Tutor profile: Jamie B.
What are the differences between insulin and glucagon, and how do they relate to glucose metabolism.
To start with their similarities, both of these are signalling molecules that our bodies use to regulate blood sugar levels. They essentially work as opposites - insulin signals that our blood sugar levels are high, while glucagon is used to signal that our blood levels are low. I like to remember this by saying GLUCAGON is used when the "GLUCose is GONe." When blood sugar levels are high, our bodies have a ready supply of sugar to break down. In this case, our bodies prefer to take these sugars and store them in the cell. Insulin does this by binding to receptors on the cell, which signals the cell to take in sugars and fix them in the cell as fats. These fats can later be broken down to be used by the body as long-term energy stores. When blood sugar levels are high, our bodies demand sugar to break down into energy. Glucagon promotes two processes. First of all, it promotes the breakdown of fats in our bodies, utilizing those sugars that were stored away thanks to insulin. Second, it promotes gluconeogenesis, a process where glucose is recreated from its breakdown products. This is a vital process, because some of our cells - like our brain cells - can only be powered by the breakdown of glucose. Glucagon, therefore, is vital to powering our bodies when we don't have an immediate source of sugars from our diet.
Subject: Basic Chemistry
I don't understand Gibb's free energy. What does it mean and how to I solve for it?
Gibb's free energy (ΔG) is a term used to describe how readily a reaction will occur. You might have heard of this is terms of "spontaneous" and "non-spontaneous" - a spontaneous reaction occurs on its own, while a non-spontaneous process needs energy to occur. Getting sugar to dissolve in your coffee is a spontaneous process - no energy input is required to get it to dissolve. Boiling water on the stove, however, is non-spontaneous - you'll need to provide energy as heat to make that happen. The most common way to solve for Gibb's free energy is through the formula ΔG=ΔH−TΔS. To break this down into English, this equation translates as (the change in free energy) = (the change in enthalpy) minus [(the temperature in Kelvin) times (the change in entropy)]. The strange thing about calculating ΔG is that a negative value makes it a spontaneous process, and a positive value makes it a non-spontaneous. However, this makes sense when you break it down. The ΔG is essentially measuring how much energy is needed to make a reaction occur. So saying a reaction needs negative energy means it doesn't need energy at all - in fact, it releases energy! So it makes sense that a spontaneous process requires a negative input of energy. Similarly, a reaction that needs a positive amount of energy means that the energy needs to be supplied - therefore making it non-spontaneous.
What is meant by the "electron transport chain," and why is it important to biology?
The Electron Transport Chain (ECT) is a vital mechanism because it allows our bodies to generate a powerful energy molecule known as ATP. The ECT is located in the mitochondria, an organelle located within our cells. To power the ECT, our mitochondria use the byproducts of sugar breakdown (AKA, glycolysis and the citric acid cycle) to bring electrons into the mitochondria and pass them across a series of complexes to liberate small packets of energy - hence why it is called an electron transport chain. These packets of energy then pump protons across the membrane against their chemical and electrical gradient, creating a build-up of energy known as a "proton-motive force." This force is then used by a protein known as ATP Synthase, generating ATP. The ETC is a complex yet elegant system that allows the mitochondria to function as the "powerhouse" of the cell.
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