Biology Lecture Chapter 9

Front 1

Cellular Respiration

Back 1

-Living cells require energy from
outside sources
-Organisms use glucose (C6H12O6)
as their main energy source

Front 2

Cellular Respiration 2

Back 2

-Cellular respiration is the process
of breaking down food molecules
to release energy (as ATP)
-Energy is released in the process
of respiration when the cells of
plants and animals convert sugar
and oxygen into carbon dioxide
and water

Front 3

Respiration

Back 3

-The breakdown of organic molecules
is exergonic

Front 4

Aerobic respiration

Back 4

Aerobic respiration consumes organic molecules and O2 and yields ATP (oxygen required)

Front 5

Anaerobic respiration

Back 5

Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 (no oxygen required)

Front 6

Fermentation

Back 6

Fermentation is a partial degradation of sugars that occurs without O2

Front 7

Cellular Respiration 3

Back 7

Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration

Front 8

Cellular Respiration Equation

Back 8

Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose:
C6H12O6 + 6 O2 ----> 6 CO2 + 6 H2O + Energy (ATP+heat)

Front 9

Redox Reactions

Back 9

-The transfer of electrons during
chemical reactions releases
energy stored in organic molecules
-This released energy is used to
make ATP
-Chemical reactions that transfer
electrons between reactants are
called oxidation-reduction
reactions, or redox reactions
-In cellular respiration, the glucose is oxidized and O2 is reduced

Front 10

Oxidation

Back 10

In oxidation, a substance loses electrons, or is oxidized

Front 11

Reduction

Back 11

In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced)

Front 12

NAD+

Back 12

-In cellular respiration, glucose and
other organic molecules are
broken down in a series of steps
-Electrons from organic compounds
are usually first transferred to
NAD+ (nicotinamide adenine
dinucleotide), a coenzyme

Front 13

NAD+ 2

Back 13

-As an electron acceptor, NAD+
functions as an oxidizing agent
-Each NADH (the reduced form of
NAD+) represents stored energy
that is tapped to synthesize ATP
-NADH passes the electrons to the
electron transport chain

Front 14

Electron Transport Chain

Back 14

Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction

Front 15

Electron Transport Chain 2

Back 15

-O2 pulls electrons down the chain in
an energy-yielding tumble
-The energy yielded is used to
regenerate ATP

Front 16

Stages of Cellular Respiration
(Glycolysis)

Back 16

Glycolysis - Anaerobic (breaks down glucose into two molecules of pyruvate)

Front 17

Stages of Cellular Respiration
(Citric Acid Cycle)

Back 17

Citric Acid Cycle - Aerobic (Kreb’s Cycle - completes the breakdown of glucose)

Front 18

Stages of Cellular Respiration
(Oxidative phosphorylation)

Back 18

Oxidative phosphorylation - Aerobic (ETC - accounts for most of the ATP synthesis)

Front 19

Mitochondria
(1.Glycolysis)

Back 19

Cytoplasm

Front 20

Mitochondria
(2.Citric Acid Cycle)

Back 20

Matrix of Mitochondria

Front 21

Mitochondria
(3.Oxidative Phosphorylation (ETC))

Back 21

Cristea of mitochondria

Front 22

Step 1: Glycolysis

Back 22

-“Splitting of sugar”
-Breaks down glucose (C6H12O6)
into two molecules of pyruvic acid
- AKA pyruvate (C3H4O3)
-Anaerobic
-Occurs in the cytoplasm
NAD picks up H+ and electrons
to form NADH2

Front 23

Glycolysis Summary

Back 23

Location: Cytoplasm

Front 24

Glycolysis Summary
(Reactants)

Back 24

-Glucose (6-C)
-2 NAD+
-2 ATP

Front 25

Glycolysis Summary
(Products)

