5.7 respiration Flashcards
(117 cards)
1
Q
what is respiration
A
a process that occurs in living cells and releases the energy stored in organic molecules such as glucose
2
Q
what examples of biological processes does ATP drive
A
- Active transport
- Movement
- Endocytosis/ Exocytosis
- Synthesis of large molecules (e.g. proteins)
- DNA replication
- Cell division
- Activation of chemicals
3
Q
what is metabolism
A
all the chemical reaction which take place in a living cell
4
Q
what are anabolic reactions
A
metabolic reactions where large molecules are synthesised from smaller molecules
5
Q
what are catabolic reactions
A
metabolic reactions involving the hydrolysis of large molecules to smaller ones
6
Q
what type of energy is in ATP
A
chemical potential energy
7
Q
what does a molecule of ATP consist of
A
- Adenine
- Ribose
- Three phosphate groups
8
Q
What causes the hydrolysis of ATP?
A
readily hydrolysed by enzyme catalysis even though it is relatively stable
9
Q
What is produced when ATP is hydrolysed?
A
ATP is hydrolysed into ADP and Pi.
- a small quantity of energy is released for use in cells.
-some energy is released as heat
10
Q
what is ATP commonly referred to as
A
-referred to as the universal energy currency, as it occurs in all living cells and is a source of energy which can be used by cells in
11
Q
Why is ATP called the Universal energy currency?
A
It is found in all living organisms/all types of cells.
It is concerned with transmitting energy and is readily available for hydrolysis, releasing small manageable amounts of energy to meet the cell’s needs, but not in quantities that could damage the cell.
12
Q
why is releasing heat when ATP is hydrolysed not considered wasteful
A
heat can keep organisms warm
13
Q
what is the numerical amount of energy that is released when a phosphate group is hydrolysed from ATP
A
30.5kJ
14
Q
describe and explain the role of ATP in the cell (3)
A
-energy ‘currency’
-energy released in small packets
-it releases 30.5kJ of energy when a phosphate is removed by hydrolysis (3)
15
Q
What is Glycolysis?
A
Glycolysis is the first stage of respiration. It is a 10-stage metabolic pathway that converts glucose to Pyvurate.
16
Q
Where does Glycolysis occur?
A
Glycolysis occurs in the cytoplasm of all living organisms that respire
17
Q
what enzyme can be seen to be helping glycolysis
A
the coenzyme, NAD
18
Q
whats a coenzyme
A
-organic molecule
-can change shape
19
Q
whats a cofactor
A
-inorganic molecule
-cant change shape
20
Q
wha are the 3 main stages of glycolysis
A
- Phosphorylation of glucose to hexose bisphosphate
- Splitting each hexose bisphosphate molecule into two triose phosphate molecules
- Oxidation of triose phosphate to pyruvate
21
Q
what do enzymes that catalyse oxidation and reduction reactions need help of
A
need help of coenzymes that accept hydrogen atoms during oxidation
22
Q
What is NAD?
A
***NAD is a non-protein enzyme coenzyme that helps dehydrogenase enzymes catalyse oxidation and reduction reactions.
23
Q
What is the structure of NAD?
A
NAD is synthesised in living cells from Nicotinamide, Ribose, Adenine, and phosphate groups.
The Nicotinamide group can accept two protons to become reduced.
24
Q
How does NAD work?
A
NAD accepts the hydrogen atoms removed during oxidation.
25
Why do living organisms have low levels of NAD in their cells, despite using many molecules of NAD throughout the day?
It is continually being recycled - reduced and then reoxidised
26
whats the first step in glycolysis?
1. glucose is phosphorylated to become hexose monophosphate and then phosphorylated again to hexose biphosphate (2 inorganic phosphate groups added)
-the energy produced prevents it from being transported out of the cell
-one ATP is hydrolysed to ADP and Pi for each time glucose is phosphorylated so 2 ATP is used in total
27
whats the second step in glycolysis?
