Carbohydrates & Lipids

Question 1

What two sugars compose Sucrose?

What type of sugar is Sucrose?

Answer 1

Glucose and Fructose

Table sugar

Question 2

What two sugars compose Lactose?

What type of sugar is Lactose?

Answer 2

Glucose and Galactose

Milk sugar

Question 3

What two sugars compose Maltose?

What type of sugar is Maltose?

Answer 3

Glucose and Glucose

Digested starch

Question 4

Name three common examples of polysaccharides.

Answer 4

Starch, Glycogen and Dietary fiber/cellulose

Question 5

What two forms do starch and glycogen exist in?

Answer 5

• Amylose: linear a-1,4-glycosidic bonds

- Amylopectin: linear a-1,4-glycosidic bonds AND branched a-1,6-glycosidic bonds

Question 6

Is starch made up more of amylose or amylopectin?

Is starch or glycogen more dense?

Answer 6

Primarily amylopectin

Glycogen is more dense because its structure branches more frequently than starch

Question 7

List the general steps of carbohydrate digestion.

Answer 7

1. Salivary amylase breaks down the a-1,4-glycosidic bonds
2. In small intestine, content is neutralized by bicarbonate (from the pancreas) and pancreatic a-amylase continues the process
3. Disaccharides are digested at the upper jejunum
4. Monosaccharides are absorbed in the duodenum and upper jejunum

Question 8

What is the consequence of lactase deficiency and what is the symptomatic result?

Answer 8

There is a deficiency of lactase causing lactose to remain in its original form - water is drawn in by the osmotically-active lactose but because there is a lack of lactase, the water is not expelled and leads to an excess of water in the body

The result of lactase deficiency is osmotic diarrhea

Question 9

What is the diagnostic test used for carbohydrate intolerance? Explain it.

Answer 9

Hydrogen Breath Test

Measures H2 gas in the breath, reflecting the amount of ingested carbohydrates not absorbed - higher peak = worse malabsorption

Question 10

Experimentally, what is often seen in patients with fructose malabsorption?

Answer 10

The fructose levels will exceed the glucose levels; also seen with fructose and sorbitol

1:1 of fructose:glucose is normal

Question 11

What is linoleic acid?

Answer 11

Omega-6 FA

Question 12

What is linolenic acid?

Answer 12

Omega-3 FA

Question 13

Is linoleic acid or linolenic acid a precursor for AA?

Answer 13

Linoleic acid

Question 14

What composes Glycerolphospholipids?

Answer 14

• Choline & Phosphate (hydrophilic)
• Glycerol
• Two fatty acids (hydrophobic)

Question 15

What composes Sphinomyelins?

Answer 15

• Choline & Phosphate (hydrophilic)
• Sphingosine
• One fatty acid (hydrophobic)

Question 16

What composes Glycosphingolipids?

Answer 16

• Galactose (hydrophilic)
• Sphingosine
• One fatty acid (hydrophobic)

Question 17

What composes Cholesterol?

Answer 17

• Head group (hydrophilic)
• Ring structure
• Tail (hydrophobic)

Question 18

List the general steps of lipid digestion.

Answer 18

1. Mechanical breakdown of products in mouth
2. Absorption of digestion products into intestinal enterocytes
3. Re-synthesis of lipids in the enterocyte
4. Transport of lipids from the enterocyte to tissues via chylomicrons

Question 19

What hormones are utilized to break down lipids in the first step of digestion? Where are these

Answer 19

• Lingual lipase from the mouth and gastric lipase from the stomach
• CCK (cholecystokinin) and secretin from the small intestine

Question 20

What does CCK stimulate the release of during digestion?

Answer 20

• Bile salts from the gallbladder

- Pancreatic enzymes from the pancreas

Question 21

What does secretin stimulate the release of during digestion?

Answer 21

Bicarbonate from the pancreas, neutralizing the acidic chyme in the small intestine

Question 22

Where are bile salts produced and stored? What are the two structures that bile salts can be found as, and what is each structure required for?

Answer 22

• Produced in the liver
• Stored in the gallbladder
• Emulsion droplets: fat digestion
• Mixed micelles: fat absorption

Question 23

What step of lipid digestion are mixed micelles involved in? Explain this step in detail.

Answer 23

Absorption of lipids

Mixed micelles serve as a carrier protein for the long FA chains to cross the plasma membrane

Mixed micelles are disc-shaped clusters of amphipathic lipids (hydrophobic head on outside and hydrophilic tail on inside); they are soluble in the intestinal lumen where they are broken down and the lipids are absorbed by the microvilli surface (micelle itself is not absorbed)

Question 24

What is packaged into chylomicrons? What step of lipid digestion are chylomicrons involved in?

Answer 24

TAGs and cholesteryl esters

Re-synthesis of lipids in the enterocyte (allow the fat-soluble vitamins (TAGs and CEs) to be carried from the intestinal mucosal cell through the lymphatic system

Question 25

What happens to short- and medium-chain FAs?

Answer 25

They are not resynthesizes into TAGs - instead, they are transported through the enterocyte into the blood where they bind to albumin and go directly to the liver for energy metabolism