PHOTOSYNTHESIS

CARBON DIOXIDE + WATER --> GLUCOSE + OXYGEN

The glucose is either utilised for respiration, stored as starch or transported to another part of the plant.

The water enters the plant through the roots, the gases enter and leave through the leaf.

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• Carbon dioxide comes from the air.
• It enters the plant through the root and travels up the stem via the xylem.
• Glucose is the food and is stored as starch.
• Oxygen is the by product of this reaction

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• Gases enter and leave the leaf through tiny holes called stomata
• These are on the under side of the nucleus.

INFORMATION

• The waxy layer means that the rain water falls of into the soil that the roots can absorb it.
• The stomata are small openings in the underside of the leaf that allow gases and water to pass in and of the leaf.
• The guard cells Control the amount of opening/closing of the stomata and hence the rate of water loss from the leaf.
• The palisade mesophyll is packed full of chloroplast containing cells near the surface of the leaf, this maximises the use of the light.
• The spongy mesophyll has spaces between the cells to allow gases to pass through the leaf.

MINERALS

Phosphate ions (po4). The use of phosphate ions is for respiration and growth. The symptoms is poor growth and discoloured leaves. Phosphate ions are a component of DNA molecules and cell membranes.

Nitrate ions (NO3)
Are used as building protein and growth. The symptoms are poor growth and yellow leaves . All amino acids contain nitrogen. Amino acids ARE the building blocks of protein.

Potassium ions (k+)
It is used by respiration and photosynthesis . The symptoms are poor flowers and fruit growth, discoloured leaves. To use this it must be present for photosynthesis and respiration enzymes to work.

Magnesium lons (Mg2)
It uses photosynthesis. The symptoms are yellow leaves. Chlorophyll molecules contain magnesium ions. It's the magnesium that makes the chlorophyll green.

If a plant shows poor growth it may be due to a lack of one or more minerals in the soil. It's possible to do chemical tests to find out which minerals are deficient, but it's often more convenient to add a general fertiliser. This is sometimes called NPK fertiliser because it contains the elements nitrogen (N), phosphorus (P) and potassium (K). These elements, plus magnesium (Mg), are the minerals that plants need in the greatest quantities.

The concentration of minerals in the soil is very low. They dissolve in water and move around the soil in solution. Root hair cells are adapted to absorb the water out of soil by osmosis – they have a large surface area, thin walls and are close to the xylem cells used for transporting water up the plant. Minerals cannot be absorbed by osmosis (which is the movement of water only) or diffusion (because the minerals are in very low concentration). The root hair cells have carrier molecules on their surface that pick up the minerals and move them into the cell against the concentration gradient. This requires energy, and is called active transport.

FRONT OF A LEAF

BACK OF THE LEAF.

Photosynthesis-
Creating something with light.

Chemosynthesis -
Creating food with chemicals.

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• Some micro-organisms produce their own food by chemosynthesis.
• They use a variety of chemical reactions ( so chemical energy, rather than light energy)
• There is no general word equation since the reactions vary.
• They often use carbon dioxide as a reactant.
• These type of organisms are called chemosynthetic.

THE EQUATION FOR PHOTOSYNTHESIS

Photosynthesis can be represented using a chemical equation.
The overall balanced equation is...

6CO2 + 6H2O ------> C6H12O6 + 6O2
Sunlight energy



Where: CO2 = carbon dioxide
H2O = water
Light energy is required
C6H12O6 = glucose
O2 = oxygen



Continue

The glucose is either utilised for respiration stored as starch or transported to another part of the plant.

The water enters the plant through the roots, the gases enter and leave through the leaf

Untitled Slide

• Carbon dioxide comes from the air
• It enters the plant through holes in the leaves called the stomata
• Water comes from the soil
• It diffuses into the plant through the root and travels up the stem via the xylem.
• Oxygen is the by product of this reaction.

VARIABLES

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• Anything that can change in an experiment is called a variable.
• The variable you change is called independant.
• The variable you measure is called dependant.
• The things that you must keep the same are called the control variables.

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