• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

AS and A Level: Molecules & Cells

Browse by
Rating:
4 star+ (48)
3 star+ (116)
Word count:
fewer than 1000 (407)
1000-1999 (659)
2000-2999 (307)
3000+ (276)
Submitted within:
last month (3)
last 3 months (3)
last 6 months (3)
last 12 months (7)

Meet our team of inspirational teachers

find out about the team

Get help from 80+ teachers and hundreds of thousands of student written documents

  1. 1
  2. 14
  3. 15
  4. 16
  5. 55
  1. Biology Coursework on Tissue Engineering

    For tissue engineering to be carried out you need to understand the cell cycle. This is explained below. The cell cycle is a necessary part of tissue engineering as it makes duplicate copies of cells that will later be used for different tissue parts of the body. The cell cycle The cell cycle consists of two parts, interphase and mitosis. The first part of interphase is the G1 phase also known as the first gap phase. Here the cell grows; new organelles and proteins are made. In the S phase, also known as the synthesis phase, the cell replicates DNA and prepares the cell so that it is ready to be divided in mitosis.

    • Word count: 1886
  2. What Factors affect the rate of enzyme reaction

    Aim: To investigate how and why different levels of pH affect the rate of enzyme reaction, when using a combination of Catalase with Hydrogen Peroxide, and modifying the pH of an acid-alkali solution. Hypothesis: I predict that for each of the different levels of pH, there will be different results. pH 7 is the level in which the acid and base substances are neutral, and is the physiological pH of most cells in the human body. For these reasons, I predict that the catalase will react best at pH 7, and the rate of reaction will be highest.

    • Word count: 1816
  3. How Do Hormones and Other Secretions interact in Human Digestion?

    amylase (ptyalin) initialises the carbohydrates digestion and has an effectiveness of 5 to 50%, depending on how fast the food is passed through the mouth and oesophagus; lingual lipase contributes to the digestion of fat; blood group antigens; (Bray et al, 1999) lysozyme; hydrolyses bacterial membranes; and immunoglobulin (antibodies) act on micro-organisms (Berne et al, 2004) b) Gastric (stomach) secretions: The gastric mucosa, containing cardiac glandular (mucus-secreting cells), glandular (acid-secreting cells), and pyloric glandular (G cells) regions (Berne et al, 2004), produce 2-3 L of gastric juice each day, which consists of: hydrochloric acid necessary for gastric enzymes activation, denaturising

    • Word count: 1797
  4. Car Quotation System-Implementation

    I entered numbers in column A, which will be needed later to lookup the multipliers. In column B I entered the different multipliers and in column C, I entered the multiplier figure. Setting up the input controls on quotes worksheet. This is the major worksheet of the system, and takes information from the groups and multipliers sheets and works out the quotation. I entered the labels for the customer's title, forename, surname, address, postcode and telephone, In C2 to C8. I also entered the labels for the customers' s*x, age, car, area and type, in C11 to C20.

    • Word count: 1819
  5. Are mobile phones more of nuisance than a benefit?

    Similarly, even through average cell phones we can store thousands of our favorite musical tracks, many videos and listen and watch them whenever we like. So, recent cell phones are computer, walkman, TV, MP3 player and camera, all in one in a tiny device, bringing joy and effectiveness in our personal and business lives.-118 Likewise, satellite phones make us able to contact every phone user wherever we are on the surface of the earth be it at Antarctica in the South, Arctic circle in the North, Amazon rain forests in Brazil or the Mount Everest in Nepal.

    • Word count: 865
  6. altering the enzyme concentration

    The second most important variable that must be kept constant throughout the experiment is the substrate concentration. If this variable is, again, not kept constant I will have irregular results and the experiment will be unfair. I must keep the substrate concentration constant because the more substrate I add the faster the reaction as there will be more active sites available for the starch to be broken up in...therefore to keep my experiment fair and reliable I will use the same substrate concentration in every experiment.

    • Word count: 2097
  7. Diluting an Enzyme

    As well as temperature, enzymes are also sensitive to pH; they will start to denature if the conditions are too acidic or alkaline. Enzymes are adapted for their conditions; their optimum temperature is 40o and this is the temperature of the body. Because, for example, pepsin is found in the stomach, it works best under acidic conditions, and amylase, which is found in saliva in the mouth, works best under neutral/alkaline conditions. The actual optimum pH of amylase is 7.5.

    • Word count: 3636
  8. INVESTIGATING HOW ENZYME CONCENTRATION CAN

    the reaction time will be less). Expected results- The affect of concentration on enzyme activity will increase. However after a maximum point all the enzyme active sites will be filled and so the substrate will be the limiting factor Rate 1/t x 100 Concentration of enzyme The more enzymes present the lower the activation energy needed for the chemical reaction to start. This is because the enzyme might weaken a covalent bond with a substrate reaction or the enzyme might hold the substrate in a particular position that increases the likely hood that the molecules are going to react.

    • Word count: 3277
  9. ENZYME IMMOBILISATION

    I will immobilise the enzyme by trapping them in an alginate gel. Hypothesis-I predict that at the end of the experiment when I test the glucose strip, there should be a change in colour, and thus considerable amount of glucose should be present. In the experiment the enzyme lactase will be the independent variable as this will determine the amount of conversion of lactose to glucose and galactose. Thus the glucose and galactose production will be dependant on this. I will measure the production at the end using a glucose test strip against a colour scale to see how much is present.

    • Word count: 2777
  10. Biology coursework

    choose a method of attachment that will prevent loss of enzyme activity by not changing the chemical nature or reactive groups in the binding site of the enzyme. Enzyme-Invertase Invertase is a yeast-derived enzyme. Invertase splits sucrose into glucose and fructose. Wide ranges of microorganisms produce invertase and can utilize sucrose as a nutrient. Commercially, invertase is biosynthesized chiefly by yeast strains. Even within the same yeast culture, invertase exists in more than one form. In contrary to most other enzymes, invertase exhibits relatively high activity over a broad range of pH (3.5--5.5), with the optimum near pH=4.5.

    • Word count: 3980
  11. DESCRIBE THE MECHANISMS OF NEURAL COMMUNICATION, EXPLAINING HOW THEY ALLOW EFFECTIVE INFORMAION PROCESSING

    Action potentials leave via the axon and are connected to terminal (boutons/buttons), which are specialized in sending the information from cell to cell. Surrounding the neuron is the membrane, which is composed of protein and two layers of lipid (fat). The membrane potential is the electrical charge across the membrane and when cells are not firing in addition to having a 70mV difference between the inside and outside of the membrane, this is known as the resting potential. Electrically-charged particles are known as ions and like all cells; neurons maintain different concentrations of particular ions across their cell membranes.

    • Word count: 1369
  12. prove Boyles Law

    MOLECULAR EXPLANATION At room temperature and pressure, there are a certain number of gas molecules in 10cm3 of air. Each molecule exerts a pressure on the walls of a container. The molecules hitting the sides of the container cause this pressure. If you decrease the volume that the air occupies from 10 cm3 to 5 cm3, then there would be twice as many molecules per cm3 than before. This means twice as much pressure will be exerted due to twice as many molecules hitting the sides of the container at a certain time. ANALYSIS To analyse my results I will extend my table from before by adding 1/v and pv: p (x105 Pa)

    • Word count: 1313
  13. Reaction of Catalase and Hydrogen Peroxide

    Catalase is an enzyme present in the cells of plants, animals and aerobic (oxygen requiring) bacteria. It promotes the conversion of hydrogen peroxide, a powerful and potentially harmful oxidizing agent, to water and oxygen molecule. Catalase is composed of four subunits. Each subunit contains a heme group. This heme group is responsible for carrying out catalase's activity. Catalase functions to break down hydrogen peroxide (H2O2) into water and oxygen: 2H2O2 ? 2H2O + O2 This reaction is performed by oxidation, the loss of electrons, and reduction, which is the gain of electrons.

    • Word count: 6217
  14. Investigate the effect of the concentration of catalase on the rate of decomposition of hydrogen peroxide

    When the enzymes denature, the weak bonds that hold the tertiary structure of the enzyme together vibrate at an excessive rate, due to the kinetic energy, that they break as well as altering the shape of the active site to a degree that the substrate can no longer link to it. PH: The formation of the enzyme-substrate complex relies on an exact complementary shape and charge. If there is a change in pH, it will corrupt the charges so that no enzyme-substrate complex can be formed.

    • Word count: 2606
  15. An Experiment that will determine the effect Of Temperature up Rate of Reaction of Catalase And Hydrogen Peroxide.

    Method: Apparatus: * Bung- will be used to prevent oxygen from escaping. It's reliable because it fits to the test tube with ease and also ensures oxygen is no lost after in use. * Measuring cylinder- will be used to collect the enzyme substrate complex; its measurements are exceptionally accurate. * Delivery Tube-this is used to supply the product to the measuring cylinder. It's a reliable peace of apparatus because it does not let anything escape and its bendable which is very convenient in this experiment * Knife-used to cut potato into disc.

    • Word count: 2770
  16. PSYCHOLOGY EVALUATION

    contained different active ingredients with different active rates within the concentration affecting the overall activity of both enzymes making the comparison harder to see with each other. The overall experiment could of been more and reliable accurate if further tests were done, like mentioned in the conclusion, there was a limiting amount of pH buffer solutions used. There was not equal amounts of basic pH compared to acidic pH so the graphs would prove that it is ambiguous as it is impossible to tell the optimum pH for either of the amylases.

    • Word count: 534
  17. To investigate the effect of cell sizes on diffusion by modelling the process of agar blocks and dilute Hydrochloric acid.

    Gather apparatus. 2. Cut agar blocks into cubes of 1cm3, 2cm3 and 3cm3 on a white tile. The same shape blocks (cubes) must be used so that it is a fair test. Accurately measuring and cutting them with the metric ruler and knife. The same source of agar must be used in order to be a fair test. 3. Next fill three beakers with 50 ml of hydrochloric acid. The volume of hydrochloric acid cubes are immersed in must remain the same in order to keep it a fair test. 4. Place the 3 different size pink agar blocks into the beakers and start three separate stop clocks immediately.

