Key physical features. All three species share similar physical characteristics - a relatively small body and a 'robust' or strongly built skull including large lower jaws with extremely large molar teeth.
Because it grows rapidly.
Answer:
Function: Cell signalling; Location: Cell membranes
Explanation:
Receptors are usually trans-membrane proteins located on cell membranes. Their extracellular part transmits chemical signals from outside the cell into the intracellular where a response is induced.
Answer:
D) bilayer membranes
Explanation:
Two lipidic bilayers compose the cell membrane. There are also proteins and glucans incrusted in between. Lipids are amphipathic molecules with hydrophilic heads -negatively charged phosphate group- and hydrophobic tails. Lipids are arranged with their hydrophilic polar heads facing the exterior and the interior of the cells, while their hydrophobic tails are against each other, constituting the internal part of the membrane. Membranes are fluid, which means that the composing molecules can move through them.
Lipids can easily change places with other neighboring lipids by lateral diffusion in the same layer. This is passive diffusion, which means that it does not need energy to happen.
Lipids can also diffuse transversally to the other layer but not as easily as lateral diffusion. Jumps between monolayers are infrequent as the lipidic polar heads meet the fatty acid barrier.
There are also other lipidic movements as rotational diffusion that imply the rotation of the molecule.
1) antigen presenting
2) release cytokines
