Download Chapter 6 – How Cells Harvest Chemical Energy Standard 1.g

Chapter 6 – How Cells Harvest Chemical Energy
Standard 1.g.
Cellular Respiration
Is the main way that chemical energy is harvested from food and converted to ATP
Is an aerobic process –
Yields
The Relationship between Cellular Respiration and Breathing
Cellular respiration and breathing are closely related.
Cellular respiration requires a cell to
Breathing exchanges these gases between the blood and outside air.
Cellular respiration banks energy in ATP molecules
Cellular respiration breaks down glucose molecules and stores the released energy in ATP
The process uses O2 and releases CO2 and H2O
During cellular respiration
Organic compounds such as glucose are
The chemical energy which is released is stored
The efficiency of cellular respiration – a typical cell stores around 40% of the chemical energy
released in ATP, the rest is released as heat
ATP is produced in 2 ways
1. The movement of electrons along an electron transport chain creates a proton gradient
across the inner membrane.
The protons diffuse back across the membrane through ATP synthase releasing energy
that is used to make ATP by
2. ATP can also be made by transferring phosphate groups from organic molecules to ADP.
This process is called
The Metabolic Pathway of Cellular Respiration
Cellular respiration is an example of a metabolic pathway,
All of the reactions involved in cellular respiration can be grouped into three main stages:
• Glycolysis
•
• Electron transport
Glycolysis harvests chemical energy
The purpose of glycolysis is to split/breakdown glucose into two 3 carbon compounds (pyruvic
acid)
During the 9 chemical steps in glycolysis:
–
–
2 molecules of ATP are used
–
4 molecules of ATP are produced by
–
2 molecules of NAD+ gain electrons to form the electron carrier NADH
The net gain of ATP during glycolysis is
Glycolysis Review
1. What is the general equation for cellular respiration?
2. What is the purpose of glycolysis?
3. Where does glycolysis occur?
4. What is needed for glycolysis?
5. What process produces ATP during glycolysis?
6. How is NADH produced during glycolysis?
7. How many ATP are produced during glycolysis?
8. What is the net gain of ATP during glycolysis?
9. Why is the number produced and the net gain different?
Fermentation
Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small
amounts of ATP
After functioning anaerobically for about 15 seconds, muscle cells will begin to generate ATP by
the process of fermentation.
Fermentation relies on
But a cell must have a way of
In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol
In lactic acid fermentation, pyruvic acid is converted to lactic acid
Accumulation of lactic acid in muscles causes fatigue and soreness.
The lactic acid is transported to the liver where it is converted to pyruvic acid.
Fermentation Review
1. How many ATP are produced during the fermentation step(s)?
2. What is the purpose of fermentation?
3. What is produced during alcoholic fermentation?
4. What is produced during lactic acid fermentation?
Structure of the Mitochondria
Pyruvic acid is chemically groomed for the Krebs cycle
In the matrix each pyruvic acid molecule is broken down to form CO2 and a two-carbon acetyl
group, which enters the Krebs cycle
For each glucose molecule
The Krebs Cycle
The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each
acetyl group
The purpose of the Krebs cycle is to
Occurs in the
Each step is catalyzed by enzymes in the matrix of the mitochondria
Acetyl CoA is completely broken apart
Since 2 molecules of acetyl CoA enter the Krebs cycle for each glucose molecule, the Krebs cycle
produces
Krebs Cycle Review
1. Where does the Krebs cycle occur? (Be specific)
2. What is the purpose of the Krebs cycle?
3. What is produced during the conversion step for each glucose?
4. How many ATP are produced during the Krebs cycle for 1 glucose molecule?
5. What process produces the ATP?
6. How many NADH and FADH2 are produced during the Krebs cycle for each glucose molecule?
7. How many CO2 are produced during the Krebs cycle for each glucose molecule?
Chemiosmosis in the Mitochondrion
Electron Transport Chain
Consists of ordered groups of molecules embedded in the inner membrane of the mitochondria
Electrons are transferred from NADH and FADH2 along the electron transport chain until the
reach
The O2 gains the electrons and joins with the 2 H+ in the surrounding fluid to produce
Chemiosmosis produces ATP
The movement of electrons along the electron transport chain creates a proton gradient across
The H+ ions diffuse back through the inner membrane through ATP synthase, which captures the
energy to make ATP
Chemiosmosis produces around
Summary of Cellular Respiration
A maximum of 38 ATP are produced during cellular respiration
ETC and Chemiosmosis Review
1. What is the role of NADH and FADH2?
2. Where does the electron transport chain and chemiosmosis occur?
3. How many ATP are made during this stage?
4. What process produces the ATP?
5. A maximum of 38 ATP are produced during cellular respiration – where are they produced,
how many are made, and what process produces them
The Versatility of Cellular Respiration
Cellular respiration can “burn” other kinds of molecules besides glucose: