Photosynthesis

3.2 – Light Independent reaction

Settling activity

• Using Fig 7 worksheet draw boxes around the 3 sets of reactions in the light dependent reaction

Learning outcomes

By the end of this lesson I will know –

• The light-Independent reaction in detail

• That carbon dioxide is accepted by ribulose bisphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate

• That ATP and reduced NADP are required for the reduction of GP to triose phosphate

• That RuBP is regenerated in the calvin cycle

• That triose phosphate is converted to useful organic substances

Success criteria

By the end of this lesson I can –

• Construct a diagram of the light independent reaction

• Answer exam questions on the work covered so far

Starter• Where does the light dependent reaction of

photosynthesis take place?• Thylakoids (disc structures that are stacked

together in groups called grana)• Name 2 ways chloroplasts structurally adapted

to their function of capturing sunlight and carrying out the light dependent reaction.

• Thylakoid membranes have a large surface area for the attachment of chlorophyll, electron carriers and enzymes

• Proteins in the grana hold the chlorophyll to get optimum light absorption

• Granal membranes have enzymes attached which help make ATP

• Chloroplasts contain DNA and ribosomes so they can quickly manufacture proteins needed for the light dependent reaction

Light independent reaction

• What are the light dependent products?• ATP and reduced NADP• Where does the light independent reaction

take place?• Stroma• How is the stroma adapted for this reaction?• Fluid contains enzymes that reduce carbon

dioxide• Fluid surrounds grana so products of light

dependent can diffuse through• Contains DNA and ribosomes so it can make

proteins

The Calvin cycle1. Carbon dioxide diffuse through the stroma and

dissolves into mesophyll cell walls, the membrane, cytoplasm, chloroplast membranes and stroma

2. Carbon dioxide is taken up by ribulose bisphosphate (RuBP), a 5-carbon compound. This gives an unstable 6-carbon compound, which quickly breaks down into 2 x 3-carbon glycerate 3-phosphate (GP)

3. This reaction is catalysed by the enzymes ribulose bisphosphate carboxylase (rubisco).

4. Activated GP is reduced by (ATP and reduced NADP) into triose phosphate (TP)

5. NADP is reduced further going back into the light dependent reaction by accepting more H+

6. Most Triose phosphate (TP) is use to regenerate RuBP using ATP

7. Some TP is converted to useful organic substances such as glucose

The light-independent reactions of photosynthesis: Calvin Cycle

CO2 (1C)

Unstable intermediate (6C)

GP2X Glycerate-3-phosphate

(3C)TP

2X Triose phosphate

(3C)

RuBPRibulose bisphosphate

(5C)

Glucose (6C), amino acids and lipids

Rubisco

Reduced NADPNADP

ATPADP + Pi

ATP

ADP

Tasks1) Complete the cut and stick of the

calvin cycle using the information from the lesson.

2) Complete the exam paper question

Homework – Complete exam questions

PlenaryConstruct a simple overview of photosynthesis

Learning outcomes

By the end of this lesson I will know –

• The light-Independent reaction in detail

• That carbon dioxide is accepted by ribulose bisphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate

• That ATP and reduced NADP are required for the reduction of GP to triose phosphate

• That RuBP is regenerated in the calvin cycle

• That triose phosphate is converted to useful organic substances

Success criteria

By the end of this lesson I can – • Construct a diagram of the

light independent reaction• Answer exam questions on

the work covered so far