photosystem ii

Photosystems in Photosynthesis

Before we kick off this whole Photosynthesis thing we just need to clarify what exactly this mess is

This bad boy isn’t as complicated as he looks, he’s a Photosystem (Photsystem II to be exact) and basically it’s just a collection or pigments and proteins arranged in a certain way. The green stringy things you see in this diagram are chlorophyll.

In the Light Dependent reactions of Photosynthesis there are two of these photosystemy things involved - Photosystem II and Photosystem I (imaginative names), both of which are located in the Thylakoid Membrane of a chloroplast


Photosystem II also contains what is known as the Oxygen Evolving Complex which does just what it says on the tin - produces Oxygen, Protons & and Electrons from the photolysis of water molecules.

The light reactions of photosynthesis basically do two things:

  1. Make ATP
  2. Split water to get electrons

The ATP is made by ATP synthase, which is found in almost all organisms on Earth. The water splitting is accomplished by an enzyme called photosystem II, pictured above. It’s possible you’ve performed a water splitting experiment in a chemistry class: you run electricity through water and produce hydrogen and oxygen gas. But you have to use electricity to do it, and that’s a lot of effort. Plants do it just by hanging around in the sunlight and getting watered!

The mechanism of photosystem II, which is important for life on Earth as we know it, is not fully understood yet. If you want to do science, how about figure it out for us, Clear Scientists? 

