respiration Flashcards
respiration is the process that….
occurs in living cells and release the energy stored in organic molecules such as glucose
why do living organisms need energy
- active transport
- endocytosis
- exocytosis
- synthesis of large molecules
- DNA replication
- cell division
- movement
- activation of chemicals
what are the two types of metabolic reactions
anabolic and catabolic
describe anabolic reactions
are metabolic reactions where large molecules are synthesised from smaller molecules
describe catabolic reactions
are metabolic reactions involving the hydrolysis of larger molecules to smaller ones
within living cells atoms, ions and molecules have ? and this allows them to move
kinetic energy
what is the role of ATP/ structural functions
atp is the standard intermediary between energy releasing and energy consuming metabolic reactions
small stable soluble easily moves breaks down and release energy universal
describe ATP structure
is a phosphorylated nucleotide
each molecule of ATP consists of adenosine which is a nitrogenous base adenine plus the five carbon sugar ribose and a three phosphate groups .
define glycolysis
first stage of respiration, a 10 stage metabolism pathway that converts glucose to pyruvate
what are the three main stages of glycolysis
phosphorylation of glucose to hexose bisphosphate (atp to adp+p)
splitting each hexose bisphosphate molecule into two triose phosphate molecules
oxidisation of triose phosphate to pyruvate
what is NAD short for
nicotinamide adenine dinucleotide
what is NAD
is a non protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions, NAD oxidises substrate molecules during glycolysis , the link reaction and krebs cycle
structure of NAD
nicotinamide
5 carbon sugar ribose
nucleotide base adenine
2 phosphoryl groups
in the three stages of glycolysis , describe phosphorylation
glucose is a hexose sugar , which means it contains six carbon atoms . its molecules are stable and need to be achieved before they can be split into two three carbon compounds
1-one molecule of ATP is hydrolysed and the released phosphoryl group is added to glucose to make hexose monophosphate
2-another molecule of ATP is hydrolysed and the phosphoryl group added to the hexose phosphate to from a molecule of hexose bisphosphate. this sugar has one phosphate group at carbon atom number one and another at carbon atom 6
the energy from the hydrolysed ATP molecules activates the hexose sugar and prevents it from being transported out of the cell
glycolysis steps
glucose
glucose -p
hexose bisphosphate
2x triose phosphate
2x pyruvate
what are the products of glycolysis
- two molecules of ATP
- two molecules of reduced NAD
- two molecules of pyruvate
the stages of respiration
- glycolysis
- link reaction
- kerb cycle
- oxidative phosphorylation
in the three main stages of glycolysis
describe the splitting of hexose bisphosphate
each molecule of hexose bisphosphate is split into two three carbon molecules , triose phosphate , each with a phosphate group attached
in the three main stages of glycolysis describe oxidation of triose phosphate to pyruvate
although this process is anaerobic it involves oxidation , because it involves the removal of hydrogen atoms from substrate molecules
1- dehydrogenase enzymes ,aided by the coenzyme NAD , remove hydrogens form triose phosphate
2- the two molecules of NAD accept the hydrogen atoms (protons and electrons ) and become reduced
3-at this stage of glycolysis , two molecules of NAD are reduced for every molecule of glucose undergoing this process. also at this stage, four molecules of ATP are made for every two triose phosphate molecules undergoing oxidation
how the structure of the mitochondria enables them to carry out their functions
- the matrix
is where the link reaction and the kerb cycle takes place, it contains
- enzymes that catalyse the stages of these reactions
- molecules of the coenzymes NAD and FAD
- oxaloacetate , the four carbon compound that accepts the acetyl groups from the link reaction
- mitochondrial DNA , some of which codes for mitochondrial enzymes and other proteins
- mitochondrial ribosomes , structurally similar to prokaryotic ribosomes where these proteins are assembled
how the structure of the mitochondria enables them to carry out their functions
-the outer membrane
the phospholipid composition of the outer membrane is similar to that of membranes around other organelles in eukaryotic cells it contains proteins, some of which form channels or carriers that allow the passage of molecules , such as pyruvate into the mitochondria
how the structure of the mitochondria enables them to carry out their functions
-the inner membrane
the lipid composition of the inner membrane differs from that of the outer membrane . this lipid bilayer is less permeable to small ions such as hydrogen ions (protons ) than is the outer membrane . the folds , cristae , the inner membrane gives a large surface area for the electron carriers and ATP synthase enzymes embedded in them
the electron carriers are proteins complexes arranged in electron transport chains . electron transport chains are involved in the final stage of aerobic respiration , oxidative phosphorylation
how the structure of the mitochondria enables them to carry out their functions
-the intermembrane space
the inter membrane space between the outer and inner layer of the mitochondrial envelope is also involved in oxidative phosphorylation
the inner membrane is in close contact with the mitochondrial matrix, so the molecules of reduced NAD and FAD can easily deliver hydrogens to the electron transport chain
how the structure of the mitochondria enables them to carry out their functions
-electron transport chain
each electron carrier protein contains a cofactor -a non protein haem group that contains an iron ion
the iron ion can accept and donate electrons , because it can become reduced by gaining an electron and then become oxidised when donating the electron to the next electron carrier. electron carrier proteins are oxido-reductase enzymes
the electron carier also have a coenzyme that………
describe the ATP synthase enzymes
are large and protrude from the inner membrane into the matrix. protons can pass through them
define decarboxylation
removal of a carboxyl group from a substrate molecule
define dehydrogenation
removal of hydrogen atoms from a substrate
define substrate level phosphorylation
production of ATP from ADP and P during the glycolysis and the kerb cycle
describe pyruvate
pyruvate is produced during glycolysis is transported across the outer and inner mitochondrial membranes via a specific pyruvate -H+ symport, a transport protein that transports that transports two ions or molecules in the same direction , and into the matrix then
1- pyruvate is converted to a two carbon acetyl group during the link reaction
2- the acetyl group is oxidised during the kerb cycle
describe the link reaction
1-Pyruvate(X2) is produced in the cytoplasm by glycolysis
2-It is moved by active transport into the mitochondrial matrix
3-A series of chemical changes occur:
4-decarboxylation (CO2 removed) by pyruvate decarboxylase
5-Dehydrogenation (H removed) by pyruvate dehydrogenase
6-An Acetyl group (2C) is produced which reacts with Coenzyme A to form Acetyl CoA
7-Acetyl CoA is the end product of the Link Reaction and is needed for the next stage of cell respiration: Krebs cycle
what are the products from the link reaction
2x reduced NAD
2X carbon dioxide
0 ATP
0 reduced FAD
describe the kerb cycle
1-pyruvate (3C) is decarboxylated( loss of CO2) and dehydrogenated ( loss of reduced NAD) to form acetyl CoA (2C)
2-the acetyl group released from acetyl CoA combines with a four carbon compound, oxaloacetate to form a six carbon compound citrate
3-citrate is decarboxylated and dehydrogenated , producing a five carbon compound , one molecule of carbon dioxide and one molecule of reduced NAD
4-this five carbon compound is further decarboxylated and dehydrogenated , producing a four carbon compound , one molecule of carbon dioxide and one molecule of reduced NAD
5-this four carbon compound combines temporarily with , and is then released from coenzyme A . at this stage , substrate level phosphorylation takes place , producing one molecule of ATP
6-the four carbon compound is dehydrogenated , producing a different four carbon compound and a molecule of reduced NAD
7- rearrangement of the atoms in the four carbon molecule , catalysed by an isomer enzyme , followed by further dehydrogenation , regenerate a molecule of oxaloacetate so the cycle can continue
For every molecule of glucose there are two turns of the kerb cycle
where does the link cycle take place
mitochondrial matrix
where does the kerb cycle take place
mitochondrial matrix
what are the products of the kerb cycle
6x reduced NAD
2x reduced FAD
4x carbon dioxide
2x ATP
other substances besides glucose can be respired aerobically , for example
- fatty acids are broken down to many molecules of acetate that enter the kerb cycle via acetyl coA
- glycerol may be converted to pyruvate and enter the kerb cycle via the link reaction
- amino acids may be deaminated and the rest of the molecule can enter the krebs cycle directly or be changed to pyruvate or acetyl coA
describe Oxidative phosphorylation
1-reduced NAD is split into electrons and protons
2-the electron atoms pass along the chain of electron carriers , each carrier protein has an iron ion
3- as electrons pass along the chain , some of their energy is used to pump protons across the inner mitochondrial membrane into the inter membrane space
4-as protons accumulate in the intermembrane space, a proton gradient forms
5-the proton gradient generates a chemiosmotic potential
6-the protons then diffuse through the protein channels associated with ATP synthase enzymes that are in the inner membrane
7-this allows ADP+P to form ATP
8-oxygen is the final electron acceptor . it combines with electrons coming off the electron transport chain and with the protons, diffusing down the ATP synthase channel, forming water
where does Oxidative phosphorylation take place
mitochondria , folded cristae
what are the products of Oxidative phosphorylation
28x ATP
why is the theoretical yield rarely achieved
- some ATP is used to actively transport pyruvate into the mitochondria
- some ATP is used in a shuttle system that transports reduced NAD , made during glycolysis , into mitochondria
- some protons may leak out through the outer mitochondrial membrane
respiration in the absence of oxygen
what happens if oxygen is absent
1- oxygen cannot act as a final electron acceptor at the end of oxidative phosphorylation . protons diffusing through channels associated with ATP synthase are not able to combine with electrons and oxygen to form water
2- the concentration of protons increases in the matrix and reduces the proton gradient across the inner mitochondrial membrane
3- oxidative phosphorylation ceases
4-reduced NAD and reduced FAD are not able to unload their hydrogen atoms and cannot re-oxidised
5- the kerb cycle stops and so does the link reaction
eukaryotic cells have two metabolic pathways to reoxidise the reduced NAD , what are they and where do they take take
1- fungi such as yeast and plants use the ethanol fermentation pathway
2- mammals use the lactate fermentation pathway
both take place in the cytoplasm
describe the ethanol fermentation pathway
1- each molecule of pyruvate produced during glycolysis is decarboxylated and converted to ethanal , this stage in the pathway is catalysed by pyruvate decarboxylase
2- the ethanal accepts hydrogen atoms from reduced NAD , becoming reduced to ethanol . the enzyme ethanol dehydrogenase catalyses the reaction
3- in the process, the reduced NAD is re-oxidised and made available to accept more hydrogen atoms from triose phosphate , thus allowing glycolysis to continue
when does the lactate fermentation pathway occur
occurs in mammalian muscle tissue during vigorous activity , such as when running fast to escape a predator, when the demand for ATP for muscle contraction is high and there is an oxygen deficit
describe the lactate fermentation pathway
1- pyruvate , produced during glycolysis , accepts hydrogen atoms from the reduced NAD , also made during glycolysis . the enzyme lactate dehydrogenase catalyses the reaction . there are two outcomes
- pyruvate is reduced to lactate
- the reduced NAD becomes reoxidised
2- the reoxidised NAD can accept more hydrogen atoms from triose phosphate during glycolysis , and glycolysis can continue to produce enough ATP to sustain muscle contractions for a short period
describe the fate of lactate
the lactate produced in the muscles tissue is carried away from the muscles, in the blood, to the liver. when more oxygen is available , the lactate may be either
1- converted to pyruvate , which may enter the kerb cycle via the link reaction
2- recycled to glucose and glycogen
if lactate were not removed from the muscle tissues, the PH would be lowered and this would inhibit the action of many of the enzymes involved in glycolysis and muscle contractions
describe the ATP yield from anaerobic respiration
neither ethanol fermentation or lactate fermentation produces any ATP . however because this still allows glycolysis to continue , the net gain of two molecules of ATP per molecule of glucose is still obtained
because the glucose is only partly broken down , many more molecules can undergo glycolysis per minute , and therefore the overall yield of ATP is quite large. however for each molecule of glucose, the yield of ATP via anaerobic respiration is about 1/15 of that produced during aerobic respiration
describe the investigation used to measure the rate of reproduction of yeast cells under aerobic and anaerobic conditions
1- pour 50 cm3 of cider into each of the conical flasks
2- using a pipette , add one drop of yeast suspension to each conical flask
3- place four layer of muslin or cheesecloth over the mouth of each conical flask and secure with an elastic band . this allows oxygen to enter the flask , but keeps out dust and contaminants
4-leave the flask in a warm place for about a week
5- mix the contents of each flask thoroughly . by using a pipette , withdraw some of the flasks contents and place a drop on to a haemocytometer slide with its coverslip in place
6- count the number of yeast cells in the centre square and each corner square
7- each of the 5 squares where you counted ,contained 16 smaller squares . so you counted cells in 80 very small squares , having a total volume of 0.02mm3, if you multiply the cell count you obtained by 50000 you will find the number of yeast cells per cm3
8- carry out three counts for each size of flask . calculate the mean number of yeat cells per cm3 for each flask
9- tabulate a graph of your data
other ways to compare aerobic and anaerobic respiration in yeast
the rate of respiration can be measured by measuring the rate of evolution of carbon dioxide . as carbon dioxide dissolved in the culture medium it lowers the PH , and this can be measured using a PH meter
define respiratory substrate
an organic substance that can be oxidised by respiration , releasing energy to make molecules of ATP
describe the energy values of different respiratory substrate
- CARBOHYDRATES
the monosaccharide glucose is the chief respiratory substrate. some mammalian cells, for example brain cells and red blood cells , can use only glucose for respiration. animals and some bacteria store carbohydrates as glycogen, which can be hydrolysed to glucose for respiration . plant cells store carbohydrates as starch, and this can also be hydrolysed to glucose for respiration
- disaccharides can be digested to monosaccharides for respiration
- monosaccharides such as fructose and galactose can be changed by isomerase enzymes to glucose for respiration
describe the energy values of different respiratory substrate
-LIPIDS
lipids are important respiratory substrates for a number of types of tissue, including muscle. triglycerides are hydrolysed by lipase to glycerol and fatty acids. glycerol can then be converted to triose phosphate and respired
-fatty acids are long chain hydrocarbons with a carboxylic acid group. hence in each molecule there are many carbon atoms , many hydrogen atoms and very few oxygen atoms. these molecules are a source of many protons for oxidative photophosphorylation , and so fats produce much more ATP than an equivalent mass of carbohydrates
describe the energy values of different respiratory substrate
- PROTEINS
excess amino acids , released after the digestion of proteins , are deaminated in the liver . deamination of an amino acid involves removal of the amino group and its subsequent conversion to urea that is removed via the kidney . the rest of the amino acid molecule , a keto acid enters the respiratory pathway as pyruvate , acetyl CoA or a kerb cycle acid such as oxaloacetic acid
during fasting, starvation or prolonged exercise, when insufficient glucose or lipid are available for respiration, protein from muscles can be hydrolysed to amino acids which are then respired . these amino acids may be converted to pyruvate or acetate and enter krebs cycle
what are the mean energy value of
- carbohydrates
- lipids
- protein
c= 15.8 l= 39.4 p= 17
how do you calculate respiratory quotient
co2 produced / o2 consumed
what are the RQ values of
- glucose
- fatty acids
- amino acids
=1
=0.7
=0.8
describe the principle of using a respirometer
- if the carbon dioxide produced is absorbed by sodium hydroxide solution or solid soda lime , then the only volume change within the respirometer is due to the volume of oxygen absorbed by the organisms
- if oxygen is absorbed from the tube containing the organisms , then that tube has a reduced volume of air in it, exerting less pressure than the greater volume of air in the other tube. as a result the coloured liquid in the manometer tube rises up towards the respirometer tube
- if the original level of liquid in the manometer tube is marked and the radius of the bore in the capillary tube is known , the volume of oxygen absorbed during a specific period can be calculated
- to reset the apparatus , the syringe is depressed to inject air into the system and reset the liquid in the manometer tube back to its original position . this also allows the reading of the volume of oxygen absorbed by noting the change in level of the syringe plunger, as measured from the graduated scale on the syringe barrel
describe the setting up the of apparatus of the respirometer
1- after placing the coloured liquid , into the manometer tube, the apparatus is connected with the taps open . this enables the air in the apparatus to connect with the atmosphere
2- the mass of living organisms to be used should be found
3- with the taps still open the whole set up, with the living organisms in place, is placed in a water bath for at least 10 minutes until it reaches the temperature of the water bath
4- the syringe plunger should be near the top of the scale on the syringe barrel and its level noted
5-the level of coloured liquid in the manometer tubes can be marked with a felt tip pen
6- the taps are closed and the apparatus left in the water bath for a specific period, such as 10 minutes
7- the change in the level of manometer liquid can be measured , and the syringe barrel depressed to reset the apparatus . this also enables you to measure the volume of oxygen absorbed
8- you can then calculate the volume of oxygen absorbed per minute per gram of living organisms
describe measuring the effect of temperature in relation to the respirometer
the effect of temperature on the rate of respiration can be investigated using the respirometer . three readings should be taken at each temperature . in-between each temperature reading, the apparatus and organisms should be allowed to adjust to the new temperatures
animal species should only be used from temperatures from 10-40 degrees , for more extreme temperatures , fungal material should be used
describe the investigation of the effect of substrate concentrations on the rate of respiration in yeast
the respirometer may be used so that a suspension of yeast , with differing concentrations of glucose solutions, is placed in one of the tubes. if the sodium hydroxide solution is omitted , the evolution of carbon dioxide during a specific period can be measured
describe the energy values of different respiratory substrate
-LIPIDS- 4 steps
1- with the aid of some energy from the hydrolysis of one molecule of ATP to AMP, each fatty acid is combined with coenzyme A
2- the fatty acid CoA complex is transported into the mitochondrial matrix , where it is broken down into two carbon acetyl groups each attached to CoA
3- this beta oxidisation pathway generates reduced NAD and reduced FAD
4-the acetyl groups are released from CoA and enter the kerb cycle by combining with the four carbon oxaloacetate
if the RQ value is greater than 1, this indicates ….
that some anaerobic respiration is taking place , because it shows that more carbon dioxide is being produced than oxygen is being consumed
describe how to assemble a fermentation tube
1-using a pipette , place 10 drops of sugar solution and 10 drops of yeast suspension into each tube . top up with distilled water . for the control, use 10 drops of distilled water in place of the sugar solution
2- push the fluid filled fermentation tube to the end of a test tube and invert
3- measure the height of the fluid in the fermentation tube
