Nutritional Biochemistry - Twining Flashcards Preview

M2 GI/Nutrition > Nutritional Biochemistry - Twining > Flashcards

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

Which enzymes are secreted by the pancreas?

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

A

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
Q

What are the three phases of enzyme secretion?

What are chemical and neural controls to release the enzymes?

A
  • 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
Q

What prompts the pancreas to release HCO3?

How is HCO3 concentrated into the duct lumen?

A

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
Q

What steps are involved in fat digestion?

A
  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
Q

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

A

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
Q

What is an endopepetidase?

Which endopeptidases are found in the stomach?

Which are found in the small intestines?

A

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

Pepsin

Trypsin, Chymotrypsin, Elastase

7
Q

What is an exopepetidase?

Which exopeptidases are found in the stomach?

Which exopepetidases are found in the small intestine?

A

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

Trick question; there are none

Carboxypeptidases

8
Q

How are the following enzymes activated?

Pepsinogen

Trypsinogen

Chymotrypsinogen

Proelastase

Procarboxypeptidase

A
  • Pepsinogen- HCl or pepsin
  • Trypsinogen- Enteropeptidase
  • Chymotrypsinogen- Trypsin
  • Proelastase- Trypsin
  • Procarboxypeptidase- Trypsin
9
Q

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

A
  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
Q

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

A
  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
Q

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?

A

NADPH synthesis, neural membrane maintenance

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

Alcoholics

12
Q

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

What does a deficiency result in?

A

General metabolism (Coenzyme A) and fatty acid synthesis

(Attacks epithelial cells)

Dermatitis

Enteritis

Alopecia

Adrenal Insufficiency

13
Q

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

What does a deficiency result in?

A

Electron carrier (citric acid cycle, dehydrogenases)

Cheilosis

Dermatitis

Corneal neovascularization

14
Q

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?

A

Basis of NAD and NADP

Glossitis

Pellagra

Synthesized from tryptophan (7 steps, extremely inefficient)

15
Q

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

What does a deficiency result in?

A

Carboxylase co-factor (holds CO2 in place)

Dermatitis

Alopecia

Enteritis

16
Q

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

What does a deficiency result in?

A

Porphyrin synthesis, Glycogen degradation, Amino acid conversions

convulsions (lysine build-up)

Dermatitis

Peripheral Neuropathy

Sideroblastic Anemia

17
Q

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

What does a deficiency result in?

A

Purine and SAM synthesis

Megaloblastic anemia

Neural Tube defects (preganant women)

18
Q

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

What does a deficiency result in?

A

TH4-Folate synthesis, Myelin synthesis

Megaloblastic anemia

Neural tube defects (pregnant women)

Demyelination

Neural Degeneration

19
Q

Where are the B vitamins mostly absorbed?

What are the exceptions?

A

Duodenum/Jejunum

B12 is absorbed in the ileum

Biotin is absorbed in the large intestine

20
Q

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

What does a deficiency result in?

A

Antioxidant, Collagen synthesis

scurvy

bleeding (abnormal collagen)

21
Q

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

What does a deficiency result in?

Where is it stored?

A

Antioxidant

Hemolytic Anemia

Muscle weakness

Demyelination

Liver, muscle, fat

22
Q

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

What does a deficiency result in?

What is the most common cause of deficiency?

A

Cogulation

Bleeding

Antibiotic use

23
Q

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

What does a deficiency result in?

A

Antioxidant, gene transcription, vision

Night blindness

Frequent infections

Scaly Skin

Corneal Degeneration

Alopecia

Osteoporosis

24
Q

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

What does a deficiency result in?

A

transcription factors, cell cycle, immune suppression, bone health

Rickets-children

Osteomalacia-adults

25
Q

What are the following minerals used for in the body:

Iron

Zinc

Iodine

Copper

Fluoride

Selenium

A

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