module 5; energy transfers in & between organisms Flashcards
describe the structure of chloroplast
outer membrane
inter-membrane space
inner membrane
stroma (aqueous fluid)
granum (stack of thylakoid)
thylakoid
lamella
lumen (inside of thylakoid)
state the structure & function of thylakoid membranes
structure: folded membranes which contain photosynthetic proteins (chlorophyll) & e- carrier proteins are embedded within these membranes
function: involved in light-dependent reactions (LDR)
state the structure & function of the stroma
structure: fluid centre which contains enzymes
function: involved in the light-independent reaction (LIR)
state the function of the inner & outer membranes
they control what can enter & leave the organelle
state the stages of photosynthesis
- light-dependent reaction
- light-independent reaction
where do the stages of photosynthesis occur?
both the LDR & LIR occur in the chloroplast of a plant cell but in different locations - LDR occurs on the thylakoid membranes/grana & LIR occurs in the stroma
what is the LDR?
the LDR is the 1st stage of photosynthesis & it requires light - light energy & water are used to create ATP & reduced NADP which are needed for the light-independent stage
state the stages of the LDR
- photolysis
- photoionisation of chlorophyll
- chemiosmosis
- production of ATP & reduced NADP
name & explain what happens in the 1st stage of LDR
photolysis of water:
light energy is absorbed by chlorophyll & splits water into oxygen, H⁺ & e-
the H⁺ is picked up by NADP to form NADPH & is used in the LIR
the e- are passed along a chain of e- carrier proteins
the oxygen is either used for respiration or diffuses out of the leaf through the stomata
name & explain what happens in the 2nd stage of LDR
photoionisation of chlorophyll:
light energy is absorbed by the chlorophyll & the energy results in e- becoming excited & raising an energy level to leave chlorophyll (chlorophyll has been ionised by light)
some of the energy from the released e- is used to make ATP & reduced NADP in chemiosmosis
name & explain what happens in the 3rd stage of LDR
chemiosmosis:
the e- that gained energy & left the chlorophyll to move along a series of proteins embedded within the thylakoid membrane
as they move along they release energy & some of the energy from electrons is used to pump the protons across chloroplast membranes
an electrochemical gradient is created
the protons pass enzyme ATP synthase - results in production of ATP
the protons combine with the co-enzyme NADP to become reduced NADP
as protons move from a high to low conc gradient this is known as chemiosmosis
what is LIR?
LIR is a cycle (the calvin cycle)
where does the calvin cycle occur?
occurs in the stroma as its fluid contains the enzyme RuBisCo which catalyses the reaction - this stage temp sensitive as it involves enzymes
what does the calvin cycle form?
hexose sugars
how does the calvin cycle form hexose sugars?
it uses CO₂, reduced NADP & ATP
why are the reactants in the calvin cycle important for the LIR?
the ATP is hydrolysed to provide energy for this reaction & the reduced NADP donates the H to reduce molecules GP in the cycle
explain the process of the LIR
- CO₂ reacts with ribulose bisphosphate (RuBP) to form 2 molecules of glycerate 3-phosphate (GP) a 3-carbon compound - RuBisCo catalyses reaction
- GP is reduced to triose phosphate (TP) using energy from ATP & 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
- glucose is the product but it can join to form disaccharides (e.g. sucrose) & polysaccharides (e.g. starch & cellulose) - can also be converted into glycerol & so it can combine with fatty acids to make lipids for the plant
state the limiting factors of photosynthesis
temperature
CO₂ concentration
light intensity
give examples of agricultural techniques that remove limiting factors
heating a greenhouse to increase the temp
burning fuel (e.g. paraffin burners) to release more CO₂
artificial lighting to maximise light intensity
to what extent are agricultural techniques used?
the extent of each technique is used is considered in terms of profit - e.g. if extra growth from photosynthesis is minimal, it will not be cost effective to pay for heating/lighting/fuel
state the 4 key stages of aerobic respiration & where they occur
- glycolysis ~ cytoplasm
- link reaction ~ mitochondrial matrix
- krebs cycle ~ mitochondrial matrix
- oxidative phosphorylation ~ mitochondrial inner membrane cristae
name & explain what occurs during the1st stage of aerobic & anaerobic respiration
glycolysis - occurs in the cytoplasm & its an anaerobic process
- phosphorylating glucose to glucose phosphate, using ATP
- production of triose phosphate
- oxidation of triose phosphate to produce pyruvate with a net gain of ATP & reduced NAD
how & where are pyruvate & NADH transported?
by active transport to the cytoplasm into the mitochondrial matrix
explain what occurs in the link reaction
- the pyruvate in glycolysis is oxidised to acetate
- NAD picks up the H & becomes reduced NAD
- acetate then combines with coenzyme A in to produce acetyl coenzyme A
- the link reaction occurs twice for every glucose molecule
explain what occurs in the kerbs cycle
- acetyl-CoA reacts with a 4 carbon molecule, releasing coenzyme A & producing a 6. carbon molecule that enters the krebs cycle
- in a series of redox reactions, the krebs cycle generates reduced coenzymes & ATP by substrate-level phosphorylation & CO₂
state the products that are formed from the krebs cycle
products per cycle:
3x reduced NAD
1x reduced FAD
1x ATP
2x CO₂
products per glucose molecule:
6x reduced NAD
2x reduced FAD
2x ATP
4x CO₂
explain what occurs in oxidative phosphorylation
- in the mitochondrial matrix, all the reduced coenzymes that were produced are going to release their H (which splits into protons & e-)
- the e- are transported along the e- transfer chain - this releases energy which is used to actively transport the protons from the mitochondrial matrix into the inner membrane space
- the process above creates an electrochemical gradient so the protons can move by facilitated diffusion down their conc gradient through ATP synthase
- ATP synthase phosphorylates ADP to create ATP
- at the end of the e- transfer chain, O₂ picks up e-& protons once they’ve passed through - this creates H₂O
why is oxidative phosphorylation important?
