respiration Flashcards
Cellular respiration (182 cards)
1
Q
enzymes lower ……… energy
A
activation
2
Q
enzymes are often ……….. dependent
A
pH
3
Q
enzymes are often inhibited by the end product in the pathway. This is negative/positive feedback
A
negative feedback
4
Q
gene expression and protein modification regulate enzymes. Give an example of each
A
gene expression - if gene is expressed it will be transcribed and translated into the functional protein that makes up the enzyme
protein modification - phosphorylation (can either switch enzymes on or off)
5
Q
describe a catabolic pathway
A
the break down of complex molecules into simpler ones. Energy is released. e.g. cellular respiration
6
Q
describe an anabolic pathway
A
the building of complex molecules from simpler ones. Energy is required. e.g. the synthesis of starch
7
Q
what are the 3 steps in aerobic respiration
A
glycolysis
citric acid cycle
electron transport chain
8
Q
where does glycolysis occur
A
in the cytosol
9
Q
how many ATP are produced in glycolysis
A
2ATP
10
Q
how are electrons carried in glycolysis
A
by NADH
11
Q
what is the final product of glycolysis
A
glucose –> pyruvate
12
Q
where does the citric acid cycle occur
A
the inner membrane of the mitochondria
13
Q
What are the main steps in glycolysis
A
begin with glucose
energy investment of 2ATP - this breaks down into 2ADP and 2Pi
energy payoff phase where 4ATP are formed. NAD+ picks up electrons
pyruvate produced
14
Q
what are the net gains from glycolysis
A
glucose –> 2pyruvate +2water
net 2ATP
2NAD+ + 4e- + 4H+ –> 2NADH + 2H+
15
Q
what are the main steps of glycolysis (lecture notes version)
A
- glucose –> glucose-6-phosphate (hexokinase uses ATP and phosphorylates glucose)
- Glucose-6-phhosphate –> fructose-6-phosphate (phosphogluco-isomerase)
- fructose-6-phosphate –> fructose-1, 6-bisphosphate (phosphofructo-kinase) molecule starts to look more symmetrical
- fructose-1, 6-bisphosphate –> dihydroxyacetone phosphate + Glyceraldehyde-3-phosphate (adolase)
- Glyceraldehyde-3-phosphate –> 1, 3-bisphosphoglycerate (triose phosphate dehydrogenase)
- 1, 3-bisphosphoglycerate –> 3-phosphoglycerate (phosphoglycerokinase)
- 3-phosphoglycerate –> 2-phosphoglycerate (phosphoglycero-mutase)
- 2-phosphoglycerate –> phosphoenolpyruvate (enolase) 2Water produced
- phosphoenolpyruvate –> pyruvate (pyruvate kinase)
16
Q
what do kinases do
A
they phosphorylate
17
Q
which enzymes is responsible for the conversion between Dihydroxyacetone phosphate and Glyceraldehyde-3-phosphate
A
isomerase
18
Q
where does the energy stored in the organic molecule of food ultimately come from
A
the sun
19
Q
energy flows into an ecosystem in the form of ………… and out in the form of …………..
A
light
heat
20
Q
what does photosynthesis provide
A
It generates oxygen and organic molecules used by the mitochondria of eukaryotes as a fuel for cellular respiration
21
Q
what does cellular respiration provide
A
respiration breaks down organic molecules (fuel) using oxygen - this generates ATP. The waste products of respiration are carbon dioxide and water which are the raw materials for photosynthesis.
22
Q
what type of metabolic pathway releases energy by breaking down complex molecules into simpler smaller ones
A
catabolic
23
Q
organic compounds have potential energy due to the arrangement of what within their structure
A
the arrangement of electrons in the bonds between their atoms.
24
Q
compounds that participate in exergonic reactions can act as what
A
fuels
25
when enzymes degrade complex molecules that are rich in potential energy into simpler waste products with less energy what happens to the energy released for the reaction
some of the energy can be used for work and the rest is dissipated as heat
26
what happens in fermentation
the partial degradation of sugars and other organic fuels without the use of oxygen
27
what is the most efficient catabolic pathway
aerobic respiration
28
give an overview of aerobic respiration
oxygen is consumed as a reactant along with the organic fuel. The fuel is broken down to release ATP and the waste products - water and carbon dioxide
29
which cells carry out aerobic respiration
all eukaryotes and some prokaryotes
30
some prokaryotes do not carry out aerobic respiration and use substances other than oxygen in a reaction with a similar process to aerobic respiration, harvesting chemical energy without oxygen. What is this process called
anaerobic respiration
31
what does the term cellular respiration include
technically aerobic and anaerobic respiration but is mostly used as a reference to aerobic respiration
32
name some molecules from food that can be used as fuel in respiration
carbohydrates, fats and protein
33
in animal diets what is the major source of carbohydrates
starch - a storage polysaccharide that can be broken down into glucose
34
what is the formula for aerobic respiration using glucose as the fuel
C6H12O6 + 6O2 --> 6H2O + 6CO2 + energy(ATP + heat)
35
is the breakdown of glucose endergonic or exergonic
exergonic - catabolic - releases energy
36
catabolic pathways do not directly perform work. How is catabolism linked to work
by ATP - it provides the energy for the reactions that result in work
37
during the breakdown of glucose how is energy released
relocation of electrons during the chemical reactions releases energy stored in organic molecules and the energy is used to synthesise ATP
38
what are electron transfer reactions called
oxidation-reduction reactions or redox reactions
39
what happens in a redox reaction
the loss of electrons from a substance oxidation and the gain of electrons by a substance is called reduction - the combination of these to reaction makes a redox reaction
40
what is the reducing agent
the electron donor that is itself oxidised
41
what is the oxidising agent
the electron acceptor that is itself reduced
42
do all redox reactions involve complete transfer of an electrons from one substance to another
no e.g. in methane combustion the electron transfer is only partial - there is just a change in electronegativity meaning the electrons are pulled more towards one atom than before
43
is energy required to pull an away from an atom
yes - the more electronegative the atom the more energy required to pull an electron away from it
44
an electron loses potential energy when it sifts from a less/more electronegative atom to a less/more electronegative atom
less
| more
45
a redox reaction that moves electrons closer to oxygen takes in/releases energy
releases energy that can be put to work
46
in aerobic respiration the fuel (glucose) is reduced/oxidised and the oxygen is reduced/oxidised
glucose - oxidised
| oxygen - reduced
47
why are organic molecules abundant in hydrogen excellent fuels for respiration
they make good fuels because their bonds are a source of electrons whose energy may be released as the electrons fall down the concentration gradient during their transfer to oxygen
48
in respiration the oxidation of glucose transfers electrons to a lower energy state what is the result of this
the process releases energy that can be used for ATP synthesis
49
In general the fuels of respiration have multiple C-H bonds that are oxidised into products with multiple C-? bonds
C-O bonds
50
what are the main energy yielding foods
carbohydrates and fats - they are reservoirs of electrons associated with hydrogen (C-H bonds)
51
does cellular respiration oxidise glucose in a single step
no - glucose is broken down in a series of steps, each one of these catalysed by an enzyme
52
How do the electrons get transferred in respiration
they are transferred from glucose and travel with a proton i.e. they travel as hydrogen atoms
53
What happens to the hydrogen ions in respiration that transfer the electrons from glucose to oxygen
the Hydrogen atoms are not transferred directly
| They are passed to an electron carrier, a coenzyme called NAD
54
what is NAD derived from
the B vitamin niacin
55
why does NAD a good electron carrier
because it can easily change from its oxidised form (NAD+) to its reduced form (NADH)
56
what does NAD+ function as during respiration
an oxidising agent
57
how does NAD+ trap electrons for glucose and other molecules in food
1. enzymes called dehydrogenases remove a pair of H atoms (removing 2 electrons and 2 protons) from the substrate, oxidising it
2. The enzyme delivers the 2 electrons along with one proton to its coenzyme NAD+ forming NADH
3. the other proton is released as a hydrogen ion into the surrounding solution
58
explain in terms of protons and electrons hoe the charge on NAD becomes neutral when in the reduced form
Recall: oxidised form (NAD+), reduced form (NADH)
NAD+ gains 2 electrons and one proton from the dehydrogenases that pick these up from food molecules.
This adds 2 negative charges and one positive charge to NAD+ and since this is already positively charged the result is a neutral molecule of NADH
59
What is the most versatile electron acceptor in cellular respiration
NAD+
60
electrons lose most/little of their energy on transfer from glucose to NAD+
little - each NADH molecule formed during respiration represents stored energy - this can be used to make ATP when the electrons complete their fall in a series of steps down an energy gradient from NADH to oxygen
61
how do electrons that are extracted form glucose and stored as potential energy in NADH finally reach oxygen
respiration uses an electron transport chain to break the fall of electrons to oxygen into a series of energy releasing steps
electron transfer form NADH to oxygen is exergonic. Instead of this energy being released, electrons cascade down a chain from one carrier molecule to the next in a series of redox reactions, losing small amounts of energy with each step until they reach oxygen (terminal electron acceptor)which has a high affinity for electrons each carrier in the chain is more electronegative than the previous one.
the electrons transferred from NADH to oxygen are moving towards a more stable location - oxygen pulls electrons down the electron transport chain
62
what makes an electron transport chain of respiration
it consists of a number of molecules, most of which are proteins, built into the inner membrane of the mitochondria of eukaryotic cells
electrons removed from glucose by NADH are shuttled to the higher energy end of the chain. At the lower energy end, oxygen captures these electrons along with the hydrogen nuclei (H+) forming water
63
during respiration what are the steps of travel for electrons
Glucose --> NADH --> electron transport chain --> oxygen
64
what are the 3 main stages of cellular respiration
1. glycolysis
2. pyruvate oxidation and the citric acid cycle
3. oxidative phosphorylation: electron transport and chemiosmosis
65
where does glycolysis occur
the cytosol
66
give an overview of glycolysis
begins the degradation process by breaking glucose down into 2 molecules of pyruvate
67
what happens to the pyruvate produced in glycolysis
it enters the mitochondrion (in eukaryotes - in prokaryotes this happens in the cytosol) and is oxidized to form acetyl CoA which then enters the citric acid cycle
68
give an overview of the citric acid cycle
the breakdown of glucose to carbon dioxide is completed
69
the electron carriers NADH and FADH2 transfer electrons derived from glucose to the ……………………..
electron transport chain
70
what happens during oxidative phosphorylation
the electron transport chain accepts electrons from NADH or FADH2 generated through the first 2 stages and passes these electrons down the chain
The electrons become bound with oxygen and hydrogen ions forming water
the energy released at each step of the chain is stored in a form the mitochondrion can use to make ATP from ADP.
this mode of ATP synthesis is called oxidative phosphorylation because it is powered by the redox reactions of the electron transport chain
71
in the earlier steps (glycolysis and citric acid cycle) of cellular respiration, a few molecules of ATP are synthesised - by what process are they synthesised
substrate level phosphorylation
72
what is the inner membrane of the mitochondrion (eukaryotes - the site in prokaryotes is the plasma membrane) the site for in respiration
electron transport and chemiosmosis - the processes that make up oxidative phosphorylation
73
which type of phosphorylation accounts for 90% of the ATP generated by respiration
oxidative phosphorylation
74
when does ATP synthesis by substrate level phosphorylation occur
it occurs when an enzyme transfers a phosphate group from a substrate molecule to ADP, rather than adding an inorganic phosphate to ADP as in oxidative phosphorylation
75
in respiration what does substrate molecule refer to
an organic molecule generated as an intermediate during the catabolism of glucose
76
for each molecule of glucose degraded to carbon dioxide and water by respiration, how many molecules of ATP are produced
32
77
what are the two phases of glycolysis
energy investment and energy payoff
78
what happens during the energy investment phase of glycolysis
the cell invests 2 ATP
79
what happens during the energy payoff phase of glycolysis
4 ATP is produced by substrate level phosphorylation and 2 NAD+ is reduced to 2 NADH by electrons released from the oxidation of glucose
80
what is the net energy yield from glycolysis per glucose molecule
2 ATP and 2 NADH
81
is any carbon released as CO2 in glycolysis
no - all carbon from glucose is accounted for in the 2 pyruvate molecules (they are 3 carbon chains and glucose is a 6 carbon chain)
82
what happens after glycolysis if oxygen is present
the chemical energy stored in pyruvate and NADH is extracted by pyruvate oxidation, the citric acid cycle and oxidative phosphorylation
83
what are the 9 steps in glycolysis (textbook version - just reactant and product pls)
ENERGY INVESTMENT
1. glucose --> glucose 6-bisphosphate
2. glucose 6-bisphosphate --> fructose 6-phosphate
3. fructose 6-phosphate --> fructose 1,6-bisphosphate
4. fructose 1,6-bisphosphate --> glyceraldehyde 3-phosphate (G3P) + dihydroxyacetone phosphate (DHAP)
ENERGY PAYOFF
5. G3P --> 1,3-bisphosphoglycerate
6. 1,3-bisphosphoglycerate --> 3-phosphoglycerate
7. 3-phosphoglycerate --> 2-phosphoglycerate
8. 2-phosphoglycerate --> phosphoenol-pyruvate (PEP)
9. phosphoenol-pyruvate (PEP) --> pyruvate
84
what enzymes are involved for each of the steps in glycolysis
1. hexokinase
2. phosphoglucoisomerase
3. phosphofructokinase
4. aldolase
5. triose phosphate dehydrogenase
6. phosphoglycerokinase
7. phosphoglyceromutase
8. enolase
9. pyruvate kinase
85
which enzyme converts between glyceraldehyde 3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP)
isomerase
86
what specifically happens in each of the steps of glycolysis
1. hexokinase transfers a phosphate group from ATP to glucose - making it more reactive
2. glucose 6-phosphate is converted to fructose 6-bisphosphate
3. phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP - key step for regulation
4. aldolase cleaves the sugar molecule into two different 3 carbon sugars
5. 2 sequential reactions:
(1) G3P is oxidised by the transfer of electrons to NAD+, forming NADH
(2) using energy from this exergonic redox reaction, a phosphate group is attached to the oxidised substrate, making a high energy product
6. phosphate group transferred to ADP (substrate level phosphorylation - ATP released) in an exergonic reaction. Carbonyl group of G3P has been oxidised to the carboxyl group of 3-phosphoglycerate
7. phosphoglyceromutase relocates the remaining phosphate group
8. enolase causes double bond to form in the substrate by extracting a water molecule, yielding phosphoenolpyruvate (PEP) (has high potential energy)
9. the phosphate group is transferred from PEP to ADP (substrate level phosphorylation - ATP released) forming pyruvate.
87
most/little of the energy from glucose remains stored in the pyruvate molecules after glycolysis
most
88
when oxygen is present the pyruvate in eukaryotic cells enters a mitochondria where what happens
oxidation of glucose is completed - in prokaryotic cells this occurs in the cytosol
89
upon entering the mitochondria what is pyruvate converted to
acetyl coenzyme A
90
what step links glycolysis to the citric acid cycle
conversion of pyruvate to acetyl coenzyme A
91
how is pyruvate converted to acetyl coenzyme A
it is carried out by a multienzyme complex that catalyses 3 reactions:
(1) pyruvates carboxyl group is fully oxidised and given off as a molecule of CO2
(2) the remaining 2 carbon fragment is oxidised and the electrons transferred to NAD+, storing energy in the form of NADH
(3) coenzyme A is attached via its sulfur atom to the 2 carbon intermediate forming acetyl CoA
92
what is acetyl coA used for in the citric acid cycle and what type of reaction is this
it is used to transfer the acetyl group to another molecule in the citric acid cycle
the reaction is highly exergonic
93
pyruvate is broken down into how many carbon dioxide molecules
3 - this includes the molecule released during the conversion from pyruvate to acetyl CoA
94
how much ATP does the citric acid cycle generate and by what means is it produced
1 ATP per turn by substrate level phosphorylation
95
where is most of the energy generated by the citric acid cycle transferred to
NAD+ and FAD during redox reactions - NADH and FADH2 then shuttle these electrons to the electron transport chain
96
describe in detail the 8 steps of the citric acid cycle
1. acetyl CoA (from oxidation of pyruvate) adds its 2 carbon acetyl group to oxaloacetate, producing citrate
2. citrate is converted to its isomer, isocitrate, by removal of one water molecule and addition of another
3. isocitrate is oxidised, reducing NAD+ to NADH. then the resulting compound loses a CO2 molecule, producing alpha-ketoglutarate
4. another CO2 is lost and alpha-ketoglutarate is oxidised and attached to coenzyme A to produce succinyl CoA, reducing NAD+ to NADH
5. coenzyme A is displaced from succinyl Co A by a phosphate group (to form succinate), which is transferred to GDP forming GTP, a molecule with functions similar to AT. GTP can also be used to generate ATP
6. 2 hydrogens are transferred to FAD, forming FADH2 and oxidising succinate
7. addition of a water molecule rearranges bonds in the substrate - producing malate
8. malate is oxidised, reducing NAD+ to NADH and regenerating oxaloacetate
97
what makes the citric acid cycle a cycle
the fact that oxaloacetate is regenerated
98
for each acetyl group entering the cycle, how many NAD+ are reduced to NADH
3
99
for each acetyl group entering the citric acid cycle, how many FAD are reduced to FADH2
1
100
what does FAD accept
2 electrons and 2 protons - so is neutral when it forms FADH2
101
where does the only generation of ATP from the citric acid cycle occur
step 5 - the GTP can be converted to one molecules of ATP
102
each glucose gives rise to how many acetyl Co A molecules entering the citric acid cycle
2
103
what is produced from the citric acid cycle as a whole - remember that one cycle involves 2 molecules of acetyl Co A
6 NADH
2FADH2
the equivalent of 2ATP - GTP isn't always converted to ATP
104
most of the ATP produced in respiration results from what kind of phosphorylation
oxidative phosphorylation when the NADH and FADH2 produced in the citric acid cycle and glycolysis relay electrons to the electron transport chain
105
in eukaryotic cells all the citric acid cycle enzymes are located in the mitochondrial matrix except from which one
the one that catalyses step 6 and resides in the inner mitochondrial membrane
106
during oxidative phosphorylation chemiosmosis couples electron transport to what
ATP synthesis
107
how many ATP molecules are produced in total from glycolysis and the citric acid cycle per glucose molecule
4 ATP: 2 from each process
108
how are the ATP produced in glycolysis and the citric acid cycle
by substrate level phosphorylation
109
up until oxidative phosphorylation, which molecules account for most of the energy extracted from glucose
FADH2 and NADH
110
give an overview of oxidative phosphorylation
it uses energy released by the electron transport chain to power ATP synthesis
111
what is the electron transport chain
a collection of molecules embedded in the inner membrane of the mitochondrion in eukaryotic cells (plasma membrane in prokaryotes)
112
what about the inner membrane increases it surface area
it folds into cristae - providing thousands of copies of each component of the electron transport chain in a mitochondria
113
most components of the electron transport chain are proteins - how are the proteins arranged
multiprotein complexes attached to prosthetic groups
114
what are prosthetic groups
non protein components such as cofactors or coenzymes essential for the catalytic function of certain enzymes
115
what happens to the components of the electron transport chain when they accept electrons from their uphill neighbour
they become reduced
116
when a component of the electron transport chain passes its electrons downhill what happens to it
it becomes oxidised
117
going down the electron transport chain the components become progressively less/more electronegative
more - oxygen - the most electronegative component is at the end of the chain
118
free energy is gained/released going down the electron transport chain
released
119
what are the electrons collected from earlier steps in respiration transferred to in the electron transport chain
they are transferred to the first molecule in the electron transport chain in complex I
120
what is the first molecule in the electron transport chain in complex I
a flavoprotein
121
where does the flavoprotein in complex I pass the electrons
to an iron-sulfur protein in complex I
122
where does the iron sulfur enzyme in complex I pass the electrons to
a compound called ubiquinone
123
what is ubiquinone (coenzyme Q)
a small hydrophobic, the only member of the electron transport chain which is not a protein. ubiquinone is individually mobile within the membrane rather then residing in a particular complex
124
what are most of the remaining electron carriers between ubiquinone and oxygen called
they are proteins called cryptochromes
125
what are cryptochromes
proteins whose prosthetic group is a heme which has an iron atom which accepts and donates electrons
126
how are all the different cryptochromes in the electron transport chain named
cyt with a letter and number to distinguish it as a different protein with a slightly different electron carrying heme group
127
what is the last cryptochrome in the chain called and what does it do
cyt a3 passes its electrons to oxygen
128
as well as picking up electrons what else does oxygen pick up and why
a pair of hydrogen ions from the aqueous solution - neutralising the negative charge due to the added electrons - the result is the formation of water
129
where does FADH2 add its electrons in the electron transport chain
from within complex II, at a lower energy than NADH does
130
do NADH and FADH2 donate the same number of electrons
yes - they each donate 2 electrons
131
when FADH2 is the electron donor what fraction of the energy produced from the electron transport chain for ATP synthesis is produced compared to when NADH is the electron donor
2/3
132
where is the protein ATP synthase found
inner membrane of the mitochondria - eukaryotes
| plasma membrane - prokaryotes
133
what does ATP synthase do
it makes ATP from ADP and an inorganic phosphate
134
ATP synthase uses the energy of an existing …………… to power ATP synthesis
ion gradient
135
what is the power source of ATP synthase
the difference in the concentration of hydrogen ions on opposite side of the inner mitochondrial membrane
136
what is chemiosmosis
an energy coupling mechanism in which energy stored in the form of a hydrogen ion gradient across a membrane is used to drive cellular work such as the synthesis of ATP
137
explain the steps of ATP synthesis
1. hydrogen ions flowing down their gradient enter a channel in a stator, which is anchored in the membrane
2. hydrogen ions enter binding sites within the rotor, changing the shape of each subunit so that the rotor spins within the membrane
3. each hydrogen ion makes one complete turn before leaving the rotor and passing through a second channel in the stator into the mitochondrial matrix
4. spinning of the rotor causes an internal rod to spin as well. this rod extends like a stalk into the knob below it, which is held stationary by part of the stator
5. turning of the rod activates catalytic sites in the knob that produce ATP from ADP and Pi
138
what is ATP synthase
a multisubunit complex with 4 main parts which are each made up of multiple polypeptides
139
how does the inner mitochondrial membrane generate and maintain the hydrogen gradient that drives ATP synthesis by ATP synthase
establishing the hydrogen ion gradient is a major function of the electron transport chain. the chain is an energy converter that uses the exergonic flow of electrons from FADH2 and NADH to pump hydrogen ions across the membrane, from the mitochondrial matrix to the intermembrane space
the hydrogen ions have a tendency to flow back across the membrane diffusing down their gradient
to do this they have to flow through ATP synthase which drives phosphorylation of ADP
thus energy stored in the hydrogen gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis
140
what do the mobile electron carriers do in the electron transport chain
they ferry electrons between large complexes
141
as the complexes shuttle electrons, they pump protons from the mitochondrial matrix into the …………………..
intermembrane space
142
electron carriers are spatially arranged in the inner mitochondrial membrane in such a way that hydrogen is accepted from the …………………….. and deposited in …….…………...
mitochondrial matrix
| intermembrane space
143
what is the hydrogen gradient in the electron transport chain referred to as
a proton-motive force - the force drives hydrogen back across the membrane through the hydrogen channels provided by ATP synthases
144
over which membrane do prokaryotes generate their proton gradient
over the plasma membrane - their proton-motive force allows them to make ATP, rotate their flagella and pump nutrients and waste products across the membrane
145
describe the energy flow during respiration
glucose --> NADH --> electron transport chain --> proton-motive force --> ATP
146
why can we not state an exact number of ATP molecules generated by the breakdown of one molecule of glucose
1. phosphorylation and redox reactions are not directly coupled to each other, so the ratio of NADH:ATP is not a whole number. 1 NADH results in 10H+ being pumped across the inner mitochondrial membrane and 4H+ are needed to generate 1ATP (not known for sure) so 1NADH generates 2.5 ATP
2. ATP yield varies slightly depending on the type of shuttle used to transport electrons from the cytosol to the mitochondrion. the electrons captured by NADH in glycolysis are passed to either NAD+ or FAD - more ATP is produced using NAD+ compared to FAD
3. the proton motive force can be used to drive other types of work e.g. mitochondria's uptake of pyruvate from the cytosol
147
what percentage of the chemical energy in glucose is transferred to ATP
approximately 34%
148
fermentation and anaerobic respiration enable cells to produce ATP in the absence of what
oxygen
149
why does ATP yield from aerobic respiration depend on adequate supply of oxygen
because most of the ATP generated is due to the work of oxidative phosphorylation - without the electronegative oxygen to pull electrons down the transport chain, oxidative phosphorylation eventually ceases
150
what is the difference between fermentation and anaerobic respiration
an electron transport chain is used in anaerobic respiration but not in fermentation
151
what organisms use anaerobic respiration
some prokaryotic organisms that live in environments without oxygen
152
