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Carb, Fat, Protein DIgestion/Absorption Flashcards

1
Q

Large food molecules (proteins, lipids, nucleic acids, starches) are broken down into subunits by _____ through what chemical process?

A

Enzymes through hydrolysis

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2
Q

Name the salivary enzymes, the substrate they breakdown, and their products

A

Lingual lipase breaks down triglycerides to free fatty acids and diglycerides

Salivary amylase breaks down polysaccharides to di and trisaccharides

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3
Q

Name the gastric enzymes, substrate they breakdown, and products of breakdown

A

Gastric lipase breaks down TGs to fatty acids and monoaclyglycerides

Pepsin breaks down proteins to peptides

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4
Q

A-Dextrinase - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

BB enzyme found in SI, breaks down a-Dextrins to glucose

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5
Q

Enteropeptidase - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

BB enzyme
Found in SI
Breaks down trypsingoen to trypsin

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6
Q

Lactase - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

BB enzyme
found in SI
Breaks down lactose to glucose and galactose

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7
Q

Maltase- what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

BB enzyme
SI
Breaks down maltose to 2 glucose molecules

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8
Q

Nucleosidases and phosphatases - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

BB enzymes
SI
Nucleotides to phosphates, nitrogenous bases, and pentoses

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9
Q

Sucrase - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

BB enzyme
SI
Sucrose to glucose and fructose

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10
Q

Carboxypeptidase- what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreas
Breaks down Amino acids at the carboxyl end of peptides to amino acids and peptides

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11
Q

Chymotrypsin - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreas
Proteins to peptides

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12
Q

Elastase - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreas
Proteins to peptides

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13
Q

Nucleases- what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreas
Breaks down ribonuclease (RNA), and deoxyribonuclease (DNA) to nucleotides

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14
Q

Pancreatic amylase- what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreatic cells
Polysaccharides (starches) to a-Dextrin and disaccharides

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15
Q

Pancreatic lipase - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreatic cells
Breaks down TGs that have been emulsified by bile salts, end product is fatty acids and monoglycerides

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16
Q

Trypsin - what type of enzyme, where is it found, what substrate does it breakdown and what does said substrate break down to?

A

Pancreatic enzyme
Pancreatic cells
Proteins to peptides

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17
Q

Cellulose - what is it and what enzymes break it down? Does it provide any nutritional value?

A

Fibrous polysaccharide that is indigestible.
No nutritional value but they do provide dietary fiber which helps propel food down the alimentary canal (AKA the digestive tract)

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18
Q

What is resistant starch and how is it digested?

A

Resistant starch is resistant to digestion in the SI, so it goes to the colon where it undergoes fermentation by the gut microbes to create SCFAs

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19
Q

Once starch is broken down to glucose molecules in the SI, where does the glucose go?

A

Glucose enters glucose/NA+ cotransporters on the apical surface of enterocyes where they are taken into the cell, and transported from the enterocytes to the bloodstream via GLUT2 transporters. Glucose then is used for energy by the tissues or stored as glycogen in the liver

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20
Q

Where does protein digestion start? How does it start? What cells in the stomach secrete enzymes and others that stimulate digestion?

A

Stomach
Chief cells secrete pepsinogen which is converted to active form pepsin by HCl. HCl is secreted by the parietal cells.

Pepsin breaks down protein into peptides

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21
Q

Once proteins are broken down into the stomach, what happens next? What enzymes are secreted from the pancreas to break down proteins further?

A

Goes to the small intestine (duodenum) which is where most of protein digestion takes place.

Trypsinogen (—> trypsin via enterkinase enzymes in enterocytes) hydrolyzes peptide bonds breaking protein to peptides

Chymotrypsinogen (—-> chymotrypsin via trypsin) hydrolyzes peptide bonds and breaks proteins —> peptides

Procarboxypeptidase (—> carboxypeptidase via trypsin) - hydrolyzes peptide bonds on the carboxyl end of amino acid chain

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22
Q

What brush border enzymes are secreted for protein digestion? When does this happen?

