Carbs (Quiz 1) Flashcards
What are the 3 functions of carbs?
1) energy
2) protect body proteins
3) prevent ketone bodies ( if theres too many ketone bodies = ketosis or ketoacidosis)
What are simple sugars?
mono or disaccharides
What are complex carbs?
oligo or polysaccharides
Are monosaccharides water soluble or insoluble?
water soluble
Which sugar class is found freely in nature?
monosaccharides only
What are the 3 important monosaccharides?
1) D- glucose (dextrose)
2) D-fructose (levulose)
3) D-galactose
Are disaccharides water soluble or insoluble?
water soluble
Disaccharides are formed by linking other monosaccharides together in a _______________ reaction
condensation
What 2 monosaccharides make up maltose?
glucose + glucose
What is the glycosidic bond in maltose?
alpha 1,4 glycosidic bond
What 2 monosaccharides make up sucrose?
glucose + fructose
What is the glycosidic bond in sucrose?
alpha 1, beta 2 glycosidic bond
What 2 monosaccharides make up lactose?
galactose + glucose
What is the glycosidic bond in lactose?
beta 1, 4 glycosidic bond
What are the 3 important disaccharides?
1) maltose
2) sucrose
3) lactose
Oligosaccharides are 3-10 units. What are 2 examples and where are they found?
raffinose and stachyose are found in beans and legumes
What are the 3 homo-polysaccharides discussed in class?
1) starch
2) cellulose
3) glycogen
(3k + monosaccharides (glucose) bound together)
What are the 2 starches we talked about?
amylose and amylopectin
Is cellulose digestible or indigestible?
indigestible
Where is glycogen stored?
in liver and muscles
Which starch is a linear chain of repeating glucose molecules?
amylose
What glycosidic bond(s) does amylose have?
alpha 1,4 glycosidic bonds
Which starch is highly branched with repeating glucose units?
amylopectin
What glycosidic bond(s) does amylopectin have?
alpha 1,4 glycosidic bonds with alpha 1,6 branch points
note: this is the same for glycogen
What has a similar structure to amylopectin but is more highly branched?
glycogen (repeating glucose units)
What glycosidic bond(s) does glycogen have?
alpha 1,4 glycosidic bonds with alpha 1,6 branch points
note: this is the same for amylopectin
What is the storage form of CHO for plants?
starch
What is the storage form of CHO for animals?
glycogen
Which end of polysaccharides allow for addition or release of glucose?
nonreducing ends
What is the major component of plant cell walls?
cellulose (repeating units of glucose)
What glycosidic bond(s) does cellulose have?
beta 1,4 glycosidic bonds
Cellulose is defined as fiber and is indigestible to humans. Why?
humans are unable to hydrolyze the beta 1,4 glycosidic bond
Other dietary CHOs we consume contribute to cell structure in animals and plants. Food additives are used to……
emulsify foods
What hetero-polysaccharides make up the ECM of animals?
hyaluronic acid and chondroitin sulfate (these are the 2 most common GAGs)
What sugars are usually present in glycoproteins and glycolipids?
-glucose
-xylose
-sialic acid
-mannose
-glucosamine
-galactosamine
What sugar is found in RNA?
ribose
What sugar is found in DNA?
deoxyribose
What are the 3 carbs usually found in food additives?
1) carrageenan (galactose sulfate)
2) agar
3) pectin
What are proteoglycans?
glycoprotein (glucose + sugar), consists of long GAGs (repeating disaccharide unit) attached to core protein, usually contains glucuronic acids (jelly like)
What are glycosaminoglycans (GAG)?
long hetero-polysaccharides consisting of a repeating disaccharide units
What is the recommended CHO intake for adults per day?
130 g a day
How many carbs should you eat a day to prevent ketosis?
test q
50-100 gm
What is the recommended percentage of energy that comes from carbs?
45-65% of total energy should come from carbs
T/F: generally speaking, the American population consumes 50-200 gm more of CHO a day than the recommended amount
true, primarily from white bread, soda, and baked goods
Are simple sugars nutrient dense?
no, low nutrient density
What is the recommended total kcal percentage of simple sugar intake a day?
test q
10%, but the absolute max should be 25%
T/F: simple sugars are added to food and drinks during processing
true
Are natural sugars (like fructose and lactose) included in simple sugar intake per day percentage?
no
What does glycemic response refer to?
how quickly glucose is absorbed after a person eats, how high blood glucose rises, and how quickly it returns back to normal
What is glycemic response compared to?
a given standard
Glycemic response is beneficial to keep track of for who?
diabetics to know which foods to avoid that give them a spike or fall
athletes, like an endurance runner should want a food that maintains their blood sugar for as long as possible
What is glycemic response influenced by?
amount of:
-starch
-fiber
-processing
-structure
-presence of other macronutrients
Which foods have a low glycemic index (GI of 55 or less)
-fruits
-beans
-seeds
-whole intact grains
-veggies
Which foods have a medium glycemic index (GI of 56-69)?
