When you drink a cup of milk, what happens to the protein in the milk after it has been swallowed? To describe these processes, you must be able to use the vocabulary effectively.
Match the words in the left column to the appropriate blanks in the sentences on the right.
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polypeptides
denaturation
proteases
gastrin
portal vein
amino acids
tripeptide
dipeptide
hydrochloric acid
pepsin
1. is the active form of the digestive enzyme pepsinogen.
2. Cleavage of proteins by pepsin in the stomach results in formation of shorter , which get broken down further in the small intestine.
3. An amino acid chain made up of three amino acids joined together is called a .
4. describes an amino acid chain made up of two amino acids joined together.
5. The 20 different are the building blocks used for protein synthesis.
6. The stomach produces , which denatures protein.
7. occurs when a protein is exposed to heat, acid, bases, or mechanical agitation resulting in unfolding of the protein, though the peptide bonds remain intact.
8. Single amino acids that are absorbed in the small intestine travel to the liver via the .
9. is a hormone that controls the release of pepsin and the production of hydrochloric acid.
10. Protein is digested in the small intestine by enzymes called .
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Part B - Digestion and Absorption of Proteins
Part complete
In this activity, you will sort each phrase regarding protein digestion and absorption according to the organ in which the function takes place.
Drag the appropriate items to their respective bins.
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Amino acids that enter the
bloodstream from the small
intestine travel to here. Selected
Mouth
Food containing protein
is crushed and moistened here.
Stomach
Pepsin is formed from
pepsinogen here.Hydrochloric acid denatures
protein here.
Small Intestine
Single amino acids,
dipeptides, and tripeptides
are absorbed here.
Pancreas
Proteases are produced here
and delivered via a duct to
the small intestine.
Liver
Amino acids can be converted
into glucose here.Amino acids that enter the
bloodstream from the small
intestine travel to here.
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The body does not directly use intact proteins in food to create the proteins it needs. Instead, the proteins are broken down into amino acids, which are then absorbed and transported to cells.
Part C - The Process of Protein Digestion
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How does protein in a peanut butter sandwich become amino acids that the body can use? Think about the digestive and absorptive process from taking the first bite of that sandwich to the amino acids’ entering the circulatory system. Focus your attention on the steps involved in protein digestion illustrated in the focus figure.
Rank the labels in the correct order from the first bite to the amino acids entering the circulatory system.
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Amino acids entering the circulatory system
Taking a bite of a peanut butter sandwich
Taking a bite of a peanut butter sandwich Background Image
Food containing
protein is crushed
and moistened
with saliva.
Background Image
Background Image
Proteins are
denatured by
hydrochloric acid,
and pepsinogen
is activated.
Background Image
Background Image
Pepsin breaks
down proteins
into single amino
acids and
polypeptides.
Background Image
Background Image
Proteases from
the pancreas
are secreted
into the small
intestine.
Background Image
Background Image
Proteases
break down
polypeptides
into mostly
tripeptides and
dipeptides.
Background Image
Background Image
Tripeptides and
dipeptides are
broken down
into single
amino acids.
Background Image
Amino acids entering the circulatory system Background Image
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The sequence of events involving the digestion and absorption of protein after ingesting food is complex; in summary, large and complex proteins molecules are denatured, the resulting polypeptides are broken down, and, finally, amino acids enter the circulatory system.
Part D - Protein Use in the Body
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How does your body use the protein once it has been ingested? Consider the following statements and select the correct ones regarding protein use.
Select all that apply.
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Select all that apply.
Amino acids are used to create new proteins.
If calorie intake is inadequate, amino acids can be used for production of energy.
If you ingest more protein than your body needs, the protein is stored in muscle.
The liver uses amino acids to create glucose.
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You have thought about the uses your body has for the protein you eat. Remember that protein can't be stored in the same way that fat can, but the amino acids contained in protein can be used for energy production, converted into glucose, or used for making proteins the body needs to function. Protein is also involved in fluid balance.
Part E - Essential versus Nonessential Amino Acids
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The body uses two types of amino acids: essential and nonessential. Which of the following statements about essential and nonessential amino acids is correct?
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The body uses two types of amino acids: essential and nonessential. Which of the following statements about essential and nonessential amino acids is correct?
There are 11 essential amino acids.
There are 11 nonessential amino acids.
The body can produce essential amino acids when the amino acid pools are diminished.
Nonessential amino acids cannot be produced in the body.
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In general, it is recommended that 10 to 35
%
of total calories come from protein. Using what you have learned regarding protein digestion, consider the following scenarios and questions:
Kwashiorkor is a disease that arises due to severe protein malnutrition. Symptoms include thinning hair (hair is made from the protein keratin), failure to produce antibodies (antibodies are proteins), muscle wasting (muscle fibers are made of proteins), in addition to many other symptoms.
A food that contains protein with all nine essential amino acids is called a complete protein. Meat, eggs, and dairy are examples of foods that are sources of complete proteins. Though very few plant sources are complete proteins by themselves, it is still relatively easy for vegans or vegetarians to get the essential amino acids they need by consuming a variety of plant sources of protein.
Patients suffering from severe wounds or injuries have an increased need for protein intake. Why might this be?
Gastric bypass surgery is a procedure where the majority of the stomach is separated from the digestive tract. A much smaller stomach “pouch” is left which connects the esophagus and small intestine. Patients that undergo some types of this surgery often have issues with protein malabsorption (they are not able to absorb very much of the proteins they eat). Can you think of reasons this might occur?
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Correct. Followup. In general, it is recommended that 10 to 35 of total calories come from protein. Using what you have learned regarding protein digestion, consider the following scenarios and questions:
Kwashiorkor is a disease that arises due to severe protein malnutrition. Symptoms include thinning hair (hair is made from the protein keratin), failure to produce antibodies (antibodies are proteins), muscle wasting (muscle fibers are made of proteins), in addition to many other symptoms.
A food that contains protein with all nine essential amino acids is called a complete protein. Meat, eggs, and dairy are examples of foods that are sources of complete proteins. Though very few plant sources are complete proteins by themselves, it is still relatively easy for vegans or vegetarians to get the essential amino acids they need by consuming a variety of plant sources of protein.
Patients suffering from severe wounds or injuries have an increased need for protein intake. Why might this be?
Gastric bypass surgery is a procedure where the majority of the stomach is separated from the digestive tract. A much smaller stomach “pouch” is left which connects the esophagus and small intestine. Patients that undergo some types of this surgery often have issues with protein malabsorption (they are not able to absorb very much of the proteins they eat). Can you think of reasons this might occur?
End of followup.
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