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Cellular Respiration Flashcards

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1
Q

What occurs in an oxidation reaction?

A

An oxidation reaction strips an electron from an atom in a compound, and the addition of this electron to another compound is a reduction reaction. Because oxidation and reduction usually occur together, these pairs of reactions are called oxidation reduction reactions, or redox reactions.
RECALL: O.I.L.R.I.G
Oxidation is loss of electrons & Reduction is gain of electrons.

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2
Q

What is Cellular Respiration (CR)?

A

Is any set of reactions that uses electrons from high-energy molecules to make ATP

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3
Q

RECALL….

A
  1. Life requires energy
  2. ATP fuels work in cells
  3. Metabolic pathways harvest energy from high-energy molecules, such as glucose
  4. The energy released is used to add a phosphate group to ADP to make ATP. Adding a phosphate group to ADP is called phosphorylation.
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4
Q

Is C.R. a catabolic process or anabolic process?

A

Catabolic

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5
Q

Where do cells get ATP from?

A

Cells obtain glucose to make ATP:
Plants - produce glucose during photosynthesis

Other organisms - obtain glucose from food

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6
Q

How do organism store glucose?

A

Either as glycogen or starch.

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7
Q

What Happens When Glucose Is Oxidized?

A

When glucose is oxidized to carbon dioxide by burning, some energy is released as heat and light.
This can be seen in the C.R. formula.
In cells, glucose is oxidized through redox reactions. Instead of being wasted on heat and light, much of the energy released is used to synthesize ATP. These reactions comprise cellular respiration.

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8
Q

What is the basic equation for C.R.?

A

C6H12O6 + 6O2 ARROW 6CO2 + 6H2O + ~36ATP

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9
Q

What macromolecule would be the best to produce ATP?

A

First - carbohydrates
Second - fats
Third - proteins

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10
Q

What Happens When Glucose Is Oxidized?

A

The 4 Cellular respiration processes.

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11
Q

What are the four cellular process?

A

​1. Glycolysis—A six-carbon glucose is broken down into two 3-carbon pyruvate molecules
​2. Pyruvate processing—Each pyruvate is oxidized to form acetyl CoA (a 2-carbon molecule)
​3. Citric acid cycle—Each acetyl CoA is oxidized to CO2.
​4. Oxidative phosphorylation and electron transport—Electrons move through a transport chain and their energy is used to set up a proton gradient, which is used to make ATP.

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12
Q

What biomolecules enter C.R.?

A

In glycolysis ​Glycolysis—A six-carbon glucose is broken down into two 3-carbon pyruvate molecules
​Pyruvate processing—Each pyruvate is oxidized to form acetyl C o A (a 2-carbon molecule)
​Citric acid cycle—Each acetyl C o A is oxidized to C O2
​Oxidative phosphorylation and electron transport—Electrons move through a transport chain and their energy is used to set up a proton gradient, which is used to make A T P

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13
Q

What biomolecules enter C.R.?

A

In Glycolysis: Carbohydrates, some Amino acids, & glycerol.
In Pyruvate oxidation: some Amino acids
In citric acid cycle: Fatty acids & some Amino acids

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14
Q

What are electron carriers?

A

They bind and carry high-energy electrons between compounds in pathways. The

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15
Q

What are the two principle electron carriers?

A
  1. NAD +
  2. FAD +
    Both trap electrons (e-) & protons (H+). Then transfer where they are needed.
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16
Q

What would happen to a cell if it could not release excess energy?

A

Excess free energy would result in an increase of heat in the cell, which would result in excessive thermal motion that could damage and then destroy the cell.

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17
Q

What is dephosphorylation?

A

The release of one or two phosphate groups from ATP; releases energy.

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18
Q

What is hydrolysis?

A

The process of breaking complex macromolecules apart. During hydrolysis, water is split, or lysed, and the resulting hydrogen atom (H+) and a hydroxyl group (OH-) are added to the larger molecule.

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19
Q

What occurs for the hydrolysis of ATP?

A

The hydrolysis of ATP produces ADP, together with an inorganic phosphate ion (Pi), and the release of free energy.

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20
Q

How are Life Processes Carried out?

A

ATP is continuously broken down into ADP, and like a rechargeable battery, ADP is continuously regenerated into ATP by the reattachment of a 3rd phosphate group. Water, which was broken down into its hydrogen atom and hydroxyl group during ATP hydrolysis, is regenerated when a third phosphate is added to the ADP molecule, reforming ATP.

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21
Q

What is phosphorylation?

A

Refers to the addition of the phosphate

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22
Q

What is the difference between substrate-level and oxidative phosphorylation?

