Prescribed Experiments

There are 21 prescribed experiments for LC Biology.

They are examined in section B of the paper. You must complete two out of three questions for a total of 60 marks.

Note: Questions about experiments may also appear in section A and section C.

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QUESTION 8

Cell Structures

Preparation and examination of plant/animal cell under microscope

Food Test for the presence of:

Reducing sugar
Protein
Lipids
Starch

Ecology

Conduct a qualitative and quantitative survey of plants and animals
Determine 3 abiotic factors that affect population

Genetics

Isolation of DNA from a plant tissue

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QUESTION 9 5. Photosynthesis

Effect of light intensity on rate of photosynthesis

Enzymes

Effect of temperature on enzyme activity
Effect of pH on enzyme activity
Demonstrate denaturation of an enzyme through boiling
Demonstrate the activity of an immobilised enzyme and compare to activity of a free enzyme

Respiration

Production of ethanol by fermentation

Movement of Molecules

Demonstrate osmosis

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QUESTION 10 9. Fungi

Growth of leaf yeast on nutrient agar

Plant Reproduction

Factors necessary for germination
Demonstrate starch is digested during germination

Plant Responses

Demonstrate the effect of different concentrations of growth regulator on plant growth

Plant Structure

Prepare and view a dicotyledon stem under a light microscope

Heart

Heart dissection
Effect of exercise on heart rate

Experiment Titles & Controls

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What is the purpose of a control? Comparison. A control provides a standard against which the actual experiment can be measured.

Experiment Title	Control	Heat
Test for a reducing sugar	Distilled water instead of food sample	30°C
Test for starch	Distilled water instead of food sample
Test for protein	Distilled water instead of food sample
Test for lipid	Distilled water instead of food sample
To use a simple key to identify five fauna and flora
To use various pieces of equipment to collect plants and animals in an ecosystem
To carry out a quantitative study of a habitat (plants and animals)
To investigate 3 abiotic factors
To prepare and examine a plant cell under a microscope
To prepare and examine a animal cell under a microscope
To investigate the effect of pH on enzyme activity	Distilled water instead of celery	30°C
To investigate the effect of temperature on enzyme activity	Distilled water instead of celery	Various temperatures
To investigate the effect of denaturation by heat on enzyme activity	Unboiled enzyme & the experiment performed at 27°C	100°C
To prepare and use an immobilized enzyme	Free enzyme (not immobilised)
To investigate the effect of light intensity on the rate of photosynthesis		25°C
To prepare ethanol using yeast by fermentation	Distilled water instead of glucose	30°C
To demonstrate osmosis	Distilled water
To isolate DNA from a plant tissue		Yes
To investigate the growth of leaf yeast on malt/starch agar	No leaf/ oiled dead leaf	30°C
To prepare and examine a transverse section of a dicot stem
To dissect, display and identify parts of the heart
To investigate the effect of exercise on pulse rate
To investigate the effect of exercise on breathing rate
To investigate the effect of growth regulator IAA on plant tissue	Distilled water instead of IAA
To investigate the effect of temperature, water, and oxygen on germination	Seeds with all three factors present (water, oxygen & suitable temperature)	20°C for control. 4°C to show effect of temperature on germination.
To use starch agar or skimmed milk agar plates to show digestive activity during germination	Boiled broad bean seeds	20°C

