Adv 1 Exam 2: CHO's & Fiber

CHO’s provide __ of food energy consumed by humans worldwide

50%

What CHO sources feed the world?

rice, corn, wheat

How many sugar units do oligosaccharides have?

3-10

How many sugar units do polysaccharides have?

>10

Monosaccharides and disaccharides are both

simple CHOs

The monosaccharides are

glucose, fructose, galactose

The disaccharides are

sucrose, lactose, maltose, trehalose

Sucrose monosaccharides

glucose + fructose

Lactose monosaccharides

glucose + galactose

Maltose monosaccharides

glucose + glucose (a-1,4)

Trehalose monosaccharides

glucose + glucose (a,a-1,4)

Oligosaccharides and polysaccharides are

complex CHOs

What are the oligosaccharides?

raffinose, stachyose, verbascose

What are the polysaccharides?

Starch, glycogen, dietary fiber

What kind of CHO are dextrins?

complex

What are dextrins, starch, and glycogen made of?

glucose only

What determines digestibility of CHOs?

type of glycosidic bonds

Maltose bond

a-1,4

Lactose bond

B-1,4

Sucrose bond

A-1,2

Trehalose bond

A-1,1

Dextrins

made from starch (corn or rice), usually 3-20 units

Limit dextrins

type of branched oligosaccharide that remains after starch of glycogen is partially broken down by a-amylase

Maltodextrins

made of only glucose, reduced sweetness, commonly used in sports nutrition as CHO source

Amylose structure

linear glucose molecules, A-1,4 bonds

Amylopectin structure

glucose molecules bonded together with branches at A-1,6 bonds

Glycogen structure

highly branched glucose molecules with A-1,4 and A-1,6 (branches)

Starch

storage form of glucose in plants (amylose or amylopectin)

What type of starch is more slowly digested?

high amylose starch

glycogen

storage form of glucose in animals (liver and skeletal muscles)

cellulose

dietary fiber, not an energy source

homopolysaccharides

dietary polysaccharide composed of only one sugar type

heteropolysaccharides

dietary polysaccharide made of multiple sugar types

Where are CHOs digested in the GI tract?

in the mouth and SI by enzymes

What enzyme digests A-1,4 bonds in the mouth?

salivary a-amylase

What enzyme digests A-1,4 bonds in the SI?

pancreatic a-amylase

What digests A-1,4, A-1,2 and A-1,6 bonds?

a-glucosidases

digestion of amylose & amylopectin

salivary a-amylase —> pancreatic a-amylase —> specific enzymes in enterocyte brush border (a-glucosidases)

What enzyme in the BB further digests maltose?

maltase-glucoamylase, starts at outer ends and works inward

Sucrase breaks

A-1,2 bonds

Lactase breaks

B-1,4 bonds

Trehalase breaks

A-1,1 bonds