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. Before beginning this article, make sure you are happy with the different parts of a muscle fibre cell. Sarcomeres Myofibrils are made up of two main protein filaments: actin... Continue Reading →
Muscle Fibre Cells – Muscles Ep 1
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 fibre cells - structure and function The below diagram shows a cross-section of a muscle fibre... Continue Reading →
Transforming bacteria – Gene Technologies Ep 3
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. Transforming bacteria 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 →
Control of Blood Glucose – Homeostasis Ep 3
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 in the blood is affected by factors such as eating and exercise, and must be brought back to the normal level of about... Continue Reading →
Synapses – Nervous Communication Ep 5
We know that nerve impulses are transmitted 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 →
Neurones and Resting Potential – Nervous Communication Ep 2
The nervous system communicates information by propagating 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 →
Barriers to Infection – Immunity Ep 5
In order for a pathogen to enter the body and cause a disease, it must pass through the body's non-specific defences. The barriers to infection are non-specific because they respond to all pathogens in the same way. Infection routes There are four main routes with a pathogen can take to enter the body: The digestive... Continue Reading →
Developing Immunity – Immunity Ep 2
In the last article we looked at how the immune system responds to a pathogen which is encountered for the first time. This is the primary immune response. However, if the same pathogen enters the body again in the future, the immune system is able to respond more quickly because it is prepared. In this... Continue Reading →
The Immune Response – Immunity Ep 1
Sometimes the body comes under attack from pathogens (microorganisms that can cause disease). If pathogens get into our body, it is down to our immune system to spring into action and destroy them. In this article we will be looking at how foreign antigens trigger our immune response, and how that results in the pathogens... Continue Reading →
Crossing Over and Independent Assortment – Cell Division Ep 5
In the last article we looked at meiosis - the type of nuclear division that produces haploid gametes in the reproductive organs. Today we're going to look at how meiosis can produce genetic variation in the gametes, and therefore genetic variation in offspring after the gametes fuse at fertilisation. We will also finish off by... Continue Reading →
