chapter 9: cellular respiration and fermentation
TRANSCRIPT
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Chapter 9: Cellular
Respiration and Fermentation
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Essential Knowledge
2.a.1 – All living systems require constant input of free energy (9.1-9.5).
2.a.2 – Organisms capture and store free energy for use in biological processes (9.1-9.5).
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Cellular Respiration - Preview
Def - The process of releasing energy/ATP from food
Food - Stored energy in chemical bonds (provides fuel)
ATP - Useable energy for cellular processes
Wastes – CO2 and H2O Mitochondrion store most of
equipment needed for rxn
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Respiration (Rs) - Equation
C6H12O6 + 6 O2 6 CO2 + 6 H2O +
energy (ATP or heat) Rxn is spontaneous (-∆G) The energy is released (exergonic) from
the bonds in the org moleculesRemember: Org molecules store energy in
their arrangement of atomsOrg molecules can be carbs, proteins or
fats/lipids
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Focus of Chapter
Cellular Rs1. Purpose - what is the reaction suppose
to do for the cell?2. Location - where does it occur?3. Requirements - what is needed to
make it run?4. Products - what does it produce?
Other Fermentation, Redox
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Fuel? What is used?
Organic molecules with a large amt of hydrogen make great fuel! Why?H becomes oxidized (only has one e-)
very easily and energy is releasedRemember: Carbs, fats, proteins are
storage bins for e- associated with hydrogen
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Oxidation - definitions Loss of electrons Loss of energy Loss of hydrogens from
carbons Ex: Na+ (of NaCl)
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Food and Oxidation
Food (organic molecules) contain a lot of H atomsThese serve as great long-term
fuelsWhy?○ Because H becomes easily oxidized
(releases energy frequently)
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Reduction - definitions Gain of electrons (REDUCING +
charge) Gain of energy Gain of hydrogens to carbons Ex: O is often reduced!
Why? Because electrons are pulled closer
to O
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Redox reactions
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Equation for Rs
C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy (ATP/heat)
General Redox Equation: Xe- + Y X + Ye-
Reduced
Oxidized
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Redox reactions Involves transfer of e- and energy
releaseSometimes doesn’t involve complete
transfer Red and Oxd reactions are usually
paired or linked together. Why?Because e- transfer requires donor
and acceptor Many of the reactions will be done
by phosphorylation Redox video
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Phosphorylation
Adding a phosphate group to a moleculeEx: ATP cycle (add P to ADP = ATP)
Two types: Oxidative AND substrate-level
The phosphate group adds “energy” to the molecule for chemical reactions (think ATP cycle)Endergonic rxn
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Phosphorylation
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Cell Respiration – 3 parts1. Glycolysis2. Krebs Cycle3. Electron Transport Chain
**Use page 167 as a starting point: Cellular Respiration - A Preview
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Glycolysis
Glyco- glucose -lysis: to split Formula for glucose: C6H12O6
Universal step in all Rs types. Likely the earliest type of cell energy
processes Overview:
Glucose splits into 2 3-C sugars (then oxidizes to form pyruvate)
STEP 1
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Glycolysis Function - To split glucose and
produce NADH and ATPATP made by substrate-level
phosphorylation○ Enzyme transfers phosphate group
from substrate/reactant to ADP to make ATP
Location – Cytoplasm of the cell
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Electron Carrier Compounds
Molecules that transport or shuttle electrons within the cell
Exist in two forms: Oxidized (ox)Reduced (red)
Ex: NAD and FAD
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NAD
Nicotinamide Adenine Dinucleotide NAD+ + 2 e- NADH NAD+ = oxidized form NADH = reduced form*
*Reduced by e- from food oxidation
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Glycolysis Requirements
Glucose 2 ATP 4 ADP 2 NAD+
Can occur with or without O2
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Glycolysis - Products 2 Pyruvic Acids (a 3-Carbon acid) 2 ADP, 4 ATP, 2 NADH NET RESULT:
2 ATP per glucose2 NADH2 pyruvateH2O
Notice:No CO2 made during
this step!
Glycolysis Intro
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Krebs Cycle
Oxidizes fuel from pyruvate molecules Remember? Pyruvate formed during
glycolysis Also called:
Citric Acid CycleTricarboxylic Acid Cycle
STEP 2
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Krebs Cycle Function: Oxidize pyruvic acid (to
make CO2 ) Produces: NADH and FADH2
Location: Mitochondria matrix Before Krebs: Acetyl CoA must be
formedAcetyl CoA is needed to actually start
Krebs
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Pyruvate moved into mito?
Why? How?Pyruvate is moved into mitochondria
(from cytoplasm) Why? This is where the 2nd step
occurs (specific enzymes are in mito)Serves as a checkpointUses active transport and transport
proteins. ○Why? Pyruvate is a charged molecule!
