PHOTOSYNTHESIS THE PRACTICALS 16 APRIL 2014 Lessn Descriptin In this lessn, we will: Review the prcess f phtsynthesis Study the starch test in leaves Study the varius practicals testing phtsynthesis Lk at hw t cmplete a practical write-up Summary Phtsynthesis (Slutins fr all Life Sciences, Macmillan, p121) Phtsynthesis is a prcess whereby light is cnverted int chemical energy. Sunlight is changed int the chemical energy f sugars and ther rganic cmpunds. This prcess cnsists f a series f chemical reactins that require carbn dixide (CO 2 ) and water (H 2 O) and stre chemical energy in the frm f sugar. Phtsynthesis ccurs in the chlrplast. It is an anablic prcess and requires enzymes. Testing fr the presence f Starch The first thing yu need t be able t d is t test fr starch. The test fr starch ges as fllws: Yu will need the fllwing: A beaker cntaining water Tripd stand and wire gauze Bunsen burner r spirit burner Test tube cntaining methylated spirits Frceps White tile Idine slutin Drpper r pipette
Methd (Slutins fr all Life Sciences, Macmillan, p128) Remve a leaf frm a healthy grwing plant. Put the leaf in biling water When the leaf has gne sft (flaccid) take it ut f the water and put it int methylated spirits r ethanl. (Keep the spirits away frm flame.) The chlrphyll will mve ut f the leaf and int the methylated spirits r ethanl. Remve the leaf frm the methylated spirits and wash it in the biling water. Put the leaf nt the white tile and flatten it ut. Drp a few drps f idine slutin nt the leaf and watch fr a clur change. Phtsynthesis Practicals Practical 1 (http://hazell11bi.blgspt.cm/2013/03/phtsynthesis.html) T determine whether light is necessary fr phtsynthesis Requirements: Pt plant that has been kept in the dark fr 48 hurs Tin fil Scissrs Starch test materials
Methd: Cut a shape int a wide strip f tinfil. Wrap the tin fil arund the leaf with the shape n the tp f the leaf. Yu dn t have t cver the whle leaf. Leave the plant in the sun fr several hurs. After several hurs remve the leaf frm the plant and perfrm the starch test n it. Practical 2 (Adapted frm Slutins fr all Life Sciences, Macmillan, p129) T determine whether chlrphyll is necessary fr phtsynthesis Requirements: Plant with variegated leaves left in the dark fr 48 hurs Starch test materials Methd: Remve the plant frm the dark and put it int the sun fr several hurs. Perfrm the starch test n a leaf. Result: (http://landscaping.abut.cm/d/galleryflandscapephts/ig/variegated-leaves/variegatedmaples.htm) There will be starch present where the green parts if the leaf were and n starch in the white areas.
Practical 3 T determine whether carbn dixide is necessary fr phtsynthesis Requirements: 2 pt plants left in the dark fr 48 hurs Sdium hydrxide slutin (NaOH) Sdium hydrgen carbnate slutin (NaHCO 3 ) 2 large plastic bags 2 elastics Starch test materials Methd: Remve the plants frm the dark Place a cntainer f sdium hydrxide n the sil f ne plant. Place a cntainer f sdium hydrgen carbnate n the sil f the secnd plant. Cver bth plants with a plastic bag and secure with the elastics. Leave the plants in the sun fr several hurs. Remve a leaf frm each plant Perfrm the starch test n each leaf. Result: Practical 4 (Adapted frm Slutins fr all Life Sciences, Macmillan, p131) The plant that had sdium hydrxide with it in the plastic bag will prduce less starch. The plant that had sdium hydrgen carbnate with it in the plastic bag will prduce mre starch. T determine whether xygen is prduced during phtsynthesis Requirements: Tw beakers Water Tw filter funnels Tw test tubes Prestick Canadian pnd weed (Eldea) 2 elastics A wden splint matches
Methd: Pur water int the tw beakers Place the Eldea in ne beaker Place the funnel upside dwn ver the Eldea and use prestick t keep it abve the bttm f the beaker Place a funnel upside dwn in the secnd beaker als slightly elevated Fill a test tube with water and clse it with yur thumb Place it ver the tp f the funnel Leave the beakers in the sun fr several days After a few days remve the test tube frm the Eldea and clse it with yur thumb Light a splint and blw it ut. Remve yur thumb frm the tp f the test tube and put the splint in. Practical Write Up (Adapted frm Slutins fr all Life Sciences, Macmillan, p132) Investigative questin this is the purpse f the investigatin. The questin we are trying t answer by cmpleting the experiment. Hypthesis the answer yu expect t get frm the investigatin Methd and materials what yu are ging t use and hw yu are ging t perfrm the experiment Variables Independent the factr yu are changing t answer yur questin Dependent the factr that changes because f what the Independent variable des (the answer t the questin) Cntrlled the factr that can change but yu make sure des nt change at all during yur experiment Results what yu have recrded as the answers t yur Investigative questin Analysis an explanatin f yur results Cnclusin Drawing the whle practical tgether summarising the questin, hypthesis and results.
