Organisms need carbon to make all sorts of biological molecules including lipids, carbohydrates, and proteins. Just like we saw with nitrogen and phosphorus, carbon is transferred around ecosystems in a cycle called the carbon cycle. The carbon cycle The Earth's atmosphere is about 0.04% carbon dioxide (CO2), which is where we will start the carbon … Read more
Not all muscles are the same. In this article we will look at the three types of muscle: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle Skeletal muscle is under conscious control, so is sometimes called voluntary muscle. There are two types of skeletal muscle fibres: fast twitch and slow twitch. Fast twitch fibres … Read more
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 fibre cells are a great example of how animal cells can be highly specialised for their function. In this article we will look at the structure of muscle fibre cells and how it relates to their function. Muscle fibres cells - structure and function The below diagram shows a cross-section of a muscle fibre … Read more
Cardiovascular disease is a non-communicable disease; it is not caused by a pathogen and cannot be passed from person to person. Most cardiovascular disease begins with atherosclerosis developing in an artery due to factors such as high blood pressure. In this article we will look at how atheromas develop, cardiovascular disease risk factors, and treatments. … Read more
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. … Read more
Control of body temperature is the first example of homeostasis we will look at in this series. For humans, normal body temperature is 37°C. It is important to maintain this temperature as it is the optimum temperature for enzymes involved in many metabolic processes such as respiration. Humans are endotherms, meaning that they control their … Read more
So far in this series we have looked at how enzymes work, what can affect the rate at which they work, and how their action can be inhibited. Today we are looking at coenzymes and cofactors: non-proteins that are needed in order for some enzymes to be able to catalyse their reaction. Coenzymes Coenzymes are … 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
