Respiration Flashcards
Why organisms need energy
-Active transport
-exocytosis/endocytosis
-synthesis of molecules eg. proteins
-DNA replication
-cell division
-movement
-activation of chemicals
Role of ATP
-standard intermediary between energy releasing reactions eg. respiration and energy consuming reactions eg. active transport
-energy produced in respiration is used to synthesise ATP from ADP + Pi which can release the energy when needed
-universal energy currency as occurs in all living cells and is a source of energy that can be used by cells in small amounts
Structure of ATP
-adenine bonded to ribose sugar
-ribose bonded to 3 phosphates by phosphodiester bond
-3 phosphates bonded to each other by phosphoanhydride bonds
4 stages of respiration
-glycolysis
-link reaction
-Krebs cycle
-oxidative phosphorylation
Glycolysis
- 2ATP hydrolysed to 2ADP + 2Pi. 2Pi added to glucose to make hexose biphosphate
-this splits into triose phosphate
-Pi in cytoplasm is added to triose phosphate to produce triose biphosphate - 2ADP removes the Pi from the triose biphosphate
-dehydrogenase enzymes, aided by coenzyme NAD, remove hydrogens from triose biphosphate
-the NAD accepts hydrogens and is reduced
-this changes the structure of the triose sugar, forming 2pyruvate for every one glucose molecule
Products from glycolysis
-Net gain of 2 ATP
- 2 reduced NAD
-2 pyruvate for link reaction and Kreb cycle
How pyruvate is transported
-transported across mitochondrial envelope via pyruvate/H symport, which is a transporter protein that transports 2 molecules in the same direction
Where the link reaction and Krebs cycle takes place
mitochondrial matrix
Link reaction
- carboxyl group (COOH) is removed from pyruvate producing CO2
- this decarboxylation together with dehydrogenation produces acetyl group
- the dehydrogenation of pyruvate reduces NAD
- acetyl group combines with CoA producing acetyl CoA
2pyruvate + 2NAD + 2CoA -> 2CO2 + 2 reduced NAD + 2 acetyl CoA
-No ATP is produced
Krebs cycle
-acetyl group (2C) from acetyl CoA combines with oxaloacetate (4C) to form citrate (6C)
-citrate decarboxylated and dehydrogenated, producing 5C compound, CO2 and reduced NAD
-5C compound is decarboxylated and dehydrogenated producing 5C compound, CO2 and reduced NAD
-4C compound temporarily combines with CoA and then released. This is substrate level phosphorylation and produces ATP
-4C compound dehydrogenated producing different 4C compound and reduced FAD
-atoms in 4C compound are rearranged by enzyme isomerase, followed by dehydrogenation, to regenerate oxaloacetate
Other substances that can be respired aerobically
-fatty acids, broken down to acetate which enters Krebs cycle via acetyl CoA
-glycerol converted to triosphosphate
-amino acids deaminated and enters the cycle directly or changed to pyruvate or acetyl CoA
Oxidative phosphorylation
-red. NAD and FAD reoxidised when they deliver H to electron transport chain
-H split into proton and electron
-protons go into solution of mitochondrial matrix
-electrons pass through electron carriers (Fe) which are reduced and reoxidised producing energy
-energy is used to pump protons from matrix into intermembrane space
-proton gradient generates chemiosmotic potential/ proton motive force
-protons can’t diffuse through bilayer easily as outer membrane has low permeability and inner membrane impermeable
-this means protons diffuse through ATP synthase, causing a conformational shape and the formation of ATP
-oxygen final electron acceptor as combines with electrons from transport chain and protons producing water
4H+ + 4e- + o2 -> 2H2O
Oxidative phosphorylation definition
formation of ATP using energy released from electron transport chain in the presence of oxygen
How many molecules of ATP produced, why theoretical yield hardly achieved
-oxidative phosphorylation produces 28ATP
-glycolysis produces 2ATP
-total 32 ATP
-some ATP used to actively transport pyruvate from cytoplasm to matrix
-some ATP used to transport red. NAD into mitochondria
-some protons leak out through outer mitochondrial membrane
Chemiosmosis definition
flow of protons, down conc. gradient, across a membrane, through ATP synthase
Mitochondria structure
-inner and outer membrane making envelope
-inner membrane folded into cristae for large SA
-in inner membrane there’s electron transport system and ATP synthase
-between 2 membranes is the intermembrane space
-inner membrane impermeable to protons
-outer membrane partially permeable
Matrix contains
-enzymes to catalyse stages of reactions
-NAD + FAD
-oxaloacetate
-mitochondrial DNA
-mitochondrial ribosomes
Respiration in absence of oxygen
-oxygen can’t be final electron acceptor, so protons can’t combine with electrons and oxygen to produce water
-the conc. of H+ in matrix increases, reducing proton gradient
-oxidative phosphorylation stops
-red. NAD and FAD can’t donate H atom and be reoxidised
-therefore stopping krebs cycle and link reaction
Anaerobic respiration in plants and fungi
Yeast fermentation pathway
-pyruvate is decarboxylated by pyruvate decarboxylase to produce ethanal
-ethanal accepts H atoms from red. NAD forming ethanol catalysed by ethanol dehydrogenase
-in the process red. NAD is reoxidised and therefore can accept more H from glycolysis
Anaerobic respiration in animals
Lactate fermentation pathway
-pyruvate accepts H from red. NAD
-this is catalysed by lactate dehydrogenase producing lactate
-reoxidised NAD can accept more H from glycolysis
Fate of lactate
-convert to pyruvate to enter link reaction
-recycled to glucose and glycogen
ATP produced from anaerobic respiration
-ethanol and lactate fermentation don’t produce ATP, they only allow glycolysis to continue
-as only glycolysis is occurring, only a net gain of 2ATP
Respiratory substrate-
-organic substance that can be oxidised by respiration, releasing energy to synthesise ATP
Glucose as respiratory substrate
-chief respiratory substrate
-RBC and brain cells only respire using glucose
-glucose is produced by hydrolysing disaccharides or monosaccharides eg. fructose can be changed into glucose via isomerase
How lipids are respired
-triglycerides are hydrolysed into glycerol and fatty acids
-glycerol converted to triose phosphate to enter glycolysis
-fatty acids combine with coenzyme A
-fatty acid- CoA complex is transported to matrix, where its broken down into 2 acetyl groups with CoA attached
-this is a beta oxidation pathway and produces red. NAD+FAD
-acetyl groups released from CoA and enter krebs cycle
How proteins are respired
-proteins are digested and excess amino acids deaminated in the liver
-this involves removal of amine group which is converted to urea
-the rest of the amino acid is now a keto acid and enters as pyruvate, acetyl CoA or krebs cycle acid eg. oxaloacetate
-where the amino acid enters depends on the R group
When proteins are respired
-last resort, when no more glucose or fatty acids
eg. starvation, fasting, prolonged exercise
Energy values of respiratory substrates
-fatty acids produce most energy
-this is because there’s more H which can split into H+ + e-
-this means more protons for chemiosmosis, so more ATP synthesised
Respiratory quotient
RQ= CO2 produced/ O2 consumed
eg. C6H12O6 + 6O2 -> 6CO2 + 6H20 6/6=1
-if RQ is greater than 1, some anaerobic respiration must be occurring as more CO2 is produced (during glycolysis) than O2 being consumed (during oxidative phosphorylation)
Glucose = 1
fatty acid= 0.7
amino acid= 0.8-0.9
Using a haemocytometer
-add coverslip horizontally onto the slide and press down
-place pipette tip at entrance to groove and allow liquid to fill chamber
-place onto microscope stage and leave for 5 mins
-count how many cells are in the 4 corner squares and middle square
-include cells touching left or top line, but not ones touching right or bottom lines
-calculate volume- 0.2x0.2x0.1 =0.004 per 1 sqaure
-5 squares= 0.02 mm3
Investigation into rate of reproduction of yeast cells in aerobic and anaerobic conditions, prediction, method, things to be aware of
-in oxygen yeast will produce more ATP so have more energy for reproduction
method:
-add cider and yeast to beaker
-cover with cloth to prevent contamination
-leave in a warm place for a week
-place into a haemocytometer and count cells
Aware:
-if oxygen becomes available yeast will break down ethanol into acetyl CoA which will enter the krebs cycle
-if alcohol concentration increases too high, yeast cells will be killed
Set up of respirometer
-place coloured liquid into manometer tube
-find mass of organisms and add equal mass of glass beads to other test tube containing soda lime
-place in water bath for 10 mins
-mark the place of manometer fluid
-close taps and leave for time period eg. 10 mins
-measure change in level of manometer fluid, which is equal to vol of oxygen consumed
Calculate volume of oxygen from respirometer
-find change on levels of manometer fluid
-multiple by area of tube (πr2)
-divide by time taken to find vol of oxygen absorbed per min
or
-how much you pushed the syringe to move manometer fluid back to start point
