40130591
Description
| Question | Answer |
| convert between units- volumes | cubic metre 10^9 m^3= 1 km^3 0.000001 m^3=1cm^3 10^-9m^3= 1mm^3 10^-18m^3= 1 um^3 Cubic decimetre 0.001 dm^3= 1cm^3 0.000001 dm^3= 1 umm^3 cm3 is the same as millilitre (ml) dm3 is the same as litre (l) |
| Convert between units- length | 1m= 1000 mm 1mm=1000um 1um= 1000 nm |
| units- time/ warning | cm not SI units- rarely use, L and ml= not SI units don't use Time- don't use combo of seconds and minutes- use minutes if no.= too big for human brain to comprehend |
| Units for rates | Rates of an enzyme controlled reaction: |
| Use of appropriate apparatus for quantitive measurment- 1.3- Determination of water potential measuring changes in mass/length | Ruler graduated in mm- cut 15 potato cylinders- same length/ 50 cm^3 measuring cylinder- measure water stopwatch- leave room for 45 min thermostat to keep at 4C- thermometer to check? |
| Use of appropriate apparatus for quantative measurment- Determination of solute potential by measuring the degree of incipient plasmolysis | Stopwatch- time 10cm^3/ 25 cm^3 measuring cylinder- if need to measure distilled water/ sodium chloride ruler graduated in mm- in case you need to cut out 0.5x0.5cm tissue square exactly x10 then x40 objective lens- to count no. turgid and plasmolysis cells |
| Use of appropriate apparatus for quantitative measurements- Investigation into the permeability of cell membranes using beetroot | Thermometer- ensure water baths are at right temperature Stop Watch- water in tubes given time to equilibrate before beetroot is added/ beetroots in tubes for 30 mins Colorimeter with blue filter/ colour chart- measure absorbance/ % transmission of solutions |
| Apparatus- quantitative measurements- Investigation into the effect of substrate concentration on enzyme activity | Measuring cylinder- 10cm^3/ 25 cm^3- measure 5cm^3 distilled water and 10cm^3 Hydrogen peroxide (H2O2) Stopwatch- time that potato paper discs take from striking the surface to sink to float up to the surface again ruler- graduated in mm- 2cm piece of potato cylinder |
| Apparatus- quantitative measurements- Investigation into the effect of temperature or ph on enzyme activity | 2x10cm^3 syringes/ measuring cylinders- 5cm^3 milk/ 7cm^3 sodium carbonate solution measured 2cm^3 syringe-add 1cm^3 lipase from beaker to test tube in water bath Thermometer- check temp of test tube in water bath Stop clock- see how long it takes for solution to lose its pink colour/ test tube needs time to equilibrate in water bath |
| Apparatus- quantitative measurements- Investigation into transpiration using a simple potometer | Stop clock- length air bubble travels in set time Potometer- use scale on potometer/ internal diameter of capillary tube to find cm^3 of water lost per minute- most of the water drawn up by the plant is lost via transpiration, making it a valid proxy. In mm^3=pier^2h pie=3.14, r= radius, h= distance moved by air bubble Graph paper- draw around edge of leaves- calculate total surface area of leaves- to find volume of water lost per cm^2 per minute |
| Apparatus- quantitative measurements- Investigation of dehydrogenase activity | 10cm^3 syringe- 10cm^3 yeast suspension measure 1cm^3 syringe- 1cm^3 indicator |
| Apparatus- quantitative measurements- Investigation into affect of light of photosynthesis | Colorimeter- absorbance of solution Measuring syringe w/out needle- for solutions under 10cm^3/ cylinder for measuring 200cm^3 Metre ruler- place vials a distance from the light source Timer- leave algal balls to form for 20mins/ give time for vials to be in light |
| Apparatus- quantitative measurements- Investigation into factors affecting respiration in yeast | Thermometer-. Mix hot and cold water in the trough to attain the chosen temperature. 1dm3 beaker for carrying water 20cm3 syringe- Stir the yeast suspension and draw 5cm3 into the 20cm3 syringe/ draw additional 10cm3 sucrose solution. Timer- Allow 2 minutes for the yeast and sucrose to equilibrate to temperature/ when gas bubbles emerge regularly from the nozzle of the syringe, count the number released in one minute. |
