PHOTOSYNTHESIS &
CELLULAR RESPIRATION
Definitions
• Photosynthesis
– How a Plant (Autotroph) Harnesses Light
Energy to Make Chemical Energy
• Respiration
– Turning Chemical Energy into Fuel for
Growth, Development & Reproduction
Autotrophs – produce their own food like plants.
What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the most important
chemical reaction on our planet.
Photosynthesis Described:
• The process of changing light energy to
chemical energy
• The Chemical Energy is stored as sugar
• Occurs in AUTOTROPHS: plants & some algae
• Plants need light energy, CO2, and H2O
• Takes place in the chloroplasts, using
chlorophyll, the green pigment in plants
Chloroplasts
• Organelles that
are only found in
a Plant Cell
• Location of
Photosynthesis
http://www.lclark.edu/~seavey/Bio100_03/Lecture%20notes/lecture_Feb_11.h
What do plants need for
photosynthesis?
•Water
•Carbon dioxide
•Light
•chlorophyll
PHOTOSYNTHESIS EQUATION:
6 CO2 + 6 H2O + light  C6H12O6 + 6 O2
ENERGY IN A
CELL!!
• Your body requires energy in order to
function…from your heart beating to
intense workouts.
• Energy is essential to LIFE!!
• Your body stores energy in a molecule
called ATP (adenosine triphosphate)
• This is a quick source of usable energy
for any organelle in the cell that needs it.
The energy inside an ATP
molecule is released when it
loses a phosphate and
becomes
ADP (adenosine diphosphate)
triphosphate  diphosphate
3 x PO4  2 x PO4
ADP is like a partially charged battery
while ATP is a like a fully charged battery.
PHOTOSYNTHESIS
Photosynthesis
occurs in
organelles,
present in green
plants and certain
algae, called
Chloroplasts.
Chloroplast
Chloroplast
These
chloroplasts
contain the
green pigment
called
chlorophyll.
“Chlorophyll, more like
borophyll!”
• https://youtu.be/HrNse
yswKak
• (1:38)
Chloroplast Structure
• Inner membrane
called the thylakoid
membrane.
• Thickened regions
called thylakoids.
A stack of thylakoids is
called a granum.
(Plural – grana)
• Stroma is a liquid
surrounding the
thylakoids.
STOMATA
STOMATA
Stomata are
important for the
exchange of gases
(CO2 & O2) by
diffusion between
the outside air and
intercellular spaces
for respiration
(and also for the
evaporation of water by
transpiration. )
https://youtu.be/pFaBp
VoQD4E (5 min)
PHOTOSYNTHESIS EQUATION:
6 CO2 + 6 H2O + light  C6H12O6 + 6 O2
CHLOROPHYLL
• Chlorophyll- found in plants
• will absorb red, blue, and violet
better than other colors.
• Green light is primarily reflected so
most leaves appear green to us.
CHLOROPHYLL
Two Types of Chlorophyll – each absorb light differently…
Chlorophyll a absorbs light mainly in blue-violet & red regions.
Chlorphyll b absorbs light in the blue and red regions more.
CHLOROPHYLL
• Because light is a form of energy, any
compound that absorbs light also absorbs
the energy in that light.
• When chlorophyll absorbs light much of the
energy is transferred directly to
electrons in the chlorophyll molecule,
raising the energy available in these
electrons.
CHLOROPHYLL
• Electron carriers are seen throughout
Photosynthesis.
• They are compounds that can accept
high-energy electrons and transfer
them along with most of their energy
to another molecule. Examples…
– NADP+
– ADP
NADPH
ATP
Breaking off the Phosphate is
what releases energy from
these molecules:
ATP  ADP + Phosphate + Energy
NADPH  NADH + Phosphate + Energy
2 REACTIONS OF
PHOTOSYNTHESIS
Photosynthesis involves 2 reactions:
1. Light Reaction  makes O2
2. Calvin Cycle  makes C6H12O6
(Also called Light Independent Reaction
and Dark Reaction.)
Light-dependent Reactions
• Electron transport system: sequence of
electron carrier molecules that shuttle
electrons, energy released to make ATP
• Oxygen is made from the light reactions
• Light reactions make ATP and NADPH
• used for Calvin cycle (dark reactions)
Calvin Cycle (“dark” reactions)
• ATP & NADPH generated in light reactions are
used to fuel the reactions in the Calvin Cycle
which take CO2 and break it apart, then
reassemble the carbons into glucose.
• Called carbon fixation: CO2  C6H12O6
Photosynthesis light reactions  ATP & NADPH
 Calvin Cycle  C6H12O6
PHOTOSYNTHESIS VIDEO ~7 MIN
https://youtu.be/KfvYQgT2M-k
PHOTOSYNTHESIS HW: pg 76 #1-5 in Text
Quizlet posted. https://quizlet.com/_66rt1t
PRACTICE: Khan Academy
https://www.khanacademy.org/science/biology/photosynthesis-in-plants/introductionto-stages-of-photosynthesis/e/photosynthesis
Photosynthecizing Animals…
https://youtu.be/AcX2n1rC4W4
Notice how the equation for
photosynthesis relates to the reactions
shown in the diagram below.
