1.
2.
CELLULAR RESPIRATION
LIFE IS WORK
A. How do cells harvest the chemical energy stored in organic molecules to generate
energy?
B. The most prevalent and efficient catabolic pathway is CELLULAR RESPIRATION.
C. SIMILAR IN PRINCIPLE TO COMBUSTION OF GASOLINE IN AUTOMOBILE ENGINE
AFTER OXYGEN IS MIXED WITH FUEL:
D. Food is the fuel for respiration
E. Exhaust is carbon dioxide and water
F. Organic Compounds + Oxygen  CO2 + H20 + Energy
3.
HARVESTING ENERGY
A. CARBOHYDRATES, FATS AND PROTEINS CAN ALL BE PROCESSED AND
CONSUMED AS FUEL.
B. IT IS TRADITIONAL TO LEARN THE STEPS OF CELLULAR RESPIRATION BY
TRACKING THE DEGRADATION OF THE SUGAR GLUCOSE.
i. C6H12O6 + 6 O2  6 CO2 + 6 H2O + Energy
ii. Energy = ATP and heat
4.
HARVESTING ENERGY
A. Many good reasons to focus on the METABOLIZING of GLUCOSE though cells can
metabolize a variety of organic molecules.
i. Virtually all cells do it some of the time.
ii. Nerve cells in brain use it almost exclusively as energy source.
iii. Not as complex as other mechanisms of metabolism.
iv. Most organic molecule energy sources convert first to glucose.
5.
CELLS AND CHEMICAL ENERGY DEFINITIONSMETABOLIZING GLUCOSE
A. FERMENTATION: Anaerobic reactions that convert the pyruvic acid produced by
glycolysis into lactic acid or alcohol and CO2.
B. Breaking down carbohydrates in pathways that do not use oxygen.
C. Bubbling mud pit at Yellowstone National Park housing anaerobic archaeans.
6.
CATABOLIC PATHWAYS AND PRODUCTION OF ATP
A. FERMENTATION: A catabolic process that makes a limited amount of ATP from
glucose without an electron transport chain and that produces a characteristic end
product, such as ethyl alcohol or lactic acid.
7.
ENERGY FLOW AND CHEMICAL RECYCLING
A. Technically, the term cellular respiration refers to both the anaerobic and aerobic
processes.
B. Catabolic pathways do not directly pump solutes across membranes or perform other
cellular work – it is linked like a chemical “drive shaft” – to ATP.
C. How does a cell regenerate ATP? How does food possess energy?
8.
CATABOLIC PATHWAYS AND THE PRODUCTION OF ATP
A. AEROBIC RESPIRATION: A catabolic pathway for organic molecules, using oxygen as
the final electron acceptor in an electron transport chain and ultimately producing ATP.
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This is the most efficient catabolic pathway and is carried out in most eukaryotic cells
and many prokaryotic organisms.
B. ANAEROBIC RESPIRATION: a catabolic pathway in which inorganic molecules
OTHER THAN OXYGEN accept electrons at the down-hill end of electron transport
chains.
9.
CATABOLIC PATHWAYS AND THE OXIDATION OF ORGANIC FUELS
A. CELLULAR RESPIRATION: The catabolic pathways of aerobic and anaerobic
respiration, which break down organic molecules for the production of ATP.
10.
OXIDATION AND REDUCTION
A. REDOX REACTIONS: a chemical reaction involving the complete or partial transfer of
one or more electrons from one reactant to another; short for oxidation-reduction
reaction.
11.
NAD+ AS AN ELECTRON SHUTTLE
A. NAD+: nicotinamide adenine dinucleotide, a coenzyme that cycles easily between
oxidized (NAD+) and reduced (NADH) states, thus acting as an electron carrier.
12.
ELECTRON TRANSPORT CHAIN
A. ELECTRON TRANSPORT CHAIN: A sequence of electron carrier molecules
(membrane proteins) that shuttle electrons down a series of redox reactions that release
energy used to make ATP.
