Unit 5 Respiration & Photosynthesis Flashcards
Describe the structure of a chloroplast in terms of photosynthesis.
THYLAKOID OF CHLOROPLAST
- Folded membranes which contain chlorophyll
- Electron carrier proteins embedded in these involved in the Light-dependent reaction
STROMA OF CHLOROPLAST
- Fluid centre which contains enzymes involved in Light independent reaction
INNER & OUTER MEMBRANE CONTROLS WHAT CAN ENTER AND LEAVE CELL
What happens to products of the photolysis of water?
H₂O → ½O₂ + 2e- + 2H+
H+ = used to reduce coenzyme NADP
E- = replace electrons lost from chlorophyll
O₂ = used for respiration or diffuses out of the leaf as
waste gas.
Describe the first 2 key stages of the light-dependent reaction
(THYLAKOID MEMBRANES)
PHOTOLOYSIS
1. Chlorophyll absorbs light energy and splits water into Oxygen, H+ and electrons
PHOTOIONISATION OF CHLOROPHYLL
2. Light energy absorbed by chlorophyll results in excited electrons in chlorophyll therefore the electrons are lost
((3. Some of the energy from electrons released during photoionisation is conserved in the production of ATP and reduced NADP in chemiosmosis))
Describe the 3rd key stage of the light-dependent reaction
CHEMIOSMOSIS
4. Electrons released from chlorophyll move down a series of carrier proteins embedded in the thylakoid membrane called the electron transfer chain
5. Some energy is released from the ETC and is coupled to the active transport of H+ ions (protons) from the stroma into the thylakoid space.
Describe the 4th key stage of the light-dependent reaction.
PRODUCTION OF ATP AND REDUCED NADP
6. Creates electrochemical gradient so H+ ions move from thylakoid to stroma via channel protein ATP Synthase which catalyses
ADP + Pi → ATP and consequently NADP forms reduced NADP from combination of H+ and electrons in stroma
Describe what is meant by the light-independent reaction (CALVIN’S CYCLE)?
NO LIGHT ENERGY REQUIRED
- Uses reduced NADP from the LDR to form a simple sugar.
- ATP produced from hydrolysis in LDR provides the additional
energy for this reaction.
Describe the first 2 stages of the light-independent reaction.
- CO₂ reacts with ribulose bisphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate (GP) OOO OOO, reaction is catalysed by the enzyme rubisco
- ATP and reduced NADP from the light-dependent reaction used to reduce GP as accepts H+ from reduced NADP(becomes oxidised) to 2x triose phosphate (TP) OOO OOO
Describe the last 2 stages of the light-independent reaction.
- 1C leaves the cycle to be converted into useful organic substances
- Rest of TP (5 carbons) is used to regenerate RuBP using ATP and forms ADP
6x till glucose formed
- sugars used for respiration
- so plants have more energy for growth
Describe 3 factors that can limit the rate of photosynthesis.
- Light intensity up to a certain point as used in the light-dependent reaction
- CO₂ up to a certain point as used in the light-independent reaction
- Temperature as enzyme-substrate complexes need to be formed from successful collisions however enzymes denature after temperature too high
Outline some common agricultural practices used to
overcome the effect of limiting factors in photosynthesis.
- Artificial light, especially at night.
- Artificial heating maybe through burning fuels (CO₂ as well)
- Addition of CO₂
- Costs and benefits need to be analysed
Describe the 4 key stages of respiration and where they occur.
DEFINITION
Respiration produces ATP.
1. Glycolysis (cytoplasm)
2. Link reaction (mitochondrial matrix)
3. Krebs cycle (mitochondrial matrix)
4. Oxidative phosphorylation (mitochondrial inner membrane of cristae)
Describe the first stage of respiration
GLYCOLYSIS
FIRST STAGE OF AEROBIC AND ANAEROBIC RESPIRATION
1. Phosphorylation of glucose to glucose phosphate, using 2x ATP
2. Splits into 2x triose phosphate
3. Oxidation of triose phosphate to 2x pyruvate with a net gain of
2x ATP and 2x reduced NAD.
Describe the second stage of aerobic respiration
LINK REACTION
- Pyruvate from glycolysis enters the mitochondrial matrix by active transport.
- Pyruvate is oxidised to acetate, producing reduced NAD in
the process + CO₂
- Acetate combines with coenzyme A in the link reaction to
produce acetyl coenzyme A
2x Acetyl CoA
2x CO₂
2x Reduced NAD
Describe the third stage of aerobic respiration.
KREBS CYCLE
- Acetyl coenzyme A reacts with a four-carbon molecule, releasing coenzyme A & producing a six-carbon molecule that enters the Krebs cycle
- series of oxidation-reduction reactions occurrs, the Krebs cycle
generates reduced coenzymes and ATP by substrate-level
phosphorylation and carbon dioxide is lost through decarboxylation
PRODUCTS PER CYCLE:/ per glucose is double
3x reduced NAD
1x Reduced FAD
1x ATP
2x CO₂
Describe the fourth stage of aerobic respiration.
(1)
OXIDATIVE PHOSPHORYLATION
- All the reduced coenzymes release their protons (H+) and electrons (e-).
- Electrons are passed down a series of electron carrier proteins (ETC) and the small amount of energy released coupled to the active transport of H+ ions (protons) from mitochondrial matrix into the intermembrane space by active transport.
Describe the fourth stage of aerobic respiration.
(2)
- Creates an electrochemical gradient so the protons (H+) move down from intermembrane space back into the matrix via channel protein ATP Synthase which catalyses
ADP + Pi → ATP(Chemeosmosis) - Oxygen acts as the final electron acceptor and combines with the electrons and the protons to form water
- 34 ATP
