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7.1 The Importance of Cellular
Respiration
Pg. 204-209
Introduction to Chapter 7
 The primary role of photosynthesis is to convert light energy into
glucose. Glucose in cellular respiration is converted to ATP.
 The glucose can be used immediately, transported or stored, or used to
synthesize other energy molecules.
 Plants store glucose as starch
 Animals and fungus store glucose as glycogen
 The role of cellular respiration is to supply the body with ATP.
 ATP, released from the cells of plants and animals (glucose) that
store energy. ATP can then be use to conduct cellular processes.
 The summarized equation is:
 Similar to photosynthesis, electrons move from molecule to
molecule as energy is transferred.
 Oxidization reaction release energy
 This energy is used to make ATP
 Electron acceptors in Cellular Processes are: NAD+ and FAD
 Electron donors in Cellular Processes are: NADH and FADH2
 Act as electron carriers, transfer electrons through Oxidation-
Reduction reactions.
 The transfer of electrons releases energy that can be used in cellular
respiration and other cellular processes and in the making of ATP.
Pg. 205 Fig.1
The energy released from the
oxidation-reduction reaction is
used to attach a free phosphate to
ADP to make ATP.
Note that the ATP is a highenergy compound. The
oxidation-reduction reaction
could be the transfer of elections
from high-energy compounds
such as when NADH is oxidized
to from NAD+ and H+.
Energy, Cells and ATP
 ATP supplies the energy cells require
 An average cell has one billion molecules of ATP.
 They are continually broken into ADP and P as they release energy to do
work, and then remade into ATP
 Active transport is one of the uses for ATP.
 This is the movement of substances through a membrane against a
concentration gradient.
 This happens through proteins called “pumps”
 Eg. Hydrogen protein in the thylakoid membrane
 Example: The sodium-potassium pump
 Sodium is pumped out, potassium into the
cell
 Notice for every 3 Na + pumped out, 2 K+
are pumped in (pg. 206 Fig.3)
 Without this pump, nerve cells and muscle
cells could not function properly. Other
substances, such as vitamins, amino acids, and
hydrogen ions are also actively transported
across membranes by specialized carrier
proteins.
 All of theses pumps require energy from ATP
to operate.
 E.g. of the Importance of Cellular Respiration
 This is a diagram of active transport.
 Active transport. The molecule to be transported attaches to an
open binding site on one side of the carrier protein. ATP is
converted to ADP on the carrier protein and releases energy. The
energy causes a change in the shape of the protein that carries the
solute to the other side of the membrane.
 Other critical uses of ATP are listed below:
 Large-scale motion ie muscle fibers contracting, their shape changes
as the result of energy from ATP.
Glucose and ATP
 Glucose is relatively small and is highly soluble. Thus, it is ideal for
transport between cells. (is our blood sugar)
 But why do we need glucose when it is ATP that is needed to run our
cells?
 All cells use energy from ATP molecules to meet their metabolic energy
needs.
 ATP is not abundant in food and provide relatively small amount of
energy.
 Large molecules like sugars are used for storage of energy as well as
transportation of energy.
 During cellular respiration, some of the energy in glucose is
converted to ATP.
Glucose and ATP
 A cell is like a large factory in which operations are performed by
vending machines that only accept $1 coins. Inorder to perform any
task (any cellular action) within the factory, you need a $1 coin.
 In cells $1 = ATP, virtually all processes conducted by cells use ATP
molecules only as their immediate energy source.
 What happens when a $100 bill (glucose) arrives?
 It is very valuable, but needs to be exchanged to $1 coins (ATP) before
it can be used to run the vending machines (cellular activities).
Releasing Energy
 During cellular respiration, chemical bonds in food are broken and
new bonds are formed. The result is a release of energy.
 Yet, it requires energy to break
the original bonds before the
release of energy can take
place.
 Cellular Respiration releases more energy (ATP)
than it used to break apart the reactant
molecules (food).
 Even though glucose($100) has significantly more energy than
ATP ($1), the energy is not all available for cellular use.
 The conversion of glucose to ATP is only approximately 36%
efficient.
 64% of the energy is lost as heat.
 This seems like a lot of waste, but remember that animals and
birds use this energy to keep warm.
Two Types of Cellular Respiration
 There are two different pathways in which glucose can be converted
into ATP
 The two processes are aerobic respiration and anaerobic respiration.
