

the cells and organs that produce and store them (which are made of structural proteins) would be digested as well

define pepsin

the chief digestive enzyme in the stomach, which breaks down proteins into polypeptides; activated by hydrochloric acid

Define dipeptidase

the final enzyme in the protein-splitting system that releases free amino acids from dipeptide bonds

The failure to maintain the nitrogen balance may not become apparent for some time, but it eventually causes what?

the loss of muscle tissue, the impairment of body organs and functions, and an increased susceptibility to infections. In children, an extended period causes growth retardations and may be fatal

Define Catabolism

the metabolic process of breaking down large substances to yield smaller building blocks

Define anabolism

the metabolic process of building large substances from smaller parts; the opposite fo catabolism

Define ovo-vegetarian

the only animal foods included in this diet are eggs. Because eggs are an excellent source of complete proteins, individuals who are following this diet do not have to be overly concerned with complementary proteins if eggs are consumed consistently

define osmotic pressure

the pressure that is produced as a result of osmosis across a semipermeable membrane

Define lacto-vegetarian

these vegetarians accept only dairy products from animal sources to complement their basic diet of plant foods. The use of milk and milk products (ex. cheese) with a varied mixed diet of whole or enriched grains, legumes, nuts, seeds, fruits, and vegetables in sufficient quantities to meet energy needs; provides a balanced diet

The primary functions of protein are what?

to repair worn-out, wasted, and or damaged tissue and to build new tissue

_________ is the iron transport protein in blood

transferrin

Three amino acids joined together are called a _____

tripeptide

Which 3 enzymes produced by the 'pancreas' continue breaking down proteins into more and more substances?

trypsin chymotrypsin carboxypeptidase