Anatomy & Physiology 34A Lecture
Chapters 3 & 24 – Cellular Respiration
I. Overview
A. Energy in Biological Systems
B. Chemical Reactions
C. Enzymes
D. Metabolism
E. ATP Production
F. Synthetic Pathways
II. Energy in Biological Systems
A. ____________ is the capacity to do work
B. Energy may be in the form of chemical, mechanical, or transport _________
1. ______________ work allows cells to grow, reproduce, and store energy (e.g.,
chemical bonds in molecules)
2. ______________ work is used for movement (e.g., muscle contraction)
3. ______________ work enables cells to move particles through cell membranes
C. The laws of _______________ govern the transfer of energy within a system
1. Energy can be ___________ from one form to another, but the total energy in a
closed system (i.e., the universe) does not change
2. One form of energy cannot be completely converted to another form – there is
always a loss of ________ energy
3. Natural spontaneous processes move from a state of order to disorder – this is
called ____________
4. To maintain intracellular order, cells must have a constant input of __________
III. Chemical Reactions
A. Chemical reactions allow cells to transfer the __________ energy of chemical
bonds into __________ energy for growth, maintenance, reproduction, and
movement
B. The speed of a reaction is called the ________ _____, which is its change in
concentration over time, often measured in M/sec
C. Energy transfer in reactions occurs as __________ are broken, and/or formed
1. Energy stored in the chemical bonds of a molecule, and available to do work is
called the _______ _____ of the molecule
2. Large molecules generally have more _________, thus more free __________
D. ___________ energy is the initial amount of energy needed to bring reactants into
position to _________ with each other
E. _______gonic Reactions
1. ________ start at a higher energy level than the products.
2. Often the breakdown (____________) of larger molecules (e.g., breakdown of
glycogen to glucose)
3. Reaction occurs ____________ (needs little energy input)
4. Results in the ____________ of energy.
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F. ________gonic Reactions
1. End _________ are at a higher energy level than reactants.
2. Often the build-up (__________) of larger molecules (e.g.: glycogen synthesis
from glucose).
3. Requires a greater __________ of energy for the reaction to occur.
G. ____________ Reactions
1. Energy released by ______gonic reactions is used to drive ________gonic
reactions.
2. Exergonic break down of ______ is often coupled to endergonic cell
reactions requiring ___________
IV. Enzymes
A. _____________ are protein catalysts that speed up reaction rates without
themselves being changed by the reaction
1. In enzymatic reactions, the reactants are called _________
2. Enzyme names are often formed by adding “-_____” to its substrate (e.g.:
lipase) or by the action it performs (e.g.: phosphatase)
3. Every chemical reaction in a cell requires a ___________ enzyme
4. Enzymes _________ the energy of activation so chemical reactions can take
place with less ________ in a cell
a. Enzymes bind to their substrates and bring them into the best
_____________ for reacting with each other
b. This allows enzymatic reactions to have much _______ reaction rates than
nonenzymatic reactions
5. Enzymes form an _________-_________ complex
a. A substrate attaches to a specific enzyme at its ______ _______ (Lock &
Key Model vs. Induced Fit Model).
b. Enzymes help to split substrates (_____________) or to join substrates
together (________) to form product(s).
c. ___________(s) detach from the enzyme, which returns to its original
shape, ready for another substrate.
6. The presence or absence of specific _________ determines what reactions take
place in a given cell or organelle.
B. Some enzymes require Cofactors or Coenzymes
1. Co___________ - nonprotein ____________ molecule or ion required by some
enzymes to function (e.g.: magnesium, potassium, calcium ions).
2. Co__________ - nonprotein __________ molecules that bind to enzymes and
serve as carriers for chemical groups or electrons (e.g.: NAD+, FADH, and
CoA).
3. _____________ such as niacin, riboflavin and pantothenic acid are used to
make co____________ such as NAD+, FADH, and CoA.
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C. _____________ that affect enzyme reaction rates include temperature, pH,
concentration of substrate and/or enzyme
1. Temperature
a. As ____________ increases to an optimal point, the reaction rate
___________ (in humans, optimal temp. is ______oF).
b. Beyond the optimal point, the rate levels off, then decreases sharply as
enzymes are ____________ (inactivated)
2. pH (acidity or basicity)
a. Each enzyme has an optimal ____, which helps it maintain its functional
shape.
b. Change in pH alters bonding of amino acid “R” groups and results in a
shape change (___________) that inactivates the enzyme.
3. Substrate & Active Enzyme Concentration
a. Greater ____________ concentration = more chances to bind with enzyme
active sites = ________ reaction rates.
b. Greater __________ concentration = more active sites for substrates to bind
with = _________ reaction rates.
D. Chemical Modulators alter enzyme activity
1. ____________ (regulator) - a molecule that binds to an enzyme and alters its
catalytic ability.
