Powering Life: Harnessing Chemical Energy

Question 1

phototroph

Answer 1

harness energy from sunlight eg. Plants

Question 2

chemotroph

Answer 2

derive energy directly from chemical compounds eg. Animals and cellular respiration.

Question 3

autotroph

Answer 3

convert carbon dioxide into glucose. Self feeders such as plants

Question 4

heterotroph

Answer 4

other feeders, rely on other organisms as their source of carbon. Such as animals

Question 5

combinations of trophs

Answer 5

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

Question 6

metabolism

Answer 6

set of chemical reactions that convert molecules into other molecules and transfer energy in living organisms.
Linked reactions

Question 7

catabolism and anabolism

Answer 7

Catabolism: break down molecules into small units and produces ATP.

Anabolism: build molecules from smaller units and requires input.

Question 8

cellular respiration

Answer 8

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

Question 9

what does CR produce and what type of reaction is it?

Answer 9

Produces: ATP, carbon dioxide and water

Can be aerobic or anaerobic

Question 10

aerobic respiration - how does it occur, energy production

Answer 10

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

Question 11

types of ATP generation

Answer 11

substrate level generation and oxidative phosphorylation

Question 12

substrate level generation

Answer 12

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)

Question 13

oxidative phosphorylation

Answer 13

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

Question 14

what are the energy carriers? what is reduced and what is oxidised? equations?

Answer 14

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

Question 15

what is oxidised and what is reduced in CR?

Answer 15

Glucose is oxidised

Oxygen is reduced

Question 16

stage 1: glycolysis - overview, eukaryotes, basic process, evolution, reactions

Answer 16

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

Question 17

phase 1 of glycolysis

Answer 17

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

Question 18

phase 2 of glycolysis

Answer 18

Cleavage of 6 carbon molecule

Two 3 carbon molecules are produced

Question 19

phase 3 of glycolysis

Answer 19

Payoff phase
ATP and NADH are produced
Two pyruvate

Question 20

stage 2 of CR - process and location

Answer 20

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

Question 21

stage 3: citric acid cycle

Answer 21

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

Question 22

stage 4: oxidative phosphorylation overview and location

Answer 22

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)

Question 23

OP transferring electrons and proton pumps

Answer 23

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

Question 24

OP the proton gradient

Answer 24

Protons cannot passively diffuse
Chemical gradient and electrical gradients formed (Electrochemical)
Source of paternal energy
Potential energy is used to make ATP

Question 25

OP ATP synthase

Answer 25

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

Question 26

energy from aerobic respiration

Answer 26

7 from glycolysis
5 from pyruvate oxidation
20 from citric acid
32 total

Question 27

membranes of the mitochondria

Answer 27

Inter membrane space: space between inner and outer membranes

Mitochondrial matrix: space enclosed by the inner membrane

Question 28

earliest energy harnessing reactions

Answer 28

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

Question 29

Gibbs free energy and CR

Answer 29

Glycolysis is endogonic - ATP input
Pay off stage is mostly exergonic
Pirate oxidation is mostly exergonic
Citric acid cycle is mostly exergonic

Question 30

carbon cycle

Answer 30

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

Question 31

oxygen transport cascade

Answer 31

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

Question 32

oxygen cascade with exercise

Answer 32

Respiration increases
Heart rate and cardiac output increase
Oxygen extraction increases - diffusion down concentration gradient to mitochondria

Question 33

exercise training

Answer 33

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

Question 34

change in oxygen supply and penguins

Answer 34

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

Question 35

what happens without oxygen?

Answer 35

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

Question 36

diving response

Answer 36

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