Chapter Text
“Gabriel: what chemical process in animals produces carbon dioxide?” Michael asked his not-so-little-anymore brother
“Respiration. Commonly referred to as breathing, but it is the diffusion of carbon dioxide and oxygen rather than the movement of air,” Gabriel turned to Sam, sitting next to him. “What is it called when you grow plants in water instead of soil?”
“Hydroponics. Dean, what is one advantage of hydroponic farming?”
“Hydro-whatnow? Oh, hydroponic, right, uh, yeah, um… you can control the nutrients the plant receives better. Lucifer, what part of a xylem vessel provides the strength to support the plant?”
“Why would xylem need…never mind. Plants, not angels. It’s the lignin,” Lucifer looked down at the exam paper in front of him. “Okay, Raph, you need to look at the table. Advantages and disadvantages of growing cucumbers on the moon using hydroponic farming.”
“The hydroponic yield is 12-13 times that of the soil yield and is the highest of the hydroponic yields, which is important because only about a fifth of the plant is edible, the least of all the options. Castiel: how can alcohol be made from biomass?”
“Yeast breaks down the sugar in sugar cane to produce alcohol. Why does biomass produce less pollution than fossil fuels, Balthazar?”
“Because biomass is carbon neutral. When it’s burned, the carbon dioxide released is the same carbon dioxide that went into it when it was created. Uriel, what is meant by ‘partially permeable’? And Raphael? Get that damn stick out of your arse. He prefers the name ‘Cas’, we all know it and you’re the only one who doesn’t call him it.”
Uriel cut in. “Partially permeable means that only some substances are able to get through. And I agree with Balthazar on this one, Raphael. Who else?” Uriel looked around the group. Everyone had immediately raised their hands, looking at Raphael. The former archangel folded his arms and scowled. Uriel smiled.
“Now we know everyone’s thoughts on that, we shall continue. Anna: which statement best describes why the level rises in the sea water tank?”
“I’ve already done this whole ‘growing up’ thing. It ended in a mental asylum when Dean here was saved. It’s the first one – osmosis causes water to move from the dilute to the concentrated salt solution. What is the name of the green chemical in the celery leaves that absorbs sunlight, Naomi? Actually, now I think about it, it’s a lot like you. Sucking the happiness out of everything.”
“Hey! I had Heaven’s best interests in mind-“
“Yeah, ‘cause that always turns out so well, doesn’t it?” Dean grumbled. He hated being 16 again, especially because Sam, like everyone else, was the same age and consequently still taller than he was.
“Shut up, Dean,” Naomi rolled her eyes at him. “Not everyone has the typical Winchester luck. The chemical is chlorophyll. Stop sulking, idiot. Michael: name the two cell layers the celery leaf miner has eaten from.”
“Uh, the spongy mesophyll and…the…uh…Stop laughing, Luci, you know I always hated biology. Mrs. Bliknam hasn’t improved that opinion much either. Uh, shit. I don’t know. Shut it, Gabriel.” Michael hated admitting defeat, but he had no choice on this one. “Let’s see how well you do. Explain why the celery plant does not grow as well when these particular cells are eaten.”
Gabriel laughed. “The plant doesn’t grow as well because the cells aid respiration and energy conversion in the plant. Without the cells for those processes the plants’ growth is stunted. Sammy, what is Bacteria A which converts compost into ammonium compounds?”
“Bacteria A are saprophytes, I think. Bacteria B are nitrifying bacteria. And Michael, the other layer is the palisade mesophyll. It contains a load of chloroplasts, so losing it reduces the amount of sunlight absorbed and therefore the amount of energy that can be made, so the plant can’t grow as well. Dean, why are the nitrates produced more slowly in cold weather?”
“Cause they want to stay in their nice warm beds.” Dean deadpanned, face completely straight, but Sam could see the corners of his mouth twitching. “Nah, it’s cause the bacteria work better in warm conditions. Too warm and they die though. Luci, which two statements best explain why nitrates can only be absorbed by the roots if there is enough oxygen in the soil?”
Lucifer looked at the list for a moment before speaking. “I’m guessing the fourth and fifth statements: diffusion of minerals occurs faster in high oxygen levels and plants take up minerals from a high concentration in the soil. The second statement is a possibility, but the others don’t follow.”