A

Depeptidases - breaks down di-peptides

Aminopeptidases - breaks down peptide bonds from the amino end of polypeptide into more di-, tri-, and singular amino acids to get ready for absorption

This happens after trypsin, chymotrypsin, and carboxypeptidase break down proteins —> peptides

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23
Q

___ ingested food, ___% electrolytes, and ___% of water is absorbed in the small intestine

A

Almost all ingested food
80%
90%

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24
Q

What part of the small intestine is involved in the absorption of carbs? Proteins? Lipids? Water? What about bile salts?

A

Entire SI involved in absorption of water and lipids

Carbs & protein in jejunum

Bile salts in terminal ileum

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25
What are the 5 mechanisms of absorption?
Active transport Passive transport Facilitated diffusion Co-transport Endocytosis
26
What is active transport? What’s used as a “pump”? Give an example
Refers to movement of a substance across a cell membrane going from an area of lower concentration to higher concentration (up the concentration gradient) ACTIVE GOES UP!! Proteins within cell membrane used as pumps, using ATP to move the substance Nucleic acid digestion products in lipid absorption
27
What is passive diffusion?
Refers to movement of substances from areas of higher concentration to area of lower concentration Passive does DOWN!!
28
What is facilitated diffusion? What’s an example?
Refers to one ent of substances from area of higher concentration to area of lower concentration (like passive diffusion) BUT uses a carrier protein in the cell membrane I.e - fructose (via GLUT5)
29
What is co-transport when talking about absorption? When is this used?
In absorption, uses the movement of one molecule through the membrane from higher to lower concentration to power the movement of another from lower to higher Used in absorption of glucose & galactose and amino acids - all with Na+ ions
30
Difference between water soluble nutrients and lipid soluble nutrients in absorption?
Since cell membrane in made up hydrophilic phospholipids, water soluble nutrients must use transport molecules embedded in the (apical) membrane to enter cells Lipid soluble can diffuse through plasma membranes
31
How is glucose absorbed/transported into cells? Galactose? Sucrose? How are they then transported into the bloodstream?
Both glucose and galactose via co-transport/secondary active transport using Na+/K+ pumps on basal membrane to pump Na+ out of cell or back into lumen Fructose via facilitated diffusion via GLUT5 Then monosaccharides are transported into bloodstream via GLUT2 transported and go to tissues or liver to be stored
32
How are proteins absorbed? Where is most of it absorbed (what %??) ? Type of carrier?
Active transport, mainly in duodenum and jejunum Most in SI, 95-95% Carrier can vary, but most linked to active transport of sodium
33
What happens in lipid digestion? Where does it start? what enzymes are released? What hormones are involved?
Mouth secretes gastric lipase which hydrolyzes fat then goes to stomach where gastric lipase hydrolyzes fat (still in TG chunks) Then goes to SI (duodenum), where fat cells and acidity of stomach cause release of CCK and secretin CCK stimulates release of bile and pancreatic juices/enzymes, secretin causes release of secretin which changes pH in SI to 6.5 Pancreatic lipase breaks down emulsified fat (from bile) to FAs and glycerol
34
What is CCK (enzyme? Hormone?) What causes it to be stimulated? Where is it released and what does it do?
Hormone released from SI, released from stomach acid and fat cells Stimulates bile production and pancreatic juice/enzyme
35
What is secretin (enzyme? Hormone?) What causes it to be stimulated? Where is it released and what does it do?
Hormone released from SI Acidity of stomach and fat cells cause release Produced bicarbonate which raises pH of SI to 6.5, which is ideal for fat digestion
36
What it the ideal intralumenal pH for fat digestion?
6.5
37
What is the role of bile salts?
Emulsify fat so pancreatic lipase can breakdown to glycerol and 2 FFAs
38
Difference between SCFA and long-chain fat acid absorption?
SCFA relatively water soluble, so can enter the enterocytes directly. Although hydrophobic, they’re small enough to be absorbed via simple diffusion LCFA - enclosed into micelles from bile salts and lecithin, which can squeeze between micro ills and get near luminal cell surface. FAs and glycerol exit micelle and absorbed via simple diffusion