Chemical/Instrument Needed and Function/Result

Chapter	Test	Chemicals/Instrument	Positive Result/Function
Food	Glucose (reducing sugar)	Fehling's (or benedict's solution) + water bath at 37°C	Blue to brick red
Food	Protein (biuret)	Sodium hydroxide + copper sulphate	Blue to lilac
Food	Starch	Iodine	Brown to blue/black
Food	Fat	Brown paper	Translucent spot
Cell Structure	Animal cell (cheek cell)	Methylene blue	Observe under microscope
Cell Structure	Plant cell (onion cell)	Iodine	Observe under microscope
Cell Structure	Cells	Cover slip	To protect the lens of the microscope
Cell Structure	Cells	Cover slip at 45° angle	To prevent air bubbles
Cell Structure	Cells	Drops of water on slide	To prevent dehydration
Cell Structure	Microscope	Magnification lens	Magnifies object to be observed
Cell Structure	Microscope	Coarse focus wheel	Moves the stage and roughly focuses the image
Cell Structure	Microscope	Fine focus wheel	Brings the image into sharp focus
Enzymes	Enzyme activity	Hydrogen peroxide (substrate). Amylase (enzyme).	Oxygen in the form of foam, produced after 2 minutes
Enzymes	Temperature variation	Temperature controlled water bath at various temperatures	Changing temperature will vary results.
Enzymes	pH variation	pH buffer solutions of various pH	Changing pH will vary results.
Photosynthesis	Carbon dioxide	Limewater	Limewater will take on a milky appearance
Photosynthesis	Photosynthesis	Elodea	Oxygen bubbles produced
Photosynthesis	CO₂ variation	Sodium hydrogen carbonate	Varying amount of chemical will vary CO₂ concentration and affect the number of O₂ bubbles produce.
Photosynthesis	Light intensity variation	Lamp	Moving the lamp away from/towards the experiment will vary amount of O₂ bubbles produced.
Photosynthesis	Temperature maintenance	Temperature controlled water bath	Keeps the temperature constant.
Respiration	Ethanol	Potassium iodide and sodium hypochlorite.	Clear to yellow (crystals if heated)
Ecology	Qualitative analysis	Identification key	Series of questions used to identify animals and plants
Ecology	Qualitative analysis	Pooter	Collects insects
Ecology	Qualitative analysis	Beating tray	Collects insects etc.
Ecology	Qualitative analysis	Pitfall trap	Collects crawling insects etc.
Ecology	Qualitative analysis	Sweep net	Hedgerow insects
Ecology	Qualitative analysis	Tullgren funnel	Collects centipedes etc.
Ecology	Qualitative analysis	Quadrat	Record the number of times a plant appears in an area.
Osmosis	Osmosis	Visking tubing	Acts as a selectively permeable membrane
Plant Structure	Dicot stem analysis	Blade	Cut a thin slice of celery
Plant Structure	Dicot stem analysis	Forceps	Transfer stem to glass slide
Fungi	Leaf yeast	Petroleum jelly	Sticks the leaf to the lid of the agar plate.
Fungi	Leaf yeast	Starch nutrient agar	Supplies the necessary nutrients for microorganisms to grow.
Fungi	Leaf yeast	Methylated spirits	Kills any microorganisms present
Fungi	Leaf yeast	Incubator at 35°C	Temperature at which enzymes in microorganisms work best.
Genetics	DNA isolation	Washing up liquid	Causes breakdown of cell membrane.
Genetics	DNA isolation	Table salt	Causes DNA molecules to clump together.
Genetics	DNA isolation	Water bath at 60°C for no longer than 15 minutes	Speeds up the reaction and denatures enzymes. If heated for longer than 15 minutes, the DNA will begin to breakdown.
Genetics	DNA isolation	Ice bath	Prevents complete denaturation and destruction of DNA.
Genetics	DNA isolation	Food blender	Breaks down cell wall
Genetics	DNA isolation	Filter paper	Collects cell fragments
Genetics	DNA isolation	Protease	Breaks down protein surrounding DNA
Genetics	DNA isolation	Ice cold ethanol	Causes the DNA to separate from the solution. DNA is insoluble in ice cold ethanol.
Plant Reproduction	Germination	Boiled water	To remove oxygen from the water.
Plant Reproduction	Germination	Layer of oil	Create anaerobic conditions by eliminating oxygen.
Plant Reproduction	Germination	Soaking the seeds in water	Softens testa and activates germination.
Plant Reproduction	Germination	IAA (indole acetic acid)	Affects the length of root and shoot growth: • Promotes root growths at low concentration. • Promotes shoot growth at high concentration.

Prescribed Experiments Simplified Revision Notes for Leaving Cert Biology

Prescribed Experiments

Experiment Titles & Controls

Chemical/Instrument Needed and Function/Result

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