Unit 2: carbohydrates + Lipids

Lec #1 LO1: List the participating and accessory organs involved in
digestion and absorption
2) Describe the structure and function of the individual organs
and the role of their secretory products
3) Explain the breakdown and transport mechanism of food
and resulting digestive products
4) List the sites of absorption for the various nutrients
5) Describe mechanisms for nutrient a

Lec #1

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

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Lec #2 LO2: describe the major classes of carbohydrates

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

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

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Lec #2 LO5: discuss carbohydrate intake in Canada

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

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

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

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

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

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

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

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

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

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

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

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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

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

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

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

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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

Which organ produces the digestive enzymes that are responsible for digestion of the majority of lipids?
A. Liver
B. Pancreas
C. Gallbladder
D. Small intestine

• The pancreas produces pancreatic lipase, the main enzyme responsible for digesting dietary fats (triglycerides → monoglycerides + free fatty acids).

• The liver produces bile, which emulsifies fat but does not digest it.

• The gallbladder stores and releases bile, but does not produce enzymes.

• The small intestine produces some enzymes, but not the main lipid-digesting ones; its role is mostly absorption.

• answer = B

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

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

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

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

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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

Which of the following enzymes participates in generation of
ATP through substrate-level phosphorylation in TCA cycle?
A. Succinate dehydrogenase
B. Malate dehydrogenase
C. Isocitrate dehydrogenase
D. Succinyl-CoA synthetase
E. Alpha-ketoglutarate dehydrogenase

• answer = D

Lec #7 LO1: Define the different categories of fiber.

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Lec #7 LO2: Name the different forms/classes of fiber.

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Lec #7 LO3: Describe the structure of different fibers.

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Lec #7 LO4: Explain why fiber is non-digestible.

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Lec #7 LO5: Describe the properties and physiological functions/effects of soluble and insoluble fibers.

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Lec #7 LO6: Give examples of dietary sources for the various fibers

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Lec #7 LO7: Identify different fibers on a random dietary supplement and describe the expected physiologic and metabolic effects after regular consumption of this product.

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Lec #7 LO8: Describe fermentability of fiber and the role of short‐chain fatty acids.

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Lec #7 LO9: Explain the difference between pre‐ and probiotics and their potential health impact.

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Lec #7 LO10: Describe the suggested metabolic effects of high fiber intake and how it could contribute to chronic disease prevention.

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Lec #7 LO11: List the dietary recommendations for fiber intake for adult men and women and give examples of fiber rich food sources.

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Lec #8 LO1: Describe the properties of lipids

Lec #8

Lec #8 LO2: List the various classes of lipids

Lec #8

Lec #8 LO3: Describe the characteristics of fatty acids and how they affect the physical property of fats

Lec #8

Lec #8 LO4: Give examples of dietary sources for the individual fatty acids

Lec #8

Lec #8 LO5: Describe the composition and function of triacylglycerol.

Lec #8

Lec #8 LO6: Describe the possible constituents of phospholipids and sphingolipids and their physiological role

Lec #8

Lec #8 LO7: Describe the occurrence of sterols, the functions of the steroids, and what cholesterol and vitamin D3 have in common

Lec #8

Lec #8 LO8: Describe the different stages of lipid digestion.

Lec #8

Lec #8 LO9: Explain why fat digestion has ‘special requirements’ compared to digestion of other macronutrients and how this is circumvented.

Lec #8

Lec #8 LO10: Explain the role of the different digestive enzymes, how their secretion is stimulated, and where they are active.

Lec #8

Lec #8 LO11: Understand the formation of bile acids, their secretion, function, and re-absorption.

Lec #8

Lec #8 LO12: Describe the role of gastric fat digestion and in what stages of life this could be of major importance

Lec #8

The daily recommended intake for fiber differs between
men and women because it is:
A. Based on the risk of cardiovascular
disease
B. Based on the physiologic tolerance
for high-fiber diets
C. Based on the carbohydrate
requirements
D. Based on the energy requirements

• Answer = D

Lec #9 LO1: Explain lipid absorption.

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Lec #9 LO2: Describe the digestion and absorption efficiency of different lipids.

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Lec #9 LO3: Explain how certain dietary factors can impact cholesterol absorption.

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Lec #9 LO4: Describe the functions and composition of the various lipoproteins.

