3.5.1 Photosynthesis Flashcards
1
Q
4 features of oxidation
A
- loss of electrons
- addition of oxygen
- loss of hydrogen atom
- releases energy
2
Q
4 features of reduction
A
- gain of electrons
- removal of oxygen
- gain of hydrogen atom
- takes in energy
3
Q
What are coenzymes?
A
- organic molecules that bind temporarily to the enzyme
- they transfer a chemical group needed for the reaction and ‘help’ the enzyme
- eg NAD, NADP, FAD, co-enzyme A, vitamin c
4
Q
Describe photosystems
A
- embedded in thylakoid membranes
- contain light absorbing pigments (eg chlorophylls, carotenoids, xynthophylls)
- 2 photosystems (II before I). Both have chlorophyll at their centers
5
Q
Where does the light dependent stage of photosynthesis occur?
Where does the light independent stage occur?
A
- Thylakoid membranes of chloroplasts
- stroma of chloroplasts
6
Q
Overview of light dependent reaction
A
- Uses light energy
- to produce ATP, reduced NADP and O2
7
Q
Overview of light independent reaction
A
- uses ATP and reduced NADP from LDR to produce glucose
8
Q
Full answer: light independent stage of photosynthesis
A
- light independent reaction/Calvin cycle occurs in the stroma of chloroplasts
- carbon dioxide combines with RuBP (ribulose bisphosphate)
- produces 2 molecules of GP (glycerate 3-phosphate) using Rubisco enzyme
- reduced to triose phosphate
- using reduced NADP
- using energy from ATP
- triose phosphate converted to other organic substance glucose / RuBP
- RuBP reformed using energy and pi from ATP
9
Q
Full answer: light dependent stage of photosynthesis
A
- occurs in thylakoid membrane of chloroplasts
- chlorophyll absorbs light energy
- excites a pair of electrons from chlorophyll, chlorophyll is photoionsed, chlorophyll is oxidised
- the electrons LOST from chlorophyll move along electron transport chain in a series of redox reactions and energy they release is used to pump protons into thylakoid lumen
- as protons move back into stroma down electrochemical gradient, energy released is used to join ADP and Pi to form ATP by ATP synthase (chemiosmosis)
- photolysis of water produces protons, electrons and oxygen
- NADP reduced by electrons/hydrogen atom
10
Q
Limiting factor graphs: light intensity
A
- as light intensity increased, rate of photosynthesis increased
- because light is a limiting factor its needed in the light dependent reaction to excite a pair of electrons from chlorophyll
- until … when, as light intensity increases further there is no further increase in rate of photosynthesis- plateau
- because light is no longer limiting- saturation point
- another factor is limiting eg carbon dioxide concentration, temperature
11
Q
Limiting factor graphs: carbon dioxide concentration
A
- as carbon dioxide concentration increases, rate of photosynthesis increases
- because CO2 is a limiting factor its needed in the light independent reaction to combine with RuBP using Rubisco to eventually produce glucose
- until … when, as CO2 increases further there is no further increase in rate of photosynthesis- plateau
- because CO2 is no longer limiting- saturation point
- another factor is limiting eg temperature, light intensity
12
Q
Limiting factor graphs: temperature
A
- as light intensity increases, rate of photosynthesis increases
- because light is a limiting factor its needed in more kinetic energy, more collisions, more enzyme substrate-complexes
- until peak at … when, as temp increases further rate of photosynthesis decreases
- because enzymes used in light independent reaction are denatured
13
Q
What is the compensation point?
A
- rate of photosynthesis = rate of respiration
- no net gas exchange
14
Q
What is the difference between primary and accessory pigments?
A
- primary pigments act as reaction centres/where electrons are excited
- accessory pigments surround the reaction centre
- transfer energy to primary pigments
15
Q
What is photophosphorylation?
A
Production of ATP from ADP and Pi
