5.7 Respiration Flashcards
(166 cards)
1
Q
What happens in respiration?
A
Respiration is a process the occurs in living cells and releases the energy stored in organic molecules such as glucose.
2
Q
What is the energy from repiration immedieatly used for?
A
The energy is used to synthesis molecules of ATP from ADP and inorganic phosphate.
3
Q
What is ATP used for?
A
ATP in cells can be hydrolysed to release energyneeded to drive biological processes.
4
Q
What organisms respire to obtain energy?
A
Microorganisms (eukaryotes and prokaryotes), plants, animals, fungi and protoctists.
5
Q
Why do living organisms need to respire?
A
Via respiration, energy is released from organic molecules, which can be used to make ATP to drive biological processes.
6
Q
What processes do living organisms need energy for?
A
- Active transport
- Endocytosis
- Exocytosis
- Synthesis of large molecules e.g. proteins
- Dna replication
- Cell division
- Activation of chemicals
7
Q
What are the chemical reactions that take place within living cells collectivly known as?
A
Metabolism or metoblic reactions
8
Q
What reactions synthesis small moecules to big molecules?
A
Anabolic reactions are metabolic reactions where large molecules are synthesised from smaller molecules.
9
Q
What reactions invove the hydrolysis pf large molecules to smaller ones?
A
Catabolic reactions involving the hydrolysis of large molecules to smaller ones.
10
Q
What is ATP the intermegiary molecule between?
A
ATP is the standard intermediary between energy-releasing and enrergy-consuming metabolic reactions.
11
Q
What is the structure of ATP?
A
12
Q
When is ATP reatively stable, what does this mean for the molecule?
A
ATP is relatively stable in solution, this means it can easily be mived from place from place to place within a cell.
13
Q
Whsat is ATP readily hydrolysed by?
A
ATP is readily hydrolysed by enzyme catalysis.
14
Q
What is the energy-releasing hydrolysis reaction of ATP paired with?
A
THe energy-releasing hydrolysis of ATP is coupled with an energy-consuming metabiolic reaction.
15
Q
What is ATP hydrolysed to? What happens in this process?
A
ADP and P. A small qunatity of energy is released for use in the cell.
16
Q
Why is energy being produced in small quanitites of energy good?
A
Cells can ontain energy they need for processes in small mangeable amounts that will not cause damage or be wasteful.
17
Q
What is reffered to as the universal energy currency? Why is it reffered to like this?
A
ATP because it occurs in all living cells and is a source of energy that can be used by cells in small amounts.
18
Q
What ways is the energy from the hydrolysis of ATP released by?
A
- Thermal energy
- Chemical potential energy
19
Q
Why is energy released from the hydrolysis of ATP as thermal energy significant?
A
It enables living organisms to stay warm and enables their enzyme-catalysed reactions to proceed at ot near their optimum rate.
20
Q
Every time ATP is hydrolysed, roughly, how much energy is released?
A
30.5kJ mol^-1
21
Q
What is glycosis?
A
Glycosis is the first stage of respiration; a 10-stage metabolic pathway that converts glucose to pyruvate.
It is the biochemical pathway.
22
Q
Where does gylcosis occur?
A
In the cytoplasm of all organisms that respire.
23
Q
During glycosis, what coenzyme catalyses some of the reactions?
A
NAD
24
Q
What are the 3 main stages of glycosis?
A
- Phosphorylation of glucose to hexose biophosphate.
- Splitting each hexose biophosphate molecule into 2 triose phosphate molecules.
- Oxidation of triose phosphate to pyruvate.
25
What do enzymes the catalyse oxudation and reduction reactions need help from?
Coenzymes that accept the hydrogen atoms removed during oxidation.
26
What is the full name of the coenzyme NAD?
Nicotinamide adenine dinucleotide
27
Describe the molecule NAD?
NAD is a coenzyme. It is a non-protein molecule that helps dehydrogenase enzymes to carry out oxidation reactions. NAD oxidises substrate molecules during glycosis.
28
What id NAD sythesised from?
NAD is synthesis is synthesised in living cells from nicotinamide (vitimin B3), the 5-carbon sugar ribose, the nucleotide base adenine and 2 phosphoryl groups.
29
What is the structure of NAD?
30
The nicotinamide ring in NAD can accept 2 hydrogens, what does the NAD become?
Reduced NAD.
31
What does reduced NAD do?
Reduced NAD carries protons and electrons to the cristae of mitochondria and delivers them to be used in oxidative phosphorylation for the generation of ATP from ADP and P.
32
What happens when reduced NAD gives up the protons and electrons that it accepted in 1 of the first 3 stages of respiration?
It becomes oxidised and can be reused to oxidise more substrate, in the process of becoming reduced again.
33
How many carbons does glucose have?
6 carbons, hexose sugar.
34
What happens in phosphorylation in glycolysis?
1. One molecule of ATP is hydrolysed and the released phosphoryl group is added to glucose to make hexose monosulphate.
2. Another molecule of ATP is hydrolysed and the phosphoryl group added to the hexose phosphate to form a molecule of hexose biopholphate. This sugar has one phosphate group at carbon one and six.
35
What happens during splitting the hexose bisphophate in glycolysis?
Each molecule of hexose bisphosphate is split into 2 three-carbon molecules, triose phosphate, each with a phosphate group attatched.
36
What happens during the oxidation of triose phosphate to pyruvate in glyolysis?
1. Dehydrogenase enzymes, aided by coenzyme NAD, remove hydrogens from triose phosphate.
2. The 2 molecules of NAD accept the hydrogen atoms (protons and electrons) and become reduced.
3. At this stage, 2 molecules of NAD are reduced for every molecule of glucose undergoing this process. Also, at this stage, 4 molecules of ATP are made for every triose phosphate molecules undergoing oxidation.
37
What are the products of glycolysis?
* 2 molecules of ATP, 4 have been made but 2 were used to 'kick start' the process
* 2 molecules of reduced NAD
* 2 molecules of pyruvate
38
What are the 4 stages of respiration of glucose?
1. Glycoysis
2. The link reaction
3. The Krebs cycle
4. Oxidative phosphorylation
39
In what conditions does the last 3 stages of respiration occur in?
Anaerobic conditions.
40
Under anerobic conditions, what happens to the pyruvate molecules from glycoysis?
The pyruvate molecules are actively transported into the mitochondria for the link reaction.
In the absencde of oxygen pyruvate is converted in the cytoplasm to lactate or ethanol. In this process, the reduced NAD molecules are reoxidised so glycoysis can continue to run, genewrating 2 molecules of ATP for every glucose molecule metabolised.
41
Why do living organisms have low levels of NAD in their cells although they use many molecules of it through the day?
It is continually being recycled – reduced and then reoxidised.
42
Why is NAD described as a nucleotide derivative?
It contains adenine, ribose sugar and phosphoryl groups, and therefore is derived from two nucleotides.
43
Explain how glycolysis involves oxidation, although its an anerobic process.
Oxidation involves removal of hydrogen atoms from substrate molecules.
44
What is the role of NAD during glycolysis?
It removes hydrogen atoms from triose phosphate molecules, oxidising triose phosphate to pyruvate.
45
Why is the net gain of ATP 2 molecules per molecule of glucose undergoing glycolysis, although 4 molecules of ATP are madde?
Two molecules of ATP are used at the beginning of glycolysis and four are produced, giving a net gain of 4 – 2
= 2.
46
Alcohol is metabolised in the liver. It is oxidised, by dehydrogenation, to ethanal. Ethanal is then oxidised to ethanoate (acetate). Why may people who drink regularly be deficient in NAD?
The NAD being used to oxidise ethanol (ethyl alcohol) and ethanal is not available for use in respiration.
47
What is cristea?
Inner highly-folded moitovhondrial membrane.
48
What is the mitochondrial matrix?
Fluid- filled inner part of mitochondria.
49
Describe the shape of a mitochondrion?
Mitochondria may be rod-shaped, thread like or spherical with diameters of 0.5-1.0μ and lengths of 2-5mμ.
50
Why can we say a michochndria has an envolope?
All mitochondria have an inner and an outer phospholipid membrane making up the envolope.
51
Describe a mitochondia's envolope?
The outer membrane is smooth, and the inner memebrane is folded into cristae, giving it a larger surface area.
52
What is embedded in the inner membrane of a mitochondia, what does this allow?
Embedded in the inner membrane are proteins that transport electrons, and protein channels channels associated with ATP sythase anzymes that aloow protons to diffuse through them.
53
What is between the inner and outer mitochondrial membranes, between the envolope?
Intermembrane space.
54
Describe the mitochondrial matrix?
The mitochondrial matrix, enclosed by the inner membrane , is semi-rigid and gel-like; it contains mitochondrial ribosomes; looped mitochondrial DNA and enzymes for the link reaction and the Krebs cycle.
55
What occurs iin the matrix in a mitochondria?
The link reaction and the Krens cycle.
56
What does the matrix in a mitochondria contain?
* Enzymes that catalyse the link reaction and the Krebs cycle.
* Molecules of the coenzyme NAD and FAD.
* Oxaloacetate- the 4-carbon compound that accepts the actyl group from the link reaction.
* Mitochondrial DNA- some of which codes for mitochondrial enzymes and other proteins.
* Mitochondrial ribosomes
57
Describe the outer mebrane of a mitochondria.
The phospholipid composition of the outer membrane around other organells in eukaryotic cells. It contains proteins, some of which form channels or carriers that allow the passage of molecules, such as pyruvate, into the mitochondrion.
58
Describe the inner membrane of a mitochondrion.
The lipid composition differs from that of the outer membrane. The lipid layer is less permeable to small ions such as hydrogen ions (protons); also, the folds, cristae, in the inner membrane give a large surface area forthe electron carriers and ATP synthase emzymes embedded in them.
59
On the inner membrane of a mitochondrion, how are electron carriers and protein complexes arranged?
They're arranged in electron transport chains. These chains aare involved in the final stage of aerobic respiration, oxidative phophorylation.
60
What is the the innermembrane space in a mitochondrion involved in?
Oxidative phosphorylation.
61
Why is significant that the inner membrane of a mitochondrion is close contact to the mitochondrial matrix?
So the molecules of NAD and FAD can easiy deliver hydrogens to the electron transport chain.
62
What is decarboxylation?
Removal of a carboxyl group from substrate molecule.
63
What is dehydrogenation?
Removal of hydrogen atoms from a substrate molecule.
64
What is substrate-level phosphorylation?
Production of ATP from ADP and P during glycolysis and the kreb cycle.
65
After glycolysis, where is pryuvate transported?
Pyruvate is transported arcoss the outer and inner mitochondrial membranes via specific pyruvate-H+ symport.
66
What process is pyruvate tranported into a mitochondria after glycolysis?
Via specific pyruvate-H+ symport, a transport protein that transports two ions or mo
lecules in the same direction, into the matrix.
67
What happens to pyruvate after being transported into the mitochondrial matrix?
1. Pyruvte is converted to a two-carbon acetyl group during the link reaction.
2. The acetyl group is oxidised during the krebs cycle.
68
Where does the link reaction occur?
In the mitochondrial matrix.
69
Summarise what happens in the link reaction.
Pyruvarte is decarboxylated and dehydrogenated, catalysed by a large multi-enzyme complex, pyruvate dehydrogenase, which catalyses the sequence of reactions that occur during the link reaction.
70
Is ATP produced in the link reaction?
No
71
Describe the steps that occur in the link reaction.
1. The carboxyl group is removed and is the origin of some of the carbon dioxide produced during respiration.
2. The decarbooxylation of pyruvate together dehydrogenation produces a acetyl group.
3. The acetyl group combines with coenzyme A (CoA) to become acetyl CoA.
4. The coenzyme NAD becomes reduced.
72
What reaction summarises the link reaction for 2 molecules of pyruvate devrived from one molecule of glucose?
2 pyruvate +2NAD + 2CoA -> 2CO2 + 2 reduced NAD + 2 acetyl CoA
73
What does coenzyme A do in thw link reaction?
Coenzyme A accepts the acetyl group and, in the form of acetyl CoA, carries the acetyl group on to the kreb cycle.
74
Where does the krebs cycle take place?
In the mitochondrial matrix.
75
Summarise the krebs cycle.
The krebs cycle is a series of enzyme-catalysed reactions that oxidise the acetate from the link reaction to 2 molecules of carbon dioxidem, while conserving energy by reducing the coenzymes NAD and FAD.
76
What is the full name of the coenzyme FAD?
Flavine adenine dinucliotide
77
What will the conenzymes involved in the krebs cycle do with the hydrogen ions?
They will take the hydrogen atoms to the electron transport chain on the cristae, where they will be involved in the production of many more ATP molecules.
78
What is happening in this stage of the krebs cycle?
The acetyle group released from CoA combines with 4-carbon, oxalocetate, to form 6-carbon compound, citrate.
79
What is happening in this stage of the krebs cycle?
Citrate is decarboxylated and dehydrogenated, producing 5-carbon compound, 1 molecule of carbon dioxide and 1 molecule of reduced NAD.
80
What is happening in this stage of the krebs cycle?
The 5-carbon compound is further decarboxylated and dehydrogenated, producing a 4-carbon compound, 1 molecule of carbon dioxide and 1 molecule of reduced NAD.
81
What is happening in this stage of the krebs cycle?
This 4-carbon compound combines temporarily with, and is then released from coenzyme A. At this stage, substrate-level phosphorylation takes place, producing 1 molecule of ATP.
82
What is happening at this stage of the krebs cycle?
The 4-carbon compound is dehydrogenated , producing a different 4-carbon compound and a molecule of reduces FAD.
83
What is happening in this stage of the krebs cycle?
Rearrangement of the atoms in the 4-carbon compound molecule, cataysed by an isomerase enzyme, followed by a further dehydrogenation, regenerate a molecule of oxaloacetate, so the cycle can begin again.
84
How many molecules of reduced NAD are produced in the link reaction?
2
85
How many molecules of reduced FAD are produced in the link reaction?
0
86
How many molecules of carbon dioxide are produced in the link reaction?
2
87
How many molecules of ATP are produced in the link reaction?
0
88
How many molecules of reduced NAD are produced in the krebs cycle?
6
89
How many molecules of reduced FAD are produced in the krebs cycle?
2
90
How many molecules of carbon dioxide are produced in the krebs cycle?
4
91
How many molecules of ATP are produced in the krebs cycle?
2
92
Although the link reaction and the krebs cycle occur in anerobic conditions, why won't they occur in the absence of oxygen?
Other substrates beside glucose can be anerobically respired
* Fatty acids are broken down to many molecules of acetate that enter the krebs cycle via acetate CoA.
* Glycerol may be converted to pyruvate and enter the krebs cycle via the link reaction.
* Amino acids may be deaminated (the mino group NH2 is removed) and the rest of the molecule can enter the krebs cycle directly or be changed inot pyruvate or acetyl CoA.
93
Is the link reaction and the krebs cycle anaerobic or aerobic?
They're aerobic, even tho they occur in anearobic conditions, other sustances invloved in them need to the repired aerobically.
94
What does an electron carrier protein contain in the electron transport chain?
Each electron carrier protein contains a cofactor (a non-protein haem group that contains an iron ion).
95
Why is it significant that the electron carrier proteins contain an iron ion?
The iron ions can accept and donate electrons, beacuse it can become reduced (Fe2+) by gaining an electron and then become oxidised (Fe3+) when donating the electron to the next electron carrier.
96
What sort of enzyme is elecron carrier proteins?
Oxido-reductase enzymes.
97
Wha does the coenzymes in electron carriers do?
They have coenxymes that, using energy from the electrons, pump protons from the matrix to the intermembrane space.
98
Due to coenzymes on electron carriers, protons accumulate in the intermembrane space, what efefct does this have?
Protons accumulate the create a concentration gradient across the membrane. This proton gradient can produce a flow of protons through the channels in the ATP sythase enzymes to make ATP.
99
What are ATP synthase enzymes?
ATP synthase enzymes are large and protude from the inner membrane into the matrix of a mitochondria. Protons can pass through them.
100
What is chemiosmosis?
Flow of protons, down their concentration gradient, across a, membrane, through a channel associated with ATP synthase.
101
What is oxidative phosphorylation?
The formation of ATP using energy released in the elcrton transport chain and in the presence of oxygen. It is the last stage of respiration.
102
In regards to oxidative phosphorylation, why is mitochondria having folded cristae significant?
It gives a large surface area for electron carrier proteins and the ATP synthase enzymes.
103
Where do the electrons and protons come from for oxidative phosphorylation?
* Reduced NAD and reduced FAD are reoxidised when they deliver hydroggen atoms to the electron transport chain.
* The hydrogen atoms released from the reduced coenzymes split into protons and electrons.
* The protons go into solution in the nitochondrial matrix.
104
What happens in the electron transport chain?
The electrons from the hydrogen artoms pass along the chain of electron carriers. Each electron carrier protein has an iron ion at it's core. The iron ions gain an electron, become reduced (Fe2+).
The reduced irom ion can the donate the electron to the iron ion in the next electron carrier in the chain, becoming reoxidised to Fe3+.
As electron pass along the chain, some of their energy is used to pump propons across the inner mitochondrial membrane into the intermembrane space.
105
What does a proton gradient form?
A proton gradient will generate a chemiosmotic potential, also known as a proton motive force, pmf. They are the source of potential energy.
106
In oxidative phosphorylation, what force is used to make ATP.
ATP is made using the enrgy of the proton motive force.
107
How do protons diffuse through membranes in a mitochondria?
Protons cannot easily diffuse through the lipid bilayer of the mitochondrial membranes, as the outer membrane has a low permeability to protons and the inner membrane is impermeable to them.
Instead, rotons diffuse through the protein channels associated with ATP synthase enzymes that are in the inner membrane.
108
What happens to the ATP synthase as protons diffuse through them?
As protons diffuse dow their concentration gradient through the ATP sythase enzymes, the flow of protons cause a conformational (shape) change in the ATP synthase enzyme that allows ADP and P to combine, forming ATP.
109
What is the flow of protons causing a conformational shape in ATP synthase called?
Chemiosmosis. This is coupled with the formation of ATP.
110
Why is oxygen required for oxidative phosphorylation?
Oxygen is the final electron acceptor. It combines with elecrons coming off the electron transport chain with protons, diffusing down the ATP synthase channel, forming water.
4H+ + 4e- + O2 -> 2H2O
111
Explain how much ATP is made during oxiddative phosphorylation.
The protons and electrons from the 10 molecules of reduced NAD (from earlier in respiration) can theoretically produce 25 molecules of ATP. The portons and elctrons from the 2 molecules of reduced FAD and theroretically produce 3 molecules of ATP. Oxidative phosphorylation can therefore theroetically produce 28 molecules of ATP per glucose.
112
What is the net gain of ATP per glucose in glycolysis?
2
113
What is the net gain of ATP per glucose in the link reaction?
0
114
What is the net gain of ATP per glucose in The krebs cycle?
2
115
What is the net gain of ATP per glucose in oxidative phosphorylation?
28
116
What is the net gain of ATP per glucose in respiration?
32
117
The theroetical gain of ATP per glucose in repiration is 32 molecule, why is this value 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 in glycoysis, into mitochindria.
* Some protons may leak out throigh the outer mitochondrial membrane.
118
What happens in repiration when oxygen is absent?
1. Oxygen cannot act as the final electron acceptor at the end on oxidative phosphorylation. Ptrotons diffusing through channels associatied with ATP synthase are not able to combine with oxygen and form water.
2. This causes the concentration of protons in the matrix to increase, reducing the concentarion gradient aross the inner mitochondrial membrane.
3. Oxudative phosphorylation ceases.
4. Reduced NAD and reduced FAD are not able to unload their hydrogen atoms and cannot be reoxidised.
5. The krebs scycle stops, as does the link reaction.
119
What stage of respiration can occur without the presence of oxygen? What is different about this?
Glycolysis can take place, but the reduced NAD generated during the oxidarion of triose phosphate to pyruvate has to be reoxidised so that glycoysis can continue. These reduced coenzymes cannot be reoxidised at the electron chain, so another metabolic pathway must operate to reoxidise them.
120
How can reduced NAD be reoxidsed in anearobic conditions?
* Fungi, such as yeast, amd plants use the ethanol fermantation pathway.
* Mammals use the lactate fermentation pathway.
Both take place in the cytoplasm of cells.
121
What is the ethanol fermantation pathway?
122
Explain what happens to pyruvate under anareobic conditions in yeast cells.
1. Each molecule of pyruvate produced during glycolysis is decarboxylated and converted inot ethanal. This stage in the pathway is catalysed by pyruvate decarbxylase, which is a coenzyme.
2. The ethanal accepts hydrogen atoms from reduced NAD, becoming redcuded NAD becoming ethanol. The enzyme ethanol dehydrogenase catalyses this 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.
123
What is a problem that yeast cell have if they're under anearobic conditions for too long?
When the accumulation of ethanol reaches about 15%, it will kill the yeast cells.
124
What is the lactate fermentation pathway?
125
When does the lactate fermentaion pathway occur?
It occurs in mammalian muscle tissue during vigorous activity, such as running fast, when the demand for ATP for muscle cotraction is high and there is an oxygen deflict.
126
Explain what happens, starting with pyruvate, in the lactate fermantaion pathway?
1. Pyruvate, produced, during glycolysis, accepts hydrogem atoms from the reduced NAD, also made during glycolysis. The enzyme lactate dehydrogenase catalyses the reaction. There are 2 outcomes:
* pryuvate is reduced to lactate
* The reduces 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/ contactions for a short period.
127
What happens to lactate produces during anaerobic repiration?
The lactate produced in the musxle tissue is carried away from the muscles, in the blood, to the liver. Where more oxygen is available, the lactate may either be:
* converted to pyruvate, which may enter the krebs cycle via the link reaction.
* recycled to glucose and glycogen.
128
What would happen if lactate was not removed form muscle tissues?
The pH would be lowered and this would inhibitthe action of many of the enzymes involved in gylcoysis and musc;e contranctions.
129
How much ATP is producesd in the ethanol fermentaion pathway and the lactate fermentation pathay?
None.
130
Why is the ethanol fermentatioon pathway and the lactate fermentation pathway good although no ATP is produced in either process?
They allow glycoysis to continue, the net gain of 2 molecules of ATP per molecule of gluocse is still obtained.
131
Why can glycolysis occur faster in anearobic conditions?
Becuase glucose is only partly broken down, many more molecules can undergo glycoysis per minute, and therefore the overall yeild of ATP is quite large.
132
For each molecule of glucose, what is the yield of ATP like in anaerobic repiration comoared to aerobic respiration?
For each molecule of glucose, the yeild of ATP via anaerobic respiation is about 1/15 of that produced in aerobic respiration.
133
What is a facultative anarobe?
