Biology paper 1

• All living things are made of cells
• Cells can be either eukaryotic or prokaryotic. Eukaryotic cells are complex and include all animal and plant cells. Prokaryotic cells are smaller and simpler, e.g. bacteria
• Eukaryotes are organisms that are made up of eukaryotic cells
• A prokaryote is a prokaryotic cell (it’s a single-called organism)
• the Different parts of a cell are called subcellular structures
• Most animal cells have the following subcellular structures which are a nucleus, cytoplasm, cell membrane, mitochondria and ribsomes
• Plant cells usually have all the bits that animal cells have, plus a few extra things that animal cells dont which is a rigid cell wall, large vacuole and chloroplasts
• Bacterial cells have no nucleus
• Bacterial cells have chromosomal DNA, ribosomes, cell membrane, plasmid DNA and flagellum
• Multicellular organisms contain lots of different types of cells and cells that have a structure which makes them adapted to their function are called specialised cells
• I’m sexual reproduction, the nucleus of an egg cell fuses with the nucleus of a sperm cell to create a fertilised egg, which then develops into an embryo. Both the nucleus of an egg cell and of a sperm cell only contain half the number of chromosomes that’s in a normal body cell so they are called haploid
• An egg cell contains nutrients in the cytoplasm to feed the embryo and has a haploid nucleus. Straight after fertilisation, it’s membrane changes structure to stop any more sperm getting in. This makes sure the offspring end up with the right amount of DNA
• A sperm cell has a long tail so it can swim to the egg and it has lots of mitochondria in the middle section to provide the energy (from respiration) needed to swim this distance. it also has an acrosome at the front of the head where it stores enzymes needed to digest it’s way through the membrane if the cell and also contains a haploid nucleus
• Epithelial cells line the surface of organs. Some of them have cilia on the top surface of the cell. The function of these ciliated epithelial cells is to move substances —- the cilia beat to move substances in one direction, along the surface of the tissue. For example, the lining of the airways contains lots of ciliated epithelial cells. these help to move mucus up to the throat so it can be swallowed and doesn’t reach the lungs
• Microscopes uses lenses to magnify images. they also increase resolution of an image. Resolution means how well a microscope distinguishes between two points that are close together. A higher resolution means that the image can be seen more clearly
• Light microscopes were invented in the 1590s. They work by passing light through the specimen. They let us see things like nuclei and chloroplast and we can also use them to study living cells
• Electron microscopes were invented in the 1930s. They use electrons rather than light. Electron microscopes have a higher magnification and resolution than light microscopes, so they let us see much smaller things in more detail like the internal structure of mitochondria and chloroplasts, giving us a much greater understanding of how cells work
• To view a specimen through a light microscope

  1. Take a thin slice of the specimen

  2. Take a clean slide and put a drop of water in the middle

  3. Use tweezers to place the specimen on the slide

  4. Add a drop of stain if the specimen is transparent

  5. Place a cover slip at one end of the specimen, holding it at an angle with a mounted needle

  6. Clip the slide onto the stage

  7. Select the lowest powered objective lens

  8. Use the coarse adjustment knob to move the stage up so the slide is just underneath the objective lens

  9. Look down until the specimen is in focus

  10. Adjust the focus with the fine adjustment knob until you get a clear image
• How to create a scientific drawing of a specimen 


  first using a sharp pencil. draw outlines of the main features using clear, unbroken lines. Don’t include any colouring or shading. next, make sure that your drawing takes up at least half of the space available and keep all the parts in proportion. And finally, label the important features of your diagram with straight lines which don’t cross over each other, and include the magnification used and a scale.
• Total magnification= eyepiece lens magnfication x objective lens magnfication
• Magnification= image size divided by real size
• Enzymes are biological catalysts produced by living things
• chemical reactions within living things need to be carefully controlled to get the right amount of substances.
• you can usually make a reaction happen more quickly by raising the temperature this would speed up the useful reactions but also the unwanted ones too
• Chemical reactions usually involve things either being split apart or joined together. The substrate is the molecule changed in the reaction. every enzyme has an active site. enzymes usually only work with one substrate as they are said to have a higher specificity for their substrate. This is because for the enzyme to work the substrate has to fit into the active site and if the shape doesn’t match the shape then the reaction won’t be catalyse. this is called the lock and key mechanism
• Temperature, pH and substrate cocentration affect the rate of reaction
• Like with any reaction, a higher temperature increases the rate at first, but if it gets too hot some of the bonds holding the enzyme together break, this changes the shape of the enzymes active site so the substrate won’t fit anymore and the enzyme is said to be denatured and all enzymes have the optimum temperature that they work best at
• The pH also affects enzymes if it is too high or too low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme or enzymes have an optimum pH that they work best at its often neutral pH 7, but not always. it works best at pH 2, which means it’s well suited to the acidic conditions there
• Substrate concentration increases


  Rate of reaction increases
• This relationship is only true up to a point
• Investigation to find the effect of pH on enzyme activity

  1. Put a drop of iodine solution into every well of a spotting tile place

  2. Set up Bunsen burner on a heatproof mat and a tripod and gauze over the Bunsen burner

  3. Put a beaker of water on top of the tripod and heat the water until it is 35°C

  4. Try to keep the temperature of the water constant throughout the experiment

  5. Use a syringe to add 3 cm³ of amylase solution and 1 cm³ of a buffer solution with a pH of 5 to a boiling tube

  6. Put the boiling tube into the beaker of water and wait for five minutes

  7. Use a different syringe to add 3 cm³ of starch solution to the boiling tube

  8. Immediately mix the contents of the boiling tube and start a stop clock

  9. Use continuous sampling to record how long it takes for amylase to break down all the starch

  10. Take a fresh sample from the boiling tube every 10 seconds and put a drop into a well when the iodine solution remains brownie. Orange starch is no longer present

  11. Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down

  12. Remember to control any variables each time to make it a fair test
• Iodine solution is used to detect the presence of starch
• Amylase is an enzyme that breaks down starch
• Buffer solutions are used to control the pH of the reaction
• As pH changes


  The time taken for amylase to break down starch changes
• Controlling variables is important to make the experiment a fair test
• You'll soon know how to investigate the effect of all on the rate of me activity I bet you're fred
• Investigating the effect of pH on enzyme activity


  1. Put a dep of iodine solution info every wall of a spotting

  2. Place Bunsen bums on a heat-pesold and a tripod and has the water until it is 2500

  3. Use to add 3 cm of anise solution and 1 on of a buffer solution with a pH of 5 to a boling tube

  4. Neod, use different surge to add 3 cm of a star solution to the boiling tube

  5. Immediately bestsets of the bolling tube and start stop look the condo to record balon H takes for the amylace to break down all of the starch

  6. Bat the whole experiment with buffer solutions of different pa to see how pH affects the time taken for the starch to be broken down

  7. Remember to gantfangarbleach time (eg. concentration and volume of anglece solution) to make it a fatt
• Iodine solution


  Will change from lengr to black when starch is present
• Rate of reaction


  A measure of how much something charges over time