-white sugar
-juice
-regular ice cream
-banana
Which foods have a high glycemic index (GI of 70+)?
-glucose (dextrose)
-high fructose corn syrup
-white bread
-white rice
-sweet potato
-white potato
T/F: there is a direct relationship between diets high in fiber and colon cancer (greater than 35g per day)
FALSE- inverse relationship!!! 35 g a day decreases colon cancer by 40%
Dietary fiber is classified as ______________ or _____________
soluble, insoluble
Some fiber is insoluble in water. This means that it is….
non-viscous
What are the 3 insoluble fibers?
1) cellulose
2) hemicellulose
3) lignin
Which fiber is both soluble and insoluble?
hemicellulose
Which fibers cannot be fermented by the bacteria in the colon?
insoluble fibers
What fiber is excreted in feces as bulk fiber?
insoluble fiber
What is the function of insoluble fiber?
clean up GI tract and increase fecal weight
What are the major food sources of insoluble fiber?
-brown rice
-fruits
-legumes
-seeds, like flax seeds
-veggies like cabbage, carrots, and brussel sprouts
-whole grains
Does insoluble fiber increase or decrease fecal weight?
increase fecal weight
Does insoluble fiber increase or decrease transit time through the colon?
decrease transit time through colon
Which fiber provides the feeling of bulk and fullness?
insoluble fiber
What are the health benefits of insoluble fiber?
-alleviate constipation
-lower risk of diverticulosis, hemorrhoids, and appendicitis
-helps with weight management
Some fiber is soluble in water. This means it is….
viscous
What are the 4 soluble fibers?
1) agar
2) mucilage
3) pectin
4) hemicellulose (some)
Which fiber is found on the skin of fruit for apples, citrus, etc?
pectin
T/F: water soluble fiber forms a viscous solution, so it can be fermented by bacteria in the colon
true
What are the major food sources of soluble fiber?
-whole grain products especially oats and rye
-fruits like apples and citrus
-legumes
-seeds
-husks
-veggies
Which fiber lowers blood cholesterol by binding to bile?
test q
soluble fiber
Does soluble fiber decrease or increase the synthesis of secondary bile acids?
decreases (reduces conc. of secondary bile acids)
Does soluble fiber slow or speed up glucose absorption?
slows glucose absorption (this also in turn decreases risk for DM)
Does soluble fiber slow or speed up transit of food through upper GI tract?
slows transit of food
Which fiber holds moisture in stools (softens stool)?
soluble fiber
Which fiber yields SCFAs after fermentation that the colon can use for energy (contributes to good gut flora)?
soluble fiber
Soluble fiber lowers the risk for what 3 diseases?
heart disease, diabetes, and colon cancer
What enzyme is found in the mouth and breaks down carbs?
salivary amylase (ptyalin)
What is starch broken down to in the mouth?
dextrins and maltose
Amylase cuts ____________ o glycosidic bonds and the smallest product generated is maltose
alpha 1, 4
Can you taste the sweetness of carbs the more you chew it?
apparently yes
Pancreatic amylase is released and secreted into the duodenum. It cuts ___________ o-glycosidic bond
alpha 1, 4 (same as salivary amylase)
Pancreatic amylase will shorten the starch chain but cannot cut the branches. So there can be 3 different products:
1) alpha limit dextrins (alpha 1,6 glucose- glucose)
2) trisaccharide (maltotriose)
3) disaccharides (maltose)
What are the 4 intestinal enzymes that line the brush border of SI?
1) isomaltase (alpha-dextrinase)
2) maltase
3) sucrase
4) lactase
What does isomaltase (alpha-dextrinase) break down?
cleaves the branches of alpha limit dextrins, a product of amylopectin digestion
so it breaks an alpha 1,6 glucose glucose bond
What does maltase break down?
alpha 1,4 bond from a glucose-glucose linkage
so a maltose or maltotriose gets broken down and becomes just 1 glucose
What does sucrase break down?
alpha 1, beta 2 bond from a glucose-fructose linkage
What does lactase break down?
beta 1, 4 bond from a glucose - galactose linkage
Where do disaccharides undergo digestion?
in the SI
What is the major product of starch digestion?
maltose!!!!!
the other 2 products are maltotriose (3 glucose molecules linked together) and alpha dextrins (also known as alpha limit dextrin which is several glucose molecules linked together with at least one alpha 1, 6 branch point)
What is the product of amylopectin digestion?
alpha limit dextrin
Both glucose and galactose use which transporter for active transport into enterocytes?
