Carbohydrates Flashcards
What is the general formula for an unmodified monosaccharide?
CnH2nOn
n =3 to 6
What type of carbohydrate sugar is this?
Aldose sugar “-ose”
What type of carbohydrate sugar is this?
Ketose Sugar “-ulose”
Is Fructose a ketose or an aldose sugar?
Ketose; it is the exeption to the rule that ketoses end in “-ulose”
Name this monosaccharide
Galactose
Name this monosaccharide
Glucose
Name this monosaccharide
Mannose
Name this monosaccharide
Fructose
Define Stereoisomers
- same chemical formula but differ in position of (-OH) group on one or more of thier asymmetric carbons
- ex: fructose, glucose, mannose, and galactose are stereoisomers, each having same chemical formula C6H12O6
Epimers
Stereoisomers that differ in the position of (-OH) group at only one specific carbon atom
- Ex: glucose and galactose are C-4 epimers; glucose and mannose are C-2 epimers
Describe this relationship
Glucose and Mannose are C-2 epimers
Define Enantiomers
Mirror images of each other
- D=dexter (-OH group off C-5 is on the right)
- L=Laevus (-OH group off C-5 is on the left)
- Sugars assumed to be in D form
How do you number these carbons
How do you number these carbons
What process is this
Mutarotation
- Spontaneous and non-enzymatic
What class of anomers is this and is it more or less commonly found?
Alpha anomer of glucose. Found 36% due to steric hinderance
What class of anomer is this and is it seen more or less?
Beta anomer; seen 64% due to less steric hinderance
Glycation
Non-enyzmatic reaction where a single, LINEAR glucose can get covalently linked to a protein in a nonspecific and non-reversible manner
- Sugar + Protein = glycated protein
How does glycation affect a proteins function?
Increased level of glycation on a protein is linked to a DECREASE in function of the protein
What does hemoglobin A1c test (HbA1c) measure?
The level of glycated hemoglobin
- Diabetic patients -> high glucose -> more protein glycation -> greater loss of protein structure/function -> inflammation and disease
What type of monosaccharide derivative is this?
Oxidized sugars (Sugar acids)
- Purpose = increase polarity
- Ex: Glucose is oxidized to Glucuronic Acid
What type of monosaccharide derivative is this?
Amino sugar
What is the monosaccharide derivative listed (on the right)?
Reduced sugar (sugar alcohols)
Oxidation
- Loss of electrons
- alochol -> aldehyde -> acid (increasing oxidation)
Reduction
- Gain of electrons
- Acid -> Aldehyde -> Alcohol (becoming more reduced)
- Ex: glucose is reduced to Sorbitol
Glycosaminoglycans
- Linear polymers of repeating disaccharides (50-150 subunits)
- Negatively charged
- Form ground substance of extracellular matrix
Disaccharides
- The linkage of two monosaccharides via glycosidic bonds
- Dehydration reaction
Sucrose is composed of which two monosaccharides?
Glucose and Fructose
Lactose is composed of what two monosaccharides?
Glucose and Galactose
Maltose is what composed of what two monosaccharides?
Glucose and Glucose
Starch exists in what two polymer forms?
- Amylose (linear polymer: a-1,4-glycosidic bonds)
- Amylopectin (linear [a-1,4-glycosidic bonds] AND branched polymer [a-1,6-glycosidic bonds]
Can dietary fiber be digested by human enzymes?
- Insoluble fiber: Can’t be degraded by human enzymes or colonic bacteria
- Soluble fiber: Can’t be degraded by human enzymes but can be fermented by colonic bacteria
Starch digestion first occurs where and by what enzyme?
Salivary Amylase (breaks a-(1-4) bonds) in the mouth
What happens to salivary a-amylase when it hits the stomach?
It is inactivated by the acid
In carbohydrate digestion, what two things does the pancrease secrete when the chyme enters the small intestine?
- HCO3- to neutralize acid from the stomach
- Pancreatic a-amylase
Where do dissaccharides become digested into monosaccharides in carbohydrate digestion?
This final digestive process occurs at the enterocytes of the upper jejunum via disacchridases
In what form will intestinal cells of duodenum and upper jejunum absorb carbohydrates?
Monosacchardies ONLY
Describe how Abnormal lactose metabolism (e.g lactase deficiency) can result in osmotic diarrhea?
- Lactose is osmotically active: when it reaches the small intestine, water is drawn in
- Lactose has to be fermented by bacteria and so water is not reabsorbed
What oral sugar tolerance test can be used to determine a glycolytic enzyme deficiency?
Measurement of H2 gas in the breath
- H2 released in bacterial fermentation; levels of H2 reflect severity of malabsorption
What are the two types of fructose carries/transporters in enterocytes for fructose absorption?
- Glucose-independent
- Glucose-dependent (main transporter for most people)
Fructose Malabsorption
- When is it most seen?
- What type of food has high fructose content?
- Effect?
- Most seen when fructose exceeds glucose
- Juice
- osmotic diarrhea
Abnormal absorption of sorbitol
- what foods have high content of sorbitol?
- When sorbitol is ingested with what monosaccharide, malabsorption is more than additive?
- apples, pears, peaches
- Fructose and Sorbitol are ingested together
Low Glycemic index represents what time course of postprandial glucose concentration?
Gradual rise, followed by a slow fall in blood glucose
A high glycemic index indicates what time course of postprandial glucose concentration?
Rapid rise, followed by a steep fall in blood glucose
