Prophase 1 – each chromosome appears in the condensed form with two chromatids. Homologous pairs of chromosomes associate with each other. The pairs cross over. this occurs when large, multi-enzyme complexes 'cut and join' bits of the chromatids together. The points where the chromatids break are known as chiasmata. This crossing over increases genetic variation and reduces the risk of a mutation causing a problem.
Metaphase 1 – the spindle forms and the pairs of chromosomes line up on the equator. Anaphase 1 – the centromeres don’t divide. One chromosome from each homologous pairs moves to opposite poles of the cell. The chromosome number is now half the original number. Telophase 1 – the nuclear membrane re-forms and the cells begin to divide. During the next interphase there is no further replication of the DNA. Metaphase 2 – new spindles are formed and the chromosomes line up on the equator. Anaphase 2 – the centromeres divide and the chromatids move to opposite ends of the cell. Telophase 2 – nuclear envelopes re-form and four daughter cells are formed with only 23 unpaired chromosomes meaning they are haploid cells. Ultimately 4 haploid cells are formed containing half of the original genetic material. An experiment analysing the effect of enzyme concentration on the initial rate of reaction10/6/2015 Equipment:
For this experiment we used the enzyme trypsin to break down milk. We used concentrations of 0.2%, 0.4%, 0.6% and 0.8%. We then placed the mixture of milk suspension and trypsin in a cuvette, which is transparent to allow light through. This is then placed in a colorimeter to measure the amount of light being absorbed depending on how much milk had been broken down. To begin with the milk suspension is cloudy meaning most of the light from the light source is absorbed by the mixture, however as the experiment continues, the milk is gradually broken down, creating a clearer solution, so that less light is absorbed by the mixture and more passes through and is detected by the colorimeter. Using a stopwatch we took measurements from the colorimeter every 20 seconds. In this way, we could compare the different concentrations of trypsin and how fast the milk was broken down for each. This would tell us how the rate of reaction differs with varying concentrations of enzyme. Analysis of results... Finding the initial rate of reaction using tangents to each curve: To work out the rate of reaction, I drew a tangent to the initial curves of each reaction and worked out the gradient… 0.2% - 0.43 0.4% - 1.2 0.6% - 1.9 0.8% - 2.35 I drew this bar chart to show the initial rate of reaction against concentration of trypsin Conclusion…
This experiment demonstrates some clear trends. Firstly, there is a steeper gradient, highlighting a faster initial rate of reaction, for the higher concentration of trypsin. To begin with, 0.2% has the lowest initial rate of reaction and takes the longest to reach completion. As the concentration increases, the initial rate of reaction increases and ultimately those reactions with a higher concentration will finish quicker. For example, 0.8% concentration has a much steeper gradient than 0.2% and it is also steeper than both the 0.4% and 0.6% concentrations. These results are due to more enzyme being involved in the reaction when the concentration is higher. A higher concentration means more of the solution is made up of enzymes, so the reaction will happen quicker and at a faster rate if more enzymes are present. Ultimately the enzyme lowers the activation energy, meaning more reactions can take place as the initial bonds can be broken at a lower energy. This means that temperature and pressure do not have to be high as the enzyme speeds up the reaction by a large amount, without being used up in the process. Overall, the higher the concentration, the more enzymes that are present in the mixture so more reactions can take place as the enzymes will assist more reactions, leading to a higher frequency of successful collisions, which consequently increases the rate of reaction. Experiment questions
After reading another article on news scientist, I understand just how important enzymes are in life. This article was based around allergy prevention by a specific enzyme known as A20.
Endotoxin is an abundant bacteria found on the surface of many species such as E.coli. This protein helps to calm down an overactive immune system so that we don’t react to every foreign species in our body. We are exposed to endotoxin constantly and it is the naturally occurring A20 enzyme which allows us to take advantage of this exposure. A20 controls inflammation as well as protecting against allergies. New born babies have the enzyme and at the start of their life it is this enzyme which helps train the immune system to prevent overreaction to bacteria that may not be harmful. Some children have the enzyme but due to chance mutation its work is disrupted and evidence shows how those children that have faulty A20 enzymes are more likely to develop allergies. News scientist carried out experiments involving mice to test the significance of this enzyme. They learnt that when A20 is present and functioning properly, exposure to endotoxin is very beneficial. Both the protein and the enzyme have to be present to prevent overreaction by the body. Studies show that those with an absence of A20 are more likely to suffer from allergic reactions due to the body overreacting to harmless microbes, such as dust. One thing they learnt from the investigations was that just being exposed to endotoxin is not enough and that both A20 and the protein must be combined to achieve benefits. I thought this was a very interesting article as it combines the benefits of enzymes with day to day problems and it helped me to grasp the idea that allergies are caused by an overreaction by the body’s immune system and how you are more likely to be allergic to certain microbes if you lack certain enzymes. https://www.newscientist.com/article/dn28129-key-enzyme-helps-country-kids-ward-off-allergies-and-asthma/ This is a common disaccharide formed when glucose and galactose are joined in a condensation reaction. This science article relates to the enzyme that breaks down lactose which is found in milk. I find this interesting that a large number of people are intolerant to lactose due to the absence of the enzyme lactase. This is linked to my biology course as it combines both biological molecules and more specifically carbohydrates as well as biological catalysts; enzymes.
The ability to digest lactose requires the enzyme lactase. Some people don’t have this vital enzyme and as a result the lactose passes into the colon where it feeds bacteria which ultimately generate gas and fluid, this can lead to bloating and cramps. This is more commonly known as lactose intolerance. Lactose intolerance is usually diagnosed before the age of 16, however some can develop the condition temporarily. Only one third of adults can digest milk because most people stop making the enzyme that is needed to break down lactose. https://www.newscientist.com/article/dn27938-everything-you-need-to-know-about-lactose-intolerance/ |
Ciara Branagan
Archives
October 2016
|