Back 25

-2 Pyruvates (3-C)
-2 NADH
-4 ATP total
** 2 ATP NET since 2 are
used initially

Front 26

Bridge Reaction

Back 26

-In the presence of O2, pyruvate
enters the mitochondrion
-Before the citric acid cycle can
begin, pyruvate must be converted
to acetyl CoA, which links the
cycle to glycolysis

Front 27

In the mitochondria matrix…

Back 27

1) Pyruvic Acid loses a C to form
acetic acid (2-C)
2) The lost carbon binds with O2
making CO2
3)Acetic acid binds with
Coenzyme-A forming Acetyl
Co-A

Front 28

Step 2: The Kreb’s Cycle(Citric Acid Cycle)

Back 28

-Takes place within the mitochondrial
matrix
-There are 8 steps, each catalyzed by
a specific enzyme

Front 29

Step 2: The Kreb’s Cycle(Citric Acid Cycle) continued.....

Back 29

-The acetyl group of acetyl CoA
joins the cycle by combining with
oxaloacetate (4-C molecule),
forming a 6-C molecule known as
citric acid (citrate)
-The next seven steps decompose
the citrate back to oxaloacetate,
making the process a cycle

Front 30

Step 2: The Kreb’s Cycle(Citric Acid Cycle) continued 3......

Back 30

-2 molecules of CO2 are released
-NAD+ and FAD (flavin adenine
dinucleotide - another ion carrier)
pick up electrons and H+
becoming NADH and FADH2
-The NADH and FADH2 produced
by the cycle relay electrons
extracted from food to the electron
transport chain
-The cycle generates 1 ATP, 3
NADH, and 1 FADH2 per turn
-Recall that two molecules of
pyruvate are formed during
glycolysis resulting in two turns of
the Kreb’s cycle for each glucose
molecule!

Front 31

Kreb’s Cycle Summary

Back 31

Location: Mitochondrial Matrix

Front 32

Kreb’s Cycle Summary
(Reactants)

Back 32

-2 Acetyl Co-A

Front 33

Kreb’s Cycle Summary
(Products)

Back 33

-8 NADH (2 from transition)
-2 FADH2
-2 ATP
-6 CO2 (2 from transition)

Front 34

Step 3: Electron Transport Chain (ETC)

Back 34

-Aerobic process
-Requires oxygen as the final
electron acceptor
-Takes place in the cristae of the
mitochondria

Front 35

Step 3: Electron Transport Chain (ETC)
Part 2

Back 35

-A series of molecules that excited
electrons pass along, to release
energy as ATP
-Most of the chain’s components
are proteins, which exist in
multiprotein complexes

Front 36

Step 3: Electron Transport Chain (ETC) Part 3

Back 36

-Following glycolysis and the citric
acid cycle, NADH and FADH2
account for most of the energy
extracted from food
-These two electron carriers donate
electrons to the electron transport
chain, which powers ATP
synthesis via oxidative
phosphorylation

Front 37

NADH and FADH2

Back 37

-Dump the electrons and protons
they’ve gathered throughout
glycolysis and the citric acid cycle
-Again, oxygen is the final electron
acceptor
O2 + 2e- + 2H+ ------> H2O

Front 38

NADH and FADH2 (Part 2)

Back 38

-Electrons are passed through a
number of proteins including
cytochromes (each with an iron
atom) to O2
-The chain’s function is to break
the large free-energy drop from
food to O2 into smaller steps that
release energy in manageable
amounts
-ETC uses chemiosmosis to
generate large amounts of ATP

Front 39

Chemiosmosis

Back 39

-Electron transfer in the ETC
causes proteins to pump H+ from
the mitochondrial matrix to the
intermembrane space
-H+ then moves back across the
membrane, passing through
channels in ATP synthase
(enzyme that acts like an ion
pump)

Front 40

Chemiosmosis (Part 2)

Back 40

-ATP synthase uses the exergonic
flow of H+ to drive phosphorylation
of ADP
-This is an example of
chemiosmosis, the use of energy
in a H+ gradient to drive cellular
work
-The H+ gradient is called the
proton-motive force

Front 41

ETC Summary

Back 41

Location: Cristae of Mitochondria

Front 42

ETC Summary (Reactants)

Back 42

-10 NADH
-2 FADH2

Front 43

ETC Summary (Product)

Back 43

-34 ATP
-Each NADH makes 3
-Each FADH2 makes 2

Front 44

ETC Summary

Back 44

The bulk of ATP is made in the ETC!!

