Review EXAM I

Question 1

What are polysomes or polyribosomes?

Answer 1

There are mRNAs segments that have more than one ribosome attached to it, translating.

Question 2

What happens if eIF-2 is phosphorylated? What process will be inhibiting or activating?

Answer 2

If eIF-2 is phophorylated then it is inactive. Trancription is hindered.

Question 3

What are the 5 forms of covalent attachments?

Answer 3

Phosphorylation

Glycosylation

Hydroxylation

Biotin and farnesyl groups.

Question 4

What is glycosylation?

Answer 4

Many of the proteins that are destined to become part of a plasma membrane or to be secreted from a cell have carbohydrate chains added en bloc to the amide nitrogen of asparagine (N-linked) or built sequentially on the hydroxyl groups of serine, threonine, or hydroxylysine (O-linked). N-glycosylation occurs in the endoplasmic reticulum and O-glycosyation in the Golgi. Glycosylation is also used to target proteins to the matrix of lysosomes. Lysosomal acid hydrolases are modified by the phosphorylation of mannose residues at carbon 6

Question 5

What facilitates protein folding?

Answer 5

Chaperones.

Question 6

Protein degradation

What targets for it?

Answer 6

Proteins that are defective (for example, misfolded) or destined for rapid turnover are often marked for destruction by ubiquitination, the attachment of chains of a small, highly conserved protein, called ubiquitin. Protein marked this way are quickly degraded by Proteasomes.

Question 7

What are the characteristic of the genetic code?

Answer 7

Specificity, universality and degeneracy.

Question 8

What are Cis-acting factors on DNA sequences?

Answer 8

They influence the expression of genes only on the same chromosome.

Question 9

What are Trans acting factors on DNA sequences?

Answer 9

A trans-acting factor is the regulatory molecule itself, that can transit (deffise) through the cell from its site of synthesis to its DNA binding site.

For example, a protein transcription factor (a trans-acting molecule) that regulates a gene on chromosome 6 might itself have been produced from a gene on chromosome 11. The binding of proteins to DNA is through structural motifs such as the zinc finger, leucine zipper, or helix-t

Question 10

What is attenuation? and where is it used?

Answer 10

With attenuation, transcription is initiated but it is terminated well before completion.

trp operon, negative control includes Trp itself binding to a repressor protein and facilitating the binding of the repressor to the operator: Trp is a corepressor. Because repression by Trp is not always complete, unlike the lac operon, the trp operon is also regulated by a process known as attenuation.

Question 11

At what pH are all amino acids water soluble?

All A.A. are L configuration except?

Answer 11

At pH 7.

•All aa are L configuration except Glycine.

Question 12

Nonpolar, aliphatic AA?

Answer 12

Glycine, Alinine, Proline, Valine, Leucine, Isoleucine, Methionine.

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Question 13

Polar uncharged AA?

Answer 13

Serine, Threonine, Cysteine (sulfur), Asparagine, Tyrosine, Glutamine.

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Question 14

Polar Charged, AA?

Answer 14

Glutamate (-, acid), Lysine, Aspartate (-, acid), Arginine, Histidine, los demas son +, basic.

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Question 15

Aromatic AA?

Answer 15

Phenylalanine, Tryptophan, and Tyrosine.

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Question 16

What is cystinuria?

Answer 16

An inherited amino acid substitution in the transport protein that reabsorbs Cysteine, arginine, and lysine.

Question 17

What are Globular, Fibrous, Transmembrane, and DNA-binding proteins?

Answer 17

Globular: Soluble in aqueous medium.

Fibrous: geometrically linear and repeating in structure.

Transmembrane: regions aligned to cross the lipid membranes

DNA-binding proteins: member of globar protein family.

Question 18

What is the alpha-helix?

What amino acids disrupt the a-helix region?

What can of syndrome can it cause?

Answer 18

The a-helix is generated by H bonds.

Are common in globular proteins.

