Biochem - Nutrition

Question 1

How many calories per gram does the following yield:

1. Protein
2. Carbohydrates
3. Fats
4. Ethanol

Answer 1

1. Protein = 4 cal/g
2. Carbs = 4 cal/g
3. Fats = 9 cal/g
4. Ethanol = 7 cal/g

Question 2

What are the fat soluble vitamins?

Answer 2

A (retinol)

D

E

K

Question 3

What are the water soluble vitamins?

Answer 3

B1 (Thiamine - TPP) B12 (cobalamin)

B2 (riboflavin - FAD,FMN) C (ascorbic acid)

B3 (niacin - NAD+)

B5 (pantothenic acid - CoA)

B6 (pyridoxine)

B7 (biotin)

B9 (folate)

Question 4

What are the functions of Vitamin A? (4)

Answer 4

1. Antioxidant
2. Constituent of visual pigments
3. Differentiation of epithelial cells into specialized tissue
4. Treatment of measles and acute promyelocytic leukemia (APL)

Question 5

What are the symptoms of Vitamin A deficiency?

Answer 5

• Night blindness (nyctalopia)
• Dry, scaly skin (xerosis cutis)
• Keratomalacia: corneal degeneration
• Bitot Spots: foamy spots on conjunctiva

Question 6

What are the symptoms of excess vitamin A

a. Acute Toxicity
b. Chronic Toxicity

Answer 6

a. nausea, vomitting, vertigo and blurred vision
b. alopecia (bald spots), dry skin, hepatic toxicity, arthralgias, pseudomtumor cerebri

Question 7

Is Vitamin A safe to give to pregnant woman?

Answer 7

No, it is Teratogenic

Can result in cleft palate and cardiac abnormalities

(A negative pregnancy test and 2 forms of contraception are required before isotretinoin (vitA derivative) can be perscribed)

Question 8

What is the function of Vitamin B1 (thiamine)

Answer 8

Thiamine Pyrophosphate (TPP) is a cofactor for several dehydrogenase enzyme reactions

• Alpha-ketoglutarate dehydrogenase (TCA cycle)
• Transketolase (PP pathyway)
• Pyruvate dehydrogenase (links glycolysis & TCA cycle)
• Branched-chain ketoacid dehydrogenase
• “ATP for B1”*

Question 9

What is the major consequence of vitamin B1 deficiency?

In who does this normally occur?

How is it diagnosed?

Answer 9

Impaired glucose breakdown/utilization due to lack of cofactors.

Most commonly seen in alcoholics and malnourished patients

Diagnosis is made by an increase in RBC transketolase activity after B1 administration.

Question 10

Wernicke-Korsakoff Syndrome

1. Occurs due to a deficiency of what?
2. How does it present?
3. How can it be prevented?

Answer 10

1. Vitamin B1 (thiamine deficiency)

2.

Confusion, Opthalmoplegia, ataxia, memory loss

Hemorrhage/necrosis of mamillary bodies and grey matter

3. In alcoholics/malnourished patients give thiamine before dextrose

Question 11

Beriberi

1. Occurs due to deficiency of what vitamin?
2. How does it present?

Answer 11

1. Deficiency of Vitamin B1 (thiamine)
2. Peripheral neuropathy and heart failure

Question 12

Vitamin B2 (riboflavin)

1. What is it used to form?
2. What is its function?

Answer 12

1. FAD and FMN
2. FAD & FMN are used as cofactors in redox reactions

(succinate dehydrogenase reaction in TCA cycle)

(succinate –> fumarate)

Question 13

What are the symptoms of riboflavin (B2) deficiency?

Answer 13

Cheilosis (inflammation of lips, scaling and fissures at the corners of the mouth)

Corneal Vascularization

Question 14

Vitamin B3 (niacin)

1. What is it derived from?
2. What does it make up?
3. What is its function?

Answer 14

1. Tryptophan
2. NAD+ and NADP+
3. Used to treat dyslipidemia

(lowers VLDL and raises HDL)

Question 15

What does severe deficiency of Niacin (B3) lead to and how does it present?

Answer 15

Pellegra

- Diarrhea

- Dementia

- Dermatitis

(broad collar rash and hyperpigmentation of sun exposed limbs)

“The 3 Ds of B3 defiency/pellegra”

Question 16

Hartnup Disease

1. What is it?
2. How does it present?
3. How is it treated?

Answer 16

1. AR diease that results in a defiency of tryptophan
2. Presents with Pellegra-like symptoms

(Diarrhea, dementia, dermatitis)

3. High protein diet and nicotinic acid

Question 17

How does excess niacin/vit.B3 present?

Answer 17

Facial flushing (due to prostaglandins)

Hyperglycemia

Hyperuricemia

Question 18

What is the function of Vitamin B5 (Pantothenic acid)?

Answer 18

It an essential component of CoA and Fatty Acid Synthase

Question 19

What is the main function of Vitamin B6 (pyridoxine)? (3)

Answer 19

It gets converted to pyridoxal phosphate (PLP)

PLP is used as a cofactor for

1. Transamination (needed for amino acid synthesis)

2. decarboxylation reactions

3. glycogen phosphorylase

Question 20

How does Vitamin B6 deficiency present? (4)

Answer 20

• cheilosis (fissures at corner of mouth)
• glossitis
• dermatitis

Can also result in Sideroblastic anemia

Question 21

What is the function of vitamin B7 (biotin)?

Answer 21

It is a cofactor for carboxylation enzymes (add 1C)

• Pyruvate carboxylase
• Acetyl-CoA carboxylase
• Propionyl-CoA carboxylase

Question 22

How does B7 (biotin) deficiency most commonly occur? (2)

Answer 22

1. antibiotic use
2. Excessive consumption of raw egg whites

(they contain avidin, which avidly binds biotin)

Question 23

Vitamin B9 (folate)

1. What is its function?
2. Where is it absorbed?
3. How large are our reserves?

Answer 23

1. Gets converted to Tetrahydrofolic Acid (THF)

Important for DNA and RNA synthesis

2. Absorbed in jejunum
3. Small (lasts weeks to months)

Question 24

Folate Deficiency

1. How does it present
2. Labs (homocysteine, methylmalonic acid)

Answer 24

1. Macrocytic Megaloblastic Anemia

Hypersegmented polymorphonuclear cells

Glossitis

NO neurological symptoms

2. increased homocysteine, normal methylmalonic acid

Question 25

Should folate be given to pregnant woman?

Answer 25

**_YES_** It is given during early pregnancy and 1 month prior to conception **It decreases the risk of neural tube defects**

Question 26

**_Vitamin B12 (cobalamin)_** 1. What are its main functions? 2. Where is it absorbed? 3. How large are our reserves?

Answer 26

1. Methionine and DNA synthesis 2. Terminal illeum 3. Large (Can last years)

Question 27

**_Cobalamin Deficiency_** 1. How does it present 2. Labs (homocysteine, methylmalonic acid)

Answer 27

1. Macrocytic Megaloblastic Anemia Hypersegmented polymorphonuclear cells Glossitis **Neurological symptoms** 2. increased homocysteine, **increased methylmalonic acid**

Question 28

What is the main function of Vitamin C?

Answer 28

**1. Hydroxylation of proline and lysine** in collagen synthesis 2. Necessary for **dopamine b-hydroxylase** (converts dopamine to norepinephrine) 3. Faciliated iron absorption by converting it to ferrous state (Fe2+)

Question 29

What are the effects of Vitamin C on **iron absorption**? How would it impart someone with: a. methemoglobinemia b. Hemochromatosis

Answer 29

**It faciliates iron absorption by reducing it to Fe2+** a. It can be used to treat methemoglbinemia (when there is too much Fe3+) b. Increased iron toxicity in someone with hemochromatosis (They already have too much iron and they dont need more)

Question 30

What occurs as a result of Vitamin C deficiency? How does it present?

Answer 30

**_Scurvy_** - swollen gums - bruising - petechiae - anemia - poor would healing - hemarthrosis

Question 31

What can occur due to excess vitamin C?