 Aerobic Cellular Respiration uses oxygen
Summarized formula:
 There are four stages to Aerobic Cellular Respiration :
 1. Glycolysis, 2. pyruvate oxidation, 3. The Krebs cycle, 4. The
electron transport chain and chemiosmosis
 Notice 36 ATP are made from one glucose!
 Anaerobic Cellular Respiration does not use oxygen. (absence of
oxygen) (glucose is not completely oxidized)
 There are 2 types with 2 different end products
 For each of these processes, there are two stages: glycolysis and
fermentation
 Anaerobic respiration only produces 2 ATP for every glucose
molecule
The Importance of Cellular Respiration
 Cells cannot use high-energy molecules, such as glucose,
directly. Cellular respiration converts glucose into energycontaining molecules the cells can use directly, such as ATP.
 Cells use ATP for their immediate energy needs.
 Aerobic cellular respiration takes place in the presence of
oxygen and produces 36 ATP molecules per glucose
molecule.
 Anaerobic respiration takes place in the absence of oxygen
and produces 2 ATP molecules per glucose molecule.
Homework…
 Textbook:
 Pg. 205 #1-2
 Pg. 207 #3-5
 Pg. 209 #1-5
 Pg. 200 #1-12,14-18
 Study for QUEST chp. 6! Its tomorrow!
 Key: pg.81-83 practice Test 1 #1-13, WR1
Glycolysis & Pyruvate Oxidation
Pg. 210-215
Aerobic Cellular Respiration
 Stage 1: glycolysis—a 10-step
process occurring in the
cytoplasm
 Stage 2: pyruvate oxidation—a 1
step process occurring in
mitochondria matrix
 Stage 3: the Krebs cycle—an 8-step
cyclical process occurring in
mitochondria matrix
 Stage 4: the electron transport chain and
chemiosmosis (oxidative
phosphorylation) –a multi step process
occuring in the inner mitochondrial
membrane
Stage 1: Glycolysis
 Glycolysis occurs at the beginning of both
anaerobic and aerobic respiration.
 Glucose can not be used directly by the cell,
thus glycolysis splits the glucose in half during
the first step of both types of cellular
respiration.
 Glycolysis is Greek for “sugar splitting”.
Glycolysis
 All ten reactions that occur in glycolysis do not require oxygen
• You will only have to know:
– 2 ATP are used &
4 ATP and in redox reactions 2
NADH are made.
– One 6 carbon molecule becomes
two 3-carbon molecules
(pyruvates)
– Takes place in the cytoplasm of
the cell. ATP are now available to
supply energy for cellular
functions.
 The reactants and Products of Glycolysis
 The net equation for glycolysis:
 Glycolysis is very inefficient:
 Only 2.2% of the energy from glucose is converted into ATP
 Yet, the two pyruvates and two NADH are used later to produce ATP.
 Some single celled organisms can live with just using glycolysis.
 Multicellular organisms require more, thus the energy from the 2
pyruvates must be converted into ATP so this is the 1st step in eg.
Aerobic respiration.
Aerobic Cellular Respiration
 Of the four stages of aerobic respiration, only the first step
(glycolysis) does not need oxygen.
 The next three steps: pyruvate oxidation, the Krebs cycle and the
electron transport chain occur in the presence of oxygen.
 Glycolysis occurs in the cytoplasm, but the following stages, which
produce the most ATP, occur in mitochondria, and require oxygen.
 Mitochondria are eukaryotic cell



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organelles that conduct
aerobic cellular respiration
Specific reactions occur in
specific areas of the
mitochondria:
The Matrix is the fluid that
fills the inner space of the mitochondria
Intermembrane space is the fluid filled space between the inner and
outer mitochondrial membranes
of mitochondrial structure.
Stage 2: Pyruvate Oxidation
 This stage connects glycolysis in the cytoplasm with the Krebs
cycle in the mitochondrial matrix.
 Two pyruvate molecules enter this stage and are
transformed into
acetyl-CoA
 Each pyruvate that enters the mitochondrial matrix produces:
a CO2, a NADH and a acetyl-CoA
 The CO2 is removed from the pyruvate and released as a waste; produced
here is 1/3 of the carbon dioxide that you breathe out.
 Pyruvate (the 2-C) are oxidized by NAD++2H++2e-  NADH. This
converts pyruvate to an acetic acid group and transfers high-energy
hydrogens to NADH.
