GCSE Edexcel biology SB1 Newest Study Guide Version With Answers.

What is an electron microscope? (SB1a) - correct answer Microscopes that send beams of electrons through a specimen to build up an image. What is meant by an instrument's resolution? (SB1a) - correct answer The smallest distance between two visible points Why can some cell structures be seen with an electron microscope but not with a light microscope? (SB1a) - correct answer This is because electrons have a smaller wavelength than visible light and so can reveal tiny details in cells that a light microscope would not be able to How do you calculate the magnification of a microscope? (SB1a) - correct answer eyepiece lens x objective lens How do you calculate the size of an object? (SB1a) - correct answer Image size/magnification - make sure everything is in the same units Name all the parts of an animal cell (5) (SB1b) - correct answer Nucleus, cell membrane (the inside wall), cytoplasm, ribosomes, mitochondria Name all the parts of a plant cell (8) (SB1b) - correct answer Nucleus, cytoplasm, cell membrane (inside wall), cell wall (outside wall), mitochondria, ribosomes, chloroplasts, permanent vacuole What structures exist in plant cells but not animal cells (3) ? (SB1b) - correct answer Cell wall, chloroplast, vacuole What are the functions of the structures found in both animal and plant cells? (SB1b) - correct answer Nucleus - Controls the activities for the cell and contains DNA Cytoplasm - Place in the cell in which reactions occur, also holds organelles Cell membrane - controls what enters and leaves the cell Mitochondria - produces energy for the cell through aerobic respiration Ribosomes - site of protein synthesis What are the functions of the structures found in plant cells? (3) (SB1b) - correct answer Cell wall - supports the cell and prevents the cell from bursting when turgid Chloroplast - contains chlorophyll which traps light energy to perform photosynthesis Permanent vacuole - contains cell sap and stores water, also helps to keep the cell firm and rigid how do you estimate sizes using microscope fields of view? (SB1b) - correct answer Find the diameter of the field of view (should be a circle that shows cells or structures inside), then divide the diameter by however many of the desired structure would fit in that diameter. This will give you an estimate of the size of the desired structure. Watch this video - correct answer State why the lowest power magnification is used when first examining a specimen (SB1b) - correct answer To get the biggest field of view to be able to examine the most cells possible When observing onion cells, there may be large, thick circles that make it difficult to observe the cells, give a method to prevent this (SB1b) - correct answer Lower the objective lens more carefully and gently When observing onion cells, state why there may be large, thick circles that make it difficult to observe the cells (SB1b) - correct answer There may be air bubbles trapped between the lens and the specimen Describe how sperm cells are adapted to their function, give 5 examples(SB1c) - correct answer -Streamlined shape to allow it to swim -Lots of mitochondria to produce energy for swimming -Contains DNA in the head of the cell to be closest to the egg when fused -A small vacuole called acrosome that contains enzymes to break down to break down substances in the egg's jelly coat which allows the sperm cell to bury inside -A tail to allow it to move and swim Describe how egg cells are adapted to their function, give 3 examples (SB1c) - correct answer -After fertilisation, the cell membrane becomes hard to stop other sperm cells from entering -The cytoplasm is packed with nutrients to supply the fertilised egg with the energy and raw materials for the growth and development of the embryo -Has a jelly coating to protect the cell. Describe how ciliated epithelial cells are adapted to its function (SB1c) - correct answer -They have hair-like structures called cilia which contain strands of a substance that can contract to cause a wavy movement to move egg cells of waft mucus up the trachea containing pathogens to be swallowed into stomach acid or spat out. Identify the common parts of bacteria cells (9) (SB1d) - correct answer -Nucleus -Plasmids -Cell membrane - Flexible cell wall -Chromosomal DNA -Flagella -Ribosomes -Cytoplasm -Slime coat What kind of cells are bacteria? (SB1d) - correct answer Prokaryotic Explain the functions of the structures inside a bacteria cell (apart from nucleus, ribosomes, cell wall and membrane, and cytoplasm) (SB1d) - correct answer N.B. in Eukaryotic cells cell walls are made from cellulose but in Prokaryotic they are made from a compound called peptidoglycan. Plasmids - Small rings of DNA that code for extra genes to those provided from the chromosomal DNA Chromosomal DNA - Codes for genes and floats in the cytoplasm as prokaryotic cells have no nucleus Flagella - Tails to allow the cells to move Slime coat - for protection Why are bacteria cells described as being prokaryotic? (SB1d) - correct answer Because they have no membrane bound organelles and no nucleus. What does being membrane bound allow for? (SB1d) - correct answer It allows the organelles within a cell to control what enters and leaves the organelle through the use of a semi-permeable membrane What's the difference between prokaryotic and eukaryotic cells? (SB1d) - correct answer Eukaryotic cells contain a nucleus which holds the DNA of the cell and has membrane bound organelles whereas prokaryotic cells have no nucleus which means the chromosomal DNA floats around in the cytoplasm. Prokaryotic cells also have plasmids which are circular rings of DNA that add on to the main chromosomal DNA to code for extra genes as well as a slime coating instead of a cell wall for protection, however, they do have cell walls for support. Describe how to test for starch in food (SB1f) - correct answer Iodine test. Add iodine, the colour changes from yellow-orange to blue-black if starch is present. Describe how to test for reducing sugars in food (SB1f) - correct answer Benedict's test. Mix a food solution with equal parts Benedict's solution and heat in a water bath for 5 minutes. A green, orange or brick red precipitate forms if sugars are present. - red is strongest, green is weakest. Blue if no sugars Describe how to test for proteins in a sample. (SB1f) - correct answer Biuret test confirms presence of peptide bond 1. Add equal volume of sodium hydroxide to sample at room temperature. 2. Add drops of dilute copper (II) sulfate solution. Swirl to mix. (steps 1 & 2 make Biuret reagent). 3. Positive result: colour changes from blue to purple Negative result: solution remains blue. Describe how to test for lipids in a sample. - correct answer Dissolve solid samples in ethanol. Add an equal volume of water and shake. Positive result: milky white emulsion forms Explain how calorimetry can be used to measure the energy in food (SB1f) - correct answer Light the food sample on a mounted needle underneath some water. Find the change in temperature to measure the energy produced. We can then use an equation to work out the energy transferred = mass x specific heat capacity (4.2 J) x temperature rise - N.B. mass must be in Kg NOT g How can we work out the energy given out per gram? (SB1f) - correct answer Divide the energy given out by the mass of the fuel in grams. Evaluate the accuracy of calorimetry and how it can be fixed (SB1f) - correct answer In the most basic method, where the sample is heated underneath the boiling tube, it isnt very accurate becasue alot of the heat energy is dissipated into the surroundings and if not, it may be dissipated out of the boiling tube out the sides or out the top - this is due to there being no insulation To solve this we can place the food sample in a container with some wires running through it inside the water bath with a lid over it. We can then heat the metal wires to burn the food sample. We can also use a stirrer to ensure that the heat produced in distributed evenly throughout the water. What are enzymes? (SB1e) - correct answer biological catalysts - proteins that speed up reactions Give some examples of enzymes and where they are found (SB1e) - correct answer Amylase - saliva and small intestine Catalase - most cells but especially liver cells Starch synthase - plant DNA polymerase - nucleus What are protein molecules broken down into? (SB1e) - correct answer Amino acids which can be synthesised into a chain of acids to fold to form a protein What are starch molecules broken down into? (SB1e) - correct answer Starch molecules which can be synthesised into starch