Nutritional Biochemistry Flashcards
(43 cards)
1
Q
Pancreatic Secretion
- Zymogens — Proproteases:
- Active enzymes:
- Ions:
A
-
Zymogens – Proproteases:
- Trypsinogen
- Chymotrypsinogen
- Proelastase
- Procarboxypeptidases
-
Active Enzymes:
- α-Amylase
- Lipases
- Co-lipase
- Phospholipases
- Cholesterol esterases
- RNAses
- DNAses
-
Ions:
- HCO3-
2
Q
Pancreatic enzyme secretion controlled at three stages:
A
-
Cephalic
- Acetylcholine
-
Gastric
- Acetylcholine
- Gastrin
-
Intestinal
- Cholecystokinin (CCK)
- Secretin
3
Q
What controls HCO3- secretion by pancreatic duct cells?
A
- Acetylcholine
- Secretin
4
Q
List the different types of lipases:
A
- Lingual
- Gastric
- Pancreatic
5
Q
Pancreatic lipase:
- Secreted into ….
- Active in ….
- What is required along with pancreatic lipase?
A
- Secreted into the duodenum
- Active in lumen of duodenum
- Requirements:
- Bile salts required
- Requires a colipase
6
Q
- What are the lipid enzymes found in the intestinal absorptive cells?
- Where and how does absorption of lipids occur?
- How does transport of lipids occur?
A
-
Enzymes:
- Phospholipases
- Cholesterol esterases
-
Absorption
- Direct
- Duodenum and jejunum
- Micelles
-
Transport
- Chylo-microns
- VLDL
7
Q
What is the function of proteases?
A
Hydrolytically cleave peptide bonds
8
Q
What are endopeptidases?
- Stomach:
- Duodenum and jejunum:
A
Cleave in center of proteins and peptides
-
Stomach – Pepsinogen – Chief Cells
- Activated by acid and auto-activated to pepsin
-
Duodenum and jejunum enzymes:
- Synthesized and secreted by α-cells of the pancreas
- Trypsinogen activated in the duodenum by epithelial enteropeptidase (enterokinase)
- Chymotrypsinogen and proelastase activated by trypsin
9
Q
What are exopeptidases?
- Location:
- What are the two different types?
A
Cleave from N or C terminal end of peptides and proteins
- Location: Duodenum
-
Carboxypeptidases
- Synthesized and secreted by α-cells of the pancreas
- Activated in duodenum by trypsin
-
Aminopeptidases
- Synthesized by intestinal epithelial cells
10
Q
- How are proteins absorbed?
- What are the epithelial cell peptidases?
A
-
Absorption
- Amino acid transporters (class specific)
- Dipeptide
- Tripeptide
- Duodenum and jejunum
- Amino acid transporters (class specific)
-
Epithelial cell peptidases
- Tripeptidase
- Dipeptidase
11
Q
How are carbohydrates absorbed?
A
- Duodenum and jejunum
-
Transporters
- SGLT1
- GLUT5
12
Q
Where are macronutrients absorbed?
A
Duodenum & Jejunum
13
Q
Vitamin B1 (Thiamine):
- Active Form:
- Functions:
A
-
Active Form
- Thiamine pyrophosphate
-
Functions
-
Cofactor for pyruvate dehydrogenase –
- Decarboxylation
-
Cofactor in pentose phosphate pathway -
- NADPH
-
Maintains neural membranes and normal nerve conduction –
- pH, myelin, neurotransmitters
-
Cofactor for pyruvate dehydrogenase –
14
Q
What happens if there is a vitamin B1 deficiency?
A
- Polyneuropathy (“dry beriberi”)
- Dilated Cardiomyopathy (“wet beriberi”)
- Wernicke-Korsakoff syndrome
15
Q
Vitamin B2 (Riboflavin):
- Active Forms:
- Function:
A
-
Active Forms:
- Flavin mononucleotide (FMN)
- Flavin adenine dinucleotide (FAD)
-
Function:
- Electron carrier
- Complex dehydrogenases
- Citric Acid Cycle to Electron Transport Chain
16
Q
What happens if there is a vitamin B2 deficiency?
