50 Questions
During glycolysis, what role does glucose play in ATP production?
Glucose is split and bonds are broken to release energy captured in ATP.
What is an advantage of glycolysis in terms of energy production?
It produces ATP efficiently without high oxygen levels.
How do cells initially obtain the energy required to start glycolysis?
By hydrolyzing 2 ATP molecules from existing cellular ATP stores.
Which molecule is reduced during the NADH production phase of glycolysis?
NAD+
In glycolysis, what happens to the NADH molecules produced?
They enter the electron transport chain to help with ATP synthesis.
Which process forms the main energy currency of cells?
The electron transport chain
In which cellular structure does the Krebs cycle occur?
Mitochondria
Which stage of cellular respiration does not directly require oxygen but is essential for aerobic respiration?
The Krebs cycle
What is the primary molecule broken down in glycolysis?
Glucose
Where does anaerobic respiration occur within a cell?
Cytoplasm
Which molecule(s) are the products of cellular respiration?
Carbon dioxide and water
How are the processes of photosynthesis and cellular respiration related?
The products of photosynthesis are the reactants of cellular respiration
What is the main function of the electron transport chain in aerobic respiration?
To generate ATP
What is the primary reason organisms need oxygen according to cellular respiration?
To release energy from food during electron transport chain
Which stage of cellular respiration captures a minor amount of glucose's energy directly?
Glycolysis
What is the definition of a calorie as described in the text?
The amount of energy to raise the temperature of 1 gram of water by 1 degree Celsius
How is the energy from food molecules trapped in cells during cellular respiration?
In the form of ATP
What percentage of the energy in glucose remains after glycolysis?
90%
Which macromolecule types are used by cells for food?
Fats, proteins, and carbohydrates
Which statement correctly represents the cellular respiration equation?
$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + chemical , energy , in , food , (in , ATP)$
Which stage of cellular respiration relies on the reactants from the other stages?
Electron transport chain
What is the primary way to continue generating ATP for exercises lasting longer than 90 seconds?
Cellular respiration
Why are aerobic forms of exercise beneficial for weight control?
They promote the breakdown of stored fats for energy
How long can carbohydrate glycogen stores in muscle cells and other tissues usually last during activity?
15-20 minutes
What do athletes in long-distance events rely on to supply oxygen to their muscles?
Efficiency of their respiratory and circulatory systems
What happens when the glycogen stores are depleted after 15-20 minutes of activity?
The body starts breaking down other stored molecules, including fats, for energy
What is the final electron acceptor of the electron transport chain?
Oxygen
What process is used by the cell to synthesize ATP?
Chemiosmosis
What happens every time 2 high energy electrons pass down the chain?
Hydrogen ions are transported across the membrane
Which enzyme is involved in the formation of ATP in the inner mitochondrial membrane?
ATP synthase
How many molecules of ATP does glycolysis net per molecule of glucose?
2
How many ATP molecules are produced per molecule of glucose through glycolysis, Krebs cycle, and the electron transport chain?
36
How does fermentation keep glycolysis going in the absence of oxygen?
By converting NADH to NAD+
Where does fermentation occur in the cell?
Cytoplasm
What is the end product of lactic acid fermentation?
lactic acid
Which of the following is true about alcoholic fermentation?
It is carried out by yeast and produces ethyl alcohol and CO2.
Which cells are best adapted to produce ATP by lactic acid fermentation during rapid bursts of activity?
muscle cells
Why do swimmers breathe heavily after a race?
To repay the 'oxygen debt' built up during lactic acid fermentation
Which pathway is NOT involved in the quick generation of ATP during high-speed exercise?
Krebs cycle
What accumulates in muscles as a byproduct of lactic acid fermentation during intense exercise?
lactic acid
Which process does NOT produce carbon dioxide?
lactic acid fermentation
What happens to NADH during both types of fermentation?
It is oxidized to NAD+.
What is the end product when a carbon atom is split off from pyruvic acid?
Carbon dioxide
During the Krebs cycle, which molecule combines with acetyl-CoA to form citric acid?
A four-carbon molecule
What is produced with every turn of the Krebs cycle concerning ATP?
1 molecule of ATP
How many molecules of ATP are produced from a single molecule of glucose during the Krebs cycle?
2 ATP molecules
What do electron carriers convert NAD+ and FAD into during the Krebs cycle?
NADH and FADH2
What is the fate of carbon dioxide produced during the Krebs cycle?
It diffuses out of the mitochondria and cell into the bloodstream and then exhaled
In eukaryotes, where is the electron transport chain located?