39
What happens to the free fatty acids and monoacylglyderies once they enter the epithelial cells (enterocytes)?
1. Reincorporated into TGs 2. Packaged into chylomicrons 3. Pass through large pores of lacteals (lymphatic capillaries) and transported to lymphatic vessels and emptied through thoracic duct 4. Once in bloodstream, lipoprotein lipase breaks TG apart to glycerol and FFAs 5. Used for energy, stored in adipose tissue, and liver used remaining chylomicron remnants and combines with proteins to make lipoproteins for cholesterol transport
40
What is a micelle? What’s its purpose?
Engulfs FFA and glycerol and combines with cholesterol and fat soluble vitamins to allow for entrance into enterocytes. Hydrophilic ends face outside (face water environment of lumen) and hydrophobic tails turn to the interior)
41
What is a chylomicron? What is its purpose?
Water soluble lipoprotein Once FFAs and glycerol have been combined to make TGs in the enterocytes, they’re packaged in chylomicrons and transported out of the cell and through large pores of lacteals (lymphatic capillaries)
42
What is the job of lipoprotein lipase?
Breaks apart TGs in chylomicrons once they’re in the blood stream so they can be used for energy or stored
43
Describe mineral/electrolyte absorption? What are the sources of electrolytes being absorbed (food? GI secretions? Both?) What two minerals are exceptions to this rule?
Electrolytes absorbed by SI are from BOTH food and GI secretions Most absorbed via active transport, with co-transport mechanisms ending in accumulation of sodium inside cells and decrease of K+ in cell. Sodium/potassium pump (needing ATP) restores the gradient by pumping sodium out and K+ in Iron & calcium exceptions
44
How is iron absorbed? What happens when the body has enough iron? What about when the body needs iron?
Absorbed via active transport Once inside cell, binds with ferritin to make iron-ferritin complex that store iron until needed When body has enough, stored iron is lost by worn out cells sloughing off When body needs more (I.e. menstruation) there’s an increased uptake of iron from intestines and accelerated release into blood
45
Do men and women have the same amount of iron transport proteins in their intestinal cells?
No, women has 4x more d/t more iron loss from menstruation
46
Describe calcium absorption - What determines the absorption of dietary calcium? What gland is involved?
Blood levels of ionic calcium determine the absorption of dietary calcium When levels drop, parathyroid hormone stimulates release of calcium ions from bone and increases reabsorption from kidneys. PTH also upregulates activation of vitamin D in kidney which facilitates intestinal calcium ion absorption
47
What is the common bile duct?
A “shunt” that carries bile from the liver and gallbladder through the pancreas e and into the duodenum.
48
What is the job of bile, where is to made and stored, what stimulates it?
Help with breakdown of fat, made in the liver and stored in gallbladder, fats and proteins stimulate the release of CCK which stimulate the release of bile from the gallbladder which travels down the common bile duct through the pancreas to the duodenum. Bile (containing bile salt) mixes with pancreatic enzymes to speed up digestion and absorption of nutrients
49
What is an ectoenzyme. Name the primary digestive ectoenzymes
Enzymes that are secreted by a cell and function outside of that cell Amylase, lipoprotein lipase, pectinase, pepsin, trypsin
50
Bile contains various components to create bile salts. Those items are:
Colic acid Chenodeoxycholic acid Taurine Glycine Cholesterol Electrolytes Water
51
What are the 3 sections of the large intestine?
Ascending colon Transverse colon Descending colon
52
What are the primary roles of the large intestine? (2)
Reabsorb water and ferment starches
53
50 g of soluble fiber can have what negative affects on the body?
Prevent fat absorption and inhibit non-fiber absorption increasing sugar and starch levels in the colon
54
Examples of soluble fiber, insoluble fibers, and non-fermentable fibers
Soluble: beta-glucans, gums, pectins, fruits, veg Insoluble: cellulose and lignins Nonfermentable: psyllium (also contains soluble fiber); makes up the mass of the stool
55
What is the role of soluble fiber? Gives examples
Slows down food, lowers blood sugar, lowers cholesterol Oats, oranges, psyllium, beans, Brussels sprouts Water soluble and forms a gel!