A
- Cheilosis (scaling and fissures at the corners of the mouth)
- Dermatitis
- Corneal neovascularization
17
Q
**Vitamin B3 (Niacin): **
- **Sources **
- Active forms
A
-
Sources
- Diet
- Synthesized from tryptophan
-
Active forms
-
NAD+ ⇒ NADH
- Carbohydrate, fat, amino acids and nucleic acid degradation
- Citric acid cycle
-
NADH ⇒ NAD+
- Citric acid cycle - electron transport chain
-
NADP+ ⇒ NADPH
- Glucose-6-phosphate dehydrogenase in the pentose phosphate shunt
-
NADPH ⇒ NADP+
- Used in synthesis of carbohydrates, fats, amino acids and nucleic acids
-
NAD+ ⇒ NADH
18
Q
What happens if there is a vitamin B3 deficiency?
A
- Glossitis
- Pellagra
19
Q
**Vitamin B5 (Pantothenic Acid): **
- **Active Form: **
- Function
A
-
Coenzyme A
- Amino acid, carbohydrate, fat and nucleic acid metabolism
-
Acyl Carrier Protein
- Fatty acid synthesis
20
Q
What happens if there is a vitamin B5 deficiency?
A
- Dermatitis
- Enteritis
- Alopecia
- Adrenal insufficiency
21
Q
**Vitamin B6 (Pyridoxine): **
- Active Form
- Coenzyme involved in ….
A
-
Active form:
- Pyridoxal Phosphate (PLP)
-
Coenzyme involved in
-
Amino acids degradation/conversion to other important molecules
- Aminotransferases
- Decarboxylases – serotonin, norepinephrine
- Serine hydroxymethyltransferase – One carbon metabolism - myelination
- Aldolases
-
Glycogen degradation
- Glycogen phosphorylase
- Porphyrin synthesis
-
Amino acids degradation/conversion to other important molecules
22
Q
What happens if there is a deficiency in vitamin B6?
A
- Convulsions
- Dermatitis
- Peripheral neuropathy
- Sideroblastic anemia
23
Q
Vitamin B7 (Biotin):
- Active Form
- Function
A
-
Active form
- Biotin bound to carboxylases
- Released by biotinidase in small intestine
- Bound in cells to carboxylases
-
Function
- Carboxylase Cofactor – Binds CO2
- Pyruvate carboxylase
- Acetyl CoA carboxylase
24
Q
What happens if there is a deficiency in vitamin B7 or biotinidase?
A
- Dermatitis
- Hair loss (Alopecia)
- Enteritis
25
**Vitamin B9 (Folate): **
* **Active Form**
* **Function**
* **Active form**
* _Tetrahydrofolate_ (THF)
* **Function:** _Carrier of one carbon units_ for:
* _Purine synthesis_
* _dTMP synthesis from dUMP_
* _Conversion of homocysteine to methionine for S-adenosylmethionine (SAM) synthesis_
26
**Vitamin B12 (Cobalamin):**
* **Active Form**
* **Function**
* **Active form**
* **Cobalamin**
* **Function:**
* **Cofactor ONLY 2 enzymes:**
* Methionine synthase
* Methylmalonyl-CoA mutase
* Odd Chain Fatty Acid Degradation
* Isoleucine and Valine Degradation
* **Required for TH4Folate availability for DNA synthesis**
* **Myelin Synthesis**
27
How is vitamin B12 absorbed?
**Intrinsic Factor – Vitamin B12 complex**
28
What happens if there is a **vitamin B12 deficiency**?
* **_Megaloblastic anemia_**
* **_Fetal neural tube defects_**
* **Demyelination**
* **Neural degeneration**
29
Where are the B vitamins absorbed?
* **Most B-vitamins**
* Duodenum
* Jejunum
* **Vitamin B12**
* Ileum
* **Microbiota produced biotin**
* Large intestine
30
**Vitamin C (Ascorbate)**
* **Active Form**
* **Function**
* **Active form**
* Ascorbic acid (Ascorbate)
* **Function**
* **Antioxidant**
* Reactive oxygen species
* Oxidized vitamin E
* **Cofactor of enzymes that reduce metal ions**
* **Post-translational modification of proteins – collagen**
* Lysyl hydroxylase
* Prolyl hydroxylase
* **Synthesis of neurotransmitters and hormones**
31
What happens if there is a **deficiency in vitamin C**?
