Neither the peptide hormones or the metabotropic neurotransmitters such as the catecholamines, can enter their target cells. They bind to surface receptors, which then activate second-messenger systems in the cell. Peptides hormones are the hormones that consist of amino acids; they can be among the intracellular signalling peptides and proteins, and can include insect hormones, gastrointestinal hormones and thyroid hormones, but their actions are not limited to individual cells and they can act systemically.
Answer: Summer
Explanation: When the southern hemisphere is closest to the sun, and it receives the most sunlight it is summer time, while in the northern hemisphere it's winter.
The main factor that determines seasons is the way sun rays enter Earth, and not as much proximity, since there is only a 2% variation in the distance overall
Answer:
O blood only
Explanation:
o blood helps to circulate in our body
the answer is B. They travel through pollen tubes