Cellular respiration in detail

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  • 1.Cellular Respiration

2. Key Concepts we will cover today. . .
Respiration is the release of energy by combining oxygen with digested food (glucose).
Carbon dioxide and waterare also produced as byproducts. They are the waste products of respiration.
Cellular respiration has two stages. First glucose is broken down to pyruvate during glycolysis, making some ATP.
The second stage involving the Krebs cycle is a series of reactions that produce energy-storing molecules during anaerobic respiration.
During aerobic respiration, large amounts of ATP are made in an electron transport chain.
When oxygen is not present, fermentation follows glycolysis, regenerating NAD+ needed for glycolysis to continue
3. Cellular Energy
Most of the foods we eat contain energy stored in proteins, carbohydrates, and fats.
Before our cells can use this energy it must be transferred to ATP within the cells.
Cells transfer the energy in organic compounds to ATP through a process calledcellular respiration.
Process cellular respiration
4. Cellular Energy

  • Oxygen in the air you breath makes the production of ATP more efficient. Some ATP is made without this oxygen however.

Metabolic processes that require oxygen are called aerobic processes.
Metabolic processes that require NO oxygen are called anaerobic processes.
5. Cellular Energy: Respiration
The energy-producing process in living things is called respiration.
Respiration is the release of energy by combining oxygen with digested food (glucose).
Carbon dioxide and water are also produced as byproducts. They are the waste products of respiration.
A simple formula to show respiration looks like this:
Glucose + oxygen carbon dioxide (waste) + water (waste) + energy
6. Stages of Cellular Respiration
Cellular respiration is the process cells use to extract the energy in organic compounds, particularly glucose.
Cellular respiration occurs in three majorstages
Stage 1:glucose is converted to pyruvateproducing a small amount of ATP and NADH
Stage 2:Aerobic respiration occurs: this is when oxygen is present, pyruvate and NADH make more ATP.
Stage 3: In an electron transfer chain, continuing reactions create a large amount of ATP from the materials from stage 2.
7. Stage 1: Breakdown of Glucose
The primary fuel for cellular respiration is glucose which is formed when carbohydrates such as starch and sucrose are broken down.
In the First stage of cellular respiration, glucose is broken down in the cytoplasm during a process called glycolysis.
Glycolysis is an enzyme-assisted anaerobic process that
breaks down one six carbon molecule of glucose
to two three-carbon pyruvate ions
1
8. Stage 1: Breakdown of Glucose: Glycolysis
Glycolysis can be summarized in 4 steps
Step 1:
in a series of three reactions,
phosphate groups from two ATP molecules
are transferred to a glucose molecule
9. Stage 1: Breakdown of Glucose: Glycolysis
Glycolysis can be summarized in 4 steps
Step 2:
In two reactions,
the resulting six-carbon molecule is broken down to
two three-carbon compounds,
each with a phosphate group
10. Stage 1: Breakdown of Glucose: Glycolysis
Glycolysis can be summarized in 4 steps
Step 3:
Two NADH molecules are produced,
and one more phosphate group is transferred
to each three-carbon compound.
11. Stage 1: Breakdown of Glucose: Glycolysis
Glycolysis can be summarized in 4 steps
Step 4:
In a series of 4 reactions,
each three carbon compound is converted to
a three-carbon pyruvate,
producing 4ATP molecules in the process
12. Stage 1: Breakdown of Glucose: Glycolysis
Summary: In this 4 step process:
Glycolysis uses two ATP molecules
but produces four ATP molecules in return.
Thus, we gain two ATP molecules for a gain ratio of 2 to 1.
Glycolysis is followed by another set of reactions that uses the energy temporarily stored in NADH to make more ATP.
13. Stage 2: Production of ATP
When oxygen is present, pyruvate produced during glycolysis enters a mitochondrion and is converted to a two-carbon compound.
This reaction produces onecarbon dioxidemolecule, one NADH molecule, and one two-carbon acetyl group
The acetyl group is attached to a molecule called coenzyme Aforming a compound called acetyl-CoA.
14. Stage 2: Production of ATP
Acetyl-CoA enters a series of enzyme-assisted reactions called the Krebs Cycle.
The Krebs Cycle has several steps we will be breaking down.
15. Stage 2: Production of ATP
Step 1:
Acetyl-CoA combines with a 4 carbon compound, forming a six carbon compound and releasing coenzymeA
16. Stage 2: Production of ATP
Step 2:
Carbon Dioxide (CO2)
is released from the six-carbon compound, forming a five-carbon compound.
