Nutrition - Reviews all chapters

• Protein


  Made of the elements carbon, hydrogen, oxygen, and nitrogen. Some contain sulfur. These elements form amino acids, the building blocks for protein synthesis.
• Amino acids


  Supplied by protein-containing foods and cell synthesis. Composed of a central carbon, nitrogen (amino) group, acid (carboxyl) group, hydrogen, and side chain (R) which determines structure, function, and name.
• Amino acids


  • 20 amino acids needed by the body
  • 11 nonessential (dispensable) amino acids that the body can synthesize
  • 9 essential (indispensable) amino acids that must be obtained from food
• Nonessential amino acids


  May be classified as "conditionally essential" during infancy, disease, or trauma when the body cannot synthesize them fast enough to meet needs
• Synthesis of nonessential amino acids

  Through transamination (transferring amino group to carbon skeleton) and deamination (amino group incorporated into urea and excreted)
• Complete (high quality) proteins

  Animal proteins (except gelatin) that contain all 9 essential amino acids
• Incomplete (low quality) proteins


  Plant proteins (except quinoa and soy) that do not contain all 9 essential amino acids and are low in 1 or more
• Limiting amino acid


  The essential amino acid in smallest supply that limits the amount of protein the body can make
• Complementary proteins


  Two or more plant proteins that can be combined to compensate for deficiencies in essential amino acids
• Synthesis of proteins


  Amino acids linked together by peptide bonds to form proteins (dipeptides, tripeptides, oligopeptides, polypeptides)
• Transcription and translation


  1. DNA transcription phase: DNA code transferred to cytosol via messenger RNA (mRNA)

  2. mRNA translation phase: tRNA and ribosomes use DNA-coded instructions (codons) to determine shape and function of proteins
• Primary structure


  Sequential order of amino acids that determines the protein's shape
• Secondary structure


  Spiral-like or pleated sheet shape formed by weak chemical bonds between amino acids
• Tertiary structure


  1. dimensional folding that determines overall shape and function of protein
• Quaternary structure


  Two or more separate polypeptides interacting
• Denaturation


  Alteration of a protein's 3-dimensional structure that destroys its function, caused by exposure to acid, alkaline, enzymes, heat, or agitation
• Bomb Calorimeter


  The calorimeter used to determine the energy change during a reaction accurately
• Body proteins are in a constant state of breakdown, rebuilding, and repair (protein turnover) which allows cells to adapt to changing circumstances
• Sources of protein


  • Dietary proteins
  • Recycling of amino acids released during breakdown of body proteins
• Typical North American diet: 70% of proteins come from meat, poultry, fish, milk, cheese, legumes, and nuts. Typical worldwide diet: 35% of protein comes from animal sources. Plants are a major source of protein.
• Plants can provide protein as well as fiber, vitamins, minerals, phytochemicals, and other benefits like lower cholesterol and saturated fat
• Prader-Willi syndrome (PWS)


  A complex, multisystem disorder characterized by neonatal hypotonia with poor suck and poor weight gain without nutritional support, developmental delay, mild cognitive impairment, hypogonadism leading to genital hypoplasia and pubertal insufficiency, short stature if untreated with growth hormone (GH), childhood-onset obesity if excessive eating is not limited, behavioral findings, and typically a characteristic facial appearance
• Biological value (BV)


  Measure of how efficiently the absorbed food protein is converted into body tissue protein
• Prader-Willi syndrome


  A rare genetic disorder that results in a number of physical, mental and behavioral problems. A key feature is a constant sense of hunger that usually begins at about 2 years of age
• Protein efficiency ratio (PER)

  Compares the amount of weight gain of a laboratory animal consuming the protein being studied against the weight gain of a laboratory animal consuming a reference protein
• Prader-Willi syndrome


  • People with Prader-Willi syndrome want to eat constantly because they never feel full (hyperphagia), and they usually have trouble controlling their weight. Many complications are due to obesity
• Chemical score


  Calculated by taking the amount of each essential amino acid in a gram of food protein being tested divided by the "ideal" amount for the amino acids in a gram of reference protein
• Protein Digestibility Corrected Amino Acid Score (PDCAAS)

  Most widely used method, calculated by multiplying a food's chemical score by its digestibility
• Prader-Willi syndrome


  • Characterized by weak muscle tone (hypotonia), feeding difficulties, poor growth, and delayed development in infancy. Affected individuals develop an extreme hunger, which leads to chronic overeating (hyperphagia) and obesity in childhood
• Nitrogen balance


  If protein intake equals losses, protein balance (equilibrium) is maintained. If intake is less than losses, individual is in negative protein (nitrogen) balance. If intake is greater than losses, individual is in positive protein (nitrogen) balance.
• Prader-Willi syndrome


  • People with Prader-Willi syndrome typically have mild to moderate intellectual impairment and learning disabilities. Behavioral problems are common, including temper outbursts, stubbornness, and compulsive behavior such as picking at the skin. Sleep abnormalities can also occur
• Adult RDA for protein is 0.8 g/kg of body weight. During recovery from illness/injury and for highly trained athletes, protein needs can range from 0.8 to 2.0 g/kg.
• Protein digestion and absorption

  1. Cooking denatures proteins and softens connective tissue

  2. In stomach, hydrochloric acid denatures proteins and pepsin breaks down polypeptides

  3. In small intestine, secretin and cholecystokinin stimulate pancreas to release proteases that complete digestion

  4. Short peptides and amino acids are actively absorbed, with amino acids going to liver via portal vein
• Prader-Willi syndrome


  • Distinctive facial features such as a narrow forehead, almond-shaped eyes, and a triangular mouth; short stature; and small hands and feet. Some have unusually fair skin and light-colored hair. Both affected males and affected females have underdeveloped genitals. Puberty is delayed or incomplete, and most are unable to have children (infertile)
• In early infancy, the GI tract is permeable to small proteins which may predispose infants to food allergies, so common allergenic foods are advised to be introduced at 4-6 months or older
• Protein functions include synthesis, energy needs, conversion to carbohydrate or fat, and release into bloodstream
• Ozempic


  A weekly injection that helps lower blood sugar by helping the pancreas make more insulin. It is not approved for weight loss, but some physicians prescribe it to be used for weight loss
• Ozempic


  • Works by mimicking a naturally occurring hormone. As those hormone levels rise, the molecules go to the brain, telling it you're full. It also slows digestion by increasing the time it takes for food to leave the body
• gastrin


  Gastrin also stimulates parietal cells to produce acids
• Protein Digestion and Absorption

  1. Chyme entering the small intestine triggers the release of secretin and cholecystokinin (CCK)

  2. Hormones that stimulate the pancreas to release proteases

  3. Trypsin, chymotrypsin, carboxypeptidase complete the digestion of polypeptides in small intestine

  4. Short peptides and amino acids are actively absorbed

  5. In absorptive cells, short peptides further digested by peptidases travel to the liver via the portal vein