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Chapter 4B: How Cells Obtain Energy
4.2 Glycolysis
Where does energy to power endergonic reactions come from?
This ____________ can be thought of as the primary ____________ ____________ of cells in the same way that
____________ is the currency that people ____________ for things they need. ____________ is used to ____________
the majority of ____________ -requiring cellular ____________.
ATP in Living Systems
How many phosphate groups are in ATP?
Energy is usually released by ATP when what is removed?
Label the ATP molecule
Click and drag the triangle to go around ribose
Click and drag the square to go around the gamma phosphate group
Click and drag the circle to go around adenine
Matching
_____ ATP
A.
Transfer of a phosphate group to another molecule
_____ ADP
B.
Used for energy requiring cell functions
_____ Phosphorylation
C.
Functional group containing phosphorous and oxygen
_____ Phosphate group
D.
Lower energy molecule
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Glycolysis
What is glycolysis?
Glycolysis begins with the ______________ -carbon, ring-shaped structure of a single ______________ molecule
and ______________ with two molecules of a three-carbon sugar called ______________. Glycolysis consists of
______________ distinct ______________. In the ______________ part of the glycolysis pathway, ______________ is
used to make ______________ so that the six-carbon sugar molecule can be ______________ evenly into two threecarbon ______________ molecules. In the ______________ part of glycolysis, ______________ and nicotinamideadenine dinucleotide (______________) are produced.
Where in the cell does glycolysis take place?
Label the diagram by clicking and dragging the labels into the correct places.
Glucose
2 ATP
2 ATP
2 ATP
2 ADP
2 ADP
2 ADP
Pyruvate
2
Pyruvate
NAD+
NAD+
NADH
NADH
4.3 The Citric Acid Cycle and Oxidative Phosphorylation
The Citric Acid Cycle
What end product of glycolysis is transported into the mitochondria?
What is required for aerobic respiration to go forward?
Pyruvate is transformed into what molecule? What is removed in this reaction?
Coenzyme A is a ____________ compound. It is made from ____________.
Where in the cell does the citric acid cycle (also called the Kreb’s cycle) take place?
How does the citric acid cycle close the loop for its reactions?
During the eight steps of the cycles, what is produced?
Which two important coenzymes are used to transfer electrons from the citric acid cycle to the next pathway?
How many turns of the cycle does it take to process the equivalent of one glucose molecule?
Match the following
_____ pyruvate
A. Occurs in the mitochondria
_____ coenzyme A
B. The beginning reactant for the second stage of aerobic respiration
_____ acetyl-CoA
C. Coenzymes carrying electrons and hydrogen released by the
reactions of the second stage
_____ NADH and FADH2
D. Carries two carbon atoms into the citric acid cycle
_____ Citric acid or Krebs cycle
E. Binds to pyruvate as a CO2 molecule is released
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Oxidative Phosphorylation
Oxidative phosphorylation is made up
of two steps: the electron transport
chain and chemiosmosis. All of the
NADH and FADH2 that were produced
during glycolysis and the citric acid
cycle (Kreb’s cycle) are used to make
ATP. Protein complexes embedded in
the inner mitochondrial membrane
are used for this process.
Read through the section in the
textbook referring to figure 4.15 as the
processes are described. Then study
the following diagram and answer the
questions based on the information in
the diagram and text book.
Electron Transport Chain
NADH and FADH2 carry high energy electrons to the electron transport chain where they are donated and used to make
ATP during aerobic respiration.
In the diagram, what is used to represent the high energy electrons?
When NADH donates electrons, what products are formed (follow the curved arrow from NADH)?
As the high energy electrons leave NADH they enter the electron transfer chain. Follow the electrons along the grey
arrow to see the route the electrons take.
How many molecules/complexes make up the electron transfer chain?
The molecules are numbered in the text book figure 4.15.
Which molecule accepts electrons from NADH?
Which molecule accepts electrons from FADH2?
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How many molecules span the entire membrane (referred to as “embedded protein channels” in the diagram)?
High potential energy electrons provide the energy necessary to pump hydrogen ions across the inner mitochondrial
membrane.