13.
WHERE ARE WE? (In a cell)
14.
WHERE ARE WE? (In a mitochondrion)
15.
ENERGY HARVESTING BEGINS WITH GLYCOLYSIS
A. GLYCOLYSIS: a series of reactions that ultimately splits glucose into pyruvate.
Glycolysis occurs in almost all living cells, serving as the starting point for fermentation
or cellular respiration.
16.
ALCOHOL FERMENTATION Occurs where there is no oxygen.
A. A method to harvest chemical energy WITHOUT oxygen or an electron transport chain.
B. Regeneration of NAD+ allows the ongoing oxidation (accepts electrons) of glucose.
C. NAD+ is regenerated when NADH transfers electrons to acetaldehyde to produce
ethanol.
17.
LACTIC ACID FERMENTATION - REGENERATION OF NAD+
A. In human cells, pyruvate becomes the oxidizing agent, accepts electrons from NADH
and produces lactate (ionized form of lactic acid).
B. NADH production is not used for energy capture, but a way to get rid of electrons and
KEEP GLYCOLYSIS GOING.
18.
PYRUVATE OXIDATION (Acetyl CoA Formation) AND CITRIC ACID CYCLE (Krebs
Cycle).
A. Acetyl CoA Formation: Acetyl Coenzyme A is the entry compound for the citric acid
cycle in cellular respiration, formed from a fragment of pyruvate attached to a
coenzyme.
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B. KREBS CYCLE (Citric Acid Cycle): A chemical cycle involving eight steps that
completes the metabolic breakdown of glucose molecules begun in glycolysis by
oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the
mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; the second major
stage in cellular respiration.
19.
OXIDATIVE PHOSPHORYLATION: Electron Transport & Chemiosmosis
A. Oxidative Phosphorylation: the production of ATP using energy derived from the redox
reactions of an electron transport chain; the third major stage of cellular respiration.
B. Electron Transport: previously defined.
C. CHEMIOSMOSIS: An energy-coupling mechanism that uses energy stored in the form
of a hydrogen ion gradient across a membrane to drive cellular work, such as the
synthesis of ATP. Most ATP synthesis in cells occurs by chemiosmosis.
20.
SUBSTRATE LEVEL PHOSPHORYLATION
A. SUBSTRATE-LEVEL PHOSPHORYLATION: the formation of ATP by an enzyme
directly transferring a phosphate group to ADP from an intermediate substrate in
catabolism.
21.
22.
OVERVIEW
GLYCOLYSIS
A. GLYCOLYSIS: the splitting of glucose into pyruvate. Glycolysis occurs in almost all
living cells, serving as the starting point for fermentation or cellular respiration.
B. O2 not necessary, CO2 not released .
C. Two stages: Energy investment and energy payoff.
23.
Glycolysis Energy Investment
24.
Glycolysis: Energy Payoff
25.
GLYCOLYSIS SUMMARY
A. Occurs in cytosol of cell.
B. Invests 2 ATP’s to produce 4 ATP’s – a 2 ATP net gain.
C. ATP’s are produced by substrate level phosphorylation.
D. GOAL OF GLYCOLYSIS? Glucose broken down and glycolysis is a source of ATP and
NADH.
26.
ACETYL CoA FORMATION
A. Glycolysis releases LESS THAN a quarter of the chemical energy stored in glucose.
B. Energy can be found in PYRUVATE.
C. Acetyl CoA formation occurs in the mitochondrion of eukaryotic cells, in the cytosol of
prokaryotic cells.
27.
KREBS CYCLE
(CITRIC ACID CYCLE)
A. What will be accomplished here? Answer: the decomposition of citrate back to
oxaloacetate, making this process a cycle.
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B. And…WE PRODUCED NADH AND FADH2 TO SUPPLY THE ENERGY NECESSARY
TO MAKE ATP.
28.
WHAT HAPPENS IN THE KREBS CYCLE?????
A. Acetyl CoA says:
B. “Oh! Can I αlways-keep studying some fun metabolics?”
C. Oh: oxaloacetate combines with acetyl CoA
D. Can: citrate
E. I: isocitrate
F. αlways-keep: α-ketoglutarate
G. Studying: succinyl CoA
H. Some: succinate
I. Fun: fumarate
J. Metabolics: malate
K. Returns to Oh! at start of cycle with oxaloacetate.
29.
Krebs Cycle (Citric Acid Cycle)
30.
ELECTRON TRANSPORT CHAIN
A. ELECTRON TRANSPORT CHAIN (ETC)
B. In eukaryotes: molecules embedded in the inner membrane of the mitochondrion.
C. In prokaryotes: molecules are embedded in the plasma membrane of the cell.
D. The cristae provides space for THOUSANDS OF COPIES of the chain IN EACH
MITOCHONDRION.
31.
MITOCHONDRION
A. MITOCHONDRION: An organelle in eukaryotic cells, bounded by two membranes, that
serves as the site of the reactions of aerobic metabolism.
32.
MITOCHONDRION
A. CRISTA: An in folding of the inner membrane of a mitochondrion that houses electron
transport chains and molecules of the enzymes catalyzing the synthesis of ATP (ATP
synthase).
B. MATRIX: The compartment of the mitochondrion enclosed by the inner membrane and
containing enzymes and substrates for the citric acid cycle.
C. INTERMEMBRANE COMPARTMENT: The fluid-filled space between the inner and
outer membranes of a mitochondrion.
33.
ELECTRON CARRIERS
A. Energy “fall” is broken up into a series of smaller steps by the ETC.
B. Oxygen is O2, as ETC reduces molecular oxygen.
C. Most components of the ETC are proteins in multi-protein complexes numbered I
through IV.
D. The electron transport chain makes NO ATP directly.
34.
ELECTRON CARRIERS
A. REMEMBER JIM JONES! Cyanide is an irreversible inhibitor of the enzyme cytochrome
c oxidase (also known as aa3 or cyt a3) in the fourth complex (IV) in the membrane of
the mitochondria of cells. It attaches to the iron within this protein. The binding of
cyanide to this cytochrome prevents transport of the electrons from cytochrome c
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oxidase to oxygen. ETC is disrupted; the cell can no longer aerobically produce ATP for
energy.
35.
CHEMIOSMOSIS uses ATP SYNTHASE
A. ATP SYNTHASE: a complex of several membrane proteins that provide a port through
which protons diffuse. This complex functions in chemiosmosis with adjacent electron
transport chains, using the energy of a hydrogen ion (proton) concentration gradient to
make ATP.
36.
CHEMIOSMOSIS:
A. An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion
gradient across a membrane to drive cellular work, such as the synthesis of ATP. Most
ATP synthesis in cells occurs by chemiosmosis.
B. Proton-motive force: The potential energy stored in the form of an electrochemical
gradient, generated by the pumping of hydrogen ions across a biological membrane
during chemiosmosis.
C. What is another way we make ATP?
37.
OXIDATIVE PHOSPHORYLATION
38.
CELLULAR RESPIRATION
A. Goal accomplished: harvesting the energy of glucose for ATP synthesis.
B. Glucose  NADH (FADH2)  ETC  Proton Motive Force  ATP
39.
CATABOLISM OF VARIOUS MOLECULES FROM FOOD
A. Remember, carbohydrates, fats, and proteins can all be used as fuel for cellular
respiration, entering the cycle at various points.
B. Proteins can be used for fuel, but first must be digested to the amino acids that
produced them. This process is deamination.
C. A metabolic sequence called beta-oxidation breaks the fatty acids down to two-carbon
fragments. These enter the cycle as acetyl CoA.
40.
DRAWING
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