The Golgi Apparatus is a membrane-bound organelle in the cell thatreceives proteins and lipids from the rough endoplasmic reticulum. It modifies some of them and sorts, concentrates and packs them into sealed droplets called vesicles. This organelle can be seen using an electron micrograph.
08/100 days of productivity!! i went to the botanical gardens today!! didnt manage to make any notes but I got to revise the structures & functions of cell organelles!! ヾ(＠⌒ー⌒＠)ノ today was such a relaxing day!! i laid down on soft grass, listened to hamilton & read a book!!! 🍂
but why???? how the fuck did this little bean shaped nubbin of a thing wind up being this all-important piece of cell that we learn about in once sentence and then completely forget about until it’s time to take an exam?
tumblr, sit down and let me learn you a thing
back in the waaaaaaaaaaaaay back early days of life, when there were just like, bacteria and random assed algae and shit floating around in the primordial soup, before there was oxygen in the atmosphere, all cells got their energy from anaerobic respiration
which basically means they used no oxygen, just kinda fermented stuff and nibbled at nutrient bits here and there, but it was suuuuuuuper inefficient
like, imagine trying to run through your day on only two sips of coffee. that’s literally all you can make each day is two sips of coffee, and you HAVE to work with it in order to do your whole life and living thing. that is literally all you are allowed
you’d be pretty fuckin sluggish, amirite
well, along the way, these new kinds of bacteria start forming. they have these weird greenish pigments. they can use the sun to make a jillion times more energy than most other cells. like, by an enormous margin. like, instead of starting their day with two sips of coffee, they start their day with three and a half cups.
and the byproduct of their energy conversion is oxygen
suddenly they just start breeding, since they can outperform everything else in the primordial soup
and this oxygen keeps filling the air, changing the composition of the atmosphere from methane, ammonia, nitrogen, and CO2, to something a little more oxygen rich. the skies turn blue. the oceans go from olive to reddish to blue as the iron in them oxidizes and falls to the seafloor. suddenly it starts looking like what we’re used to.
these little green bacteria start making some pretty sweet deals. some of them sneak into larger cells, trading their energy output for not having to hunt down nutrients for their own survival. the cells they live inside stop trying to make energy on their own and rely on the bacteria, now basically functioning as chloroplasts.
but now that there’s oxygen in the atmosphere, a NEW kind of bacteria emerge. these little guys are purple.
these guys use sunlight and oxygen to produce even MORE energy than just chloroplasts on their own. They’re mega efficient, but they don’t produce oxygen at the end of their little processes. instead they make sulfates and phosphates.
these little guys start hanging around inside larger cells, some of which have chloroplasts, and some of which instead consume other cells to create energy
they give up photosynthesis, instead getting their energy from either the chloroplasts or the “food” from the larger cells, and in return the bigger cells get an enormous amount of energy, which lets them compete on a much higher level than before.
that’s where mitochondria come from.
but the thing is, mitochondrial DNA doesn’t change much over time. It was already pretty solid when it first entered the early, larger cells.
what they’ve found is that plants, fungi, and animals all have different mitochondrial DNA bases
and protists have basically a FRILLION different types of mitochondrial DNA
this means that this happened multiple times, each using slightly different kinds of little purple bacteria
in fact, fungi’s are SO different that some of the codons in the DNA, that in every other organism on earth mean “stop coding for anything, this is the end of the sequence” in fact produce a completely different result and make amino acids instead like tryptophan
which means this has to be an ancient, crazy lineage that happened before DNA was really set in stone, before the different codons became universal for different kinds of amino acids
This was my first time recording a time lapse but I didn’t even realise I was doing this for an hour 0.0.
Just completing some biology homework on organelles because I have a SAC next week.
Everyone has some kind of NSAID in their medicine cabinet whether it be Advil, Aleve, or Aspirin. These drugs are so common that they are often not even considered drugs and so people freely take more than they should or give them to their pets. Understanding how these drugs work not only helps explain why the directions for using them are so specific, but also shows how really amazing it is that we even have them. So, let’s get to the real reason you are here- COX.
Animal and human cells are sort of like water balloons. The “balloon” part of the cell is the membrane which is made up of lipid molecules. The water is actually still water but also filled with lots of different organelles, proteins, enzymes, and other things that make the cell work. Located within the cell membrane is a special lipid called arachidonic acid (AA). Usually AA just hangs out in the membrane not doing a whole lot. It takes an enzyme called phospholipase A2 (PLA2) to free the AA from the cell and let it get to work.
PLA2 is itself “turned on” by other enzymes but to make it simple, it is activated when there is an injury of some kind. It breaks the AA free of the cell membrane so that it can then be turned into other useful molecules.
Usually AA can be turned into three different types of molecules: prostanoids, leukotrienes, and epoxides. We are only going to worry about prostanoids today.
Prostanoids are a group of molecules that do lots of different things in the body including create inflammation, dilate blood vessels, activate platelets, de-activate platelets, protect the GI tract, make sure the kidneys have enough blood flow, and other important for living type things.
Here is where the COX comes in. COX-1 and COX-2 are enzymes that convert arachidonic acid into usable molecules. In very general terms COX-1 is responsible for making housekeeping type molecules, the ones that protect the gut and keep the kidneys working. COX-2 is the enzyme that makes the inflammatory molecules. In reality it isn’t that simple and box COX enzymes overlap in function but we are keeping it simple.
