Fiber and Lipids Flashcards
In general, what does the word “fiber” refer to?
carbohydrates that are not digestible by human enzymes
Fibers are generally split into what two categories?
soluble (mostly viscous, but some non-viscous) and insoluble (non-viscous)
What are the three insoluble fibers we learned?
lignins
cellulose
some hemicelluloses
What are some of the soluble fibers we learned?
fructans (this one's non-viscous) psyllium B-glucans pectin gums some hemicelluloses
What about the bonds in fiber makes it indigestible?
they are glucose polymers with beta1,4 bonds which is not a substrate for amylase, which likes alpha1,4 bonds
What is the simplest insoluble fiber?
cellulose - it’s just repeating glucose units in beta1,4 linkages
What determines whether a fiber is soluble or not?
the different backbones and side chains affect solubility
Describe the structure of lignin?
a branched polymer of phenolic subunits, so there are phenol groups, which is somewhat odd for a carb
makes them undigestible by us AND bacteria
Lignins are found in what foods?
stems and seeds of fruits
What foods are high in cellulose?
bran, beans, nuts, root veggies and apples
How does hemicellulose differ from cellulose?
hemicellulose has the similar string of glucose molecules in beta1,4 linkages, but will also have various sugars on the backbone which cellulose doesn’t have
What foods are high in hemicellulose?
bran, whole grains and nuts
What are three examples of the side chains that hemicellulose will have?
arabinose
glucuronic acid
galactose
Describe the structure of pectin.
It is a branched polymer with a galacturonic acid backbone and various side chains including rhamnose, arabinose, xylose, fucose and galactose
What foods have pectins in abundance?
apples, strawberries
True or false: pectins are almost completely degraded by gut bacteria.
true
How are gums made?
they are secreted by plants to close wounds (so cut a tree, wait and collect)
What is the structure of gum arabic?
highly branched glucuronic acids