Introduction to Nutrition: Chapter 7
Protein synthesis
- DNA unwinds exposing a gene - gene undergoes transcription, forming messenger RNA - mRNA transfers info from the nucleus to ribosomes - ribosomes "read" the messenger RNA - RNA molecule conveys a particular amino acid to the ribosome - at the ribosome, the amino acid attaches to the peptide chain
Polypeptide
- Comprised of 50 or more amino acids - most naturally occurring proteins
Essential amino acid
Protein synthesis in cells cannot proceed when one or more ______________ is unavailable
Edema
accumulation of fluid in tissues
nonessential amino acids
amino acids that the body can synthesize
Symptoms of food allegries
- Swollen, itchy lips - difficulty swallowing - scaly rashly skin
Major functions of proteins in the body:
- build new cells and functional components of cells - component of structures such as hair and nails - enzymes to speed chemical reactions - lubricates to ease movement - clots compounds in blood - builds antibodies that fight disease - help maintain fluid and pH balance - transporter - makes certain hormones -energy source
Proteins
- chemically similar to lipids and carbohydrates because they contain carbon, hydrogen, and oxygen - also contain nitrogen • skin, blood, nerve, bone, and all cells contain this
high quality or complete protein
- contains all 9 essential amino acids - well digested and absorbed by the body • meat, fish, poultry, eggs, and milk
Treatment of children with PEM:
- hospitalization - frequent health assessments - carefully controlled refeedings
Vegetarian diet
- lower risk of diabetes, obesity, hypertension, and certain cancers - provide more fiber, photo chemicals, folic acid, vitamins E and C, potassium and magnesium - supplies less saturated fat
Personalized nutrition
- making dietary choices based on one's genetic makeup
acid-base balance
- proteins help maintain this - proper pH of body fluids
celiac disease
Autoimmune disorder that results in poor absorption of nutrients in the small intestine • cannot tolerate gluten
quarternary structure of protein
2 or more proteins joined to form a functional unit
0.8g/kg
A healthy adult's RDA for protein is __________ of body weight
Biological Value (BV)
A measure of protein quality based on how well and how quickly the body converts food into body tissue proteins
Gluten
A protein in wheat, barley, and other cereal grains
Urinary elimination of urea and creatinine
Accounts for most of nitrogen loss
protein-energy malnutrition (PEM)
Affects people whose diets lack sufficient protein and energy
Liver
After being absorbed, amino acids enter the hepatic portal vein and travel to the ________
essential amino acids
Amino acids that are needed, but cannot be made by the body; they must be supplied by food
Nitrogen
An element cells need to make a wide array of important biological compounds such as enzymes and hormones
conditionally essential amino acids
Become essential under certain conditions
Buffer
Can protect the pH of a solution
gluten sensitivity
Compared to celiac disease, people with gluten sensitivity do not have damage to the small intestine
peptide bond
Connection between amino acids
Peptides
Contain 2 or more amino acids
Protein Efficiency Ratio (PER)
Determined by measuring the weight gain of a growing lab animal that consumes a known amount of protein
Poor growth, slow recovery, and death
Diets that do not supply adequate amounts of essential amino acids can result in:
amino or nitrogen-containing group, R group, and carboxylic acid group
Each amino acid has a carbon atom that anchors a hydrogen atom and three different groups of atoms:
Amino acids
End product of protein digestion
Nitrogen, nitrogen, lost
Even though the body conserves ____________ by recycling amino acids, each day some protein and ___________ are lost
Proteins
Every organism synthesizes __________ that are unique to that specific organism
Small intestinal cells
Final digestion occurs within absorptive _____________
Amino acids
Following digestion, _______________ are transported by specific carrier systems into the absorptive cells
10-35%
For healthy adults, the level of consumption of protein is _________ of energy from protein
Trypsin and chymotrypsin
Further digestion occurs as the pancreas secretes protein-splitting enzymes including __________ and ____________
Eggs
Has a pattern of essential amino acids that closely resembles that used by humans
Food intolerance
Having a headache and intestinal discomfort from eating a food, without triggering the body's immune response
Genes
Hereditary material in a cell's nucleus
Pepsin
Initiates enzymatic digestion of proteins into smaller polypeptides
low quality or incomplete protein
Lacks adequate amounts of one or more of the essential acids
nutritional genomics
May explain why dietary interventions can have different effects on the health of different individuals
Protein digestibility corrected amino acid score (PDCAAS)
Most widely used measure of protein quality Derived by multiplying a foods chemical score by its digestibility.
Transamination
Occurs when the nitrogen-containing group is transferred to another substance to make a nonessential amino acid
Legumes
Plants with seed pods • peas, peanuts, lentils, soybeans
Fruit
________ is not a good source of protein
Stomach acid, pepsin
Proteins undergo denaturation by ______________ and partial digestion by __________
tertiary structure of protein
Refers to the proteins final three-dimensional form
Function
The shape of a protein influences the compounds ___________ in the body
Protein
___________ needs to increase during pregnancy, breastfeeding, periods of rapid growth, and recovery from illnesses, blood loss and burns
Multiply, 0.8g
To determine a person's RDA for protein, ______________ his or her weight by ________
20, DNA
To make proteins, cells assemble the _____ amino acids in specific sequences according to the information provided by ________
Dipeptide
Two amino acids bonded together and a molecule of water is released in the process
digestibility and amino acid composition
Two key factors in determining the quality of a protein:
Feces
Very little dietary protein is excreted in _________
Denaturation
When a protein is exposed to various conditions that alter its natural folded and coiled shape
negative nitrogen balance
When the body loses more nitrogen than it retains • occurs during starvation, serious illness, and severe injuries
Heat
________ causes proteins in food to undold
primary structure of protein
linear sequence of amino acids linked by peptide bonds
Casein
milk protein
Complimentary combinations
mixing certain plant foods to provide all essential amino acids without adding animal protein
secondary structure of protein
protein structure is formed by folding and twisting of amino acid chain
Amino acids
what proteins are made of