8: Energy From Organic Molecules I Flashcards
Module 2, Lesson 2
Depending on how they obtain energy, organisms are classified as either…
Autotrophs or heterotrophs
____ convert solar energy into chemical energy.
Autotrophs
Autotrophs store chemical energy as…
ATP or organic molecules
List three examples of autotrophs.
- Plants
- Algae
- Photosynthetic bacteria
____ rely on the chemical energy stored in the bonds of organic molecules.
Heterotrophs
Heterotrophs convert chemical energy into…
ATP
True or false:
Only heterotrophs can extract chemical energy from organic molecules.
False
Both autotrophs and heterotrophs are capable of this.
____% of species are heterotrophs.
95
List four examples of heterotrophs.
- Animals
- Fungi
- Most protists
- Most prokaryotes
All cells can use ____ to extract energy from the chemical bonds in organic molecules.
Cellular respiration
Cellular respiration involves two enzyme-catalyzed reactions, ____ and ____.
Oxygenation and dehydrogenation
Dehydrogenation involves…
The loss of both protons and electrons
(the loss of one or more hydrogen atoms)
The energy contained in electrons is harvested via a series of…
Redox reactions
During a redox reaction, the ____ and ____ are transferred to another molecule.
Electrons and most of their energy
What happens to the energy lost by electrons during transfer?
It is either lost as heat or converted to ATP.
After multiple redox reactions, the energy-depleted electrons are transferred to…
A final electron acceptor molecule
The transfer of electrons often relies on…
Electron carriers
Most electron carriers are…
Cofactors
What are cofactors?
Small chemicals that assist enzymes
All electron carriers are easily and reversibly ____ and ____.
Oxidized and reduced
List two examples of electron carriers.
NAD+ (reduces to NADH)
FAD (reduces to FADH2)
What two forms of energy are generated via cellular respiration?
- ATP
- Electron energy
NAD+ has ____ energy than NADH.
Greater
____ is a fundamental energy source for cells.
Glucose
When glucose is oxidized in the process of molecular oxygen (O2), respiration becomes…
Aerobic
During the aerobic respiration of glucose, ____ is the final acceptor for harvested electrons.
Oxygen
Cellular respiration of glucose produces chemical energy as…
ATP and heat
True or false:
It is more efficient for a cell to convert the chemical energy of glucose to ATP all at once.
False
Glucose is so energy efficient that if a cell did this, it would likely combust.
Glucose oxidation happens over ____ stage(s).
Four
List the four stages of glucose oxidation.
- Glycolysis
- Pyruvate oxidation
- Krebs cycle
- Electron transport chain & chemiosmosis
In eukaryotes, glycolysis occurs in the…
Cytosol
In eukaryotes, pyruvate oxidation, the Krebs cycle, and chemiosmosis occur in the…
Mitochondria
In prokaryotes, the process of glucose oxidation occurs in either the…
Cytoplasm or plasma membrane
During glycolysis, 1 molecule of glucose is converted into….
2 molecules of pyruvate
What are the two phases of glycolysis?
- Energy input
- Energy production
During the first phase of glycolysis…
Glucose splits into 2 molecules of G3P.
The first phase of glycolysis is ____, while the second is ____.
Endergonic ; exergonic
During the second phase of glycolysis…
Each molecule of G3P is converted into a pyruvate molecule
For each glucose molecule, glycolysis produces…
2 pyruvate molecules
4 ATP molecules
2 NADH molecules
2 water molecules
Glycolysis results in a net gain of ____ ATP molecules.
Two
List the two means of producing ATP.
- Substrate-level phosphorylation
- Oxidative phosphorylation
During substrate-level phosphorylation…
An enzyme transfers an inorganic phosphate to ADP, creating ATP.
The energy contained in the inorganic phosphate is ____ during substrate-level phosphorylation.
Maintained
When ____ is present, eukaryotes and aerobic prokaryotes can synthesize much more ATP.
Oxygen
True or false:
Glycolysis requires oxygen to proceed.
False
However, the cell can perform aerobic respiration if there is oxygen present.
Pyruvate oxidation occurs in the ____ of a mitochondrion.
Matrix
(innermost area)
For every molecule of pyruvate, pyruvate oxidation produces…
1 molecule of carbon dioxide
1 molecule of NADH
1 molecule of acetyl-CoA
The Krebs cycle is also sometimes called the…
Citric acid cycle
The Krebs cycle contains a total of ____ steps, divided into ____ phases.
Nine ; three
During the Krebs cycle…
Acetyl-CoA is oxidized.
The Krebs cycle occurs in the ____ of a mitochondrion.
Matrix
List the three main steps of the Krebs cycle.
- Acetyl-CoA and oxaloacetate combine to form citrate.
- Citrate is rearranged and forms a 4-carbon succinate.
- Oxaloacetate is regenerated from succinate.
In addition to succinate, the second step of the Krebs cycle produces…
2 carbon dioxide molecules
2 NADH molecules
1 ATP molecule
In addition to oxaloacetate, the third step of the Krebs cycle produces…
1 NADH molecule
1 FADH2 molecule
In total, for each molecule of acetyl-CoA, the Krebs cycle produces…
2 molecules of carbon dioxide
3 molecules of NADH
1 molecule of FADH2
1 molecule of ATP
1 oxaloacetate
For each glucose molecule, ____ acetyl-CoA molecules enter the Krebs cycle.
Two