Nutrition Exam 3 Review: Chapter 7

Amino acids

-Amino acids needed to make body proteins are supplied by the protein containing foods we eat and through cell synthesis. -Each amino acid composed of central carbon bonded to 4 groups of elements: a nitrogen (amino) group, an acid (carboxyl group), hydrogen, and a side chain (Letter R). -There are 20 amino acids the body needs to function -11 non-essential amino acids - 9 essential amino acids

Forming Hormones, Enzymes, and Neurotransmiters

-Amino acids required for the synthesis of most hormones in body -Hormones can be made from 1 or multiple amino acids -Hormones act as messengers in body and aid in regulatory functions. -Amino acids are needed to make enzymes -Cells contain thousands of enzymes that facilitate chemical reactions needed for metabolism -Neuotransmitters released by nerve endings also derived from amino acids (dopamine, noepinephrine, serotonin)

Pool

-Amount of a nutrient found within the body that can be easily mobilized when needed

Contributing to Immune Function

-Antibody proteins are key in immune system -Antibodies bind to foreign proteins (called antigens) that invade body and prevent their attack on target cells. -Without sufficient protein, immune system lacks the material needed to build this defense. -Immune incompetence called anergy develops and reduces body's ability to fight infection.

Lacto-Vegetarians

-Are similar to vegans because their diets exclude meat, poultry, eggs, and fish, but differ in that they include dairy products.

Lacking In Vegetarian Diets

-BV protein -Riboflavin -Vitamin D -Vitamin B-12 -Calcium -Zinc -Unless carefully planned

Protein Synthesis

-Begins at a specific starting point on the mRNA indicated by AUG and continues until stop codon is reached. -Energy input from ATP is needed to add each amino acid to growing polypeptide chain (very costly to body in terms of energy use) -Key participant in protein synthesis in the cytosol is transfer RNA (tRNA).

Amino Acid Toxicity

-Body is designed to obtain protein through whole foods -This ensures that a balanced amount of amino acids is consumed -When individual amino acid supplements are taken, chemically similar amino acids can compete for absorption, resulting in amino acid imbalances and toxicity risk

Animal and plant proteins

-Can differ greatly in their proportions of essential and nonessential amino acids. -Animal proteins such as meat, poultry, fish, eggs, and milk contain ample amounts of all 9 essential amino acids. -In contrast Plants do not contain the needed amounts of essential amino acids.

Inadequate Protein Consumption

-Can impair metabolic processes because the body is unable to build the proteins it needs -For example the immune system no longer functions efficiently when it lacks key proteins, which leads to an increased risk of infection, disease, and, if severe, even death

Essential Amino Acids

-Cannot be synthesized in the body because body cells cannot make the carbon skeleton of the amino acid, cannot attach an amino group to the carbon skeleton, or cannot do the whole process fast enough to meet the body's needs

Proteins and Cells

-Cells require a pool of essential amino acids for the synthesis of body proteins. Thus, a single plant protein such as wheat cannot support the synthesis of body protein if it is the sole source of dietary protein -If low quality proteins are not planned, proteins cannot be made and the remaining amino acids may be used for energy or converted into carbs or fats.

Dietary Proteins

-Classified according to their amino acid composition. Because they contain sufficient amounts of all essential amino acids, animal proteins are classified as complete or high quality proteins -Plants proteins are not complete and are classified as incomplete or low quality proteins.

Protein Digestibility Corrected Amino Acid Score (PDCAAS)

-The most widely used measure of protein quality -Score is derived by multiplying a food's chemical score by its digestibility.

Gastrin

-The release of pepsin is controlled by the hormone gastrin -Thinking about food stimulates gastrin-producing cells of the stomach to release the hormone. -Strongly stimulates the stomach's parietal cells to produce acid, which in digestion and the activation of pepsin.

Protein Organization

-The sequential order and strong peptide bonding of amino acids in polypeptide chain, called primary structure, determines a protein's shape. -Amino acids must be accurately positioned in order for the amino acids to interact and fold correctly into the intended shape for the protein. This in turn allows weaker chemical bonds to form between amino acids near each other and stabilize the structure.

Tertiary Structure

-Unique 3 dimensional folding of a protein, determines the protein's overall shape and physiological function. -If a protein fails to form appropriate configuration, it cannot function.

