respiration
aerobic respiration
four stages of aerobic respiration
glycolysis, link reaction, krebs cycle and oxidative phosphorylation
oxidative phosphorylation, link reaction and krebs cycle take place in mitochondria, glycolysis takes place in cytoplasm
stage 1- glycolysis
occurs in cytoplasm
first stage in both aerobic and anaerobic respiration
1) phosphorylation
glucose is phosphorylated by adding 2 phosphates from 2 molecules of atp
this produces 1 molecule of hexose bisphosphate and 2 molecules of adp
then hexose bisphosphate is split into 2 molecules of triose phosphate
2) oxidation
triose phosphate is oxidised (loses hydrogen) top form 2 molecules of pyruvate ( which is actively transported into mitochondria) for link reaction)
NAD collects hydrogen ions forming red nad
4 atp are produced, net gain of 2 atp
stage 2- link reaction
takes place in mitochondrial matrix
2 pyruvate is decarboxylated (one carbon atom is removed) in form of CO2 catalysed by pyruvate dehydrogenase
2 nad is reduced to 2 red nad and collects hydrogen from pyruvate converting it into acetate
acetate is combined with 2 CoA to form 2 acetyl CoA
no atp is produced
occurs twice for every glucose molecule (2 molecules of acetyl CoA, 2 CO2, 2 red nad
stage 3- krebs cycle
acetyl group from acetyl CoA is combined with oxaloacetate to produce citrate catalysed by citrate synthase
CoA goes back to link reaction
the 6C citrate molecule is converted to a 5C molecule via decarboxylation releasing CO2, dehydrogenation occurs releasing hydrogen which reduced nad to red nad
the 5C molecule is then converted to a 4C molecule via decarboxylation and dehydrogenation producing one molecule of red fad and 2 red nad (NO, NO AND FUCKING NO)
atp is produced by direct transfer of phosphate group from an intermediate compound to adp (substrate level phosphorylation) citrate has been converted to oxaloacetate via isomerase enzyme
stage 4- oxidative phosphorylation
takes place in inner mitochondrial membrane
hydrogen atoms are released from red nad and red fad when they are oxidised. the h atoms split into H+ ions (protons) and e-
the electrons move down electron transport chain losing energy at each carrier (each has a iron ion which is reduced and oxidised)
this energy is used by the electron carriers to pump proton from the inner mitochondrial membrane into the intermembrane space until the conc of H+ ions is higher in intermembrane space forming an electrochemical gradient and a chemiosmotic potential
protons move back down electrochemical gradient back into mitochondrial matrix via atp synthase which causes the synthesis of atp from adp and an inorganic phosphate
this process is called chemiosmosis
at the end of the chain O2, H+ and e- combine to form water
anaerobic respiration and rqs
2 types- lactate and alcoholic fermentation
lactate fermentation
reduced nad from glycolysis transfers hydrogen to pyruvate to form lactate and nad catalysed by lactate dehydrogenase
nad is reoxidised reused in glycolysis even when there isn't much oxygen
too much lactate is toxic and is removed from cells into blood to liver where it undergoes glycogenesis to produce glucose or converted to pyruvate when more oxygen present
alcoholic fermentation
CO2 is removed from pyruvate to form ethanal (decarboxylated) catalysed by pyruvate decarboxylase which has thiamine diphosphate coenzyme
red nad transfers hydrogen to ethanal to produce ethanol and nad catalysed by ethanol dehydrogenase
nad is reoxidised and reused in glycolysis
anaerobic respiration produces less energy than aerobic respiration
anaerobic respiration only has one energy releasing stage (glycolysis) as all other reactions need oxygen
cells can respire glucose, carbohydrates, lipids and proteins
lipids have highest energy value (39.4) then proteins (17)then carbohydrates (15.8)
most energy is produced in OP which requires red nad, red fad and hydrogen atoms this means respiratory substrates that contain more hydrogen atoms cause more atp to be produced and respired