as most ATP is made during this stage
when does anaerobic respiration occur?
occurs in the absence of O₂ & occurs in the cytoplasm of the cell only
in anaerobic respiration what is pyruvate converted into? in what organisms? using what?
in anaerobic respiration, the pyruvate produced in glycolysis is reduced to form ethanol & CO₂ (in plants & microbes) or lactate (in animals) by gaining the hydrogen from reduced NAD
why is pyruvate important?
as it oxidises NAD so that it can be reused in glycolysis & ensures more ATP is continued to be produced
state & explain the role of plants in a food web
in any ecosystem, plants are the producers in the food web as they can produce their carbohydrates using CO₂ in the atmosphere or water
what occurs between each tropic level in a food web?
the majority of the energy is lost due to respiration & excretion & the remaining energy is used to form the biomass
how can we measure the amount of biomass that remains in an organism?
can be measured by terms of mass of carbon or dry mass of tissue per given area
what factors do ecosystems depend on to be productive?
abiotic & biotic factors
give examples of factors that maximise the rates of photosynthesis & their impact
plenty of water, light warmth and green plants maximise rates of photosynthesis & therefore result in more carbohydrates being produced in plants
define GPP
gross primary production
it’s the chemical energy store in plant biomass, in a given area or volume, its the total energy resulting from photosynthesis
define NPP
is the chemical energy store in plant biomass taking into account the energy that will be lost due to respiration (R)
how is NPP calculated?
NPP = GPP - R
how is the net production of consumers (N) calculated?
N = I - F + R
I - the chemical energy store in ingested food
F - the chemical energy lost to the environment
R - respiratory losses
state the units used for rates of productivity
KJ ha-1 year-1
why are the rates of productivity recorded per unit area?
to standardise the results to enable environments to be compared - it takes into account that different environments will vary in size
why are the rates of productivity recorded per year?
as it takes into account the impact sessions will have on rain, light and heat - it provides an annual average to allow fair comparisons between environments
why do organisms need to convert nitrogen gas and what is it converted to?
as animals & plants cannot obtain nitrogen through gas exchange, microorganisms convert nitrogen gas into nitrogen-containing substances that plants & animals can absorb
list the biological molecules that contain nitrogen
proteins
ATP
nucleic acids
what is essential to the key processes of the nitrogen cycle?
saprobiotic nutrition & microbes - refers to when microbes feed on dead plant matter or waste
state the key processes of the nitrogen cycle
- ammonification
- nitrification
- nitrogen fixation
- denitrification
explain the nitrogen cycle
what is phosphorus used for in organisms?
DNA/RNA
ATP
phospholipid bilayer - therefore an essential element for life
explain the difference between the phosphorus cycle and the carbon and nitrogen cycles
as phosphorus is not found as a gas and therefore not in the atmosphere - it is mainly found as a phosphate ion, in mineral form in sedimentary rocks
what are mycorrhizae?
they are fungal associations between plant roots and beneficial fungi
what nutrient cycles can mycorrhizae be found?
nitrogen & phosphorus cycles
explain the benefits of mycorrhizae for plant growth
- the fungi increase the SA for water & mineral absorption
- the mycorrhizae acts like a sponge so it holds water & minerals around the roots
- this makes the plant more drought-resistant & able to take up more inorganic ions
what is the role of mycorrhizae in the nutrient cycles?
improves the uptake of relatively scarce ions, such as phosphate ions - has a mutualistic relationship with nutrient cycles
explain the phosphorus cycle
why are fertilisers used?
they are added to the soil to replace the nitrate & phosphate ions when plants are harvested & removed from nutrient cycles nutrient cycles as crops
state the types of fertilisers
natural (manure)
artificial (inorganic chemicals)
what are artificial fertilisers?
they are fertilisers created to contain exact proportions of minerals
what substances do artificial fertilisers contain?
inorganic substances
explain an advantage of using artificial fertilisers
inorganic substances are more water soluble and therefore more of these ions dissolve in the water surrounding the soil - easier for plants to absorb nitrates & phosphates
explain a disadvantage of using artificial fertilisers
due to its high solubility, larger quantities are washed away with rainfall & therefore have a greater impact on the environment
what is leaching?
it’s when water-soluble compounds are washed away, often into rivers or ponds
what does leaching cause?
eutrophication - if nitrogen fertilisers leach into waterways it causes eutrophication
what is eutrophication?
it’s when nitrates leached from fertilised fields stimulate growth of algae in ponds
explain the effect of eutrophication on plants
the excessive growth of algae creates a blanket on the surface of the water which blocks out the light
as a result, plants below cannot photosynthesis & die
explain the effect of eutrophication on fish
bacteria within the water feed & respire on the dead plant matter
this results in an increase in bacteria, which are all respiring & using up the oxygen in the water
eventually, fish & other aquatic organisms die due to lack of dissolved oxygen in the water
