respiration

Question 1

Aerobic Respiration

Answer 1

The release of large amounts of energy made available as ATP- produced from breakdown of molecules, w/ oxygen as terminal electron acceptor

Question 2

Anaerobic Respiration

Answer 2

breakdown of molecules in the absence of oxygen , releasing relatively little energy, making a small amount of ATP by substrate- level phosphorylation. There’s obligate aerobes, facultative anaerobes and obligate anaerobes

Question 3

Dehydrogenation

Answer 3

The removal of one or more hydrogen atoms from a molecule

Question 4

Decarboxylation

Answer 4

The removal of a carboxyl group from a molecule, releasing CO2.

Question 5

Metabolism

Answer 5

Respiration is a catabolic process involving a series of enzyme-catalysed reactions in cells, where energy-rich respiratory substrates, e.g. glucose and fatty acids, are broken down to release energy: some is trapped as chemical energy in ATP and some is released as heat energy.

Question 6

Metabolism pt 2

Answer 6

During respiration, high energy C-C, C-H and C-OH bonds are broken, lower energy bonds are formed and the difference is released and used to attach iP to ADP to make ATP- ATP does not ‘produce’ energy- but when hydrolysed releases energy. Energy= available to use by cell or is lost as heat.

Question 7

Oxidative phosphorylation.

Answer 7

occurs on inner membranes of mitochondria in aerobic respiration- energy for making ATP comes from oxidation- reduction reactions- released in the transfer of electrons- along a chain of electron carrier molecules

Question 8

Photophosphorylation

Answer 8

Photophosphorylation- occurs in thylakoid membranes of the chloroplasts in the light- dependent stage of photosynthesis- energy for making ATP comes from light- is released in transfer of electrons along a chain of electron carrier molecules- photophosphorylation does not occur in respiration.

Question 9

Substrate level phosphorylation

Answer 9

Substrate level phosphorylation- occurs when phosphate groups are transferred from donor molecules e.g. glycerate 3- phosphate to ADP to make ATP in glycolysis or when enough energy is released from a reaction to bind ADP to inorganic phosphate eg in krebs.

Question 10

More on respiration- processes/ aerobic formula

Answer 10

Processes that require energy- active transport, movement, formation of complex molecules eg proteins- comes from respiration Formula for aerobic respiration of glucose C6H1206 +6CO2—> 6CO2 +6H2O+ energy (ATP) Glucose + oxygen—> carbon dioxide + water But can also use lipids and proteins in respiration

Question 11

ATP- more

Answer 11

Reacting ATP with water is an example of a hydrolysis reaction catalysed with with ATP hydrolase also called ATPase ATP + water —> ADP + Pi + energy At end of the reaction made adenosine diphosphate (ADP) and released phosphate ion Given symbol Pi- i tells us it’s inorganic- not bonded to a carbon containing molecule -2 processes in respiration that can reform ATP- substrate level phosphorylation and oxidative phosphorylation- oxidative phosphorylation produces the vast majority of ATP during respiration

Question 12

ATP formation

Answer 12

Once ATP is hydrolyzed has to be reformed to be used again ATP is formed in respiration in the energy stored in glucose- when ATP is reformed- energy from glucose is used is used to add a phosphate ion back on to ADP- process is called phosphorylation

Question 13

ATP formation-more

Answer 13

ATP formation- more Cells use energy in glucose to produce ATP in respiration- during respiration a large no. chemical reactions gradually break down the glucose molecule- during some of these reactions a hydrogen ion is released - dehydrogenation or oxidation reaction- hydrogen ion has 2 electrons- hydrogen ions are rich in energy- can be used to form large quantities of ATP- takes place during oxidative phosphorylation- when H= is released it’s added to a molecule called a hydrogen carrier- good example- coenzyme NAD- by adding hydrogen with its 2 electrons to NAD - carry out a reduction reaction NAD + H —> NADH (reduced NAD)

Question 14

Glycolysis overview

Answer 14

At different stages, energy contained within glucose can be transferred to other molecules Energy transfer can take place in 2 different ways- in some reactions the energy transferred can be used to produce a molecule of ATP directly releasing energy- energy is used to form a molecule of ATP from ADP and Pi (substrate level phosphorylation) - Or hydrogen and 2 electrons can be removed from a molecule- (dehydrogenation/ oxidation - hydrogen and 2 electrons are transferred to a hydrogen carrier such as coenzyme NAD, forming reduced NAD- reduced NAD is then used used later to produce ATP in process called oxidative phosphorylation.