rq= volume of CO2 released/ volume of O2 consumed (if value is >1 it indicates some anaerobic respiration is occurring)
need for cellular respiration
processes requiring energy= active transport, endocytosis, exocytosis, synthesis of large molecules e.g. collagen, enzymes and antibodies, dna replication, cell division, movement (flagella and cilia/undulipodia, activation of chemicals
anabolic reactions= when large molecules are made from small molecules
catabolic reactions= when small molecules are made from large molecules
role of ATP
ATP is the standard intermediary between energy releasing and energy consuming metabolic reactions in cells
ATP= adenine, ribose and 3 phosphate groups
ATP is stable in solution (doesn't break down to ADP and pi) but is hydrolysed in enzyme catalysis
when ATP is hydrolysed a small quantity of energy is released e.g. heat used for maintaining body temp/warmth or energy which can be used for other processes in cell
ATP + H2O---> ADP + Pi. -30.5 kj mol-1
ADP + H2O--> AMP + Pi. -30.5 kj mol-1
AMP + H2O---> adenosine + pi. -13.8 kj mol-1
catalysed by dehydrogenase enzymes
link, Krebs and OP are NOT IN ANAEROBIC RESPIRATION
Mitochondria structure
2-5 ym long
outer membrane= made out of phospholipids, contains proteins (channels/ carriers) to transport molecules into mitochondria
inner membrane= lipid composition( not phospholipid),bilayer is less permeable to small ions than outer membrane, cristae (folds) increase SA for electron carriers and ATP synthase
intermembrane space= involved in OP, Inner membrane in close contact with mitochondrial matrix so red NAD and FAD can easily deliver H+ to electron transport chain
electron transport chain= each electron carrier protein contains a COFACTOR a non protein ham group which contains iron ion, iron ion can accept and donate electrons as it becomes reduced and oxidised (oxide-reductase enzymes), have a COENZYME which pumps H+ from matrix to inter membrane space creating conc gradient causing H+ to diffuse through ATP synthase to generate ATP
ATP synthase enzyme= H+ ions pass through them generating ATP
fatty acids, glycerol and amino acids can be respired also
28 ATP made per molecule of glucose in OP, 2 in Krebs, 2 in glycolysis, 0 in links= 32 in total (yield may be lower as some ATP is used for: actively transporting pyruvate and red NAD into mitochondria, some H+ may leak out of outer membrane
if no oxygen
no oxygen for protons and electrons to combine with at end of OP
conc of protons in matrix increases in matrix and reduces gradient
OP stops
red NAD and FAD are not reoxidised
krebs and links stops
yield of 2 ATP in anaerobic respiration (lactate and ethanol fermentation produce no ATP, the ATP comes from glycolysis)
carbohydrates= main is glucose, disaccharides can be digested to monosaccharides for respiration, monosaccharides e.g. fructose can be changed by isomerase enzyme into glucose
lipids= glycerol can be converted to TP and then respired, each fatty acid is combined with a CoA from energy ATP--> AMP to form fatty acid-CoA complex which is transported into mitochondrial matrix and broke down into 2 carbon acetyl CoA, this beta oxidation pathway generates red NAD and FAD, acetyl groups are released from CoA and enter Krebs combining with oxaloacetate
proteins= after deamination keto acid enters Krebs as acetyl coA or pyruvate
respiromoter
sodium hydroxide/ soda lime absorbs CO2 produced then only volume change is due to oxygen conc absorbed
method
1) after placing methylene blue into manometer tube , the apparatus is connected with taps open enabling air to escape
2) measure mass of organism
3) with taps open and organism inside place set up into water bath for 10 mins
4) the level on syringe should be recorded
5) the levels of coloured liquid should be marked using pen
6) taps are closed and set up is left for 10 mins
7) the change in level of fluid is measured and measure the conc of oxygen absorbed
8) calc volume absorbed per min per gram of organism
effect of temp= using different temps at fixed intervals
effect of substrate conc= different concs of glucose placed in tubes