Digestion and Absorption of Nutrients Flashcards by Marcos J Collazo Acevedo

The major routes of absorption for glucose are:

SGLT-1, GLUT-5, and GLUT-2

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Collectively the microvillous regions constitute the ___________.

Brush border

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Final breakdown of carbohydrates, proteins and fats occur in:

Small Intestine

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Is most commonly caused by deficiencies in carbohydrate-splitting enzymes in the intestinal brush border

Diarrhea caused by the poor assimilation of dietary carbohydrates

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Peptide bonds are hydrolyzed by: ____________

Peptidases

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Cleaves proteins at hydrophobic amino acids

Elastase

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Luminal digestion of starch begins in mouth with the action of: ______________

Salivary α-amylase

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Cellulase

Enzyme not present in human GI tract that is capable of digest the B-glucose bonds of cellulose and hemicellulose

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Sercete enzymes in pancreas

Exocrine cells

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Most nutrients are absorbed in: _____________

Ileum

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High-molecular-weight polysaccharide similar to amylopectin in molecular structure but having considerably more 1,6- linkages

Glycogen

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Is nonexistent because pancreatic amylase is secreted in tremendous excess.

Maldigestion of starch in humans

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GI Physiology can be affected by:

Starvation, irradiation, and the loss of a portion of the bowel.

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Exits the basolateral membrane by another facilitated diffusion, involving the GLUT-2 transporter.

Fructose

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Acid secretion is stimulated by __________ and accompanied by morphologic changes in __________.

Extracellular Signals, Parietal Cells

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Is the most frequently observed congenital disaccharidase deficiency and can exist in the absence of any other intestinal malfunction.

Lactase Deficiency

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Solubilization is aided by the release of bile salts from the gallbladder, this process is stimulated by:

Cholecystokinin

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The H + transported by the proton pump are supplied by:

Carbonic Anhydrase

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Glucose and chemically related sugars are absorbed by: ______________

Na+ dependent secondary active transport process

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Similar to amylose but in addition to α-1,4- linkages there is a α-1,6-linkage for every 20 to 30 glucose units.

Amylopectin

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Final digestion of oligopeptides and dipeptides is carried out in the small intestine by:

Endopeptidases, Dipeptidases, and Aminopeptidases

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Polysaccharides and oligosaccharides are absorbed as:

Polysaccharides

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Who secrete enzyme in mouth?

Glandular Cells

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Cimetidine or Ranitidine

H2 antagonist (prevent histamine release)

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Cleaves proteins at aromatic amino acids

Chymotrypsin

The only products of sugar digestion are:

Glucose, Galactose, and Fructose

What happened to di and tripeptides within the enterocytes?

Are hydrolyzed to their constituent amino acids

Bile salts and pancreatic enzymes act on the lipid emulsion that take place in the:

Duodenum

Describe 2nd step of digestion

Secretion of enzymes that break down macromolecules to a mixture of oligomers, dimers, and monomers.

All lactose is broken down into glucose and galactose by

Lactase

Produces mainly 2-monoacyl glycerols (2- MAG), which are absorbed into enterocytes.

Pancreatic Lipase

Is approximately 50% of the calories ingested

Daily Intake of Carbs

In these cases the patients show no symptoms when they are fed fructose

Intolerance to glucose and galactose

Are associated with inflammation in the small bowel mucosa. These conditions are often attended by brush border enzyme deficiencies.

Celiac disease, certain bacterial infections, and some protozoan and helminth infections

Break down large polypeptides into smaller oligopeptides

Endopeptidases

Protects the stomach from the effects of the strong acid.

Alkaline Mucus secreted by epithelial cells

Who secrete enzymes in stomach?

Chief Cells

Covalently modifies cysteine residues located in the extracytoplasmic domain of the α- subunit and inhibits the proton pump, blocking H secretion

Omeoprazole

Cells that made digestion, | absorption, and secretion

Enterocytes

Secrete lysozymes and defensins that destroy bacteria or produce inflammatory responses.

Paneth Cells

The absorptive processes start in: ___________

The Jejunum

Is activated to pepsin in the acidic environment of the stomach lumen.

Pepsinogen

Is a disaccharide consisting of glucose and fructose

Sucrose

Acts on H2 receptors and is activated by gastrin

Histamine

Digestion and absorption of essentially all major dietary products take place in ______

Small Intestine

Describe 1st step of digestion

Lubrication and homogenization of food with fluids secreted by glands of the intestinal tract.

Osmotic retention of water in the lumen leads to:

Diarrhea, bloating, and abdominal pain

Describe 3rd step of digestion

Secretion of hydrogen ion and bicarbonate within different parts of the GI tract to optimize the conditions for enzymic hydrolysis.

During periods of health the principal substances absorbed from the colon are:

Water and Electrolytes

Facilitates absorption of vitamin B 12 in the intestine .

Intrinsic factor (IF) secreted by parietal cells

In humans, the time needed to replace the entire population of intestinal epithelial cells is:

3 to 6 days

Where is absorbed medium and short chain FA?

Are absorbed into the portal blood

Remains inactive in the presence of bile salts normally secreted into the small intestine.

Pancreatic Lipase

Recycling of bile acids and absorption of the SCFAs produced by:

Colonic Bacteria

Is the site of activity for a number of digestive enzymes, it is also the barrier that must be traversed by nutrients, water, and electrolytes on the way to the blood or lymph.

Brush Border

The H + secretion is dependent on: ________

The parallel export of K + through luminal K + channels

Triggers the release of the main digestive enzymes by the pancreas as well as the contraction of the gallbladder to release bile.

Cholecystokinin in pancreatic phase of digestion

Responsible for the exit of glucose and galactose from the absorbing cell

GLUT-2

Cells that secrete mucus

Goblet Cells

Comprises approximately 30% of the total carbs intake

Sucrose

Are synthesized as inactive zymogens and are only activated on their release to the gut lumen

Enzymes involved in the digestion of protein (proteases)

Enzymes in mouth

Amilasa and Lingual Lipase

Consists of cholesterol, cholesteryl esters, phospholipids, and nonesterified fatty acids (NEFA).

Tryacyglycerols

Wich Enzyme is responsible for active Pancreatic Lipase?

Colipase | -Binds to both the water􏰋lipid interface and the pancreatic lipase, activating the enzyme.

Secrete pepsinogen, which is a precursor of pepsin

Chief Cells

Enzymes secreted by small intestine:

Enterokinase, Disaccharides, Maltase, Sucrase, Lactase, Trehalase, Isomaltase, Peptidase, Dipeptidase

Luminal digestion of starch ends in small intestine with the action of: ______________

Pancreatic a-amilase

Cleaves proteins at arginine and lysine residues

Trypsin

____________ are transferred to the rough endoplasmic reticulum for resynthesis into TGs by a FA binding protein

Greater than 12 carbons FA

Major enzyme secreted by the pancreas

Pancreatic Lipase

Enzymes of stomach

Pepsin and Gastric Lipase

Remove amino acids from the carboxy terminus of the polypeptide

Carboxypeptidase

Is the most active enzyme, but sucrase and isomaltase also cleave these bonds

Glucoamylase

Parietal cell activity is stimulated by the action of: ___________

Histamine

Describe the protein digestion in the stomach.

1. The HCl reduces the pH to 1-􏰋2, with consequent denaturation of dietary proteins 2. Denaturation unfolds polypeptide chains, making proteins more accessible to proteases 3. Chief cells of gastric mucosa secrete pepsin

Human salivary and pancreatic amylases have optimum activities near ______ pH and are activated by _________.

Neutral, Cl

Cleaves 100% of sucrose to yield glucose and fructose.

Sucrase

Is a high-molecular-weight compound consisting of two polysaccharides, amylose and amylopectin

Starch

Remove amino acids from amino terminus

Aminopeptidases

Mixing of food and initiation of digestion take place in: ____________

The mouth and stomach

Transport the lipids to the brush border of the enterocyte

Micelles

Enzyme secreted by pancreas

Amylase, Trypsin, Chymotripsin, Carboxypeptidase, Elastase, etc

Secreted bile salts pass into the ileum, where they are reabsorbed and transferred back to the liver through the:________________

Enterohepatic Circulation

In this patients the SGLT-1 transporter is absent, whereas GLUT-5 is present

Patients with intolerance to glucose and galactose

Is secreted by G cells and is triggered by food entering the stomach

Gastrin

Is a rare disease found primarily in children.

Intolerance of sucrose and Isomaltose

Treatment of acid-related symptoms, such as dyspepsia or gastroesophageal reflux, can be achieved with:

Antiacids, H2 antagonist or proton pump inhibitors

Act as detergents and reversibly form lipid aggregates, micelles

Bile Acids

Antiacids function

Neutralize PH

What happened in the final step of digestion of peptides?

The transfer of free amino acids out of the enterocyte into the portal blood

Cell proliferation, differentiation, and maturation are influenced by:

GI hormones, growth factors, and the nature of the material in the lumen.

Is involved in the absorption of water and electrolytes and participates in the recirculation of the bile acids to the liver.

Large Intestine

Comprises approximately 1% of the total carbs intake

Maltose

Comprises approximately 50% of the total carbs intake

Starch

Is a straight-chain polymer of glucose linked by α-1,4-glycosidic bonds

Amylose

Hydrolysis of oligomers and dimers is mediated by:

Membrane-bound enzymes.

The end product of digestion of peptides are:

Free amino acids and di- and tripeptides.

Products of amylase action on starch and other major dietary sugars are hydrolyzed by: _________

Brush Border Carbohydrases

Generate hydrogen ions through the action of carbonic anhydrase and then pump them into the lumen by an ATP-dependent proton pump on the luminal membrane.

Parietal Cells

Comprises approximately 6% of the total carbs intake

Lactose

Is the chemical breakdown of food by enzymes

Digestion

Emulsification of dietary lipids are mediated by:

Bile Acids

Converts trypsinogen to active trypsin

Duodenal Enteropeptidase

Uptake processes include:

Active and Passive Diffusion

Fructose is absorbed by:_____________

Na+ independent facilitated diffusion

Are absorbed by secondary active transport via an Na +- dependent carrier system (SGLT-1).

Glucose and Galactose

Control the flux of solutes and fluid between the lumen and blood

Enterocyte Membrane

Pass directly through the enterocytes into the hepatic portal system

Medium and Short Chain FA (>10)

Digestion and Absorption of Nutrients Flashcards

(108 cards)