Paper 1 Biology Required Practicals Flashcards
(17 cards)
microscope practical
-add a drop of water to a microscope slide
-take a thin piece of onion skin ( to allow light to pass through)
-stain the microscope slide using iodine ( so we can see the structures inside the cell)
-gently lower a cover slip on your stained tissue to cover it before you put it on microscope
-use clips to hold the slide in place on stage
-rotate lens to the lowest power first
-use objective lens to magnify the image
-use coarse focussing knob to focus the image first so it is not blurry
- use the fine focus knob to make your image focused at high magnifications.
culturing microorganisms
-incubate at 25 degrees to prevent the growth of harmful pathogens
-place agar plate upside down so no condensation falls on bacteria
-loosely tape lid so bacteria have oxygen to grow
the cell cycle
interphase :
-replicate DNA
-cells grow in size
-increase number of sub-cellular structures
mitosis:
-chromosomes are pulled apart to opposite sides of the cell
-cell membrane and cytoplasm divide
-forming 2 genetically identical daughter cells with the same chromsome number
what is the IV, DV and CV of the enzyme effect on amylsase required practical?
independent variable : pH or temperature or substrate concentration
dependent variable : a colour change using indicator
-mass/volume of product produced
-change in pH
control variable : volume of solutions
-concentration of solutions
what is the role of arteries and their structure
arteries : transports blood away from the heart at high pressure
-narrow lumen to maintain high pressure
-thick elastic layer so they can stretch and recoil to maintain high pressure
-thick muscle layer to withstand high pressure
what is the role of veins and their structure
-transport blood to the heart at low pressure
-wider lumen to transport greater volume of blood
-thinner muscle + elastic walls as blood is at low pressure
-valves to prevent backflow of blood due to gravity
what is the role of capillaries?
-transport blood close to cells so substances can be exchanged
-narrow lumen to slow blood flow and increase the diffusion time
-thin walls, only one cell thick to decrease diffusion distance
what are the two types of white blood cells?
-phagocytes - engulf pathogens
-lymphocytes - produce antibodies or antitoxins
photosynthesis required practical
-start by taking a boiling tube and place it 10cm away from an LED light source
-fill the boiling tube with sodium hydrogen carbonate solution
-put a piece of pondweed into the boiling tube with the cut end at the top
-leave for five minutes to acclimatise to the conditions in the boiling tube
-bubbles of gas should be produced from the cut end of the pondweed
-this gas is oxygen which is produced by photosynthesis
-start a stop watch and count the number of bubbles produced in one minute
-repeat two more times and calculate the mean number of bubbles produced in one minute
-do whole experiment again with different distances
why is an LED light used?
-these do not release a lot of heat, too much heat would change the temperature of the experiment
why is sodium hydrogen carbonate solution used?
-it releases carbon dioxide which is needed for photosynthesis
what are the two problems with the photosynthesis required practical and the solutions
-the number of bubbles can be too fast to count accurately
-the bubbles are not always the same size
-a large bubble would count the same as a small bubble
-place the pond-weed under a funnel and catch the bubbles in a measuring cylinder
-then use the measuring cylinder to measure the volume of the oxygen gas produced
what is the inverse-square law?
-if we double the distance, the light intensity falls by a factor of four
describe how to prepare an uncontaminated bacterial culture using aseptic technique
-first sterilise all petri dishes, bacterial nutrient broth and agar
-this kills any unwanted microorganisms and prevents contamination
-bacteria are normally transferred into the culture using an inoculating loop
-we sterilise the inoculating loop by passing it through a bunsen burner flame
-we attach the lid of the petri dish using adhesive tape. This stops the lid from falling off and unwanted microorganisms entering
-we then place the agar plate upside down into an incubator. This stops moisture from dripping down onto the bacteria and disrupting the colonies
-we incubate bacteria at 25 degrees to reduce chances of harmful bacteria growing
describe how to investigate the effects of antibiotics on bacterial growth
-clean the bench with disinfectant solution. This kills microorganisms that could contaminate our culture
-we sterilise an inoculating loop by passing it through a bunsen burner flame
-open a sterile gel plate near a bunsen burner flame. The flame kills bacteria in the air
-use the loop to spread the chosen bacteria evenly over the plate
-place sterile filter paper discs containing antibiotic onto the plate
-incubate the plate at 25 degrees
Describe how to investigate the effects of osmosis on plant tissue
-we peel the potato because potato skin can affect osmosis
-use a cork borer to produce three cylinders of potato
-using a cork borer makes all of the cylinders have the same diameter
-use a scalpel to trim the cylinders to the same length
-measure the length of each cylinder using a ruler and the mass of each cylinder using a balance
-place each cylinder into a test tube and add 10 cm^3 of 0.5 molar sugar solution to the first test tube
-add 10cm^3 of 0.25 molar sugar solution to the second test tube and 10cm^3 of distilled water to the third test tube
-leave the potato cylinders overnight to allow osmosis to take place
-remove the potato cylinders and gently roll them on paper towel to remove any surface moisture
-measure the length and mass of the cylinders again
-describe how to investigate the effects of pH on amylase
-Add iodine solution to each well of a spotting tile.
-Use 3 test tubes: one with 2 cm³ starch, one with 2 cm³ amylase, and one with 2 cm³ buffer solution (e.g., pH 5).
-place all test tubes in a 30°C water bath for 10 minutes to allow them to reach the same temperature
-Mix all three solutions in one test tube, return to the water bath, and start the stopwatch.
-Every 30 seconds, place a drop of the mixture onto the iodine in the spotting tile.
-When iodine stays orange, starch is fully broken down.
-Repeat the experiment with different pH buffer solutions (e.g., pH 6, 7, 8) to find the pH with the fastest reaction.
