Nutritional Biochemistry - Twining Flashcards Preview

M2 GI/Nutrition > Nutritional Biochemistry - Twining > Flashcards

Flashcards in Nutritional Biochemistry - Twining Deck (25):
1

Which enzymes are secreted by the pancreas?

 

Which are secreted as zymogens and which are secreted as active enzymes?

Proteases, a-mylases, lipases, phospholipases, cholesterol esterases, RNAses, DNAses

 

The proteases are the only ones secreted as zymogens, which makes sense since you don't want them digesting the pancreas.

2

What are the three phases of enzyme secretion?

 

What are chemical and neural controls to release the enzymes?

  • Cephalic- controlled by the vagus/muscarinics and acetylcholine
  • Gastric- controlled by the vagus/muscarinics and acetylcholine as well as gastrin from the G cells
  • Intestinal- CCK from I cells and secretin from S cells 

3

What prompts the pancreas to release HCO3?

 

How is HCO3 concentrated into the duct lumen?

Acetylcholine from the vagus/muscarinics OR Secretin

 

  1. HCO3 is produced in the duct cells using Carbonic Anhydrase
  2. HCO3 is released into the lumen via the Cl/HCO3 exchanger
  3. A chloride gradient is maintained by the Cystic Fibrosis Transmembrane Regulator 

4

What steps are involved in fat digestion?

  1. Lingual lipase digests a small amount 
  2. Gastric lipase breaks down large fat droplets into smaller droplets
  3. In the duodenum, pancreatic lipase, co-lipase, and bile salts break down small droplets into micelles
  4. Micelles are absorbed across the microvilli

5

How are fats transported from the lumen of the duodenum/jejunum to the body?

Smaller fats (Glycerol, SCFA, and MCFA) diffuse through the enterocyte straight into the blood stream

 

All other fats are absorbed into the enterocyte as a micelle and reformed into cholesterol and fatty acids in the enterocyte.  They are then packaged as chylomicron/VLDL, excreted into the lymph, and sent to the liver.  

6

What is an endopepetidase?  

 

Which endopeptidases are found in the stomach?

 

Which are found in the small intestines? 

A pepetidase that cleaves in the center of a pepetide, not from the end

 

Pepsin

 

Trypsin, Chymotrypsin, Elastase

7

What is an exopepetidase?

 

Which exopeptidases are found in the stomach?

 

Which exopepetidases are found in the small intestine?

Pepetidase that cleaves from either the N- terminal or the -C terminal of the peptide

 

Trick question; there are none

 

Carboxypeptidases

8

How are the following enzymes activated?

 

Pepsinogen

Trypsinogen

Chymotrypsinogen

Proelastase

Procarboxypeptidase

  • Pepsinogen- HCl or pepsin
  • Trypsinogen- Enteropeptidase
  • Chymotrypsinogen- Trypsin 
  • Proelastase- Trypsin
  • Procarboxypeptidase- Trypsin

9

How are proteins absorbed from the intestine and distributed throughout the body?

  1. Peptides are broken down to tri-, di-, or mono-peptides in the lumen of the small intestine
  2. Tri-, di-, and mono- peptides are transported into the enterocytes by transporters
  3. Tri- and di- pepetides are broken down by tripeptidases and dipeptidases in the enterocyte
  4. Single amino acids are transported across the enterocytes, into the blood stream

10

How are carbohydrates transported across the enterocyte into the blood stream?

  1. SGLT1 cotransports 2Na to move galactose or glucose into the enterocyte
  2. GLUT5 transports fructose into the enterocyte
  3. GLUT2 transports sugars across the basal membrane into the bloodstream 

11

What is Vitamin B1/Thiamine used for in the body?

 

What does a deficiency result in?

 

Bonus: What is the USMLE sterotype for thiamine deficiency?

NADPH synthesis, neural membrane maintenance

 

  • Dry beriberi (polyneuropathy)
  • Wet beriberi (dilated cardiomyopathy)
  • Wernicke-Korsakoff syndrome (ataxia, psychosis)

 

Alcoholics

12

What is Vitamin B5/Pantothenic acid used for in the body?

 

What does a deficiency result in?

General metabolism (Coenzyme A) and fatty acid synthesis

 

(Attacks epithelial cells)

Dermatitis

Enteritis

Alopecia

Adrenal Insufficiency

13

What is Vitamin B2/Riboflavin used for in the body?

 

What does a deficiency result in?

Electron carrier (citric acid cycle, dehydrogenases)

 

Cheilosis

Dermatitis

Corneal neovascularization

14

What is Vitamin B3/Niacin used for in the body?

 

What does a deficiency result in?

 

Where can niacin be obtained other than the diet?

Basis of NAD and NADP

 

Glossitis

Pellagra

 

Synthesized from tryptophan (7 steps, extremely inefficient)

15

What is Vitamin B7/Biotin used for in the body?

 

What does a deficiency result in?

Carboxylase co-factor (holds CO2 in place)

 

Dermatitis

Alopecia

Enteritis

16

What is Vitamin B6/Pyridoxine used for in the body?

 

What does a deficiency result in?

Porphyrin synthesis, Glycogen degradation, Amino acid conversions

 

convulsions (lysine build-up)

Dermatitis

Peripheral Neuropathy

Sideroblastic Anemia

17

What is Vitamin B9/Folate used for in the body?

 

What does a deficiency result in?

Purine and SAM synthesis

 

Megaloblastic anemia

Neural Tube defects (preganant women)

18

What is Vitamin B12/Cobalamin used for in the body?

 

What does a deficiency result in?

TH4-Folate synthesis, Myelin synthesis

 

Megaloblastic anemia

Neural tube defects (pregnant women)

Demyelination

Neural Degeneration

19

Where are the B vitamins mostly absorbed?

 

What are the exceptions?

Duodenum/Jejunum

 

B12 is absorbed in the ileum

Biotin is absorbed in the large intestine

20

What is Vitamin C/Ascorbic Acid used for in the body?

 

What does a deficiency result in?

Antioxidant, Collagen synthesis

 

scurvy

bleeding (abnormal collagen)

21

What is Vitamin E/Tocopherol used for in the body?

 

What does a deficiency result in?

 

Where is it stored?

Antioxidant

 

Hemolytic Anemia

Muscle weakness

Demyelination

 

Liver, muscle, fat

22

What is Vitamin K/Phylloquinone used for in the body?

 

What does a deficiency result in?

 

What is the most common cause of deficiency?

Cogulation

 

Bleeding

 

Antibiotic use

23

What is Vitamin A/Retinoid used for in the body?

 

What does a deficiency result in?

Antioxidant, gene transcription, vision

 

Night blindness

Frequent infections

Scaly Skin

Corneal Degeneration

Alopecia

Osteoporosis

24

What is Vitamin D/Calciferol used for in the body?

 

What does a deficiency result in?

transcription factors, cell cycle, immune suppression, bone health

 

Rickets-children

Osteomalacia-adults

25

What are the following minerals used for in the body:

 

Iron

Zinc

Iodine

Copper

Fluoride

Selenium

Iron- heme, energy metabolism (enzyme co-factor)

Zinc- wound healing, spermatogenesis

Iodine- Thyroid hormones

Copper- Antioxidant, collagen formation, electron trasport

Fluoride- dental health

Selenium- antioxidant, thyroid function