Quiz 4 Flashcards
packet 5b slide 63-77 until packet 6b
what are the 2 lines of protection for the gastrointestinal tract?
physical barrier: mucosal lining
GI immune defense: cells form tight junctions that prevent material from gaining entry, below the mucosal lining are immune cells ready to attack when lining is compromised
what is leaky gut?
leaky gut (intestinal permeability) is a condition where the integrity of the
intestinal lining has been compromised, gaps allow undigested food particles and bacteria to pass through, triggering an immune response
celiac disease (response to protein gluten), food allergies (response to certain proteins in food), and Inflammatory Bowel Disease are examples
what is Inflammatory Bowel Disease?
ex. ulcerative colitis and crohn’s disease
increased intestinal permeability, foreign particles (pathogen, protein
fragment?) leak through the colon lining, immune system over responds (autoimmune disease) causing chronic
inflammation in regions of the GI tract
what are the functions of the large intestine?
- absorption of water and electrolytes
- microbial breakdown of undigested food residue
- formation, storage, and elimination of feces
what is the microbiota?
human microbiota consists of microorganisms (bacteria, viruses, fungi) that reside in various regions of the body, largest population of
microbes reside in the colon and is a dynamic ecosystem characterized
by microbial density and diversity
what factors influence the colonic microbiota density and diversity?
birth (vaginal vs c-section), infant feeding (human milk vs formula), old age (decreasing density/diversity), diet (meat vs plant based, fiber, alcohol, antibiotics)
what are non-digestible carbohydrates?
non-digestible carbohydrates (fiber
and resistant starch) provide a source
of energy for bacteria residing in the
colon, which fosters their growth and
proliferation (a dense and diverse
microbiota can inhibit the growth of pathogenic bacteria by fermenting non-digestible carbohydrates)
how are non-digestible carbohydrates fermented?
non-digestible carbohydrates are fermented by microbes for energy, which results in the production of butyrate, a short-chain fatty acid and
the primary energy source for colonocytes (epithelial cells that form the mucosal lining of the colon), supports the healthy of the colon’s mucosal lining by promoting the
production of a mucus layer, which helps protect against inflammation, infection, injury, and pathogens
what is dysbiosis?
disruption of the microbial ecosystem, can occur with a loss of beneficial organisms, which allows excessive growth of harmful organisms, or a loss of microbial diversity, environmental factors like antibiotic use can disrupt
the microbial balance, can increase disease risk particularly inflammatory
bowel disease (ulcerative colitis
and Crohn’s disease)
how can you restore the colonic microbiota?
probiotics foods provide live beneficial organisms, fermented foods (yogurt fermented milk products like sauerkraut, sour pickles, and fermented soy (miso)), prebiotics are nondigestible (dietary fiber) to promote
the growth of beneficial gut microorganisms
what is clostridium difficile (C. dif)?
the colonic microbiota is disrupted when a person takes certain antibiotics
(dysbiosis), clostridium difficile colonizes the colon and produces a toxin that causes inflammation and
injury to colon lining, treated with antibiotics but 20%- 40% chance of
recurrence, stool from a healthy donor can be transferred to patients
what is the histology of the small intestine like?
plicae circulares (PC): folds of the mucosa layer that project into the lumen, PC remain folded which increase the surface area of the SI, create a turbulent, spiral flow of chyme, which slows the movement of chyme and brings it into contact with the absorptive surface of the SI, villi project into the lumen (villi contain network of capillaries and lymphatic vessel (called
lacteal) circulates lymph to and from each villus, nutrients absorbed into the blood, lipids are absorbed into the
lymph) mucosal lining of SI is made up of epithelial cells called enterocytes, enterocytes are covered with microvilli, microvilli brush border produce enzymes
how does nutrient absorption in the small intestine work?
nutrient absorption entails crossing 2 cell membranes
1. nutrients cross the cell membrane (apical
membrane) facing the lumen to enter the enterocyte.