 The acetyl-CoA formed will be used in the Krebs Cycle & the NADH will
be used in the electron Transport system
Homework…
 Textbook:
 Pg. 212 #1-3
 Pg. 215 #1-3
 Study for Quiz pg. 210-215 Stage 1&2
 Key: Read pg. 65-68 practice Qs #11,12,15-17
 Watch 1st 2 videos (paper response) 5-7 pts each.
Stage 3: Krebs Cycle & 4:ELT
7.2b Pg. 215-220
Review: Act it out… 
 ATP ADP + P
 Energy is released.
 ADP + P ATP
 Energy is stored.
Aerobic Cellular Respiration
 Stage 1: glycolysis—a 10-step process
occurring in the cytoplasm
 Stage 2: pyruvate oxidation—a 1 step
process occurring in mitochondria
matrix
 Stage 3: the Krebs cycle—an 8-step
cyclical process occurring in
mitochondria matrix
 Stage 4: the electron transport
chain and chemiosmosis (oxidative
phosphorylation) –a multi step
process occurring in the inner
mitochondrial membrane
Stage 3: The Krebs Cycle
 This is an 8-step process which requires an enzyme at each step.
 Reactions that transfer energy from organic molecules to ATP,
NADH, FADH2, and removes Carbon atoms as CO2
 The final product in stage 8 is used in stage 1 of the cycle.
The Krebs cycle
occurs here
 The result of each
cycle produces free energy as:
3 NADH’s, a FADH2
and an ATP.
 There is also 2 CO2
Created as waste.
 REMEMBER 1 glucose makes two
3-C which each make two acetylCoA, so the Krebs cycle occurs
twice for 1 glucose molecule.
Products*2
 Notice that all 6 C will be oxidized
to CO2 and released from the cell
as metabolic waste. …What do
plants need?
 NADH and FADH2 go to Stage 4.
Stage 4: Electron Transport and Chemiosmosis
 The Electron transport system takes energy from NADH and
FADH2 in a chain reaction to pump H+ into the intemembrane
space of the mitochondria.
 Ongoing process with countless NADHs and FADH2 (has lower
electron energy) delivering e-s to the ETC continuously.
 The NADH and to a lesser extent FADH2 give up high energy electron to





the ETC.
These electrons are passed down a number of protein pumps which push
H+ through the inner mitochondrial membrane.
The build up of H+ in the intermembrane space produces a large amount
of potential energy.
This system results in a transformation of chemical energy into
electrochemical energy.
Note that Oxygen is the last electron acceptor in the electron transport
system. (We -aerobic organisms- need Oxygen!)
The chemical energy of the electrons is converted electrochemical
potential energy of an H+ ion gradient that forms across the inner
mitochondrial membrane. This energy is used to make lots of ATP in
chemiosmosis.
Chemiosmosis & Oxidative ATP Synthesis
 Chemiosmosis: a process for synthesizing ATP using the energy of an
electrochemical gradient and the ATP synthase enzyme.
 This is the place where most of the ATP made by our bodies occurs.
 This happens just like the processes found in plant cell that contain
chloroplasts.
 The build up of H+ in the intermembrane space produces a large
amount of potential energy in the electrochemical gradient.
 An ADP is converted to an ATP as H+ moves across the
electrochemical gradient through the ATPase complex (ATP
synthase).
 One NADH pump enough H+ ions
across to generate 3 ATP; One
FADH2 pump enough H+ ions across
to generate 2 ATP.
 Energy is released in the ETC by a
series of oxidations which result in
the production of ATP.
 Thus, the process referred to as
Oxidative ATP synthesis.
 ETC and Chemiosmosis need
electrons (from food, ie glucose) and
oxygen (acts as an electron
acceptor).
Aerobic Respiration Energy Balance Sheet
 How much energy was transferred from glucose to ATP in the entire
aerobic respiration process?
 A total of 36 ATP are created in the processing of one glucose.
 Can you identify
where the ATP
were produced?
Note in Glycolysis the NADHs
produced are not able to generate 3
ATP each, instead they transfer their
electrons to FADs which are used in
the ETC to produce 2 ATPs each.
Remember that glycolysis was 2.2%
efficient, aerobic respiration is over
32% efficient, so the actual yield is
about 30 ATP
Aerobic Respiration Energy Balance Sheet
Homework… All to hand in.
 Textbook:
 Pg. 219 #4-6
 Pg. 220 #1-10
 Key:
 Pg. 68 Read & Qs #4,6,13,14,18,NR1, NR2, NR3