A

Substrate Level: ATP is generated through 2 mechanisms during the breakdown of glucose. A few ATP molecules are generated as a DIRECT result of the chemical reactions that occur in the catabolic pathways. A phosphate group is removed from an intermediate reactant in the pathway, and the free energy of the reaction is used to add the third phosphate to an available ADP molecule, producing ATP. Substrate-Level Phosphorylation Involves an Enzyme and a Phosphorylated Substrate.

Oxidative: A much more complex process. The production of ATP uses the process of chemiosmosis that involves oxygen in the process.

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23
Q

What is Chemiosmosis?

A

A process of ATP production in cellular metabolism, is used to generate 90 percent of the ATP made during glucose catabolism and is also the method used in the light reactions of photosynthesis to harness the energy of sunlight.

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24
Q

What is glycolysis?

A

Is the first step in the breakdown of glucose to extract energy for cellular metabolism. Is anaerobic (c/o O2). Takes place in the cytoplasm of the cell.

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25
Q

How does glucose enter heterotrophic cells?

A
  1. Through secondary active transport in which the transport takes place against the glucose concentration gradient.
  2. Uses a group of integral proteins called GLUT proteins, AKA glucose transporter proteins. These transporters assist in the facilitated diffusion of glucose.
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26
Q

What does glycolysis begin and end with?

A

Begins with the six carbon ring-shaped structure of a single glucose molecule.
Ends with two molecules of a three-carbon sugar called pyruvate.

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27
Q

What are the 2 distinct phases of Glycolysis?

A
  1. The glycolysis pathway traps the glucose molecule in the cell and uses energy to modify it so that the six-carbon sugar molecule can be split evenly into the two three-carbon molecules. 2. Extracts energy from the molecules and stores it in the form of ATP and NADH, the reduced form of NAD.
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28
Q

What is the first half of glycolysis?

A

Energy-Requiring Steps

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29
Q

What is step 1 in the first half of glycolysis?

A

Is catalyzed by hexokinase, an enzyme that catalyzes the phosphorylation of six-carbon sugars. Hexokinase phosphorylates glucose using ATP as the source of the phosphate, producing glucose-6-phosphate, a more reactive form of glucose. This reaction prevents the phosphorylated glucose molecule from continuing to interact with the GLUT proteins, and it can no longer leave the cell because the negatively charged phosphate will not allow it to cross the hydrophobic interior of the plasma membrane.

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30
Q

What is step 1 in C.R.?

A

Glycolysis-Oxidizing Glucose to Pyruvate.
Glycolysis is a series of 10 chemical reactions that occur in the cytosol. It basically splits glucose in half and reformats it.
Three key points:
1. Glycolysis starts by using two ATP.
2. NADH is made and 4 ATP are produced by substrate-level phosphorylation.
3. The net yield from each glucose (a 6-Carbon molecule) is 2 NADH, 2 ATP, & 2 pyruvate (a 3-Carbon molecule).

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31
Q

Every step in Glycolysis requires…

A

An ENZYME. Example: Step 3 in the first half of glycolysis uses the enzyme phosphfructokinase.

32
Q

How Is Glycolysis Regulated?

A

By feedback Inhibition:
High levels of ATP (a product of glycolysis) inhibit the third enzyme: phosphofructokinase.
Phosphofructokinase has 2 binding sites for ATP.
1. When ATP levels are low, it binds to an activator site and the enzyme catalyzes the third step in glycolysis.
2. When ATP levels are high, it binds to a regulatory site and inhibits the enzyme.

phosphofructokinase is a rate-limiting enzyme. It is active when the concentration of ADP is high; it is less active when ADP levels are low and the concentration of ATP is high. Thus, if there is “sufficient” ATP in the system, the pathway slows down. This is a type of end product inhibition, since ATP is the end product of glucose catabolism.

33
Q

What is step 2 in C.R.?

A

Processing Pyruvate to Acetyl CoA. In eukaryotes, pyruvate produced by glycolysis is transported into mitochondria.

34
Q

What are the parts/labels of the mitochondria?

A
  1. Inner membrane
  2. Outer membranes
  3. Cristae. Are sack-like compartments formed by the inner membrane
  4. Mitochondrial matrix is inside the inner membrane.
35
Q

How is pyruvate processed into Acetyl CoA?

A

By pyruvate dehydrogenase:
1. In the mitochondrial matrix in eukaryotes.
2. In the cytosol in prokaryotes.

Pyruvate undergoes a series of reactions:
One of its carbons is removed
It is oxidized to CO2 and NADH is produced. The remaining two-carbon unit is attached to coenzyme A, producing acetyl CoA.