    • Word count: 1182
  18. This is an investigation to determine the effect of concentration on the activity of an enzyme Trypsin on the insoluble protein found in milk known as Casein.

    Increasing the temperature causes more heat energy, which makes the substrate molecules and enzymes move a lot faster. This increases the kinetic energy; therefore more collisions take place between the substrate and the active site, resulting in more enzyme substrate complexes and formation of more products. If the temperature is increased even further; above 40�C, the substrate molecules and enzymes will vibrate so energetically that the hydrogen bonds holding the tertiary structure will break. The enzyme will lose its globular shape, which will affect the active site. The substrate will no longer fit into the enzyme's active site and the enzyme is said to be denatured.

    • Word count: 2294
  19. for this experiment my main aim is to investigate the effect of temperature on enzyme activity

    The molecules that bind with the active site of an enzyme are called Substrate. The combination of an enzyme and a substrate is called an enzyme-substrate complex. The shape of the active site on an enzyme allows a particular type of substrate to fit perfectly into it. Catalase-hydrogen peroxide complex Enzymes catalyses a reaction either by breaking down bonds or by forming bonds. After the reaction the products leave the active site for another substrate to bind with. NB: Enzymes are specific in action as only one type of substrate can fit into their active sites.

    • Word count: 6230
  20. Enzymes are affected a great deal by temperature.

    Protease Proteins small soluble amino acids Amylase Carbohydrates small soluble sugar Lipase Fats small soluble fatty acids and glycerol. Pg 1 Prediction: I predict the hotter the solution of the starch and amylase is, the reaction will become faster. But if the solution is at room temperature or below then it will take longer to react. I think this because the hot water will break down the enzymes faster so the hot water will make the enzymes move faster which is kinetic energy. I feel that there will be a successful collision because if I do the experiment clearly then the enzymes will bump into the right place. As the temperature increase the movement of the amylase moves faster.

    • Word count: 2120
  21. Enzymes uses in industry and medicine bio cw

    Enzymes can also work at many different ranges of pH as well as temperature changes and this is due to when they are immobilized in the industrial and medicine process. (3) This essay will now look at particular enzymes in industry and medicine within their main uses. An enzyme that is very important in the textile industry it is Amyloglucosidase, also known as glucoamylase. In the textile industry amylases are used to remove starch-based size for improved and uniform wet processing.

    • Word count: 1118
  22. Investigating the effect of temperature on the permeability of cell surface membranes

    Large polar molecules on the other hand, can not diffuse through the bilayer (i.e. glucose and amino acids). These molecules must diffuse through the hydrophilic channels created by the proteins in the bilayer. Each protein channel will only let a specific molecule through, this is essential for controlling what goes in and out of the cell. As you can see from the picture above, the membrane is quite complex. This is called a fluid mosaic model, this shows all the components known of a membrane.

    • Word count: 2367
  23. How enzyme concentration affects the rate of reaction

    To understand the significance of enzymes in an enzyme-catalyzed reaction some information about how they work must be known. Enzymes are protein molecules which are made up of amino acids. They have a three- dimensional shape because of the way the amino acids are arranged o the protein. A few of these amino acids on the surface of the molecule fold inwards making what is called the active site. Within the enzyme the active site is where the reactant molecule (in this case the egg white) attaches to the enzyme by random collision. The substrate binds to the active site of the enzyme where the reaction takes place.

    • Word count: 2516
  24. The Uses of Enzymes in Industry

    Enzymes have many applications in modern food processing. Enzymes are rapidly becoming very important to the Baking Industry. Enzyme supplements are used in baking to make consistently high-quality products by enabling better dough handling, providing anti-staling properties, and allowing control over crumb texture and colour, taste, moisture, and volume. The enzyme rennin is used to clot milk in cheese-making, and enzymes from yeast have long been used in the brewing and the baking industries. One specific use of enzymes in the food industry is its application in baby food-here the enzyme trypsin is used to pre-digest the baby food enabling easier digestion for the babies.

    • Word count: 1149
  25. Rennin investigationMy experiment is also to see how long it takes for milk and rennin to react with each other.

    Put the test tubes in to the beaker full of 150ml water. Check that the water has cooled down to what ever temperature you want it to be. 4. Measure the temperature if the milk and rennin, which should be between 38�C-42 �C. 5. Mix the rennin and with the milk and begin to time the reaction. 6. Note down when the reaction begins and also when the rennin and milk stop reacting with each other. The experiment: You keep the same amount of rennin (1cm�)

    • Word count: 1200

Marked by a teacher

This document has been marked by one of our great teachers. You can read the full teachers notes when you download the document.

Peer reviewed

This document has been reviewed by one of our specialist student essay reviewing squad. Read the full review on the document page.

Peer reviewed

This document has been reviewed by one of our specialist student document reviewing squad. Read the full review under the document preview on this page.