Lecture 5: Cellular Respiration Flashcards
(103 cards)
1
Q
What is the ultimate source of energy
A
The sun
2
Q
Functions of photosynthesis
A
- captures the energy of light
- converts it to chemical energy (complex organic molecules)- these act as a source of fuel via cellular respiration
3
Q
How do cyanobacteria receive energy
A
trap solar energy and convert it into energy
4
Q
Cellular respiration is a what kind of reaction
Hint: exergonic or endergonic
A
Exergonic
5
Q
The transfer of energy uses
A
Negative Gibbs energy (capable of work) to build energy (ATP)
6
Q
glucose contains
A
electrons at high energy levels, making it unstable (CATABOLIC)
7
Q
process and products of energy flow
A
process: photosynthesis to glucose to cellular respiration (powered by ADP and free phosphate into ATP) and removal of an O2 to form CO2+ H2O (stable, and low energy level electrons)
PRODUCTS: CO2 and H2O which contain electrons at low energy levels
8
Q
What do gasoline and glucose have in common
A
- abundance of C-H bonds
- good source of energy because its a np bond that shares electrons equally (electrons are equidistant)
- stores energy
9
Q
When electrons move towards atomic nucleus energy is
A
released (can be captured to make ATP)
10
Q
To move an electron away
A
- moving from a lower energy level to a higher energy level, you are absorbing energy
11
Q
to move an electron inwards
A
- moving an electron closer to the nucleus, you are losing energy
12
Q
The EN difference between CH bonds
A
0.4 difference
13
Q
How do we get the energy that is stored in organic molecules
A
Oxidize it to remove the electrons
- the donor is oxidized=losing electrons
- acceptor is reduced=gains electrons
REDOX reaction (transfer of electrons from donor to acceptor atoms)
14
Q
What is going to be able to remove the electrons
A
- An oxidizing agent which has a higher EN than the other atom so the electrons have a greater pull towards the oxidizing agents nucleus
15
Q
One of the strongest oxidizing agent
A
Oxygen
- this can be dangerous, because O2 has a very strong pull of electrons
- can take electrons from carbs, proteins, DNA therefore we have to control it
O2 gets 4 electrons all at the same time and with H2O because it avoids reactant o2 species and instead goes straight to form H2O
16
Q
Equal sharing of electrons between C-H bonds means
A
they have lots of energy which keeps them away from the nucleus
17
Q
CH4 + 2O2 = CO2 + ENERGY + 2H2O
Why energy?
A
- release of energy, we went from high energy to unstable reactants to low energy stable products
- the high energy and unstable CH4 becomes oxidized into a more stable CO2, and 2O2 becomes 2H2O which is also more stable
(DUE TO THE EN DIFFERENCE BETWEEN C, H, O, AND N)
18
Q
Cellular respiration
A
- organisms obtain energy by oxidizing organic molecules produced by photosynthesis in a series of reactions
- energy released in oxidation is captured in ATP
19
Q
Cellular Respiration is what kind of reaction (aside from redox)
A
Controlled combustion
- whichever way you undergo cellular respiration, the G doesn’t change
- Enzyme control lets us capture and harness released energy to be sent to the carrier molecules
- VERY EFFICIENT, ESP DUE TO ENZYMES
20
Q
Energy transfer
A
- electrons lose energy as they pass from donor to acceptor molecule
- released energy is free energy that can do work
- in cellular respiration, end result is ATP synthesis
21
Q
What will carry the energy through this process
**what will carry the electrons
A
NAD+ (oxidized form of NADH)
- dehydrogenase (has another H)
- they help give us electrons by carrying them
22
Q
REDOX from NAD+ to NADH
A
NAD+ + 2e- + H+ = NADH
23
Q
What are the 3 stages of cellular respiration
A
1) glycolysis (substrate level phosphorylation), occurs in cytosol
2) citric acid cycle (substrate level phosphorylation) , occurs in mitochondria
3) electrons transport and chemiosmosis (oxidative level phosphorylation), occurs in mitochondria
24
Q
Glycolysis
A
- glucose (6 carbons) is converted:
- through oxidation to 2 molecules of pyruvate (3 carbons each) through series of enzyme catalyzed reactions (10 steps)
- ATP and NADH synthesis through electron removal that is delivered to NAD+ producing NADH
25
Citric Acid Cycle
- 8 enzymatic reactions
- oxidize pyruvate
- acetyl-CoA
- enters the metabolic cycle
- collecting electrons so that NAD+ can product NADH