instead of oxygen what tends to be at the end of the electron transport chain
sulfate ion SO4-
153
in anaerobic respiration when a sulfate ion replaces oxygen in the electron transport chain what is the by-product instead of water
hydrogen sulphide
154
what is fermentation
a way of harvesting chemical energy without using oxygen or an electron transport chain i.e. without cellular respiration
155
what is the oxidising agent of glycolysis
NAD+
156
glycolysis doesn't generate ATP in the absence of oxygen TRUE/FALSE
FALSE - oxygen has no effect on glycolysis, glycolysis yield 2 ATP whether oxygen is present or not
157
fermentation is an extension of glycolysis that allows continuous generation of ATP by ……………………. phosphorylation of glycolysis
substrate-level
158
for fermentation to occur there must be a sufficient supply of ……….. to accept electrons during the oxidation step of glycolysis
NAD+ - although this is always regenerated as under anaerobic conditions the electrons are transferred to pyruvate
159
name two types of fermentation
alcohol fermentation
| lactic acid fermentation
160
describe alcohol fermentation
pyruvate is converted into ethanol in two steps
1. carbon dioxide is released from the pyruvate which is converted to the two carbon compound acetaldehyde
2. acetaldehyde is reduced to ethanol by NADH - this regenerates the supply of NAD+ needed for continuation of glycolysis
161
what organisms often carry out alcohol fermentation under anaerobic conditions
many bacteria
| yeast (fungus) carries out alcohol fermentation in addition to aerobic respiration
162
describe lactic acid fermentation
1. pyruvate is reduced directly by NADH to form lactate as an end product, regenerating NAD+ with no release of CO2
163
where is lactic acid fermentation used in industry
in the dairy industry to make cheese and yoghurt
164
where is alcohol fermentation used in industry
baking and brewing
165
which body cells use lactic acid fermentation
human muscle cells make ATP by lactic acid fermentation when oxygen is scarce - during strenuous exercise when sugar catabolism for ATP production outpaces the muscles supply of oxygen from the blood
166
what happens to the lactic acid produced in the body
blood carries the excess lactate from the muscles to the liver where it is converted back to pyruvate by the liver cells
the pyruvate can then enter the mitochondria in liver cells and complete cellular respiration
167
what are obligate anaerobes
organisms that carry out only fermentation or anaerobic respiration and cannot survive in the presence of oxygen
168
what are facultative anaerobes
organisms that can make enough ATP to survive by using either fermentation or respiration
169
which cells can behave as facultative anaerobes
muscle cells
170
explain the use of proteins as a fuel for respiration
they can be broken down into their constituent amino acids and made into new proteins
any excess amino acids are converted by enzymes to intermediates of glycolysis and the citric acid cycle
before the amino acids can be used their amino groups must be removed (deamination)
the nitrogenous waste from the amines is excreted
171
explain the use of fats as a fuel for respiration
fats can be broken down into fatty acids and glycerol
glycerol is converted to glyceraldehyde-3-phosphate - an intermediate of glycolysis
beta oxidation breaks fatty acids down to 2-carbon fragments which enter the citric acid cycle as acetyl coA
172
………….. are better fuels for respiration compared to carbohydrates
fats
173
compounds formed as intermediates of glycolysis and the citric acid cycle can be diverted into anabolic pathways as precursors for which cells can synthesise the molecules they require TRUE/FALSE
TRUE
174
which intermediate of glycolysis can be converted to one of the major precursors of fats
dihydroxyacetone phosphate (DHAP)
175
how does feedback inhibition provide control
the end product of the anabolic pathway inhibits the enzyme that catalyses an early step of the pathway
176
what happens to respiration rate when there is a plentiful supply of ATP
it slows down
177
how can respiration rate be slowed down
step 3 of glycolysis, catalysed by phosphofructokinase is the first step that irreversibly commits the substrate to the glycolytic pathway. by controlling this step we can control the speed of the entire process
178
which enzyme is considered a pacemaker for respiration
phosphofructokinase
179
what stimulates phosphofructokinase
AMP - derived from ADP
180
what inhibits phosphofructokinase
ATP and citrate
181
what type of enzyme is phosphofructokinase
an allosteric enzyme
182
where do the different steps of respiration occur
glycolysis - cytosol
pyruvate oxidation - mitochondrial matrix
citric acid cycle - mitochondrial matrix
oxidative phosphorylation - mitochondrial cristae