Question 15

Where does glycolysis take place + why

Answer 15

Glycolysis takes place in the cytoplasm and does not require oxygen Glycolysis consists of 10 different reactions but we learn a simplified version Initial stage of both aerobic and anaerobic respiration- occurs in cytoplasm as glucose can’t pass through mitochondrial membrane- but even if it could- enzymes for breakdown= not present in mitochondria- so glucose could not be metabolised

Question 16

Glycolysis- steps pt 1

Answer 16

glucose molecule is phosphorylated by addition of 2 phosphate groups using 2 molecules of ATP- ATP molecules each transfer 1 phosphate onto the glucose molecule- makes hexose diphosphate As a result- phosphorylated molecule= more reactive- less AE required for enzyme controlled reactions- also more polar than glucose= less likely to diffuse out of cell Hexose diphosphate converted to 2 molecules of triose phosphate- a 3 carbon sugar, glyceraldehyde-3- phosphate

Question 17

Glycolysis pt 2

Answer 17

Hydrogen is removed from the triose phosphate molecules- a dehydrogenation/ oxidation reaction- triose molecules oxidised to form pyruvate- this hydrogen is added onto NAD forming reduced NAD (hydrogen carrier molecule). - Also each phosphate group on triose phosphate is added to ADP, converting these molecules to ATP- so for each triose phosphate molecule 2 molecules of ATP is produced-4 ATP molecules produced overall- this is an example of substrate level phosphorylation- happens without redox reactions along electron transport chain- produces pyruvate

Question 18

Overall products of glycolysis

Answer 18

At start used 2 ATP molecules but produced 4 ATP molecules at end- net yield- 2 ATP Produced 2 reduced molecules of reduced NAD- will be used in a later stage of respiration called oxidative phosphorylation- if O2 available each has potential for synthesis of an additional 3 molecules of ATP- making 6 altogether from electron transport chain Released 2 molecules of Pyruvate Doesn’t seem to have released too much energy- because pyruvate still contains a great deal of energy- gradually released during later stages of respiration in krebs cycle- if O2 is available

Question 19

Link reaction- overview

Answer 19

What happens after glycolysis depends on amount of oxygen present- in absence of oxygen anaerobic respiration takes place in the cytoplasm If oxygen is present then cell carries out aerobic respiration- takes place in mitochondria- has a double membrane- internal region of a mitochondria= mitochondrial matrix

Question 20

Link reaction overview pt2

Answer 20

Pyruvate molecules produced by glycolysis are actively transported from cytoplasm into mitochondrial matrix- at this point the pyruvate molecules take part in the link reaction Link reaction formula Pyruvate + coenzyme A —> acetyl coenzyme A + carbon dioxide (at same time) NAD —> reduced NAD

Question 21

Link reaction- steps pt1

Answer 21

Pyruvate contains 3 C atoms - pyruvate now reacts with enzyme called coenzyme A- pyruvate molecule splits- A 2 C group is added to coenzyme A, forms acetyl coenzyme A- the remaining one carbon part of the pyruvate leaves as a molecule of CO2 At same time an oxidation reaction takes place- forms reduced NAD At end of a link reaction- got 3 products- one molecule of acetyl coenzyme A, one molecule of CO2, one molecule of reduced NAD

Question 22

Link- REMEMBER

Answer 22

REMEMBER- glycolysis produces 2 pyruvate molecules for each molecule of glucose- so the link reaction takes place twice for each molecule of glucose entering respiration- so produces 2x of each product

Question 23

Link- pt 3

Answer 23

Also- during link reaction a CO2 molecule is released from the pyruvate- when CO2 is removed from a molecule- called decarboxylation reaction Because we have oxidation alongside decarboxylation during link reaction- called oxidative decarboxylation Link reaction doesn’t require O2