2. nutrients must cross the cell membrane (basolateral membrane) that is oriented away from the lumen to exit the enterocyte
nutrients absorbed into the blood circulate to liver by veins called the hepatic portal system (some nutrients are stored in the liver, liver acts as a filter and can remove harmful substances)
what is celiac disease?
gluten (protein) is highly resistant to digestion and is
broken down into a protein
fragment called gliadin, in susceptible individuals, epithelial cells gradually lose
adherence (tight junctions)
resulting in increased intestinal permeability (leaky
gut), gluten fragments (gliadin)
gain access to underlying
tissue and trigger immune
system response, damages villi of the SI to make them flatter which can lead to secondary malnutrition
what is the absorptive vs post-absorptive state of metabolism?
absorptive state (after eating): energy-yielding nutrients
(glucose, amino acids, and
fatty acid metabolized by cells
for energy (ATP)
post-absorptive state (fasting):
cells breakdown stored
nutrients into useable energy
forms (glucose, amino acids,
and fatty acids)
in the process metabolic waste products form
where are carbohydrates found?
found primarily in plant-based foods (grains, legumes, vegetables, and fruit) and milk
what is cellulose?
the main structural component of plants, made up of repeating glucose molecules, most abundant fiber in our diet
how are carbohydrates classified?
based on the number of sugar units:
simple carbohydrates:
monosaccharides (1 sugar) and disaccharides (2 sugars)
complex carbohydrates:
polysaccharides (many sugars)
what is condensation?
condensation reactions are the
opposite of hydrolytic reactions (break chemical bonds by the addition of water
molecules), condensation
reactions make chemical bonds by the formation of
water molecules, glycosidic bonds join monosaccharides together through condensation
how are glycosidic bonds named?
carbon atom numbers that bind to the water and direction of the hydroxyl group (-OH) on C1
hydroxyl group on C1 is above the carbon = beta (β)
hydroxyl group on C1 is below the carbon = alpha (α)
what are the types of added sugars in processed food?
sucrose (table sugar): disaccharide, glucose and
fructose in a 50:50 ratio
high fructose corn syrup (derived from corn starch treated with heat and enzymes): 55:45 ratio fructose to glucose, unlike sucrose, no chemical bonds joining the glucose and fructose (requires no digestion)
what is metabolic associated fatty liver disease (MAFLD)?
characterized by excessive fat
accumulation in the liver and metabolic dysfunction (type 2 diabetes, obesity, elevated blood lipids), fructose is metabolized mostly in the liver, excess intake of fructose increases fat production, leading to MAFLD
what does untreated fat accumulation in the liver lead to?
if left untreated, fat accumulation in the liver can progress through the following stages: hepatitis, cirrhosis, which in turn can cause ascites, and esophageal varices
- hepatitis (liver inflammation): enlargement of the liver obstructs the ability of blood to flow from the SI to the liver (hepatic portal
circulation), damages hepatocytes and can cause fibrous tissue to form
- cirrhosis: with chronic inflammation and fibrosis the liver becomes heavily scarred
impaired flow of blood between the SI and liver causes blood pressure to increase
- ascites: to alleviate the pressure building in
the flow of blood from the SI to the liver (hepatic portal circulation), plasma leaks out of blood vessels and into surrounding tissues
in the abdominal cavity
esophageal varices: because blood can’t flow freely through the liver, it seeks alternate pathways through the veins of the lower esophagus and upper stomach, these veins are not designed to handle large volumes of blood, so they become dilated and swollen, forming esophageal varices, these fragile varices are under high pressure and can easily rupture, leading to life-threatening upper GI bleeding
what are the different types of polysaccharides?
starch (amylose and amylopectin), glycogen, and fiber, the difference between polysaccharides is based off of the type of glycosidic bonds and the arrangement of glucose molecules
where are each kinds of polysaccharides found?
plants use starch (amylose and amylopectin) to store glucose/energy, glycogen is found in the liver and skeletal muscles (only small amounts of glucose can be stored as glycogen), liver glycogen provides glucose when blood glucose levels are low, enzymes split liver glycogen apart by glycogenolysis
what does muscle glycogen do?
the adrenal glands release stress hormones
(epinephrine and cortisol) in response to
increased demand for glucose in skeletal
muscle cells (flight or fight response, prolonged physical activity), glucose liberated from muscle glycogen is not released into the blood (used by skeletal muscle for energy since skeletal muscle cells lack the enzyme
needed for glucose to be released into the
blood
what is glycogen supercompensation (carbohydrate loading)?