Questin 1 Test Yurself A part f de-starched leaf f a ptted plant was cvered with black paper strips n bth sides and the plant was kept in sunlight fr 8 hurs. The leaf was then tested with idine after biling it in alchl. Only the uncvered part f the leaf turned blue black. The inference is that (a) CO 2 is necessary fr phtsynthesis. (b) light is necessary fr phtsynthesis. (c) chlrphyll is necessary fr phtsynthesis. (d) water is necessary fr phtsynthesis. Questin 2 In an experiment n phtsynthesis, students were instructed t cver a prtin f a leaf f a destarched ptted plant with paque paper as shwn in the figure. A cvered ne f the leaves with red strip, B with green, C with blue and D with black. When the starch test was dne n the leaves after 4 hurs, the result shwed n starch in a.) the prtin cvered with red, green and blue strips. b.) the prtin cvered with green strip. c.) the prtin cvered with black and blue strips. d.) any f the cvered prtins. Questin 3 A student perfrmed the starch test n a leaf. Sme steps invlved are shwn belw.
The crrect sequence f steps shuld be a.) iv; iii; ii; i. b.) i; ii; iii; iv. c.) ii; iii; iv; i. d.) i; iii; iv; ii. Questin 4 The teacher instructed a student t place a healthy ptted she flwer plant in a dark rm fr 24 hurs prir t an experiment n phtsynthesis. The purpse f placing it in a dark rm is a.) t increase the intake f CO 2 b.) t activate the chlrplasts in the leaves. c.) t de-starch the leaves. d.) t denature the enzymes in the leaves. Questin 5 In an experiment t shw that sunlight is necessary fr phtsynthesis, the leaf is biled in alchl fr a few minutes using a water bath. It is essential because a.) alchl is highly vlatile. b.) steam frm the water bath heats the leaf rapidly. c.) steam frm the water bath disslves the chlrphyll. d.) alchl is flammable. Questin 6 In an experiment n phtsynthesis, a student fixed a strip f black paper n the drsal surface f a Bugainvillea leaf in the mrning. In the evening she tested the leaf fr starch. The result was a.) the drsal surface f the leaf was white but the ventral surface turned blue. b.) bth the surfaces f the cvered prtin remained white. c.) the entire leaf turned blue black. d.) the entire leaf remained white. Questin 7 The purpse f testing the prduct f phtsynthesis with a glwing splint is t a.) prve that CO 2 is prduced during phtsynthesis b.) prve that O 2 is prduced during phtsynthesis c.) prve that O 2 is used in phtsynthesis d.) prve that CO 2 is used in phtsynthesis
Questin 1 Imprve yur Skills (http://www.elateafrica.rg/elate/bilgy/nutritin/structured2.jpg) 1.1 What is an apprpriate investigative questin fr this experiment? (2) 1.2 Write an apprpriate hypthesis fr this experiment. (2) 1.3 Write dwn the fllwing variables a) cntrlled (1) b) independent (1) c) dependent (1) 1.4 Write a suitable cnclusin fr this experiment. (3) Questin 2 (http://www.passmyexams.c.uk/gcse/bilgy/images/phtsynthesis-light-graph-03.jpg)
In the diagram there is a graph and a table shwing results f an experiment cnducted relating t phtsynthesis. 2.1 What was the independent variable in the experiment? (1) 2.2 What is the dependent variable in the experiment? (1) 2.3 Hw was the dependent variable measured? (1) 2.4 State an apprpriate cnclusin fr this experiment. (2) Questin 3 Yu are given the fllwing list f apparatus: 2 pt plants left in the dark fr 48 hurs Sdium hydrxide slutin (NaOH) Sdium hydrgen carbnate slutin (NaHCO 3 ) 2 large plastic bags 2 elastics Starch test materials Yu will use this equipment t carry ut an experiment. 3.1 What will the aim f the experiment be? (2) 3.2 What is the purpse f the sdium hydrxide slutin? (1) 3.3 What is the purpse f leaving the pt plants in the dark fr 48 hurs? (1) 3.4 Briefly describe the methd yu wuld emply in this experiment. (6) Links http://www.mindset.c.za/learn/xtra/live http://www.reading.ac.uk/virtualexperiments/ves/prelader-phtsynthesis-full.html