Hi, I’m Aleks and I study Biochemistry at the University of Surrey. It’s my fifth and final year of the course, with an exciting project set out for me for the upcoming semester. I will be working alongside my lovely mentor and supervisor Natalie Riddell investigating effects of the endocrine system on immunometabolism. Before you accuse me of speaking gibberish, bear with me so I can explain what my project has to do with you…
In today’s society, stress is an inevitable part of life. Whether it’s the morning rush after a late night, work drama, or catching a cold, what seems to be our ‘bad luck’ or just the case of ‘the Monday’s’ can actually be affecting our health. The term ‘immune system’ is familiar and well known, from vitamin adverts to guest appearances on smoothie bottles, but have you ever wondered how it works and why sometimes do we get sick so easily?
The immune system is composed of an army of different cells, all working together to fight invading bacteria, pathogens, and allergens which may cause that annoying runny nose on a flowering spring’s day. The immune cells circulate in our blood observing their surroundings looking for foreign antigens- particles associated with bacteria and general things which should not be in the body, and once they’re found, the immune cells recognize, activate, and attack! However, a lot of energy is used up doing this, so where does this energy come from?
When speaking about metabolism, most people automatically think of eating food and digesting it, albeit not wrong, zooming in on this concept shows every cell of the body absorbs molecules, processes them and turns it into a useful energy source. So, allow me to get into more detail about the basics of how the cells of your immune system metabolise.
Carbohydrates which we eat (such as rice, potatoes, or bread) are composed of long chains of single sugar molecules, most simple and known one being glucose. Glucose enters the cells through glucose receptors such as GLUT1 or GLUT4.
GLYCOLYSIS – Splitting of the glucose
The glucose is processed in a series of reactions known as glycolysis, creating molecules called adenosine triphosphate (aka ATP) and some pyruvate as seen in the diagram above. This process can occur both in presence of oxygen and without, converting the glucose into lactate instead. ATP is used directly for energy whereas pyruvate enters the mitochondria, an organelle in the cell which turns it into an acetyl coenzyme A molecule in the process of link reaction.
But what are reactions?
Before we get all confused, reaction steps reassemble the carbons, hydrogens, and water atoms of which the sugars are composed of, however nearly each step of the process either adds components from somewhere or gives components away which cannot simply be left behind. The leftover atoms are usually scooped up by molecules in the mitochondria which bind and carry the atoms to places where they can be of use, and knowing this, I can tell you all about oxidative phosphorylation or OXPHOS!
The citric acid cycle
Acetyl CoA from our previous reaction combines with oxaloacetate which is a resident molecule of the citric acid cycle from the previous round of processes. During the upcoming changes is where the carbons start falling out of the cycle and co-factor molecules (the carriers I mentioned earlier) can carry the donated hydrogen atoms to yet another stage of cell metabolism, the electron transport chain.
The electron transport chain
At electron transport chain, all the leftover atoms play the most important part in cellular energy production as they split and get deposited in different places. The hydrogens carried by the previously mentioned co-factors, split into electrons and hydrogen ions (H+, aka protons) as seen on the figure above. This occurs by a process called oxidization, facilitated by the complexes (C) of the electron transport chain. The “empty” co-factors can return to the TCA cycle to pick up more hydrogen atoms.
The deposited hydrogen ions (H+) create a gradient between the two mitochondrial membranes, and with this buildup, these protons tend to flow down a channel of complex V (aka ATP synthase; synthesis being another word for creation of a whole from two parts) where there’s less of them, powering the rotation of complex V. This generates the force required to bind adenosine diphosphate with another phosphate, the building blocks of ATP.
However, this process does not always work as it should, and many factors in the body such as stress can affect the pathways by either speeding it up, slowing it, or even completely blocking any pathway leading to cell death.
But what is stress and why is it such a big deal? We usually associate stress to be a psychological response, however it has a massive effect on the body as well as our mind. The brain recognises stressors such as lack of sleep, or a need for increased level of alertness then send signals to storage organs which release chemicals aiming to adapt the body for said situation. For example, when frightened, a fight or flight response kicks in due to release of adrenaline, you can physically feel it in your stomach. These same chemicals can affect how your immune cells work and create their energy; however nobody knows what the processes are for these events, and the aim of my project is to find that out! 😊
So next time you miss the bus,
Don’t worry, stay happy, love from: