Unit 1 - Carbohydrates: types, digestion, absorption and transport

major source of energy fuel in the average diet

carbohydrates

approximately ½ total caloric intake is in the form of what

polysaccharides and simple sugars

2 major types of polysaccharides

starches and dextrins

size differences in dextrins and starches

dextrins are slightly smaller

main types of simple simple sugars

sucrose (table sugar), lactose (milk), fructose (fruit)

basic chemical structure/form of a carb

CH2O

H

I

C = O

I

H

smallest simple sugar

glyceraldehyde

most common complex sugar

glycogen

what is glyceraldehyde broken into

carbs and glycerol

where is glycogen stored

in the muscle

what organisms make glycogen

animals and humans

what organisms make starch

plants

how do humans get starch

eating plants

types of monosaccharides

trios, tetrose, pentose, hexose, heptose

what are the types of monosaccharides classified by

number of carbons

most important type of monosaccharides

hexoses

which type of monosaccharide is a major source of energy

hexose

important hexose molecules

glucose

fructose and galactose (smaller quantities)

most abundant monosaccharide

glucose

what are pentoses formed from

hexoses

most important pentose molecules

ribose

what is ribose used for in cells

ATP, DNA, RNA

what is one of the sugar molecules in every disaccharide structure

one glucose out of the 2 monosaccharide parts

dietary monosaccharides

glucose, fructose, galactose

blood sugar are in reference to what dietary sugar

glucose only

primary carbon on a sugar molecule

carbon down and to the right of the “in ring” oxygen (attached to an OH and an H)

how are disaccharides formed

condensation of 2 monosaccharides (OH group leaves one monosaccharide and H leaves the other)

monosaccharides forming maltose

glucose + glucose

monosaccharides forming sucrose

glucose + fructose

monosaccharides forming lactose

glucose + galactose

where can you find sucrose

cane sugar, beet sugar, table sugar, processed foods

high fructose corn syrup (HFCS) composition

45% glucose + 55% fructose

where can you find high fructose corn syrup

syrup form found in processed foods

difference in effect between HFCS and sucrose

depends on quantity eaten bc very similar on 5% difference

are oligosaccharides digestible?

some are some are not

oligosaccharide size

3-10 monosaccharides long

raffinose composition

gal-glu-fruc

stachyose composition

gal-gal-gluc-fruc

why are some oligosaccharides non digestible?

we dont have the enzymes to break down certain monosaccharide combinations or to break down certain bond types

what are non digestible oligosaccharides called on food labels?

fibers

type of digestible oligosaccharides

dextrins (glu-glu-glu)

example of non digestible oligosaccharides

raffinose, starchyose

where are non digestible oligosaccharides found

beans, peas, and whole bran

where do non digestible oligosaccharides go after being eaten?

passed through to the intestines and then to bacteria

polysaccharide size

very big (usually over 10 monosaccharides)

important types of polysaccharides in nutrition

starch, glycogen, fiber

starch is what type of carb?

polysaccharide

glycogen is what type of carb?

polysaccharide

fiber is what type of carb?

polysaccharide

how do plants store carbs?

starch

types of starch

amylose and amylopectin

amylose

type of starch made of glucose molecules linked by a (1-4) bonds

amylopectin

type of starch made of highly branched glucose molecules that looks like glycogen

bond type in long straight branches of amylopectin

a (1-4) bonds

bond type in branched portion of amylopectin

a (1-6) bonds

what type of starch is fully digestible?

amylopectin

how do animals store carbs?

glycogen

where is glycogen stored?

in liver and muscle

where is glycogen made?

in liver

how does the liver use glycogen?

makes it and stores it, shares with other tissues if they are low

how do muscles use glycogen?

stores it and does not share with any other tissues

glycogen structure

most branched form of repeating glucose molecule

how is glycogen used as an energy source?

glycogenolysis converts it back to G6P

in muscle: G6P to fructose to phosphate → → glycolysis

in liver: G6P → glucose

what types of starches do we eat?

amylose and amylopectin

do we eat glycogen?

no

what is fiber?

non digestible plant polysaccharides

where are fibers found?

in plants

calories for fiber

less than 4 cal/g bc it cant be digested

fibers are what kind of carb molecule

poly or oligo

types of fibers

dietary or functional (defined by USDA), insoluble or soluble

where are dietary fibers found?

intact and naturally occurring in plants

where are functional fibers found?

manufactured, isolated, or extracted

are soluble fibers digestible?

no

soluble fibers speed

faster

soluble fibers function

increases transit time

prevents constipation

soluble fiber examples

pectins, gums, some hemicelluloses

insoluble fibers speed

slower so stays in body longer

insoluble fibers function

decreases transit time

increases fecal bulk

helps with diarrhea, pulls cholesterol

insoluble fiber examples

ligands, celluloses, some hemicelluloses

how are soluble fibers broken down in the body?

bacteria in the intestines ferment them and use them as energy (for the bacteria only not for us) which produces gas

digestive enzyme specificity

breaks specific bonds of specific molecules

a (1-4) bonds vs b (1-4) bonds

a bonds have H on same side so the chain looks straight and b bonds have H on opposite sides so the chain looks diagonal/bent

why are fibers non digestible?

they have bonds and molecules that do not have corresponding enzymes in our bodies

what are soluble fibers broken down into?

hydrogen, methane gas, CO2, short chain fatty acids

short chain fatty acid examples

acetic acid, butyric acid, propionic acid

what are short chain fatty acids used for in bacteria?

provide energy for bacteria

what are short chain fatty acids used for in humans?

stimulate water and sodium absorption into mucosa, provide collocates with energy, enhanced immune function, reduces atrophy of gut, decreases cholesterol

how do short chain fatty acids decrease cholesterol?

decreases pH of gut which lovers reabsorption of bile

inhibits cholesterol synthesis in the liver

do we digest cholesterol

no

what happens to unused/excess soluble fiber?

excreted as fecal matter and carries bile with it

sources of soluble fibers

fruits, vegetables, and whole grains

fiber recommendations based on gender

men recommended more grams of fiber than women

fiber recommendations based on age

men and women recommended less fiber after 50 years old

what is the GI tract

tube thru the body that digests and absorbs nutrients to be transported into bloodstream to be used by the body

accessory organs

liver, gallbladder, pancreas

accessory organ function

necessary for absorption but food does not pass thru them

parts of the small intestine

duodenum → jejunum → ileum

what does the small intestine have on its lining for absorption

villi and enterocytes on villi (brush border)

where do carbs go after absorption in small intestine?

enterohepatic circulation system (to liver and then passed on)

where do fats go after absorption in small intestine?

lymph system