in the signaling pathway shown, inositol triphosphate (ip3) acts as a second messenger. which of the following best describes how an increase of ip3 affects cellular response? influx of ca2 increases and leads to activation of other signaling pathways. ip3-gated calcium channels close and decrease cellular responses. phospholipase c increases its activity to produce more second messengers. signaling molecules stop binding to protein receptors until ip3 decreases.