Carbohydrates Flashcards
What is the process of plants taking in carbon dioxide and water, then after capturing energy from the sun, producing glucose and oxygen?
photosynthesis
How are carbohydrates categorized?
- simple
- complex
How many types of simple carbohydrates are there?
- Monosaccharides
- Disaccharides
What are the simplest carbohydrates consisting of one sugar molecule?
Monosaccharides
What are the building blocks of more complex carbohydrates?
Monosaccharides
What are the three main dietary monosaccharides?
- Glucose
- Galactose
- Fructose
Each dietary monosaccharides has 6 carbon atoms. How many Hydrogen and Oxygen do they have?
12 Hydrogen, 6 Oxygen.
C6, H12, O6.
What are monosaccharides that have 6 carbon atoms?
hexose sugars
What is the difference in the chemical structure between glucose and galactose?
one hydroxyl group (-OH) faces in opposite directions
What is the difference in ring structure between Fructose and glucose/galactose?
Fructose has a 5-sided ring structure
Glucose/galactose has 6-sided ring structures
What are 5 carbon monosaccharides found in small amounts of fruit?
Pentoses
What is synthesized from hexose precursors and incorporated into other compounds?
Pentose
What are two monosaccharides joined by a glycosidic bond?
Disaccharide
What are the most common disaccharides?
- sucrose
- maltose
- lactose
Glucose + Fructose =
Sucrose
What is another name for sucrose?
table sugar
Glucose + Glucose =
Maltose
How many foods consist of maltose?
very few
Galactose + Glucose =
Lactose
what is another name for lactose?
milk sugar
What type of reaction forms disaccharides?
Condensation
What determine digestibility of carbohydrates?
alpha and beta configuration
What are the two main types of complex carbohydrates?
Oligosaccharides
Polysaccharides
What type of bond does sucrose have?
glucose and fructose with an a(1,2) bond
What kind of complex carbohydrates are prebiotics?
Oligosaccharides
What type of bond does lactose have?
galactose and glucose with a B(1,4) bond
What type of bond does maltose have?
glucose and glucose with a a(1,4) bond
What type of bond is Trehalose?
glucose and glucose with an a(1,1)a bond
How many monosaccharides does an oligosaccharide have?
3-10 monosaccharide units
How are oligosaccharides digested?
by the gut bacteria because they cannot be completely hydrolyzed by digestive enzymes
How many monosaccharides make up polysaccharides?
> 10 monosaccharide units. (could range in the thousands)
What is a polysaccharide composed of only one type of monosaccharide?
Homopolysaccharide
What is a polysaccharide composed of two or more different types of monosaccharides?
Heteropolysaccharide
What are the three most common polysaccharides?
- Starch
- Glycogen
- Fiber
What is the storage form of carbohydrates in plants?
Starch
What are two forms of starch?
- Amylose
- Amylopectin
What is the difference between Amylose and Amylopectin?
Amylose is a linear chain bonded together by a(1,4) glycosidic bonds. (no branches)
Amylopectin has a(1,4) glycosidic bonds and a(1,6) bonds that occur and branched points. (highly branched arrangement).
What is the primary storage form of carbohydrates in animal tissue and localized to the liver and skeletal muscles?
Glycogen
Why is it beneficial for Glycogen to be branched?
It’s easier to break off a portion at the branch to use rather than breaking carbons off one by one.
What is a polysaccharide that are resistant to digestive enzymes, but a great energy source for intestinal bacteria by breaking it down to gas and short chain fatty acids?
Fiber
What is the difference between starch and fiber?
The bonds. Starch is bonded with a(1,4) and Fiber is bonded with B(1,4)
Which classification of fiber tends to dissolve in colon and forms a gel, slowing digestion/absorption?
This absorbs water, thus softening fecal matter.
Soluble Fiber
Which classification of fiber does not dissolve in water, passes through the GI intact (increasing the fecal weight and volume, decreasing constipation)?
Insoluble Fiber
How does fiber effect health?
- alleviates constipation and reduces risk of diverticulitis
- delays absorption of monosaccharides- in turn reduces glycemic index
- reduces cholesterol
- can bind metals (may bind and cause lower absorption rates
What results when small, protruding pouches form along the wall of the large intestine?
Diverticulosis
What are the protruding pouches that form along the large intestines called?
Diverticula
What reduces the likely-hood of Diverticular Disease by 40%?
