⭐️59 - Digestion & Absorption of Lipids & Absorption of Vitamins & Minerals 🟢

LECTURE 59 POWERPOINT INFO

LECTURE 59 POWERPOINT INFO

Triglycerides (glycerol + 3 fatty acids)

Cholesterol

Phospholipids

What are the dietary lipids?

animal fats

Tallow, lard, and grease are _____

small intestine

Dietary lipids must be solubilized in the _____ for digestion and absorption

by churning (breaks lipids into small droplets and increasing SA and mixing lipids

How does the stomach initiate enzymatic digestion?

gastric lipase

Hydrolyzes ~10% of ingested TAG → glycerol + FFAs

slowly (allows pancreatic lipase time to digest

The stomach [quickly/slowly] empties chyme into the small intestine

emulsify

In the small intestine, bile salts _____ lipids = surround small lipid droplets to increase surface area

Pancreatic

_____ enzymes digest different lipids → lipase, colipase, cholesterol ester hydrolase, phospholipase A2

lipid-water interface

Colipase binds to lipase and allows it to digest at _____

cholesterol ester hydrolase

Hydrolyzes cholesterol ester → free cholesterol + FA + releases glycerol from triglycerides

phospholipase A2

-Activated by trypsin **

-Hydrolyzes phospholipids → lysolecithin + FA

micelles

Final products of lipid digestion of lipids in the SI, must now be solubilized in _____ for absorption

glycerol - hydrophilic and can be absorbed by Na+

Bile salts solubilize products within SI lumen as micelles (products in the center), except _____

brush-border

Micelles diffuse to _____ membrane of enterocyte, products released and diffuse into cell.

Bile salts do not diffuse into the cell***

re-esterified

Products are _____ inside enterocyte to form original compounds

chylomicrons- have cholesterol and triglycerides in the core, phospholipids and apoproteins around core

Re-esterified lipids are packaged with apoproteins to form _____

lymphatic capillaries

Chylomicrons (very large) are packaged in secretory vesicles and exocytosed across basolateral membrane into _____

steatorrhea (fatty feces)

A problem at any step of digestion or absorption of lipids can result in _____

pancreatic insufficiency (chronic pancreatitis)

_____ -> inadequate pancreatic enzymes, so TGs not digested

pancreatic enzymes

Some causes mentioned in class

-excessive H + secreation usually a tumor

Pancrease cannot secrete enough bicarbonate (pancreatitis)

If chyme is not neutralized (duodenal contents more acidic) in the small intestine, _____ become inactivated

micelle

-caused by inadequate bile salts recycling→ ideal resection →less bile salt recycling

No bile salts -> no _____ formation

Colipase

What enzyme is essential for proper function of pancreatic lipase

glycine; taurine

Bacterial overgrowth -> removal of _____ and _____ from bile salts

surface area

In any condition where enterocytes (intestinal cells) are reduced, there is less _____ for absorption of lipid products

abetalipoproteinemia

-Chylomicrons are not able to form and cannot transport from enterocyte→ lymphatic capillaries

Lack of Apo B causes _____

co-enzymes; co-factors

Vitamin absorption required as _____ or _____ for metabolic reactions

fat-soluble vitamins

Within SI lumen, _____ are incorporated into micelles for absorption

chylomicrons

Fat-soluble vitamins are incorporated into _____ for transport

Na+/dependent co-transport

Water-soluble vitamins are most absorbed via _____ in the small intestine

vitamin B12 (cobalamin)

Which water soluble vitamin requires intrinsic factor for absorption?

1. B12 released from food by pepsin

2. B12 binds to R proteins from salivary secretions

3. Proteases in SI degrade R proteins and release B12, which then binds intrinsic factor

4. B12/IF complex resists proteases, travels to ileum for absorption

What are the steps for B12 absorption?

Pancrease only

Intrinsic factors for vitamin absorption varies among species. Where do cats vit. Absorb. Other species are mostly stomach

active vitamin D

_____ is needed to absorb calcium in the small intestine

true

T/F - Calcium is absorbed by both passive and active transport mechanisms

Dietary vitamin D3 (cholecalciferol) →

25-hydroxycholecalciferol in liver →

1,25-dihydroxycholecalciferol in kidney

How is vitamin D activated?

calbindin D-28 K

Active vitamin D promotes synthesis of _____

rickets-young & osteomalacia- adults

Lack of active vitamin D or calcium -> ______

Micelles

In what form must lipid products be in order for absorption (into enterocytes) to occur

free iron (Fe2+); heme iron- bound to hemoglobin or myoglobin

Iron can occur as _____ or _____

true

T/F - The DMT-1 transporter in luminal membrane

lysosomal enzymes

Heme iron is digested into free iron by _____ inside enterocytes

apoferritin; ferroportin; transferrin

Free iron binds to _____ inside enterocytes for transport into blood via _____ → binds to _____ in plasma

transferrin; ferritin

Iron circulates bound to _____ and is stored as _____

LECTURE 59 PRACTICE QUESTIONS

LECTURE 59 PRACTICE QUESTIONS

B) Triglycerides, cholesterol, and phospholipids

In what forms can dietary lipids be provided for domestic animals?

