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Exam 2: Proteins
Terms in this set (63)
A protease that is secreted from the gastric cells and converted to its active form by HCl
-macronutrients found in each cell in the body
-All enzymes are made of proteins
-Some hormones are made of proteins
Excess dietary protein can NOT be stored
Composed of Amino Acids to make Peptides
-primary, secondary, tertiary, quaternary
Protein: Structure cont.
Four levels of structure:
: Amino acids are linked together to form a simple linear chain.
: Geometric shape of the protein that is folded and twisted
: Three-dimensional globular shape of the protein
: Two or more polypeptide chains bond together.
Which structure of proteins are unchanged by denaturing(unfolding)?
Primary (just a string of amino acids)
1) Transport substances throughout the body: transport proteins shuttle oxygen, waste products, lipids, some vitamins and sodium and potassium through the blood and cell membranes)
2) Contribute to a healthy immune system: antibodies are proteins that bind and neutralize pathogens that would harm the body.
3) Provide energy: 4 kcals/gram
4) Improve satiety and appetite control
Amino Acid structure
surrounded by a side chain
Unique side chain distinguishes the different types of amino acids
An active protein enzyme in the stomach that begins the chemical digestion of protein
A classification of protein enzymes that break peptide bonds linking amino acids together
Amino acids are linked together by these; created when the acid group of one amino acid is joined with the nitrogen-containing amine group of another amino acid through condensation
(Broken through Hydrolysis)
Essential vs Nonessential vs Conditionally Essential amino acids
: must be taken in through diet
: we can make
: their synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress.
A protein chain made up of 3 amino acids joined together by a peptide bond
A protein chain consisting of 10 to more than 100 amino acids joined together by peptide bonds
A protein chain made up of 2 amino acids joined together by a peptide bond
The strong acid that is produced in the stomach and denatures proteins (and converts some proteases to their active form)
The process in which a protein's shape is altered; destroys the protein's function without disrupting the peptide bonds
Types of Cells involved in digestion
1. Mucosa (surface and neck) cell
2. Parietal cell
3. (Gastric) Chief cell
4. G cell
Enzymes/hormones secreted by Stomach
Pepsinogen, HCl, Gastrin
Enzymes/hormones secreted by Pancreas
Trypsin, Chymotrypsin, Carboxypeptidase
Enzymes/hormones secreted by Small Intestine
Aminopeptidase, Dipeptidase, Tripeptidase
Dipeptidase and Aminopeptidase
Enzymes secreted by the brush border in the small intestine that breaks down small peptides into amino acids
A component of gastric juice, that helps create the environment that pepsin needs to break down protein in the stomach; secreted from parietal cells
The hormone that stimulates secretion of gastric juices and contraction by the stomach
The main protease secreted by the pancreas; trypsin is activated (from trypsinogen) by enterokinase, and subsequently activates other pancreatic enzymes; specific for proteins
One of the main pancreatic proteases; it is activated (from chymotrypsinogen) by trypsin to degrade proteins into small polypeptides
Made in the pancreas and secreted into the small intestine. Hydrolyzes the first peptide bond at the carboxyl terminus of proteins and peptides; cleaves proteins into smaller amino acids
Overall Protein Digestion
1. Protein-rich foods are masticated and mixed with salivary juices (first digested in stomach)
2. Bolus enters stomach, where gastrin is released, which stimulates secretion of HCl and pepsinogen.
3. HCl denatures proteins and activates pepsinogen to pepsin, which breaks up polypeptides into smaller polypeptides
4. Chyme enters small intestine
5. Pancrease releases proteases into small intestine; along with enzymes produced by the small intestine, theses hydrolyze polypeptides to yield single amino acids, tripeptides, and dipeptides.
5. Dipeptides and tripeptides are broken down by dipeptidases and tripeptidases; amino acids are absorbed into enterocytes
6. Single amino acids in the enterocytes pool and then are absorbed into capillaries
How does the body use the protein once it has been ingested?
If calorie intake is inadequate, amino acids can be used for production of energy and the liver uses amino acids to create glucose
The body can synthesize_____ from amino acids
_________ is a common blood disorder that involves abnormal or flawed protein formation.
T or F: Excess dietary protein can be stored in the body
Contribution to Amino Acid Pool by:
1. Protein turnover
2. Intake of dietary protein
3. Synthesis of non-essential amino acids and Gluconeogenesis
In order to be used for fuel or stored as fat, surplus amino acids must undergo_____
The removal of the amine group from an amino acid to produce ammonia.
the continuous balance of protein synthesis and degradation; breakdown and synthesis of body proteins involving the recycling of amino acids
Which of the following proteins is most critical for maintaining fluid balance in the body?
Albumin (plasma protein)
Protein Demands in relation to Nitrogen Balance
-Healthy adults should be in nitrogen balance.
