1 Photosynthesis & Cellular Respiration How plants get
Energy Slide 2 2 Photosynthesis Photosynthesis - the process in
which green plants use the energy of sunlight to convert water and
carbon dioxide into high-energy carbohydrates and oxygen Slide 3
Photosynthesis There are two main steps in Photosynthesis. Light
reaction Calvin Cycle 3 Slide 4 4 The Photosynthesis Equation The
equation for photosynthesis is: 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2
carbon dioxide + water sugars + oxygen Light Slide 5 5 Light Energy
Light is a form of energy chlorophyll absorbs light. The energy is
transferred directly to electrons in the chlorophyll molecule
raising the energy levels of these electrons. high-energy electrons
are what make photosynthesis work Slide 6 6 Inside a Chloroplast
photosynthesis takes place inside chloroplasts. Plant Plant cells
Chloroplast Slide 7 7 Inside a Chloroplast Chloroplasts contain
thylakoidssaclike photosynthetic membranes. Thylakoids are arranged
in stacks known as grana. A singular stack is called a granum.
Stroma space outside of the thylakoids Granum Chloroplast Stroma
Single thylakoid Slide 8 8 Light and Pigments photosynthesis
requires chlorophyll pigments - light-absorbing molecules that
gather the sun's energy The main pigment in plants is chlorophyll.
There are two main types of chlorophyll: chlorophyll a chlorophyll
b Slide 9 9 Light and Pigments Chlorophyll does not absorb light in
the green region of the spectrum. Green light is reflected by
leaves, which is why plants look green. Estimated Absorption (%)
100 80 60 40 20 0 400 450 500 550 600 650 700 750 Chlorophyll b
Chlorophyll a Wavelength (nm) Slide 10 10 Inside a Chloroplast
Proteins in the thylakoid membrane organize chlorophyll and other
pigments into clusters called photosystems, which are the
light-collecting units of the chloroplast in the thylakoid
membrane. Chloroplast Photosystems Slide 11 Light Reaction Sep 1
Light energy forces electrons in the chlorophyll a molecules to
become excited. This means that have more energy than usual. 11
Slide 12 Light Reaction Step 2 The electrons leave the chlorophyll
a molecule and are accepted by the primary electron acceptor. This
begins the start of the electron transport chain and activates the
Hydrogen pumps. Hydrogen is pumped into the Thylakoid. 12 Slide 13
Light Reaction However, certain electrons are donated to NADP
(cousin to NAD) instead of heading down the chain. NADP takes and
electron and a Hydrogen. 13 Slide 14 Light Reaction SO. Where did
the electrons that were lost come from? Water! An enzyme in the
Thylakoid breaks two water molecules down into four hydrogen ions
(H + ), their 4 electrons and O 2. 14 Slide 15 Light Reaction An
enzyme in the Thylakoid breaks two water molecules down into four
hydrogen ions (H + ), their 4 electrons and O 2. This is why plants
dont need to take in O 2. They make it by splitting water! 15 Slide
16 Calvin Cycle Now that the plant has made energy it is going to
use that energy to make a simple sugar. But WE NEED CARBON to make
sugar. Plants take in CO 2 and turn it into sugar! 16 Slide 17
Calvin Cycle Step 1 We need three CO 2 to get started. We start by
hooking the carbon from each CO 2 up to a 5 carbon chain with
phosphates at each end. This now make a 6 carbon chain with
phosphates at each end. We create three of these at a time. 17
Slide 18 Calvin Cycle Step 2 Each carbon chain breaks in half. You
now have 6 three carbon chains with a phosphate at each end. 18
Slide 19 Calvin Cycle Step 3 The ATP and NADPH created in
photosynthesis gives a phosphate and a hydrogen to each of the
three carbon chains. There is now a phosphate attached at each end.
19 Slide 20 Calvin Cycle Step 3 Cont. The three carbon chains now
give off a phosphate. Yes we gained 6 phosphates to lose 6
phosphates. CRAZY! But this give the three carbon chains the energy
needed to rearrange slightly. 20 Slide 21 Calvin Cycle Step 4 One
of the new three carbon chains leaves to become a carbohydrate. We
have made a molecule of sugar!!! The rest of the 3 carbon chains
use 3 ATPs to recombine into the 5 carbon chains. 21 Slide 22 22
Inside a Chloroplast Chloroplast Light H2OH2O O2O2 CO 2 Sugars NADP
+ ADP + P Calvin Cycle Light- dependent reactions Calvin cycle
Slide 23 23 Photosynthesis Reactions light-independent reactions
(Calvin cycle) takes place in the stroma ATP and NADPH not stable
enough to store the energy they carry for more than a few minutes
uses ATP and NADPH energy to build high-energy sugars for long term
storage Slide 24 24 Factors Affecting Photosynthesis Many factors
affect the rate of photosynthesis, including: Water Temperature
Intensity of light Slide 25 25 Comparing Photosynthesis and
Cellular Respiration The energy flows in photosynthesis and
cellular respiration take place in opposite directions. Slide 26 26
Comparing Photosynthesis and Cellular Respiration On a global
level, photosynthesis and cellular respiration are also opposites.
Photosynthesis removes carbon dioxide from the atmosphere and
cellular respiration puts it back. Photosynthesis releases oxygen
into the atmosphere and cellular respiration uses that oxygen to
release energy from food.