6CO2 + 6H2O + Energy
C6H12O6 + 6O2
CELLULAR
RESPIRATION
C6H12O6 + 6O2  6 CO2 + 6 H2O + Energy
CELLULAR RESPIRATION
A car and our bodies are
similar in the fact that the
mitochondria is like an
engine that uses O2 to burn
sugar as fuel.
The exhaust is H2O & CO2 .
CELLULAR RESPIRATION
• Process by which living organisms obtain
energy from the chemical bonds of food.
• The two important ways cells can harvest
energy from food…
1) cellular respiration & 2) fermentation
(aerobic - O2)
(anaerobic – No O2 )
 lots of ATP!
 Less energy made
AEROBIC RESPIRATION
• Aerobic respiration occurs when
oxygen is present.
• Aerobic respiration produces
large amounts of energy (ATP)
ANAEROBIC RESPIRATION
• Anaerobic respiration occurs when
oxygen is NOT present.
• Produces few ATP’s
• Called fermentation.
 discussed last in the slides…
WHAT IS ATP?
Adenosine Triphosphate is a
compound that contains
- 3 high energy phosphate bonds &
is an important source of energy for cells
ATP
CELLULAR RESPIRATION
Cellular Respiration consists of
3 major stages:
• Glycolysis (in the cytosol / cytoplasm)
• Krebs Cycle (mitochondria)
• Electron Transport Chain (mitochondria)
(ETC for short)
2
2
34
1)
GLYCOLYSIS
• The 1st stage of cellular respiration.
• Occurs in the cytoplasm of the cell.
• Occurs in both aerobic & anaerobic
conditions.
• BUT Does NOT require oxygen
GLYCOLSIS:
• glucose turned to 2 molecules of pyruvate
• Gives net gain of
2x
molecules.
GLYCOLYSIS:
glucose  2 pyruvate molecules
+ 2 ATP molecules
2)
KREBS CYCLE
nd
•2 phase of aerobic respiration
• Occurs in the Mitochondria
KREBS CYCLE
The process of Kreb Cycle is essentially:
- removing CO2 carbon dioxide
- getting out energy in the form of
ATP for energy, NADH & FADH (Electron Carriers)
- & then regenerating the cycle.
2
KREBS CYCLE
The process of Kreb Cycle is essentially:
 MAKES 2
 MAKES CO2
s
.
 MAKES NADH & FADH2
(Electron Carriers for energy
for next step 
ETC )
3) ELECTRON TRANSPORT CHAIN
(ETC)
• 3rd stage of cellular respiration
• Reactions in which an electron is
passed from one molecule to
another to produce energy to
make EVEN MORE
!
3) ELECTRON TRANSPORT CHAIN
(ETC)
• The electron carriers (NADH & FADH2 )
move electrons down the chain
along the inner membrane of the
mitochondria.
To Give You an Idea…
– not to be memorized
3) ELECTRON TRANSPORT CHAIN
(ETC)
• As hydrogen ions move across the
channels in the membrane, they
release energy that is used by an
enzyme to make ATP
• H2O Water is formed in this process
...it is a by-product
3) ELECTRON TRANSPORT CHAIN
(ETC)
• The Result  the electron transport chain
produces 32 molecules of
• O2 enters the ETC & absorbs electrons
• H from C6H12O6 & extra O2
make H2O is a by-product
TOTAL - Cellular Respiration
HOW MUCH
is finally produced???
 2 x ATPs
1)
Glycolysis
2)
Krebs Cycle  2 x ATPs
3) Electron Transport Chain  32 x ATPs
TOTAL = 36
s
OVERVIEW
• Glycolysis is anaerobic  no oxygen
• If oxygen is present then …
Krebs cycle & ETC pathway is taken
• If oxygen is NOT present, a different
pathway is taken  fermentation
FERMENTATION - Anaerobic
• No O2 used !
• Fermentation releases energy
from food molecules in the
absence of oxygen.
Aerobic
Anaerobic
2
2
34
The Process of Fermentation
• In Glycolysis 2 pyruvate were made from
glucose
• Pyruvate is then broken down into:
ethyl alcohol or lactic acid
• Only results in 2
molecules
ALCOHOLIC FERMENTATION
• Most common type of fermentation is
yeast cells converting pyruvate into ethyl
alcohol
• The process enables yeast cells to convert
the sugar in dough to ethyl alcohol &
carbon dioxide
Glycolysis:
Fermentation:
FERMENTATION in Bread
• As yeast ferments,
it causes dough to rise &
create the bubbles that
are present in bread
• An example of alcoholic
fermentation of yeast
• As the dough bakes, yeast
cells die and the alcohol
they made evaporates
FERMENTATION
Also used to
make wine, beer,
& ethanol added
to gasoline.
LACTIC ACID FERMENTATION
• Occurs in muscle cells
when they use up all
the available oxygen
Video clip: - 10 seconds https://youtu.be/uyM6Wyg0xPg
• Muscle cells feel
fatigued and sore b/c
lactic acid forms when
oxygen is NOT present
• This goes away in a few
hours.
LACTIC ACID
• Most lactic acid made in muscles
diffuses into bloodstream, then to liver,
where it is converted back to pyruvate,
which enters the
aerobic respiration process…
Kreb’s Cycle &
Electron Transport Chain
LACTIC ACID Products
Yogurt, cheeses,
rye bread, pickles,
sauerkraut, and
olives are lactic
acid products