SGLT
Fructose uses facilitated diffusion to get into enterocytes. What transporter is used?
GLUT 5
Active transport is faster than facilitated diffusion causing….
tremendous increases in plasma glucose
GLUT passive transporters absorb monosaccharides to the liver from the portal vein. From here then what happens?
-fructose and galactose are transformed to glucose
-released to blood stream
-allows the liver to control glucose content in the bloodstream
-stored as glycogen or fat
Why does HK present in the brain have a low Km compared with GK (HK D)?
every tissue has HK so theres a higher affinity than GK, and the only tissue that has GK is the liver
so HK has small Km and Vmax while GK has large Km and Vmax
What is lactose intolerance?
-lactose is indigestible or absorbable
-large intestinal bacteria metabolizes lactose and this causes gas, bloating, cramping, discomfort
What are the 2 forms of lactose intolerance?
adult onset or congenital
T/F: 25% of all adults in the US have some form of lactose intolerance (mild to severe)
true
Who has increased frequency of chances of being lactose intolerant?
African Americans, Asians, Arabs, or Ashkenazy Jews (70% in adults, 30% in children)
What can you do for lactose intolerance?
-eat small amounts of dairy with fat in it
-cheese and yogurt are usually tolerated well
-use products such as lactaid or lactose free products
How many glucose transporters are there?
at least 7
Insulin is not responsive to which GLUT transporters?
GLUT 1, 2, and 3
Where is GLUT 1 found?
found everywhere but especially in RBCs and brain barrier
Where is GLUT 2 found?
in the liver
Where is GLUT 3 found?
in neurons
Which GLUT transporters are responsive to insulin?
GLUT 4 only
note: levels of GLUT 4 are decreased in insulin resistance cases
Where is GLUT 4 found?
-adipose tissue
-skeletal and cardiac muscle tissue
GLUT 5 is a ____________ transporter
fructose
What is the adequate amount of intake for dietary fiber a day for men and women?
25 g a day for women, 38 g a day for men
Do Americans typically eat enough fiber?
no, we need to up our fiber intake (the average American eats only 13-17 g a day when we need 25-38 g a day)
What happens if you eat too much fiber (more than 60 g a day)?
-require extra intake of fluid
-bind to some minerals
-develop phytobezoars (phyto = stomach), its masses of undigested fiber matter that are typically associated with fibrous fruits and vegetables, or eating cotton balls)
What is diverticulosis?
condition in which the intestinal walls develop bulges in weakened areas
What is the treatment for diverticulosis?
-high fiber diet of fruits, veggies, whole grains (2 tsp of bran daily)
-exercise
-fluids, especially water
What is diverticulitis?
inflammation of the diverticula
What is the treatment for diverticulitis?
rest the bowel by going on a low residue diet, also known as low fiber diet
-this is commonly done with lots of liquids like fruit juice, soda, milk
-white rice or bread
-meat
High fructose corn syrup is known to cause what 2 diseases?
DM and obesity
What is high fructose corn syrup?
-40-90% fructose
-cornstarch treated with acid and enzymes
-conversion of glucose into fructose
-the same degree of sweetness as sucrose
-cheaper than other “sugars” and is used in many food products for a preservative
What are the 5 types of sweeteners we discussed in class?
1) high fructose corn syrup
2) brown sugar
3) maple syrup
4) honey
5) sugar alcohols (polyols)
Which sweetener is nutritious with iron and contains molasses?
brown sugar (better than white sugar according to Dr. Zhou)
What 2 sweeteners contain antioxidants?
maple syrup and honey
Does sugar alcohol contain alcohol?
no
Which sweetener is this?
-absorbed and metabolized slower
-does not generate acid like regular sugar
-large amounts cause diarrhea
-does not spike glucose levels like regular sugar so it is sometimes called diabetic sugar
boards q
sugar alcohols (polyols)
What is the sweetest sugar?
fructose (levulose)
What is the sweetest artificial sweetener?
alitame
Which of these compounds is a simple sugar?
A) raffinose
B) amylose
C) sucrose
D) cellulose
C) sucrose
Which of the following is NOT true?
A) cellulose is an insoluble fiber
B) rye and oats are good food sources of soluble fiber
C) pectin is made from apple skin
D) bread is a good source of fiber
D) bread is a good source of fiber
What is the principle carb produced by the action of amylase on dietary starch?
maltose
The enzyme that catalyzes the breakdown of maltose are secreted by?
SI
Glucose precursors are primarily derived from?
AAs
T/F: glycogen is a storage form of carbs in plants
false
T/F: potato is rich in complex carbs
true
T/F: whole grain is a good source of dietary fiber
true
T/F: drinking red wine is good for your health
false
What is sorbitol?
a sugar alcohol