| Investigation into numbers of bacteria in milk serial dllution steps | Sterilise all apparatus in a pressure cooker for 15 to 20 minutes prior to the experiment. During the experiment, place all disposable items into a container labelled ‘waste’. Once used, return all apparatus to the pressure cooker to be sterilised. Carry out the following procedure for both samples of fermented milk: Serial dilution 1. Start with the solution of fermented milk. Use a graduated pipette to transfer 0.1 cm3 of the milk into a screw-cap bottle along with 9.9 cm3 of distilled water. Label this 10-2 2. Next, use a graduated pipette to transfer 0.1 cm3 of the 10-2 solution into a screw-cap bottle along with 9.9 cm3 of distilled water. Label this 10-4 3. Repeat until a 10-10 solution is produced: 4. Swirl each screw-cap bottle to gently mix |
| Investigation into numbers of bacteria in milk serial- counting bacteria | 1. Remove the Petri dishes from the incubator. Observe the plates and select the dilution that produces the most distinct colonies. 2. Count the number of bacterial colonies present on the selected plate. Use a marker to highlight each colony counted on the Petri dish to prevent re-counting. 3. Estimate the bacterial count of the initial fermented milk sample. Each bacterial colony arises from a single cell, enabling the estimation of the number of cells in the initial culture. e.g. 56 colonies counted on the 10-6 dilution Petri dish ∴ 56 × 106 = 5.6 × 107 bacteria per cm3 fermented milk. To increase the reliability of the results, the experiment can be repeated a further two times for the dilution that produced the most distinct colonies. This gives three bacterial colony counts, enabling the calculation of a mean. |
| Aseptic techniques p1 | Handwashing is a simple yet effective technique that should always be practised before handling microbes. Sterilisation of equipment is another aspect of aseptic techniques. It’s crucial to ensure that glassware, tools, and any surfaces where handling will take place are thoroughly sterilised. This can be done through heat (flaming), pressure (autoclaving), or chemical solutions (ethanol). Wear gloves whenever needed and dispose of them appropriately after use. Inoculating loops (tools for transferring bacteria) need to be sterilised by heating in a flame before and after each use. This prevents any bacteria from being transferred in or out. |
| Aseptic techniques p2 | Culture plates in which microbes grow should always remain closed unless absolutely necessary. When opened, the lid should not be put down on the work surface and should be held diagonally over the plate to minimise the exposure to the air. Incubating cultures should not exceed 25 degrees Celcius. This is to avoid the growth of harmful bacteria that thrive at body temperature (37 degrees Celcius). Remember to clean the workstation before and after use. This typically involves wiping down the area with a disinfectant. |
| Calibration of a light microscope eye piece graticule | Inside the eyepiece of the microscope there is an eye piece graticule. It is graduated 1-10 with 10 subdivisions between each number therefore the eyepiece graticule has 100 eyepiece units (epu) along its length- different magnifications, the divisions on the eyepiece graticule will cover different actual lengths of the specimen on the slide |
| Calibration- stage micrometer | . There are two types of stage micrometer available, check which you are using. Either The stage micrometer is a slide with a line 1 mm long on it. The line is also marked for tenths and hundredths of a mm. There are 100 stage micrometer units [smu] on the 1 mm line. Each stage micrometer unit = 0.01 mm or 10 µm. Or The stage micrometer is a slide with a line 10 mm long on it. The line is also marked for tenths and hundredths of a mm. There are 100 stage micrometer units [smu] on the 10 mm line. Each stage micrometer unit = 0.1 mm or 100 µm . |
| Calibration calculation | Line up the zero of the eyepiece graticule and the zero of the stage micrometer. • Make sure the scales are parallel. • Look at the scales and see where they are in line again (look in book) Using this x40 objective lens, 20 stage micrometer units make up 80 eyepiece units. 80 eyepiece units = 20 stage micrometer units If 1 stage micrometer unit = 0.01mm 1 eye piece unit = 20 80 = 0.25 stage micrometer units 1 stage micrometer unit = 0.01mm 1 eye piece unit = 0.25 x 0.01 mm = 0.0025 mm or 0.0025 x 1000µm = 2.5 µm If 1 stage micrometer unit = 0.1mm 1 eye piece unit = 20 80 = 0.25 stage micrometer units 1 stage micrometer unit = 0.1mm 1 eye piece unit = 0.25 x 0.1 mm = 0.025 mm or 0.025 x 1000µm = 25 µm |
| Microscope use- Low power plan of anther, including calculation of actual size and magnification of drawing | Need a microscope and slide of T.S. anther Observe slide using x10 objective lens Draw plan to show distribution of tissues in correct proportion- may need to use x40 to see some of the tissue layers |
