Misc questions pt 1

Question 1

Thyroxine, calcitriol & retinoic acid do not require a plasma membrane receptor because …….

Answer 1

they are fat soluble hormones. Diffuse through the membrane to bind to an intracellular receptor, which then binds to DNA
* Insulin, on the other hand, binds to a membrane receptor, which activates intracellular tyrosine kinase

Question 2

Define porphyria. And how is lead poisoning related?

Answer 2

any abnormality in heme synthesis pathway.

• If the block is early in the pathway, intermediates are released in urine
• If the block is later in the pathway, intermediates are released in urine, feces & accumulates in the skin/mucous membranes
• • Lead poisoning inhibits ALA dehydratase & heme synthase (ferrochetolase). It causes anemia, dark colored lines in the gums, abdominal pain, neuropathy. Lead is deposited in the epiphysis of bone, abdomen, and RBC (basophilic stippling)

Question 3

Thiamin is ….. in chronic alcoholics

Answer 3

deficient

* Its absorption is inhibited by alcohol and folate deficiency.

Question 4

Which of the following amino acids would be found on the surface of a protein molecule?

1. Alanine
2. Arginine
3. Isoleucine
4. Leucine
5. Phenylalanine

Answer 4

Arginine
because it is a basic amino acid with a positive charge, and it is hydrophilic.
* Hydrophobic amino acids are more likely to be in the core of the protein molecule

Question 5

High levels of the amino acid …… can be used as a replacement for niacin in the body

Answer 5

tryptophan

• It is an aromatic AA with an indole group
• Low levels of both tryptophan and niacin are the main cause of pellagra (characterized by swollen tongue, dermatitis, neurologic dysfunction, and gastrointestinal dysfunction)

Question 6

Deficiency of Vitamin A leads to ……

Answer 6

deficiency retinal pigments, inappropriate differentiation of epithelial tissues (including hair follicles, mucous membranes, skin, bone, and adrenal cortex)

Question 7

The cofactor ….. is required for the decarboxylation of alpha keto acids

Answer 7

thiamine (B1)

• It is required by pyruvate dehydrogenase complex
• Serves as a cofactor for transketolase enzyme in pentose phosphate synthesis (hexose monophosphate shunt)

Question 8

Niacin (B3) is used clinically for the treatment of ……

Answer 8

hypercholesteremia & hypertriglyceredemia

Question 9

Pyridoxine (B6) is a required cofactor for ……

Answer 9

protein metabolism and energy production.
* Deficiencies can lead to the development of glossitis, cheilosis, weakness and irritability. Severe deficiency can cause peripheral neuropathy and anemia.

Question 10

A stretch of 25 hydrophilic amino acids in a protein could be found in ……

Answer 10

collagen (highly enriched with hydrophilic proline & glycine)

• Note that:
  1. start & stop signal sequences are made of 25-30 hydrophobic AA
  2. Transmembrane domain (alpha helix that spans the lipid bilayer) is made of 25 hydrophobic AA

Question 11

What are the three types of hormones??

Answer 11

1. Peptides: from ant & post pituitary, pancreas
2. Aminoacids: catecholamines, thyroid hormones
3. Steroids: from adrenal cortex, ovaries, testes & placenta

Question 12

In a strenuous exercise, list the sources for ATP according to the first consumed (used)

Answer 12

1. ATP stores (first two seconds)
2. Creatine phosphate (first 3-4 seconds)
3. glycolysis (the main pathway)
4. If the exercise continues, gluconeogenesis & lipolysis are utilized

Question 13

What is the function of the Na/K ATPase pump in the RBC??

Answer 13

Maintaining of the RBC volume by regulating salt and water flow in and out of the cell
* RBCs depend on glycolysis for energy, and the two ATPs produced are used to maintain the pump activity

Question 14

What coenzyme/factor is needed for each of the following reactions

1. carboxylation
2. acyl transfer
3. decarboxylation
4. methylation
5. hydroxylation
6. Transamination

Answer 14

1. biotin (in pyruvate & acetyl CoA carboxylase reactions). Vit. K (post translational modification of clotting factors)
2. Pantothenic acid (CoA)
3. Thiamine (B1) like pyruvate and alpha keto glutarate dehydrogenases
4. THF
5. Vit. C in collagen synthesis (hydroxylation of prolyl & lysyl)
6. Pyridoxal phosphate (from B6)

Question 15

Deficiency of Vit. C causes …..

Answer 15

scurvy. Bleeding time will be increased, but PT/INR will be normal

Question 16

Cells, with visible large nucleoli suggests that they are making large amounts of …..

Answer 16

ribosomes

* This is true for cells with high mitotic activity, not just cancer cells.

Question 17

What is the effect of cyanide on energy production??

Answer 17

It binds to Fe molecules in the ETS, blocking the movement of protons back to the inside of the mitochondrial matrix, inhibiting oxidative phosphorylation and ATP production

Question 18

Describe the amelanotic melanoma lesion

Answer 18

non pigmented melanoma, as they totally lack melanin
* The patient can not form melanin due to lack of tyrosinase enzyme
* It is the lead cause of death from skin
cancer
* The lesion is usually in the head or neck

Question 19

Breslow’s classification is

Answer 19

classification of tumors depending on their thickness

Question 20

The main cause of beri beri is ……

Answer 20

Thiamine deficiency due to alcohol

• characterized by damage to the nerves, expressed in terms of pain in the limbs and weakness of musculature.
• The heart can become enlarged and cardiac output decreased.

Question 21

Pyruvate carboxylase deficiency may cause …….

