<span>The mitochondria in eukaryotic cells originated from prokaryotic cells, bacteria that were once free-living. The mitochondria have their own DNA, which is inherited from the mother in most species. Similarly, plant cells have organelles called plastids which contain their own DNA and originated from free-living bacteria. The chloroplasts in plant cells, which convert the energy of sunlight into chemical energy via photosynthesis, are a kind of plastid, and they originated from bacteria that could do photosynthesis.</span>
The opening of channels that let positive ions flow out of the cell (or negative ions flow in) can cause hyperpolarization. Examples: Opening of channels that let
+
K
+
K, start superscript, plus, end superscript out of the cell or
−
Cl
−
C, l, start superscript, minus, end superscript into the cell.
The opening of channels that let positive ions flow into the cell can cause depolarization. Example: Opening of channels that let
+
Na
+
N, a, start superscript, plus, end superscript into the cell.
The opening and closing of these channels may depend on the binding of signaling molecules such as neurotransmitters (ligand-gated ion channels), or on the voltage across the membrane (voltage-gated ion channels).
Answer:
a mature haploid male or female germ cell which is able to unite with another of the opposite sex in sexual reproduction to form a zygote.
Explanation:
