Respiration 5.7 Flashcards
1
Q
What is respiration?
A
Respiration is the process that occurs in all living cells and releases the energy stored in organic molecules like glucose.
2
Q
What is energy immediately used for?
A
Energy released is immediatly used to synthesise molecules of ATP from ADP and inorganic phosphate (pi)
3
Q
What happens when ATP is hydrolysed?
A
The hydrolysis of ATP releases energy needed to drive biological processes
4
Q
What are biological processes ATP drives?
A
ATP need processes:
- active transport
- endocytocis and exocytosis
- synthesis of large molecules like proteins
- DNA replication
- Cell division
- movement
- activation of chemicals
5
Q
What is metabolism?
A
Metabolism is all the chemical reactiosn that take place in living cells
6
Q
What are anabolic reactions?
A
Anabolic reactions are metabolic reactions where large molecules are synthesises from smaller molecules (making large molecules from small molecules)
7
Q
What are catabolic reactions?
A
Catabolic reactions are metabolic reactions involving the hydrolysis of large molecules from smaller ones (breaking down of large molecules to small)
8
Q
Does respiration create or release energy?
A
Respiration releases energy from respiratory substrates
9
Q
Why is ATP referred to as the universal energy currency?
A
ATP is the universal energy currency as it occurs in all living cells and is a source of energy that can be use by cells in small amounts
10
Q
What is the structure of ATP?
A
ATP structure: Adenosine -nitrogenous base adenine -5 carbon sugar ribose 3 phosphate groups ( Tri phosphate)
11
Q
What are the 2 mains bonds in ATP?
A
Bonds:
- phosphodiester between CH2 group o ribose and the first P on the phosphate group
- Phosphoanhydride bond between the phosphate groups
12
Q
Discuss the stability of ATP
A
ATP is relatively stable when in solution in cells and can be easily moved from place to place in a cell BUT is readily hydroylysed by the enzymes catalysis
13
Q
Hydrolysis of ATP releases heat. Why is this not wasteful/inefficient?
A
The heat released helps keep the organisms warm and enables their enzyme catalyses reactions to proceed at or near optimum rate
14
Q
What does glycolyis make?
A
Gylcolysis produces:
- 2 Pyruvate
- 2 reduced NAD
- 2 ATP
15
Q
Where does gycolysis occur?
A
Glycolysis occurs in the cytoplasm
16
Q
What is the series of reactions of respiration?
A
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
17
Q
What is pyruvate converted to in anaerobic conditions?
A
In anaerobic condtions pyruvate is converted to ;lactate or ethanol
18
Q
What is the structure of NAD?
A
NAD:
- adenosine attached to a ribose attached to a phosphate
- nicotinamide attached to a ribose attached to a phosphate
- both phosphates are joined
19
Q
What is NAD?
A
NAD is a non protein molecules that helps dehydrogenase enzymes to carry out oxidative reactions
20
Q
Where does reduced NAD carry the proteins and electrons?
A
Reduced NAD carries protons and electrons to the cristae of mitochondria and delivers them to be used in oxidative phosphorylation.
21
Q
What is nictotinamide?
A
Nicotinamide is vitamin B12
22
Q
Define glycolysis
A
Glycolysis is the first stage of respiration and is a 10 stage metabolic pathway that converts glucose to pyruvate. It is a biochemical pathway that occurs in the cytoplasm of all living organisms that respire
23
Q
How many reactions happen in gycolysis?
A
Gylocysis is a 10 stage metabolic pathway
24
Q
Briefly summarise Gylycolysis
A
Glycolysis:
- glucose (6c)
- Glucose-p (6c)
- Hexose bisphosphate (6c)
- 2 x triose phosphate (3c)
- 2 x pyruvate
25
What stage of gylcolysis does ATP and reduced NAD gte made?
4 ATP are made from ADP +p and 2 reduced NAD are made form 2 NAD in the oxidation of triose phosphate to pyruvate
26
What is the first big stage of Gycolysis?
Phosphorylation of glucose to hexose bisphosphate
Glucose is a stable hexose sugar so needs to be activated before spiltting into 3 carbon compounds
- One ATP is hydrolysed and the released phosphoryl group is added to the glucose
- Another ATP molecule is hydrolysed and the phosphoryl is added again to make hexose bisphosphate
27
In the first stage of glycolysis what does the ATP do other than activating the hexose sugar?
