Photosynthesis & Respiration

1. Chlorophyll molecule absorbs light energy, raising the energy of electrons until they leave the chlorophyll molecule

2. The electrons are then taken up by a molecule called an electron carrier

3. The electrons are passed along a number of electron carriers, the electron transfer chain

4. At each of these transfers, the electron loses some energy, some of this energy is used to combine a phosphate molecule with an ADP molecule to make ATP

1. Carbon dioxide from the atmosphere diffuses into the leaf through stomata and dissolves in water, it then diffuses through the cell surface membrane, cytoplasm and chloroplast membranes into the stroma of the chloroplast.

2. Carbon dioxide reacts with RuBP, this reaction is catalysed by the enzyme RUBISCO

3. The reaction between CO2 and RuBP produces two molecules of GP (3 carbon molecule).

4. Reduced NADP and ATP from the light dependent reaction are used to reduce GP to TP using the ATP

5. NADP is reformed and goes back to the light-dependent reaction

6. Some TP molecules are converted into organic substances such as glucose, starch, lipids and amino acids.

7. Most TP molecules are used to reform RuBP using ATP from the light dependent reaction

1. Phosphorylation of glucose to glucose phosphate. Glucose is made more reactive by the addition of two phosphate molecules. The phosphate comes from the hydrolysis of ATP which provides energy to activate glucose.

2. Splitting of the phosphorylated glucose. Each glucose molecule is split into two 3 carbon molecules known as triose phosphate (TP)

3. Oxidation of triose phosphate. Hydrogen is removed from the TP molecules and transferred to NAD to form reduced NAD

4. The production of ATP. Enzyme-controlled reactions convert the TP into pyruvate, in the process two ATP molecules are generated.

1. Pyruvate is oxidised to acetate, the pyruvate loses a CO2 molecules and two hydrogens. The hydrogens join with NAD to form reduced NAD.

2. The acetate combined with a molecules called coenzyme A to produce acetylcoenzyme A.

pyruvate + NAD + CoA = acetyl CoA + reduced NAD + CO2

1. The actyl CoA combines with a 4-carbon molecule to create a 6-carbon molecule

2. In a series of reactions this 6-carbon molecule loses CO2 and hydrogen to give a 4-carbon molecule and a single molecule of ATP

3. The cycle now repeats with a new molecule of acetyl CoA

1. The hydrogen atoms produced in previous stages combine with NAD and FAD.

2. The reduced NAD & FAD donate electrons of the hydrogen to the first molecule of the transfer chain

3. The electrons pass along a chain of electron carrier molecules in a series of oxidation-reduction reactions. As they move the energy they release causes the active transport of protons across the inner mitochondrial membrane and into the inter-membrane space

4. The protons accumulate in the inter-membranal space before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane

5. At the end of the chain the electrons combine with protons and oxygen to form water. Oxygen is the final acceptor of electrons in the electron transfer chain.

In plants and some microorganisms: pyruvate + reduced NAD = ethanol + carbon dioxide + NAD

In animals: pyruvate + reduced NAD = lactate + NAD