Amino acids that disrupt the alpha-helical region of protein are proline (not present at all) large number of charged aa (glutamate, aspartate, histidine, lysine, and asparagine), Tryptophan (bulky R, Valine and isoleucine.

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Question 19

What is Mafan Syndrome?

Answer 19

It is an autosomal dominant genetic disorder of the connective tissue. Has been linked to a defect in chromosome 15, which encodes a glycoprotein called fibrillin-1. The ration of a-helix and b sheets is disrupted.

Question 20

What is Creutzfeldt-Jakob disease (CJD)?

Answer 20

It is a very rare and incurable degenerative neurological disorder that is ultimately fatal. Caused by prions. The CJD result from the transmission of a protinaceuos agent that is capable of atering the normal a-helix arrangement and replacing with b-pleated sheets.

Question 21

What are chaperones proteins?

Answer 21

Chaperones“heat shock” are molecules that catalyze the rate of foldingand protect the protein to form non-productive folding

Question 22

What is Charcot-Marie-Tooth disease (CMT)?

Answer 22

Charcot-Marie-Tooth disease:is a heterogeneous inherited disorder of nerves that is characterized by loss of muscle tissue and touch sensation, predominantly in the feet and legs but also in the hands and arms in the advanced stages of disease.

The absence of these chaperones gives rise to dysfunction either in the axon or the myelin sheathof the nerve cell.

Question 23

What causes Alpha 1-antitrypsin deficiency (A1AD) and what is it?

Answer 23

Misfolded protein

Alpha 1-antitrypsin deficiency(A1ADor Alpha-1) is a genetic disorder caused by defective production of alpha 1-antitrypsin, deficient activity in the blood and lungs, and deposition of excessive amounts of abnormal A1AT protein in liver cells (cirrhosis, emphysema). This results by a misfolded protein that gets trapped within cell.

Question 24

What is the degredation sequence for some proteases?

Answer 24

Some proteins are degraded in a sequence-dependent manner. In the N terminus contains proline, glutamate, serine, and threonine. This sequence is a signal to degradation by nonspecific proteases.

Question 25

What is Chediak-Higashi syndrome?

Answer 25

Chédiak-Higashi syndromeis a rare childhood autosomal recessive disorderthat affects multiple systems of the body, and arises from a mutation in the lysosomal trafficking regulator gene, LYST.

• Have the defect in the ability to transfer enzymes from lysosomes to phagocytic vesicles.
• Neutropenia seems to be the most common. The syndrome is also associated with albinism. Persons are also prone for infections, especially with Staph. Aureus.
• Associated features: Abnormalities in melanocytes (albinism), nerve defects, bleeding disorders.

Question 26

What is the Bohr effect?

Answer 26

the release of O2 from Hb is enhanced when the pH is lower or when increase the present of CO2. the concentration of H+ and CO2 in the capillaries is higher than in the lungs.

Question 27

What happens in sickle cell?

Answer 27

Point mutation: glutamate (neg. charge) at position 6 has been replaced with valine in beta-globin chanins.

This deprives the downstream tissues of oxygen and causes episodes of pain, anemia, hiperbilirubinemia, infections ischemia and infarction, which may cause organ damage, such as stroke.

Question 28

What is Scurvy?

Answer 28

Scurvy is a disease resulting from a deficincy of vitamin C, which is required for the synthesis of collagen in humans.

Question 29

Often presents itself initially as symptoms of malaise and lethargy, followed by formation of spots on the skin, spongy gums, and bleeding from the mucous membranes.

What is this disease?

Answer 29

Scurvy

Scurvy is a disease resulting from a deficiency of vitamin C, which is required for the synthesis of collagen in humans.

Question 30

What is Osteogenesis Imperfecta?

Answer 30

Osteogenesis imperfecta(OIand sometimes known as Brittle Bone Disease) is an autosomal dominant defect. People with OI are born without the proper collagen, or the ability to make it. It usually (though not always) is due to a deficiency of Type-I collagen.