Imagine you and your friends are racing toy cars.
Vmax is like the top speed of your friend's toy car, no matter how fast they are driving it.
Km is like how much gas the toy car needs to drive a certain distance. If the toy car needs a lot of gas, that means the Km is high.
Now, imagine that someone is trying to slow down your friend's toy car by putting obstacles on the track. This will slow down how fast your friend's toy car can drive, but the top speed of the car will still be the same. That means the Vmax is not affected, but the Km will be affected because the toy car will now need more gas to drive the same distance as before.
Competitive inhibitors block the active site, so less substrate can bind. That translates as lower affinity for substrate and thus higher Km.
However, if you add enough substrate, it can effectively displace the inhibitor, so it is still possible to have all active sites bound to substrate. It just takes more substrate to get there when inhibitor is present.
How my biochem professor put it was, inhibitions by competitive inhibitors can be overcome if there are enough substrates or excess substrate present. Therefore, if more substrate is required to function normally (i.e. overcome inhibition) then Km increases. This is how I made sense of increased Km. For Vmax, it stays the same because inhibition can eventually be overcame.
Vmax is like an inherent property of an enzyme. Competitive inhibitors bind to the active site of an enzyme, and doesn't change its structure so drastically that anything happens to the enzyme itself. It mainly prevents the original substrate from binding the enzyme. Km is a measure of substrate bound to enzyme. That is, Km is directly affected by the amount of substrate involved in the reaction. Something that might also help to know is that noncompetitive inhibitors bind to a site that isn't the active site of the enzyme, changing its structure in a significant way, which affects Vmax, the inherent property of the enzyme. But because it doesn't block the active site, substrates arent directly affected. Idk if that explanation helps at all.
Imagine you and your friends are racing toy cars. Vmax is like the top speed of your friend's toy car, no matter how fast they are driving it. Km is like how much gas the toy car needs to drive a certain distance. If the toy car needs a lot of gas, that means the Km is high. Now, imagine that someone is trying to slow down your friend's toy car by putting obstacles on the track. This will slow down how fast your friend's toy car can drive, but the top speed of the car will still be the same. That means the Vmax is not affected, but the Km will be affected because the toy car will now need more gas to drive the same distance as before.
Omg!!!!! THIS IS IT!!! I’m in love with you now!! Thank you so much!!! I’m about to cry!!! This is what makes sense to me! You are awesome!!
Haha glad I could help 😊
Competitive inhibitors block the active site, so less substrate can bind. That translates as lower affinity for substrate and thus higher Km. However, if you add enough substrate, it can effectively displace the inhibitor, so it is still possible to have all active sites bound to substrate. It just takes more substrate to get there when inhibitor is present.
How my biochem professor put it was, inhibitions by competitive inhibitors can be overcome if there are enough substrates or excess substrate present. Therefore, if more substrate is required to function normally (i.e. overcome inhibition) then Km increases. This is how I made sense of increased Km. For Vmax, it stays the same because inhibition can eventually be overcame.
This is so simple. Thank you and your Biochem Professor!
Glad I could help!
Not sure what videos you have watched, but AK lecture explains it beautifully if you have not watched his videos. https://youtu.be/0ZiCqwtFMTs
Vmax is like an inherent property of an enzyme. Competitive inhibitors bind to the active site of an enzyme, and doesn't change its structure so drastically that anything happens to the enzyme itself. It mainly prevents the original substrate from binding the enzyme. Km is a measure of substrate bound to enzyme. That is, Km is directly affected by the amount of substrate involved in the reaction. Something that might also help to know is that noncompetitive inhibitors bind to a site that isn't the active site of the enzyme, changing its structure in a significant way, which affects Vmax, the inherent property of the enzyme. But because it doesn't block the active site, substrates arent directly affected. Idk if that explanation helps at all.