Chapter 5 - cellular respiration Flashcards
(75 cards)
1
Q
what does the cellular respiration do?
A
- Breaks down carbohydrates, lipids, and proteins
- Converts energy that is liberated into ATP
- Allows the cell to do work
2
Q
What is cellular respiration?
A
Collection of metabolic reactions within cells that breaks down food molecules (catabolic reactions) to produce ATP
3
Q
What is ATP?
A
ATP is the form of chemical energy required for thousands of biosynthetic reactions (anabolic reactions) taking place within the cell
- produced in glycolysis
- Result from substrate-level phosphorylation
4
Q
Where is energy coming from?
A
- The Sun: Ultimate source of energy for most organisms
- Photosynthesis: Captures energy of sunlight; Converts it to chemical energy of complex organic molecules
5
Q
What happens in cellular respiration?
A
Photosynthesis uses light energy to convert carbon dioxide and water into energy-rich organic molecules,
such as glucose, which, in turn, are oxidized by cellular respiration.
6
Q
What are the two fuel molecules
A
gasoline and glucose
7
Q
What is a Oxidation-Reduction (Redox)
Reaction?
A
Chemical reactions in which electrons are transferred from one atom or molecule to another
1. Loss of Electrons = Oxidation
2. Gain of Electrons = Reduction
8
Q
Explain oxidation
A
- The partial or full loss of electrons from a substance
- The substance from which the electrons are lost (the e- donor) is oxidized
9
Q
Explain reduction
A
- The partial or full gain of electrons to a substance
- The substance that gains the electrons (the e- acceptor) is reduced
10
Q
what is a redox reaction
A
Redox reactions are coupled reactions: The oxidation reaction and the reduction reaction occur simultaneously
11
Q
cellular respiration is ….
A
controlled combustion
12
Q
what is NAD+
A
NAD+ is the oxidized form of an electron carrier. Two electrons and a proton are added to produce the
reduced form, NADH
13
Q
equation for cellular respiration
A
Glucose+ Oxygen = Carbon dioxide + Water + energy
14
Q
steps of cellular respiration
A
- Glycolysis (cytosol)
- Pyruvate oxidation and the citric acid cycle (mitochondria)
- Oxidative phosphorylation
(mitochondria)
15
Q
The parts of a mitochondria
A
- Most reactions of cellular respiration take place in
mitochondria.
1. inner mitochondrial membrane: electron transfer; ATP synthesis by ATP synthases
2. Matrix: pyruvate oxidation and the citric cycle
3. intermembrane compartment: is between inner and outer membrane
4. outer mitochondrial membrane
16
Q
Reactions of glycolysis
A
- Glycolysis is a universal and ancient metabolic process
- Glycolysis occurs in cytosol of all cells, and involves a series of soluble enzymes
- First ATP consuming reaction
- Second ATP consuming reaction
- Cleavage of 6 carbon sugar to two 3-carbon molecules - Pyruvate (2 molecules)
17
Q
Summarize glycolysis
A
- Glycolysis does not require O2
- Series of 10 chemical reactions, each catalyzed by a different enzyme, and that can be grouped into an ”energy investment” phase, and an “energy payoff” phase”
- Converts glucose (6 carbons) into two molecules of pyruvate (3 carbons each)
18
Q
what is the substrate level phosphorylation?
A
- Substrate-level phosphorylation
* Enzyme-catalyzed reaction
* Transfers phosphate group from substrate to ADP - - A phosphate group is transferred from a high-energy donor directly to ADP, forming ATP - Substrate-level phosphorylation produces only a small amount of the ATP generated in cellular respiration
19
Q
Most of the ATP produced during
cellular respiration is generated
during ……
A
oxidative phosphorylation
20
Q
Where does pyruvate oxidation take place?
A
mitochondria
21
Q
What type of group is pyruvate oxidized to?
A
acetyl group
22
Q
_____________ is produced when pyruvate is oxidized with an acetyl
A
CO2
23
Q
what happens during pyruvate oxidation?
A
- Electrons removed are accepted by (or used to reduce) NAD+ to form NADH
- Acetyl group linked to Co-Enzyme A (CoA)
- Pyruvate oxidation converts pyruvate to acetyl-CoA. This process is aerobic.
- Pyruvate oxidation occurs within the mitochondrial matrix
24
Q
What is the product of each pyruvate molecule?
A
- 1 acetyl group
- 1 NADH
- 1 CO2
25
what is an acetyl group attached to?
coenzyme A
26
Pyruvate oxidation links _______________________
glycolysis and the citric acid cycle
27
At the End of Pyruvate Oxidation
1 pyruvate molecule yields:
* 1 acetyl-CoA
* 1 CO2
* 1 NADH
28
During glycolysis, glucose produced
2 pyruvate molecules
29
What takes place in the citric acid?
* Acetyl groups completely oxidized to CO2
* Electrons removed in a series of oxidations
- Accepted by NAD+ or FAD (which get reduced to NADH and FADH2)
* Some ATP made by substrate-level phosphorylation
30
Each acetyl group that enters the cycle and gets oxidized produces what?
* 2 CO2
* 1 ATP
* 3 NADH
* 1 FADH
31
other names of the citric acid are ....
tricarboxylic acid cycle or Krebs cycle
32
summarize the citric acid
The eight reactions of the citric acid cycle (tricarboxylic
acid cycle or Krebs cycle) oxidize acetyl groups
completely to CO2, generate 3 NADH and 1 FADH2, and
synthesize 1 ATP by substrate-level phosphorylation
33
At the end of the cycle two molecules of acetyl - CoA yield_______________
* 2 ATP
* 6 NADH
* 2 FADH2
34
What is the electron transfer system ?
The electron transport chain converts the potential energy in NADH and FADH2 into a proton-motive
force, which is used to drive ATP synthesis
35
Explain the stages of electron transfer
Stages 1 - 2:
Glucose is oxidized through a series of chemical reactions, releasing energy in the form of ATP and reduced electron carriers.
Stage 3:
Electron carriers donate electrons to the electron transport chain, leading to the synthesis of ATP.
- oxidative phosphorylation, the reduced electron carriers generated in stages 1-2 donate electrons to the
electron transport chain and a large amount of ATP is
produced
36
Electrons pass from NADH ____________
FADH2 to O2
37
Electron Transport Chain includes:
* 4 protein complexes
* 2 smaller shuttle carriers
*Electrons move spontaneously along the
electron transport chain
38
what are 3 major protein complexes of the Respiratory Electron Transport Chain?
I, III, and IV
* Pump H+ from Matrix to IMS
* Contain prosthetic groups that
cycle between reduced and
oxidized states
39
What happens to the electrons in the respiratory electron transport chain ?
- the electrons are depleted of energy
- they are Delivered to oxygen as final
electron acceptor
40
The complete oxidation of glucose
during stages 1-2 of cellular respiration
results in the production of _____________
the reduced electron carriers, NADH and FADH2
41
The electron transport chain consists of four complexes (I to IV) in the____________________
inner mitochondrial membrane
42
the steps of the electron transport:
1. Electrons donated by NADH and FADH2 are transported along the series of ETC complexes
2. Complexes I and II harvest electrons from NADH and FADH2
3. Coenzyme Q (or Ubiquinone) is reduced to CoQH2 and transfers electrons from complexes I and II to complex III.
4. Cytochrome c moves to complex IV where oxygen is reduced to form water
5. Within each protein complex of the ETC, electrons are passed from electron donors to electron acceptors
6. When oxygen accepts electrons at the end of the ETC, it is reduced to form water
43
Explain Proton transport and ATP synthesis:
- The transport of electrons in complexes I, III, and IV is coupled with the transport of protons across the inner membrane, from the mitochondrial matrix to the intermembrane space
- ATP synthase uses the electrochemical proton gradient to drive the
synthesis of ATP
- Due to the proton pumping of the ETC, protons have a high concentration in the intermembrane space and a low concentration in the mitochondrial matrix. The proton concentration gradient contains high potential energy
44
ATP synthase catalyzes ATP synthesis
using energy from _______________
H+ gradient across the membrane
45
What is chemiosmosis?
