My topic 5

• What is photosynthesis?

  Occurs ONLY in plants. The plant makes glucose from light, carbon dioxide and water
• What is the equation for photosynthesis?

  6CO2 + 6H2O -> C6H12O6 + 6O2
• How is energy stored in plants?

  In the glucose until plants release it by respiration
• What is a metabolic pathway?


  A series of reactions that are catalyzed by different enzymes and result in one or more products - photosynthesis
• What is aerobic respiration?

  Respiration with oxygen
• What is anaerobic respiration?

  Respiration without oxygen
• What is respiration?

  The release of energy from glucose
• What is the chemical equation for aerobic respiration?

  C6H12 + 6O2 > 6CO2 + 6H2O + energy
• What does anaerobic respiration produce in plants and yeast?

  Ethanol, carbon dioxide and releases energy
• What does anaerobic respiration produce in humans?

  Lactate and releases energy
• What is ATP?

  Adenosine Triphosphate - immediate source of energy in a cell
• In respiration, the energy released from glucose is used to make.....

  ATP
• Describe the structure of ATP

  Adenine base, combined with ribose sugar and three phosphate groups
• how is ATP synthesized?

  Via a condensation reaction between ADP (adenosine diohosphate) + P ( inorganic phosphate) using energy from an energy releasing reaction eg the breakdown of glucose in respiration
• Where is energy stored in ATP?

  In the phosphate bond
• What enzyme catalyses the synthesis of atp?

  ATP synthase
• What is phosphorylation?

  Addition of a phosphate group
• How does ATP release energy in a cell?

  Diffuses to part of cell that needs energy, here it is broken down back into ADP+P by hydrolysis- chemical energy is then released from the phosphate bond that was broken
• What enzyme catalyses the breakdown of ATP

  ATP hydrolase
• 6 ATP properties that make it so useful


  1. Stores or releases only small manageable amount

  2. Small soluble so easily transported

  3. Easily broken down

  4. Quickly remade

  5. Can make other molecules more reactive by transferring phosphate group

  6. Can't pass out of cell
• What is the compensation point for light intensity?

  When there is a particular level of light intensity at which the rate of photosynthesis exactly matches the rate of respiration
• How do you work out the compensation point in plants?

  Measure the rate at which oxygen is used at different light intensities - photosynthesis produces oxygen and respiration uses it so the compensation point is the light intensity at which oxygen is being used as quickly as it's produced
• Where does photosynthesis take place?

  Chloroplast
• Chloroplasts are small flattened organelles surrounded by a double membrane. ..........1........... are stacked into structures called ................. which are linked tighter by bits of .........1...... membrane called .................

  Thylakoids

  Grana

  Lamellae
• What are photosynthetic pigments?

  Coloured substances that absorb light energy needed for photosynthesis
• Photosynthetic pigments are found in the ................. ..................... and they're attached to ................... . This is called a .........................

  Thylakoid membrane

  Proteins

  Photosystem
• What are the two photoSystems?

  Photosystem 1 - absorbs light best at wavelength of 700nm

  Photosystem 2 - absorbs light best at 680nm
• Describe stroma

  Gel like substance contained within the inner membrane of a chloroplast and surrounding the thylakoids , contains enzymes, sugars and organic acids
• Carbohydrates produced by photosynthesis and not used straight away are stored as............

  Starch grains in the stroma
• What are redox reactions?

  Oxidation-reduction reactions. Electrons are transferred from one molecule to another
• If something is reduced It has .................. electrons and may have gained hydrogen or lost ................

  Gained

  Oxygen
• If something is oxidised it has .............. electrons and may have lost hydrogen or .............. oxygen

  Lost

  Gained
• Oxidation on one molecule always involves ................. of another molecule

  Reduction
• What is a coenzyme?

  AIDS the function of an enzyme- work by transferring a chemical group from one molecule to another
• What is NADP and what does it do?

  A coenzyme used in photosynthesis - transfers hydrogen from one molecule to another ( it can reduce or oxidise a molecule)
• What are the 2 stages that make up photosynthesis?

  The light dependent reaction

  The light independent reaction ( the Calvin cycle)
• the light dependent reaction needs ............... it takes place in the ................ .............. of the chloroplasts. Light energy is absorbed by ..................... in the photoSystems. The light energy excites the ................... in the chlorophyll giving them more energy which eventually causes them to be ............... from the chlorophyll molecule. This process is called ............................

  Light

  Thylakoid membrane

  Chlorophyll

  Electrons

  Released

  Photo ionisation
• After photoionisation in the light dependent reaction, the chlorophyll molecule is now a ........................ charged ion. Some of the energy released from electrons is used to add a ........................... to adp to form atp and some is used to .............. NADP to form ............ NADP. ATP transfers .............. and NADP transfers ................. to the light independent reaction.

  Positively

  Phosphate group

  Reduce

  Reduced

  Energy

  Hydrogen
• Briefly describe the light independent reaction ( Calvin cycle)

  Doesn't use light energy directly but uses the products of the light dependent reaction, takes place in the stroma of the chloroplast . The atp and reduced NADP supply the energy and hydrogen to make glucose from co2
• What are electron carriers?

  Proteins that transfer electrons