2. the 6 carbon hexose biphosphate is unstable and breaks into two 3 carbon molecules called TP (each with a phosphate group attached)
28
whats the third step in glycolysis (after TP is formed)?
process is anaerobic but oxidation is involved (cus it involves the removal of H atoms from substrate molecules)
-dehydrogenase enzymes, aided by the coenzyme NAD, remove hydrogens from triose phosphate
-the two molecules of NAD accept the hydrogen atoms (protons and electrons) and become reduced (2 molecules of reduced NAD formed, 1 H atom for each)
-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.
29
whats the products of glycolysis
for each molecule of glucose:
-two molecules of (3C) Pyruvate
-two molecules of reduced NAD
-a net gain of two molecules of ATP
30
why is there only a net gain of 2 molecules of ATP for glycolysis
2 molecules of ATP are used in the Phosphorylation of Glucose to Hexose Biphosphate.
Then 4 molecules of ATP are regenerated in the Oxidisation of Triose phosphate
31
state two roles of 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 Pi
-can give up protons and electrons that is accepted during on of the first three stages of respiration, it becomes oxidised and can be re-used to oxidise more substrate in the process of becoming reduced again
32
what are the 4 stages of respiration of glucose
-glycolysis (anaerobic- cytoplasm)
-the link reaction (aerobic- mitochondria)
-the krebs cycle (aerobic- mitochondria)
-oxidative phosphorylation (aerobic- mitochondria)
(pyruvate molecules from glycolysis are actively transported to the mitochondria for the link recation)
33
what occurs to pyruvate in anaerobic conditions
its converted in the cytoplasm to lactate or ethanol. in the process reduced NAD molecules are re-oxidised so that glycolysis can continue to run producing 2 molecules of ATP for every glucose molecule metabolised
34
whats the envelope of the mitochondria
the envelope consists of the inner and outer phospholipid bilayer
35
What is the role of the outer membrane?
The outer phospholipid bilayer membrane contains some proteins which form channels or carriers that allow the passage of molecules, such as pyruvate, into the mitochondria.
36
what is the role of the intermembrane space (its between the inner and outer membranes)
The intermembrane space is involved in oxidative phosphorylation.
-the inner membrane is in close contact with the mitochondrial matric, so the molecules of reduced NAD and FAD can easily deliver hydrogens to the electron transport chain
37
what is the role of the inner membrane
The inner phospholipid bilayer membrane is less permeable to small ions such as hydrogen ions.
It folds into the cristae giving a large surface area for the electron carriers and ATP synthase enzymes embedded in them.
The inner membrane is in close contact with the mitochondrial matrix, so the molecules of reduced NAD and FAD can easily deliver protons to the electron transport chain.
there are proteins that transport electrons, protons and protein channels associated with ATP synthase enzymes that allow protons to diffuse through them.
38
what is the role of the mitochondrial matrix
the matrix is where the link reaction and Krebs 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 group from the link reaction
-mitochondrial DNA- looped, some of which codes for mitochondrial enzymes and other proteins
-mitochondrial ribosomes- structurally simmilar to prokaryotic ribosomes, where these proteins are assembled
39
whats the function of cristae
highly folded to increase surface area
40
What is the role of ATP Synthase?
ATP synthase enzymes are large and protrude from the inner membrane into the matrix.
Protons can pass through them.
41
What is the structure of Electron carrier protein?
Each electron carrier protein contains a cofactor - a non-protein haem group that contains an Iron ion.
Each electron carrier also have a coenzyme.
42
How do Electron carriers work?
The Iron ion can accept and donate electrons because it can become reduced (Fe2+) by gaining an electron and then become oxidised when donating an electron (Fe3+) to the next electron carrier. Electron carrier proteins are oxido-reductase enzymes.
43
why is it important that electron carriers also have a coenzyme
the coenzyme uses energy released from the electrons to pump protons from the matrix to the intermembrane space
44
what occurs when the coenzyme in an electron transport chain pumps protons into the inter membrane space
protons accumulate in the intermembrane space and a proton gradient forms across the membrane. this gradient can produce a flow of protons through the channels associated with ATP synthase to make ATP
45
Where does the Link Reaction take place?