- oxidizied completely to CO2
- synthesis of atp, nadh, fadh2
26
Electron transport and chemiosmosis
NADH is synthesized by glycolysis and citric acid cycle is oxidized (also FADH2)
- Free e- pass along etc
- electrons transferred to O2 (water) (electron carriers, thet donate electrons to ETC)
- free energy establishments proton gradient across membrane
- Drive ATP synthesis
27
Mitochondria and cellular respiration
- location for. most cellular respiration
- but prokaryotes don't have mitochondria
28
Inner mitochondrial membrane
- electron transfer
- ATP synthesis and ATP synthase
- matrix= reactions involving electrons
29
What does each glucose molecule oxidized produce
- 2 ATP
- 2 NADH
- 2 Pyruvate
- 2 water
(pyruvate and water produced from glucose)
30
Energy input and output during glycolysis
Energy investment: consumption of ATP to move through
Energy Harvest: made 4 atp, (net gain of 2 atp), remove electrons and make NADH
31
Steps 1-3 of glycolysis
1) glucose receives PO4 from ATP to produce G6P
2) G6P is rearranged into isomer to F6P
3) PO4 from ATP is attached to F6P to form F1,6BP (* uses phosphofructokinase)
1,3= phosphorylation
2= isomerization
32
Phosphofructokinase
regulated enzyme involved in step 3 of glycolysis
- regulates cellular respiration
- adding PO4 (which is unstable) on glucose (already unstable) which makes it MORE UNSTABLE so it looses MORE ENERGY
33
Steps 4-5 of glycolysis
4) F1,6BP is split into G3P and DAP (hydrolysis)
5) DAP produced is concerted to into G3P giving 2 G3P per one glucose (isomerization)
- 1 sugar= 2 G3P (only one that moves ahead)
34
Steps 6-7 of glycolysis
6) 2 electrons and 2 protons are removed from G3P, some of the energy released in this reaction is trapped by the addition of inorganic PO4 from cytosol (NOT ATP)
electrons are accepted by NAD+ along with 1 H+ the other H+ os released to cytosol (redox reaction)
7) One of the two phosphate groups of 1,3BPG is transferred to ADP to make ATP (substrate level phosphorylation) ***powered by kinase****
- production of 2ATP by substrate level phosphorylation
- Synthesis of 2 NADH by redox reactions
35
Steps 8-10 of Glycolysis
1) Energy output via PEP
- production of 2 ATP by substrate level phosphorylation
- 2 pyruvate=less PE than glucose
8) 3PG is rearranged shifting to the PO4 from C-3 to C-2 to make 2PG (mutase reaction)
9) E- are removed from 1 part of 2-PG and delivered to another part of the molecule. Most of the energy lost by the electrons is retained in the product...PEP (redox)
10) Remaining PO4 is removed from PEP and transferred to ADP, the reaction forms ATP and the final product of glycolysis=PYRUVATE
(substrate level phos.)
36
What is substrate level phosphorylation
- enzyme catalyzed reaction
- transfers PO4 from substrate to ADP to form ATP (can also be GDP to GTP)
37
What is mutase
shifting of a chemical group to another within the same molecule
38
ATP molecules are produced in
- glycolysis from substrate level phosphorylation
39
is ATP synthesis the same in the forms of cellular respiration.
- same in citric acid cycle as glycolysis
- at the end of etc, they use ATP synthase (unique to etc only)
- no phosphorylation
- different in oxidative phosphorylation and chemiosmosis
40
Pyruvate Oxidation in the Krebs cycle
- pyruvate must be modified to enter the Krebs cycle via pyruvate oxidation
- removal of Carboxyl group and moves a few e-
= acetyl-CoA can enter Krebs
- this is dehydrogenation and decarboxylation and the acetyl-CoA is a high energy intermediate
41
What is dehydrogenation
removal of Hydrogen from organic molecule
42
What is pyruvate oxidation
- takes place in the mitochondrial matrix
- pyruvate oxidized to acetyl groups (2C)
- electrons removed are accepted by NAD+, acetate is produced by oxidation, and that energy is used to make NADH
- CO2 is produced and released to increase the entropy of the system contributing to disorder
43
What does each pyruvate molecule produce
| when it initially is brought into krebs
- 1 acetyl group
- 1 NADH
- 1 CO2
44
Acetyl groups are attached to
conenzyme A and then delivered to citric acid cycle
45
Pyrvuate to glucose ratio
2 pyruvate per 1 glucose
46
Pyruvate oxidation REACTION
pyruvate + CoA + NAD+ = acetyl-CoA + NADH + H+ + CO2
47
Acetyl groups are oxidized in the citric acid cycle to form what
CO2 (low energy, stable)
48
Electrons removed in Oxidations are accepted by