Question 24

Krebs p1

Answer 24

The function of the Krebs cycle is a means of liberating energy from carbon bonds via reduced intermediates to provide ATP and reduced NAD (and reduced FAD), with the release of carbon dioxide Glucose has 6C atoms - during link reaction- 2 of those atoms have left as 2 CO2 molecules - remaining 4C atoms are now in 2 molecules of remaining acetyl coenzyme A Acetyl coenzyme A now enters next stage of respiration - Krebs cycle- takes place in the mitochondrial matrix Can divide krebs cycle into 2 main stages In 1st stage acetyl coenzyme A reacts with a 4 carbon molecule - the 2 carbon part of acetyl coenzyme A moves onto this molecule, creating a 6C molecule- at same time the coenzyme A and goes back to take part in the link reaction- 2nd stage- a whole series of chemical reactions takes place:

Question 25

Krebs p2

Answer 25

For 6C molecule- First a decarboxylation reaction releases 1 CO2 molecule and a dehydrogenation reaction produces a molecule of reduced NAD- now have 5C molecule Another dehydrogenation reaction takes place- produces 1 molecule of reduced NAD/ another decarboxylation reaction- produces 1 CO2 molecule- 1 molecule of ATP also produced during krebs cycle- produced through substrate level phosphorylation Finally 2 more dehydrogenation reactions- produces 1 molecule of reduced FAD and 1 molecule of reduced NAD- coenzyme FAD is a hydrogen carrier similar to NAD

Question 26

Krebs p3

Answer 26

Krebs pt 3 NOTE- during these reactions we regenerate our starting molecule (the 4 C molecule) via 6C and 5C intermediates.- allows krebs cycle to continue again When Kreb’s cycle operates once we make 1 molecule of ATP, 3 molecules of reduced NAD, 1 molecule of reduced FAD, also release 2 CO2 molecules. REMEMBER- 1 glucose molecule forms 2 pyruvate molecules in glycolysis So- per glucose- link reaction produces 2 molecules of acetyl coenzyme A- krebs cycle operates x2 the acetate fragment which entered the Krebs cycle from the glucose molecule is completely broken down to CO2 and water Note that H2O is fed in at three reactions. Krebs cycle does not require oxygen

Question 27

Coming up to oxidative phosphorylation- what's happened so far

Answer 27

So far in respiration created several molecules of reduced hydrogen carriers Next stage of respiration the reduced hydrogen carriers used to produce ATP- called oxidative phosphorylation Whole purpose of respiration is to generate ATP, However in reactions we’ve seen so far- only made net yield of 4 ATP molecules- per glucose- we produced a yield of 2 ATP molecules in glycolysis and 2 ATP molecules in 2 turns of Krebs cycle- These ATP molecules are formed by substrate level phosphorylation Also produced 12 molecules of reduced hydrogen carriers: 2 reduced NAD- glycolysis 2 reduced NAD link 6 reduced NAD, 2 reduced FAD- krebs

Question 28

Oxidative phosphorylation- start

Answer 28

When hydrogen carrier is reduced it gains a hydrogen ion and 2 electrons- 2 e’s contain a great deal of energy- used to create ATP in oxidative phosphorylation Inner mitochondrial membrane is folded into cristae- increases SA- inbetween 2 membranes we have inter membrane space On inner mitochondrial membrane- have 2 different sets of proteins- electron transport chain and ATP synthetase

Question 29

Oxidative phosphorylation- steps pt 1

Answer 29

On inner mitochondrial membrane- have 2 different sets of proteins- electron transport chain and ATP synthetase reduced NAD and reduced FAD deliver their pairs of hydrogen atoms to the electron transport system chain in the inner mitochondrial membrane- first protein is reduced 2 electrons then pass to 2nd protein- 1st protein now oxidised- 2nd reduced KEY NOTE- as electrons move down the electrons transport chain, the electrons lose energy- used by electron transport chain proteins to pump protons (hydrogen ions) from matrix into intermembrane space

