Questions and Answers
Where does protein digestion begin?
Stomach
What happens to proteins in the stomach?
They are cut into short segments.
What are proteins called after they have been cut into segments?
Peptides
What enzyme cuts the proteins?
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Is pepsin the active or inactive form of the enzyme?
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What is the inactive form of pepsin?
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What activates pepsinogen?
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What cells secrete pepsinogen?
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What cells secrete HCl?
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What happens to peptides after the stomach?
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Where are peptides broken down into amino acids?
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What is the name for the enzyme group that breaks down peptides into amino acids?
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What are a few examples of proteases?
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What is the main source for all of our digestive enzymes (including proteases)?
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What happens to amino acids after the small intestine?
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How does the absorption of amino acids into the mucosal cells happen?
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How does co-transport work?
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Why does taking extra supplemental protein in an attempt to build muscle not work very well?
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What happens to amino acids after the mucosal cell?
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What is facilitated diffusion?
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Why does this make sense that the amino acids would use facilitated diffusion to pass into the bloodstream?
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What major blood vessel will this blood be in?
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Where will the proteins in this blood go next?
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What does the liver generally do to blood that has just arrived from the digestive tract?
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What does the liver do with amino acids?
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What types of proteins does the liver manufacture from amino acids?
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Does the liver use all of the amino acids to make proteins?
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What happens to the amino acids that remain in the bloodstream?
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What does the muscle do with amino acids?
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Is protein ever used for energy?
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What will the brain do with amino acids?
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What will adipose tissue do with amino acids?
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Study Notes
Protein Digestion Process
- Protein digestion begins in the stomach.
- In the stomach, proteins are cut into short segments known as peptides.
- The enzyme responsible for cutting proteins in the stomach is pepsin, which is in its active form.
- Pepsinogen is the inactive precursor that activates into pepsin when exposed to hydrochloric acid (HCl), also known as stomach acid.
- Chief cells secrete pepsinogen, while parietal cells secrete hydrochloric acid.
Peptide Breakdown and Enzyme Functionality
- After leaving the stomach, peptides are further broken down into amino acids in the small intestine.
- Proteases are the enzyme group that accomplishes the breakdown of peptides into amino acids, including examples like trypsin and carboxypeptidase.
- The pancreas is the main source of digestive enzymes, including proteases.
Amino Acid Absorption
- Amino acids are absorbed into the mucosal cells of the small intestine.
- This absorption occurs via co-transport with a sodium (Na+) protein carrier that utilizes a chemical gradient.
- Co-transport leverages the sodium gradient, allowing other molecules to move alongside sodium ions.
Impact of Supplementing Protein
- Excess supplemental protein can overwhelm the protein carriers, leading to reduced absorption of amino acids.
- After entering the mucosal cells, amino acids are transported into the bloodstream through facilitated diffusion.
- Facilitated diffusion occurs as amino acids move along their natural gradient via carrier molecules.
Bloodstream Pathway and Liver Processing
- Absorbed amino acids enter the hepatic portal vein, directing blood to the liver.
- Upon arrival, the liver modifies, filters, and normalizes the nutrient concentrations in the blood.
- The liver utilizes amino acids primarily to synthesize proteins, specifically plasma proteins.
- Not all amino acids are used by the liver; some remain in the bloodstream for distribution.
Utilization of Amino Acids
- Remaining amino acids travel to sites such as muscles, the brain, and adipose tissue.
- Muscle tissue uses amino acids to synthesize actin, myosin, and enzymes but does not utilize them directly for energy.
- Proteins are not used directly for energy; they must first be converted into carbohydrates.
- The brain uses amino acids to produce enzymes, receptors, channels, and carriers for metabolic processes.
- Adipose tissue converts amino acids into enzymes that synthesize fat.
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Description
Test your knowledge on the steps of protein digestion and absorption with these flashcards. Learn about where protein digestion begins, the role of enzymes like pepsin, and the transformation of proteins into peptides. Perfect for students studying biology and nutrition.
