Energy transfers in and between organisms Flashcards
Producers are aka
autotrophs
How do photoautotrophs synthesise their own food
Using light energy
How do chemoautotrophs synthesise their own food
Using inorganic molecules
How do plants photosynthesise
Using organic compounds from carbon dioxide
What are sugars synthesised used for
Majority- respiratory substances
Rest-used to make other groups of bio molecules e.g cellulose form plant biomass
How to measure biomass
-MASS of carbon
or -Dry mass of tissue per given area
Method of measuring biomass
-Sample of organism dried in an oven set to low temp (to avoid combustion)
-Sample reweighed at regular intervals
-All water removed when mass remains constant
-Mass of Carbon taken to be 50% of dry mass
Why is dry mass more representative
Water content of samples vary
Measuring chemical energy in biomass
-Burn sample of dry biomass
-Energy released is used to heat known volume of water
-Change in temp of water used to calculate chemical energy
What is Gross primary production
Chemical energy stored in plant biomass, in a given area/ volume, in a given time
What is Net primary production
Chemical energy store in plant biomass after respiratory losses to the environment are taken into account
Net production of consumers equation
N=I-(F+R)
I= chemical energy store in ingested food
F=chemical energy lost to the environment in faeces and urine
R= respiratory losses to the enivironment
How is energy transfer inefficient between sun and producer
-Wrong wavelength of light
-Light hits non photosynthetic region
-Light reflected
-Lost as heat
How is energy transfer inefficient between producer →primary consumer →secondary consumer
-Respiratory loss- energy used. for metabolism
-Lost as heat
-Not all plant/ animal eaten
-Some food not digested
Increasing energy transfer efficiency-crops
-Herbicides: kills weeds →less competition →more energy to create biomass
-Fungicides: reduce fungal infections →more energy to create biomass
-Pesticides: reduce loss of biomass from crops
-Fertiilisers: prevent poor growth due too lack of nutrients
Increasing energy transfer efficiency- Livestock
-Restrict movement, and keep warm → more energy to create biomass
-Slaughter animal whilst growing, when most energy is used for growth
-Selective breeding to produce breeds with higher growth rates
- Treated with antibiotics to reduce energy loss due to pathogens
Role of sapriobionts
-Feed on remains of dead plants and their waste and break down organic molecules
-Secrete enzymes for extracellular digestion
-Absorb soluble needed nutrients
Role of mycorrhizae
-Symbiotic relationship between fungi and plant roots
-Fungi act as an extension of the plant roots ( made of thin strands called hyphae)
-Increases surface area of root system → increases rate of absorption
-Mutualistic relationship- plant provides fungi with carbs
-Increases absorption rate in phosphorus cycle
Why is the nitrogen cycle important
Nitrogen is unreactive and not easily converted into other compounds
-Most plants can only take up nitrogen in the form of nitrate
-Use by plants/ animal to make proteins → growth
1.Nitrogen fixation
Nitrogen gas in the atmosphere is turned into Nitrogen containing compounds
- Ammonification
Nitrogen compounds from dead organisms and waste are turned into ammonia by saprobionts, which then turns into ammonium ions
- Nitrification
Ammonium ions in the soil are changed into nitrogen compounds that can be used by plants (nitrates)
Ammonium ions → nitrites →nitrates
4.Denitrification
Nitrates in the soil are converted into nitrogen gas by denitrifying bacteria- using nitrates in the soil to respirate and produce N₂ gas- under an aerobic conditions
Stages of phosphorus cycle
-Phosphate ions in rock released (erosion)
-Phosphate ions taken into plants by roots and incorporated into their biomass
-Phosphate ions transferred through food chain
-Some lost from animals in. waste, and death
Phosphorus cycle- weathering
-Phosphate ions released to sea, lakes, and rivers
-Taken up by aquatic producers
-Passed along food chain
-Guano returns as phosphate ions to soil in coastal areas
Why are fertilisers needed
-Replaces nutrients lost from ecosystems nutrient cycle when crops are harvested, and livestock removed
How do fertilisers improve efficiency of energy transfer
Nutrient no longer limiting factor, increases productivity of agricultural land
Artificial fertilisers
-Inorganic (more water soluble so larger quantities washed away, impacting the environment)
-Contain pure chemicals
Natural fertilisers
-Organic
-Cheaper but exact nutrients can’t be controlled
How does leaching leads to eutrophication
-Rapid growth of algae in ponds and rives
-Algae blocks light, preventing it reaching plants
-Death of plants, no photosynthesis
-Saprobionts decompose the dead plant matter, reducing oxygen concentration of water
-Death of aquatic organisms due to lack of dissolved oxygen for aerobic respiration
Why is leeching less likely with natural fertilisers
-Nitrogen/phosphorus contained in organic molecules
-Organic molecules less soluble in water so need to be decomposed by saprobionts
How does leeching reduce species diversity
-Favours fast growing plants, slower. growing plants lose out, less organisms who feed off them
Overview of photosynthesis
Light dependent reaction on thylakoid membrane in chloroplast
Light independent reaction in stroma in chloroplast
Describe photoionisation
Chlorophyll, in photosystem II, absorbs light energy which excites electrons to a higher energy level, releasing them from the chlorophyll
Excess energy from photoionisation is..
conserved in the production of ATP and reduced NADP
Production of ATP
-Electrons pass down electron transfer chain from PS II to PSI via redox reaction, losing energy at each step
-Energy is used to actively transport protons from stroma into thylakoid creating a (proton) electrochemical gradient across the thylakoid membrane (higher in thylakoid)
-Protons move by fd down the electrochemical gradient into the stroma via enzyme synthase embedded in thylakoid membrane.