Question 30

Oxidative phosphorylation- steps pt 2

Answer 30

Because inner membrane is impermeable to protons- protons build up in intermembrane space Electrons continue making way down chain in series of oxidation and reduction reactions- at each stage protons are pumped into the intermembrane space

Question 31

Oxidative phosphorylation- steps- pt 3

Answer 31

At the end the 2 electrons have transferred all of their energy These 2 electrons now combine with oxygen and 2 hydrogen ions (protons) to make a molecule of water equation= 2 e- + ½ O2 + 2H+ —> H2O

Question 32

Oxidative phosphorylation- steps pt4

Answer 32

Reduced FAD operates in the same way as reduced NAD- However, the electrons from reduced FAD enter the transport chain in the middle rather than the start As we said molecule of glucose generates 10 reduced NAD molecules and 2 reduced FAD molecules- so as a result of the electron transport chain, the concentration of protons is much greater in the intermembrane space than the matrix- proton gradient is now used to generate ATP

Question 33

Reaches ATP synthetase pt 1

Answer 33

Enzyme ATP synthase is found on inner mitochondrial membrane- contains an ion channel through centre Protons now diffuse down the gradient through the ion channel into the matrix- this movement of protons is used by ATP synthase to generate ATP from ADP and Pi- process is called chemiosmosis - ADP+Pi→ ATP+ H2O At end protons combine with electrons and oxygen to form water- O2 from blood- taken to cells

Question 34

Reaches ATP synthetase pt 2

Answer 34

Oxygen is described as the final (terminal) electron acceptor-essential as it removes protons and electrons- oxygen reduced by addition of hydrogen atoms and electrons to make water Cyanide is a non competitive inhibitor of the final carrier of the electron transport chain- in its presence electrons and protons can’t be transferred to water- accumulate and so electron transport chain no longer functions- proton gradient not maintained- ATP synthetase can’t produce ATP- cell dies quickly

Question 35

Oxidative phosphorylation - ATP products

Answer 35

Oxidative phosphorylation - ATP products : 38 ATPs per glucose molecule formed as follows: * net 2 ATPs in glycolysis (substrate-level phosphorylation) * 2 ATPs in the Krebs cycle (substrate-level phosphorylation) * 34 ATPs from oxidative phosphorylation (using chemiosmosis) from 10 reduced NAD (2 from glycolysis, two from the link reaction, six from the Krebs cycle) and 2 reduced FAD (Krebs cycle).

Question 36

Oxidative phosphorylation general products

Answer 36

ATP is the major product of oxidative phosphorylation, as it is the premier energy molecule of the cell. Oxidative phosphorylation also produces NAD+, FAD, and water.

Question 37

Anaerobic respiration

Answer 37

no oxygen to remove atoms from reduced NAD and make water- electron transport chain cannot function- no oxidative phosphorylation- no ATP formed- no O2- no reduced NAD can be reoxidised - no NAD regenerated to pick up more hydrogen consequently- link and Krebs can't take place- only glycolysis is possible

Question 38

Anaerobic respiration- how does glycolysis continue

Answer 38

For glycolysis to continue- pyruvate and hydrogen must be constantly removed and NAD must be regenerated Done how? Pyruvate accepts hydrogen from reduced NAD - 2 different anaerobic pathways to remove hydrogen from reduced NAD- both in cytoplasm

Question 39

2 anaerobic pathways- path1

Answer 39

In animals- muscle cells may not get sufficient O2 during vigorous exercise-when deprived of O2 pyruvate= hydrogen acceptor- converted to lactate- regenerating NAD- lactate can build in muscle cells or be transported to liver- converted back to glucose or stored as glycogen- if O2 later becomes available- lactate can be respired to CO2 and water- releasing energy it contains

Question 40

2 anaerobic pathways- path2

Answer 40

In various microorganisms eg yeast and in plant cells under certain conditions eg roots in waterlogged soils- pyruvate is converted o CO2 and to ethanal, a hydrogen acceptor- converted by decarboxylase- Ethanal is reduced to ethanol and NAD is regenerated in alcoholic fermentation ( a process in which some sugars (as glucose) are converted into alcohol and carbon dioxide by the action of various yeasts, molds, or bacteria or carbohydrate materials) pathway= irreversible- even if O2 becomes available again ethanol is not broken down- accumulates in cells- can rise to toxic concentrations

