Respiration and Photosynthesis Flashcards
Properties of ATP
- When hydrolysed, energy is released in small amounts
- Energy released in single-step reaction
- Soluble in water, where most chemical reactions occur
- Quickly broken down and resynthesised
Functions of ATP
- Active transport
- Synthesis reactions
- Muscle contraction
- Cell division
- Light independent reactions of photosynthesis
- First stage of glycolysis
Oxidation of amino acids
- Only used when all carbohydrate and lipid reserves have been used.
- Frst deaminated, and remaining keto acid can enter glycolysis or Krebs cycle, or be converted into a fatty acid which enters the Krebs cycle
What occurs to pyruvate during anaerobic respiration and why is this significant?
It is reduced using the NADH produced during glycolysis. Enabling regeneration of NAD for reuse.
Limitations of a respirometer
- Changes in T or atmospheric Pa can make gases expand or contract.
- These affect the distance the fluid moves, so measured distance isnt just affected by O2 volume.
- Chemicals used might alter composition of gases in the chamber.
- Volume change calculated using the diameter of the tube may be inaccurate.
Photosynthesis
Autotrophic nutrition. Production of organic compounds, e.g. carbohydrates and lipids from the inorganic compounds CO2 and H2O using light energy.
Product of light dependent reaction
- ATP
- NADPH plus H+ (H from photolysis of H2O
- Oxygen
Uses of NADPH and ATP in light independent reaction
- Hydrogen from NADPH reduces GP forming TP
- ATP used as energy source for further synthesis reactions
Products of non-cyclic phosphorylation
ATP, NADPH plus H+ and oxygen
Products of cyclic phosphorylation
ATP
What occurs to CO2 in calvin cycle?
It combines with RuBP in a reaction catalysed by Rubisco to form 2 GP.
What occurs to GP in calvin cycle?
Reduced using NADPH to form TP, with energy supplied by ATP.
What is TP used for in plants?
- Forms all photosynthetic products e.g. glucose, fatty acids, glycerol, amino acids
- Regenerates RuBP
Action spectrum
Graph showing the effectiveness of different wavelengths of light in stimulating the process being investigated.
Absorption spectrum
Graph of the relative amounts of light absorbed at different wavelengths for a pigment.
What is the metabolic advantage of C4 plants to C3 plants?
- Not inhibited by oxygen
- CO2 acceptor, PEP has v high CO2 affinity, even in low concentrations
What happens to CO2 in C4 plants?
1) CO2 is fixed in mesophyll cell then shuttled to bundle sheath cells for conventional C3 fixation
2) Carbon is shuttled as a 4C acid which releases CO2 and is fixed by RuBP.
3) Resulting 3C compound is shuttled back to mesophyll cells for conversion into PEP
Adaptations of halophytes
- High transpiration rates & low water potential in root cells, greater water potential gradient
- Extensive root network providing anchorage and a large surface area for water and iron uptake
- Smaller plants able to store water when available
- Able to regulate salt content by excreting salt from glands at the margins of their leaves
Adaptations of xerophytes
- A thickened waxy cuticle
- Reduced surface area of leaves.
- Curled leaves
- Hairs on leaf surface
- Stomata in ‘epidermal pits’ beneath leaf surface
- Extensive shallow root network and deep tap root
How does a thickened waxy cuticle help prevent water loss?
Provides long diffusion pathway, reducing the rate of evaporation
How do curled leaves help prevent water loss?
Reduces surface area for evaporation and increases humidity in air around stomata reducing transpiration.
How do hairs on the leaf surface prevent water loss?
Trap layer of air, which becomes saturated with water vapour reducing water potential gradient for water loss.
How does the location of stomata in epidermal pits help reduce water loss?
Reduce exposure to air currents which become saturated with water vapour & reduce the water potential gradient for evaporation.
How does and extensive shallow root network and deep tap root help prevent water loss?
Maximises water uptake from just below the surface and from well below the sand level
Adaptations of mesophytes
Presence of waxy cuticle, protected stomata (w/ regulatory diameters), variable leaf shape & abscission.
Adaptations of hydrophytes
Cells become turgid & a point is reached where water potentials of surrounding water & plant cells are equal & there is no further net movement of water into cells.
Adaptations of the xylem
- Tissue is dead, no cell contents, leaving hollow tubes so there is minimal resistance to flow of water & ions.
- Cell walls strengthened by lignin; making them more rigid providing support & impermeable to water.
- No cross-walls in xylem vessels allowing free flow. In tracheids the end walls have partially broken down.
- Bordered pits present allowing water and solutes to move laterally to adjacent vessels
How does the endodermis control entry of substances into the xylem?
Casparian strip (made of suberin) is impermeable to water and ions, meaning they cannot pass through the apoplast pathway, only the symplast.
How is root pressure produced?
- Active transport of ions into the xylem;
- By the endodermis;
- Lowers the water potential of the xylem;
- Water moves into the xylem by osmosis;
- Produces a positive hydrostatic pressure
Explain how standard deviation helps in the interpretation of data
- Shows spread of the data
- Overlap = not significant;
- Low SD means results more reliable / repeatable
Why is petroleum used as a control when measuring efficiency of biofuels
- Is widely/commonly used;
- Provides a standard amount of CO2 produced;
- Produces large amount of carbon dioxide;
- Could be replaced by biofuel
Advantage of systemic herbicide over contact herbicide
- Absorbed / transported through tissues of plant
- Kills whole plant
- Less affected by light / rain
Appropriate units for measuring energy transfer in a pyramid of energy
kJ m-2 yr-1
Describe and explain how the stability of a community is related to the number of species it contains
- High stability with greater number of species
- More species linked to more food chains
- If one species dies others available as food
Light independent reaction
- CO2 combines with RuBP, Catalysed by RUBISCO;
- Produce two molecules of GP, reduced to TP using NADPH and energy from ATP
- TP used to form glucose and resynthesize RuBP;
