Actin can reversibly assemble into filaments that consist of two helices of actin subunits

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Carcinogens are mutagens, they act by altering one or more nucleotides in DNA.

TLS Online TPP Program

#Id: 10433

#Unit 4. Cell Communication and Cell Signaling

Carcinogens can be classified into two categories: 

1. Direct-acting carcinogens

2. Indirect-acting carcinogens

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Direct-acting carcinogens

highly reactive compounds that can react with and modify nucleotide bases in DNA, to distort the normal pattern of base pairing.

TLS Online TPP Program

#Id: 10435

#Unit 4. Cell Communication and Cell Signaling

Direct-carcinogens includes:

Ethylmethane sulfonate (EMS)

Dimethyl sulfate (DMS)

Nitrogen mustards

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Indirect-acting carcinogens 

Relatively unreactive compounds that become modified to more reactive forms by cellular cytochrome P-450 enzymes

TLS Online TPP Program

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#Unit 4. Cell Communication and Cell Signaling

Benzo(a)pyrene

(found in cigarette smoke & coal tar) undergoes metabolic activation by cytochrome P-450 in the lungs to form a potent mutagen