Answer:
The answer is A.
Explanation:
B) Nucleotides and amino acids can act as extracellular signal molecules:
ATP is made of adenosine (a type of nucleotide) and used in cell signalling called "purigenic signalling" and amino acids are also used as signal molecules.
C) Some signal molecules are transmembrane proteins:
Transmembrane acts as receptors for smaller signal molecules so this can also be accepted as true.
D) Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription:
That is also true, some of the hormones can cross lipid membrane of the cells and bind directly to the intracellular (inside-of-a-cell) proteins.
Lastly; dissolved gasses such as nitric oxide can activate proteins such as guanylyl cyclase so this choice is <u>false</u>.
<span>The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but now appears to be dormant. Besides silicon and oxygen, the most abundant elements in the Martian crust are iron, magnesium, aluminum, calcium, and potassium.</span>
A crab lives in the intertidal zone.
A crab spends most of its time scavenging for food in the sand.
The food chain, just from common knowledge, would be
fruit trees, birds, monkeys, tigers.
The fruit trees cannot prey on anything. The birds eat the fruit, the monkeys can catch birds and eat them, and the tigers can eat the monkeys.
The surface of a leaf has many tiny pores, called stomata. The stomata allow carbon dioxide into the leaf so that photosynthesis can occur. They also allow water to leave the leaf by transpiration. Plants that grow in full sunlight usually have most of their stomata on the shaded undersides of their leaves.