Complementary Proteins

-When 2 or more plant proteins are combined to compensate for deficiencies in essential amino acid content in each protein, the proteins are called this -When they combine they can yield a high quality protein for the diet. -

mRNA translation

-When mRNA codons are read by ribosomes to produce a specific protein -Amino acids added one at a time to the polypeptide chain as directed by the instructions

Synthesis of Proteins

-Within the body cells, amino acids can be linked together by a chemical bond called a peptide bond to form needed proteins

Buffers

-compounds that help maintain acid base balance within a narrow range.

tRNA

-tRNA units take amino acids to the ribosomes as needed during protein synthesis. -tRNA carriers have a complementary code to the mRNA -numerous tRNA carriers are present during protein synthesis to continually supply the ribosomes with needed amino acids. -Once synthesis of polypeptide is completed, indicated by the ending codon, it is released from the ribosome, as is the mRNA.

Steps of DNA to protein

1). DNA unwinds for the amino acid sequence to be transcribed into a complementary messenger RNA (mRNA) 2). DNA stays in nucleus and mRNA travels to cytosol 3). mRNA goes to ribosome and ribosomes read codons on mRNA and translate those instructions to produce a specific protein.

Protein digestion steps

1). Stomach - protein is partially digested by the enzyme pepsin and hydrochloric acid 2). Pancreas - further protein digestion by enzymes released by the pancreas into the small intestine. 3). Small Intestine - Final digestion of protein to amino occurs in the small intestine. Chyme triggers the release of hormones secretin and cholecystokinin from the walls of the small intestine. Any remaining short peptides are broken down to individual amino acids by peptidase enzymes. 4). Liver - Amino acids are absorbed into the portal vein and transported to the liver. From there they enter the general bloodstream 5). Large Intestine - Little dietary protein is present in feces -It is uncommon for intact proteins to be absorbed from the digestive tract. However, in early infancy (up to 4 to 5 months of age), the gastrointestinal tract is somewhat permeable to small proteins, so some whole proteins can be absorbed.

Carbon Skeleton

Amino acid without the amino group

Protein Efficiency Ratio (PER)

- Another method for assessing a food's protein quality. -PER compares the amount of weight gain by a growing laboratory animal consuming a standardized amount of protein being studied with the weight gain by an animal consuming a standardized amount of a reference protein, such as casein. -PER of food reflects its BV because the weight gain and growth measures in the PER are dependent on the incorporation of food protein into body tissue.

Functions of Proteins

- Proteins function in many crucial ways in metabolism and in the formation of essential compounds and structures. Recall that the amino acids needed for the synthesis of proteins are supplied by the diet as well as by the recycling of body protein. -If we do not eat adequate amounts of carbs and fats, some amino acids will be used to produce energy, rendering them unavailable to build body proteins for other essential functions.

Protein RDA

-0.8 per kilogram of body weight -10-35% of energy intake should be protein -Daily intake of typical american man is 100g and 65g for women -Excess protein is metabolized for energy needs or used for other purposes.

Vegetarian Diets

-2.5% in US are vegetarian -4% in Canada are vegetarian -20-25% of Americans report they eat atleast 4 meatless meals a week -Most go vegetarian for religious, philosophical, ecological,, or health related reasons. -Some recognize that meat is not an efficient way of obtaining protein because it requires the use of approximately 40% of the world's grain production to raise meat-producing animals. -Diets Rich in fruits, vegetables, legumes, and grains frequently result in increased intakes of antioxidant nutrients, dietary fiber, and healthful phytochemicals, and decreased intakes of saturated fats and cholesterol.

Denaturation

-Alteration of a protein's 3-dimensional structure (Tertiary Structure) -Does not affect the protein's primary structure, unraveling a protein's shape often destroys its normal biological function. -Can be beneficial (Example: secretion of hydrochoric acid in stomach during digestion denatures food proteins, which increases their exposure to digestive enzymes and aids in the breakdown of polypeptide chains. Heat produced during cooking also can denature proteins, making them safer to eat (denatures harmful bacterial proteins) and more pleasing to eat. -Can be harmful to physiological function and overall health. During illness, changes in gastrointestinal acidity, body temp., or body pH can cause essential proteins to denature and lose their function.