COX converts AA into PGH2 which is then further into five different prostanoids, Thromboxane, PGD2, PGI3, PGF2, and PGE2. The prostanoid we care about right now is prostaglandin E2 (PGE2). PGE2 is an inflammatory mediator and is responsible for the classic signs of inflammation: redness, swelling, pain, and warmth or if you wanna impress your friends using Latin: rubor, tumor, dolor, and calor.
PGE2 has four different receptors that it can bind to, each one doing something a bit different. EP4 is the receptor responsible for causing pain and inflammation.
*Head explosion* I know, it is a lot. Let’s summarize. Injury causes PLA2 to free arachidonic acid from the cell membrane. COX-1 and 2 convert AA into PGH2. PGH2 turns into PGE2. PGE2 binds to receptors on cells which then cause inflammation and pain.
Now we can discuss medications. Corticosteroids like prednisone work by blocking PLA2 way at the beginning of the pathway. This means everything downstream is stopped. There is no production of prostanoids, leukotrienes, or epoxides. Steroids are like bringing a bazooka to a knife fight, they work but there is a lot of collateral damage. We cannot use steroids for very long because of the severe side effects they cause.
NSAID’s are COX blockers. Some block both COX-1 and 2, others are more selective and mostly block COX-2. This prevents formation of PGH2 which prevents all of the prostanoids down stream from being formed. Celebrex was a popular human NAID that preferentially blocked COX-2 which sounded great. However it prevented the formation of PGI2 which was a vasodilator and anti-thrombotic, this caused many people to die of heart attacks. This doesn’t seem to be an issue in pets but blocking COX does lead to GI ulceration and renal damage in some animals. Aspirin irreversibly binds to platelets and prevents clotting which can be a problem in humans and animals in addition to causing GI ulcers.
A fairly new class of drugs called Piprants has been developed and they specifically target one of the receptors that PGE2 binds to. This leaves all of the other molecules available to do their jobs and only prevents pain and inflammation. This means the drug is safe for dogs with liver or kidney disease and shouldn’t have any GI side effects. Hopefully something similar for humans is produced as well.
So that in a very complex nutshell is how NSAID’s work and hopefully now you have a greater understanding of just how important it really is to follow all drug labels. And you now you can tell all your friends about your COX.
*Disclaimer- NEVER give OTC pain meds to your pets. Many are toxic to them and the safe ones require different doses than what humans take. Always consult with your vet first.
So, I see a lot of people – not just here, but in my classes – that are pushing themselves to memorize tons of terms and then become frustrated that they aren’t getting the results they want. And, I think this idea that you need to memorize entire textbooks worth of terms to do well in AP classes is totally inaccurate. The absolute most important thing you can do is: make connections. AP exams have been reconfigured to see how students can make connections between topics and draw conclusions based on information – not just spout facts. For instance, the AP Biology exam used to ask relatively simple identification questions such as, “Which organelle is responsible for cellular respiration?” The reconfigured exam would instead have a question such as, “Christae are folds found within mitochondria in eukaryotic cells. How do christae provide an advantage in the processes undergone in mitochondria?” (please bear with me I came up with that off the top of my head). Or, in APUSH, there is less focus on the actual battles of the Civil War and a greater emphasis on the Antebellum Period that led up to the conflict. My point is, the key to success in AP classes (in my opinion), is to not focus just on memorizing facts, but understanding big ideas and trends, and THEN having facts/details to support those ideas.
Organelle = particular structure of cell that has a specialised function
[1 = structure; 2 = function]
Organelles surrounded by membranes
Largest organelle; when stained, shows darkened patches of chromatin; surrounded by nuclear envelope; structure made of two membranes with fluid inbetween; nuclear pores [a lot of holes] through the envelope; nucleolus [dense, spherical structure] inside nucleus
Home to the cell’s genetic material; chromatin consists of DNA and proteins; has instructions for making proteins; some of the proteins regulate cell’s activities; when cells divide, chromatin condenses into visible chromosomes; nucleolus makes RNA and ribosomes
Endoplasmic reticulum (ER):
Series of flattened, membrane-bound sacs [cisternae]; continuous with outer nuclear membrane; rough ER with ribosomes; smooth ER without ribosomes
Rough ER transports proteins made on attached ribosomes [some of the proteins secreted from cell, some placed on cell surface membrane]; Smooth ER involved in making lipids for cell
Stack of membrane-bound, flattened sacs
Receives and modifies proteins from ER [may even add sugar molecules on them, how lovely]; packages modified proteins in vesicles to be transported [to cell surface or to be secreted]
Spherical or sausage-shaped; two membranes separated by fluid-filled space; inner membrane is highly folded to form cristae; central part is called matrix
Where ATP [adenosine triphosphate] is produced during respiration
Found only in plant cells and cells of some protocists; two membranes separated by fluid-filled space; inner membrane is continuous with elaborate network of thylakoids [flattened membrane sacs; stack of thylakoids = granum (plural grana)]; chlorophyll molecules present on thylakoid membranes and in intergranal membranes
Site of photosynthesis; light energy used to drive photosynthesis reactions, in which carbohydrate molecules are mode from carbon dioxide and water
Spherical sacs surrounded by single membrane
Contain powerful digestive enzymes to break down materials - white blood cell lysosomes to break down pathogens; acrosome in head of sperm cells to break down material surrounding egg
Organelles not surrounded by membranes
Tiny organelles [aww, babies]; some in cytoplasm, some bown to ER; each consists of two subunits
Site of protein synthesis; act as assembly line where coded information [mRNA] from nucleus is used to assemble proteins from amino acids
Small tubes of protein fibres [microtubules]; a pair of them next to nucleus in animal cells and someprotocists
Take part in cell division; form spindle fibres which move chromosomes during nuclear division