LO’s
Cellular Respiration
- Able to understand the processes of glycolisis, the
citric acid cycle, krebs cycle and electron transport
system.
- Able to compare between photosynthesis and cellular
respiration
Cellular Respiration
• Process that unlocks stored energy
– Nutrient molecules store energy in bonds
– Chemical reactions produce ATP
– ATP provides cellular energy
Skunk cabbage using metabolic
heat to melt snow
ATP
• ATP powers cellular work
• A cell does three main kinds of work:
– Mechanical work, beating of cilia, contraction of muscle
cells, and movement of chromosomes
– Transport work, pumping substances across membranes
against the direction of spontaneous movement
– Chemical work, driving endergonic reactions such as the
synthesis of polymers from monomers
• The bonds between phosphate groups can be
broken by hydrolysis.
So what?
• Energy is stored in these bonds.
• So?
• The breaking of the chemical bond releases
the energy
ATP + H2O→ ADP + P + ENERGY
Photosynthesis and cellular respiration – provide energy for life
Photosynthesis is the process where green plants use sunlight, carbon
dioxide, and water to make food and oxygen (chloroplasts- chlorophyll)
6CO2 + 6H2O + energy --> 6O2 + C6H12O6
Cellular Respiration is the process where cells use this food to release
stored energy (mitochondria)
 takes glucose, breaks it down into atoms, and by mixing it with the atoms from
more oxygen, produces carbon dioxide, water and energy ... A new energy is form
and it can be used by all cells
6O2 + C6H12O6 --> 6H2O + 6CO2 + energy (ATP)
The theoretical maximum yield of cellular respiration is 36 ATP per molecule of
glucose metabolized.
Chemical Reactions for Photosynthesis
• Light dependent reactions
• Light independent reactions
Cellular respiration
The process by which
mitochondria break down
glucose to make ATP
Cellular respiration metabolic reactions /processes;
to convert biochemical energy from nutrients into adenosina
triphospahte (ATP), and then release waste products.
ATP : covalent bonds between atoms
6O2 + C6H12O6 --> 6H2O + 6CO2 + energy (ATP)
Glucose looses electrons and hydrogen and oxygen gains electrons and hydrogen
During this process heat energy is released. This is a redox reaction; a chemical
reaction that transfers electrons from one substance to another aka oxidationreduction reactions. Oxidation is the loss of electrons during a redox reaction and
reduction is the acceptance of electrons during a redox reaction.
The reactions involved in respiration are catabolic reactions that involve the redox
reaction (oxidation of one molecule and the reduction of another). Respiration is one
of the key ways a cell gains useful energy to fuel cellular reformations.
Cellular Respiration - Aerobic respiration
requires oxygen in order to generate energy
(ATP)
• Chemical reactions to
yield energy
– Break down
carbohydrates
– Series of reactions
Aerobic Cellular Respiration
• Oxygen dependent
• Byproducts
– Raw materials for
photosynthesis
– Carbon dioxide
– Water
Cellular respiration
Three metabolic processes:
 Glycolysis - cytosol
 Krebs cycle - takes place in the matrix of the mitochondria
 Oxidative phosphorylation - via the electon transport
chain is carried out on the inner mitochondrial membrane
In the absence of oxygen, respiration consists of two metabolic pathways:
glycolysis and fermentation. Both of these occur in the cytosol.
Glycolosis
Glyco = glucose Lysis = break down
Occurs in the cytoplasm
This stage occurs in BOTH aerobic and anaerobic
respiration
Glucose breaks down into 2 pyruvate (2 ATP are also
made)
Glucose is a 6-carbon sugar
Pyruvate is a 3-carbon molecule (there are two of them)
Glycolosis - glucose is split into pyruvic acid.
Glucose, a six carbon sugar, is split into two molecules of a three carbon sugar. In
the process, two molecules of ATP, two molecules of pyruvic acid and two "high
energy" electron carrying molecules of NADH are produced.
In the presence of oxygen, glycolysis is the first stage of cellular respiration.
Without oxygen, glycolysis allows cells to make small amounts of ATP. This
process is called fermentation.
