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TLS Online TPP Program

#Question id: 863

Ubiquitinated proteins are proteolytically degraded in an ATP-dependent process mediated by a large (∼2500 kD, 26S) multiprotein complex named the 26S proteasome;

#Unit 1. Molecules and their Interaction Relevant to Biology

  1. A hollow cylindrical core, known as the 20S proteasome, which is covered at one or both ends by a 19S cap.

  2. The yeast 20S proteasome, which is closely similar to other eukaryotic 20S proteasomes, is composed of Ten different types of α-like subunits.

  3. The yeast 20S proteasome, which is closely similar to other eukaryotic 20S proteasomes, is composed of seven different types of α-like subunits and seven different types of β-like subunits.

  4. The α-type subunits and the β-type subunits are structurally similar, only three of the β-type subunits have proteolytic activity.

    Choose any one incorrect option.

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TLS Online TPP Program

#Question id: 1219

#Unit 4. Cell Communication and Cell Signaling

Many G protein-coupled receptors contain seven transmembrane α-helical domains. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior surface or on the cytosolic surface of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others. Where would you expect to find the carboxyl end of the protein?
TLS Online TPP Program

#Question id: 1220

#Unit 4. Cell Communication and Cell Signaling

Many G protein-coupled receptors contain seven transmembrane α-helical domains. The amino end of the protein lies at the exterior of the plasma membrane. Loops of amino acids connect the helices either at the exterior surface or on the cytosolic surface of the membrane. The loop on the cytosolic side between helices 5 and 6 is usually substantially longer than the others. Where would a coupled G protein most likely interact with this receptor?
TLS Online TPP Program

#Question id: 1221

#Unit 4. Cell Communication and Cell Signaling

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?
TLS Online TPP Program

#Question id: 1222

#Unit 4. Cell Communication and Cell Signaling

Particular receptor tyrosine kinases (RTKs) that promote excessive cell division are found at high levels in various cancer cells. HER2 is an RTK that is present at excessively high levels in some breast cancer cells. Herceptin is a protein that binds to HER2 and inhibits cell division. Herceptin may be an effective treatment for breast cancer treatment under which of the following conditions?
TLS Online TPP Program

#Question id: 1223

#Unit 4. Cell Communication and Cell Signaling

The receptors for steroid hormones are located inside the cell instead of the membrane surface like most other signal receptors. How do steroids gain access to their receptors?
TLS Online TPP Program

#Question id: 1224

#Unit 4. Cell Communication and Cell Signaling

Put the steps of the process of signal transduction in the order they occur.

1. A conformational change in the signal-receptor complex activates an enzyme.

2. Protein kinases are activated.

3. A signal molecule binds to a receptor.

4. Target proteins are phosphorylated.

5. Second messenger molecules are released.