The Link Reaction takes place in the Mitochondria Matrix.
46
How is Pyvurate brought into the Mitochondrial Matrix?
Pyruvate produced during glycolysis is transported across the outer and inner membrane via specific Pyruvate-H+ symport.
Pyrvuate-H+ symport is a transport protein that transports two molecules into the matrix.
47
after pyruvate is moved into the matrix, what main two steps occur
1. pyruvate is converted to a two carbon acetyl group during the link reaction
2. the acetyl group is oxidised during to the krebs cycle
48
what is the fate of pyruvate in the link reaction
one pyruvate is broken down to a two carbon acetyl group
49
outline the link reaction
-in the link reaction a carboxyl group and hydrogen atoms are removed from the pyruvate.
-when a carboxyl group is removed, this process is decarboxylation
-when hydrogen atoms are removed, this process is dehydrogenation
-the decarboxylation and dehydrogenation of pyruvate is catalysed by the large multi-enzyme complex pyruvate dehydrogenase
-when the carboxyl group is removed, co2 is produced
-when the hydrogen atoms are removed from the pyruvate they are accepted by NAD, producing reduced NAD
-Finally the acetyl group combines with a molecule called coenzyme A (Co A) to form the compound acetyl coenzyme A (acetyl CoA)
50
what does each pyruvate molecule used during the link reaction produce
* One carbon dioxide molecule
* One reduced NAD
* One molecule of acetyl CoA
51
What is the equation for the Overall Link Reaction?
2 Pyruvate + 2NAD + 2CoA --> 2CO2 + 2 RNAD + 2 Acetyl CoA
52
Where does the Krebs Cycle take place?
The Krebs cycle takes place in the Mitochondrial Matrix.
53
how does the acetyl group move to the krebs cycle
coenzyme A accepts the acetyl group and in the form of acetyl CoA carries the acetyl group onto the Krebs cycle.
54
summarise the idea of the krebs cycle
-its a series of enzyme catalysed reactions that oxidise acetate from the link reaction to two molecules of co2 while conserving energy by reducing the coenzymes NAD and FAD
-these reduced coenzymes then carry the hydrogen atoms to the electron transport chain on the cristae, where they will be involved in the production of many more ATP molecules
55
describe the steps of the krebs cycle
1. The 2C Acetyl group released from acetyl CoA combines with a 4C Oxaloacetate to form 6C Citrate.
2. Citrate (6C) is Decarboxylated and Dehydrogenated.
- A 5C compound is produced
- One molecule of Carbon Dioxide is produced
- One molecule of reduced NAD is produced
3. The 5C compound is further decarboxylated and dehydrogenated.
- 4C compound is produced
- One molecule of Carbon Dioxide is produced
- One molecule of reduced NAD is produced
4. This 4C compound combines temporarily with Coenzyme A.
- One molecule of ATP is produced (substrate-level phosphorylation)
5.The 4C compound is then dehydrogenated.
- A different 4C Compound is produced
- A molecule of reduced FAD is produced
6. The 4C compound is rearranged and dehydrogenated to regenerate Oxaloacetate.
- It is catalysed by an Isomerase Enzyme.
- A molecule of reduced NAD is produced
56
What is Substrate-level Phosphorylation?
Production of ATP from ADP and Pi during glycolysis and the Krebs Cycle
57
How many turns of the Krebs cycle is there for each molecule of Glucose?
For every molecule of glucose there are two turns of the Krebs cycle.
58
per molecule of glucose, how much of each is produced in the link reaction...
-Reduced NAD
-Reduced FAD
-Carbon dioxide
-ATP
-Reduced NAD= 2
-Reduced FAD= 0
-Carbon dioxide= 2
-ATP= 0
59
per molecule of glucose, how much of each is produced in the krebs cycle...