| How to draw a low power plan/ calculate actual size | ● Drawing should fill at least half of the provided space ● Only draw what you can see ● Use a sharp pencil ● Ensure lines are single, complete and non-overlapping ● Do not use shading or colour ● Create straight lines for labels using a ruler ● Label lines should not have arrow heads ● Label lines should not intersect ● Include a scale in terms of eyepiece units ● Include a title and objective lens power ● Include a magnification No individual cells should be drawn. There should be no mysterious gaps between tissues. |
| Calculating actual size from microscopes | Step 1: Calculate the total magnification of the specimen total magnification = eyepiece lens magnification × objective lens magnification 10 × 40 = 400 Magnification = ×400 Step 2: Convert the image size into μm 1 mm = 1000 μm 3 × 1000 = 3000 Image size = 3000 μm Step 3: Substitute values into equation for actual size Actual size = image size ÷ magnification Actual size = 3000 ÷ 400= 7.5 Therefore, the average size of a red blood cell in this sample is 7.5 μm |
| : Scientific drawing of low power plan of a prepared slide of T.S. leaf- method | 1. Calibrate the microscope for all three objective lens magnifications (see ‘Calibration of a light microscope’ practical). 2. Place the microscope slide of the T.S. dicot leaf under the clips on the microscope stage. 3. Turn the lowest power objective lens (×4) on the nose piece. 4. Turn the coarse adjustment knob to move the stage closer to the lens. 5. Look down the microscope and turn the coarse adjustment knob to focus the image. 6. Turn the fine adjustment knob until the best image is obtained. 7. Rotate to the medium power objective lens (×10) and focus using the fine adjustment knob. |
| : Scientific drawing of low power plan of a prepared slide of T.S. leaf- method- p2 | 8. Draw a rough sketch of the outline of the leaf. 9. Select a region of the slide (that includes the central midrib) to draw a low power plan. Mark this region on the rough sketch. 10. Draw a low power plan to show the distribution of tissues but not individual cells. The high power objective lens (×40) can be used to aid in the identification of the different tissue layers. |
| : Scientific drawing of low power plan of a prepared slide of T.S. leaf- method- p2 | 11. Label the following structures: cuticle; upper epidermis; lower epidermis; palisade mesophyll layer; spongy mesophyll layer; xylem; phloem; collenchyma; sclerenchyma and guard cells. Collenchyma tissue consists of elongated cells with abnormally thickened cell walls. It is often found under the epidermis and in the veins. Sclerenchyma tissue is made up of cells with lignified walls. It is mainly found in the cortex and is often stained red. 12. Using the eyepiece graticule, draw two lines on the low power plan, measured in eyepiece units. 13. Calculate the actual size of the low power plan and hence the magnification of the drawing. |
| Scientific drawing of cells from prepared slides of anther- method | . Examine the slide using the x10 objective lens. 2. Draw a plan to show the distribution of tissues in the correct proportion. 3. You may need to use the x40 objective to identify some of the tissue layers. 4. The entire structure need not be drawn but if it is not a complete representation of the entire structure a small drawing should be made and the area drawn in the plan shown. 5. Draw two lines measured in eye piece units on the plan. 6. Label the following structures: epidermis; tapetum/ inner wall; fibrous layer/ outer wall; area of dehiscence/ stomium; pollen sac; xylem; phloem; parenchyma. 7. Calculate the actual size of the plan and the magnification of the drawing. |
| T.S Artery- low power plan | Method 1.Calibratethe microscope for all three objective lens magnification (see ‘Calibration of a light microscope’ practical). 2.Place the microscope slide of T.S. artery under the clips on the microscope stage. 3.Turn the lowest power objective lens(×4) on the nose piece. 4.Turn the coarse adjustment knob to move the stage closer to the lens. 5.Look down the microscope and turn the coarse adjustment knob to focus the image. 6.Turn the fine adjustment knob until the best image is obtained |
| T.S Artery- low power plan- p2 | 7) Using x10 objective lens Draw a plan to show the distribution of tissues in the correct proportion 8) may need to use x40 objective to identify some tissue layers Identify and label- endothelium, tunica intima/ interna, tunica media, tunica externa/ adventitia, lumen 9)Draw 2 lines measured in epu on the plan 10) Calculate the actual size of the tissues and magnification of drawing 11) Repeat steps using vein |
| High power plan drawing | A high-power diagram generally does show individual cells. For a high-power diagram of a microscope slide, CIE require that students are provided with a microscope with a x10 eyepiece lens and high-power objective lens (x40). For a high power diagram: draw only a few representative cells draw the cell wall of all plant cells (usually as a double line) do not draw the nucleus as a solid blob (this is a particularly common error). https://ifitsgreenormoves.com/tag/high-power-diagram/ |
| TS leaf structure functions | cuticle- waterproof and protects the leaf from water loss, alongside the upper epidermis. The lower epidermis and its respective waxy cuticle serve the same role… upper epidermis- Thin and transparent to allow light to enter palisade mesophyll layer underneath it lower epidermis palisade mesophyll layer- Column-shaped cells tightly packed with chloroplasts to absorb more light, maximising photosynthesis |
| TS leaf structure functions p2 | spongy mesophyll layer- Contains internal air spaces that increase the surface area to volume ratio for the diffusion of gases (mainly carbon dioxide) xylem- Transports water into the leaf for mesophyll cells to use in photosynthesis and for transpiration from stomata phloem- Transports sucrose and amino acids around the plant collenchyma-living support tissue with irregular walls- provide mechanical support to the growing young parts of the plants. It also provides flexibility, protects leaf margins from tearing sclerenchyma- Unlike collenchyma, mature cells of this tissue are generally dead and have thick walls containing lignin- support tissue composed of any of various kinds of hard woody cells. guard cells- Absorbs and loses water to open and close the stomata to allow carbon dioxide to diffuse in, oxygen to diffuse out |
| Anther- structure functions | Epidermis: It is the outermost part of the pollen sac that consists of a single layer. The function of the epidermis is to protect the pollen sacs. Inner Epidermis: It is also a single layer that develops the cellulose. The cellulose consists of the pectin and lignin fibrous. |
| Anther- structure/ function p2 | Middle Layer: It is a cell-like structure that is present just below the inner epidermis. The cell is protected with three to four layers and nourishes the microspore to produce pollen. Tapetum: It is the fourth layer that is close to the pollen sac. It provides the essential nutrients for the pollen division process. outer wall area of dehiscence-causes the release of pollen grains- Anther Dehiscence is the process of splitting of the anther. It is the final stage where the anther breaks and releases the pollen grains through different processes including pollen differentiation, stomium- site through which pollen grains are released pollen sac- contains pollen parenchyma- They are found in many parts of a plant and perform a variety of functions, including storage, transport, photosynthesis, growth, repair and support. |
| h | endothelium- Endothelial, cells, for example, can be responsible for “telling” arteries to contract or relax depending on the body’s needs. They also control the release water, electrolytes, and other substances into the blood. tunica intima tunica interna tunica media tunica externa tunica adventitia lumen |
| use qualitative reagents to identify biological molecules- Food tests Reagent- A chemical that indicates the presence of a substance, usually by changing colour- 6 | Food sample- Reducing sugar ,Reagent- Benedict’s ,Method -Add-Benedict’s reagent to the food and boil in a water bath ,Initial colour-Blue ,Colour change-Brick red precipitate Food sample- Starch, Reagent-Iodine Method-Add iodine reagent to the food. Initial colour-Yellow-brown, Colour change-Blue-black Food sample-Protein/amino acids Reagent-Biuret (a mixture of sodium hydroxide and copper sulfate). Method- Add Biuret reagent to the food. Initial colour-Blue, Colour change-Lilac/purple Food sample-Fat Reagent-Ethanol Method-Add ethanol to the food to dissolve the fat then add water. Initial colour-Colourless Colour change-White emulsion |
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