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Formation of Acetyl CoA
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Krebs Cycle Requirements
Pyruvic acid (3C acid) Acetyl coenzyme A 4 NAD+
1 ADP 1 FAD Double this list for each glucose
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Krebs Cycle Products 3 CO2
Acetyl CoA 4 NADH 1 FADH2
1 ATP
Double this list for each glucose
Made from pyruvate
LOADS of energy stored in these molecules
Krebs Cycle Intro
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Krebs Cycle notes Notice:
Only 1 ATP made per cycleProduces most of the cell's energy in
the form of NADH and FADH2
Does NOT require O2
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Comment about ATP The ATPs produced directly in Krebs
Cycle and Glycolysis are by:Substrate-level phosphorylation
The P group is transferred from a substrate to ADPMaking ATP
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At this point…
After the Krebs and glycolysis cycles, the cell has made a total of 4 ATP. Remember: some ATP had to be used to
power the cycles. Most energy (at this point) comes from
NADH and FADH2
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Electron Transport System
ETC/S or Electron Transport Chain This is a collection of proteins that are
structurally linked Located in inner membrane of mito
Folding of mito (cristae) allows for lots of places (large surface area!) for ETC to occur
STEP 3
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ETC/S Uses sets of Cytochromes
Fe (Iron)-containing proteins to pass electrons The Cytochromes alternate between Red
and Ox forms and pass electrons down to O2
Remember: LEO, GER; LEO the lion goes GERLosing Electrons is Oxidation; Gaining
Electrons is Reduction
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As e- moves
down the ETC, free energy
decreases
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ETC/S
Function: Convert NADH and FADH2 into ATP
Location: Mitochondria cristae/folds
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ETC Requirements NADH or FADH2
ADP O2
We finally see the need/requirement of Oxygen
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ETC Products NAD+ and FAD ATP (LOTS!!!) H2O
Remember: Water was also produced during glycolysis
ETC explanation
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ETC - ATP Yields
Each NADH 3 ATP Each FADH2 2 ATP
TOTAL: 34 ATP
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Chemiosmotic Hypothesis ETC energy is used to move H+
(protons) across the mito/cristae membrane
ATP is generated as the H+ diffuse back into the matrix
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ATP Synthase Enzyme An enzyme that uses the flow of H+ to
make ATP Works like an ion pump in reverse, or like
a waterwheel under the flow of H+ “water”
Power source: H+ concentration difference on opposite sides
of mitochondrial membrane
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Oxidative Phosphorylation
ATP synthase uses oxidative phosphorylation to make ATP during ETC
Uses H ions to make ATP and water (using Oxygen)
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ATP Synthase
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Alcoholic Fermentation
Done by yeast A kind of fungus
Used in brewing beer, winemaking, and bakingCO2 bubbles generated give:○ Bread a rising effect○ Wine/Beer the carbonated effect
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Alcoholic Fermentation Uses only Glycolysis An incomplete oxidation - energy
is still left in the products (alcohol) Does NOT require O2
Produces ATP (when O2 is not available)
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Alcohol
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Lactic Acid Fermentation Uses only Glycolysis An incomplete oxidation - energy is
still left in the products (lactic acid) Does NOT require O2
Produces ATP (when O2 is not available)
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Lactic acid
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Lactic Acid Fermentation
Done by human muscle cells under oxygen debtLactic Acid is a toxin and can cause
soreness and stiffness in musclesOxygen intake can’t keep up with sugar
breakdown Used in dairy industry (yogurt/cheese) Also used to produce methanol and
acetone
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Fermentation - Summary Way of using up NADH so
Glycolysis can still run Provides ATP to a cell even when O2
is absent
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Fermentation
*Alcoholic OR*Lactic acid
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Aerobic vs Anaerobic
Aerobic - Rs with O2
Anaerobic - Rs without O2
Aerobic - All three Rs steps Anaerobic - Glycolysis only
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Strict vs. Facultative
Strict - can only do Rs this one way Either aerobic OR anaerobic-NOT both!
Facultative - can switch types depending on O2 availabilityEx - yeast
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Question??
Since yeast can do both aerobic and anaerobic Rs, which is the better process if given a choice?Hint: Check the ATP yields from both
processes.
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ATP yields by Rs type
Anaerobic - Glycolysis only gets 2 ATPs per glucose
Aerobic - Glycolysis, Krebs, and ETC. Generates many more ATPs per
glucose.
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Aerobic ATP yield
Glycolysis - 2 ATPS, 2 NADHs Krebs - 2 ATPS, 8 NADHs, 2 FADH2
Each NADH = 3 ATP Each FADH2 = 2 ATP
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Aerobic ATP Sum
10 NADH x 3 = 30 ATPs 2 FADH2 x 2 = 4 ATPs 2 ATPs (Gly) = 2 ATPs 2 ATPs (Krebs) = 2 ATPs
Max = 38 ATPs per glucose
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However...
Some energy (2 ATP) is used in shuttling the NADH and pyruvate from Glycolysis into the mitochondria
Actual ATP yield ~ 36/glucose
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Yeast Would rather do aerobic Rs;
This has 18x more energy per glucose than anaerobic
But, anaerobic will keep you alive if oxygen is not present.
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Importance of Rs
Convert food to ATPLiving orgs use ATP to fuel body
processesEx: reproduction, cell division
Provides materials for use in other cellular pathways
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Other Respiration Items of Importance
Alcohol Industry - almost every society has a fermented beverage
Baking Industry - many breads use yeast to provide bubbles to raise the dough
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Alcohol Matching Game!
Sugar Cane GinBarley RumGrapes
WineJuniper Cones
VodkaAgave Leaves
BeerRice TequilaPotatoes Saki
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Summary
Identify the basic chemical equation for cellular respiration.
Identify the main reaction sequences of cellular respiration.
Recognize the location, function, requirements, and products, for each cellular respiration reaction.
Recognize and be able to discuss the chemiosmotic model for ATP generation.
Recognize the reactions and importance of fermentation. Contrast and compare aerobic and anaerobic respiration. Identify the biological and commercial importances of
respiration.
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Exclusion Statements
You do NOT need to memorize the steps in glycolysis and the Krebs cycle, the structures of the molecules, or the names of the enzymes that are involved.
You do NOT need to memorize the names of the specific electron carriers in the electron transport chain (ETC).