-Should consume enough to replace what is used every day
Positive nitrogen balance
-people recovering from surgery or injury
-Should consume enough to build new tissue
Negative nitrogen balance
-Immediately after surgery
-fighting an infection, or severe emotional trauma
-Need to consume enough kilocalories and protein to meet demand
Which of the following individuals are typically in nitrogen balance?
Nitrogen Balance = Total protein intake (grams)/6.25 - (UUN + 4 grams)
6.25=6.25 grams of protein per gram of nitrogen, UUN=grams of nitrogen excreted in the urine over a 24 hour period of time
4=4 grams of nitrogen lost each day as "insensible losses" via the skin and gastrointestinal tract
EX: Taylor consumed 63g of protein. She was told her UNN (urinary urea nitrogen) loss was 9 g.
Nitrogen balance= (63/6.25) - (9+4)=10.08-13=-2.92
The amino acid score takes into account the composition of a protein's_____
Essential amino acids compared to a standard
Finding an Individual's Daily Protein Requirements:
1. Take weight in pounds and convert into kilograms (divide by 2.2 lbs)
2. Multiply weight (kg) by 0/8 g of protein/kg
EX) 136lb healthy female Sarah; 32 years old
136 lbs/2.2lbs=61.8 kg...61.8kg X 0.8g= 49.4 g of daily requirement
How does pregnancy effect daily protein requirements?
Pregnant women need about 70-100 g of protein when pregnant (so Sarah above would need 19 more grams of protein to reach minimum of 70)
What group in an amino acid (amine group, acid group, or side group) gives the amino acid its unique qualities?
The side group of an amino acid provides it with its unique qualities
The role of high-protein diets in several disease states is still unclear, but it is thought that __________ from high-protein diets may contribute to conditions such as osteoporosis and kidney stones.
increased saturated fat intake
T or F: A high-protein diet may increase the risk of heart disease and kidney stones.
Fed state-release insulin and drive anabolic reactions
Fasted state- glucagon drives catabolic reactions
Metabolism in Chemical Reactions
Too much or too little protein?
Too much protein
-May increase risk for heart disease, kidney stones, and osteoporosis
-High intake of protein sources with high saturated fat
Too little protein
-bone loss in elderly men and women
-PEM (protein-energy malnutrition)
Inadequate protein intake effects
-Cells lining the GI tract are not sufficiently replaced as they slough off.
-Digestive function is inhibited.
-Absorption of food is reduced.
-Intestinal bacteria get into the blood and cause septicemia.
-The immune system is compromised due to malnutrition and cannot fight infection.
the rate at and the extent to which a nutrient is absorbed and used.
digestive hormone that causes the liver to increase its production of bile and the gallbladder to release stored bile
A hormone secreted by the small intestine (duodenum) in response to low pH (e.g., from stomach acid). It promotes the release of bicarbonate from the pancreas to act as a buffer.
Complete Protein VS Incomplete Protein
: "whole protein"; a source of protein that contains an adequate proportion of all nine of the essential amino acids necessary for the dietary needs of humans or other animals
EX) animal products (meat, dairy, eggs)
: The plant-based foods—legumes, whole grains, nuts, seeds, fruits, and vegetables—also contain all the essential amino acids. However, they have a low amount in one or more of these amino acids
process of combing proteins from different sources so that they collectively provide the proportions of amino acids required to meet needs
EX) rice and beans
Swelling of body tissues due to an excessive accumulation of fluid in connective tissue or a serous cavity
Glucogenic amino acids
-amino acids that can be converted into glucose through gluconeogenesis
-ALL but Leucine and Lysine
the formation of glucose from noncarbohydrate sources, such as amino acids
Limiting amino acid
The amino acid present in the smallest amount, relative to the amount received for growth, is called the:
A rare change in the DNA of a gene, ultimately creating genetic diversity.
-A human metabolic disease caused by a mutation in a gene coding for a phenylalanine processing enzyme (phenylalanine hydroxylase), which leads to accumulation of phenylalanine and mental retardation if not treated; inherited as an autosomal recessive phenotype.
process where the DNA sequence in a gene is copied into mRNA
mRNA VS tRNA
-DNA is copied so the message can be sent to the ribosomes
-RNA picks up amino acids and brings them to the ribosomes
the process where genetic information coded in messenger RNA directs the formation of a specific protein at a ribosome in the cytoplasm
-A chemical that comes from the breakdown of proteins
-A soluble nitrogenous waste produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide.
Recommended textbook explanations
Chemistry: The Central Science
Bruce Edward Bursten, Catherine J. Murphy, H. Eugene Lemay, Matthew E. Stoltzfus, Patrick Woodward, Theodore Brown
Matta, Staley, Waterman, Wilbraham
Glencoe Physical Science
McLaughlin, Thompson, Zike
Davis, Frey, Sarquis, J., Sarquis, M.
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