2.17: Describe the process of Photosynthesis and Understand its importance in the Conversion of Light Energy to Chemical Energy

PHOTOSYNTHESIS: Conversion of Light Energy from the Sun into Chemical Energy by Chlorophyll such as Glucose, which is then stored as Starch

• Occurs only in the presence of Light
• Glucose produced by Photosynthesis is passed down the Food Chain, hence why Plants are called Producers (Bottom of the Food Chain)
• Glucose produced is also used in Aerobic Respiration to release Energy for Growth

 s

EQUATION OF PHOTOSYNTHESIS:

Carbon Dioxide       +       Water       →       Glucose       +       Oxygen          6CO2                          H2O                    C6H12O6                     6O2

2.18: Write the Word Equation and the Balanced Chemical Symbol Equation for Photosynthesis

PHOTOSYNTHESIS: Conversion of Light Energy from the Sun into Chemical Energy by Chlorophyll such as Glucose, which is then stored as Starch

 s

EQUATION OF PHOTOSYNTHESIS:

Carbon Dioxide       +       Water       →       Glucose       +       Oxygen          6CO2                          H2O                    C6H12O6                     6O2

2.20: Describe the Structure of the Leaf and Explain How it is Adapted for Photosynthesis

Diagram:

                              

STRUCTURE OF THE LEAF:

STRUCTURE	DESCRIPTION
WAX CUTICLE	Protective layer on top of the Leaf, Prevents Water from Evaporating
UPPER EPIDERMIS	Thin and Transparent to allow Light to Enter Palisade Mesophyll
PALISADE MESOPHYLL	Tightly Packed with Chloroplasts to Absorb More Light, Maximising Photosynthesis
SPONGY MESOPHYLL	Contains Internal Air Spaces that Increases the Surface Area to Volume Ratio for the Diffusion of Gases (Mainly Carbon Dioxide)
LOWER EPIDERMIS	Contains Guard Cells and Stomata
GUARD CELL	Absorbs and Loses Water to Open and Close the Stomata to Allow Carbon Dioxide to Diffuse in, Oxygen to Diffuse Out
STOMATA	Where Gas Exchange takes place, Opens during the Day, Closes during the Night

ADAPTATIONS FOR PHOTOSYNTHESIS:

PHOTOSYNTHESIS: Conversion of Light Energy from the Sun into Chemical Energy by Chlorophyll such as Glucose, which is then stored as Starch

FEATURE	ADAPTATION
LARGE SURFACE AREA (LEAF)	Increases Surface Area for the Diffusion of Carbon Dioxide and Absorption of Light for Photosynthesis
THIN	Allows Carbon Dioxide to Diffuse into Leaf Cells Easily, e.g Chloroplasts
CHLOROPHYLL	Absorbs Light Energy and Converts it into Chemical Energy such as Glucose which is the stored as Starch
NETWORK OF VEINS	Allows the Transport of Water and Carbohydrates from the Leaves of the Plants for Photosynthesis (Water FOR Photosynthesis, Carbohydrates as a PRODUCT of Photosynthesis)
STOMATA	Allows Carbon Dioxide to Diffuse into the Leaf
EPIDERMIS IS THIN AND TRANSPARENT	Allows More Light to reach the Palisade Cells
THIN CUTICLE MADE OF WAX	To Protect the Leaf without Blocking Sunlight
PALISADE CELL LAYER AT TOP OF LEAF	Maximises the Absorption of Light as it is directly underneath Sunlight
SPONGY LAYER	Air Spaces allow Carbon Dioxide to Diffuse through the Leaf, Increasing the Surface Area
PALISADE CELLS CONTAIN MANY CHLOROPLASTS	Absorbs More Light so Maximises Photosynthesis

2.19: Understand how Varying Carbon Dioxide Concentration, Light Intensity and Temperature affects the Rate of Photosynthesis

PHOTOSYNTHESIS: Conversion of Light Energy from the Sun into Chemical Energy by Chlorophyll such as Glucose, which is then stored as Starch

FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS:

FACTOR	EXPLANATION
CARBON DIOXIDE	Carbon Dioxide is a Reactant so the More Carbon Dioxide there is, the More Photosynthesis can Take place as it will no longer be the Limiting Factor Rate of Photosynthesis will Increase
TEMPERATURE	Increase in Temperature, this will be closer to Optimum Temperature so Enzyme Activity will Increase Increase in Enzyme Activity, Rate of Chemical Reactions in the Plant will Increase (Occur Faster) Rate of Photosynthesis will Increase
LIGHT INTENSITY	Light is the Condition for Photosynthesis, the Higher the Light Intensity, the More Light Energy there is for Chlorophyll to absorb and Convert into Chemical Energy Rate of Photosynthesis will Increase