Pyruvate will be transformed into an acetyl group that will be picked up and activated by a carrier compound called coenzyme A (CoA). The resulting compound is called acetyl CoA

36
Q

What is the major function of Acetyl CoA?

A

It is to deliver the acetyl group derived from pyruvate to the next stage of the pathway in glucose catabolism.

37
Q

When does aerobic respiration occur?

A

If oxygen is available.

38
Q

NOTE…

A

During the second stage of glucose metabolism, whenever a carbon atom is removed, it is bound to two oxygen atoms, producing carbon dioxide, one of the major end products of cellular respiration.

39
Q

In the presence of oxygen, Acetyl CoA will…

A

Deliver its acetyl group to a four-carbon molecule, oxaloacetate, to form citrate, a six-carbon molecule with three carboxyl groups. This pathway will harvest the remainder of the extractable energy from what began as a glucose molecule. This single pathway is called The citric acid cycle.

40
Q

What is Step 3 in C.R.?

A

The Citric Acid (Krebs) Cycle - Oxidizing Acetyl CoA to CO2:
In the citric acid cycle, each acetyl CoA from pyruvate processing is oxidized into two CO2. The reactions are organized in a cycle that starts by moving the acetyl group from acetyl CoA to oxaloacetate to form citrate. At the end, oxaloacetate is regenerated.

41
Q

Where is the Krebs Cycle located?

A

Mitochondrial Matrix for Eukaryotes & cytosol for prokaryotes.

42
Q

What is the main purpose of the Krebs Cycle?

A

To generate proton & electron carriers (NADH and FADH2)

(though a couple ATP are also produced).

43
Q

The Citric Acid Cycle…

A

Completes the Oxidation of Glucose

44
Q

What occurs because of the Oxidizing of Acetyl CoA to CO2?

A

Some of the potential energy released is used to:
Reduce 3 NAD+ to NADH. Reduce 1 FAD to FADH2.
Phosphorylate ADP to form ATP.
The cycle turns twice for each glucose molecule since two pyruvate are produced by glycolysis. Total yield for the Citric Acid Cycle (for each glucose/two pyruvates):
6 NADH, 2 FADH, 2 ATP.

45
Q

What enzyme of the Krebs Cycle is not soluble?

A

Succinate dehydrogenase, which is embedded in the inner membrane of the mitochondrion.

46
Q

What Happens to the NADH and FADH2?

A

Most of glucose’s original energy is contained in the electrons transferred to NADH and FADH2. The electrons (and protons) are ultimately transferred to oxygen to form water….but not yet
Two questions remain:
What happens to the energy that is released as electrons are transferred?
How is this energy used to make ATP?

47
Q

What is step 4 in C.R?

A

Electron Transport and Chemiosmosis- Building a Proton Gradient to Produce ATP: The ETC uses the energy in NADH & FADH2 to create a steep concentration gradient of H+ ions (protons) across a membrane. NADH is oxidized (drops off its electrons) when moving through the inner membrane of mitochondria. Therefore, a concentration gradient forms in which hydrogen ions diffuse out of the matrix space by passing through ATP synthase. The current of hydrogen ions powers the catalytic action of ATP synthase, which phosphorylates ADP, producing ATP.
In prokaryotes, its oxidation involves the plasma membrane instead. What are the membrane molecules that oxidize NADH, and how do they work?

48
Q

The ETC is the only part of glucose metabolism that uses…

A

atmospheric oxygen.

49
Q

What is the ETC?

A

A series of redox reactions that resemble a relay race/bucket brigade in that electrons are passed rapidly from one component to the next, to the endpoint of the chain where the electrons reduce molecular oxygen, producing water. There are 4 complexes composed of proteins, the aggregation of these 4 complexes, together with associated mobile, accessory electron carriers.

50
Q

Where does the ETC take place?

A

Embedded within the mitochondrial membrane.

51
Q

ATP Synthase Includes a…

A

Proton-Driven Rotor and an ATP-Generating Enzyme

52
Q

What occurs as electrons move from one molecule to another in the ETC?

A

They are held more and more tightly. A small amount of energy is released in each reaction. Each successive bond holds less potential energy.

53
Q

How is the ETC organized?

A

The ETC is organized into 4 protein complexes, I – IV:
Q and cytochrome c transfer electrons b/w complexes. At the end of the ETC, low-energy electrons are passed to oxygen, along with protons.

Water is formed.

54
Q

What is the role of the ETC?

A

The electrons from NADH and FADH2 cause the protein complexes to become energized.
Protein complexes use the energy to pump (active transport) protons from the matrix into the intermembrane space.

55
Q

Free Energy Changes as Glucose Is Oxidized:

A

In each of these drops, energy is transferred to energy-storing molecules.
1. ATP
2. NADH
3. FADH2

56
Q

What is Chemiosmosis?