* **Abnormal collagen crosslinking leading to bleeding**
* **Scurvy**
32
**Vitamin E (Tocopherol): **
* **Active Form**
* **Storage**
* **Function**
* **Most active form**
* **α-Tocopherol**
* **Storage:**
* _Adipose tissue, liver, muscle_
* **Function:**
* **Antioxidant** - scavenges free radicals
* _Recycled by Vitamin C_ (Ascorbate)
33
**Vitamin K (Phylloquinone): **
* **Active Form **
* **Storage**
* **Function**
* **Active form**
* Vitamin K
* **Storage**
* Liver
* **Function**
* **Cofactor for Vitamin K dependent γ-carboxylase**
* Coagulation Factors 2, 7, 9, 10
* Proteins S, C
* Bone calcium binding proteins
* **Modified Gla residue**
* Binds calcium
* Localizes to activated platelets
34
What happens if there is a **deficiency in vitamin K**?
Bleeding
35
**Vitamin A (Carotenes, Retinoids): **
* **Storage**
* **Active Forms**
* Storage - **Liver**
* Active Forms - Functions
* **β-Carotene**
* Antioxidant
* Vitamin A precursor
* **Retinol (Vitamin A)**
* Major transport form
* **11-cis Retinal (Retinaldehyde)**
* Vision
* **Retinoic Acid**
* Gene regulation
36
**Vitamin A (Carotenes, Retinoids): **
* **Function**
* **Retinoic Acid **
* all-trans, 9-cis
* **Regulation of retinoid responsive gene expression**
* Epithelial cell function
* Mucous cell function
* Immunity
* Reproduction
* Development
37
What happens if there is a **vitamin A deficiency**?
* **Night blindness**
* _Susceptibility to infection_
* _Dry scaly skin_
* _Corneal degeneration_
* _Alopecia_
* _Osteoporosis_
38
Vitamin A: Vision
* 11-cis retinal binds ....
* How is vitamin A used in the visual cycle?
* 11-cis-retinal binds:
* Rhodopsin in rods
* Cone pigments in cones
* Visual Cycle:
* Light
1. 11-cis-retinal ⇒ all-trans-retinal
2. Conformational change
3. Signal transduction
4. Signal to the brain
5. All-trans retinal ⇒ 11-cis-retinal in retinal pigment epithelial cells
39
How is **vitamin D (calciferol)** expressed as:
1. **Dietary in Micelles:**
2. **Hormone:**
3. **Active:**
1. **Dietary in Micelles:**
* Animals: **Vitamin D3** (Cholecalciferol)
* Plants: **Vitamin D2** (Ergocalciferol)
2. **Hormone:**
* 7-Dehydrocholesterol ⇒ **Vitamin D2**
3. **Active:**
* **1, 25 dihydroxyvitamin D** (1,25-dihydroxychole-calciferol, Calcitriol)
40
How is **vitamin D** **distributed** and **stored**?
* Distribution:
* **Chylomicrons**
* Storage:
* **Liver**
41
What is the **function** of **vitamin D (calciferol)**?
* **Controls expression of vitamin D responsive genes**
* _Calcium and phosphate absorption in_ _intestine_
* _Bone formation and dissolution_
* _Renal retention of calcium and phosphate_
* **Other:**
* Cell cycle arrest
* Apoptosis
* Immune suppression
* Anti-inflammation
* Differentiation
* **Requires retinoic acid** – binds RXR – **plus 1,25 dihydroxy vitamin D** – binds VDR
42
**Vitamin D Deficiency:**
* Children
* Adults
* Children — **Rickets**
* Adults — **Osteomalacia**
43
Where are the **fat soluble vitamins absorbed**?
* **All fat soluble vitamins**
* Duodenum
* Jejunum
* **Vitamin D**
* Ileum
* **Microbiota produced vitamin K**
* Large intestine
