M5 - Photosynthesis and Respiration Flashcards
Photosynthesis involves a number of _______ that absorb _____ energy.
Only chlorophyll participates directly in photosynthesis. It mainly absorbs ____ and ____ light. It reflects ____ light.
________ pigments can absorb wavelengths of light that chlorophyll cannot.
pigments
light
red and blue
green
Accessory Pigments
What do accessory pigments do?
What may shade tolerant plants also contain?
They pass light energy (photons) to chlorphyll a, broadening the spectrum that allow photosynthesis to take place.
Shade tolerant plants may also contain ANTHOCYANINS (red or purple pigments) thought to protect chloroplasts from brief exposure to high light levels.
What is the link between photosynthesis and respiration?
PHOTOSYNTHESIS provides the O2 and carbohydrates, proteins and fats either directly or indirectly for cellular respiration.
Waste products of cellular respiration (CO2 + H2O) are used by chloroplasts as raw materials for photosynthesis.
Chemical elements to life are recycled but energy is not - it flows into an ecosystem as sunlight and back out as heat.
What is chlorophyll ionisation?
Light energy excites electrons which are released, leaving +ve ions.
Describe the process of the light-dependent reaction of photosynthesis.
Chlorophyll molecules in the thylakoid membranes absorb light energy and become excited.
- Excited electrons are emitted from the chlorophyll molecule, which becomes photoionised.
Describe the process of Non-cyclic Photophosphorylation.
1) Photolysis
2) Electrons in PS II are excited and are transferred along a chain of electron carriers to PS I (to replace emitted excited electrons).
3) As electrons are carried along the electron transport chain energy is lost and is used to pump H+ across the thylakoid membrane.
4) H+ ions diffuse down a concentration gradient back across the membrane through ATP synthase, synthesising ATP (chemiosmosis).
5) Excited electrons from PS I are accepted by an electron carrier and transferred to NADP. H+ from water are also transferred to NADP - forming reduced NADP (NADPH).
What is chemiosmosis?
The flow of H+ ions down a conc gradient through ATP synthase forming ATP from ADP + Pi.
What is photolysis?
The splitting of water using light energy.
- Electrons from water molecules replace those lost from PS II.
- H+ ions and O2 gas released (O2 diffused through membrane because small).
Describe photosystems.
They contain pigments arranged in a funnel-shaped light harvesting cluster.
Pigments are held in place by proteins in the membrane.
Accessory pigments absorb photons of light and transfer the energy to the primary pigment (Chlorophyll a) - also known as the reaction centre.
There are two main photosystems: PS II and PS I.
Describe Cyclic photophosphorylation
- Only PSI involved.
- The electrons emitted from PSI are passed to a higher energy level where they are received by a second electron acceptor.
- Electrons then pass along a chain of electron carriers and return to PSI.
- This releases energy to form ATP.
- No reduced NADPH is made in this process.
(Refer to notes on Z-scheme - do not need to know, but need to understand).
What does the Calvin cycle do? Where does it occur? What does it require?
Metabolic pathway - reducing CO2 to carbohydrates (gaining H).
Occurs in the stroma of chloroplast.
Required ATP and NADPH from the light dependent reactions.
Describe the steps involved in the Calvin Cycle (one cycle).
Rubisco fixes CO2 and combines it with Ribulose Bisphosphate (RuBP) 5C to form 2 x Glycerate-3-phosphate (GP). 2x3C
GP is reduced to form 2 x Triose phosphate (TP) 2x3C and converting ATP –> ADP + Pi and NADPH –> NADP.
1/6 of C of TP goes to form organic molecules (e.g. glucose - 6 turns of the cycle needed)
5/6 of C of TP goes on to regenerate ribulose bisphosphate using ATP.
How many Calvin cycle turns are required to from 1 glucose molecule?
6 turns
What organic molecules can be produced from Triose Phosphate?
Monosaccharides, Disaccharides, Polysaccharides
Lipids, Proteins
What are the 3 main limiting factors of photosynthesis?
- Light intensity
- Temperature
- CO2 Concentration
Describe the effect of increased CO2 concentration.
As CO2 conc increases, rate of photosynthesis increases.
Because… increased rate of L-I reactions providing no other factor is limiting (e.g. low light causing stomata to close).
CO2 is limiting factor initially and then other factors become limiting factor when graph plateaus.
How do you record the rate of respiration for mammels? (experiment)
Test tube containging woodlice on a gauze - immersed in a water bath to provide optimum temperature. Bottom of test tube filled with KOH solution. Test tube attached to a syringe and a capillary tube filled with coloured fluid with a scale.
Control tube set up containing glass beads instead of woodlice.
Woodlice respire - releasing CO2, which is absorbed by the KOH. O2 is consumed so volume of air decreases, reducing pressure in test tube causing the coloured fluid in capilalry tube to move.
Readings taken over a set period of time. Repeated and a mean volume of O2 is calculated.
How do you test rate of respiration for yeast? (experiment)
AEROBIC
- Test tube with buffer and substrate solution (e.g. glucose) connected to a gas syringe and placed in a water bath. Add yeast culture and set syringe to zero.
- As yeast respire, CO2 released and travels up into syringe.
- Measure CO2 volume at set time intervals. Repeat and calculate mean.
- Control experiment should also be set up with no yeast.
ANAEROBIC
- Same as above, just add a little liquid parafin so it settles on and completely covers surface of solution. This will stop O2 getting in,
Note: could also bubble through lime water and count bubbles