ATP synthase catalyzes ATP synthesis using energy from the H+ gradient across the membrane
46
What is ATP synthase?
* Molecular motor
* Embedded in inner mitochondrial membrane with electron transfer system
47
What does ATP synthase do?
ATP synthase converts the energy of the proton gradient into the energy of ATP
48
Electron transport and chemiosmotic generation of ATP are separate and distinct processes. TRUE OR FALSE
TRUE
49
Where can energies be extracted from?
Besides simple sugars, energy can be extracted from fats, proteins, and carbohydrates that enter the respiratory chain at different points
50
Explain respiratory intermediates.
- Intermediates of glycolysis and the citric acid cycle are routinely diverted and used as starting substrates to synthesize amino acids, fats, and the pyrimidine and purine bases needed for nucleic acid synthesis
51
What do respiratory intermediates supply?
carbon backbones for hormones, growth factors, prosthetic
groups, and cofactors essential to cell function
52
What is meant by carbon backbones?
carbon skeleton; carbon atoms make up the backbone of many important molecules in your body, including proteins, DNA, RNA, sugars, and fats (macromolecules)
53
In anaerobic respiration, what is not the terminal electron acceptor?
Oxygen
54
What results in fermentation?
low oxygen levels
55
What is fermentation?
pathway of respiration that oxidizes fuel molecules in the absence of oxygen
56
what are two types of fermentations that are anaerobic?
- lactate fermentation
- alcohol fermentation
57
What happens when oxygen is present in aerobic respiration ?
pyruvate is converted to acetyl-CoA, which then enters the citric acid cycle,
followed by the ETC
58
In what type of respiration is oxygen not present? and what happens?
in anaerobic respiration oxygen is not present. When oxygen is not
present, pyruvate is metabolized along a number of different
pathways
59
What is produced in fermentation and where is it used?
NAD+ produced in fermentation is used in glycolysis
60
The breakdown of glucose by fermentation yields what?
only 2 molecules of ATP, since lactic acid and ethanol are not fully oxidized and still contain a large amount of chemical energy in their bonds.
61
what does lactic fermentation occur in?
animals and bacteria
62
What happens in lactic fermentation?
Electrons from NADH are transferred to pyruvate to produce lactic acid and NAD+
63
What does alcoholic fermentation occur in?
plants and fungi
64
What happens in alcoholic fermentation?
Electrons from NADH are transferred to pyruvate to produce ethanol and NAD+
65
What do anaerobic respiration lack?
mitochondria, many bacteria and archaea have respiratory electron transport chains, located on internal membrane systems
66
what are some common electron acceptors?
Sulfate, nitrate, and ferric ion
67
what are Strict anaerobes?
Cannot grow in presence of oxygen
68
What do Strict aerobes require?
Require oxygen
69
what are Facultative aerobes?
they can grow in presence of oxygen and can grow using fermentative pathways
70
Reactive oxygen species (ROS).....
* Include superoxide and hydrogen peroxide
* Strong oxidizing agents
71
what does reduction of oxygen to water result in?
results in the formation of the intermediate ROS, which are potentially harmful
72
what are some defence mechanisms against reactive oxygen species?
* Antioxidant defence system
- Enzymes
* Superoxide dismutase and catalase
* Non enzymes
- Antioxidants: vitamin C and vitamin E
73
what is phosphofructokinase?
PFK is an allosteric enzyme
74
In eukaryotes ( plants), what is oxygen?
it is a terminal electron acceptor
75
doneee
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