2.19: Know the Word Equation and the Balanced Chemical Symbol Equation for Photosynthesis

PHOTOSYNTHESIS: Production of Carbon compounds (Glucose) in cells by using light energy from the Sun

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EQUATION OF PHOTOSYNTHESIS:

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

2.18: Understand the Process of Photosynthesis and its Importance in the Conversion of Light Energy to Chemical Energy

PHOTOSYNTHESIS: Production of Carbon compounds (Glucose) in cells using light energy from the Sun

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• Light energy from the sun is absorbed by Chlorophyll to produce Glucose which is stored as Starch for growth, and Oxygen as a waste product
• Glucose produced in Photosynthesis is passed down the food chain from one organism to another, hence why Plants are called Producers (bottom of the food chain)
• While Photosynthesis only occurs under the presence of sunlight, aerobic respiration occurs at all times of day and uses Glucose produced from Photosynthesis to produce energy (used for cell growth) and Carbon Dioxide (waste product or used for Photosynthesis)

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EQUATION OF PHOTOSYNTHESIS:

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

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

PHOTOSYNTHESIS: Production of Carbon compounds (Glucose) in cells using light energy from the Sun

FACTORS THAT AFFECT RATE OF PHOTOSYNTHESIS:

FACTOR	EXPLANATION
CARBON DIOXIDE	As the concentration of Carbon Dioxide increases, the rate of Photosynthesis will increase As Carbon Dioxide is a reactant in Photosynthesis, the increase in Carbon Dioxide concentration will allow more Photosynthesis to occur, hence increasing the rate of Photosynthesis However, as concentration of Carbon Dioxide increases beyond a certain point, rate of Photosynthesis with plateau as another factor will be the limiting factor
TEMPERATURE	As temperature increases towards optimum, the rate of Photosynthesis will increase This is because the increase in temperature towards optimum will allow optimum enzyme activity for Photosynthesis-related enzymes, hence increasing the rate of photosynthesis However, as temperature increases above optimum, enzymes involved in Photosynthesis will denature, therefore causing the rate of Photosynthesis to decrease
LIGHT INTENSITY	As light intensity increases, the rate of Photosynthesis will increase As Photosynthesis can only occur under the presence of light, the increase in light intensity will therefore allow more Photosynthesis to occur, increasing the rate of Photosynthesis However, as light intensity increases beyond a certain point, the rate of Photosynthesis will plateau as another factor is the limiting factor

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

DIAGRAM OF LEAF STRUCTURE:

                                    

Diagram showing the Structure of a Leaf

STRUCTURE OF THE LEAF:

STRUCTURE	DESCRIPTION
WAX CUTICLE	Outermost protective layer that prevents Water loss via evaporation
UPPER EPIDERMIS	Thin and transparent layer of cells to allow light to enter Palisade Mesophyll
PALISADE MESOPHYLL	Layer tightly packed with Chloroplasts to maximise light absorption for Photosynthesis
SPONGY MESOPHYLL	Layer containing internal air spaces to increases surface area to volume ratio for the diffusion of gases (mainly Carbon Dioxide)
LOWER EPIDERMIS	Layer containing: Guard cells: cells that flank and control the opening and closing of Stomata by absorbing and losing Water to regulate gas exchange and prevent water loss (via transpiration) Stomata: mouth-shaped opening flanked and controlled by Guard cells to regulate gas exchange and prevent Water loss (via transpiration)

*ADAPTATIONS FOR PHOTOSYNTHESIS (FEATURES):

FEATURE	ADAPTATION
LARGE SURFACE AREA (LEAF)	Increases surface area to volume ratio (SA:V) for diffusion of Carbon Dioxide and absorption of light for Photosynthesis
THIN	Short diffusion length which increases the rate of diffusion of Carbon Dioxide into leaf cells, e.g Chloroplasts
CHLOROPHYLL	Tightly packed and present in large amounts in Palisade Mesophyll to maximise light absorption for Photosynthesis
NETWORK OF VEINS	Supports the leaf and transports Water for Photosynthesis and Transpiration (via Xylem), and Carbohydrates produced by Photosynthesis (via Phloem) from sources to sinks
STOMATA	Regulates gas exchange by allowing Carbon Dioxide to diffuse into the leaf for use in Photosynthesis, and Oxygen to diffuse out as waste product of Photosynthesis

