Glycolysis, Respiration, ATP Flashcards
Energy Carries Molecules
Adenosine triphosphate (ATP)
Cells break down glucose in two stages: glycolysis, which liberates a small quantity of ATP, followed by cellular respiration, which produces far more ATP.
What is Oxidation?
A loss on an electron.
What is Reduction?
A gain of an electron.
Does a molecule release energy as it is oxidized?
A molecule usually releases energy as it is oxidized.
Glucose oxidation equation
Glucose + Oxygen —-> Carbon dioxide + Water + Energy
In living systems, the oxidation of glucose takes place in two major stages. What are they?
First is known as glycolysis. The second is respiration, which in turn consists of two stages: Krebs cycle and terminal electron transport.
Glycolysis occurs in the cytoplasm of the cell, and the two stages of respiration take place within the mitochondrion.
Where glycolysis and respiration occur?
Glycolysis occurs in the cytoplasm of the cell, and the two stages of respiration take place within the mitochondrion.
Glycolysis - the lysis (splitting) of the cell takes place in series of reactions. How many?
It takes places in a series of nine reactions, each catalyzed by a specific enzyme.
Glucose
Glucose is a key energy-storage molecule
All cells metabolize glucose for energy
In humans, energy is stored as long chains of glucose, called glycogen, or as fat
These storage molecules are converted to glucose to produce ATP for energy harvesting
Glucose Breakdown Overview Stage 1
Glycolysis
1) Begins by splitting glucose (a six-carbon sugar) into two molecules of pyruvate (a three-carbon sugar)
2) Two ATP molecules are produced in glycolysis
Glycolysis proceeds in the same way under aerobic (with oxygen) or anaerobic (without oxygen) conditions
Glycolysis occurs in the cytoplasm.
Glucose Breakdown Overview Stage 2
Cellular respiration (occurs when oxygen is available)
1) Two pyruvate molecules produced by glycolysis are broken down into six carbon dioxide molecules and six water molecules
For every two pyruvate molecules, an additional 34 or 36 ATP molecules are generated
Cellular respiration occurs in mitochondria, organelles specialized for the aerobic breakdown of pyruvate.
Glucose breakdown without oxygen
If oxygen is not available, the second stage of glucose breakdown is fermentation
Fermentation does not produce any ATP
In fermentation, pyruvate remains in the cytoplasm and is converted into lactate or ethanol + CO2.
What Happens During Cellular Respiration?
Two pyruvate molecules enter the mitochondrion
Each reacts with coenzyme A (CoA), a process that captures high-energy electrons in two NADH, produces two molecules of acetyl CoA, and liberates two molecules of CO2
The acetyl CoA enters the Krebs cycle
The Krebs cycle releases four molecules of CO2, produces two ATP, and captures high-energy electrons in six NADH and two FADH2
These electrons are passed to the ETC, where their energy is used during chemiosmosis to generate a gradient of H+, yielding a net of 32 or 34 ATP
Energy-depleted electrons exiting the ETC are picked up by H+ released from NADH and FADH2, and combine with oxygen to form water.
Final Product of Cellular Respiration
The total energy captured from the breakdown of a single glucose molecule from glycolysis and cellular respiration is 36 or 38 ATP
The reason two different numbers exist for ATP synthesis is that some cell types have to expend two ATPs to transport the two NADH molecules created during glycolysis into the mitochondrion; others are more efficient and don’t require two.
Fermentation
Some cells ferment pyruvate to form lactate
Muscles that are working hard enough to use up all the available oxygen ferment pyruvate to lactate
To regenerate NAD+, muscle cells ferment pyruvate to lactate, using electrons from NADH and hydrogen ions.
