Question

Are the following statements true or false?

1. Membrane carbohydrates occur as either glycoproteins or glycolipids, and most always face away from the cytosol.

2. The melting temperature of a phospholipid bilayer increase with an increased content of unsaturated fatty acid.

3. Molecules which permeate a plasma membrane by facilitated diffusion require cells to use energy (ATP) for their transfer.

4. “Catabolism” refers to synthetic processes that occur inside the cell.

5. Type I collagen has a membrane bilayer-spanning domain.

6. Cell surface junctions, functionally analogous to focal adhesions, but found in vivo, are gap junctions.

7. L-selectin, the calcium-dependent lectin-binding transmembrane glycoprotein, belong to the integrin family.

8. When neuronal cells release neurotransmitter, they engage in constitutive secretion using clathrin-coated vesicles.

9. Proteins lacking the signal sequence are synthesized in the SER; these proteins may be destine for the cytosol, the nucleus, the mitochondria, or the chloroplasts.

Answer 1

1. Membrane carbohydrates occur as either glycoproteins or glycolipids, and most always face away from the cytosol. True, based on the above information.

lipid bilayers become more fluid (think about butter melting on a hot day), along with increasing the amounts of cis-unsaturated fatty acids.

2. The melting temperature of a phospholipid bilayer increase with an increased content of unsaturated fatty acid. (True) based on the above information

Facilitated diffusion is considered passive transport because substances pass through a cell membrane with the assistance of a protein carrier, and no cellular energy is used in this process. Solutes use facilitated diffusion to move from areas of higher concentration to areas of lower concentration, (Reference, Science).

3. Molecules which permeate a plasma membrane by facilitated diffusion require cells to use energy (ATP) for their transfer. False

4. Catabolism” refers to synthetic processes that occur inside the cell (false) it is breakdown

5. Type I collagen has a membrane bilayer-spanning domain. Since collagen is a structural protein in the extracellular space and further, Type I collagen is the most abundant collagen of the human body which forms large, eosinophilic fibers known as collagen fibers. It is present in scar tissue, (US National Library of Medicine ) this is a false statement.

6. Cell surface junctions, functionally analogous to focal adhesions, but found in vivo, are gap junctions, True, (Alberts, 2002)

7. L-selectin, the calcium-dependent lectin-binding transmembrane glycoprotein, belong to the integrin family. The selectins are a family of cell adhesion molecules (or CAMs) so they belong to CAM but they trigger integrins. Hence false

8. When neuronal cells release neurotransmitter, they engage in constitutive secretion using clathrin-coated vesicles.(true), (Lodish, 2000)

9. Proteins lacking the signal sequence are synthesized in the SER; these proteins may be destine for the cytosol, the nucleus, the mitochondria, or the chloroplasts. (True)