Use a egg. It resembles a cell it best resembles a animal cell and that’s because it is from an animal but look up whats inside egg and talk about it.
Rods and cones are similar in that they both release glutamate as the primary neurotransmitter. During signalling the rod and cone photoreceptors signal their absorption of photons via a decrease in the release of the neurotransmitter glutamate to bipolar cells at its axon terminal. Every rod and cone photoreceptor release the same neurotransmitter, glutamate.