Page 12 of 15 8. Which of the following statements about plasma membranes is INCORRECT?
A. They are composed of phospholipids.
B. They have both integral and peripheral proteins.
C. They are relatively rigid structures.
D. They function to separate the extracellular and intracellular environment.
CONT
st?

C. They are relatively rigid structures.

Explanation:

The plasma membrane is a semipermeable lipid bilayer mainly composed of amphipathic phospholipids, which acts as a barrier to separate the cytoplasm from the extracellular environment. This barrier is considered a fluid combination of proteins, lipids and carbohydrates. The fluid mosaic model states that the plasma membrane is a mosaic of lipids (especially phospholipids and cholesterol), as well as proteins and carbohydrates (glycolipids and glycoproteins) that are constantly moving. This fluidity alters the rotation and diffusion of proteins and other components within the plasma membrane, thereby affecting their functions. Membrane fluidity has been experimentally demonstrated by a variety of techniques. (e.g., X-ray diffraction, labeling techniques, calorimetry, etc).

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

b c a d mark me