-Reduced NAD
-Reduced FAD
-Carbon dioxide
-ATP
-Reduced NAD= 6
-Reduced FAD= 2
-Carbon dioxide= 4
-ATP= 2
60
Why are the Link reaction and the Krebs cycle considered Aerobic when no oxygen is used?
Although oxygen is not directly used, these stages will not occur in the absence of oxygen, so they are aerobic.
61
other substances besides glucose can be respired aerobically:
How can Fatty acids be respired?
Fatty acids are broken down into many molecules of Acetate that enter the Krebs cycle via Acetyl CoA
62
other substances besides glucose can be respired aerobically:
How can Amino acids be respired?
Amino acids are deaminated and the molecule can enter the Krebs cycle directly or be changed to Pyruvate or Acetyl CoA
63
other substances besides glucose can be respired aerobically:
How can Glycerol be respired?
Glycerol may be converted to Pyvurate and enter the Krebs cycle via the Link Reaction.
64
What is Oxidative Phosphorylation?
The formation of ATP using the energy released in the electron transport chain and in the presence of oxygen.
It is the last stage in Aerobic respiration.
65
Where does Oxidative Phosphorlyation take place?
Inner mitochondria membranes/ Cristae
66
what are the 3 steps of the final stage of aerobics respiration in terms of hydrogen atoms
1. Reduced NAD and reduced FAD produced in the Krebs Cycle are reoxidised and lose their Hydrogen atoms to the electron transport chain
2.The Hydrogen atoms produced are split into Protons and Electrons.
3. The Protons go into the solution of the Matrix.
67
what happens to the electrons along the ETC
The Electrons pass along the chain of electron carriers. Each electron carrier protein has an Iron ion at the core which becomes oxidised and reduced. The electrons can be re-donated to each iron ion.
As the Electrons pass along the chain, Energy is produced.
68
What is the Energy produced by the electrons passing along the electron transport chain used for?
The Energy is used to pump protons across the inner mitochondrial membrane into the Intermembrane Space.
69
What happens as Protons accumulate in the Intermembrane Space? (electron transport chain)
a proton gradient forms across the membrane
A concentration gradient called a Chemiosmotic Potential or a Proton Motive Force is set up.
This causes Protons to diffuse through the membrane via protein channels associated with ATP synthase.
70
what is the permeability for protons for the outer membrane and the inner membrane
The outer membrane has a low degree of permeability to protons
The inner membrane is impermeable to protons
71
What happens as Protons diffuse through ATP synthase channels?
A conformational change in the ATP synthase channel allows ADP and Pi to combine to form ATP.
This flow of protons is known as chemiosmosis.
the formation of ATP in this way, in the presence of oxygen is known as oxidative phosphorylation
72
define chemiosmosis
flow of protons down their concentration gradient, across a membrane, through a channel associated with ATP synthase
73
oxygen is the final electron acceptor, how is water formed
oxygen combines with electrons coming off the electron transport carrier chain and with protons diffusing down the ATP synthase channel, forming water
74
What is the equation for the formation of Water?
4H+ (+) 4e- (+) O2 -> 2H2O
75
How many molecules of ATP are produced in Glycolysis per Glucose molecule?
2 molecules of ATP
76
How many molecules of ATP are produced in The Krebs Cycle per Glucose molecule?
2 molecules of ATP
77
How many molecules of ATP are produced in Oxidative Phosphorylation per Glucose molecule?
28 molecules of ATP
(the protons and electrons from 10 molecules of reduced NAD can theoretically produce 25 molecules of ATP)
(the protons and electrons from 2 molecules of reduced FAD can theoretically produce 3 molecules of ATP)
78
How many molecules of ATP are produced in total per Glucose molecule in aerobic respiration?
32 molecules of ATP
79
Why is the theoretical yield of 32 ATP molecules rarely achieved?
- Some ATP is used to actively transport Pyruvate into the mitochondria
- Some ATP is used to transport reduced NAD, made during glycolysis, into the mitochondria.
