3.5 Energy transfers in and between organisms (A-level only) Flashcards
(26 cards)
photosynthesis
structures in the chloroplast
- thylakoid membranes
-stroma
-inner and outer membranes
thylakoid membranes
Folded membranes which contain photosynthetic proteins (chlorophyll) and electron carrier proteins are embedded within these membranes which are both involved in LDR
Stroma
Fluid centre which contains enzymes involved in the LIR
inner and outer membranes
control what can enter and leave the organelle
where does the light dependant reaction occur?
thylakoid membrane
what is the light dependant reaction?
and water are used lo create AT and reduced NADP Which are needed
ind water are used to create ATP and reduced for the light-independent stage
what are the 4 key stages of the light dependant reaction?
This occurs in four key stages:
1. Photolysis
2. Photoionisation of chlorophyll
3.Chemiosmosis
4.Production of ATP and reduced NADP
Photolysis of water
Light energy is absorbed by chlorophyll and splits water into oxygen, H+ and e-.
H₂0 → ½0₂ + 2e⁻ + 2H+
The H+ is picked up by NADP to form NADPH and is used in the LIR.
The e- are passed along a chain of electron carrier proteins.
The oxygen is either used for respiration or diffuses out of the leaf through the stomata
photoionisation of chlorophyll
Light energy is absorbed by the chlorophyll
and the energy results in
electrons becoming excited and raising up an energy level to leave chlorophyll.
Therefore the chlorophyll has been ionised by light.
Some of the energy from the released electrons is used to make ATP and reduced NADP in chemiosmosis
Chemiosmosis
-As electrons move along they release energy and some of the energy from electrons is used to pump the protons across chloroplast membranes
-An electrochemical gradient is created.
The protons pass through the enzyme ATP synthase, which results in the production of ATP
-The protons combine with the co-enzyme NADP to become reduced NADP
Because the protons move from a high to low concentration gradient this is known as chemiosmosis
light independent reaction
the light independent reaction is a cycle (Calvin cycle)
Calvins experiment method
1.Isolation of Chloroplasts
2. Incorporation of Carbon-14
3. Perfusion of the Chloroplasts
4. Measurement of radioactivity
5. Analysis of the data
where does the light independent reaction occur
The Calvin cycle occurs in the stroma, and this fluid contains the enzyme RuBisCo which catalyses this reaction. This stage is temperature sensitive due to the fact it involves enzymes.
what does the light independent reaction use
-The Calvin cycle uses carbon dioxide, reduced NADP and ATP to form hexose sugar
-The ATP is hydrolysed to provide energy for this reaction and the reduced NADP donates the hydrogen to reduce molecules GP in the cycle
Calvin Cycle
-Carbon dioxide reacts with ribulose bisphosphate (RuBP) to form two molecules of glycerate 3-phosphate (GP) a 3 carbon compound. This reaction is catalysed by the enzyme Rubisco.
-GP is reduced to triose phosphate (TP) using energy from ATP and by accepting a H from reduced NADP
-Some of the carbon from TP leaves the cycle each turn to be converted into useful organic substances
-The rest of the molecule is used to regenerate RuBP, with the energy from ATP.
-Whilst glucose is the product, this monosaccharide can join to form disaccharides such as sucrose, and polysaccharides such as cellulose and starch. It can also be converted into glycerol and therefore combine with fatty acids to make lipids for the plant
limiting factors
-Any factor that reduces the rate of photosynthesis is called a limiting factor
-These could be temperature, carbon dioxide concentration, or light intensity
Calvins experiment
The equipment were used to measure the incorporation of carbon-14 isotope into the carbohydrate molecules, trace the movement of carbon through the Calvin cycle, and visualise the distribution of radioactivity in the plant material
respiration
stages in aerobic respiration
-glycolysis
-link reaction
-Krebs cycle
-oxidative phosphorylation
what is the purpose of respiration
to make ATP
where does glycolysis occur?
cytoplasm and it is an anaerobic process
what are the 3 steps to glycolysis?
- Phosphorylating glucose to glucose phosphate, using ATP
- The production of triose phosphate
- Oxidation of triose phosphate to produce pyruvate with a net gain of ATP and reduced NAD.
glycolysis flow chart
-glucose is phosphorylated by adding ATP
-triose phosphate is oxidised to form pyruvate
-pyruvate is actively transported into the mitochondria for the link reaction
