Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

NUTR 301 > Carbohydrates Classification, Digestion and Absorption > Flashcards

Carbohydrates Classification, Digestion and Absorption Flashcards

1
Q

Hydrated Carbon Compounds

A
  • H to O ratio of 2 to 1 (like water)
  • the reaction for hydrating carbons is photosynthesis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

Glucose is also known as (5)

A
  • hexose
  • monosaccharide
  • simple sugar
  • available carbohydrate
  • nutritive sweetener
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

RDA/AI of carbohydrates for majority of population (g/day)

A

130 g/day

RDA/AI denotes the essential minimal amount required for brain function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

RDA/AI of fibre for majority of population (g/day)

A

19-38 g/day
- 38g for males (14-50y)
- 26g for females (9-50y)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Carbohydrate AMDRs for children (1-3), children (4-18) and adults

A

45-65% of energy intake
- based on total energy requirement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Aldose & Ketose

A

Aldose
- (-ose), contains 1 aldehyde on carbon 1

Ketose
- (-ulose), contains 1 ketone on C 2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

examples of mono, di, oligo and polysaccahrides

A
  • mono: glucose, fructose, galactose
  • di: lactose, sucrose, maltose
  • oligo: raffinose, stachyose
  • poly: starch, glycogen, dietary fiber
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

structure of disaccharides (sucrose, maltose, lactose)

A
  • sucrose: glucose + fructose
  • maltose: glucose + glucose
  • lactose: galactose + glucose

sucrose is aka table sugar

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Who discovered the reactivity of sugars?

A

Louis Camille Malliard

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What causes the build up of advanced glycation end products (AGEs) in collagen-rich tissues, joints, blood vessel walls and lens?

A

caused by reactions between sugars and proteins

  • aldoses and ketoses can react with primary and secondary amines to form N-glycoside
  • dehydration (malliard), then a rearrangement occurs at C1 & 2 to form an aminoketose (highly reactive)
  • when this compound reacts with amine groups on proteins it can result in cross-linked proteins

the reactivity of glucose with proteins serves as a marker for how glucose has affected tissues over time - 2-3 fold increase in glycoproptein in patients with diabetes mellitus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

reducing vs non reducing sugars

A

reducing: have an anomeric carbon available (lactose, maltose)

non reducing: both anomeric carbons are involved in the glycosidic bond (sucrose, trehalose)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why does dietary fiber remian in the human gastrointestinal tract?

A

humans lack the digestive enzymes that can hydrolyze β-1,4 glycosidic bonds
- some enzymes from colonic bacteria may degrade fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Polysaccharides

A

polysaccharides can be linear or branched

Digestible Polysaccharides:

1) Amylose:

  • alpha 1-4 linkages
  • straight chain polymer of D glucose units
  • makes up 20% of starch
  • less soluble in water (forms a helix)
  • can be hydrolyzed (β/⍺ amylases)
  • no gel formation

2) Amylopectin:

  • alpha 1-4 & alpha 1-6 GL
  • branched chain polymer of D-glucose units
  • makes up 80% of starches
  • more soluble in water
  • cannot be hydrolyzed by enzymes completely
  • forms a gel when hot water is added

Non-digestible polysaccharides

  • aka dietary fiber
  • eg. cellulose: has β 1-4 and hydrogen bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Two major steps of carbohydrate digestion

A

1) intraluminal digestion (amylases)

  • initial: salivary ⍺ amylases then pancreatic amylases
  • salivary amylases deactivated in stomach by acids
  • pancreatic juices neutralize acid and hydrolysis continues (inter luminal hydrolysis)

2) membrane digestion (brush border glycohydrolases

  • maltose, maltotriose, trisaccharides, oligos and ⍺-limit dextrins require further breakdown
  • how quickly you can break carbs down into their single units determines how quickly you get a glucose response

alpha limit dextrins: branched oligosaccharides that result from the incomplete hydrolysis of amylopectin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Digestion of complex polysaccharides

A

mouth: amylose and amylopectin get broken down into dextrins by salivary ⍺ amylases (amylopectin still contains branches)
alpha 1,4 bonds only

stomach: no further digestion of dextrins occurs

small intestine: dextrins get broken down into maltose (glux2), and limit dextrins (amylopectin) by pancreatic ⍺ amylases.
alpha1,4 bonds only

brush border: maltose is hydrolyzded to free glucose by maltase. limit dextrins are hydrolysed to free glucose by ⍺-dextrinase
alpha 1,6 bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

fructose: sources, glycosidic bond, membrane enzymes and products

A
  • fruits & honey
  • none
  • none
  • fructose
16
Q

glucose: sources, glycosidic bond, membrane enzymes and products

A
  • fruit, honey, grapes
  • none
  • none
  • glucose
17
Q

amylopectin: sources, glycosidic bond, membrane enzymes and products

A
  • potatoes, rice, corn, bread
  • ⍺-1,4, ⍺-1,6
  • maltase, glucoamylase, isomaltase
  • glucose
18
Q

amylose: sources, glycosidic bond, membrane enzymes and products

A
  • potatoes, rice, corn, bread
  • ⍺-1,4
  • maltase, glucoamylase
  • glucose
19
Q

sucrose: sources, glycosidic bond, membrane enzymes and products

A
  • table sugar & desserts
  • ⍺-1,2
  • sucrase
  • glucose & fructose
20
Q

trehalose: sources, glycosidic bond, membrane enzymes and products

A
  • young mushrooms
  • ⍺-1,1
  • trehalase
  • glucose
21
Q

lactose: sources, glycosidic bond, membrane enzymes and products

A
  • milk & milk products
  • β-1,4
  • lactase
  • glucose & galactose
22
Q

Digestion: absorption of monosaccharides

A
  • transported processes occur on the apical side of the small intestine epithelial cells
  • hepatic portal vein transports the absorbed nutrients to the liver

Glucose/Galactose:

  • carrier-dependant, energy-requiring active transport
  • sodium dependant

Fructose:

  • facilitated diffusion - doesn’t illicit a GI

Rate of CHO assimilation:

  1. enzymatic hydrolysis at brush border
  2. transport of sugar
    expression of GLUT2 controls the last phase of GI (entrance of glucose into bloodstream)

transport accross the epithelium is the rate-limiting step for carbohydrate digestion

23
Q

Malabsorption

A
  • lactose from milk requires lactase
  • undigested lactose gets fermented
  • hydrogen breath test/stool acidity test
  • ## hydrolysis defect not absorption defect
24
Q

why do we need more enzyme expression for oligo-/polysaccharides

A
25
Q

CHO digestive enzymes and transporters

A

SGLT1:

  • located on the apical membrane
  • requires energy (Na+ gradient dependant) to shuttle glucose into the cell
  • expressed in low and high concentrations of glucose

GLUT5:

  • located on the apical membrane
  • passively transports fructose into the cell
  • expressed in low and high fructose concentration

GLUT2:

  • located on basal membrane and on apical (when hexose concentration is high) - GLUT2 expression is maximal within 10m after consuming a sugar-rich meal
  • passively transports both fructose and glucose into the cell, as well as out of the cell into the bloodstream

NUTR 301 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions