Answer:
Cells from the pure culture can cause disease in healthy individual after infecting it with the pure culture.
Explanation:
Koch postulates says that microbes are the cause of every disease. These microbes can be isolated from the infected host and can be grown outside the host in a pure culture. Then this pure culture is able to cause disease in a healthy host after infecting the host with pure culture. Then this same microbe can again be isolated from the second host.
So Koch postulates which proves that cells from the pure culture can cause disease in healthy individuals after infecting it with the pure culture was the step that enabled Koch to determine that a particular microbe is the cause of the disease because it was causing disease in healthy individual also.
<span>Phytoplankton require sunlight because they generate energy though photosynthesis.
They do make tasty snacks for the passing aquatic organism, but not purposefully.</span>
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>.