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Questions 18 - 25

Questions 18 - 25. Carbohydrate Disposal – early stuff. 18. Inadequate Digestion. Which of the following scenarios would MOST likely lead to flatulence (ie production of volatile short chain fatty acids and gases in the lower bowel)? Consumption of sucrose by someone with lactase deficiency

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Questions 18 - 25

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  1. Questions 18 - 25 Carbohydrate Disposal – early stuff

  2. 18. Inadequate Digestion • Which of the following scenarios would MOST likely lead to flatulence (ie production of volatile short chain fatty acids and gases in the lower bowel)? • Consumption of sucrose by someone with lactase deficiency • Consumption of amylopectin starch • Consumption of amylose starch • Consumption of dairy products pre-treated with lactase • Consumption of glucose in association with an amylase inhibitor lactase not involved with sucrose digestion 14 13 127 19 46 amylopectin easily digested by amylase much passes into lower bowel lactase will break down lactose and allow full absorption amylase not needed for glucose absorption

  3. 19. Blood Glucose Homeostasis • Which statement is CORRECT? • Two days of continual exposure to a blood glucose concentration of 10 mM will cause a coma • The reaction between proteins and glucose is not an enzyme catalysed process • Glycosylation does not affect the function of proteins • When blood glucose concentration is 5 mM, the rate of reaction between proteins and glucose is zero • Hyperglycemia causes problems faster than hypoglycemia lots of people walk around with moderate hyperglycemia 39 124 10 30 14 yes, no enzyme needed glycosylation most certainly DOES cause malfunction glycosylation is proportional to glucose concentration hypoglycemia is immediate, hyperglycemia several months or years

  4. 20. Glycemic Index • Which statement is INCORRECT? • It is not practical to measure the glycemic index of meat • The reference food used in glycemic index determinations is normally glucose • The glycemic index is a relative measure of the peak blood glucose concentration caused by a food • Legumes have a lower glycemic index than white bread • Sucrose has a lower glycemic index than amylopectin starch true statement – not enough carbs to give a 50 g dose 32 12 133 7 34 true statement – white bread sometimes used too not the peak, the area under the curve intuitively true (legumes contain amylose) strange but true – sucrose is half fructose which is not ‘glycemic’

  5. 21. GLUT-4 51 29 55 33 53 E A B GLUT-4 moves from Golgi to cell membrane after meal Glucose transporter number in response to a glucose load (that is completely cleared from the bloodstream in about 2 hours) C D The number of GLUT-4 transporters in the vesicles of the Golgi apparatus in muscle cells

  6. 22. GLUT-2 47 46 47 53 22 E A B GLUT-2 present all the time Glucose transporter number in response to a glucose load (that is completely cleared from the bloodstream in about 2 hours) C D The number of GLUT-2 transporters on the cell membrane of liver cells

  7. 23. GLUT-1 46 46 55 56 17 E A B GLUT-1 present all the time Glucose transporter number in response to a glucose load (that is completely cleared from the bloodstream in about 2 hours) C D The number of GLUT-1 transporters on the cell membrane of brain cells

  8. 24. Chemistry of Carbohydrates • Which statement is INCORRECT? • Anomeric forms of monosaccharides result from ring formation • Glyceraldehyde and dihydroxyacteone are both trioses • Interconversion of glucose and galactose occurs spontaneously in solution • Glucose, fructose and galactose are all hexoses • Conversion of glucose 6-phosphate to fructose 6-phosphate involves changing an aldose into a ketose true statement 12 14 94 73 23 they are oh no! need epimerases all six carbons glucose is aldose, fructose is ketose

  9. 25. Rate Limiting Steps • Which of the following enzymes is most likely to catalyse a ‘rate limiting step’ in a pathway • High Vmax enzyme that catalyses irreversible conversion of SP with the prevailing [S] being about the same as the Km of the enzyme. • High Vmax enzyme that catalyses reversible conversion of SP with the prevailing [S] being about the same as the Km of the enzyme • High Vmax enzyme that catalyses reversible conversion of SP with the prevailing [S] being about 2-fold the Km of the enzyme • Moderate Vmax enzyme that catalyses reversible conversion of SP with the prevailing [S] being about 2-fold the Km of the enzyme • Low Vmax enzyme that catalyses irreversible conversion of SP with the prevailing [S] being about 20-fold the Km of the enzyme Looking for slow, irreversible and saturated fast, irreversible, not saturated 55 4 22 2 130 fast, reversible, not saturated fast, reversible, not saturated ?fast, reversible, not saturated slow, irreversible, saturated

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