DNA composition

-Composed of 4 nucleotides (building blocks of DNA). -Adenine (A) -Guanine (G) -Cytosine (C) - Thymine (T) -Each of the nucleotides is complimentary to (binds to) another nucleotide; A and T are complementary, as are C and G -DNA-coded instructions given for protein synthesis consist of a sequence of 3 nucleotides per unit of instruction, which dictate where each amino acid is to be placed in a protein and in which order. -Having the correct codons in the right sequence is critical for producing the needed amino acid and a normal protein (mistakes in order or types of amino acids can result in profound health consequences like sickle cell disease).

Protein Digestion and Absorption

-Cooking denatures proteins and softens the tough connective tissues in meat. This can make many protein rich foods easier to chew and aids in breakdown during digestion and absorption in GI tract -The enzymatic digestion of protein begins in the stomach with the secretion of hydrochloric

DNA Code

-Determines not only shape but also function of the protein. -If DNA contains errors, an incorrect mRNA will be produced and ribosomes in turn will read this incorrect message and produce an abnormal polypeptide. -Sickle cell anemia is example of what can happen when amino acid sequencing errors occur.

Denaturation of Proteins

-Exposure to acid or alkaline solutions, enzymes, heat, or agitation can change a protein's structure, leaving it in a denatured state. -

Peptide bonds

-Form between the amino group of 1 amino acid and the acid (Carboxyl) group of another. Through peptide bonding of amino acids, cells can synthesize dipeptides (joining of two amino acids), tripeptides (joining of 3 amino acids), oligopeptides (joining of 4 to 9 amino acids), and polypeptides (joining of 10 or more amino acids). -Most proteins are polypeptides, ranging from approximately 50 to 2000 amino acids. -Body can synthesize many different proteins by joining different combinations of amino acids with peptide bonds.

Positive Protein/Nitrogen Balance

-Greater intake of protein than loss -Needed during periods of growth, recovery, trauma, illness, or repairing tissues. -Hormones insulin, growth hormone, and testosterone all stimulate protein synthesis for the building of new tissue.

Quaternary Structure

-In some cases, 2 or more seperate polypeptides interact to form a large, new protein. An example is hemogoblin.

Lacto-ovo-vegetarians

-Include eggs but avoid meat

Special Concerns for infants and children

-Infants and children are at highest risk of nutrient deficiencies as a result of poorly planned vegetarian diets -Deficiency of iron, b-12, vitamin D, zinc, and calcium are highest concern

Nitrogen Balance

-Is a method to determine protein needs. -Healthy individuals who are not in periods of growth or recovering from illness or injury need to consume protein in an amount that replaces the protein lost in urine, feces, sweat, skin cells, hair, and nails.

Anergy

-Lack of an immune response to foreign compounds entering the body. -Can turn measles into a fatal disease for malnourished children -It also increase the risk of illness and infection in protein-deficient adults

Structure of Proteins

-Made of elements carbon, hydrogen, oxygen, and nitrogen -Some proteins contain sulfur

Side Chain of Amino Acids (R)

-Makes each amino acid unique and determines the structure, function, and name of the amino acid. -For example if R is a hydrogen, the amino acid is glycine; if R is a methyl group, the amino acid is alanine. -Some amino acids have chemically similar side chains. These special related amino acids form special classes, such as amino acids, basic amino acids, and branched chain amino acids. -Example is when acidic acids gain a hydrogen and become positively charged, this allows them to be part of a different enzymatic reaction.

Transporting Nutrients

-Many proteins function as transporters for other nutrients, carrying them through blood stream to cells and across membranes to sites of action -Example: protein hemoglobin carries oxygen from the lungs to cells. -Lipoproteins transport large lipid molecules from the small intestine through the lymph and blood to body cells. -Small vitamins and minerals have specific protein carriers that aid in their transport into and out of tissues and storage proteins. Examples include retinol-binding protein, trannsferrin and ferritin and ceruloplasmin.

Biological Value (BV)

-Measure of how efficiently the absorbed food protein is converted into body tissue protein. -If food possesses adequate amounts of all 9 essential amino acids, it should allow a person to efficiently incorporate amino acids from food protein into body protein. -BV is determined by comparing nitrogen retention in the body with content of food protein. More nitrogen is retained when a food's amino acid pattern closely matches the amino acid pattern of body protein. Better match = higher the BV -Egg white BV is 100, the highest BV of any single food

Capillary Beds

-Minute blood vessels, 1 cell thick, that create a junction between arterial and venous circulation. Gas and nutrient exchange occurs here between body cells and the blood. -Normal blood pressure in the arteries force blood into capillary beds. -Blood pressure is balanced by counteracting force of protein -Presence of these proteins in the capillary beds attract the right amount of fluid back to the blood, partially counteracting the force of blood pressure to maintain fluid balance.

Adaptation of Protein Synthesis to changing conditions (Protein Turnover)

-Most vital proteins in a constant state of breakdown, rebuilding and repair -^^^Protein Turnover allows cells to adapt to changing circumstances. -Example is when we eat more protein than is necessary for health, liver makes more enzymes to process the waste product from the resulting amino acid metabolism-namely, ammonia into urea. -Overall protein turnover is a process by which a cell can respond to its changing environment by increasing the production of needed proteins while reducing the production of proteins not currently needed.

Conditionally Essential Amino Acids

-Non essential amino acids that may become essential due to infancy, disease, or trauma. -Example is when a person with the genetic disease phenylketonuria has a limited ability to metabolize the non essential amino acid phenylalanine. -Glutamine and arginine may become essential after infection or trauma

Pepsin

-Once proteins are denatured by stomach, pepsin, a major enzyme produced by the stomach, begins to break the long polypeptide chains into shorter chains of amino acids through hydrolysis reactions. -Pepsin does not completely separate proteins into amino acids because it can break only a few of the many peptide bonds found in these large molecules. -Pepsin is actually stored as an inactive enzyme called pepsinogen to prevent it from digesting the stomach lining. -Once pepsinogen enters the stomach's acidic environment, part of the molecule is split off, forming the active enzyme pepsin.

Producing Vital Body Structures

-Primary protein function is to provide structural support to body cells and tissues. -Key structural proteins (collagen, actin, and myosin) constitute more than a third of body protein and provide a matrix for muscle, connective tissue, and bone. -During periods of growth, new proteins are synthesized to support the development of vital body tissues and structures. -In periods of malnutrition or disease, body proteins are often broken down to supply energy. Thus, the synthesis of protein for vital tissues drops below normal rates, eventually resulting in protein wasting and the development of a condition known as kwashiorkor.

DNA Transcription

-Process of forming messenger RNA (mRNA) from a portion of DNA.

Chemical Score

-Protein Quality can evaluated by chemical score -Calculated using the amount of each essential amino acid in a gram of the food being tested is divided by the ideal amount for that amino acid in a gram of the reference protein. -Lowest limiting amino acid ration that is calculated for the essential amino acids of the test protein is the chemical score of that protein. -Ranges from 0-10

High Protein Diets

-Protein consumption should not exceed 35% of energy intake -High protein diets to not offer additional health benefits -High protein intake may increase health and disease risks. One area of concern is the effect of excess protein on kidneys. Kidneys responsible for excreting excess nitrogen as urea. -High protein diets may burden the kidney, additional water is needed to dilute and excrete urea, inadequate fluid can increase the risk of dehydration as the kidneys use body water to dispose of the urea. -High protein diet may increase urinary calcium loss and eventually lead to a loss of bone mass and an increased risk of osteoporosis.

Equilibrium

-Protein intake is equal to protein loss, adequate to prevent the use of protein for energy

Negative Protein/Nitrogen balance

-Protein intake is less than losses -Often develops due to eating inadequate proteins accompanied by a serious untreated illness or injury -Example is how individuals with AIDS synthesize proteins at similar rates to healthy people but breakdown protein at higher rates. Overtime the increase rates of protein breakdown results in wasting of lean body mass.

Protein Quality

-Rated by scientists based on protein's digestibility (amount of amino acids absorbed) and amino acid composition compared with a reference protein (like egg whites). -Plant digestibility is lower than Animals

Codon

-Specific sequence of 3 nucleotide units within DNA that codes particular amino acids needed for protein synthesis

Transcription and Translation of genetic information.

