Answer:
3. the absence of a cell wall in human cells
Explanation:
Animal cells do not have cell walls. Cell membranes separate the cytoplasm of the animal cells from the surroundings and maintain their interior. Plant cells have cellulosic cell walls. A cell wall surrounds the cell membrane of a plant cell. Cell walls serve to provide structural support and protect plant cells from pathogens. Cell walls also help keep excess water out of cells so they do not burst. Therefore, human cheek cells would not have cell walls while the onion cells would have cell walls made up of cellulose.
Answer:
Hormones can be proteins, lipids or cholesterol-based molecules. Neurotransmitters are protein. The main difference between hormones and neurotransmitters is that Hormones are produced in the endocrine glands and released into the bloodstream where they find their movement targets at a distance from their origin. In contrast, Neurotransmitters are released into the synaptic space by a terminal of an excited presynaptic nerve cell and transmit a nerve signal to the neighboring postsynaptic nerve cell.
Explanation:
Explanation:
so there blood can go in and out of there arteries and ventricles
