Question

A flattened disc-like structure present in the chloroplast is
A. Stroma
B. Thylakoid
C. Loculus
D. Margin

Answer 1

Hint: Chloroplast is one of the cell organelles which is found in the plants, these are generally biconvex in shape, however, this shape may differ in different plants like a saucer-shaped, etc and is generally found in the mesophyll of the leaves.

Complete answer:
> The chloroplast contains inner and outer membrane and intermediate space.
> The inner part of the chloroplast consists of stacks of thylakoids called grana and it also contains the dense fluid called the stroma.
The thylakoid contains the pigment called chlorophyll, helpful for the plants for photosynthesis.
Parts of the chloroplast
> The outer membrane (envelope): This is the outer side membrane and usually it is permeable for smaller ions and impermeable outer large ions.
> Intermediate membrane: This is located between the outer and inner membrane and it is usually 10 to 20 nm.
> Inner membrane: This membrane usually surrounds the stroma and it helps in the movement of ions in and out and it also contains lipids, fatty acids, etc.
> Stroma: This is fluid in nature, it is alkaline, protein-rich, and within the stroma, the things like chloroplast DNA and proteins and ribosomes are all present in the stroma fluid.
> Thylakoid system: The stacks are arranged to form the thylakoid, they are generally flat and disc-shaped, they are suspended in the stroma, and these thylakoid space consist of a pigment called chlorophyll, it is the place where light reactions of photosynthesis take place, and this thylakoid arranged as 10 to 20 stacks called grana.
The peripheral reticulum is also a part of the chloroplast present in some plants only.

So from all the above explanations, Thylakoid is the right option.

Note:
In the chloroplast, all the light-dependent and light-independent reactions of photosynthesis take place, and it is responsible for the synthesis of food, and synthesis of so many products, it also helps in photorespiration and plants usually lack defense cells, but this chloroplast with and endoplasmic reticulum act as defense cells.