The ATP also prevents it from being transported out of the cell
28
What is the second stage of gycolysis?
The second stage is where hexose bisphosphate is split into 2 triose phosphate molecules each made of three carbons
29
What is the final stage of gycolysis
Oxidation of triose phosphate to pyruvate:
This is anaerobic but involves oxidation
1. dehydrogenase enzymes aided by NAD remove hydrogens from triose phosphate
2. the 2 NAD molecules accept the hydrogen ions and become reduced
3. 2 molecules of NAD are reduced for every molecule of glucose undergoing the process
4. 4 molecules of ATP are made for every 2 triose phosphate molecules undergoing oxidation
30
Define dehydrogenation
Dehydrogenation is the removal of hydrogen atoms from a substrate molecule
31
Define decarboxylation
Decarboxylation is the removal of a carboxyl group from a substrate molecule
32
What is substrate level phosphorylation?
Substrate level phosphorylation is the production of ATP from ADP and Pi during glycolysis and the krebs cycle
33
Where does the link reaction occur and how does the pyruvate get there?
The link reaction occurs in the mitochondrial matrix. The pyruvate is actively transported via a specific pyruvate-H+ symport ( a symport is a transport protein that transports two ions or molecules in the same direction)
34
What are the stages of the link reaction?
The link reaction
1. pyruvate dehydogenated and decarboxylatrd by pyruvate dehydrogenase
2. The decarboxylation and hydrogenation of pyruvate produces an acetyl group
3. the acetyl group combines with coenzyme a (CoA) to come acetyl CoA
4. NAD gets reduced
5. Acetyl CoA transports the acetyl group to the krebs cycle
35
What is the equation summarising the link reaction?
Link reaction
2 pyruvate + 2 NAD + 2 CoA--------
2CO2 + 2 reduced NAD + 2 acetyl CoA
36
Where dos the krebs cyelce take place?
The krebs cycle takes place in the mitochondrial matrix
37
What arew the products of the krebs cycle?
The krebs cycle products:
- 6 reducced NAD
- 2 reducced FAD
- 4 carbon dioxide
- 2 ATP
38
What are the procuts od the link reaction?
Products of the link reaction
- 2 reducded NAD
- 2 carbon dioxide
39
Describe of the Krebs cycle
Krebs cycle
1. Acetyl group + oxaloacetatae = citrate (6c)
2. citrate decarboxylated and dehydrogenated making a 5c compound, CO2 and reduced NAD
3. 5c compound decarboxylated + dehydrogenated to make 4c compound, 1 CO2, 1 reduced NAD
4. 4c temp combines with and released from CoA + substrate level phosphorylation makes 1 ATP
5. 4 c is dehydrogenated producing another 4c compound + 1 reduced FAD
6. Isomerase catalyses rearrangement of 4c molecule + hydrogenation to regenerate a molecule of oxaloacetate
40
How many turns of the Krebs cycle are there for each glucose molecule?
For each glucose molecule there are 2 turns of the Krebs cycle
41
Simply describe main parts of each stage of the Krebs cycle
Krebs cycle:
1. citrate formed
2. 5c moleule made from citrate
3. 5c turned into 4 c compound
4. 4c compound + CoA
5. 4c compound makes new 4c compound
6. rearrangement regenerates oxaloacetate
42
Are the krebs cycle and link reaction anaerobic or aerobic?
The krebs cycle and link reaction are aerobic as they will not happen in the absence of oxygen
43
What are three other substrates for aerobic respiration other than glucose?
- fatty acids broken down into many molecules of acetate
- glycerol converted to pyruvate
- amino acids are deaminated and can enter the krebs cycle directly or change to acetyl CoA or pyruvate
44
What is the only stage of respiration that does not make ATP?
The only stage of respiration that does not make any ATP is the link reaction
45
Describe the structure of a mitochondrion
Mitochondria structure:
- Envelope = inner membrane + outer membrane
- Cristae (folder inner membrane)
- Mitochondrial matrix (inside the inner membrane)
- Intermembrane space between inner and outer membranes
- proteins that transport electrons and proteins channels with ATP synthase
46
What shape are mitochondria?