A) Amino acids and triglycerides

B) Triglycerides, cholesterol, and phospholipids

C) Glucose and phospholipids

D) Amino acids and glucose

B) Animal fats, oils of vegetable or marine origin

Which of the following is a major source of dietary fat for domestic animals?

A) Carbohydrates

B) Animal fats, oils of vegetable or marine origin

C) Protein supplements

D) Plant fibers

B) Gastric lipase

What enzyme in the stomach initiates lipid digestion?

A) Pancreatic lipase

B) Gastric lipase

C) Colipase

D) Trypsin

B) 10%

What percentage of triglycerides (TAGs) does gastric lipase typically hydrolyze in the stomach?

A) 5%

B) 10%

C) 20%

D) 30%

B) To emulsify lipids for digestion

What is the primary role of bile salts in lipid digestion?

A) To break down proteins

B) To emulsify lipids for digestion

C) To transport glucose

D) To synthesize lipoproteins

C) Pancreatic lipase

Which pancreatic enzyme is responsible for breaking down triglycerides?

A) Phospholipase A2

B) Trypsin

C) Pancreatic lipase

D) Amylase

B) Binding to lipase to allow digestion at the lipid-water interface

Colipase assists lipase in lipid digestion by:

A) Increasing lipid surface area

B) Binding to lipase to allow digestion at the lipid-water interface

C) Emulsifying lipid droplets

D) Breaking down triglycerides into fatty acids

A) Cholesterol and free fatty acids

Which of the following is the final product of cholesterol ester hydrolase digestion?

A) Cholesterol and free fatty acids

B) Glycerol and fatty acids

C) Phospholipids and bile salts

D) Micelles

C) Original lipid compounds

After absorption, lipid products are re-esterified inside the enterocyte to form:

A) Bile salts

B) Cholesterol

C) Original lipid compounds

D) Micelles

A) Chylomicrons

What structure packages re-esterified lipids and apoproteins for transport into lymphatic capillaries?

A) Chylomicrons

B) Micelles

C) Colipase

D) Triglycerides

C. Vitamin K

Which vitamin requires micelles for absorption?

A. Vitamin C

B. Vitamin B12

C. Vitamin K

D. Vitamin B6

C. It requires intrinsic factor to form a complex

How does vitamin B12 differ in absorption compared to other water-soluble vitamins?

A. It requires an Na+/dependent co-transporter

B. It is absorbed in the jejunum

C. It requires intrinsic factor to form a complex

D. It is absorbed directly by enterocytes

C. Liver and then kidney

Where is vitamin D converted to its active form?

A. Liver only

B. Kidney only

C. Liver and then kidney

D. Small intestine

C. Active vitamin D

Which hormone is produced to enhance calcium absorption in the intestine?

A. Parathyroid hormone

B. Calcitonin

C. Active vitamin D

D. Thyroxine

B. DMT-1 transporter

What transporter is involved in iron absorption in the small intestine?

A. Na+/glucose cotransporter

B. DMT-1 transporter

C. H/K ATPase

D. Na+/K ATPase

C. Apoferritin

In the enterocyte, free iron binds to which protein for transport?

A. Transferrin

B. Ferritin

C. Apoferritin

D. Hemoglobin

A. Steatorrhea

Which of the following can result from the absence of bile salts in the intestine?

A. Steatorrhea

B. Increased absorption of fats

C. Decreased iron absorption

D. Elevated gastric acid production

B. Chylomicrons

In lipid absorption, re-esterified lipids combine with apoproteins to form:

A. Micelles

B. Chylomicrons

C. Bile salts

D. Lipoproteins

C. They degrade R proteins to release vitamin B12

What is the role of proteases in vitamin B12 absorption?

A. They bind vitamin B12 to bile salts

B. They release vitamin B12 from food in the stomach

C. They degrade R proteins to release vitamin B12

D. They form a complex with vitamin B12 and intrinsic factor

C. Abetalipoproteinemia

Which condition is caused by the lack of Apo B?

A. Iron deficiency anemia

B. Steatorrhea

C. Abetalipoproteinemia

D. Pernicious anemia