Biology: Energy transfer in and between organisms Flashcards
What is biomass?
The dry mass of an organism
What are the units for biomass?
grams or kilograms/m^-2
what are saprobionts?
Microbes which feed on dead organisms, decomposing them.
Why are saprobionts important?
When a plant or animal dies, saprobionts release nutrients back into the soil as they decompose the dead matter, making the soil fertile.
What is an ecosystem?
An area in which organisms live, contains all of the biotic and abiotic factors of an area.
Describe the process of calorimetry.
- Weigh the sample and burn it in pure oxygen.
- Measure the temperature change of the water in order to obtain the estimate amount of energy in the sample.
Define NPP
Net primary production, the energy produced by a plant, taking expenses into consideration.
Define GPP
The amount of energy/biomass created by a plant.
What is the equation for NPP in plants?
NPP = GPP - R
R = energy used for growth, repair etc.
What is the equation for NPP in animals?
NPP = energy taken in - (energy lost in respiration + energy lost in faeces)
Why do most food chains only have around 4 trophic levels?
Because a 5th trophic level would have insufficient energy to support life as energy is lost at each stage of a food chain.
What is the role of mycorrhizae?
It exists in a mutualistic relationship with plants. They absorb water/nutrients etc. to keep it close to plant roots in order to keep the plant alive.
Why are fertilisers needed on farmed land and not natural habitats?
In farmed land, plants take up nutrients from the soil, but are removed from the ground before they die and are able to return the nutrients to the soil. This means that fertilisers are needed to keep the soil fertile. In natural habitats, plants die and return nutrients to the soil, so the soil is always fertile.
What is nitrification?
When ammonia ions and converted into nitrite ions.
what is denitrification?
When nitrate ions and converted into nitrogen gas.
How does applying high concentrations of fertiliser to the soil reduce plant growth?
Too much fertiliser changes the water potential of the soil, making it more negative. This results in water being lost from the plant due to osmosis.
What is the difference between natural and artificial fertilisers?
- Artificial fertilisers are mined from rocks and can be made for specific plants.
- Natural fertilisers are non-specific and organic.
What is leaching?
When water is washed deep within the soil due to rainfall.
Describe the process of eutrophication.
- Farmers fertilise fields.
- It rains, fertiliser is washed from the soil and into water sources.
- Water becomes very nutrient rich, algae and bacteria populations thrive.
- A thick algal bloom covers the surface of the water, plants below it die due to lack of oxygen.
- Bacteria feed off the dead plants, food is no longer a limiting factor.
- Bacteria use up all of the oxygen, the water become anoxic and all respiring organisms die.
- The water becomes putrid as they decompose.
What happens in the ammonification stage of the nitrogen cycle?
Saprobionts feed on dead and decaying organic matter. This releases ammonia ions.
What happens in the nitrification stage of the nitrogen cycle?
Nitrifying bacteria convert ammonia ions into nitrite ions
What happens in the nitrogen fixation stage of the nirtogen cycle?
Nitrogen gas is converted into nitrogen containing compounds by free-living and mutualistic bacteria.
What happens in the denitrification stage of the nitrogen cycle/
Denitrifying bacteria convert nitrates into nitrogen gas.
What is a biosphere?
Regions of the surface and atmosphere of earth occupied by living organisms.
Describe what happens in the phosphorus cycle.
- Over time, rain and weathering cause rocks to release phosphate ions and other minerals. This inorganic phosphate is then distributed in soils and water.
- Plants take up inorganic phosphate from the soil. The plants may then be consumed by animals. Once in the plant or animal, the phosphate is incorporated into organic molecules such as DNA. When the plant or animal dies, it decays, and the organic phosphate is returned to the soil.
- Within the soil, organic forms of phosphate can be made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus. This process is known as mineralisation.
- Phosphorus in soil can end up in waterways and eventually oceans. Once there, it can be incorporated into sediments over time.
Which cells make up the upper mesophyll layer?
Which cells make up the upper mesophyll layer?
Where does the light dependent reaction occur?
Thylakoid membrane
Describe the process of photoionisation
light hits chlorophyll, causing it to lose electrons
What happens to an electron when it enters the ETC?
- travels along the chain, being taken in by electron acceptors.