Mitochondria may be rod shaped, thread like or spherical. Very small
47
Why do mitochondria have a large surface area?
Mitochondria have a large surface area because the inner membrane is folded into cristae
48
What is the final stage of aerobic repiration?
The final stage of repisration ois oxidative phosphorylation
49
Discuss the electron transport chain?
Electron transport chain (ETC)
○ Electron carriers are embedded in mitochondrial membrane with iron ions at the core
○ Co-enzymes NAD and FAD are reoxidised when they donate H atoms to these carriers
○ H atoms split into protons and electrons
○ Electrons move down the chain reducing the Fe3+ to Fe2+ then when they leave it reoxidsises. They release enrgy as they move
○ They are finally donated to oxygen, the final electron acceptor
50
What do electrons release as they move down the electron carrier chain?
Electrons release energy as they move down the electron carrier chain
51
What is chemiosmosis in oxidative phosphorylation?
Chemiosmosis
○ As electrons flow, energy is released
○ This is used to pump protons into the intermembrane space
○ This builds up a proton gradient (and electrochemical gradient)
○ Potential energy builds up in the intermembrane space
○ Hydrogen ions are only able to diffuse through ATP synthase as the inner membrane is impermeable to proton.
○ This drives the reaction of ADP and Pi, forming ATP. This is because as they flow through they caused a conformational change in ATP synthase that allows them to combine. H+ drive its rotation
52
What is the final electron acceptor and what is the equation of what happens here?
Oxygen is the final electron acceptor and it combines with electrons coming of the electron transport chain and the protons from the ATP synthase, forming water.
4 H+ + 4e- + O2 ----- 2 H2O
53
How many molecules of ATP does oxidative phopshorylation make per 1 glucose? Why?
Oxidative phosphorylation makes 28 molecules of ATP
- protons and electrons from the 10 reduced NAD can make 25 molecules of ATP
- protons and electrons from the 2 reduced FAD makes 3 ATP
54
What is the total number of ATP achieved in aerobic respiration per 1 molecule of glucose?
In aerobic respiration 1 molecule of glucose can make 32 ATP
55
How many ATP are made from each stage of respiration per 1 glucose molecule?
ATP gain
- Glycolysis = 2
- Link reaction = 0
- Krebs cycle = 2
- Oxidative phosphorylation = 28
56
What stages of respiration stop and which continue in anaerobic respiration?
In anaerobic respiration, in the absence of oxygen the krebs cycle, link reaction and oxidative phosphorylation stop but gycolysis continues
57
Why is it important that gycolysis continues i n the absence of oxygen?
It is important that glycolysis continues in the absence of oxygen because it yields some ATP and we need ATP
58
Discuss what happens when their is no oxygen available
No oxygen:
1. H+ and e- cannot combine with O2 to make H2O
2. H+ accumulate in the matrix offsetting the accumulating the H+ in the intermembrane space dissipating the chemiosmotic potential and proton gradient
3. oxidative phosphorylation ceases as protons gradient does not poush H+ out of ATRP synthase so no ATP
4. Redcuded NAD and FAD cannot off load H+ atoms and cannot be reoxidised so cell runs out of electron acceptors
5. krebs and link reaction stop as hydrogen released has no where to go
59
What must we do to reoxidise the NAD when we cannot do so in the electron transport chain?
We must use another metabolic pathway to reoxide the NAD
60
What are the 2 pathways used by eukaryotic cells to reoxidise reduced NAD?
- Ethanol fermentation pathway in fungi and plants
| - lactate fermentation pathway in mammals
61
Describe the ethanol fermentation pathway
Ethanol fermentation pathway:
1-pyruvate is decarboxylated to ethanal by pyruvate decarboxylase re;easing CO2
2- ethanal accepts 2 hydrogen atoms from reduced NAD becoming reduced to ethanol, catalysed by ethanol dehydrogenase. Son reduced NAD becomes NAD
62
What does the enzymes pyruvate decarboxylase contain?
The enzyme pyruvate decarboxylase contains a co enzyme of thiamine diphosphate
63
Describe the lactate fermentation pathway
Lactate fermentation pathway;
- pyruvate accepts 2 hydrogen atoms from reduced NAD catalysed by pyruvate dehydrogenase. So reduced NAD becomes NAD
- NAD can then accept more hydrogen atoms from triose phosphate in glycolysis allowing it to continue
64
What does lactate do? Where is it taken?
