energy transfer

What are the two stages of photosynthesis and what do they do

• light dependent reaction which produces O2, NADPH and ATP from water and light energy

• Light independent reaction which produces glucose from ATP, CO2 and NADPH

Where do the two stages of photosynthesis occur

• light independent reaction = thylakoid

• Light independent reaction = stroma

What are photo systems

Proteins within the thylakoid which contains chlorophyll

What are the photosystems linked by

Electron carrier proteins

What are electron carrier proteins

Proteins than can transfer electrons and form the electron transport chain

What are co enzymes

Molecules that aid enzymes with the transfer of chemical groups such as hydrogen

What is OILRIG

• oxidation is loss of electrons and hydrogen

• Reduction is the gain of electrons and hydrogen

What is a coenzyme used in photosynthesis

NADP as it transfers hydrogen from one molecule to another so it oxidises or reduces

What is photolysis

Light energy is absorbed by chlorophyll and splits water into oxygen protons and electrons

What is the equation for photolysis

H2O → ½ O2 + 2e- + 2H+

What occurs during photoionisation

• photons of light absorbed by chlorophyll and the electrons within are excited

• This means they are transferred to electron carriers at higher energy levels

• This means chlorophyll is oxidised

What occurs in chemiosmosis

• electron moves down the electron transport chain by a series of oxidation and reduction reactions and it loses energy as it travels down

• This energy is used to pump the protons into the thylakoid lumen

• This leads to a higher concentration of protons in the lumen which means they move down an electrochemical gradient into stroma via ATP synthase

  • This movement releases energy which combines with ADP and Pi to form ATP

• The electrons are then transferred to NADP with a proton to form NADPH

What is the light independent reaction known as

The Calvin cycle

What are the features of the light independent reaction

• catalysed by enzyme Rubsico

• Temperature sensitive due to the involvement of enzymes

What is the AT used for in the LIR

To release energy

What is the NADPH used for in the LIR

Donates the hydrogen to reduce GP

What is RUBP

A five carbon compound

What is GP

A three carbon compound

What happens in the Calvin cycle

• CO2 reacts with RuBP to form 2 GP which is catalysed by Rubsico

• GP reduced into triose phosphate using energy from ATP and hydrogen from NADPH

• Triose phosphate used to create a organic substances like glucose with one carbon

• Rest of the triose phosphate is used to regenerate RuBP with energy from ATP

• Cycle repeats until the heroes sugars like glucose is formed

What is glucose used for in plants

• to form disaccharides and polysaccharides like sucrose and starch for storage

• Lipids

Where does respiration take place

• glycolysis takes place in the cytoplasm

• Link reaction, Krebs cycle and oxidative phosphorylation takes place in the mitochondria

What are the three coenzymes in respiration

• NAD - transfers hydrogen from one molecule to another

• FAD - transfers hydrogen from one molecule to another

• Coenzyme A x transfers acetate between molecules

What is the purpose of glycolysis

The breakdown of glucose into pyruvate via phosphorylation and oxidation v

Describe the process of glycolysis

• glucose phosphorylated using 2x ATP to form phosphorylated glucose and 2x ADP

• The phosphorylated glucose then splits to 2x triose phosphate

• Triose phosphate is then oxidised to form 2x pyruvate

  • The hydrogen lost from triose phosphate is collected with NAD to form 2x NADH

• A total of 4 ATP produced but only net gain of 2x ATP

Why is forming pyruvate important

It can pass through the plasma membrane but glucose can’t

Where does the link reaction take place

Mitochondrial matrix

Describe the link reaction

• 2x Pyruvate is decarboxylated and the carbon is expelled as CO2

• The pyruvate is oxidised to form 2x acetate (2C) and the hydrogen lost is used for form NADH

• 2x acetate combined with coenzyme A to form 2x acetyl coenzyme A

What doesnt the link reaction produce

ATP

Briefly explain the Krebs cycle

A series of redox reactions where reduced coenzymes and ATP are produced

Describe the Krebs cycle

• Acetyl coA combines with 4 carbon compound to from 6 carbon compound and removed coenzyme A

• 6 carbon compound is then carboxylated and expelled as CO2 as well as losing hydrogen to form NADH and a 5 carbon compound

• The 5 carbon compound is carboxylated and oxidised to from 2x NADH and 1x FADH and 1x ATP

• this process repeats with each acetyl coA

How is the ATP formed in the Krebs cycle

Via substrate level phosphorylation

What happens to the coenzyme A expelled in the start of Krebs cycle

It is recycled in the link reaction

Where does the Krebs cycle take place

Mitochondrial matrix

Where does oxidative phosphorylation take place

In the mitochondrial cristae

Describe oxidative phosphorylation

• NADH and FADH are oxidised to form NAD and FAD

  • Hydrogen splits into protons and electrons

• Electrons move down the electron transport chain consisting of three carrier proteins via a series of redox reactions

• As they move down, they lose energy which then pumps protons in the intermembrane space

• Eventually, the concentration of protons exceeds the concentration in the matrix so they move down back into the matrix down the electrochemical gradient via facilitated diffusion

• this movement releases energy which combines ADP and Pi to form ATP via ATP synthase

• At the end of the transport chain, the electrons are then picked up by the final electron acceptor which is oxygen which then combines with protons to form water

Why does anaerobic respiration occur

Happens due to oxygen no longer being the final electron acceptor so no electron transport chain

Describe the process of anaerobic respiration in animals

• same as glycolysis But eventually the NAD becomes a limiting factor after net gain of 2x ATP

• This means pyruvate is reduced to lactate using the H from NADH regenerating NAD to form more ATP

Negatives of anaerobic respiration

• produces less ATP due to no oxidative phosphorylation

• Lactate is acidic so is poisonous to muscles so cramps/ fatigues

Describe anaerobic respiration in plants

• same as glycolysis

• Pyruvate is decarboxylated to form ethanal and then is reduced to form ethanol using the H from NADH, regenerating NAD

Explain why the coloured droplet moves in the respiration practica

• oxygen diffuses into the organism as its used in respiration

• It expels CO2 which is absorbed by thr KOH

• This reduced the volume of gas in the tube and so the pressure so air moves in down pressure gradient moving the droplet with it

How do you reset the respirometer practical

• open the three way tap

• Push down on syringe

How would we set up a control for the respirometer practical

• replace the organisms with inert glass beads

• Keep all apparatus the same

• Proves that the pressure differential is caused by the organism

Why might the top be left open at the start of the respirometer practical

• To reach equilibrium

• Allow for the pressure changes of the apparatus

• Stabilises respiration rate

What is biomass

The mass of dry mass / carbon per given area

What is gross primary productivity

The total amount of chemical energy converted from light energy by plants during photosynthesis per given area

What is net primary productivity

Energy stored as biomass and what is available for next trophic levels

What is some energy lost as from GPP

Respiratory losses

How to calculate NPP

NPP = GPP - R

How to calculate net production of consumers

N = I - F - R

• I = chemical energy stored in ingested food

• F = chemical energy lost to environment as faeces and urine

• R = respiratory losses

Why is energy lost as we go up trophic levels

• some parts of organisms not eaten

• Egressed as faeces

• Excretion as urine

• Respiratory losse

How to calculate efficiency of energy transfer

Efficiency = net production of trophic level / net production of previous trophic level x 100

Why is nitrogen cycle needed

To break down nitrogen containing compounds and release the nitrogen back to the atmosphere

What are nitrogen containing compounds

• protein

• ATP

• DNA

• Urea

What are the stages of the nitrogen cycle

• ammonification

• Nitrification

• Denitrification

• Nitrogen fixation

What is ammonification

When an organism dies, the sabrobionts decompose the nitrogen containing compounds such as protein to produce ammonia

What is nitrification

The ammonia is oxidised to nitrites which is oxidised further to nitrates via nitrifying bacteria under aerobic conditions

How are the nitrates taken up into the plants

Via active transport and it’s assimilated into tissues to form nitrogen containing compounds

What is denitrification

Denitrifying bacteria convert nitrates in soil back to nitrogen gas under anaerobic conditions

What is nitrogen fixation

Nitrogen fixing bacteria reduce nitrogen to ammonia

Where are nitrogen fixing bacteria present

Free living or a symbiotic relationship with the plants via root nodules