56
What is the role of insoluble fiber? Examples?
Keeps you full and regular Skins of fruits and veg, bran
57
How does fiber influence the gut microbiota? How do the microbiota help with decreasing fat accumulation?
Microbes ferment fiber to SCFA (acetate, propionate, butyrate) which bind receptors to satiety hormones GLP-1 and peptide tyrosine tyrosine (PYY) SCFA also bind GP coupled receptors on adipocytes and stimulate breakdown and utilization of fat (decreases fat accumulation) partly through beta ox and then through decreasing lipid synthesis via decreasing insulin signaling
58
Role of SCFAs (6)
Responsible for intestinal integrity and immune health Supply energy to the enterocytes in the large intestine Anti-inflammatory Agents Glucose homeostasis Cholesterol metabolism Obesity regulation and gene expression
59
List causes of an imbalance in the micro flora of the large intestine?
Baby formula, diet high in resistant starch (too much of a good thing), low fiber diet, low production of digestive enzymes, oral antibiotics, xenobiotics and exotoxins Stress, consuming foods you’re intolerant too, a SAD diet, not having enough probiotic foods in the diet, not having enough food diversity (picky eaters), poor sleep hygiene, smoking or drinking alcohol
60
Successful reseeding of the gut can take ____ at what dose?
6 months, 10B CFU per species - most OTC probiotics don’t contain this high a dose. One should also include prebiotics in addition. Probiotics need to make it through the HCl first, which is why such a high dose is recommended
61
SCFA have a direct link to some human pathological conditions. List those
IBD, IBS, diarrhea, cancer (has been proposed)
62
Describe butyrate and its role in the colon
4 carbon, the main end product of intestinal bacterial fermentation of mainly non digestive carbs (resistant starch). It’s absorbed by the colon cells and is the main energy source for colonocytes which is why levels are lower in the blood compared to others. Role - increase mucus production, decrease cell permeability, promote tight junctions, decrease pH. Considered anti-diarrheal d/t it’s taken up into cells with Na+ (and water),
63
Describe butyrate’s role in colon cancer and inflamed colon cells
Shown to inhibit colon carcinogenesis and decrease inflammation in colonocytes by inh8ibiting NfKB
64
Describe a “functioning barrier” of the SI
Tight junctions are tight (there’s no “leaky gut”) in the intestinal tract which allows for nutrients to get into the bloodstream but keep waste and pathogens moving through the GI tract
65
In order for the SI to maintain its tight junctions, what needs to be in place?
1. Healthy microbiota 2. Secretory IgA (released by the gut-associated lymphatic tissue, GALT) 3. 50-70% of the immune system is maintained by the GALT, the first line of defense 4. Peristaltic movement (speed at which food flows) 5. Filtration of the enterocytes (cells lining the intestinal wall that create tight junctions, filtration is the process of selective absorption of nutrients and other substances from the intestinal lumen into the bloodstream and lymphatic system) 6. A healthy mucosal lining
66
What two nutrients are important for maintaining a healthy barrier function in the SI?
Glutathione and glutamine
67
What is glutathione? Where is it made and where will you find it in its highest concentration?
Intestinal antioxidant primarily made in liver and found in high concentrations in the duodenum and the stomach
68
What amino acids make up glutathione?
Cysteine, glycine, and glutamine
69
What happens in the digestive tract when glutathione levels are low?
Environment for leaky gut is created, its important for proper intestinal barrier function!
70
Describe glutamines role in the digestive tract
It’s an amino acid that is the primary fuel source for enterocytes (the cells that line the intestine and make up the tight junctions). If these cells aren’t being fed, they don’t function as well. Also fuel the microvilli Needed for - 1. Healing intestinal permeability 2. To make glutathione which is important for barrier function
71
What are the microvilli in the SI needed for? What happens if they starve or are damaged? What’s a nutrient they need to help avoid this?
Nutrient absorption, decreased pathogen activity, health tight junctions When damaged - no nutrient absorption, increase pathogen activity, increased intestinal permeability Glutamine

CNS (7 decks)

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