Photosynthesis Flashcards
Name the 5 layers that make up a leaf and state which layers contains the greatest proportion of chloroplast and which contain stomatal pores
- Waxy Cuticle
- Upper Epidermis
- Upper Mesophyll (Contains most Chloroplast)
- Lower Mesophyll
- Lower Epidermis (Contain stomatal pores)
Which two molecules are the feedstock reactants of photosythesis?
Carbon Dioxide & Water
Which 2 molecules are the product of photosynthesis?
Glucose & Oxygen
In which part of the chloroplast does each following reaction occur?
a) light-dependant reaction
b) light-independent reaction
a) Grana/Thylakoids
b) Stroma
What are the products of the light-dependant reaction?
Reduced NADP
ATP
Oxygen
What are the products of the light-independent reaction?
sugars and other organic molecules
Name and explain some adaptations of the leaf to maximise photosynthesis
- Large surface area too collect as much sunlight as possible
- Arrangement of leaves to minimise overlapping (avoiding shadowing)
- Thin leaves, so diffusion pathway is kept short
- Transparent cuticle and epidermis to allow light to cells beneath
- Numerous stomata for gaseous exchange
- A network of xylem to bring water to the leaf, and phloem to remove sugars produced by photosynthesis
Describe the use of the light energy captured by the chlorophyll pigment during the light-dependant reaction
- To add an inorganic phosphate molecule to ADP to make ATP
- For photolysis for the splitting of water into H+ ions, gaseous Oxygen and electrons
Give a balanced equation for the photolysis of water
2H2O –> 4H+ + 4e- + O2
Describe the ETC (Electron Transport Chain) and explain how this produces ATP and NADPH
The chlorophyl molecule is Oxidised. The lost electron is transferred along a series of electron carriers in the chloroplast membrane, decreasing in energy levels as they do so. This energy is used to phosphorylate ADP molecules into ATP.
The final electron acceptor is NADP which gains the electron from the chlorophyll pigment as well as Hydrogen ions from photolysis to be reduced, becoming NADPH (or Reduced NADP).
Describe the Calvin Cycle starting from when Carbon Dioxide reacts with RuBP (Ribuslose Biphosphate)
Carbon Dioxide is fixed to RuBP (a 5 Carbon molecule) by an enzyme to form 2 GP (Glycerate 3-phosphate) molecules (each with 3-Carbon atoms). The GP is reduced by the hydrolysis of ATP and the oxidation of NADPH to NADP, to form 2 molecules of TP (Triose Phosphate). These TP molecules are either converted to useful organic molecules (glucose) or reduced further by the hydrolysis ATP, to form RuBP.
Give examples about how the stroma of the chloroplast is adapted to aid photosynthesis.
- The fluid of the stroma contains all necessary enzymes for the light-independent reaction (the reduction of Carbo Dioxide)
- The stroma fluid surrounds the grana so products of the light-dependant reaction have a short diffusion pathway
- The stroma contains both DNA and ribosomes so it can quickly manufacture proteins needed for the light-independent reaction
Although light is not required for the Calvin Cycle to take place, explain why the Calvin Cycle cannot take place for long in the absence of light
The Calvin cycle requires ATP and NADPH in order to operate. Both are the products of the light-dependent reaction, which needs light. No light means no more ATP or NADPH are produced, thus the Calvin cycle cannot continue once any ATP or NADPH already produced have been used up.
Describe and explain two ways in which the rate of photosynthesis could be measured experimentally
1) - Measuring the volume of Oxygen released by the plant, since Oxygen is a product of photosynthesis
2) - Measuring the volume of Carbon Dioxide taken up by the plant since Carbon Dioxide is used in the light-independent stage of photosynthesis
Describe an explain the effect of light intensity on the rate of photosynthesis
An increase in light intensity will cause a proportional increase in the rate of photosynthesis. This is because the increased light intensity will oxidise more chlorophyll pigments more rapidly.
The change in rate of photosynthesis will decrease further on due to Carbon Dioxide concentration temperature becoming a limiting factor.
