To wrap up the muscle series we are looking at neuromuscular junctions - the synapses between motor neurones and muscle fibre cells. This article will relate closely to the synapse article, but there are some differences between cholinergic synapses and neuromuscular junctions. Neuromuscular junction structure There are three main differences between neuromuscular junctions and a... Continue Reading →
Muscle contraction requires a large amount of energy, meaning that a constant source of ATP is needed. In this article we will look at the three sources of ATP which muscle fibre cells can use. Phosphocreatine ATP has to be made by adding a phosphate group (Pi) to ADP. In the ATP-phosphocreatine system, the phosphate... Continue Reading →
Muscle contraction is a tricky bit of A-Level biology. There are lots of new terms to learn and a complex process to get your head around. Make sure to review it regularly so that it sticks in your brain. Before beginning this article, make sure you are happy with the different parts of a muscle... Continue Reading →
HIV (human immunodeficiency virus) is a virus which can eventually lead to development of AIDS (acquired immunodeficiency syndrome). However, it is not the virus itself which causes AIDS symptoms; HIV weakens the immune system, meaning other infections can take hold more easily. In this article we will look at HIV structure, replication, and development of... Continue Reading →
The aim of this practical is to investigate the rate of enzyme-controlled reactions. The details of the practical itself vary depending on what the enzyme, substrate, and product are. Let's use catalase as an example. Catalase is an intracellular enzyme which catalyses the conversion of toxic hydrogen peroxide (the substrate) into oxygen and water (the... Continue Reading →
So far in the genetic engineering journey we have learnt how to isolate or produce a DNA fragment, and amplify it in vitro using PCR. Bacterial transformation is a method to amplify a DNA fragment in vivo (in a living organism), and to engineer bacteria to produce a protein. In this article we will look... Continue Reading →
Once a DNA fragment has been isolated or produced (see the last article), the next step is often to produce many copies of it. One common way to do this is to use the polymerase chain reaction, which is a fairly simple process that can be automated. In this article we will look in detail... Continue Reading →
This article begins a new series about gene technologies. Many gene technologies, especially recombinant DNA technologies, begin with the need to isolate or make DNA fragments. We will look at three different ways that this can be achieved. Restriction enzymes This method allows DNA fragments to be "cut out" of existing DNA. Restriction enzymes, sometimes... Continue Reading →
Control of blood glucose is very important. Sufficient glucose must be delivered to cells for respiration, but too much glucose can eventually result in coma or even death. The concentration of glucose is affected by factors such as eating and exercise, and must be brought back to the normal level of about 4mmol/L to 5.5mmol/L.... Continue Reading →
Homeostasis is the maintenance of a stable internal environment. The conditions inside the body must be stable so that cells can function properly. For example, if the temperature or pH are too high, enzymes can become denatured. It is also important to maintain blood glucose concentration and water potential, which we will look at in... Continue Reading →