- Some Protons may leak out through the outer mitochondrial membrane.
30 molecules more likely to be achieved
80
Why can Aerobic Respiration not occur in the absence of Oxygen?
1. Oxygen cannot act as the final electron acceptor at the end of Oxidative Phosphorylation. This means Protons diffusing through ATP synthase channels are not able to combine with electrons to form water.
2.The Proton gradient therefore reduces and protons begin to accumulate in the matrix.
3. Oxidative phosphorylation ceases
4. Reduced NAD and reduced FAD are not able to unload their hydrogen atoms and cannot be re-oxidised.
5. This means the Krebs cycle stops, as does The Link Reaction as NAD is needed to reduce reactants. The reduced NAD needs to be oxidised for glycolysis to continue, these reduced coenzyme molecules cannot be re-oxidised at the electron transport chain* so another metabolic pathway must take place.
*************
81
If the Link reaction, Krebs cycle, and Oxidative phosphorylation require oxygen, how else can ATP be produced?
ATP can still be produced through Glycolysis.
However, the reduced NAD produced in the oxidation of Triose Phosphate has to be re-oxidised so that glycolysis can continue.
82
what are the two metabolic pathways in which reduced NAD can be re-oxidised
-fungi such as yeast and plants use the ethanol fermentation pathway
-mammals use the lactate fermentation pathway
(both take place in the cytoplasm)
83
describe the steps in the ethanol fermentation pathway clearly showing the fate of pyruvate
1. Pyruvate produced during glycolysis is decarboxylated and converted to Ethanal.
-This stage is catalysed by Pyruvate decarboxylase, which has a coenzyme, thiamine diphosphate, bound to it.
2. The Ethanal accepts hydrogen atoms from NADH, becoming reduced to 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 TP, thus allowing glycolysis to continue
84
what pathway do mammals use to re-oxidise reduced NAD and when is this pathway used
-lactate fermentation pathway
-occurs in muscles when ATP demand is high and there is a deficit in oxygen
85
outline the steps in 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 this reaction, there are 2 outcomes:
-pyruvate is reduced to lactate. -The reduced NAD becomes oxidised.
2. The re-oxidised NAD can accept more hydrogen atoms from TP during glycolysis, and glycolysis can continue to produce enough ATP to sustain muscle contraction for a short period.
86
what is the fate of the lactate produced
Lactate is carried away from the muscles, in the blood, to the liver. When more oxygen is available, lactate is:
- Converted to pyruvate, which may enter the Krebs cycle via the Link reaction
- Recycled to glucose and glycogen
87
What would happen if Lactate was not removed from muscle tissue?
If Lactate was not removed from muscle tissue, the pH would be lowered and this would inhibit the action of many of the enzymes involved in glycolysis and muscle contraction.
88
describe the ATP yield from anaerobic respiration
-ethanol fermentation and lactate fermentation both don't produce ATP...
HOWEVER... glycolysis can still continue which generates a net gain of 2 ATP per molecule of glucose
cus the glucose is only partly broken down, many more molecules undergo glycolysis per minute, thus total yield of ATP= quite large, HOWEVER the the yield via anaerobic respiration is about 1/15th of that produced during aerobic respiration.
