Delivered on: 16 OCTOBER 2023
The chloroplast, a vital organelle found in plant cells, is the green powerhouse that drives photosynthesis. This complex structure is designed to capture sunlight and convert it into chemical energy, a process that sustains life on Earth. In this lecture, we will delve into the intricate details of the chloroplast's anatomy, exploring its various components and their essential functions in the photosynthetic process. By understanding the chloroplast's structure, we can gain a deeper appreciation for the remarkable efficiency and complexity of nature's solar energy conversion system.
Video Transcript:
Okay so light reaction okay. We have covered 9.1 until 9.3 now we're going to continue from 9.4 until 9.9.
I do not know maybe we'll you only finish up to 9.5. Let's see let's see.
Number one, what you need to understand is the organization of photosynthetic apparatus.
This is very important this is the basic of photosynthesis you need to understand photosynthesis is not happening in just about anywhere.
It is happening in a specific location inside a cell okay and inside a cell there are many organelle, meaning that membrane bound structure.
Sub cellular compartment of a cell okay and there are many there are nucleus there are vacuums, there are mitochondria and so on.
We are interested with a type plastid okay so there is a group of organelle collectively it's called plastid one type of plastic that we are interested today which is the chloroplast. Okay which is this guy.
So this is a cross section from electron microscope you can see that chloroplast why is it not green?
This is electron microscope, no colour okay.
Actually the reason you see the colour green for the chloroplast is because you are dealing with visible light.
When the sample is in the microscope people are not using a visible light anymore use Argon gas so no colour.
But the give of the charges and signal so that the computer can interpret, and you get this image.
Right there are important structure that you need to understand here this is look a bit boring right.
Let's use the cartoon part of it so in the plant cell you got this plant cell.
See? many many many blobs and then we are interested with these green blobs here.
Okay enlarge this and then you get this
Number one chloroplast double membrane please remember that.
It's called the outer membrane and inner membrane that enveloped the entire thing.
Okay and in between the membrane there is an intermembrane space and this is very important because not all substance can go in and out into the chloroplast.
It's kind of Highly regulated okay and also important because this is where you where the plants will eventually decide to have more sugar transported out of the cells or otherwise.
Okay so inside the chloroplast now you can see the stacking of pancake here the green pancake here yeah
So we focus in here we enlarge this here I know that maybe you have learned this before the concept of grana, granum that kind of thing
But this time we're going to correct your understanding with the correct labelling.
Okay so a stack of this thing is called granum one pancake 2 pancake 3 4 5 6 the whole thing is called granum. Okay one pancake is called a thylakoid disc. It's not written disc there but it's called disc.
Okay and this kind of granum when you go deeper in learning photosynthesis it's actually called as either grana lamellae or stroma lamellae
Meaning that depending on the location and the shape of this structure it will determine later what kind of biochemical process happens to it.
Look at here this collectively you call it grana lamellae right remember grana lamellae stack of thylakoid this is where the photo system is located
you will learn later that in order to capture and the light plants have two important photo system.
Photo system to do what capture and utilize okay so the one of the photosystem is located primarily in this grana lamellae and what about these connecting bridges here.
This is called the stroma lamellae okay it is not part of the pancake but it's rather protruding out of the structure.
Okay look at this this is actually not individual disc even though I call this just now it's actually like your intestine.
Your intestine is a long tube right 6 M or more so that tube is arranged in such a way does it look like your intestine.
So this tube when it is arranged upon on top each other in the that folding manner it gives the illusion of pancake stacking but it's actually a one long tube like your intestine.
Okay right so what what is what other other thing is important
The stroma what is the stroma the stroma is the environment inside the chloroplast the soup inside the chloroplast.
If the soup in the cell we call cytoplasm the soup in the chloroplast we call stroma okay not stoma, stoma are the microscopic pores on the leaf surface.
That's not it this is stroma okay right yeah get it?
I do expect for you to be able to draw this okay so I do not know this is the time if you don't like drawing this is the time to like it a bit right.
Reference book: Plant Physiology and Development 7th Edition
by Lincoln Taiz, Ian Max Møller, Angus Murphy, Eduardo Zeiger
Full video: https://www.youtube.com/watch?v=dYs_TczAsM0
Attribution 4.0 International — CC BY 4.0 - Creative Commons
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