2.22: Describe Experiments to Investigate Photosynthesis, Showing the Evolution of Oxygen from a Water Plant, the Production of Starch and the Requirements of Light, Carbon Dioxide and Chlorophyll

EXPERIMENT:

INVESTIGATING PHOTOSYNTHESIS

Pond Weed in Water                    Variable: Light

METHOD: Set up the Apparatus as in the Diagram Change Variable Leave for 5 Minutes to allow the Pond Weed to adapt to environment Count number of Bubbles Given Off in One Minute Increase or Decrease the Variable (E.g, distance of lamp) Repeat Experiment Other variables

VARIABLES: LIGHT Use a Lamp and Vary the Distance of the Lamp to the Pondweed to Control the Light Intensity CARBON DIOXIDE Add Sodium Hydroxide to Absorb and Remove all Carbon Dioxide Add Sodium Bicarbonate to Increase Carbon Dioxide CHLOROPHYLL Use Variegated Plant (White Plant and Green Plant)

2.21: Understand that Plants require Mineral Ions for Growth and that Magnesium Ions are needed for Chlorophyll and Nitrate Ions are needed for Amino Acids

MINERAL IONS:

MINERAL ION	FUNCTION
MAGNESIUM	Magnesium is needed to Build Chlorophyll DEFICIENCY: Causes Leaves to turn Yellow
NITRATE	Nitrates are need to produce Amino Acids to Build Protein and DNA DEFICIENCY: Causes Leaves to turn Yellow and Stunted Growth

2.39: Understand Gas Exchange ( of Carbon Dioxide and Oxygen) in Relation to Respiration and Photosynthesis

AEROBIC RESPIRATION:  Breakdown of Glucose to release Energy in the Presence of Oxygen

EQUATION:

Glucose       +       Oxygen       →       Carbon dioxide       +       Water C6H12O6                      6O2                               6CO2                          H2O

 

GAS EXCHANGE:

• Oxygen is Taken in by Respiring Cells (Mitochondria) and Carbon Dioxide is Produced as Waste Products

PHOTOSYNTHESIS: Conversion of Light Energy from the Sun into Chemical Energy by Chlorophyll such as Glucose, which is then stored as Starch

EQUATION:

Carbon Dioxide       +       Water       →       Glucose       +       Oxygen        6CO2                            H2O                    C6H12O6                   6O2

 

GAS EXCHANGE:

• Carbon Dioxide is Taken in by Photosynthesizing Cells (Chloroplast) and Oxygen is Produced as Waste Products (If not Used for Aerobic Respiration)

2.40: Understand that Respiration Continues during the Day and Night, but that the Net Exchange of Carbon Dioxide and Oxygen Depends on the Intensity of Light

PLANTS

• Plants Respire during the day and night, But they can Only conduct Photosynthesis during the Day when Light is Present

PROCESS	DAY	NIGHT
RESPIRATION	✓	✓
PHOTOSYNTHESIS	✓	✗

PLANTS AND GAS EXCHANGE

• Using the Table Above, the Reactants and Products of Aerobic Respiration and Photosynthesis will Reverse Each Other

PROCESS	CARBON DIOXIDE	OXYGEN
RESPIRATION	Out	In
PHOTOSYNTHESIS	In	Out

NET GAS EXCHANGE

DURING THE DAY

Net Exchange of Gases During the Day

Respiration takes Place All the Time so Carbon Dioxide will be Taken in by Respiring Cells, and Carbon Dioxide will be Produced as a Waste Product In Daytime, Light is Present which Allows Photosynthesis to Occur, So Carbon Dioxide will be Taken In by Photosynthesizing Cells in Plants and Oxygen will be Produced as a Waste Product Oxygen is Being Both Used and Produced, and Carbon Dioxide is Being Both Used and produced, Causing the Net Exchange of Gases to be Balanced During the Day

DURING THE NIGHT

Net Exchange of Gases During the Night

Respiration takes Place All the Time so Carbon Dioxide will be Taken in by Respiring Cells, and Carbon Dioxide will be Produced as a Waste Product At Night, Light is Not Present so Photosynthesis will Not Occur, So Carbon Dioxide will Not be Taken In by Photosynthesizing Cells in Plants and Oxygen will Not be Produced as a Waste Product Oxygen Will be Used by Respiration, Carbon Dioxide will be Produced by Respiration So Net Exchange of Oxygen will have an Increased Input and Net Exchange of Carbon Dioxide will have an Increased Output