Enzyme Structure and Function
Enzymes are globular proteins that act like molecular machines, each designed for a specific job. Think of them as highly specialised tools in your body's toolkit. They have an active site where their target molecule (called the substrate) fits perfectly, like a key in a lock.
There are two main types you need to know about. Intracellular enzymes work inside your cells - catalase is a great example that breaks down harmful hydrogen peroxide into harmless oxygen and water. Extracellular enzymes work outside cells, like amylase in your saliva that starts breaking down starch the moment you bite into a sandwich.
The induced fit model explains how enzymes actually work. When the substrate approaches, the active site doesn't just sit there - it changes shape slightly to create the perfect fit. This flexibility is what makes enzymes so effective at their jobs.
Key insight: Enzymes don't just speed up reactions randomly - they lower the activation energy needed, making reactions happen at body temperature that would normally need intense heat.
Factors Affecting Enzyme Activity
Temperature has a massive impact on how well enzymes work. More heat means molecules move faster and collide more often with the active site. However, there's a sweet spot called the optimum temperature - go beyond this and the enzyme denatures (permanently changes shape), becoming completely useless.
The Q10 value is a handy way to measure this - it shows how much faster a reaction goes when you raise the temperature by 10°C. Most enzyme reactions roughly double in speed with this temperature increase.
pH levels matter just as much. Each enzyme has an optimum pH where it works best. Stray too far into acidic or alkaline conditions and the enzyme's shape gets distorted, making the active site ineffective.
Concentration also plays a crucial role. More enzymes mean more chances for substrate molecules to find an active site. However, once all active sites are occupied, adding more substrate won't help - you've hit the maximum reaction rate.
