Back to: MICROBIOLOGY 200 LEVEL
Welcome to class!
My ever-curious and determined learner, I’m so glad to see you back in class! You’re growing into a true microbiologist, one step at a time. Today, we’re going to shine a light on something that helps bacteria stay smart and economical — Inducible vs. Repressible Systems. Get ready, because this lesson will make you appreciate just how intelligent even the tiniest cells can be!
Inducible Vs. Repressible Systems
Let’s start with a familiar situation: In your house, do you leave the fan or generator running all the time even when nobody is using it? Of course not! You only switch things on when you need them — and turn them off when they’re not needed. That’s the same logic that cells follow when it comes to turning genes on and off.
In bacteria, some genes are controlled by systems that work like switches. These systems can be induced (switched on when needed) or repressed (switched off when not needed). These systems help cells conserve energy and resources — just like how your family avoids waste during tough times like fuel scarcity!
Inducible Systems
These systems are usually off but can be turned on (induced) when a specific molecule is present.
The classic example is the lac operon — which turns on only when lactose is available.
In the absence of lactose, a repressor blocks the genes from being expressed.
When lactose is present, it binds to the repressor and removes it, allowing the genes to be expressed.
Think of this like turning on your blender only when there’s fruit inside. There’s no point running it if you’re not making a smoothie!
Repressible Systems
These systems are usually on by default but can be turned off (repressed) when the product is in excess.
A good example is the trp operon — responsible for making tryptophan.
When there’s enough tryptophan, it acts as a co-repressor and helps switch the system off.
This prevents the cell from wasting resources making more than it needs.
This is like cooking beans — once the pot is full, you turn off the stove. No need to keep cooking when there’s already enough food.
Let’s use a small akara joint as an example.
Inducible system: The akara seller starts frying only when customers show up — no beans, no frying. That’s like the lac operon.
Repressible system: She keeps frying until there are enough akara balls. Once the table is full, she stops — that’s the trp operon.
Both systems help her manage her gas and ingredients wisely — just like bacteria manage their gene expression!
Summary
- Inducible systems are normally off and are turned on in response to a specific substance (e.g. lac operon with lactose).
- Repressible systems are normally on and are turned off when the product becomes excessive (e.g. trp operon with tryptophan).
- Inducible systems save energy by only producing enzymes when needed.
- Repressible systems prevent overproduction by stopping once enough product is available.
- These systems are great examples of how bacteria efficiently manage resources.
Evaluation
- What is the difference between inducible and repressible systems?
- Give one example of an inducible system and explain how it works.
- What molecule acts as a co-repressor in the trp operon?
- Why is it important for cells to regulate gene expression?
- Use a real-life scenario from your environment to explain an inducible system.
Every time you take a step like this, you get closer to mastering the beautiful science of life. You now understand how tiny cells manage their resources just like humans do — how amazing is that? Keep your head high and your curiosity sharp. Afrilearn is here with you all the way. See you in the next exciting lesson — your brilliance is showing!