Any help/explanation for the answers to these cell biology questions would be ex

Question

Any help/explanation for the answers to these cell biology questions would be extremely helpful. Thank you so much.

1.) Which of the following molecules would enter the cell via a specialized transmembrane receptor?

A) O2

B) fatty acids

C) cholesterol

D) ethanol

E) glucose

2.)

Of the following molecules, which would not be expected to be moved across a membrane by simple diffusion?

A) oxygen

B) fatty acids

C) water

D) sodium ion

E) carbon dioxide

3.)

Which of the following will destined a protein to the lysosome?

A) mannose-6-phosphate

B) KDEL tag

C) RXR tag

D) HDEL tag

E) all of the above

4.)

Using the techniques of genetic engineering, you design a cytoplasmic protein you want to accumulate within the ER of yeast cells. To accomplish this goal, you need to

A) do nothing; all proteins go through the ER.

B) incorporate the appropriate mannose-6-phosphate groups.

C) incorporate the appropriate DNA sequence that codes for the KDEL signal.

D) incorporate radioactive fatty acids into the protein.

E) incorporate the appropriate DNA sequences that codes for AAAA signal.

5.)

Which of the following glucose transporters in humans has properties that facilitate glucose transport out of the cell in response to keeping blood sugar levels homeostatic?

A) GLUT1

B) GLUT2

C) GLUT3

D) GLUT4

E) GLUT5

Explanation / Answer

1. A. Oxygen - only small non-polar molecules can enter the cell via a specialized transmembrane receptor like gases.

2. D. sodium ion - Oxygen is a small non polar molecule, so it easily go through a cell membrane. Carbon dioxide is the byproduct of cell respiration and readily diffuse out of a cell. Small uncharged lipid molecules can pass through the lipid innards of the membrane. charge of the particle play an important role in passage of the molecules, sodium and potassium channels are used for the passage of such ions across the cells.

3. A.  proteins can be destined for the lysosomes by the lysosomal pathway; proteins destined for the lysosomal pathway are glycoylated which adds a special targeting signal mannose-6-phosphate.

4. C. incorporate the appropriate DNA sequence with the proper signal. in this case it is KDEL, KDEL is a target peptide sequence in the amino acid structure of a protein, which prevents the protein from being secreted from the endoplasmic reticulum thus accumulates it.

5. B. GLUT 2, Glucose transporter 2 is also known as solute carrier family 2 (facilitated glucose transporter), it is a transmembrane carrier protein that enables protein facilitated glucose movement across cell membranes. It is the main transporter for transfer of glucose between liver and blood, maintain hemostasis.

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