Question 41

Energy budget aerobic respiration

Answer 41

Energy budget aerobic respiration p 47- table shos how many H+ atoms and ATP molecules produced from 1 molecule of glucose- gives 2 turns of krebs cycle

Question 42

How many ATP molecules overall respired

Answer 42

38 overall per glucose molecule- theoretical total- cell is generally not this efficient as- - ATP used to move pyruvate, ADP, reduced NAD and reduced FAD across mitochondrial membrane -Proton gradient may become compromised by proton leakage across the inner mitochondrial membrane, rather than passing through ATP synthetase Molecules may also leak through membranes on average 30-32 ATP molecules tend to be produced

Question 43

Maths

Answer 43

If a mole of glucose is combusted in oxygen- produces 2880 kJ energy required to make ATP= 30.6 kJ/mol-1- if theoretical max is considered- a mole of glucose makes 38 moles of ATP- equivalent to 30.6x38= 1162.8 kJ therefore efficiency of ATP production= energy made through ATP/ energy released in combustion= 1162.8/2880x 100= 40.4%

Question 44

Anaerobic respiration- brief overview

Answer 44

Without ATP synthetase associated with the electron transport system- the only ATP formed is in glycolysis makes 2 molecules of ATP per molecule of glucose by substrate level phosphorylation- small compared to 38 molecules of ATP produced during aerobic-

Question 45

anaerobic more pt2

Answer 45

in anaerobic pyruvate not transferred to the mitochondria but is converted in the cytoplasm- to ethanol in plants or lactate in mammals-2H released in conversion of glucose to pyruvate reduces NAD - given up again in formation of ethanol in plant cells or lactate in animal cell- many different metabolic pathways have been identified in bacteria or archaea- many organic acids and alcohols produced by their fermentation

Question 46

anaerobic respiration- maths

Answer 46

Efficiency of ATP production= energy made available through ATP/ energy released in combustion x100= 30.6x2/2880x100=2.1% much less efficient

Question 47

Alternative respiratory pathways

Answer 47

Kreb's cycle- sometimes called metabolic hub as the Metabolic pathways of carbohydrates, lipids and proteins can feed into it and in some situations fats and proteins can be used as respiratory substrates - Acetyl Coenzyme A is a most significant molecule as it links the metabolism of the three types of macromolecule

Question 48

Lipid pathways

Answer 48

Triglyceride molecule has 2 parts-3 carbon glycerol part and on right - 3 fatty acids- fatty acids and glycerol= joined by 3 ester bonds- when triglycerides are digested - ester bonds= hydrolysed- release glycerol and fatty acid molecules- 3 carbon glycerol is converted to triose phosphate, an intermediate of glycolysis- converted to pyruvate - enters link reaction and krebs cycle as previously seen

Question 49

Lipids pt 2 electric boogaloo

Answer 49

fatty acid molecules broken down into 2 carbon units eg O H H H || | | | C C- C - C | | | | H H H H Start of a fatty acid chain- 2 units here (2C acetate fragments) - fed into the Krebs cycle as acetyl co-enzyme A;

Question 50

Lipids pt 3

Answer 50

Acetyl coenzyme A now enters the krebs cycle- fatty acids contain great amount of carbon to hydrogen bonds- forms very large number of acetyl coenzyme A molecules- so triglycerides contains great amount of energy- more than glucose

Question 51

Protein- aerobic respiration pathway

Answer 51

First protein must be hydrolysed to its individual amino acids during digestion- all proteins have an amino group- in first stage- amino group is removed- called deamination- carbon part of amino acid is then processed (entirety that isn't N-H-H)-

Question 52

Protein- aerobic respiration pathway- pt 2

Answer 52

proteins are hydrolysed into their constituent amino acids, which are deaminated in the liver, forming a keto acid and ammonia; * Some keto acids are fed into glycolysis (e.g. pyruvate) and some others are fed into the Krebs cycle.energy value of proteins is approx same as carbs