Inner membrane of the mitochondrion
Which molecules pass their high-energy electrons to the electron transport chain?
NADH and FADH2
Study Notes
Cellular Respiration: Overview
- Organisms get energy from food, which is stored in units of calories (1 calorie = amount of energy needed to raise 1 gram of water 1°C)
- Cells use different molecules for food, such as fats, proteins, and carbs, with varying energy storage
- Cellular respiration is the process of energy conversion that releases energy from food in the presence of oxygen
- The overall equation for cellular respiration is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + chemical energy in food (ATP)
- The cell reduces the chemical energy in food molecules a little at a time, trapping the energy in the form of ATP
Stages of Cellular Respiration
- There are three main stages of cellular respiration: glycolysis, Krebs cycle, and electron transport chain
- Glycolysis: 10% of glucose energy is captured to produce ATP, leaving 90% of chemical energy still available
- Krebs cycle: More energy is captured, with reactants from other stages of the process
- Electron transport chain: Extracts energy from reactants using oxygen, requiring reactants from other stages of the process
Oxygen and Energy
- Oxygen is required at the end of the electron transport chain
- When cell demand for energy increases, oxygen use also increases
- Most energy-releasing pathways within cells require oxygen, which is why we need to breathe oxygen
Aerobic Respiration
- Aerobic respiration is a process that requires oxygen
- It occurs in two stages: the Krebs cycle and the electron transport chain
- The Krebs cycle is a series of chemical reactions that occur in the mitochondria of cells, requiring an electron transport chain to function
- The electron transport chain is a series of molecules that use electrons from the Krebs cycle to generate ATP, requiring oxygen
Anaerobic Respiration
- Anaerobic respiration is a process that does not require oxygen
- It occurs in the cytoplasm of cells
- The most common type of anaerobic respiration is glycolysis
- Glycolysis breaks down glucose into two molecules of pyruvate, not requiring oxygen
The Relationship between Photosynthesis and Cellular Respiration
- Photosynthesis and cellular respiration are two complementary processes
- Photosynthesis produces glucose and oxygen, while cellular respiration uses glucose and oxygen to produce carbon dioxide, water, and ATP
- The products of photosynthesis are the reactants of cellular respiration, and vice versa
Glycolysis
- Glycolysis breaks down glucose into two molecules of pyruvate, releasing a small amount of energy
- The energy from glycolysis is used to produce ATP and NADH
The Krebs Cycle
- The Krebs cycle is a series of chemical reactions that occur in the mitochondria of cells
- It begins with the breakdown of acetyl-CoA, producing citric acid
- The cycle releases energy, producing ATP, NADH, and FADH₂
- The energy from the Krebs cycle is used to produce ATP in the electron transport chain
Electron Transport and ATP Synthesis
- The electron transport chain uses high-energy electrons from the Krebs cycle to synthesize ATP from ADP
- The electron transport chain is a series of electron carriers located in the inner membrane of the mitochondria
- High-energy electrons are passed from carrier to carrier, releasing energy used to produce ATP
ATP Production
- The cell uses chemiosmosis to produce ATP
- The inner mitochondrial membrane contains enzymes called ATP synthases
- The charge difference across the membrane forces hydrogen ions through channels in these enzymes, producing ATP
- On average, each pair of high-energy electrons that moves down the full length of the chain provides enough energy to produce 3 molecules of ATP
Fermentation
- Fermentation is an anaerobic process that occurs in the absence of oxygen
- It releases energy from food molecules by producing ATP
- There are two types of fermentation: alcoholic and lactic acid
Alcoholic Fermentation
- Carried out by yeast, producing ethyl alcohol and carbon dioxide
- Pyruvic acid + NADH → alcohol + CO₂ + NAD+
Lactic Acid Fermentation
- Chemical reaction that converts pyruvic acid to lactic acid
- Does not give off CO₂
- Regenerates NAD+ so that glycolysis can continue
- Pyruvic acid + NADH → lactic acid + NAD+
- Humans are also lactic acid fermenters, particularly during brief periods without enough oxygen
Energy and Exercise
- During short, intense bursts of energy, the body uses ATP already in muscles and ATP made by lactic acid fermentation
- For longer periods of exercise, cellular respiration is the only way to continue generating a supply of ATP
- Aerobic forms of exercise are beneficial for weight control because they increase the efficiency of the respiratory and circulatory systems to supply oxygen to muscles for aerobic respiration
Learn about cellular respiration, the process of generating energy from food, including the importance of calories and different macromolecules in cells.
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