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 … Read more
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 … Read more
In the last article we left photosynthesis at a point where ATP, reduced NADP, and oxygen had been produced in the light-dependent reaction. Oxygen is a waste product of photosynthesis, however the ATP and reduced NADP are used for the light-independent reaction. So although light energy isn't specifically needed for any reaction in this next … Read more
Photosynthesis is the process used by plants and other photosynthetic organisms to make their own glucose. The glucose can then go on to be used in respiration, stored as starch, or used in other reactions. Photosynthesis requires light energy, but it is actually only the first stage which is light-dependent. We will focus on the … Read more
Anaerobic respiration happens when there isn't enough oxygen present for aerobic respiration to continue. Different types of organism use different pathways - lactate fermentation or alcoholic fermentation. For both pathways, the amount of ATP produced is much lower than in aerobic respiration because the only ATP produced comes from glycolysis (2ATP per glucose molecule). You … Read more
We've reached the final stage of aerobic respiration - oxidative phosphorylation. This step takes place using proteins in the inner mitochondrial membrane. Now we will find out what all the reduced NAD and reduced FAD produced in glycolysis, the link reaction, and the Krebs cycle is used for. Oxidative phosphorylation The coenzymes NAD and FAD … Read more
The Krebs cycle has many names. Sometimes it is called the tricarboxylic acid (TCA) cycle or the citric acid cycle. But whatever name you give it, it's an important part of aerobic respiration. In the last article we covered the first two stages of aerobic respiration (glycolysis and the link reaction). We ended the link … Read more
In this series we are going to be looking at respiration. This is the process that releases energy from glucose to produce ATP. In the first few articles we'll be focusing on aerobic respiration (which uses oxygen) and then we will cover anaerobic respiration (which doesn't use oxygen) in the last article. Aerobic Respiration Equation … Read more
So far we have looked at the passive movement of substances across cell membranes by diffusion and osmosis. Sometimes substances need to move against a concentration gradient, which is when active transport comes into action. Active transport Active transport uses energy from ATP to transport substances from an area of low concentration to an area … Read more
Today we are looking at adenosine triphosphate, often just abbreviated to ATP because as with most scientific terms, it's a bit of a mouthful. This molecule is very important in providing a quick source of energy for processes in cells. Let's have a closer look at its structure and function. Structure of ATP ATP is … Read more