- it reaches photosystem II and is boosted to a higher energy level.
- it continues to travel along the ETC, losing energy as it does so.
- it reaches photosyetem I and its energy level is boosted a second time.
- when it reaches the end of the ETC, it’s absorbed by NADP, reducing it.
What happens to the energy lost from electrons?
It’s used to actively transport protons into the thyklakoid. this forms a concentration gradient, protons then travel back into the stroma through ATP synthase, which phosphorylates ADP.
What is made in the photolysis of water?
protons, electrons, oxygen
How is chlorophyll reduced after it loses its electrons?
photolysis of water results in electrons, which are used to reduce chlorophyll.
What are the 3 stages of the light independent reaction?
carbon fixation, reduction, regeneration
which 5C compound binds with CO2 during the light independent reaction?
RuBP
which enzyme catalyses the reaction between RuBP and CO2?
rubisco
after CO2 binds to RuBP, an unstable 6C compound is made and is broken into 2 3C compounds, what are they called?
GP
How many times does the calvin cycle need to happen in order to produce 1 glucose molecule?
6
What are the products of the light-dependent reaction?
ATP, NADPH (reduced NADP)
where does the light-independent reaction take place?
stroma of the chloroplasts
state the process of the calvin cycle
- CO2 diffuses into the leaf through the stomata and into the stroma.
- CO2 joins with RuBP to form an unstable 6C compound in a reaction catalysed by the enzyme rubisco.
- the 6C compound is unstable and so it breaks up into 2 3C compounds calles GP.
- NADPH is used to reduce GP into triose phosphate using energy from ATP.
- NADP is reformed and goes back to the light dependent reaction.
- 1/6 triose phosphate molecules are used to make organic molecules. the rest regenerate RuBP.
what is aerobic and anaerobic respiration?
AEROBIC:
requires oxygen. produces CO2, water and much ATP.
ANAEROBIC:
takes place in the absence of oxygen and produces lactate and little ATP
what are the 4 stages of aerobic respiration?
describe each
Glycolysis: the splitting of the 6C glucose molecule into 2 3C pyruvate molecules.
Link reaction: the 3C pyruvate molecules enter a series of reactions which lead to the formation of acetylcoenzyme A, a 2C molecule.
Krebs cycle: the introduction of acetylcoenzyme A into a cycle of redox reactions that make ATP and NAD, FAD
Oxidative phosphorylation: the use of electrons associated with reduced NAD and FAD to synthesise ATP
describe the process of glycolysis
phosphorylation of glucose into glucose phosphate: glucose has 2 phosphate molecules added to it to make it more unstable. the phosphate comes from the hydrolysis of 2 ATP molecules. this provides the energy at activate glucose + lowers activation energy of reactions that follow.
splitting of phosphorylated glucose: each glucose is split into two 3C molecules called triose phosphate.
oxidation of triose phosphate: hydrogen is removed from each triose phosphate molecule. They’re transferred to a hydrogen carrier molecule called NAD, this forms reduced NAD.
production of ATP: 3C molecules converted into pyruvate. 2 molecules of ATP regenerated from ADP in the process.
what happens in the link reaction?
- pyruvate oxidised into acetate. hydrogens are accepted by NAD and forms reduced NAD which is later used to produce ATP.
- the 2C acetate combines with coenzyme A to produce acetylcoenzyme A.
what happens in the krebs cycle?
- acetylcoenzyme A joins with a 4C molecule.
- the 6C molecule loses carbon dioxide to give a 4C molecule and a single ATP molecule.
- the 4C molecule can join at acetylcoenzyme A to start the cycle again.
describe the process of oxidative phosphorylation.
happens in the mitochondria
- hydrogen atoms produced in glycolysis and the Krebs cycle combine with NAD and FAD.
- rNAD and rFAD donate the electrons to the first molecule on the electron transport chain.
- electrons pass through the electron transport chain, the energy they release causes the active transport of proteins across the inner mitochondrial membrane and into the inter-membranal space.
- protons accumulate in the inter-membranal space before they diffuse back into the matrix through ATP synthase.
- at the end of the chain, electrons combine with protons and oxygen to form water, oxygen is therefore the final acceptor of electrons in the electron transport chain.