There are 4 important stages in Glycolysis:
• Activation of glucose by ATP
• Splitting of glucose into two roughly equivalent phosphorylated halves
• Reduction of NAD+ to NADH
• Phosphorylation of ADP
Glycolysis Reactants and Products
Reactants
• 1 glucose
• Enzymes are needed
• 2 ATP are needed to
start
Products
• 2 Pyruvates (go to next
step)
• 4 ATP (2 are gained)
• 2 NADH (go to ETC)
Intermediate step
• Pyruvate is converted to acetyl CoA
• Occurs in the cytoplasm
• See diagram on simple explanation handout
Intermediate step Reactants and products
Reactants
• 2 pyruvate (from
glycolysis)
Products
• 2 Acetyl CoA (go to next
step)
• 2 CO2 (given off as
waste)
• 2 NADH (go to ETC)
Krebs Cycle (Citric Acid Cycle)
• Occurs in the matrix of mitochondria
• A series of reactions occur (this is not just one
step)
• Main purpose is to generate electrons for use
in ETC
• 2 ATP is given off
• See diagram on simple explanation handout
Krebs Cycle Reactants and Products
Reactants
• 2 Acetyl CoA
Products
•
•
•
•
2 ATP
6 NADH (go to ETC)
2 FADH2 (go to ETC)
4 CO2 (given off as
waste)
Electron Transport Chain
• Occurs in inner membrane of mitochondria
• Series (chain) of coupled redox reactions
(electrons are transported through the chain)
• Electrons carried to this step by NADH and
FADH2 (produced in previous steps)
• Oxygen is used in this step
• Water is given off
Electron Transport Chain Reactants and Products
Reactants
• 10 NADH
• 2 FADH2
• Oxygen
Products
• 34 ATP
• H2O
Where do we get 38 ATP?
• 2 ATP made in glycolysis
• 2 ATP made in Krebs Cycle
• 34 ATP made in ETC
– 1 NADH = 3 ATP
o 10 X 3 = 30
– 1 FADH2 = 2 ATP
o2 X 2 = 4
Anaerobic Respiration (Fermentation)
Fermentation is the anaerobic harvest of food energy.
Anaerobic respiration occurs when your cells need more ATP than your
bloodstream’s delivery of oxygen can supply.
Common in yeast, molds, some bacteria
Carbon & hydrogen not fully oxidized
Less energy than aerobic respiration. It can produce 2ATP per
glucose molecule.
By oxidizing the NADH produced in glycolysis, fermentation regenerates NAD+, which
can take part in glycolysis once again to produce more ATP.
Anaerobic Respiration (Fermentation)
• Glycolysis
• Yields 2 pyruvate and 2 ATP
• With no oxygen present, cellular respiration
does not occur
• ONLY 2 ATP ARE PRODUCED (compare to
aerobic respiration)
Two Types of Fermentation
Alcoholic Fermentation
• Pyruvate converted to
ethyl alcohol and CO2
• Carried out by yeast
and some bacteria
• Used in producing
alcohol (both
consumable and for
ethanol), and for baking
Lactic Acid Fermentation
• Pyruvate converted to
lactic acid
• Carried out by muscles
when working hard
(muscles need ATP but
can’t get O2 )
• Causes muscle soreness
and cramps
Photosynthesis
• Carried out by most (not all) autotrophs
• 6CO2 + 6H2O + light energy→ C6H12O6 + 6O2
• Basically this reaction is the OPPOSITE of cellular
respiration
• See simple explanation handout and text
Steps of Photosynthesis
1. Light reaction (depends on light)
•
•
•
Traps sunlight
Produces electrons and ATP required to power the
dark reaction
Oxygen given off here
2. Dark reaction, aka Calvin Cycle (does not
directly depend on light)
•
Uses ATP and electrons from light reaction and CO2
to make glucose
See diagram on simple explanation handout
Cellular respiration - in presence of O2
• Yields
– ATP from ADP
– Carbon dioxide & water from glucose & oxygen
Three Phases Of Aerobic Cellular Respiration
Aerobic Cellular Respiration happens in
Mitochondria. Three main reactions are involved:
1. Glycolisis occurs in cytoplasm of mitochondria
(requires 2 ATP to start/ makes 2 ATP)
2. Krebs Cycle occurs in matrix of mitochondria
(makes 2 ATP)
3. Electron Transport Chain occurs in
mitochondria; makes majority of ATP (32 ATP)
Out of 38 ATP Produced - energy of 2 ATP required
to start the process.