PHOTOSYNTHESIS &
CELLULAR RESPIRATION

• 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 – e.g. plants

What is Photosynthesis?
The process of photosynthesis is a
chemical reaction.
It is the MOST IMPORTANT chemical reaction on our planet .

Photosynthesis Described:
• 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, CO
2
, and H
2
O
• 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
tml

What do plants need for photosynthesis?

PHOTOSYNTHESIS EQUATION:
6 CO
2
+ 6 H
2
O + light  C
6
H
12
O
6
+ 6 O
2

ENERGY IN A
CELL!!
• Your body requires energy in order to function…from your heart beating to intense workouts.
• Energy is essential to LIFE!!
• HOW? WHAT?

• 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 PO
4
 2 x PO
4

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

Chloroplast  Chlorophyll
These chloroplasts contain the green pigment called chlorophyll .

“Chlorophyll, more like borophyll!”
• https://youtu.be/HrNseyswKak
•
(1:38 min)
• So Billy isn’t into photosynthesis, but he’s a loser …

• 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 are important for the
exchange of gases
(CO
2
& O
2
) 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 CO
2
+ 6 H
2
O + light  C
6
H
12
O
6
+ 6 O
2

• 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.

Slide won’t be on test
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.

• 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.

• 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 for cell use.
ATP  ADP + Phosphate + Energy
NADPH  NADH + Phosphate + Energy

2 REACTIONS OF
PHOTOSYNTHESIS
Photosynthesis involves 2 reactions:
1. Light Reaction  makes O
2
2. Calvin Cycle  makes C
6
H
12
O
6
( Calvin Cycle is also called Dark Reactions or the Light Independent Reactions)

Light Dependent
Reactions
MAKES:
O
2
NADPH and ATP

• Electron transport system:
Sequence of electron carrier molecules that shuttle electrons which release energy to make
ATP & NADPH
• Light reactions make Oxygen
• Light reactions make ATP & NADPH
• ATP & NADPH used in Calvin cycle (dark reactions)

in molecules carry
to different molecules which allow for
& to be made.

Calvin Cycle (“dark” reactions)
• ATP & NADPH generated in light reactions are used to fuel the reactions in the Calvin Cycle which take CO
2 and break it apart, then reassemble the carbons into glucose.
• Called carbon fixation: CO
2
 C
6
H
12
O
6
Photosynthesis light reactions

ATP & NADPH
 Calvin Cycle  C
6
H
12
O
6

Light Dependent
Reactions
CALVIN CYCLE:
Light Independent
Reactions

Light Dependent Reactions :
Calvin Cycle: Light Independent

Notice how the equation for photosynthesis relates to the reactions shown in the diagram below.
6CO
2
+ 6H
2
O + Energy C
6
H
12
O
6
+ 6O
2

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