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 →
In the first article about the kidneys, we learnt how blood is filtered and substances are reabsorbed in the Bowman's capsule and the proximal convoluted tubule. Today we will focus on the loop of Henle, distal convoluted tubule, and collecting duct, and look at how blood water potential is controlled. The loop of Henle, distal... Continue Reading →
The kidneys are important organs for maintaining blood water potential and excreting waste products from the blood. In this article, we will look at the structure of the kidneys and how substances are filtered out and reabsorbed into the blood using ultrafiltration and selective reabsorption. Kidney structure The kidneys have an outer layer called the... Continue Reading →
We know that nerve impulses are carried along neurones in a wave of depolarisation. But how does a nerve impulse get transmitted from one neurone to the next? Well, that is where synapses come in. Structure of synapses Synapses are the microscopic gaps between neurones. The neurone before the synapse is called the presynaptic neurone,... Continue Reading →
In the last article we learnt that neurone cell membranes are polarised at rest (when they are not being stimulated). However, when a stimulus is detected a nerve impulse must be sent along the neurone. Today we will look at the sequence of events that happens during an action potential and how ion channels bring... Continue Reading →
The nervous system communicates information by sending nerve impulses. In the last article we saw how impulses are generated at receptors in response to a stimulus. Now the impulses must be transmitted by neurones. In this article we will look at some of the different types of neurones found in the nervous system, and see... Continue Reading →
Translocation is the movement of dissolved substances (also called solutes or assimilates) through the phloem vessels. If you haven't already, make sure to read about the structure of the phloem vessels here first so you've got a good grounding to take this topic further. Source to Sink Solutes move from a source to a sink.... Continue Reading →
So far in the exchange and transport series we have mainly been looking at exchange and transport of gases. However, organisms also need to absorb nutrients such as glucose and amino acids so they can carry out processes like respiration and protein synthesis. In this article we will cover how large food molecules are broken... Continue Reading →
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... Continue Reading →
