UNIT 5: CARBS Flashcards
Carbohydrates are a major _______, but do not ______.
major source of energy/fuel (~50%)
do not contain essential nutrients
Carbohydrates are not an essential _____ but are an essential ____.
nutrient
metabolite
- i.e. blood glucose is an essential metabolite but can be obtained from dietary protein
Sugars must possess:
- aldehyde or ketone functional group
- hydroxyl groups
Sugars are joined together by ______
glycosidic bonds
Anomeric carbon is the carbon with…
the carbonyl group
- carbon closest to
Fischer projection L vs D is defined by?
- highest chiral carbon
- direction of carbonyl group
- OH to left = L
- OH to right = D
Glucose in aqueous solution equilibrium is…
1/3 alpa-D-glucose, 2/3 beta-D-glucose
Alpha is when ____ points ___ and Beta is when it points ____.
alpha: -OH points down
beta: -OH points up
Which carbon becomes the anomeric carbon when cyclized?
The carbonyl carbon.
it is attacked by the -OH of highest chiral carbon.
Glucose is a ____ while Fructose is a ____
- glucose is aldose
- fructose is ketone
Fructose is a ketone or hemi-ketal ring
Plant cells use ____,
Grain cells use _____,
Muscle cells use _____.
Plant: beta-D-glucose
Grain: alpha-D-glucose
Muscle-alpha-D-glucose
The disacchardes: Sucrose Lactose Maltose are made of...
Sucrose = alpha glucose + beta fructose Lactose = alpha or beta glucose + beta galactose Maltose = alpha glucose + alpha or beta glucose
Of the 3 disacchardies, which are the reducing sugars and which are the non-reducing sugars?
Reducing: lactose and maltose
- they have hemiacetal that can reduce reduce aldehyde to continue link
Non-reducing: sucrose, both anomeric carbons used to form glycosidic bond so cannot reduce
Non reducing sugars are ______ chemically reactive than reducing sugars.
Non-reducing sugars are less reactive, and need to be digested to monosacharides before absorbed
Homopolysaccharides are ____ abundant than Heteropolysaccharides
more abundant
Plants produce 2 types of starches:
- amylose -> a-1-4 glucose (linear)
- amylopectin -> a-1-6 glucose (for branching)
Starch in plants is like _____ in humans.
Glycogen
Which is more dense? Starch or glycogen?
Glycogen
- dense branching
- this forms granules
- prevents glycogen accumulation from disrupting muscle and liver cells
Compare soluble and insoluble fibres.
Insoluble fibres: cellulose, hemicellulose, lignin - remains intact through GI tract (only some fermentation) - does not dissolve in water Soluble fibres: pectins, gums, mucilages - forms a gel - ferments in colon -> VFA - does dissolve in water
A fibre is digestible if….
- the fibre is soluble enough that enzymes can attack it
2. enzymes are present
What is so interesting about resistant starch?
- we have enzymes to digest starch
- tight granule structure
- goes to colon for fermentation
What happens to insoluble fibres with wetted surface?
fermentation
Soluble fibres have a _____ glycemic index.
lower glycemic index
- slow appearance of glucose in blood stream
In terms of transit time, compare insoluble vs soluble fibres.
Insoluble fibres have a low transit time so promotes bowel movements.
Soluble fibres have increased transit time and slow stomach emptying, slowing nutrient absorption.
Cellulose is linked by
beta bonds, beta-1-4 glucose