NAD+ or FAD to form NADH and FADH
49
Citric Acid Cycle produces what through substrate level phosphorylation
2 acetyl groups
Each one forms (via oxidation)
- 2 CO2
- 1 ATP
- 3 NADH
- 1 FADH2
50
Citric Acid Cycle summarization (the reactions specifically)
High energy acetyl CoA
Isomerization: e- will go to NADH, CO2 loss (REDOX)
NAD to NADH= CO2 loss again, (REDOX)
Succinyl CoA synthesizes ATP
Redox Reaction to form FADH2 from FAD
Addition of water=HYDRATION
NAD+ to NADH again=REDOX Reaction to resupply acetyl-CoA
51
ETC and chemiosmosis
- respiratory ETC:
- Inner mitochondrial membrane
Includes: 4 major protein complexes
- 2 smaller shuttle carriers
- electrons passed from NADH and FADH2 to O2 through carriers
- O2 is the final electron acceptor
- Electrons are depleted of energy
- Some energy used by complexes 1 and 4 to pump H+ across the inner mitochondrial membrane = electrochemical gradient
52
ETC is a what type of reaction
Catabolic reaction, transfer chemical energy to generate ATP and release free energy
53
How will protons return back to their original position in the ETC
- will use ATP synthase as a transport protein to re-enter
54
Whenever we transfer electrons, we are also transferring free energy
1) when UQ pick up electrons, it also grabs H+
2) when e- are given to O2 and they form H2O
= contributes to EN gradient
55
What is the electrochemical gradient
Proton motive force=action of moving protons
56
the inter membrane component is
more acidic than mitochondria
57
UQ will do what
neutralize grabbing H+ with hydrophobic core and negative charge
58
the protons that will move will naturally want
to go back down to their lower concentration using ATP synthase
59
Chemiosmosis
ATP synthase catalyzes ATP synthesis using energy from the H+ gradient across the membrane
60
REDOX components of ETC
- prosthetic groups will help transfer electrons (ex. heme)
- establishes electrochemical gradient (which eventually will drive ATP production) = NO ATP production
61
prosthetic groups in the ETC
- prosthetic groups in proteins accept the electrons and move down ETC
- free energy here= moves electrons across, free energy down
* because as we move the electrons down the prosthetic groups, they have an increase in EN allowing the electrons to move and energy to be lost *
62
the ETC is what kind of reaction
- exergonic
- catabolic
- spontaneous
63
Oxidative phosphorylation and chemiosmosis
- ATP synthase catalyzes ATP synthesis using energy from the H+ gradient across the membrane (chemiosmosis)
64
ATP synthase
- a molecular motor
- driven by proton motive force
- rotation in the enzyme (driven by p+ motive force which generates ATP)
- embedded in the inner mitochondrial membrane with electron transfer system
* indirectly connected and work together to move H+ to drive ATP production *
65
Uncoupling of ETC and ATP synthesis
If H+ from the ETC comes in via uncouplers through ionophores and don't enter atp synthase (as they usually would to go back to proper position) we make 0 ATP
66
problem with uncouplers
- toxic to cells
- prevents our cells from making ATP
67
purpose of ionophores
- can be used to create pores and channels to let ions to come through (h+) to uncouple atp
68
efficiency of cellular respiration
- more than 30% efficiency for utilization of energy released by glucose oxidation
*IFF THE H+ GRADIENT IS USED ONLY FOR ATP*
- the other 70% was transferred as thermal energy which can be used for homeostasis, but we don't use most of it which contributes to disorder
69
purpose of oxaloacetate
Oxaloacetate is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate
70
When cells are stressed
they produce less ATP or produce more if in ideal conditions
71
Approximate ATP production
| amongst e- carriers
1 NADH = 2.5 ATP
1 FADH2= 1.5 ATP
- dependent on environment of cell
72
T/F only glucose produces usable energy of atp
f, fats and proteins can do the same
73
AMP does what...
Activates phosphofructokinase enzyme which then turns F6P into F16BP and so on
74
Major Inhibitor of phosphofructokinase enzyme
ATP
- if too much ATP is made in excess, it will bind to phosphofructokinase and turn it off
75
Inhibitor of phosphofructokinase enzyme
- citrate (intermediate of Krebs), in excess amounts will inhibit the enzyme
76
Knowing that we can consume ADP and thus AMP, if ATP and ADP supply is low....
AMP that accumulates bonds to the phosphofructokinase enzyme as an allosteric enzyme and increases its affinity state
So, we go from allosteric activator to feedback inhibition
77
O2 and cellular respiration
GLYCOLYSIS (anaerobic)
Glucose ---- Pyruvate
If O2 is present
- citric acid cycle and ETC w/ oxidative phosphorylation (cell resp)
If O2 is NOT present
- fermentation
78
What is fermentation
- occurs in cytosol in prokaryotes and eukaryotes
- instead of driving e-, they will be donated to an organic molecule
(ex. NADH will deliver electrons to donate to organic acceptor molecules)
- converting NADH back to NAD+ which keeps glycolysis going
- Pyruvate is reduced
79
ATP production in fermentation
small amount temporarily that is enough for the time being
- purpose is to keep glycolysis going
80
NAD+ in fermentation
is free to accept more electrons, removed from sugars in glycolysis
81
Types of fermentation
a) lactate: Pyruvate with electrons donated from NADH will form lactate and ATP
b) alcoholic: NADH move electrons to NAD+
- this cycle drives more glycolysis which produces more ATP
- pyruvate is decarboxylated (-co2) to form acetaldehyde to form ethyl alcohol
82
Cell resp in prokaryotes
- Anaerobic respiration
prokaryotes: respiratory etc on internal membrane systems
- there's still glycolysis
- there's still krebs
- there's still ETC but O2 is not the final e acceptor
- Sulfur, Nitrate, and Ferric Ion will create gradients to generate ATP
83
Strict Anaerobes
cannot grow in o2 (can't avoid reactive oxidative species)
84
Strict Aerobes
Require oxygen (humans for example)
85
Facultative Anaerobes
Can grow in O2 and can grow using fermentative pathways (Can do cellular resp. , if O2 Is depleted they can shift to anaerobic resp. example is yeast)
86
If we gave O2 1/4 e- we would form
superoxide
- has a higher EN than water which forms H2O2 (strong oxidizing and toxic agent) and peroxisomes use catalase to convert this into water
- H2O2 can also turns into hydroxyl radical which is even stronger oxidizing agent and that can turn into H2O too
87
Defence against ROS (Reactive Oxygen Species)
- includes superoxide, H2O2, and hydroxyl radical: strong oxidizing agents that can lead to cancer, Alzheimer's, and heart disease
Antioxidant defence system
- enzymes
- superoxide disumutase and catalase
Nonenzymes
- antioxidants: vitamin C and vitamin E (We can take electrons from the ROS go we can get to H2O faster
88
what is the ultimate source of organic carbon used to synthesize carbs, fats, and proteins
photosynthesis
thus, earths life is dependent on a cycle of energy flow between photosynthesis and respiration
89
equidistant electrons
contains greater energy because its held further from the nucleus
90
molecules that have oxygen have
less free energy because oxygen is too electronegative so electrons are held too close to the nucleus of the oxygen atom
91
why does 1g of fat contain more energy than 1g of protein
- fat = entirely C-H bonds essentially, but proteins and even carbs can have Oxygen and Nitrogen which have a high EN
92
polar bonds are stable because
electrons are held close to electronegative atoms, harder to involve in chemical reactions
93
cellular respiration and controlled combustion
- exergonic with the same G (-686kcal/mol) as if it were driven by enzymes (bring molecules to the transition state by lowering the activation energy the way a flame would provide the activation energy to get molecules to the transition state
Diff: if you burn glucose the energy is released as heat and is unable to drive metabolic reactions, therefore its controlled combustion as the potential energy of glucose is not liberated suddenly but released slowly with a lot of the energy being transferred to other molecules
94
what is the efficiency of the enzyme catalyzed transfer of energy between food and NAD+
- via dehydrogenase enzyme
- high efficiency because the free energy difference is small, meaning its available to downstream reactions
95
PE in NADH is used
to make ATP
96
anatomy of mitochondria
- two membranes : outer and inner
- intermembrane space : between outer and inner membranes
- matrix : interior aq environment
97
what supports the idea that glycolysis is the most fundamental and ancient pathway
1) glycolysis is universal and found in all 3 domains: Archea, bacteria, and eukarya
2) Glycolysis doesn't depend upon O2
4) uses soluble enzymes and occurs in cytosol (which all cells have), doesnt require transport chains or internal membrane systems
98
the potential energy in the 2 pyruvates produced at the end of glycolysis
is less than glucose because the glucose was oxidized
- but they still have usuable free energy that can be harvested as NADH and ATP
99
remaining carbon atoms from glucose at start of glycolysis are now
converted into CO2
100
the PE from glucose
is NADH and FADH2, process of chemiosmosis extracts the PE in these molecules to synthesize additional ATP
101
partially reduced forms of O2 are formed when O2 accepts fewer electrons to produce
ROS
102
Which enzymes are the most scavenging against H2O2
catalase
dismutase
103
Why do strict anaerobes die in the present of O2
1) inability to live because they lack enzymes
2) O2 binds itself to metabolic enzymes