Answer 21

lactic acid buildup, due to accumulation of pyruvate

* This enzyme requires biotin (not thiamine like pyruvate dehydrogenase)

Question 22

Cytochrome C oxidase is ……

Answer 22

the last enzyme in the ETC, located in the mitochondria of muscle and brain

Question 23

G proteins are involved in ……

Answer 23

signal transduction
* Binding of a hormone molecule to G protein will cause binding of a GTP molecule to the alpha subunit of the G protein. Alpha then dissociates from the beta and gamma subunits, and interacts with intracellular effector molecules such as adenylate cyclase, which it activates.

Question 24

Receptor mediated endocytosis is ……

Answer 24

engulfment of a molecule that binds to a receptor on the surface of the cell, occurring commonly at the clathrin-coated pits on the plasma membrane

Question 25

Dietary fibers decreases ......

Answer 25

blood cholesterol * Dietary fiber consists of nondigestable cellulose, lignin, and pectin. * Other actions include increasing bowel motility, reduced exposure of the gut to carcinogens, softer stools, and interference with mineral absorption.

Question 26

In pyrimidine synthesis, carbamoyl phosphate is ......

Answer 26

condensed with aspartate, catalyzed by aspartate transcarbamoylase, to form carbamoyl aspartate * In subsequent steps, ring closure occurs with the loss of water, followed by oxidation to yield orotic acid. * Addition of ribose-5-phosphate produces orotidylic acid, which is decarboxylated by orotidylate decarboxylase to yield uridylic acid & CO2

Question 27

Folate deficiency is associated with ......

Answer 27

overcooked food & old food * Folic acid deficiency causes macrocytic anemia that reveals macro-ovalocytes and hypersegmented neutrophils on the peripheral blood smear

Question 28

Alpha tocopherol function is ......

Answer 28

preventing peroxidation of fatty acids in the cell membrane, helping to maintain its integrity * It is Vitamin E * Reduces the incidence of heart attacks

Question 29

Elongation of the polypeptide chain in the ribosome requires ..... as energy source

Answer 29

GTP | * not ATP, and this is unique!

Question 30

If the enzyme ...... is deficient, severe acidosis occur, with high serum levels of alanine and lactate

Answer 30

Pyruvate dehydrogenase | * Pyruvate will accumulate in this case, leading it to be used in alternative pathways.

Question 31

The citric acid cycle is continuously supplied with new carbon in the form of .......

Answer 31

acetyl CoA | * Though PDH works in the mitochondria to convert pyruvate to acetyl-CoA, pyruvate is NOT a part of the TCA cycle.

Question 32

Chronic Hyperuricemia may cause .....

Answer 32

gout * There is accumulation of needle shaped monosodium urate crystals in joint spaces (often involving the big toe), tophus (soft tissue of elbow)

Question 33

Megaloblastic anemia is caused by deficiency of ...... or ......

Answer 33

B12 or B9 (folate)

Question 34

Triple helical structure of collage is formed in .....

Answer 34

Golgi body * Note that the lumens of the RER and the Golgi are connected * Glycosylation of individual chains occur in the lumen of the ER * Procollagen is formed in the Golgi. Maturation (cross linking of the triple helix) occurs in the extracellular space * Note that SER doesn't participate in collagen synthesis

Question 35

Alanine level during prolonged starvation is ..... because .....

Answer 35

decreased conversion to glucose * Ketone bodies supply the energy * Bicarbonate level is low because it is used to buffer the acidity of ketones

Question 36

Congenital hypothyroidism may cause ......

Answer 36

impaired cognition and hearing

Question 37

Selenium deficiency may cause ......

Answer 37

congestive cardiomyopathy and skeletal muscle degeneration.

Question 38

Proline and glycine are ...... . Aspartate is ......

Answer 38

normal, aliphatic amino acids | negatively charged

Question 39

When TCA slows there is accumulation of Citrate, which then will act as an allosteric inhibitor of .......

Answer 39

PFK-1 (rate limiting enzyme of glycolysis) * Note that: 1. fructose 2,6 phosphatese is activated by cAMP dependent protein kinase 2. 6-phosphogluconate dehydrogenase converts 6-phosphogluconate to ribulose 5-phosphate in the HMP shunt

Question 40

To destabilize an integral membrane protein, we must hydrolyze .....

Answer 40

the hydrophobic bonds between integral membrane proteins and other membrane constituents, such as phospholipids. Accomplished by detergents * To detach peripheral proteins, we can alter pH, increase ionic strength, or dissociate the phospholipid polar head groups

Question 41

The number of nucleotides in the coding region of an mRNA is ..... regardless of how long the untranslated region

Answer 41

three times the number of amino acids

Question 42

Neutrophils use NADPH & O2 to produce ......, which is catalyzed by ...... .

Answer 42

superoxide, NADPH oxidase * Superoxide is then converted to hydrogenperoxide by the action of superoxide dismutase (or spontaneously) * The hydrogen peroxide can also be converted to the toxic HOCl. radical by the action of myeloperoxidase

Question 43

# Define: 1. C-reactive protein 2. Beta-Carotene 3. Apoprotein B

Answer 43

1. synthesis increases by the liver during inflammation 2. a vitamine with an anti oxidant properties 3. one of the proteins that hold lipoproteins together

Question 44

Describe the detoxification of a alcohol in the liver

Answer 44

1. Alcohol is oxidized to acetaldehyde in the peroxisomes and SER 2. Acetaldehyde is then oxidized to acetate (non toxic), catalyzed by aldehyde dehydrogenase in the mitochondria * Peroxisomes: single membrane bound organelles important in detoxification and break down of long chain fatty acids