Electrons are transferred to NAD+, making a molecule of NADH.
17. Stage 2: Production of ATP
Step 3:
Carbon dioxide is released from the five-carbon compound, resulting in a four-carbon compound.
A molecule of ATP is made, and a molecule of NADH is produced.
18. Stage 2: Production of ATP
Step 4:
The existing four-carbon compound is then converted to a new four-carbon compound.
Electrons are transferred to an electron acceptor called FAD, making a molecule of FADH2.
FADH2 is another type of electron carrier.
19. Stage 2: Production of ATP
After the Krebs Cycle, NADH and FADH2 now contain much of the energy that was previously stored in glucose and pyruvate.
When the Krebs Cycle is completed, the four-carbon compound that began the cycle has been recycled, and acetyl-CoA can enter the cycle again.
20. Electron Transfer Chain
In aerobic respiration, electrons donated by NADH and FADH2 pass through an electron transport chain.
Step 1: The electron transfer chain pumps hydrogen ions out of the inner compartment
21. Electron Transfer Chain
Step 2: At the end of the chain, electrons and hydrogen ions combine with oxygen, forming water (H2O).
22. Electron Transfer Chain
Step 3: ATP is produced as hydrogen ions diffuse into the inner compartment through a channel protein.
23. Electron Transfer Chain
Hydrogen ions diffuse back into the inner compartment through a carrier protein that adds a phosphate group to ADP, making ATP.
At the end of the electron chain, hydrogen ions and spent electrons combine with oxygen molecules (O2) forming water molecules (H20)
24. Respiration in the Absence of Oxygen
What happens when there is not enough oxygen for aerobic respiration to occur?
When oxygen is not present, NAD+ is recycled in another way
Under anaerobic conditions, electrons carried by NADH are transferred to pyruvate produced during glycolysis.
This process recycles NAD+ needed to continue making ATP through glycolysis.
This recycling of NAD+ using an organic hydrogen acceptor is called fermentation.
25. Respiration in the Absence of Oxygen
Two important types of fermentation are lactic acid fermentation and alcoholic fermentation.
Lactic acid fermentation by some prokaryotes and fungi is used in the production of foods such as yogurt and some cheeses.
26. Lactic Acid Fermentation
Lactate is the ion of an organic acid called lactic acid. For example, during exercise, pyruvate in muscles is converted to lactate when muscles must operate without enough oxygen.
Fermentation enables glycolysis to continue producing ATP in muscles as long as the glucose supply lasts. Blood removes excess lactate from muscles.
Lactate can build up in muscle cells if it is not removed quickly enough, sometimes causing muscle soreness.
27. Alcoholic Fermentation
Alcoholic fermentation is a two-step process.
First, pyruvate is converted to a two-carbon compound, releasing carbon dioxide.
Second, electrons are transferred from a molecule of NADH to the two-carbon compound, producing ethanol.
28. Alcoholic Fermentation
Alcoholic fermentation by yeast, a fungus, has been used in the preparation of many foods and beverages.
Wine and beer contain ethanol made during alcoholic fermentation by yeast.
Carbon dioxide released by the yeast causes the rising of bread dough and the carbonation of some alcoholic beverages, such as beer.
Ethanol is actually toxic to yeast. At a concentration of about 12%, ethanol kills yeast.
Thus, naturally fermented wine contains about 12% ethanol.
29. Production of ATP: Summary
The total amount of ATP that a cell is able to harvest from each glucose molecule that enters glycolysis depends on the presence or absence of oxygen.
Cells use energy most efficiently when oxygen is present.
In the first stage of cellular respiration, glucose is broken down to pyruvate during glycolysis. Glycolysis is an anaerobic process (no oxygen required), and it results in a gain of two ATP molecules.
In the second stage of cellular respiration, the pyruvate passes through either aerobic respiration (requires oxygen) or fermentation. When oxygen is not present, fermentation occurs instead.
30. Production of ATP: Summary
Most of a cells ATP is made during aerobic respiration. (requiring oxygen)
For each molecule of glucose that is broken down, as many as two ATP molecules are made directly during the Krebs cycle,
and up to 34 ATP molecules are produced later by the electron transport chain.
31. Key Concepts: Review. . .
Cellular respiration has two stages. First glucose is broken down to pyruvate during glycolysis, making some ATP.
The Krebs cycle is a se

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