Powering Life: Harnessing Chemical Energy Flashcards
phototroph
harness energy from sunlight eg. Plants
chemotroph
derive energy directly from chemical compounds eg. Animals and cellular respiration.
autotroph
convert carbon dioxide into glucose. Self feeders such as plants
heterotroph
other feeders, rely on other organisms as their source of carbon. Such as animals
combinations of trophs
Plants are phototrophs and autotrophs (photoautotrophs)
Animals are chemotrophs and heterotrophs (chemoheterotrophs)
Animals can get energy and carbon from the same molecule - glucose
Photoheterotrophs: gain energy from the sun and carbon from preformed carbon molecules
Chemoautotrophs: extract energy from inorganic sources and build their own organic molecules
metabolism
set of chemical reactions that convert molecules into other molecules and transfer energy in living organisms.
Linked reactions
catabolism and anabolism
Catabolism: break down molecules into small units and produces ATP.
Anabolism: build molecules from smaller units and requires input.
cellular respiration
Cellular respiration: breaking down compounds to release energy to be used by the cell.
Chemical energy from molecules into chemical energy of ATP
Catabolic reaction
what does CR produce and what type of reaction is it?
Produces: ATP, carbon dioxide and water
Can be aerobic or anaerobic
aerobic respiration - how does it occur, energy production
C6H12O6 + 6O2 —> 6CO2 + 6H2O + energy
Energy in bonds of glucose and oxygen is greater than carbon dioxide and water (output of energy)
Max free energy (energy available to do work) is -686 kcal per mole of glucose
If all the energy of glucose was released in one step, most of the energy would be released as heat
32 ATP from 1 glucose
7.3 kcal to make mole ATP from ADP + Pi
32 x 7.3 = 233.6 kcal of energy from one glucose
34% of energy from respiration harnessed in ATP, rest is heat
types of ATP generation
substrate level generation and oxidative phosphorylation
substrate level generation
Substrate level phosphorylation
Phosphorylated molecule transfers a phosphate group to ADP
Two coupled reactions carried out by one enzyme
Hydrolysis reaction of phosphorylated organic molecule releases energy to drive ATP synthesis
Phosphate group is transferred to ADP from an enzyme substrate
Small amount of ATP (12% for glucose)
oxidative phosphorylation
Oxidative phosphorylation
88% of ATP
Chemical energy of organic molecules is transferred to electron carriers
Transport electrons from catabolism of organic molecule to electron transport chain
Electrons move along a series of membrane associated proteins to the final electron acceptor (oxygen in aerobic respiration) and form water - harnesses energy to produce ATP
what are the energy carriers? what is reduced and what is oxidised? equations?
NADH
FADH2
Oxidation reactions in cellular respiration are coupled with reduction of electron carriers
Reduction (opposite is oxidation):
NAD+ + 2e- + H+ —> NADH
FAD + 2e- + 2H+ —> FADH2
Reduced molecules have increased C-H bonds
Oxidised molecules have decrease C-H bonds
Shuttle electrons
what is oxidised and what is reduced in CR?
Glucose is oxidised
Oxygen is reduced
stage 1: glycolysis - overview, eukaryotes, basic process, evolution, reactions
Glycolysis: glucose is partially broken down to make pyruvate and energy is transferred to ATP and reduced energy carriers. Splitting sugar
Eukaryotes: cytoplasm
6 carbon sugar to two 3 carbon molecules
Anaerobic
Evolved early when oxygen was not present in the atmosphere
Net 2 ATP (substrate level phosphorylation) and 2 NADH
10 reactions - three phases
phase 1 of glycolysis
Two phosphate groups added to glucose
Input of energy
Two ATP are hydrolysed per 1 glucose
Phosphorylated glucose is trapped in the cell (cannot be transported)
Negatively charged phosphate groups destabilise the molecule so it can be broken down
phase 2 of glycolysis
Cleavage of 6 carbon molecule
Two 3 carbon molecules are produced
phase 3 of glycolysis
Payoff phase
ATP and NADH are produced
Two pyruvate
stage 2 of CR - process and location
Pyruvate is oxidised to acetyl-coenzyme A
Reduced electron carriers and CO2 (most oxidised C) are released
2 NADH is produced
2 CO2
Part of pyruvate is oxidised first
The remaining acetyl group (COCH3) contains a large amount of potential energy that is transferred to coenzyme A which carries the acetyl group to the next reactions (2 Acetyl-CoA)
Eukaryotes: mitochondria
stage 3: citric acid cycle
TCA cycle or Krebs cycle
Series of 8 reactions
A cycle - starting molecule oxaloacetate is regenerated
Acetyl group (substrate) is oxidised to carbon dioxide and energy is transferred to energy and reduced electron carriers
2 carbon acetyl group of acetyl CoA is transferred to 4 carbon oxaloacetate to form 6 carbon citric acid or tricarboxylic acid - this is oxidised (2 carbons are lost to CO2)
Oxidation coupled with reduction of NAD+
More NADH and FADH2 are released in other reactions
3 NADH per cycle
1 FADH per cycle
Amount of energy is nearly twice that of stages one and two
Electrons supplied to electron transport chain by electron carriers
One substrate level phosphorylation that makes GTP - GTP transfers terminal phosphate to ADP to make ATP
Two acetyl-CoA are made from glucose and yield 2 ATP, 6 NADH and 2 FADH2
Eukaryotes: mitochondria
stage 4: oxidative phosphorylation overview and location