A

The proton gradient drives synthesis of ATP from ADP and Pi - a process called chemiosmosis

57
Q

A Series of Reduction–Oxidation Reactions Occur in an Electron Transport Chain:

A

Free energy decreases in a stepwise fashion. The last decrease in energy (converting oxygen to water) is why we breath oxygen.

58
Q

The molecules that oxidize NADH and FADH2 are collectively called the electron transport chain (ETC):

A

Most of these molecules are proteins. One is a lipid-soluble, nonprotein called coenzyme Q. They have different ability to accept electrons, called their redox potential. Some accept only electrons; others accept electrons plus protons

59
Q

How does a cell use this Gradient to harness energy?

A

With a VERY steep concentration gradient of H+
ATP production is dependent on a proton-motive force generated by the proton electrochemical gradient.

60
Q

The Proton-Motive Force Couples Electron Transport to ATP Synthesis:

A

ATP synthase is a membrane protein which facilitates chemiosmosis by acting as a proton channel. The protein consists of two components:
1. An ATPase “knob” (F1 unit)
2. A membrane-bound, proton-transporting base (F0 unit)
The units are connected by a shaft and are held in place by a stator. The F0 unit turns as protons flow through it
The spinning changes the conformation of the F1 unit so that it phosphorylates ADP to form ATP.

61
Q

What is the ATP yield from C.R?

A

The energy to produce ATP comes from a proton gradient, oxidative phosphorylation because a phosphate is added to ADP due to oxidation reactions.

Different from substrate-level phosphorylation that occurs during glycolysis and the citric acid cycle.

28-34 ATP are produced from each molecule of glucose during chemiosmosis.
The vast majority of the ATP made during C.R. is made by oxidative phosphorylation.

62
Q

Catabolic Intermediates Are Used in Anabolic Pathways

A

Cellular respiration intermediates are used to synthesize macromolecules:
1. Glycolysis intermediates can be used to make nucleotides for DNA and RNA synthesis
2. Acetyl CoA may be used for synthesis of fatty acids to build phospholipids and fats.
3. Many amino acids can be synthesized from citric acid cycle molecules.
4. Pyruvate can be used to make glucose for glycogen and starch production.

63
Q

What is the final electron acceptor?

A

Oxygen (aerobic respiration)

64
Q

What is the final electron acceptor for anaerobic respiration?

A

Bacteria use iron and manganese

65
Q

Which respiration is the most efficient?

A

Aerobic b/c using oxygen as the final electron acceptor provides the greatest energy yield:
It is highly electronegative.
It allows the generation of a large proton-motive force.

65
Q

What occurs during anaerobic respiration?

A

NADH must be reoxidized to NAD+ for reuse as an electron carrier for the glycolytic pathway to continue.

66
Q

What processes uses organic molecule to regenerate NAD+ from NADH?

A

FERMENTATION

67
Q

What is anaerobic cellular Respiration?

A

When organism convert energy for use in the absence of oxygen. At this point, living systems use either an inorganic or organic molecule as a final electron acceptor.

68
Q

What happens when there is no electron acceptor?

A

The electrons have no place to go. SO the ETC stops. NADH builds up & there is no NAD+ available to accept electrons. Ultimately glycolysis, pyruvate processing, and the citric acid cycle stop. The situation is life threatening & NAD+ must be regenerated.

69
Q

What is fermentation?

A

A metabolic pathway that regenerates NAD+ from NADH. It includes glycolysis and additional steps. Serves as an emergency backup. Glycolysis can continue to produce ATP by substrate-level phosphorylation in the absence of oxygen.

70
Q

What is Lactic Acid Fermentation?

A

When our muscle cells cannot get enough oxygen. Pyruvate produced by glycolysis accepts electrons from NADH. Lactate and NAD+ are produced. As muscle cells get more oxygen, lactate can be converted back to pyruvate. Fermentation Regenerates NAD+ So That Glycolysis Can Continue.

71
Q

What is Alcohol Fermentation?

A

Yeast cells can perform this. Pyruvate is converted to acetaldehyde and CO2. Acetaldehyde accepts electrons from NADH. Ethanol and NAD+ are produced. Prokaryotes that rely on fermentation are present in our intestines.

72
Q

How much ATP is produced from Fermentation?

A

2 ATP per glucose

73
Q

What is facultative anaerobes?

A

When some organisms can switch between fermentation and aerobic respiration. They use fermentation only if oxygen is not available.

74
Q

What enzyme is used during Lactic Acid Fermentation?

A

The enzyme used in this reaction is lactate dehydrogenase (LDH).

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