Answer 31

**Calcium Oxalate Nephrothialisis** Nausea, vomitting, diarrhea

Question 32

What are the following forms of vitamin D: ## Footnote **1. D₂ (ergocalciferol)** **2. D₃ (cholecalciferol)** **3. 25-OH D₃** **4. 1,25-(OH)₂ D₃**

Answer 32

1. D₂ (ergocalciferol) --\> from ingestion of **plants, fungi, yeast** 2. D₃ (cholecalciferol) --\> from **sun, fish, milk** 3. 25-OH D₃ --\> **_storage_ form in _liver_** 4. 1,25-(OH)₂ D₃ --\> **_active_ form in _kidney_**

Question 33

What is the function of vitamin D?

Answer 33

1. Increased intestinal absorption of Ca²⁺ and PO₄^3- 2. At LOW levels: increased bone mineralization/building 3. At HIGH levels: increased bone resorption

Question 34

What is the consequence of Vitamin D deficiency in: a. Children b. Adults

Answer 34

a. **Rickets** (bone deformities such as genu varum "bow legs") b. **Osteomalacia** (bone pain and muscle weakness)

Question 35

Vitamin E 1. What are the names of the 2 main types 2. What is its function?

Answer 35

1. Tocopherol and Tocotrienol 2. Protects RBCs and membranes from free radical damage

Question 36

How does Vitamin E deficiency present?

Answer 36

**Hemolytic Anemia** **Acanthocytosis** (acanthocytes) **Muscle Weakness** **Ataxia, impaired proprioception and vibratory sensation** (due to posterior column & spinocerebellar degeneration) (Similar to B12 but with **_no_** megalobastic anemia, increased methylmalonic acid and hypersegmented neutrophils)

Question 37

What is the function of Vitamin K? How is it activated?

Answer 37

Cofactor for **y-carboxylation** of glutamic acid on proteins required for blood clotting (**clotting factors II, VII, IX, X and proteins C & S**) Activated by **epoxide reductase**

Question 38

Should vitamin K be given to neonates?

Answer 38

Yes, in order to prevent hemorrhagic disease of the newborn

Question 39

How does zinc deficiency present?

Answer 39

- delayed wound healing - supressed immunity - hypogonadism - decreased adult hair (Axillary, facial, pubic)

Question 40

**_Kwashiorkor Malnutrition_** 1. What is the classic presentation? 2. Why does it occur?

Answer 40

1. Child with **swollen abdomen**, edema, anemia, fattly liver and skin lesions) 2. Occurs due protein malnutrition due to **protein deficient meals** * "Kwashiorkor occurs due to Protein deficient **_MEALS_**:* ***_M_**alnutrition, **_E_**dema, **_A_**nemia, **_L_**iver fat, **_S_**kin lesions"*

Question 41

**_Marasmus Malnutrition_** 1. What is it? 2. How does it present?

Answer 41

1. Malnutrition due to a **diet deficient in calories** but _not_ nutrients 2. Presents as **muscle wasting** and extreme skinniness * "**_M_**arasmus results in **_M_**uscle wasting"*

Question 42

**_Ethanol Metabolism_** **_Ethanol_** ---(?)----\> **_??????_** ---(?)----\> **_?????_**

Answer 42

**_Ethanol_** ---(**Alcohol Dehydrogenase**)---\> **_Acetaldehyde_** ---(**acetaldehyde dehydrogenase**)---\> **_Acetate_**

Question 43

**_Fomepizole_** What does it inhibit? What is it used for?

Answer 43

**Inhibits alcohol dehydrogenase** (ethanol --\> acetaldehyde) Used as an antidote for overdoses of - **methanol** (regular alcohol) - **ethylene glycol** (antifreeze)

Question 44

**_Disulfiram_** What does it inhibit? What effects does it cause?

Answer 44

**Inhibits acetaldehyde dehydrogenase** (acetaldehyde --\> acetate) It causes the **symptoms of a hangover** to discourage drinking

Question 45

What effects does **ethanol metabolism** have on the **NADH/NAD⁺ ratio**? What are the consequences of this effect?

Answer 45

**It increases the NADH/NAD+ ratio** (each step in ethanol metabolism requires NAD+ to NADH) This results in: - **Lactic acidosis** (pyruvate to lactate) - **Fasting hypoglycemia** (prevents gluconeogenesis) - **Hepatosteatosis** (fatty liver)