method used by endurance athletes to increase glycogen stores for the purpose of
enhanced endurance performance, glycogen depletion triggers an adaptive response which causes muscles and liver cells to store
greater amounts of glycogen, low levels of carbohydrate consumption/exhaustive
exercise followed by high levels of carbohydrate consumption/reduced exercise
what is dietary fiber?
dietary fiber refers to a naturally occurring,
diverse group of plant polysaccharides (other
than starch) that cannot be digested in the
human small intestine, beta bonds in dietary fibers are impervious to human digestive enzymes
soluble fiber has a high-water holding
capacity and form gels (high viscosity) in
the small intestine which keeps fecal matter soft and forms viscous layer that decreases
absorption of cholesterol and glucose
insoluble fiber does not mix with water
and adds bulk to feces
what is total fiber?
functional fiber + dietary fiber, dietary fiber is found natural in foods whereas isolated functional fiber is added to processed
foods
how does carbohydrate digestion work?
dissachardies like lactase, sucrase, maltase, reside along the brush bored and hydrolize glycosidic bonds in lactose, sucrose, and maltose resulting in monosaccharides like glucose, fructose, and galactose throughout the digestive process
what is lactose intolerance?
insufficient lactase production, without lactase, lactose is not digested, passing into large intestine, this causes diarrhea, gas, cramping to occur, is genetic (globally, 70%
population stop producing lactase after weaning, secondary to other illness (celiac disease), or age-related
how does starch digestion work?
salivary glands produce salivary amylase and the pancreas produces pancreatic amylase
salivary amylase initiates starch digestion (amylase functions at high pH so this only occurs in the stomach), pancreatic amylase then continues to digest starch by breaking it down in maltose, maltase (a brush bored enzyme) the completes starch digestion by splitting maltose into glucose molecules
what is the difference between amylose and amylopectin digestion?
amylopectin is enzymically digested to glucose units until a branch point is reached, these are referred to as limit dextrins, the final step in amylopectin digestion requires an enzyme called limit dextrinase (brush
border enzyme) that hydrolyzes alpha 1,6 glycosdic bonds release glucose molecules
what are the risks of high blood glucose?
long-term: prolonged elevation of blood glucose levels (hyperglycemia) over time is unhealthy and can damage blood vessels, eyes, kidneys, and nerves
short-term: when blood glucose levels are too low (hypoglycemia) it can cause coma and death
what are the two functions of insulin?
- insulin is needed for certain cells to take up
glucose from the blood - insulin promotes storage of excess energy which stimulates anabolic pathways (store
energy) and Inhibits catabolic pathways
(break down of stored energy)
what is the insulin response?
- insulin binds to insulin receptors embedded in cell membranes of fat cells (adipocytes) and skeletal muscle cells
- insulin binding to IR signals intracellular storage vesicles that house GLUT4
- GLUT4 relocate and fuse to the cell membrane
- GLUT4 enables glucose molecules to cross cell membranes to deliver energy to cells
what is the role of insulin in the fed vs fasted state?
fed: certain cells require insulin for glucose to
cross cell membrane
insulin promotes storage of excess glucose (anabolic) as glycogen and as fat: promotes glyvogenesis (glucose to glyvogen) and lipogenesis (excess glucose to fatty acids)
catabolic pathways: insulin inhibits the break down stored energy (glycogen and fat), lipolysis (break down of stored lipids), glycogenolysis (break down of glycogen to glucose), and preoteolysis (break down of muscle protein to AA)
fasting: insulin levels are low, glucagon is high, catabolic pathways increase glycogenolysis (break down of liver glycogen to glucose), lipolysis (break down of stored fats), and proteolysis, under prolonged fasting gluconeogenesis (making glucose from muscle protein) and ketogenesis (used fatty acids to make ketones, fatty acids can not be used to make glucose) can occur
how does the body adapt to semi-starvation?
if cells depend solely on protein (amino acids) to meet existing need for glucose
(gluconeogenesis), survive < 3 wks, the body adapts to semi-starvation (limited glucose availability) by using glucose sparingly, this is accomplished by an adaptive response called ketogenesis (rapid breakdown of fatty acids and subsequent conversion into ketones), ketones bodies can be used as a form of energy for brain and cardiac muscle
