Unit 2: carbohydrates

Lec #2 LO1: define the role of carbohydrates in human nutrition

meow

Lec #2 LO2: describe the major classes of carbohydrates

meow

Lec #2 LO3: define carbohydrates and explain the structures of the different carbohydrate classes and their individual units

meow

Lec #2 LO4: list food sources for individual carbohydrate classes

meow

Lec #2 LO5: discuss carbohydrate intake in Canada

meow

Lec #2 LO6: describe organs and specific enzymes involved in carbohydrate digestion

meow

Lec #2 LO7: explain why some carbohydrates cannot be digested

meow

Lec #3 LO1: Describe in what form carbohydrates are absorbed.

meow

Lec #3 LO2: Describe how the monosaccharides glucose, galactose and fructose are absorbed in the small intestine and reach the blood stream.

meow

Lec #3 LO3: Explain the corresponding absorption and transport mechanisms and why those mechanisms are used.

meow

Lec #3 LO4: Describe the structure and role of glucose transporters and list their major sites of expression

meow

Lec #3 LO5: Describe the role of blood glucose.

meow

Lec #3 LO6: Describe acute and long-term parameters of blood glucose concentrations

meow

Lec #3 LO7: Explain acute and chronic symptoms of elevated and low blood glucose levels

meow

Lec #3 LO8: Describe regulatory compounds and pathways involved in blood glucose control

meow

Lec #3 LO9: Explain glycemic index and glycemic load and how they are calculated. Discuss the use of these two indicators

meow

The digestion of disaccharides mainly occurs in
the:
A. Mouth
B. Stomach
C. Lumen of small intestine
D. Brush border membrane

• digestion of disaccharides mainly occurs in the lumen of small intestine

• answer = C

The enzyme that digests the majority of ingested
complex carbohydrates is:
A. Salivary alpha 1-4 amylase
B. Pancreatic alpha 1-4 amylase
C. Duadenal alpha 1-4 amylase
D. Salivary alpha 1-6 amylase

• The enzyme that digests the majority of ingested complex carbohydrates is Pancreatic alpha 1-4 amylase (Option B).

• Salivary alpha 1-4 amylase initiates digestion in the mouth, but pancreatic amylase is responsible for the bulk of starch digestion in the small intestine.

• answer = B

Free sugars are:
A. Simple sugars added to foods during
production, cooking or consuming
B. Simple sugars naturally present in
honey, syrups, and fruit juices
C. Both A and B are correct

• answer = C

Lec #4 LO1: Name the production and disposal pathways of glucose, and explain which hormones regulate these pathways in the different stages of the fed-fast cycle

meow

Lec #4 LO2: Explain how cells turn glucose into energy in dependence of the cell type and oxygen supply

meow

Lec #4 LO3: Name the regulatory steps (with the specific intermediary products and enzymes) of glycolysis and TCA cycle pathways

meow

Lec #4 LO4: Explain how and in which format energy is produced from carbohydrates and other macronutrients.

meow

Which transporter is involved in active transport of glucose
into enterocytes (=mucosal cells=absorptive cells)?
A. SGLT1
B. GLUT5
C. GLUT2
D. GLUT4

• SGLT1 = involved in active transport

• GLUT 5,2,4 = involved in facilitated diffusion

• answer = A

Boiled red potatoes have very high (above 80 in reference to
glucose) Glycemic Index (GI) when:
A. Are consumed hot
B. Are consumed cold
C. Always, no matter if hot or cold

• when consumed cold, the starches (complex carbohydrate - polysaccharide) reform

• answer = A

Compared to glucose, fructose is absorbed by facilitated
diffusion only and does not require active transport into the
intestinal cell. This is because:
A. Fructose has a much higher affinity to GLUT5 than glucose has to GLUT2.
B. Fructose can be transported to the intestinal cell independent of the concentration gradient.
C. The concentration of fructose in the intestinal cell is always lower than in the intestinal lumen.
D. Fructose is phosphorylated in the intestinal cell to allow
continuous absorption of fructose molecules.

• D = if fructose is phosphorylated it cannot leave into the bloodstream

• facilitated diffusion requires the use of a [ ] gradient

• answer = C

Lec #5 LO1: Describe the hexosemonophosphate shunt and name the key products. Explain why the pathway is more active in certain tissues

meow

Lec #5 LO2: Explain gluconeoaenesis and how it is regulated. Name precursors for glucose formation

meow

Lec #5 LO3: Describe the structure, function, and distribution of glycogen

meow

Lec #5 LO4: Explain the formation and breakdown of olvcoaen and describe how those pathways are regulated.

meow

Glucokinase is present in the ______ where it ________
glucose and is _________ by the product of the catalyzed
reaction.
A. Muscle, phosphorylates, inhibited
B. Liver, phosphorylates, NOT inhibited
C. Muscle, dephosphorylates, NOT inhibited
D. Liver, phosphorylates, inhibited
E. Muscle, phosphorylates, NOT inhibited

• glucokinase is the enzyme that phosporylates glucose in the liver

• it is NOT inhibited by its products

• answer = B

Glycogen stored in muscle does not contribute directly to
blood glucose levels because:
A. Muscle lacks glucose-6-phosphatase to
convert glucose-6-phosphate to free
glucose
B. Muscle lacks glucokinase to convert
glucose-6-phosphate to free glucose
C. It is not true, glycogen in muscle
contributes to blood glucose levels

• Review

  • glucokinase is an enzyme in the liver that phosphorylates glucose, it does not make a free glucose

  • muscle only uses glycogen stores for itself

  • phosphatases remove phosphate groups via hydrolysis

  • glucose-6-phosphatase is only present in liver and kidney

• answer = A

o