89
what location do most reduced NAD and reduced FAD get made for oxidative phosphorylation
mostly in the matrix, some in the cytoplasm
90
what is the energy produced by the first step of oxidative phosphorylation in the electron transport chain used to do
this energy is used to actively pump protons from the mitochondrial matrix into the intermembrane space
91
why can a gradient of more protons in the intermembrane space be achieved
-what dos the proton gradient form
because the inner mitochondrial membrane is impermeable to protons (can only diffuse into the matrix by channels associated with ATP synthase)
overall the proton gradient forms the chemiosmotic potential (a source of potential energy used to generate ATP)
92
what is chemiosmosis
the flow of protons through the ATP synthase associated channel and down a concentration gradient
93
what are the folds of the inner mitochondrial membrane called
and what do they contain
cristae
they contain embedded electron carrier proteins which form an electron transport chain
94
name respiratory substrates
carbohydrates, lipids, proteins
-they can be oxidised in the presence of oxygen to produce molecules of ATP, CO2 and water , they each have different relative energy values
95
what is the chief respiratory substrate
glucose
96
what mammalian cells only use glucose for respiration
brain cells and red blood cells
97
how are some monosaccharides (fructose and galactose) changed to glucose for respiration
via isomerase enzymes to glucose
98
give an example of a type of tissue that lipid is used as a respiratory substate
muscles
99
what is glycerol converted to to be respired
glycerol can be converted to TP to be respired
100
why do fats produce more ATP than carbohydrates
fatty acids are long chain hydrocarbons so are the source of many protons for oxidative phosphorylation
101
outline the steps that make one molecule of reduced FAD, one molecule of reduced NAD and one molecule of ATP by substrate level phosphorylation made by fatty acids
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 oxidation pathway generates reduced NAD and reduced FAD
4. The acetyl groups are released from CoA and enter the krebs cycle by combining with the four carbon oxaloacetate
5. for every acetyl group oxidised in the krebs cycle, three molecules of reduced NAD, one molecule of reduced FAD and one molecule ATP by substrate level phosphorylation is made
102
what happens to the excess amino acids after the digestion of proteins
they are deaminated in the liver
103
what does a keto acid enter the respiratory pathway as
enters the respiratory pathway as pyruvate, acetylCoA or Krebs cycle acid such as oxaloacetic acid
104
in what circumstance is protein from muscle hydrolysed to amino acids
-during fasting, starvation or prolonged exercise, when insufficient glucose or lipid are available for respiration
105
how can amino acids enter the krebs cycle
via being converted to pyruvate or acetate and enter the krebs cycle
(enter as 5C compound, enter as acetyl CoA and enter as pyruvate)
106
more ATP is produced when there is more...
more ATP is produced when there is more protons available for chemiosmosis.
This means more hydrogen atoms there are in a respiratory substrate, more ATP is generated per molecule.
107
what is the mean energy value of the respiratory substrate, carbohydrate
15.8 kJ g-1
108
what is the mean energy value of the respiratory substrate, lipid
39.4 kJ g-1
109
what is the mean energy value of the respiratory substrate, protein
17.0 kJ g-1
110
what determines if more or less oxygen is needed for respiration
as protons ultimately combine with oxygen atoms to form water, the greater the proportion of hydrogen ions in a molecule, the more oxygen will be needed for respiration
111
what is the respiratory quotient formula:
RQ= CO2 produced
---------------------
O2 consumed
112
what is the respiratory quotient for glucose
C6H12O6 + 6H2O ---> 6CO2 + 6H2O
so 6/6= 1
RQ= 1
113
what is the respiratory quotient for fatty acids
RQ= 0.7
114
what is the respiratory quotient for amino acids
RQ= 0.8
( values can be between 0.8 and 0.9 for amino acids)
115
what does a RQ value greater than 1 indicate
indicates that some anaerobic respiration is taking place because it shows that more CO2 is being produced than oxygen is being consumed
116
what is the principle of a respirometer
- Carbon dioxide produced is absorbed by lime water
- This decreases the pressure in the tube and the coloured liquid in the U-tube is withdrawn higher and changes height.
-the volume change is due to the production of oxygen
117
How can a Respirometer be used to investigate the effect of Aerobic Respiration?
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 (e.g. woodlice) used should be found.
3. The whole set-up, with the living organisms in place, is put in a water bath 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 levels of coloured liquid in the manometer tubes can be marked with a felt tip pen or chinagraph pencil.
6. The taps are closed and the apparatus is left in the water bath for a specific period.
7. The change in the level of manometer liquid can be measured, and the syringe barrel depressed to reset the apparatus. This enables you to measure the volume of oxygen absorbed.
8. You can then calculate the volume of oxygen absorbed per minute per gram of a living organism.