Lactate lowers the pH of cells so it is transported in the blood to the liver
65
What happens to lactate in the liver?
When oxygen is available lactate turn into pyruvate or is recycled to glycogen and glucose
66
What are the good points of anaerobic respiration?
Positives of anaerobic respiration:
- gycolysis is quick as many glucose can be used per minute
- large ATP yield (2 per glucose)
67
What are the cons of anaerobic respiration?
Cons of respiration:
- Yield per molecule of glucose is only 1/15th of what is produced from one molecule in aerobic respiration
- lactate lowers pH of cells
68
How many molecules of ATP does anaerobic respiration release per glucose molecule?
Anaerobic respiration releases 2 molecules of ATP per molecule of glucose
69
How are mitochondria moved within cells?
Mitochondria are moved by microtubules in cells
70
What is the size of a mitochondrion?
Mitonchondrion are 0.5-1 um wide and 2--5 um long
71
How does the structure of the outermembrane help the mitochrionidra function?
The outer membrane contians proteins allowing passge of molculesintoand outer pf the mitocndirions
72
Howdoes the structure of the inner menrbane help the micondrions function?
The inner memrabne is less permeable to H+ molecules than the outer membrane.
It has a large surface area as it is folded meaning there is lots of rokms for lots of elctron carriers and ATP synthase to be p[acked in sorepiuration can be carried out at a faster rate
73
What does the mitocbndrioal matrizx contian?
Mitochnodrial matrix:
- enzymes for the stages
- molecules of NAD and FAD
- oxaloaceate
- mitochondrial DNA (naked loop)
- mitonchondrial ribosomes
74
What does FAD stand for and what is it?
FAD is Flavine adenine dinucleotide.It is a coenenzyme
75
What is NAD and what does it stand for?
NAD is a coenzyme that sytands for nicotinamide adenine dinucleotide)
76
What are some respiratory substrates?
Respiratory substrates:
- Glucose
- other carbohydrates
- lipids
- proteins
77
What respiratory substrates do the brain and red blood cells specifically use?
Red blood cells and the brain only use carbohydrates as substares
78
How can carbohydratebe used forrepiration?
Dissacharides get digested to monosaccharides and hydrolyeszed to their constituent parts
Monosaccharides may be changed by isomerase enzymes into glucose
79
What part of the body uses lipid for respiratory substrates?
The muscle cells use lipid as they produce more atp than carbohydrate
80
Why do lipids produce more ATP than carbohydrates?
Lipids have fatty acids which have long hydrocarbon chains.these chains have lots of carbon and lots of hydrogen. Lots of hydrogen ions for oxidative phosphorylation so more atp is made
81
How are lipids hydrolysed?
Lipids get hydrolysed;
triglyceride + 3H2O ----- glycerol +fatty acids
helped by lipase enzymes
82
What is the beta oxidation pathway? What does it produce?
beta oxidation pathway is how fatty acids get tuned into acetyl CoA to enter the krbs cycle.
It produces reduced NAD and reduced FAD
83
How many carbons does a acetyl group have?
An acetyl group is a 2 carbon molecule
84
How many reduced NAD and FAD and ATP are made for every acetyl group oxidated in the krebs cycle?
For every acetyl group oxidised in the krebs cycle, 3 molecules of reduced NAD, 1 reduced FAD and 1 ATP are made
85
Discuss how proteins are respired?
Proetins as a respiratory substrate:
- excess amino acids are deaminated into keto acid + ammonia
- keto acid enters the respiratory pathway as pyruvate, acetyl CoA or as a krebs cycle acid
- Where the keto acid derives from changes how they enter the pathway
86
Why does the body not like using proteins as respiratory substrates? When does it use them?
The body doesn't like using proteins as they are important in other functions like structure.
It only uses them during fasting, starving or prolonged periods of exercise
87
If the keto acid enters the respiratory pathway as Pyruvate where was it derived from?
Keto acid entering the respiratory pathway as pyruvate means it derives from
- glycine
- serine
88
If the keto acid enters the respiratory pathway as acetyl CoA where was it derived from?