-Synthesis of bod proteins is determined through a process called gene expression -Gene expression begins when deoxyribonucleic acid (DNA) replicates, making an exact copy of the gene. Thus, each gene serves as a template to guide the duplication of genetic information carried by the DNA.

Gene expression

-Synthesis of body proteins is determined through this process

Kwashiokor

-Synthesis of protein for vital tissues drops below normal rates, eventually resulting in protein wasting and the development of a condition known as kwashiorkor.

Synthesis of Non-essential Amino Acids

-Synthesized through a process called transamination -Glutamic acid and several other amino acids also can lose an amino group without transferring it to another carbon skeleton. -^^^This process is called deamination. -The amino group in the form of ammonia is incorporated into the urea of the liver, transported via the bloodstream to the kidneys and secreted in the urine. Once an amino acid breaks down its amino-free carbon skeleton, the carbon skeleton can be used for energy or synthesized into other compounds such as glucose.

Protein Synthesis Location

-Takes place in the ribosome -Ribosome is located in the cytosol of the cell -Because DNA is in the nucleus, the DNA code used for the synthesis of a specific protein must be transferred from the nucleus to the cytosol to allow for such synthesis. -This transfer job is done by the messenger RNA (mRNA). To produce mRNA, the DNA unwinds from it supercoiled state. Enzymes read he code on the DNA and transcribe that code into a complimentary single-stranded mRNA molecule called the primary transcript. This process is called DNA transcription

Contributing to Acid-Base Balance

-The acid-base balance in the body is expressed in terms of pH, which reflects the concentration of hydrogen ions. A solution with high hydrogen ion concentration has a low pH and is therefore more acidic, whereas a solution with a low hydrogen ion concentration has a high pH and is more alkaline. -Proteins play an important role in regulating acid-base balance and body pH. For example, proteins located in cell membranes pump chemical ions into and out of cells. The ion concentrations that result from the pumping action help the blood slightly alkaline.

Maintaining Fluid Balance

-The blood proteins albumin and globulin are important in maintaining fluid balance between the blood and the surrounding tissue space.

Forming Glucose

-The body must maintain a fairly constant concentration of blood glucose to supply energy, especially for red blood cells, brain cells, and other nervous tissues that rely on glucose for energy -If carb intake is inadequate to maintain blood glucose levels, the liver (and kidneys to a lesser extent) is forced to make glucose from the amino acids present in body tissues. -When this occurs chronically, as in starvation, the conversion of amino acids into glucose results in the development of widespread muscle wasting in the body (cachexia).

Limiting Amino Acid

-The essential amino acid in smallest supply in a food or diet in relation to body needs is called this because it limits the amount of protein the body can synthesize.

Kwashiorkor

Condition occurring primarily in young children who have an existing disease and consume a marginal amount of energy and severely insufficient protein. It results in edema, poor growth, weakness, and an increased susceptibility to further infection and disease. -develops rapidly -Is a word from Ghana that means "the disease that the first child gets when the new child comes" -Diet change from mothers milk to foods low in protein like starchy roots and gruels result in Kwashiorkor -Presence of edema in a child who still has some subcutaneous fat is the hallmark of kwashiorkor -Diarrhea, listlessness, failure to grow and gain weight, infections, and withdrawal from the envrionment

Protein-energy malnutrition PEM

Condition resulting from insufficient amounts of energy and protein, which eventually result in body wasting and an increase susceptibility to infection and disease -Children fail to grow normally, and many develop diarrhea, infections and diseases and die early in life. -Occurs as either Marasmus or Kwashiorkor

Marasmus

Condition that results from a severe deficit of energy and protein, which causes extreme loss of fat stores, muscle mass, and body weight -develops slowly -Word means to "waste away" -Usually develops in infants who either are not breastfed or have stopped breastfeeding in the early months. Often, the weaning formula used is incorrectly prepared because of unsafe water and because the parents cannot afford sufficient infant formula for the child's needs. -Latter problem may lead parents to dilute the formula to provide more feeding, not realizing that this deprives the infant of essential calories, proteins, and other nutrients. -Needs large amounts of energy to recover. -Low energy leads to bad brain development in early years of life

Urea

Nitrogenous waste product of protein metabolism and the major source of nitrogen in the urine.