  • a timer appears on everyone’s wrist the moment they turn 12 that counts down to the moment they meet their soulmate
  • why 12? bc I like the number 12 no one knows
  • some people’s timers show up as 0 meaning they’ve already met their soulmate
  • others have a few days until they meet their soulmate
  • but in most cases there are years of waiting left until the soulmates meet
  • when Seungkwan turned 12, he was greeted by a long string of number that read 6:9:12:23:31:38
  • 6 years, 9 months, 12 days, 23 hours, 31 minutes, and 38 seconds until he’d meet you
  • some basic calculations told him that he’d meet his soulmate during October of his freshman year of college
  • if he made it right after hs
  • knowing this, he chilled his way through middle and high school
  • didn’t have to worry about what his soulmate would say and was the life of every party
  • no seungkwan? no party.
  • however, he still thought about his soulmate a lot
  • what would you be like?
  • how would the two of you meet?
  • how would you take his noisy sides?
  • were you anything like his “ideal type”?
  • the years flew by and he ended up a transfer student in the US for his freshman year of college
  • moved into the dorms in Sept, super excited to start school and meet his soulmate in a few weeks
  • as the time counted down, started making up scenarios in his head about how you two would meet
  • scenarios like Vernon suddenly announcing his marriage and him flying back to Korea and meeting his soulmate while getting fitted for a suit bc he’s Vernon’s best man
  • or running into his soulmate at his favorite Chinese place in front of school when a waiter trips his soulmate and he dramatically saves them from falling
  • yes he’s a sappy romantic
  • so what?
  • *josh as a shrug emoji*
  • anyways
  • as the date got closer, so did midterms and he was forced to stop spending so much time daydreaming and snap back to reality a little
  • started to focus on his study and realized that he wasn’t going to have some ridiculous escapade where he meets his soulmate unless he failed midterms and he couldn’t really afford that as an international student
  • didn’t like studying too much and came up with a method catered specifically to him to make it through
  • he’d study for his calc midterm for an hour or so then
  • BLAST TUNES for 10
  • (minutes not hours)
  • then he’d study English for an hour then 
  • then he’d study his Chinese for an hour ish and
  • roommate!dk studied chem for an hour?
  • by blasting tunes, I mean BLASTING them
  • you could hear it from across the floor 
  • even in from upstairs
  • his blasting of music was not approved by most people on the floor
  • lots and lots of noise complaints from fellow residents
  • RA got complaints for everyone about Seungkwan’s study habits on a daily basis
  • everyone except you
  • you’d initially complained as well, but then you found that the system was actually pretty regular and that his choice of music was pretty similar to yours
  • you started studying the BSK (boo seungkwan) way
  • studied for an hour then jammed to seungkwan’s tunes for ten minutes
  • you’d never met the source of the music, but you found yourself growing increasingly grateful for them
  • you’d never really met anyone in your dorm bc you never went to floor gatherings
  • sometimes you were busy
  • sometimes you forgot
  • other times you were just plain lazy
  • since you never went to these things, you had no clue who the heck was fueling your study with some lit tunes, but you thanked them nonetheless
  • you had a timer on your wrist as well, and you’d discovered that you would be meeting your soulmate on the day before your biology midterm
  • despite having been excited about meeting your soulmate, you completely forgot about the countdown happening as you panicked over midterms
  • how the heck did professors magically sync all their tests and assignments to all be due in the same week?
  • you didn’t have the time for this!
  • the day before your bio midterm arrived faster than you’d anticipated
  • the timer on your wrist reading 7:32:14 (7 hours, 32 minutes, 14 seconds) was the least of your worries with a bio midterm (worth 20% of your grade) countdown of about 23 hours
  • the day started off like all the other days during testing weeks
  • you went to class, went to grab food with friends to panic about midterms together, then headed back to your dorm to study
  • you started studying when you got back, pulling out the brick of a textbook and trying to recall what the difference between the two photosystems were and why the heck photosystem II came before photsystem I
  • or did it?
  • midterm struggles are real
  • you were dying, but kept pushing through, waiting for your jam session to start
  • but then, something weird happened
  • there was no music
  • you’d been studying (emphasis on the dying) for over an hour, but there was no music
  • the silence was uber distracting to you
  • even though you would’ve taken a break at this time anyways, you couldn’t really let loose and kept feeling anxious, meaning you weren’t as ready to get back into study mode after 10 minutes
  • the break in routine was getting to you
  • you’d grown dependent on music blasty person for your studying abilities
  • dang it.
  • while you were struggling with your studies, BSK was dying for a completely different reason
  • he was freaking out in his dorm bc HE’S DONE WITH MIDTERMS
  • !!
  • !!!!!!!!!!!!!!!
  • the boy was a little excited
  • just a little
  • that’s why he’d shaken roommate!dk awake by the shoulders at 8AM in the morning to spazz despite not having to be up until 2pm for a 2:30 class
  • didn’t really know what to do with himself
  • should he go out?
  • should he stay in his dorm?
  • should he dress up nicely?
  • he was struggling
  • he eventually headed off to his 2:30 class (Calc), still spazzing and DK kicking him out so he’d go to class
  • you were debating whether or not it’d be worth having complaints filed against you for blasting music the way that music blasty person did to study for your midterm
  • you couldn’t concentrate bc your study rhythm was broken
  • rip you
  • your thoughts kept drifting to the abnormal noise level in your dorm
  • ugh
  • you decided you’d try studying at a café bc nothing was getting done in your dorm and headed out
  • the timer on your wrist read 2:17:51 (2 hours,  17 minutes, 51 seconds)
  • not that you noticed
  • you need to get a good grade on that midterm!!!!
  • studying at the café did not help much
  • yes there was music, but it was constant
  • you couldn’t work with that
  • not after getting used to silence followed by a freaking turnt party
  • you gave up on the  café and decided to head back to the dorm, seriously considering the pros and cons of blasting music yourself
  • however, when you walked back into the dorm, you were greeted by the familiar sound of IOI’s “Whatta Man” blasting at 500% full volume 
  • relieved that the system was back in place, you headed into your room
  • maybe they’d just slept in today and started studying later
  • you relaxed and jammed to the song, waiting for the music to stop so you could study
  • but it didn’t
  • tune after tune
  • song after song
  • twenty minutes passed
  • didn’t stop
  • even worse for studying than the silence
  • why must they be so cruel?
  • you decided you’ve had enough
  • you got yourself together and marched to the source of the noise
  • meanwhile, BSK was partying it up in his dorm, excited to be meeting his soulmate in a few minutes
  • didn’t really know what was going to happen
  • but he was excited
  • tbh when is he not?
  • you found yourself standing in front of room 317, completely oblivious to the timer on your wrist counting down its last seconds
  • you knocked on the door and while you couldn’t see it, seungkwan froze 
  • he froze, then looked down at his timer that was at 23 seconds
  • roommate!dk saw seungkwan wasn’t moving, but noticed him glancing at his timer and pushed him to the door
  • Seungkwan snapped out of it and opened the door, timer counting down quickly to zero…
  • only to be greeted by a very grumpy looking you
  • that didn’t scare seungkwan though
  • he barely noticed your expression and engulfed you in a hug
  • you pushed him off you like
  • ?????
  • what the heck?
  • “You’re my soulmate!”
  • you were confused bc you hadn’t thought about your soulmate for a while but then you realized 
  • you looked down at your wrist
  • sure enough, your timer was at 0
  • to say you were shocked would be an understatement
  • you didn’t have time to process everything before seungkwan dragged you inside and bombarded you with questions about yourself
  • you tried your best to keep up and answer his questions, brain still kind of elsewhere
  • when he asked what classes you were taking, you remembered why you came
  • you told him why you’d come and he agreed to follow his normal studying schedule with his music despite being done with midterms himself
  • on the condition that the two of you could go get boba together after your bio exam
  • you agreed
  • who says no to free bubble tea anyways?
  • that was the start of a new page in your life with booeun boi as your partner and newest study buddy
  • yey!

Written by Admin Sea

I’m sitting outside and looking at plants and trying to relax but all I can think about is parenchymal cells and PHOTOSYSTEM II COMES BEFORE PHOTOSYSTEM I and xylem and phloem and the Calvin cycle

lol too bad none of that was on the actual exam


Photosystem II

(This video goes into more detail than necessarily needed for AQA Biology Unit 4 but it’s still good to see)

one thing I hate about biology is that numbering of anything is reliable enough to feel somewhat safe assuming ist what it should be, but enough important things are numbered weirdly where you realistically never SHOULD feel safe

Like photosystem II is a critical focus and is procedurally before photosystem I in the electron transport bullshit and yet, its PSII. The three classes of myosin, as you’d expect, are one, two, and five.