Front 45

Total Energy

Back 45

38 ATP's per 1 glucose broken down

Front 46

Total ATP from 1 molecule of glucose in AEROBIC CONDITIONS

Back 46

Stage ATP
-+ 4 Total
-Glycolysis -+ 2 NET (b/c 2
are used in
the first step)
-CA Cycle -+2
-ETC -+34
-----------------------------------------------
Total -+38

Front 47

Total Energy (Part 2)

Back 47

-During cellular respiration, most
energy flows in this sequence:
Glucose -> NADH -> electron
transport chain -> proton-motive
force -> ATP
-About 40% of the energy in a
glucose molecule is transferred to
ATP during cellular respiration,
making about 38 ATP

Front 48

Fermentation

Back 48

-Most cellular respiration requires
O2 to produce ATP
-Glycolysis can produce ATP with
or without O2 (in aerobic or
anaerobic conditions)
-In the absence of O2, glycolysis
couples with fermentation or
anaerobic respiration to produce
ATP
-Fermentation uses
phosphorylation instead of an
electron transport chain to
generate ATP

Front 49

Fermentation (2 types)

Back 49

-Lactic Acid Fermentation
-Alcohol Fermentation

Front 50

Lactic Acid Fermentation

Back 50

-In lactic acid fermentation,
pyruvate is reduced to NADH,
forming lactate as an end product,
with no release of CO2
-Lactic acid fermentation by some
fungi and bacteria is used to make
cheese and yogurt
-Human muscle cells use lactic
acid fermentation to generate ATP
when O2 is scarce

Front 51

Lactic Acid Fermentation (Part 2)

Back 51

-Example: Burning feeling in
muscles during a workout
-From oxygen debt
-Aerobic respiration cannot
occur
-Lactate builds up in muscles
leaks into blood

Front 52

Alcohol Fermentation

Back 52

-In alcohol fermentation, pyruvate is
converted to ethanol (type of
alcohol) in two steps, with the first
releasing CO2
-Bacteria and fungi (yeast)
-Alcohol fermentation by yeast is
used in brewing, winemaking, and
baking

Front 53

Fermentation (Obligate anaerobes)

Back 53

-Obligate anaerobes carry out
fermentation or anaerobic respiration
and cannot survive in the presence of
O2

Front 54

Facultative anaerobes

Back 54

-Yeast and many bacteria are
facultative anaerobes, meaning that
they can survive using either
fermentation or cellular respiration

Front 55

Role of Macromolecules

Back 55

-Catabolic pathways funnel
electrons from many kinds of
organic molecules into cellular
respiration
-Glycolysis accepts a wide range
of carbohydrates
-Proteins must be digested to
amino acids
-Amino groups can feed
glycolysis or the citric acid
cycle

Front 56

Role of Macromolecules (Part 2)

Back 56

-Fats are digested to glycerol (used
in glycolysis) and fatty acids (used
in generating acetyl CoA)
-Fatty acids are broken down
by beta oxidation and yield
acetyl CoA
-An oxidized gram of fat produces
more than twice as much ATP as
an oxidized gram of carbohydrate

Front 57

Regulation of Cell Respiration

Back 57

-Feedback inhibition is the most common mechanism for control
-If ATP concentration begins to
drop, respiration speeds up
-When there is plenty of ATP,
respiration slows down

Front 58

Regulation of Cell Respiration (Control of catabolism)

Back 58

-Control of catabolism is based mainly
on regulating the activity of enzymes
at strategic points in the catabolic
pathway