H+ moves from which region to which region on the diagram (see the labels on the right side for the names of
the regions)
What is the name of the region where the highest concentration of hydrogen ion (H+) is located?
Energy is required to move the hydrogen ions across the membrane in the direction indicated in the diagram.
Why is energy required? (Remember membrane transport and concentration gradients from chapter 3)
What molecule is the final electron acceptor after the electron has moved through the electron transport chain?
What compound is formed as a final product of the electron transport chain?
Is any ATP produced in the electron transport chain?
Is any ATP used in the electron transport chain?
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Chemiosmosis
Once a concentration gradient of
hydrogen ions has formed, the
process of chemiosmosis occurs.
How do the hydrogen ions move
through the membrane?
Would energy be required for the
hydrogen ions to move in the
direction shown in the figure? Explain
your reasoning.
What is the name of the embedded
protein that provides a channel for
the hydrogen ions to pass through the membrane? (It is labeled in the diagram)
The flow of hydrogen ions through the protein channel provides free energy to do work.
Besides allowing hydrogen ions to pass through the membrane what other function does ATP Synthase have?
Which direction is the reaction going:
ATP  ADP + Pi
ADP + Pi  ATP
or
Which molecule is higher energy ATP or ADP?
Does it require energy for this reaction?
What provides the free energy to do the work required?
In the electron _________________ chain, the free _________________ from the series of _________________ just
described is used to _________________ hydrogen ions across the _________________. The uneven distribution of H+
ions across the membrane _________________ an electrochemical _________________, owing to the H+ ions’ positive
charge and their higher _________________ on one side of the membrane.
Hydrogen ions _________________ through the inner membrane through an integral membrane _________________
called ATP Synthase. This complex protein acts as a tiny _________________, turned by the force of the
_________________ ions diffusing through it, down their _________________ gradient from the _________________
space, where there are _________________ mutually repelling hydrogen ions to the matrix, where there are
_________________. The turning of the parts of this molecular machine _________________ ATP from ADP. This flow
of _________________ ions across the _________________ through ATP synthase is called _________________.
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ATP Yield
Fill in the table. Some of the information has been filled in as an example.
How many ATP formed
How many NADH/FADH2
reduced
Glycolysis
Krebs cycle
List other end products
(besides ATP and NADH)
Pyruvate
1 per cycle
2 per one molecule of
glucose
zero
Electron transfer
phosphorylation
4.4 Fermentation
In the absence of O2 aerobic respiration cannot occur. If _______________ respiration does not occur, _____________
must be reoxidized to NAD+ for reuse as an _______________ carrier for _______________ to continue. How is this
done? Some living systems use and _______________ molecules as the _______________ _______________
_______________. Processes that use an organic molecule to _______________ NAD+ from NADH are collectively
referred to as _______________. In contrast, some living systems use an _______________ molecule as a
_______________ electron acceptor; both methods are a type of _______________ cellular respiration. Anaerobic
respiration _______________ organisms to convert _______________ for their use in the _______________ of oxygen.
Choose from the following
A. Alcohol fermentation
B. Lactic Acid fermentation
C. Both types of fermentation
______ Glycolysis is the first stage
______ Yeasts are famous for their use of this pathway
______ Animals use this for a quick fix of energy for their muscles
______ Pyruvate and NADH form, and the net energy yield is two ATP
______ The final steps regenerate NAD+, the coenzyme that assists the breakdown reactions
______ Each pyruvate molecule that formed in glycolysis is converted to the intermediate acetaldehyde
______ These reactions do not completely degrade glucose to CO2 and H2O
______ Saccharomyces cerevisiae (bread yeast) makes bread dough rise
______ Drunken birds such as tipsy wild turkeys and robins consume fermented fruit or grain
______ Lactobacillus of yogurt and some other bacteria use this anaerobic pathway
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4.5 Connections to Other Metabolic Pathways
Briefly describe how other sugars are connected to glucose metabolism
Briefly describe how proteins are connected to glucose metabolism.
Briefly describe how lipids are connected to glucose metabolism.
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