2. Modulators include competitive ____________, allosteric and covalent
modulators
a. Competitive inhibitor - molecule with shape similar to that of a substrate
________ for the enzyme’s active site.
b. Allosteric modulator - binds to an enzyme’s ________ site (not the active
site) and alters the active site shape, which can
1) ____________ enzyme-substrate binding OR
2) ____________ enzyme-substrate binding
c. Covalent modulator – atom or functional group (e.g.: phosphate) that
____________ binds to an enzyme and activates or deactivates it.
1) _________ enzymes and ATP phosphorylate enzymes
2) _______________ dephosphorylate enzymes
V. Metabolism
A. ____________ refers to all of the chemical reactions in an organism. Two types of
metabolism are
1. __________ – the break down of large molecules to smaller ones. Catabolic
reactions are _______gonic (they release energy)
2. ___________ – the build up of large molecules from smaller ones. Anabolic
reactions are ________gonic (they require energy input)
3. Energy released from or stored in chemical bonds is usually measured in
kilocalories (_____)
a. A kilocalorie (_______) is the amount of energy required to raise the temp. of
one liter of water by 1° Celcius.
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b. Energy released from catabolic reactions is often stored in the ______ of ATP
molecules, or in high energy ____________ in NADH and FADH2
c. Energy used for anabolic reactions is often provided by breaking the bonds of
______ molecules, or transferring electrons from ________ and FADH2
B. Metabolic ________ - organized series of chemical reactions.
1. Begins with a reactant and ends with a ____________
2. Reactants are called ____________ in enzymatic reactions
3. Involves many small ___________
4. Proceeds in an ____________ step-by-step manner.
A → B → C → D → E → F →G
E1
E2
E3 E4
E5
E6
(A-F are substrates, B-G are products, E1, E2…are enzymes)
5. One pathway may lead to other pathways if they have molecules in
____________
6. Allows for easier capture & use of ___________ because it is released in
_________ increments.
C. Cells ____________ their metabolic pathways in several ways
1. Control of ___________ concentration and activity
2. Production of allosteric and covalent ____________
3. Use of different enzymes to catalyze __________ reactions
4. Isolation of enzymes within intracellular ______________
5. Maintenance of an optimum ratio of ______ to ADP
D. ATP is the main ________ transfer molecule in metabolic reactions
1. ______ = Adenosine Triphosphate, composed of adenine, ribose sugar, and 3
phosphates connected by high energy _______
2. When energy is required, the phosphate ______ between the 2nd and 3rd
phosphate is broken, yielding ______ + Pi (inorganic phosphate)
3. If more energy is needed, the phosphate _____ between the 1st and 2nd phosphate
may be broken, yielding _______ + Pi
4. ADP and AMP can be converted back to _____ via the process of cellular
______________
E. ATP Production occurs during cellular ______________:
C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP + Heat
Enzymes
1. _____________ cellular respiration (fermentation)
a. Does not require ____________
b. Occurs in the cell ___________
c. Involves ___________, in which a 6-carbon _________ molecule is
progressively split into 2 3-carbon ________ molecules
d. The energy liberated as glucose _______ are broken is used to produce a net
of ___ ATP and 2 ______
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e. When oxygen is not present, pyruvate is converted to ________ via lactate
dehydrogenase and NADH is restored to _______
2. ___________ cellular respiration requires _________, and includes glycolysis,
the citric acid cycle, and the electron transport chain
a. ____________ occurs as in anaerobic respiration, except
1) ___________ is transported into the mitochondrion, and converted to a 2carbon _____________ molecule, with the loss of CO2
2) _________s transport their high energy ___________ to the electron
transport chain (ETC)
b. _________ _____ cycle occurs via enzymes in the mitochondrial _________
in the following sequence
1) ___________ is joined to a 4-carbon molecule to form a 6-carbon
_________ acid molecule
2) In a cycle of enzymatic reactions, citric ______ is progressively broken
back down to the ___-carbon molecule, with the loss of _____
3) Energy liberated as citric acid bonds are broken is used to generate __-ATP
molecules, ___-NADH, and ___-FADH2
c. ___________ __________ chain (ETC) involves proteins (enzymes and
cytochromes) in the mitochondrial ______
1) ______ and FADH2 transport their high energy electrons (in H atoms) to
proteins in the ETC
2) __________ are stripped from their H atoms and passed from protein to
protein along the ETC
3) Energy from the electrons allows ___ ions to be pumped from the matrix
into the _______________ space
4) At the end of the ETC, ____ ions diffuse back to the matrix through ATP
___________, providing energy to convert ADP + Pi to ______
5) H+ and their electrons are reunited at the end of the ETC to join with
oxygen and form _____
6) About ___-____ ATP are generated in the ETC via ___________
phosphorylation
F. Large ____molecules can also be used in cell respiration to regenerate ATP
1. ____________ can be broken down via glycogenolysis into ___________
molecules
2. __________ can be broken down via lipolysis into glycerol and fatty acids
a. ___________ is fed into glycolysis
b. ________ _____ are broken into 2 hydrocarbon fragments via beta-oxidation
and fed into the citric acid cycle
3. _____________ can be broken down via proteases into polypeptides, then by
peptidases into ________ _________; the glucogenic A.A.s can be used in cell
respiration
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G. Synthetic pathways
1. Glycogen is made from ________ (glycogenesis), primarily in the liver and
muscle cells
2. Glucose can be made from glycerol or glucogenic ______ ______
(gluconeogenesis) in a process similar to the reverse of glycolysis
3. Lipids are made from _____________ units linked together by fatty acid synthase
in the smooth ER
4. Protein synthesis is directed by DNA sequences called ________. We will
discuss this process in a later lecture