Keto acid enetering the respiratoty pathway as acetyl CoA means it dervioded from:
- leucine
- lysine
89
If the keto acid enters the respiratory pathway as a krebs cycle acid where was it derived from?
Keto acid entering the respiratory pathway as a krebs cycle acid means it derived from:
- glutamate
- proline
90
How do you calculate respiratory quotient? Units?
Respiratory quotient =
CO2 produced / O2 consumed
No units as it produces a ratio
91
How do you know whether anaerobic respiration is happening from the RQ value?
If there is an RQ bigger than 1 anaerobic respiration is happening as more CO2 is being made than O2 is consumed
92
What is the mean energy value of carbohydrates, lipids and proteins?
```
Carbohydrate = 15.8 KJ per gram
Lipid = 39.4 KJ per gram
Protein = 17 KJ per gram
```
93
What is the negative consequence of having more hydrogen ions and therefore a higher energy value per gram?
Having more hydrogen ions means more energy per gram BUT it means more oxygen is required to respire it so more breathing using chest muscles more
94
Why is carbohydrate generally respired?
Carbohydrate has the lowest mean energy value (15.8)
| compared to lipids and proteins BUT is requires the least oxygen to respire it so less effort is needed by the body
95
What gases are used up and which are given off in respiration?
Oxygen is used up in respiration and carbon dioxide is given out
96
Do we want to measure oxygen used up or carbon dioxide given off in measuring respiration?
To measure rate of respiration we want to measure how much oxygen is used up
97
How do we eliminate the CO2 (eliminate it as a variable in experiment)
To get rid of the variable of CO2 we use soda lime or sodium hydroxide to absorb the CO2
98
What is the alternative of soda lime?
instead of soda lime to absorb CO2 we ca use sodium hydroxide
99
Describe how you would set up a respirometer
Airtight Respirometer:
- Two chambers
- One chamber has a gauze platform with organism to be studied and soda lime
- One chamber has an inert object occupying a volume equal to the organisms and the soda lime
- Capillary U tube with manometer fluid
- syringe e with 3 way tap to insert pure oxygen into chamber 1
100
What is the purpose of the inert object in chamber 2 in a respirometer?
The inert object means that at the beginning the force being exerted on the fluid from each chamber is equal so that when the fluid moves we know it is purely due to the force of chamber a
101
What is the principle of a repirometer?
In a respirometer as oxygen is used up it reduces the gas volume in chamber a meaning there is less pressure being exerted from that side so the fluid moves towards a
102
How do you calculate the amount of oxygen used up in respiration?
volume of oxygen:
| distance traveled fluid x pi radius squared (of capillary tube)
103
How do you reset the respirometer to its original position?
To reset the respirometer you open the lids and then inject pure oxygen from the syringe until the fluid id back in the original position
104
What are 3 consideration of using a respirometer?
Considerations;
- Temperature range as organisms only withstand a small range (use a water bath to keep constant)
- mark initial volumes/ positions of fluid and gas syringe
- the volume of living organisms and soda lime
105
What yeast is used when investigating yeast respiration? What type is it?
Investigating yeast uses SACCHAROMYCES CEREVISIAE which is a facultative anaerobe
106
What is a facultative anaerobe?
Facultative anaerobes are organisms that respire aerobically when they can but will respire anaerobically
107
What do we measure in yeast to see how they are respiring? why?
In yeast e can see their respiration through their reproduction rates. This rate depends on the amount of ATP available which is different for aerobic or anaerobic
108
What would we expect to see in reproduction rate if they were respiring aerobically/anaerobically?
If the yeast were respiring aerobically we would expect a higher reproduction rate as there are more ATP available
109
How do we measure reproduction rates in yeast?
To measure reproduction rates in yeast we count number of cells
110
Yeast use the ethanol pathway when respiring anaerobically, what do we need to consider?
Yeast use the ethanol pathway when repsiring anaerobically. However high levels of ethanol can kill the yeast
111
Describe the experiment for using yeast and reproduction rates for measuring respiration
Respiration in yeast
1. 2 flasks. 1 well ventilated and 1 covered in gauze or cheese cloth to make it not well ventilated
2. leave in the warm for 5 minutes
3. Pipette some out on to haemocytometer
4. count the cells in the middle square and the outer 4 squares
