• 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+ (277)
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. ## AN INVESTIGATION INTO HOW TEMPERATURE AFFECTS THE PERMEABILITY MEMBRANE OF A BEETROOT.

3 star(s)

* My results are the first set of results * The anomalous results are in bold italics. ANALYSIS, EVIDENCE AND CONCLUSION Mean of class calculated to give more reliable data for conclusion and to use it to produce graph and standard deviation. Looking at the result table and the graph produced from the results obtained form this experiment; it shows that as temperature increases, the percentage transmission decreases. This tells us that temperature does affect the membrane, resulting in more leakage of the red pigment.

• Word count: 3800
2. ## Beetroot membrane

3 star(s)

Variables: Independent variable - the temperature of the water in the water bath. Dependent variable - colour change in the water. The increase or decrease of water temperature would have an effect on colour change in the water. Variables which were kept constant were the diameter of the beetroot piece. Risk assessment: * Taking care when using the cork borer and knife when dividing the beetroot sections. * Boiling tubes should be handled with care, especially in the water baths. Apparatus: * One beetroot * One size 4 cork borer * White tile * Knife * Ruler * Water Baths at 0 oC, 30 oC, 40 oC, 50 oC, 60 oC, 70 oC

• Word count: 1070
3. ## effect of temperature on beetroot pigment through membrane

3 star(s)

There will also be the same number of disks per boiling tube, 3 disks, to increase the surface area. Origin of Beetroot: The beetroot have to be of the same sort and source in order to make it a fair test. Ideally, I would use one, organic beetroot for all of the experiments. Organic beetroot tend to be juicier and richer in colour, however they are expensive. Therefore, I will be using beetroot from the local grocers, knowing that the beetroot have been grown in the same conditions and are the same species. Clean Glassware: This is essential for when placing test tubes into the colorimeter as a stain on the test tube can read a false reading, making my results unreliable.

• Word count: 3426
4. ## Cell Biology and Genetics

3 star(s)

In other words allowing what would be very long DNA molecules to fit into the cell's nucleous tiny space. These chromosomes provide a very important function for the cell. They carry the strands of DNA and proteins for the cells functionality. DNA's function to the cell is that it carries the code for the proteins controlling which proteins are made therefore controlling the cells activity. Ribosome's are very small organelles found in the cytoplasm and on the endoplasmic reticulum. They are structured into two parts, a large and small subunit which fit together and work as one. Their job is to synthesise proteins needed for the cell to function.

• Word count: 3398
5. ## Compare and contrast the structures/ultrastructures of cells

3 star(s)

In contrast to this, the similarities become evident only when the cells are looked at more closely. For example both plant and animal cells contain organelles, each one being assigned to a particular job. This is called 'division of labour'. This type of cell, where the nucleus is inside a nuclear envelope, and has other membrane-bound organelles, is called a eukaryotic cell.1There are new differences that can be discovered from using a more powerful microscope.

• Word count: 549
6. ## An investigation to see how different sugars affect the growth and respiration of yeast.

3 star(s)

Prediction I predict that glucose will allow yeast to produce the most respiration. This is because it is a monosaccharide Fair Test Whilst doing the experiments, it is necessary to have minimal errors. By this, each experiment must be done fairly. To make each experiment fair it is important to make sure: * The same quantities are used throughout all the experiments. * Separate syringes are used for the methylene blue, sugars and yeast; this is to avoid any contaminations. * Repeat each experiment to gain an average set of results. * The same equipment must be used * The time be used in the same units throughout the experiments Safety It is important to ensure: * All equipment is used safely and correctly.

• Word count: 2677
7. ## Enzymes - investigate how the substrate concentration (H2O2) affects the activity of catalase on hydrogen peroxide.

3 star(s)

This theory of how enzymes work Is known as the lock and key theory. A substrate Lock and key theory (Biology 1, 2002) molecule is a 'key', and binds to the active site of an enzyme, a 'lock'. The induced fit theory is another theory of how enzymes work. The active site of an enzyme is a cavity of a particular shape, and initially the active site is not the correct shape in which to fit the substrate. As the substrate approaches the active site changes and this results in it being a perfect fit.

• Word count: 6008
8. ## How does the pH affect the activity of amylase

3 star(s)

The buffer solution must also be kept at the same volume as the starch and amylase, but obviously the pH would be different. Apparatus 0.5% starch Solution - this is used for the experiment as it is the substrate that the enzyme will be breaking down 0.1% Amylase solution - we need the amylase, as this is the enzyme that is used in the experiment to breakdown the starch Water Bath at 37�C - this is used to keep the temperature constant throughout the experiment, at times the room temp can be different.

• Word count: 3845
9. ## Liver and Hydrogen Peroxide experiment

3 star(s)

Here are 2 graphs to show the increase of rate of reaction as enzyme and substrate concentration increase. For the purpose of this experiment the enzyme concentration will be kept constant and the variable will be the substrate concentration. Apparatus: 1dm3 10% Hydrogen peroxide - This is my substrate which I will make 6 different concentrations from. Liver (Catalase) - This is my enzyme that will be used to break down the H2O2 5x Test tubes with bungs and delivery tubes - Will be where the liver and hydrogen peroxide will react. Gas syringe - Where the gas will be collected to measure the rate of reaction.

• Word count: 1625
10. ## Enzyme concentration and enzyme activity. Trypsin

3 star(s)

Enzyme concentration: As the enzyme concentration increases the rate of the reaction increases linearly, because there are more active sites and so the reaction can proceed at a faster rate. Eventually, increasing the enzyme concentration beyond a certain point has no effect because the substrate concentration becomes the limiting factor. Hypothesis: As the enzyme-protease's concentration increases, the time taken for the breakdown of protein will decrease, meaning the rate will increase. The site of the reaction occurs in an area on the surface of the enzyme protease called the active site.

• Word count: 1079
11. ## biology differences in animal and plant cells

3 star(s)

(Toole, G & S 1984) the nucleus controls every organelle with the Cytoplasm. Within the nucleus is the Nucleolus, It is a small structure within the nucleus that forms ribosomes which then pass into the cytoplasm to produce protein (Moth.E 2003) The cell membranes is a fine membrane made of protein and lipids, it has two functions to keep the cytoplasm and the nucleus in. Plant and animal cells contain mitochondria, they are distinct organelles with two membranes, usually they are rod shaped, however they can be round, the outer membrane limit's the organelle, the inner membrane in thrown into folds or shelves that project inward, the organelles contain enzymes which convert food material into ATP (Adenosine Triphosphate)

• Word count: 1185
12. ## Biology Coursework Investigation

3 star(s)

I found this out through the preliminary work. As the pH of an enzyme increases (becomes less acidic) the enzyme activity increases until there is an optimum pH. As pH increases further (becomes more alkaline) the activity decreases. At very low pH and very high pH, the enzyme is denatured and does not work. - The type of enzyme (input variable)- The type of enzyme you use is also very significant to your results. This is due to the fact that different types of enzymes have different optimum temperatures and therefore are denatured at different temperatures.

• Word count: 2640
13. ## An investigation to determine how increasing the concentration of inhibitor Copper Sulpahte will affect the amount of juice pr

3 star(s)

This prevents enzyme substrate complexes formation, which means the enzyme can no longer function as it should. Therefore if i increase the concentration of the inhibitor it is more likely that the inhibitor will attach to an enzyme structure, meaning that a smaller ammount of enzymes are hydrolysing the same amount of pectin molecules, making less juice each time. Once the non-competitive inhibitor binds to the enzyme, it changes the shape of the active site, making the substrate unable to fit in its active site and therefore working properly. Enzymes: An enzyme is a protein that catalyzes or speeds up, a chemical reaction.They are biological catalysts.

• Word count: 825
14. ## Effect of different temperatures on the permeability of beetroot cell membrane.

3 star(s)

therefore there is a positive significant correlation between the two values. Group 2 Site Temp (�C) Rank R1 Absorbance (Arbitrary units) Rank R2 D (R1-R2) D2 1 25 1 0.26 2 -1 1 2 35 2 0.34 3 -1 1 3 45 3 0.21 1 2 4 4 55 4 0.63 4 0 0 5 65 5 2 6 -1 1 6 75 6 2 6 0 0 7 85 7 2 6 1 1 0 8 From using the formula the rs was 0.85, which is over the critical value (0.79)

• Word count: 2077
15. ## Proteins have many functions in the human body and these include transport, catalysis, protection, storage, sensitivity, structure and co-ordination.

3 star(s)

So this makes protein very crucial for your health. Each protein is a large complex molecule; these molecules are made up of a string of amino acids. There are 20 different amino acids that occur naturally to form proteins and they all have the same basic structure. The 20 amino acids the body needs can be linked in thousands of different ways to form thousands of different proteins, each with a unique function in the body. Both the amino acids manufactured in the liver and those derived from the breakdown of the proteins we eat are absorbed into the blood stream and taken up by the cells and tissues to build new proteins as needed.

• Word count: 1112
16. ## The Advantages & Disadvantages of Using Enzymes in Medicine and Industry

3 star(s)

Non - competitive inhibitors change the globular shape of an enzyme so that a enzyme-substrate complexes can't form meaning a lower optimum rate of reaction. Enzymes in Medicine Enzymes can have good and bad effects to the body; it depends on the situation that they are being used in. For example some bacteria is a lot more dangerous than others because of certain enzymes that they contain, meaning that they can do things such as (depending on the enzyme) duplicate faster, inhibit other enzymes and break down substrate's that should not be broken down etc, in general cause more damage to its holder.

• Word count: 895
17. ## The effect of temperature on catalase activity

3 star(s)

For this reason few cells can tolerate temperatures higher than approximately 45�C. Enzymes are specific in the reactions they catalyse, much more so than inorganic Catalysts. Normally, a given enzyme will Catalyse only one reaction, or type of reaction. The enzyme has an active site that helps it to recognise its substrate in a very specific way. Just like a key only fits into a specific lock, each enzyme has its own specific lock; each enzyme has its own specific substrate. This is called the lock and key theory. The enzymes never actually get consumed in the process; they just increase the rate of reactions.

• Word count: 2724
18. ## The use of pectinase in fruit juice production

3 star(s)

The pectin is broken down by enzymes in the pectinase group, which include polygalacturonases, pectin methyl esterase and pectin lyases. All three contribute to the breakdown of pectins from a variety of plant materials. Pectinase enzymes are produced during the ripening of some fruits and are also secreted by plant pathogens such as the fungus: Monilinia fructigena and the bacteria: Erwinia carotovora or the fungi: Aspergillus niger. The pectinase enzymes act in different ways on the pectins, for example they help soften their cell walls (they break down the cell walls).

• Word count: 688
19. ## An investigation to examine the effects of temperature on membrane stability in beetroot, by assessing the degree of pigment leakage.

3 star(s)

The bilayer is impermeable to ions and large polar molecules due to the hydrophobic regions within the phospholipids bilayer. However, specialised proteins within the bilayer, allow movement of these substances. It is selectively permeable and controls what enters and exits the cell. It does this by the proteins that are in it, however small lipid molecules, non-polar molecules and small water molecules can enter and exit the cell straight across the membrane through the phospholipids. This is due to the properties and size of the molecules, which enable them to do so.

• Word count: 9415
20. ## Should stem cell research be allowed?

3 star(s)

This means stem cells could repair diseased or damaged organs. So for example if part of a mouse's spine was removed stem cells could be put in its place and under the right conditions form the missing part of the spine. The stem cells would become spine cells. Stem cells can be extracted from adults and umbilical cords after a child is born, but are usually taken from embryos or tissue from aborted pregnancies (before the first trimester). Embryonic stem cells are of corse taken from human embryos.

• Word count: 1110
21. ## Investigating the Effect of Ethanol Concentration on the Rate of Respiration in Yeast.

3 star(s)

If the yeast is heated to a temperature above 45'C, then the enzymes within the yeast are denatured. Denaturating is when the bonds holding the protein in shape are broken, and the effects it has on the enzyme are irreversible. The optimum temperature at which the yeast will work best at is approximately between 25'C and 35'C, and anything below or above this then the reaction will not occur, or the results will be in accurate. As the temperature of the reacting mixture reaches around 30'C, this is the optimum temperature, so as the temperature increases or decreases around this the molecules have more energy to move around hence more collisions.

• Word count: 3629
22. ## Investigation into how temperature affects the enzyme: Amylase.

3 star(s)

The second variable is PH. Each enzyme has an optimum PH, any change in temperature will affect the bonding in an enzyme & therefore, will change it's shape. In my experiment, I will not change the PH of any of my enzymes by adding or taking away substances. I know from my preliminary work that my saliva is at PH 7 and that if the PH of the starch is changed from PH 7, then the reaction will be a lot slower.

• Word count: 1887
23. ## The effect of enzyme concentration on enzyme activity.

3 star(s)

A depression on the three dimentional shaped surface of the molecule is the active site. This takes up only a fractional of the enzyme molecule so only a few of the amino acids will be directly involved in the active sites. Substrate molecules are either single or more complementary molecules that fit into the active sites. These form tempary bonds with the amino acids forming an enzyme - substrate complex. During each separate reaction products are formed which are released and enzyme concentration remains the same. The enzyme works only for a specific reation due to its uniquely shaped active site.

• Word count: 1390
24. ## Investigate the Effect of Temperature Change on the Permeability of Beetroot Cell Membrane.

3 star(s)

The asterix (*) indicates anomalous results. To give me a visual perception of my obtained results compared to that of the two other groups, I will represent the results in a form of a scatter diagram/graph. I will use the Spearman Rank Statistical test to carry out a statistical analysis of my results. This will allow me to establish a significant relationship between the two sets of data, which are the temperature and the absorbency. Data Set 1 Temp. Rank R1 Data Set 2 absorbance Rank R2 Difference (R1 - R2)

• Word count: 1236
25. ## Investigation of factors affecting the enzyme Amylase.

3 star(s)

Therefore I have developed two similar experiments (one for each factor I am investigating). To investigate the pH effects on the enzyme amylase activity. 1. Pour amylase solution into a test tube to a depth of 2cm. 2. Half fill another test tube with a 4% starch solution. 3. With a pipette, place a drop of iodine into each dimple in a dimple tray. 4. With a glass rod lift a drop of the starch solution from the first test tube and mix it with the first drop of iodine in the first dimple in the tray. A blue/black colour should develop; this will be used as the control. 5. Rinse the glass rod.

• Word count: 2074