Photosynthesis 6.3 Dark Reaction (Photorespiration)

 

*PDP SEMASA PKPB (BELAJAR DARI RUMAH)*

*Minggu 45* 

*23 hingga 27 Nov 2020*

*SUBJEK* : BIOLOGI

*TARIKH* : 26.11.2020

*HARI* : Khamis 11.30 - 1.30pm

*TAJUK* :  6.3 Light Independent (Photorespiration)

*BUKU/BAHAN* : Lembaran Latihan 6.3, video pembelajaran melalui youtube. 

*AKTIVITI* :

1. Murid diminta menonton video pembelajaran melalui link youtube ini  https://youtu.be/I94KGY2li14

 sehingga  selesai. 

2.Murid diminta mendengar dan menyebut "3 pathways" yang terlibat dalam "Light Independent Reaction". 

3.Murid diminta menjawab soalan latihan no 2 & 3  (mengandungi 10 soalan struktur) dalam modul CHAP 6: PHOTOSYNTHESIS yang diberikan.

TIPS:

Photorespiration is a process in the metabolism of plants in which RuBP (a sugar) combines with oxygen with the help of an enzyme (Rubisco), instead of carbon dioxide during normal photosynthesis.

UNDER WHAT CONDITION DOES PHOTORESPIRATION OCCUR?

During dry-hot seasons, plants are forced to close their stomata. Thus, the concentration of carbon dioxidein the leaf decreases. If the plant continues to fix CO2 when its stomata are closed., the CO2 will get used up and the O2 / CO2 ratio in the leaf will increase. O2 will compete with CO2 for the active sites in Rubisco. Rubisco starts to combine with O2 with RuBP instead of Co2.

2. a) i. A = bundle sheath cell B = mesophyll cell 

ii. The initial fixation of carbon dioxide takes place in the mesophyll cell 

b) i. D = Phosphoenolpyruvate (PEP) F = malic acid 

ii. C = ATP 

iii. E = CO2 

c) i. PEP carboxylase 

d) i. Sugar cane, maize, tropical grasses and cereal – any 2. 

ii. In these plants carbon dioxide first combines with phosphoenolpyruvate to form a four carbon compound (oxaloacetate). 

e) i. Tropical grasses are exposed to high rate of photorespiration. Concentration of carbon dioxide is low relative to oxygen gas. So that oxygen gas will combine with Ribulose biphosphate (RuBP). 

ii. By keeping RuBP and RuBP carboxylase (Rubisco) well away from high oxygen concentration. RuBP and RuBP carboxylase are placed in bundle sheath so, by arranging the bundle sheath cells around the vascular bundle they would have no direct contact with the air.