-Energy from here allows photophosphorylation
What is photophosphorylation
ADP + Pi → ATP
Production of reduced of NADP
In PS1 electrons are excited and transferred to NADP. (with a proton from photolysis to reduce NADP to form reduced NADP
Photolysis is..
the splitting of water using light energy
Photolysis produces..
Protons, electrons, and oxygen
Products of light dependent reaction
ATP → light independent reaction
Reduced NADP→light independent. reaction
Oxygen→leaves cell as a by-product or used in respiration
Light independent reaction: aka Calvin Cycle
-CO₂ reacts with ribulose bisphosphate (RuBP) (5C), catalysed by enzyme rubisco
-Produces 2 molecules of glycerate 3-phosphate (3C)
-GP reduced to triose phosphate using products from light dependent reaction
-Some TP converted into useful organic substances
-TP used to regenerate RuBP (using rest of ATP)
Limiting Rates: Temperature
Rate of photosynthesis increases as temperature increases up to optimum, then decreases
Limiting rates: Light intensity
Rate of photosynthesis increases as light intensity increases
What would happen if light intensity was drastically reduced
Levels of ATP and reduced NADP would fall, as light dependent reaction limited as less photoionisation of chlorophyll, so light independent reaction would slow as GP can’t be reduced to TP and then can’t generate RuBP (requires ATP)
Limiting rates: CO₂ concentration
Rate of photosynthesis increases as CO₂ conc increases
What would happen if CO₂ was drastically reduced
-Limits light independent reaction
-Less CO₂ to combine with RuBP to form GP
-Less GP reduced to form TP
-Less TP converted to organic substances and generated into RuBP
What will happen if limiting factors are minimal
Faster production of glucose allowing faster respiration, more ATP to provide energy for growth, higher yield so more profit
Examples of common agricultural practices to overcome limiting factors
-Growing plants under artificial light to maximise light intensity
-Heating a greenhouse to increase temperature
-Burning fuel to release more CO₂
What does respiration produce
ATP
Stage 1: glycolysis
Phosphorylation of glucose → glucose phosphate, using inorganic phosphates from 2ATP. Hydrolyses into 2x triose phosphates, which oxidises to 2xpyruvate. 2 NAD reduced →collects Hydrogen ions, 4 ATP regenerated
Glycolysis conditions
Occurs in cytoplasm, anaerobic,
Products of glycolysis
2x pyruvate, net gain of 2x ATP, 2x reduced NADP
After glycolysis (anaerobic)
In the cytoplasm, pyruvate is converted to lactate (animal cells & bacteria) or ethanol.
Reduced NAD is oxidised→NAD and is regenerated. Glycolysis can continue (which needs NAD) allowing continued production of ATP.
Process of lactic acid fermentation
Glucose converted to pyruvate, pyruvate converted to lactic acid. This process releases energy in the form of ATP, which can be used by the cells.
Process of alcoholic fermentation
Glucose converted to pyruvate, pyruvate converted to acetaldehyde and carbon dioxide. Acetaldehyde converted into ethanol. This releases energy in the form of ATP, which can be used by the cells.
Efficiency of anaerobic respiration; produces less ATP per molecule of glucose.
Only glycolysis involved which produces little ATP (2 molecules). No oxidative phosphorylation which forms majority of ATP (around 32
molecules) Some energy still in lactate; incomplete oxidation glucose.
After glycolysis (aerobic)
Pyruvate actively transported. into the mitochondrial matrix
Link reaction
In the mitochondrial matrix, pyruvate oxidised (and decarboxylated) to acetate. CO2 produced and reduced NADP produced (picks up H). Acetate combines with coenzyme A= Acetyl cooenzyme A
Link reaction: Products per glucose molecule
2x acetyl coenzyme A
2x CO2
2x reduced NADP
Krebs cycle
In the mitochondrial matrix, acetyl coenzyme A (2C) 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 4C molecule is regenerated and 2x CO2 is lost, coenzymes NAD and FAD reduced, substrate level phosphorylation (direct transfer of Pi from intermediate compound to ADP) → ATP produced
Krebs cycle: Products per glucose molecule
Useful- 6x reduced NAD; 2x reduced FAD; 2x ATP
Waste- 4x CO2
Oxidative phosphorylation
In the inner mitochondrial membrane, reduced. NAD+FAD oxidised to release H atoms. Electrons are transferred down the electron transfer chain by redox reactions. Energy released by electron carriers to actively transport protons from the matrix → intermembrane space. Protons diffuse into matrix down an. electrochemical gradient, via ATP synthase (embedded in inner. mitochondrial membrane), releasing energy to synthesise ATP from ADP+Pi. In the matrix at the end of the electron transfer chain, Oxygen is the final electron acceptor, so protons electrons and oxygen combine to form water.
Respiratory substrates
Fatty acids from hydrolysis of lipids → converted to Acetyl coenzyme A
Amino acids from hydrolysis of proteins → converted to intermediate in Krebs cycle
