6.2 LIGHT DEPENDENT REACTIONS

*PDP SEMASA PKPB (BELAJAR DARI RUMAH)*

*Minggu 44* 

*16 hingga 20 Nov 2020*

*SUBJEK* : BIOLOGI

*TARIKH* : 19.11.2020

*HARI* : Khamis 11.30 -2.00pm

*TAJUK* :  6.2 Light Dependent

*BUKU/BAHAN* : Lembaran Latihan 6.2, video pembelajaran melalui youtube. 

*AKTIVITI* :

1. Murid diminta menonton video pembelajaran melalui link youtube ini  https://www.youtube.com/embed/4s2HVEUEwRY sehingga  selesai. 

2.Murid diminta mendengar dan menyebut 3 jenis "electron carrier proteins"yang terlibat dalam "Light Dependent Reaction". 

3.Murid diminta menjawab soalan latihan no 1 hingga 5  (mengandungi 16 soalan struktur) dalam modul CHAP 6: PHOTOSYNTHESIS yang diberikan. 

BERIKUT ADALAH JAWAPAN KEPADA LATIHAN YANG DIBERIKAN. BELAJAR RAJIN-RAJIN TAU! 

Worksheet Answers

1.      a) Photosynthesis is a process by which organic molecules are produced from inorganic components by green plants and other autotrophic organisms in the presence of light energy

b)             i.          - Light reaction

- Dark reaction

 

ii.         – Light reaction – granum of     chloroplast -  Dark reaction – stroma of chloroplast

b)             -    photolysis

-       cyclic photophosphorylation

-       non-cyclic photophosphorylation

 

2.      a)        from water

 

b)             i.  A water molecule is split into its components: two electrons: two proton / 2H⁺ and one oxygen atom.

 

H₂O                    2e^- + 2H⁺ + ½ O₂

             

These two electrons then replace the two electrons that have left the reaction centre P680 of photosystem II. The oxygen atom will combine with another oxygen atom to form oxygen gas. The two H⁺ are moved into the thylakoid spaces and go on to reduce the NADP.

 ii. -     Water is a source of hydrogen which reduces NADP to NADPH + H⁺ / NADPH₂ -     Water is a source of electron which replace those lost by chlorophyll a (P680). -     The excited electrons release energy which is used to make ATP.

 

3.      a) -     Light is absorbed by photosystem II.

-        Two energised electrons are emitted.

-        The energised electrons rise to a higher energy level.

-        Then they are picked up by an electron acceptor.

-        The electron acceptor passes the electrons along a chain of electron carriers to photosystems I.

-        The energy released from the electron is used to make ATP from Adp + P_i.

 b)             Two photosystems are involved because there is insufficient energy in the light to energise the electrons  from water straight to NADP.

 c)              i.    They will both be positive and unstable.

ii.    The two electrons released from the P680 of photosystem II will go to replace the two electrons lost from photosystem I. At the same time P680 of photosystem II receives its replacement electron from photolysis.

 d)             Electrons are raised to a higher energy level. They are passed through a series of hydrogen acceptors. Proton / H⁺ ion are produced from the photolysis of water then go on to reduce the NADP to become NADPH + H⁺ 

4.             a)  Non-cyclic photophosphorylation uses the light energy to build both ATP and NADPH.  Whereas cyclic photophosphorylation uses the light energy to build only ATP.

b) 

	Cyclic	Non-cyclic
Used	photons ADP phosphate group	photons ADP phosphate group water NADP+
Produced	ATP	ATP NADPH2 oxygen
Accomplished	captured energy in the form of ATP	captured energy in the form of ATP and NADPH

5.

Photosystem I	Photosystem II
Consists of three kinds of pigments (chlorophyll a, b and carotenoids)   Chlorophyll a most abundant	Consists of three kinds of pigments (chlorophyll a, b and carotenoids)   Chlorophyll b most abundant
Reaction centre is called P700	Reaction centre is called P680
FeS – primary electron acceptor	Substance Q – primary electron acceptor
Electron carriers : -  ferredoxin (Fd) -  flavoprotein (FAD) -  nicotinamide dinucleotide phosphate (NADP+)	Electron carriers : -       plastoquinone (Pq) -       cytochrome complex     - plastocyanin (Pc)