It is a single celled fungus and is eukarytotic. It's cells contain mitochondria. E.g yeast.
Yeast cell divise asexually by mitosis.
134
If oxygen is lacking, how do yeast cells respire?
Using glycolysis and the ethanol fermentaion pathway.
135
What do yeast cells require ATP to do?
For yeast cells to divide, they reqiure ATP and the rate of reporoduction depends on the amount of ATP available.
136
Can yeast oxidise ethanol under aerobic conditions?
Yes, however less is produced compared to in anaerobic respiration. With anearobic repiration, it may produce enough ethanol to kill the yeast cells.
137
To invetigate the rate of production of yeast cells under aerobic and anearobic condoitions, what equiptment would you need?
* Microscope
* conical flasks of different sizes
* Measuring cylinder
* Muslin
* Pipettes
* Elastic bands
* Culture of brewer's yeast
* Dry cider
138
To invetigate the rate of production of yeast cells under aerobic and anearobic condoitions, what must be done to the before conducting the experiment?
Conical flasks must be cleaned and steralised- they can be heated in the microwave for 5mins on the high setting.
The cider should also be uncontaminated.
139
Describe what is happening in the investigation of yeast cells under earobic and anearobic conditions?
In the presence of oxygen, yeast cells can oxidise the ethanol and any sugar in the cider, and will not be killed by the alchol. They will respire aerobically and produce more ATP that can be used for cell division. Under anaerobic conditions the ethanol cannot be oxidised and will eventually kill the yeast. Therefore, where the respiration is aerobic, more yeast cells should be present per cm^3 at the end of the week.
140
To invetigate the rate of production of yeast cells under aerobic and anearobic conditions, how do you prepare a week before?
1. Pour 50cm^3 of cider into each of the conical flasks.
2. Using a clean pipette, add one drop of yeast suspension to each conical flask.
3. Place 4 layer of muslin over the mouth of each conical flask and secure with an elastic band.
4. Leace the flask in a warm position for about a week.
141
To invetigate the rate of production of yeast cells under aerobic and anearobic condoitions, How do you find the results after the cider-yeast mixture have been left for a week?
1. Mix contents of each flask, using a clean pipette, withdraw some of the contents and place a drop onto a haemoytometer slide with a cover slip in place.
2. Count the number of yeast cells in the centre sqaure and some in the corner square.
3. Each of the 5 squares where you counted contain 16 smaller squares. So you counted cells ion 80 very small squares, having a total volume of 0.002mm^3. If you ultiply the cell count you obtained by 50,000, you will find the number ofyeast cells per cm^3.
4. Carry out 3 counts for each size of flask, to calculate the mean number of yeast cells per cm^3.
5. Tabulate and graph your data.
142
What is a respirtoy substrate?
An organic susbstate that can ne oxidised by respiration, releasing energy to make molecules of ATP.
143
Name a few respiratory substrates.
* Carboydrates
* Lipids
* Proteins
144
How can substrates act is respiratory substrates?
The substates can be oxidised in the presence of oxygen to produce molecules of ATP, carbon dioxide and water.
145
What is trhe difference between different respiratory substrates?
They have diffrent energy values.
146
What is the chielf respiratory substrate?
The monscchacride glucose.
147
How can carbohydrates be used as a respiratory substarte?
Carbonhydrates are made up of sugars. Glucose is stored as glycogen in animals and as starch in plants- these can be hydrolysed to glucose for respiration.
* Disaccharides can be digested to monosaccharides for respiration.
* Monosaccharides such as fructose and galactose can be changes, by insomerase enzymes, to glusoce for respiration.
148
How can lipids be respired?
Trigycerides are hydrolysed by lipase to glycerol and fatty acods. Glycerol can then be converted to triose phosphate and repired.
149
What is the structure of a fatty acid? Why is it good to be respired?
Fatty acids are long-chain hydrocarbons with a carboxylic acid group. In each molecule there are many atoms of carbon and hydrogen and few molecules of oxygen. These molecules are a source of many protons for oxidative phosphorylation.
150
Does carbhydrates or lipids produce more enrgy in respiration?
Fats produce more ATP thsn the equivalent mass of carboyhates due to the high number of carbon and hydrogen atoms per molecule.
151
How is fatty acids respired?
1. With the aid of some energy from the hydrolysis one an ATP molecule to AMP, each fatty acid id combines with coenzyme A.
2. The fatty acid-CoA complex is transported into the mitochondrial matrix, where it is broken down into 2-carbon acetyl groups, each attatched to CoA.
3. This beta oxidartion pathway generates NADH and FADH.
4. The acetyl groups are released for CoA and enter the krebs cycle by combining with the 4-carbon oxalocetate. For every acetly group oxidised in the krebs cycle, 3 molecules of NADH, 1 FADH and 1 ATP, by substare level phosphorylation is produced.
152
What must occur before amino acids can be respired?
Excess amino acids are deaminated in the liver. Deamination involves the removal of the amino group which gets converted to urea and removed vua the kidney. The rest of the amino acid, a keto acid enters the respiratory pathway as pyruvate, acetyl CoA or a Ktrebs cycle acid such as oxaloacetic acid.
153
During fasting or peolonged exercise, when insufficent glucose or lipid is available for respiration, what respiratory molecule can be hydrolysed to be respired?
Proteins.
154
Which respiratory substre will produce the mostto the least ATP in oxidative phosphorylation? (Give some aproximate values)
* Lipid- 39.4kJ g^-1
* Protein- 17.9kJ g^-1
* Carbohydrate- 15.8kJ g^-1
155
When will mre oxygen be needed for respiration?
As protons combine with oxygen atoms to form water, the greater the proportion of hydrogen atoms in a molecule, the more oxygen will be needed for it's respiration.
156
What is the repiratory quotent (RQ)?
If the respiratory quotent is greater then 1, this indicates that some anearobic repiration is taking place bacuase it shows that more carbon dioxide is being produced than oxygen is being consumed. It is a ratio.
157
How can you work out the respiratory quotent?
RQ= CO2 produced/ O2 consumed
158
Whats the RQ vaule of glucose?
1
159
What is the RQ value of fatty acids?
0.7
160
What is the RQ value of amino acids?
0.8
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What is this bit of equipment?
A simple respiometer
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What is a respirometer?
A piece of apparatus used to measure the rate of respiration of living organisms by measuring the rate of exchange of oxygen and carbon dioxide.
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How does a respiraometer show respiration is occuring?
If carbon dioxide is produced, it is absorbed by the sodium hydroxide solution or sode lime, then only volume change within the repirometer is due to the volume of oxygen absorbed by the organsism.
This will exert less pressure than the air in the other tube, causing the couloured liqid in the manometer tube to rise up towards the respirometer tube.
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Using a respirometer, how can the volume of oxygen absorbed be calculated?
If the origin level of liquid in the manometer tube is marked and the radius of the bore in tthe capillary tube is known, the volume of oxygen absorbed during a specific period can be calculated.
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How can you reset a respirometer?
The syringe is depressed to inject air into the system aand reset the liquid in the manometer tube back to it's original position.
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How do you set up a respirometer?
1. After placing coloured liquid, e.g. methylene blue solution that has one drop od detergent added to it , into the manometer tube, the apparatus is connected with taps open. This enables rthe air in the apparatus to connect with the atomsphere.
2. The mas of living rganism to be used should be found.
3. With taps still open ane whole set-up with the living organism in place, is placed in a water bath for at least 10mins until it reache the temperature og the water bath.
4. The syringe plunger should be near the top of the scale on the syringe barrel and it's level noted.
5. The taps are closed and the apparatus left in water bath.
6. The change in level of anometer liquid can be measured, and the syringe barrel depressed to reset the apparatus and enables you to meausre the volume of oxygen absorbed.
