49 Questions
During which stage of cellular respiration is pyruvate oxidized?
Citric acid cycle
In which process are electrons transported to ATP synthesis through chemiosmosis?
Oxidative phosphorylation
Which molecule is the primary product of glycolysis?
Pyruvate
What is the main purpose of fermentation in cellular respiration?
To generate ATP without oxygen
In a redox reaction, which substance is oxidized?
The substance losing electrons
What is the role of O2 in cellular respiration?
O2 is reduced
What makes O2 a powerful oxidizing agent?
Its high electronegativity
What type of bonds in organic molecules are a source of energy?
C ¬ H bonds
What is the function of activation energy in cellular respiration?
Acts as a barrier preventing instantaneous combination of glucose with O2
What do carbohydrates and fats serve as in cellular respiration?
Reservoirs of electrons associated with hydrogen
What is the main purpose of stepwise energy harvest in cellular respiration?
Efficiently harness energy for constructive work
What is the reducing agent in a redox reaction?
Electron donor
What is the electron acceptor in a redox reaction?
Oxidizing agent
What is the role of oxygen in methane combustion?
Oxygen is oxidized
What happens in redox reactions that do not involve the complete transfer of electrons?
Change in the degree of electron sharing in covalent bonds
What is the source of energy liberated from the oxidation of glucose in respiration?
Transfer of electrons to a lower energy state
Where does glycolysis occur?
Cytosol
What is the final product of glycolysis?
Pyruvate
Where does oxidative phosphorylation occur in eukaryotic cells?
Inner membrane of the mitochondrion
What is the main function of the citric acid cycle?
Complete the breakdown of glucose to carbon dioxide
What is the role of NADH and FADH2 in cellular respiration?
Transfer electrons to the electron transport chain
Where is the energy released during cellular respiration stored?
In the form of ATP
What is the primary function of substrate-level phosphorylation?
Produce ATP directly
How is oxidative phosphorylation different from substrate-level phosphorylation?
Involves the transfer of electrons to the electron transport chain
Which stage of cellular respiration accounts for almost 90% of the ATP generated?
Oxidative phosphorylation
What is the cumulative function of the three metabolic stages of cellular respiration?
The entire process of breaking down glucose and other organic fuels, releasing energy in the form of ATP, heat, and light
What is the term usually reserved by biochemists for stages 2 and 3 of cellular respiration?
Cellular respiration
What is the source of energy harvested during cellular respiration?
Organic fuels such as glucose
Which process ultimately provides the energy stored in organic molecules of food?
Photosynthesis
What are the waste products generated by cellular respiration?
Carbon dioxide and water
Which compounds can act as fuels for exergonic reactions?
Compounds that can participate in exergonic reactions
What is the most efficient catabolic pathway that requires oxygen as a reactant?
Aerobic respiration
Which process is a partial degradation of sugars or organic fuel that occurs without the use of oxygen?
Fermentation
What is the free energy change per mole of glucose decomposed in the breakdown of glucose in cellular respiration?
$-686$ kcal
What is essential for cellular function and is generated by catabolic pathways?
ATP
What plays a major role in releasing stored energy in catabolic pathways?
Electrons
Which molecules from food can be processed and consumed as fuel for cellular respiration?
Carbohydrates, fats, and proteins
What is the process that breaks down organic fuel using oxygen and generates ATP?
Cellular respiration
What type of respiration refers to the process similar to the combustion of gasoline in an automobile engine?
Aerobic respiration
What ultimately uses the energy stored in organic molecules of food to synthesize ATP through redox reactions?
Mitochondria
What happens to NAD+ during cellular respiration?
It is reduced to NADH by receiving 2 electrons and 1 proton from the substrate.
What is the function of NADH in cellular respiration?
It represents stored energy that can be tapped to make ATP when the electrons complete their “fall” down an energy gradient from NADH to O2.
Where does the electron transport chain primarily exist in the cell?
Inner membrane of mitochondria
What is the role of O2 in cellular respiration?
It captures electrons along with hydrogen nuclei at the bottom of the electron transport chain, forming water.
What is the main function of the electron transport chain during cellular respiration?
To facilitate the transfer of electrons from NADH to O2, generating ATP.
What represents the stored energy that can be tapped to make ATP during cellular respiration?
NADH
What happens to NADH during cellular respiration?
It donates electrons to the electron transport chain, generating ATP.
Where do most electrons travel during cellular respiration?
Glucose → NADH → electron transport chain → oxygen
What is the role of dehydrogenases in cellular respiration?
To remove a pair of hydrogen atoms from the substrate, oxidizing it and forming NADH.
Study Notes
Cellular Respiration and Electron Transfer
- Glucose is broken down in a series of steps, catalyzed by enzymes, with electrons being stripped at key steps.
- Hydrogen atoms from glucose are usually passed first to an electron carrier, NAD+, which can cycle between its oxidized and reduced forms.
- Dehydrogenases remove a pair of hydrogen atoms from the substrate, oxidizing it and forming NADH.
- NAD+ is reduced to NADH by receiving 2 electrons and 1 proton from the substrate.
- NADH represents stored energy that can be tapped to make ATP when the electrons complete their “fall” down an energy gradient from NADH to O2.
- Cellular respiration brings hydrogen and oxygen together to form water through an electron transport chain, consisting of mostly proteins, built into the inner membrane of mitochondria.
- Electrons removed from glucose are shuttled by NADH to the top of the chain, and at the bottom, O2 captures these electrons along with hydrogen nuclei, forming water.
- Electron transfer from NADH to oxygen is an exergonic reaction, with electrons cascading down the chain from one carrier molecule to the next in a series of redox reactions.
- O2 pulls electrons down the chain in an energy-yielding tumble analogous to gravity pulling objects downhill.
- Most electrons travel the following “downhill” route during cellular respiration: glucose → NADH → electron transport chain → oxygen.
- The cell uses the energy released from this exergonic electron fall to regenerate its supply of ATP.
- NAD+ is the most versatile electron acceptor in cellular respiration and functions in several of the redox steps during the breakdown of glucose.
Test your knowledge of cellular respiration and electron transfer with this quiz. Explore the steps of glucose breakdown, electron transfer, and ATP production in cellular respiration.
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