Fiber
What parts of the digestive system (in order) break down Carbohydrates into monosaccharides?
- Mouth
- Stomach
- Small intestine
- Brush Border
What are Hydrolytic enzymes generally called?
glycosidases (aka carbohydrates)
What do salivary glands release?
salivary a-amylase
What does salivary a-amylase hydrolyzing an a-(1,4) glycosidic bond in amylose create?
dextrins
what does salivary a-amylase hydrolyzing an a(1,4) glycosidic bond in amylopectin form?
dextrins
where does digestion of amylose and amylopectin start?
in the mouth
which a-amylase interacts first in digestion?
salivary a-amylase
which a-amylase interacts after salivary a-amylase?
Pancreatic a-amylase
what does the acidity of gastric juices do to the enzymatic activity of salivary a-amylase for amylose?
destroys the activity
What does the acidity of gastric juices do the enzymatic activity of salivary a-amylase for amylopectin
destroys the activity
What happens to the dextrins in the stomach?
No further digestion of dextrins. Dextrins pass unchanged into the small intestine
what does pancreatic a-amylase do to amylose?
hydrolyzes a-1,4 glycosidic bonds to turn into maltose
what does pancreatic a-amylase do to amylopectin?
hydrolyzes a-1,4 glycosidic bonds in amylopectin and dextrin are broken down into maltose and limit dextrins.
Is there any digestion of amylose and amylopectin in the stomach?
No
Where is the maltase enzyme located at?
Brush Border
How is amylose digested in the Brush Border?
After salivary digestion, Maltose is hydrolyzed by maltase turning into glucose.
What does maltose form into after reacting with maltase?
free glucose molecules
How is amylopectin digested in the brush border?
a(1,6) bonds in limit dextrins are hydrolyzed by a-dextrinase.
What does dextrin turn into after reacting with a-dextrinase?
free glucose molecules
Where does the digestion of disaccharides take places?
Brush border of the small intestine
What do intestinal disaccharidases do?
hydrolyze disaccharides
after disaccharides react with disachharidases, Where do resulting monosaccharides go?
transported into enterocytes
What is the deficiency of lactase, the enzyme that digests lactose?
Lactose Intolerance
How does lactose intolerance cause symptoms like bloating, nausea, flatulance, diarrhea, etc.?
Since most lactose enters the large intestines undigested (lack of lactase in SI), the bacteria digests the lactose.
How is lactose intolerance diagnosed in a clinical setting?
approximately two hours after (25-50g) lactose ingestion, two components can diagnose lactose intolerance
- no increase in blood glucose
- increase of hydrogen via breath test (H is byproduct)
How do monosaccharides go from the GI tract into the blood?
absorption through enterocyte in small intestine.
True or False
The mechanism of absorption differs among the different monosaccharides.
True
How are glucose and galactose transported through the enterocyte?
Glucose/Galactose transport into the enterocyte by moving from lower to higher concentration utilizing ATP.
=active transportation
What type of transport does glucose and galactose use?
Active Transport
How is fructose transported through the enterocyte?
Moves from higher to lower concentration with assistance from transport proteins. (but does not require ATP)
Facilitated transport
apical - GLUT5
basolateral - GLUT2
What type of transport does fructose use?
facilitated diffusion
apical - GLUT5
basolateral - GLUT2
Where do the absorbed monosaccharides circulate too within the hepatic portal system
Liver
What is the difference between apical membrane and basolateral membrane
Apical: closest to the lumen of the small intestine; hosts SGLT1 activity.
basolateral: membrane away from the lumen; Hosts GLUT2 and sodium pumps
Where is GLUT5 and what does it do?
in the enterocyte; transports fructose from apical to basolateral GLUT2 using facilitative transport.
What type of transport has molecules move from low to high concentration and uses energy?
active transport
What type of transport utilizes membrane proteins to go across the plasma membranes?
facilitated transport
What type of transport have molecules move from high to low concentration not requiring energy?
Passive Transport
What carrier proteins are used for absorption of Glucose/Galactose from the lumen of the small intestine into circulation.
Apical SGLT1 - Basolateral GLUT2
What carrier proteins are used for absorption of Fructose
Apical GLUT5 - Basolateral GLUT2
What GLUT gets recruited when luminal concentrations are high (after a big meal)?
GLUT2
What transporter allows glucose to re-enter the circulation and exists in the kidney?
SGLT2
What is a negative consequence of ingesting glucose after SGLT1 and SGLT2 blockade?
SGLT1: Indigestion
SGLT2: UTIs
What is a positive consequence of ingesting glucose after SGLT1 and SGLT2 blockade?
Not storing calories = weight loss
What is the “master regulator” of the metabolism and is responsible for maintaining blood glucose levels?
Liver
What refers to the alterations in blood glucose following a meal?
Glycemic Response
What is a normal blood glucose range to have at fasting?
60-100mg/dl
What is a normal blood glucose peak to have after a meal?
<140 mg/dl
What is the state in which blood glucose levels is within normal range?
Euglycemia
How does Activity level affect digestion after eating?
moderate activity increases digestion rate. Vigorous activity inhibits digestion because of the sympathetic response
A partial breakdown product formed during starch digestion, consisting of varying numbers of glucose units
Dextrin
A partial breakdown product formed during amylopectin digestion that contains three to four glucose molecules and an a-1,6 glycosidic bond.
limit dextrins
What tract holds SGLT1?
GI tract
What tract holds SGLT2?
Urinary tract
How does SGLT2 inhibitors work?
Used in type 2 diabetes to lower blood sugar.
Differ from most anti diabetic drugs by causing kidneys to excrete glucose into the urine instead of increasing insulin/insulin sensitivity.
What are 3 AUC graph differences between high and low glycemic index?
- Peak High-GI foods cause a rapid rise and fall in blood sugar and insulin levels (spike).
2.Low-GI foods result in slower, steadier rise and fall.
- A right shift indicates a longer digesting time.
(blood glucose AUC for food w.50g CHO × 100)/(blood glucose AUC for 50g glucose)
Glycemic Index
What are three limitations over the Glycemic Index?
- Porportions of what is tested and what people eat in a serving is off.
- Some foods have low GI but other health risks (fructose)
- Gi influenced by other foods eaten in meal.
What is a hormone that shuttles glucose into muscles and comes from the beta cells of the pancreas
Insulin
What is the goal of insulin?
maintain blood glucose levels by facilitating glucose removal from blood stream and into cells of the body
What biological effects does insulin have in the muscle?
Increase in Glucose uptake, glycogen synthesis, protein synthesis.
What biological effect does insulin have in the blood vessels?
Increase in vasodilation.
What biological effect does insulin have in the liver
Decrease in gluconeogenesis and glycogenolysis.
Increase in glycogen synthesis.
What biological effects does insulin have in the fat cells?
decrease in lipolysis
Increase in FA uptake and TG synthesis.
what means “formation of new sugar” and occurs in the liver
Gluconeogenesis
What is the biochemical pathway in which glycogen breaks down into glucose-1-phosphate and glucose?
glycogenolysis
what hormone formed in the pancreas promotes the breakdown of glycogen to glucose in the liver?
glucagon
What hormone produced by beta cells in the pancreas decrease the amount of glucose in the blood?
insulin
What disease occurs when blood glucose is too high due to insulin resistance?
Type 2 diabetes
Does glucagon decrease or increase blood glucose?
increase
does insulin decrease or increase blood glucose?
decrease
How does glucagon work?
promotes breakdown of glycogen to glucose
promotes use of noncarbohydrate sources to make glucose
What stimulates the pancreatic a-cells to release glucagon?
low blood glucose levels
What is a gut-derived hormone processed from the glucagon gene?
Glucagon like peptide 1 (GLP-1)
What stimulates the release of GLP1 from intestinal cells?
glucose in the intestines
GLP1 collectively accounts for how much insulin secretion? %
70%
What hormone stimulates insulin secretion and inhibits glucagon secretion?
GLP-1
What effect does GLP-1 stimulating insulin and inhibiting glucagon secretion have on blood glucose concentrations?
GLP-1 limits the rise of glucose after a meal and postpones glucose falling below normal levels.
How long does GLP-1 last?
1/2 <2 minutes because it is broken down by an dipeptidyl peptidase IV (DPP4)
Is GLP-1 more active or less active in patients with type 2 diabetes?
less active.
What is a drug that effects GLP1 and how does it work?
DPP4 Inhibitors: sitagliptin, inhibits glp-1 breaking down and allowing more work.
GLP agonist: trulicity, must be injected, increases insulin via GLP-1 receptors.
What does the fate of glucose depend on once it leaves the circulation and enters target tissues?
the energy needs of the body.
What glucose transporter is insulin dependent
GLUT4
