Unit 1 Study Review Flashcards

1
Q

What is IP3 (1,4,5 inositol triphosphate) derived from?

A

Membrane lipid PIP2 (phosphotidyl inositol biphosphate)

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2
Q

A hydrogen bond will not form between the hydrogen of a methyl group and the oxygen of a carbonyl group due to what ?

A

The lack of a partial positive charge on the hydrogen atom

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3
Q

Hydrogen bonds form when a hydrogen atom, with a partial positive charge, is shared between two _______ atoms, each of which has a partial negative charge.

A

Electronegative

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4
Q

What best describes the role of activation-transfer coenzymes in the enzyme-catalyzed reactions ?

A

They provide functional groups for covalent catalysis (make covalent bonds with the portion of the substrate that will be transferred)

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5
Q

In the serine protease mechanism, _____ acts as a general base catalyst and pulls a proton from _____, creating the serine nucleophile at the active site.

A

Histidine

Serine

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6
Q

In the cysteine protease mechanism, the _____ orients the histidine appropriately to remove a hydrogen from cysteine, thereby creating a powerful cysteine nucleophile at the active stie.

A

Asparagine

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7
Q

What happens in cysteine proteases or serine proteases if aspartic acid is replaced by asparagine next to histidine ?

A

Asparagine is not charged and so can not stabilize the positively charged histidine by hydrogen bonds

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8
Q

The activation of zymogens to enzymatically-active proteins occurs due to what initial step?

A

Alteration in the primary structure - proteolysis of the zymogen leading to removal of a series of amino acids that will activate the enzyme

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9
Q

A mutation in a plasma membrane receptor changes its Kd for a growth factor from 10-9M to 10-7M , what would be the consequence of this change?

A

It would increase the concentration of growth factor required to achieve a cellular response
-Kd has increased, so it dissociates more readily (growth factor)

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10
Q

Chymotrypsin is a protease that cleaves peptide bonds. It is characterized as which of the following classes of enzymes ?

A

Hydrolases

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11
Q

Which AA has a side chain that has a pKa that can act as a buffer in a physiological pH range (7.4)

A

Histidine

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12
Q

The “T” state of hemoglobin is stabilized by what interaction ?

A

Aspartate sidechain forming and ionic interaction with a residue in the H-helix

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13
Q

What will Iron binding do to the hemoglobin?

A

Lead to R state and higher oxygen affinity

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14
Q

All intestinal hydrolases (proteases, esterases, glycosidases) utilize _____ catalysis to add the elements of water across the bonds, so pH changes will or will not effect the activity of hydrolases?

A

Acid-Base catalysis

Will Effect if pH changes

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15
Q

As the pH falls below 6.5, protons will not readily dissociate from Hisitdine. This means that enzymes that utilize histidine to abstract a proton from the substrate in ____ catalysis are active only when ?

A

Acid base catalysis

Over a neutral range in pH because Histidine needs to be able to accept and donate protons within its pH range

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16
Q

Nerve gas, such as sarin , will lead to muscle contraction due to what ?

A

Prolonged opening of the ion channel in the acetylcholine receptor - due to irreversible inhibition of acetylcholinesterase so the signal will not degrade

17
Q

A mutation in a plasma membrane receptor changed its Kd for a growth factor from 10 to the -9M to 10 to the -7M. What is a consequence of this change ?

A

Increase in Kd = more growth factor required to bind receptor to obtain 50% saturation
(more is needed to reach the same cellular response now as affinity of the receptor for its ligand has decreased )

18
Q

Raising the membrane content of what can increase the membrane fluidity ?

A

Cholesterol - hydrophobic molecule helps disrupt the rigidity

19
Q

An increase in pH from 7 to 13 usually results in protein denaturation due to what ?

A

Loss of tertiary structure caused by deprotonation of basic groups
(NH3 converted to NH2 and loss of ionic interactions and hydrogen bonds- destabilizes tertiary structure)

20
Q

Substrate binding to the active site most often utilizes what types of interaction?

A

Hydrogen bonding

in hydrophobic active sites, hydrophobic forces will be primary driving force in substrate binding

21
Q

A single nucleotide mutation has converted an “I” amino acid to a “N” within a protein. Why might the protein lose activity?

A

Gain of hydrogen bonding capacity

Isoleucine is non-polar and can not form hydrogen bonds

Asparagine has a carbonyl group linked to a amide group on R chain, and can do hydrogen bonding

22
Q

SH2 Domains on proteins are specific for what residues?

A

phosphotyrosine residues

23
Q

The number of distinct human chromosomes ?

A

24
(22 are autosomal distinct)
(2 are sex distinct)
Total each human has is 23 pairs (46 chromosomes)