Biology FAQ - 3GJ by

Eg. Why are the mitochondrion and chloroplast considered semi-autonomous organelles?

nadya_loh_yu_shuen — 2025-01-23 05:14:00 UTC

Misconception: Are protein ONLY present in muscle cells/ animal cells?

nadya_loh_yu_shuen — 2025-01-27 09:03:19 UTC

No! This is not true. Proteins are found in animal cells AND plant cells. Since animal and plant cells perform different functions, the proteins found within the respective cells are also different. Similarly, the proteins found in a muscle cell are also different from the proteins found in a liver cell.

TLDR: Proteins are found in BOTH plant and animal cells!

Comparison between the electron micrograph of a chloroplast and a mitochondrion

nadya_loh_yu_shuen — 2025-01-27 09:20:17 UTC

It is important for you to be able to distinguish between a mitochondrion and a chloroplast.

Take note of the

1) Folded Inner membrane: Cristae (plural)

This is only present in the mitochondrion. The chloroplast does have an inner membrane that encases the stroma. BUT the inner membrane is NOT folded.

2) Presence of stacks of thylakoids

The disc shaped structures present in stacks are only found in chloroplast
Each disk is called the thylakoid
A stack of thylakoids is called the granum
You will notice that the thylakoids are all interconnected with each other
On the thylakoid's MEMBRANE (meaning the membrane of the disc like structure), you can find photosynthetic pigments such as (chlorophyll)

What are lysosomes?

nadya_loh_yu_shuen — 2025-01-27 09:22:47 UTC

You may notice this organelle appearing in your notes and assignment as well. Lysosomes contain enzymes (which are made up of proteins) that break down other organelles/ cell. For example, if I have an organelle that is damaged beyond repair, the lysosome will fuse with it, release its enzymes and essentially "kill" and "digest" the organelle.

2025-02-08 05:09:42 UTC

why does skin get wrinkly in water? Do the cells not pop?

2025-02-24 14:23:14 UTC

what is the definition of resolving power?

and

what is the difference between resolving power and resolution?

What is the induced fit model and how does it differ from the lock-and-key hypothesis?

nadya_loh_yu_shuen — 2025-03-05 00:28:05 UTC

We have learnt that the lock and key hypothesis is an easy way to represent enzyme specificity since it very clearly shows how the substrate (key) fits perfectly into the enzyme (lock)'s active site (key hole).

However, we also discussed its limitations such as

1) The key leaves the lock unchanged, but when products are formed and leave the enzyme, they are physically and chemically different from the reactants!

2) This also means that the substrate(s) has to be 100% complementary to the enzyme's active site! This may not be the case ALL the time. Does this then mean that if the substrate(s) are/is not 100% complementary to the active site, then the reaction cannot be catalysed?

Hence, the induced fit model has been introduced! The active site in the induced fit model is flexible, when the substrate binds, the enzyme changes its 3-Dimensional shape slightly such that its active site fits around the substrate better. This slightly change stabilises the interaction and make the reaction more efficient.