Reduced electron carriers from previous stages donate electrons to electron transport chain (inner mitochondrial membrane in eukaryotes)
Large amount of ATP produced
Eukaryotes: mitochondria
Some bacteria: electron transport chain takes place in the plasma membrane (rest in cytoplasm)
OP transferring electrons and proton pumps
Electrons from NADH and FADH2 are transported along four large protein complexes (I to IV)
Proteins are embedded in mitochondrial inner membrane
Very high concentration of proteins
Electrons enter at complex I (NADH) or II (FADH2)
II is the same enzyme that catalyses step 6 of the citric acid cycle
Within each complex, electrons are passed from electron donors to electron acceptors (redox couples) eg. Oxygen reduced to form water at complex IV
Coenzyme Q or ubiquinone accepts electrons from I and II (2 electrons and 2 protons from the mitochondrial matrix, forming CoQH2)
CoQH2 diffuses in the inner membrane to III
In III electrons are transferred from CoQH2 to cytochrome c and protons are released into the inter membrane space
Cytochrome c is reduced and diffuses to IV
Oxygen is the final acceptor
Some energy is used to reduce the next carrier but I, II and IV use some energy to pump protons
Accumulation of protons in inter membrane space
OP the proton gradient
Protons cannot passively diffuse
Chemical gradient and electrical gradients formed (Electrochemical)
Source of paternal energy
Potential energy is used to make ATP
OP ATP synthase
Converts energy of the proton gradient into the energy of ATP
Potential energy converted into chemical energy of ATP
Protons move down the gradient by protein channels
Movement of proton is coupled with synthesis of ATP
ATP synthase couple the reactions - subunits F0 and F1
F0 forms a channel for the protons to flow F1 catalyses the synthesis of ATP
Proton flow causes channel to rotate creating mechanical rotational energy (kinetic energy)
F1 subunit also rotates in the mitochondrial matrix causing conformational changes that allow it to catalyse the synthesis of ATP (mechanical to chemical energy)
This is the chemiosmotic hypothesis
2.5 ATP for NADH
1.5 ATP for FADH2
Overall 32 ATP from one glucose
energy from aerobic respiration
7 from glycolysis
5 from pyruvate oxidation
20 from citric acid
32 total
membranes of the mitochondria
Inter membrane space: space between inner and outer membranes
Mitochondrial matrix: space enclosed by the inner membrane
earliest energy harnessing reactions
Some bacteria do the citric acid cycle in reverse - add carbon dioxide to organic molecules, requires energy from sunlight
Allows them to build organic molecules
Pyruvate is start of sugars and amino acid alanine
Acetate is start of lipids
Oxaloacetate can form amino acids and pyrimidine bases
Alpha ketoglutarate is used in amino acids
The citric acid cycle (both ways) is found very early in metabolism
Gibbs free energy and CR
Glycolysis is endogonic - ATP input
Pay off stage is mostly exergonic
Pirate oxidation is mostly exergonic
Citric acid cycle is mostly exergonic
carbon cycle
Carbon cycle: cycle of matter through producers and consumers, they die etc.
Energy flows through levels of organisation
Detritus - organisms breaking down or things they shed, dead and decaying
oxygen transport cascade
From the atmosphere to the lungs, through the circulatory system to the mitochondria (cellular respiration)
Nutrients are carried in the blood - fuel
Synthesis, ion transport and muscles demand
Balance between supply and demand
oxygen cascade with exercise
Respiration increases
Heart rate and cardiac output increase
Oxygen extraction increases - diffusion down concentration gradient to mitochondria
exercise training
Marathon runners compared to people that do not run
Breath air in and out into a mask thing
Works out how much oxygen is consumed, frequency of breath and heart rate
Oxygen consumption increases with fitness (regardless of how fast heart rate is)
Heart is able to pump more blood with each beat in fitter people
Unfit people need a higher heart rate to get the oxygen consumption needed
change in oxygen supply and penguins
Penguins diving
500m down for 9 minutes as an example
Time pressure
Depth pressure, atmospheric pressure 10m = 1atm
If we went down 300m, we would need lots of oxygen delivered and it takes 11.5h to ascend without getting sick
Dark past 200m
Oxygen uptake from the air is decoupled from cellular respiration - rely on stored oxygen
what happens without oxygen?
Anaerobic respiration Glycolysis: glucose makes pyruvate and then lactate 2 ATP are made Not enough ATP is made though Lactic acid build up which is toxic Fast
diving response
Hooked up to an ECG, holds breath and puts face in water
Pressure transducer strapped to thumb records heard rate
Heart rate dropped as low as 48 BPM
If water was colder, heart rate would decrease further
Blood flow to tissues and organs was being redistributed - supply only important organs such as brain, muscles but over time that changes
Things like digestive tract use less oxygen
Would see a bit of anaerobic metabolism
Oxygen content declines, store is consumed from air sacs and blood but some is preserved
Lactate begins to increase
After 6 minutes, muscles begin to do some aerobic respiration and lactate increases so that oxygen can be preserved for the brain
Less oxygen being delivered so the heart does not need to pump as much. Also the heart requires a lot of oxygen so slowing it, makes it use less oxygen and energy
