Its not C. i took he test and got A.
Answer:
peptide antigens by MHC class II molecules
Explanation:
Helper T cells are activated by peptide antigens by MHC class II molecules. These antigens express on the surface of antigen-presenting cells (APCs). After activation, the T helper cells divide and secrete cytokines to assist the immune response.
Answer and explanation;
-All lipids contain carbon, hydrogen, and oxygen. Some of them also contain nitrogen and phosphorus. The four main classes of lipids are fats, waxes, sterols, and phospholipids. Fats are triglycerides.
-The functions of lipids include storing energy, signaling, and acting as structural components of cell membranes.
-Lipids are water-insoluble (hydrophobic), and this property is put to great use in the organisation of cells and tissues.
For example; phospholipids are a class of lipids that is amphipathic; that is it contains fatty acid tails that are hydrophobic, and a phosphate head that is hydrophilic. This means the phosphate group will orientate itself towards water and away from the rest of the molecule, and also gives rise to the special properties that allow phospholipids to be used to form membranes.
<span>Organelles are moved within the cytoplasm by being pulled along microtubules by the motor proteins </span><span>dyneins and kinesins.</span>
