photosynthesis and respiration Flashcards
Explain the different requirements of an autotroph and a heterotroph
Autotroph – organism that can use an external energy source and
simple inorganic molecules to make complex organic molecules. The source of carbon is carbon dioxide. The energy source is light, although chemoautotrophs include the nitrifying bacteria. Heterotroph – and organism that needs to take in complex organic molecules ( such as carbohydrates, proteins and lipids) to act as a source of both energy and usable carbon compounds.
Describe the relationship between photosynthesis and respiration in living organisms
Photosynthesis provides the organic molecules for respiration which
oxidises the organic molecules releasing carbon dioxide. The energy flow is in one direction The carbon is recycled.
What range of wavelengths do you think chlorophylls reflect?
the green parts of the visible spectrum
what colour light to carotenoids reflect?
yellow/orange
Explain how the structure of the grana enables them to carry out their function.
Consists of stacks of thylakoid membranes which give a large surface area for ligt absorption
Explain how the structure of the stroma enables chloroplasts to carry out their functions.
Fluid filled stroma has enzymes for the Calvin cycle. It surrounds the grana so the products of the light dependent reaction can easily pass into the stroma. DNA has the genetic code to make some of the proteins needed for photosynthesis and there are ribsomes for assembly of these products
Name the two sets of reactions involved in photosynthesis, and state where in the
chloroplast each occurs.
Light –dependent reactions on the lamellae; light independent reaction
in the stroma
Explain why the very large surface area provided by the grana is important in
photosynthesis
The large surface area allows for more photosynthetic pigments, more
light absorption and more electron transfer.
List the products of the light –dependent reaction of photosynthesis.
ATP, reduced NADP and oxygen
State the role of accessory pigments in a photosystem.
They absorb a range of wavelengths of light and pass energy to the
primary pigment.
Describe the different roles of photosystem I and photosystem II.
Photosystem 2 is involved in non-cyclic photophosphorylation and takes part in photoionisation, photosystem 1 is involved in cyclic photophosphorylation and also takes part in photoionisation.
Distinguish between cyclic and non cyclic photophosphorylation
In cyclic photophosphorylation electrons return to the pigment from
which they were emitted. In non-cyclic photophosphorylation electrons pass elsewhere.
Outline the role of water in photosynthesis.
It is the source of hydrogen ions to be used in the light –independent stage to reduce GP
to TP. It is an electron donor and replaces the electrons lost by PSII when light excites chlorophyll molecules. It keeps palisade cells turgid, so the full vacuole s push the chloroplasts to the outer edges of the cells where they can more readily trap sunlight and carbon dioxide can diffuse into them
Explain how light causes stomata to open. What is the significance of this?
Light is trapped by photosystems (PSI) in the guard cells. AT is made. This actively transports potassium ions into the guard cells. This lowers the water potential of the guard cells and water enters then by osmosis, down a water potential gradient, from the surrounding epidermal cells. The guard cells swell and the tips, where cellulose in the walls is thinner and more flexible, bulge. This pushes guard cells apart from each other, opening the stoma between them.
Suggest why a lack of iron in soil can reduce growth in plants.
A lack of iron may mean fewer electron carriers (proteins with haem/iron) in the thylakoid membranes and reduced light –dependent reactions. This could lead to less reduced NADP and fewer molecules of ATP, which would reduce the light –dependent reactions. This in turn reduces yield of amino acids, so fewer proteins for growth or for enzymes needed for the light independent reactions.
State the advantage of using ATP as the universal energy currency.
It is efficient because using a single compound makes it easy to control
and coordinate different energy-requiring processes.
Distinguish between an energy currency molecule and an energy storage molecule.
Energy currency : the molecule that is the immediate source of energy
for reactions in the cell- ATP Energy storage: a large compact, insoluble energy rich molecule – amylose, glycogen or triglyceride.
Explain why ATP is known as the universal energy currency.
It releases energy in small manageable amounts for powering chemical reactions in cells
and it is found in all types of cells.
Explain why living organisms do not have very much NAD and CoA in their cells.
Because these molecules are recycled / regenerated.
Alcohol is metabolised in the liver. It is oxidised to ethanol by dehydrogenation, and then
to ethanoate (acetate). Suggest why people who drink large amounts of alcohol may be deficient in NAD.
As the alcohol is metabolised, it undergoes dehydrogenation – removal of hydrogen
atoms. The hydrogen atoms are combined with NAD, so there is less of it for respiration.
. Explain why NAD is called a nucleic acid/nucleotide derivative.
NAD contains ribose sugar (found in RNA), the nitrogenous base adenine and phosphate
groups. (ATP also contains adenine, ribose and phosphate groups.)
