Chapter 4.4 Flashcards
Cellular respiration occurs in three series of reactions called
Glycolysis
Citric Acid Cycle
Electron Transport Chain
Cellular respiration requires
glucose and oxygen
Products of cellular respirationa make
CO2, water, and energy
Glycolysis means
the breaking of glucose
Glycolysis is a
series of ten enzyme-catalyzed reactions that break down the 6-carbon glucose molecule into two 3-carbon pyruvic acid molecules
Glycolysis takes place in
the cytosol
Glycolysis involves how many sets of reactions?
Three
First Step of Glycolysis
Two phosphate groups are added to a glucose molecule, one at each end, in a step called phosphorylation.
How much energy does the first step of glycolysis require?
requires energy from two atps, which are used to “prime” the glucose so that it is activated fro some of the energy-releasing reactions that will happen
Second Step of Glycolysis
The 6-carbon glucose molecule is cleaved into two 3-carbon molecules
Third Step of Glycolysis
The electron carrier NADH is produced, ATP is synthesized, and two 3-carbon pyruvic acid molecules result
During glycolysis, how many ATPs are synthesized directly?
Four
Subtracting the two ATPS used in the priming step gives
a net yield of two ATP’s per molecules of glucose from glycolysis
For cellular respiration to continue..
NADH + H+ must be able to deliver electrons to the ETC, replenishing the cellular supply of NAD+
What acts as the final electron acceptor at the end of the ETC?
Oxygen, which enables the chain to continue processing electrons and recycling NAD+
Under anaerobic conditions, the ETC has
no oxygen and therefore nowhere to unload its electrons. As a result, the ETC can no longer accept new electrons from NADH
Anaerobic - As an alternative, NADH + H+ can
give its electrons and hydrogen back to pyruvic acid in a reaction that forms lactic acid
The buildup of lactic acid evantually
inhibits glycolysis and ATP production declines
Pyruvic acid generated by glycolysis can
continue through the aerobic pathways if enough oxygen is available
The reactions inside aerobic reactions include
the synthesis of
Acetyl Coenzyme A/Acetyl CoA
the Citric Acid Cycle
ETC
How many ATP produced per Glucose molecule in aerobic reactions?
Twenty-Eight ATP molecules per glucose
The aerobic reaction begins with
pyruvic acid produced in glycolysis moving from the cytosol into the mitochondria.
From each pyruvic acid,
enzymes inside the mitochondria remove two hydrogen atoms, a carbon atom, and two oxygen atoms, generating NADH and CO2 leacing a 2-carbon acetic acid
Aerobic Reaction - The Acetic Acid then
combines with a molecule of coenzyme A to form Acetyl Co1.
CoA “carries”
the acetic acid into the citric acid cycle
Citric Acid Cycle begins when
2-carbon acetyl CoA molecule combines with a 4-carbon oxaloacetic acid molecule to form the 6-carbon citric acid and CoA.
The citric acid is changed through
a series of reactions back into oxaloacetic acid.
Citric Acid Cycle - The cycle repeats as
long as the mitochondrion receives oxygen and pyruvic acid.
The citric acid cycle has how many important consequences?
Three
First Important Consequence in Citric Acid Cycle
One ATP is produced directly from each citric acid molecule that goes through the cycle
Second Important Consequence in Citric Acid Cycle
For each citric acid molecule, eight hydrogen atoms with high-energy electrons are transferred to the hydrogen carriers NAD+ and the related molecule FAD
Third Important Consequence in Citric Acid cycle
As the 6-carbon citric acid reacts to form the 4- carbon oxaloacetic acid, two carbon dioxide molecules are produced
What are Oxidation/Reduction Reactions?
That energy is transferred to ATP synthase, an enzyme complex that uses the energy to add a phosphate to ADP to form ATP
What two processes do not use oxygen directly?
Neither glycolysis nor the citric acid cycle
The final enzyme of the ETC gives up
a pair of electrons that combine with two hydrogen ions and an atom ox oxygen to form a water molecule
ETC - Oxygen is therefore the
final electron “carrier”
ETC - In the absence of oxygen,
electrons cannot continue to pass through the ETC and the aerobic reactions of cellular respiration stop
Excess glucose in cells may
enter anabolic carbohydrate pathways and be linked into storage forms as glycogens
Following a meal when glucose concentration is relatively high,
liver cells obtain glucose from the blood and synthesize glycogen. Between meals, when blood glucose concentration is lower, the reaction reverses and glucose is released into the blood
GLucose can react to form
lipid molecules, which are deposited in adipose tissue.
The most common entry point for aerobic respiration is
into the citric acid cycle as acetyl CoA.
