15) cara and chuck were looking at pond water through a microscope. they saw this image. cara wondered what it was. chuck said it had to be a living thing because it was a) green. b) moving. c) made of cells. d) round throughout. 16) your science teacher has asked the class to make a cell city model. which building or business in the city could represent the mitochondria, and why? a) city dump - waste storage b) city hall - control center c) roads - transportation system d) power company - produces energy 17) identify the structure that protects and gives support to this plant cell. a) vacuole b) cell wall c) cytoskeleton d) cell membrane 18) which cell structure is the gatekeeper, controlling what goes in and out of the cell? a) c - nucleus b) e - vacuole c) a - cell membrane d) b - endoplasmic reticulum 19) karina is looking at a group of cells under the microscope. the organism has many cells, each with a cell wall and green chloroplasts. it has a nucleus and membrane bound organelles. in which kingdom should this organism be classified? a) animalia b) fungi c) plantae d) protista 20) is a jellylike substance in both the animal and the plant cell containing important chemicals and acts like a matrix for the cell organelles. a) chloroplast b) cytoplasm c) mitochondria d) vacuole