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Lec #9 LO5: Explain the role and significance of apolipoproteins.

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Lec #9 LO6: Describe the tissue‐specific uptake of lipids.

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Lec #9 LO7: Explain the primary use of lipids after their uptake in peripheral tissues

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Lingual lipase contributes to lipid digestion. Which one
of the following statements about the characteristics of
lingual lipase is CORRECT:

A. Lingual lipase preferentially cleaves the
sn-2 fatty acids
B. Lingual lipase is not active in infants
C. Lingual lipase contributes to lipid
digestion in the mouth (10% of total
lipid digestion)
D. Lingual lipase preferentially cleaves
short- and medium chain fatty acids

• lingual lipase likes Sn-3, not sn2

• lingual lipase prefers short ad medium chain fatty acids

• answer = D

Which of the following statements is CORRECT?
A. Both soluble beta-glucans and insoluble lignin diminish absorption of lipids
B. Both soluble beta-glucans and insoluble cellulose inhibit cholesterol synthesis
C. Both soluble raffinose and insoluble lignin increase production of short- chain fatty acids in the gut
D. None of the above

• answer = A

Lec #10 LO1: Describe the development of atherosclerosis based on the lipid hypothesis.

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Lec #10 LO2: List the parameters that are measured in blood lipid profile.

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Lec #10 LO3: Describe which dietary and lifestyle factors may alter circulating lipoprotein levels and how.

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Lec #10 LO4: Explain how the dietary guidelines address the effects of the different types of fatty acids on blood lipid profile.

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Lec #10 LO5: Explain how dietary cholesterol may or may not influence the blood lipid profile.

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Lec #10 LO6: Describe the dietary and lifestyle factors influencing blood triacylglycerol concentrations

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What could explain a beneficial effect of saturated
fat from dairy on the lipid profile?
A. Food matrix
B. The amounts per serving size
C. Types of saturated fat
D. Absorption efficiency
E. All the above could be correct

• answer = E

Lec #10 LO7: Name the essential fatty acids for human metabolism.

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Lec #10 LO8: Describe why very long‐chain polyunsaturated fatty acids, such as EPA and DHA, are not considered “essential” fatty acids.

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Lec #10 LO9: Explain why regular fish consumption is being recommended.

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Lec #10 LO10: Describe the importance of the ratio of omega‐3 and omega‐6 fatty acids in our diet.

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Lec #10 LO11: Differentiate the functions of eicosanoids being formed of omega‐3 versus omega‐6 fatty acids.

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Lec #10 LO12: Describe how polyunsaturated fatty acids, and specifically omega‐3 and omega‐6 fatty acids, may impact cardiovascular disease risk

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Which lipoprotein is responsible for the transport of
cholesterol to peripheral tissues?
A. Chylomicron
B. VLDL
C. LDL
D. HDL

• answer = LDL

• answer = C

What is the carrier for short-chain fatty acids in
portal circulation?
A. Triacylglycerol
B. Cholesterol
C. Chylomicron
D. Albumin

• Short-chain fatty acids (and medium-chain fatty acids) are absorbed directly into the portal blood because they are relatively water-soluble.

• These fatty acids bind to Albumin (Option D) in the portal circulation for transport to the liver.

•  Triacylglycerol and Cholesterol are types of lipids and are transported within lipoproteins, not acting as carriers themselves.

• Chylomicrons are lipoproteins that transport long-chain fatty acids (after re-esterification into triacylglycerols) via the lymphatic system, not short-chain fatty acids in the portal vein.

• Answer = D

LO1: Describe lipid transport, distribution, and metabolism at fed state by naming the regulatory hormone and its actions, and describing how and to which tissues lipids are distributed upon absorption into enterocytes.

LO2: Explain the mechanisms of lipid uptake from the blood circulation to the individual tissues.

LO3: Describe lipid metabolism in liver and adipose tissue at fed state.

LO4: Explain lipid transport, distribution, and metabolism at postprandial/fasting state between tissues, with a focus on the liver and adipose tissues. Name the regulatory hormone(s) and regulated actions.

LO5: Explain the interrelationship between carbohydrate and lipid metabolism.

LO6: Define ketogenesis and describe the purpose and causes of this pathway.

LO7: Explain how and in which circumstances ketone bodies can serve as alternative source of energy.