2.22: 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	Needed to build Chlorophyll for growth Deficiency: Leaves turn yellow
NITRATE	Needed to produce Amino acids to build Protein and DNA Deficiency: Leaves turn yellow and stunted growth

2.23: Practical: Investigate Photosynthesis, Showing the Evolution of Oxygen from a Water Plant, the Production of Starch and the Requirements of Light, Carbon Dioxide and Chlorophyll

INVESTIGATING PHOTOSYNTHESIS

Diagram showing Experiment to Investigate the Effect of Light intensity on Photosynthesis in Pond Weed

METHOD: Place pond weed in a beaker of water Change the independent variable Leave for 5 Minutes to allow pond weed to adapt to environment Count the number of air bubbles produced in a fixed period of time Increase or decrease the independent variable by a fixed increment (e.g, distance of lamp to change light intensity) Repeat process to obtain a range of data and analyse results

INDEPENDENT VARIABLES: LIGHT INTENSITY Use a lamp and change light intensity by adjusting the distance between lamp and pond weed CARBON DIOXIDE CONCENTRATION To increase Carbon Dioxide concentration, add Sodium Bicarbonate into beaker of Water To decrease Carbon Dioxide concentration, add Sodium Hydroxide into beaker of Water CHLOROPHYLL Use variegated plant - Green plant containing Chlorophyll, and White plant without Chlorophyll

2.24: Understand that a Balanced Diet Includes appropriate Proportions of Carbohydrate, Protein, Lipid, Vitamins, Minerals, Water and Dietary Fibre

BALANCED DIET: Diet in which all components needed to maintain health are present in appropriate proportions

• Humans need to eat a balanced diet to ensure the body is provided with components to maintain good health

IMPORTANT DIETS CONSIST OF:

DIET
CARBOHYDRATE	LIPIDS	WATER
PROTEIN	DIETARY FIBRE
VITAMINS	MINERALS

2.26: Understand How Energy Requirements Vary with Activity Levels, Age and Pregnancy

FACTORS THAT AFFECT ENERGY REQUIREMENTS:

FACTOR	EXPLANATION
AGE	Amount of energy required increases towards adulthood for growth and muscle development
ACTIVITY LEVELS	Amount of energy required increases with activity level as more energy is needed to allow muscle contractions to facilitate exercise via respiration
PREGNANCY	Amount of energy required by Females during pregnancy will increase as more energy is needed to support the growth of developing fetus, and the large mass that the Mother will carry around

2.25: Identify the Sources and Describe the Functions of Carbohydrate, Protein, Lipid (Fats and Oils), Vitamins A, C, and D, the Mineral Ions Calcium and Iron, Water and Dietary Fibre as Components of the Diet

DIET	FUNCTION
CARBOHYDRATE	Direct energy source Deficiency: Lack of energy Source: Meat, Starch
PROTEIN	Growth and repair Deficiency: Marasmus - poor growth Source: Meat
VITAMIN A	Healthy eyesight Deficiency: Night Blindness Source: Carrots
VITAMIN C	Heal wounds and rebuilds tissue Deficiency: Scurvy - bleeding gums Source: Lemon
VITAMIN D	Strengthen teeth and bones Deficiency: Rickets - curvature of bones Source: Margarine
LIPID	Insulation and Energy Storage Source: Meat
DIETARY FIBRE	Lowers Cholesterol Deficiency: Constipation Source: Vegetables
CALCIUM	Strengthen Teeth and Bones Deficiency: Rickets - curvature of bones Source: Milk
IRON	Promote Haemoglobin Deficiency: Anaemia - poor Oxygen transport Source: Meat
WATER	Allows chemical reactions to occur Source: Water