Transcript Energy and Photosynthesis - Fort Bend ISD / Homepage

Energy and Photosynthesis
S. Burnham
Biology
HHS
Energy in Living Things
 Two Groups of Living Organisms in the
Way they meet their Energy needs:


Autotrophs: plants and other living things that
build organic molecules from inorganic
substances internally (auto-by themselves)
Heterotrophs: organsims that do not make their
own food but depend on autotrophs for their
food directly or indirectly (hetero – different)
How do autotrophs make their
own food?
Photosynthesis
 Almost all of the Energy on the Earth
comes from the Sun and it drives the
chemical reactions that creates all other
forms of energy in life.
 Therefore, most all autotrophs get their
food directly or indirectly from the sun.
Photosynthesis
 The Sun’s energy is trapped in the
organelles of a plant cell called the
CHLOROPLAST, which is a type of
PLASTID.
 It uses the suns energy with the help of
chlorophyll,CO2, AND H2O to produce
glucose and O2 .
Photosynthesis
 Is the process of breaking that Glucose
molecule down and releasing that
stored energy and Oxygen.
 Overall-Photosynthesis-Allows Plants
to take in Light and Carbon dioxideturn it in to Sugar and release Oxygen
into the atmosphere---Yipee.
ATP
 USABLE Energy is stored in a molecule
called ATP.
 ADENOSINE TRI PHOSPHATE
ATP
 THREE PARTS:
Adenine
 Ribose
 3 Phosphate groups
 Its written as A-P-P-P the energy is
between the P’s. When the P bonds
are broken energy is released.

Biochemical Cycle-ATP-ADP
 Those P bonds must be broken before
cells can use the energy stored in ATP.
 An enzyme (a Protein that CUTS stuff)
called ATPase---- -ase means to cut
whatever the word is in front of it…is
sent out to cut the bond between the 2nd
and 3rd Phosphate group
 ADP is formed.
 (If ATP is triphosphate…what is ADP?)
ATP-ADP Cycle continued
 So, then energy is released…and then
ATPase comes along and breaks the P
bond between the 1st and 2nd P group
and you are left with AMP and energy.
 (If ADP is Adenosine Diphosphate- I
wonder what AMP stands for)
ATP-ADP Cycle continued
 The formation of ADP or ATP is the
reverse of its breakdown. It occurs
with the help of an enzyme (protein)
called ATP synthetase….a protein that
builds-not breaks.
Photosynthesis-Chemical
Reactions
 Phostosynthesis:
 Sun Energy+6CO2+6H20 C6H12O6+6O2
 This chemical reaction takes place in
basically two steps: Light and Dark
reactions
Photosynthesis-Chemical
Reactions
 The light reactions-which require light
to form ATP and the Hydrogen carrier
molecule
 The dark reactions- which require no
light to use ATP and Carbon dioxide to
form sugar
The Chloroplast
 Both the Light and Dark reactions take
place in the Chloroplast.
 Organelle
 A number of Chloroplasts in Plant Cells
 Plant cell only
 Structure of Chloroplast:

Thylakoid, lumen, grana, stroma – see page
208
Plant cell and chloroplast
Chlorophyll
 Primary pigment of plants
 Job is to capture sun’s rays
 When sun’s rays…blue and red only
are captured, the green rays are
reflected and thus plants are seen as
green.
Chlorophyll
 When Chlorophyll absorb those waves
their molecules are excited and
electrons jump off ..which is necessary
for photosynthesis.
Carotenoids and Phycobilins
 Beta Carotene… Carrots… and autumn leaves
all have one thing in common:
 ACCESSORY PIGMENTS
 Chlorophyll…cannot do it all with just the red
and blue light of the sun’s rays so the accessory
pigments of carotenoids/xanthophylls-yellow,
orange and browns, and the phycobyllins which
are the red and blues hues…capture the rest of
the sun’s rays and give the rest of the energy to
chlorophyll during photosynthesis.
Light Reactions
 PAY ATTENTION OR YOU WILL GET
LOST….
 Sunlight hits chlorophyll
 Chlorophyll’s electrons get excited and one
escapes….this happens more than once during
photosynthesis
 Two molecules of water are split. Two
hydrogens form ions H+. Then the two
Oxygen ions come together to form Oxygen
gas and are released into the atmosphere.
Two more Molecules
 The Hydrogen Ions that split from the water are picked up
by NADP-to form NADPH—its just a bucket used to pick
up H’s. Now if the H+s build up, the cell becomes like a
magnet and it needs to be balanced out by electrons (e-’s)
They both travel up and down the electron transport chain
creating ENERGY to be used in the next reaction and the
H+s are carried over for the next reaction…IN THE DARK.
 Let me give you the overall equation for Photosynthesis and
you can see just how much we have covered:
 Energy from Sun+6CO2+6H20
C6H12O6 +6O2
 So what have we used so far?
Dark Reactions or the CALVIN
CYCLE
 These are called the Dark reactions because they
do not require sunlight to occur. BUT they do
require the ATP and NADPH from the light dep.
Reactions to occur.
 This time CO2 enters the plant and mixes with the
ATP and NADPH to form a 6 carbon sugar called
GLUCOSE.
 This cycle has to happen 6 times just to get 1
molecule of glucose.
IN REVIEW
 Glucose is the product of Photosynthesis as well as
Oxygen…However, plants store the glucose and release
the oxygen.





So to review
Photosynthesis happens in the chloroplasts.
Light dep. Reactions happen in the thylakoid
Light indep. reactions happen in the stroma
Light dep. Uses light to form ATP, NADPH, split water
and make oxygen gas
 Light indep. Brings in carbon dioxide plus all of the stuff
from light dep. Reactions to make six turns of the
CALVIN cycle to produce glucose.
Cellular Respiration
 If animals and other life forms use a process
that is directly reversed from the
plants…what would its equation look like?
 Energy from Sun+6CO2+6H20 C6H12O6 +6O2
 Or ATP
 CELLULAR RESPIRATION??????
Respiration
 Before food can be used to perform work its
energy must be released in the process of
respiration.
 There are two forms of respiration:
 Aerobic
 Anerobic
Aerobic Respiration
 Basically, how do humans use sugar or food as
chemical energy?
 Please look at the following formula:
 C6H12O6 +6O2
 REACTANTS
6CO2+6H20 + 38 ATP
PRODUCTS
Basically
 Sugar and Oxygen break down and give off
water, Carbon Dioxide, and 38 molecules of
Energy.
 This happens in 3 STAGES
 GLYCOLYSIS
 KREB’s CYCLE
ELECTRON TRANSPORT CHAIN
Review
 Glycolysis which occurs without oxygen and
turns glucose into Pyruvic Acid ( which is a
3-carbon molecule)…takes place in the
cytoplasm of the cell.
 KREB’s CYCLE occurs in the
MITOCHONDRIA and turns pyruvic acid
into citric acid and ATP and Carbon
dioxide.
 And the electron transport chain helps take
the NADH and combine it with O2 to make
water.
The Formation of ATP
 The Electron Transport Chain….
 In the inner membrane of the mitochondria ..it
acts like a giant magnet… the positive parts
of the magnet are the H+ molecules of the
NADH+H and the FADH and H+
molecules…as they move through the
membrane they attract electrons which are
negative particles of the magnet.
The formation of Water and ATP
At the end of this magnet…
 oxygen picks up some Hydrogens and makes a
water molecule.
 Now did you know that the word “electricity”
comes from the movement of electrons…so, as our
electrons in this inner membrane of the
mitochondria are moving with the Hydrogens as a
magnet, they are creating enough energy to help
that enzyme ATP synthetase to create molecules of
ATP and that is why ATP is found in the
mitochondria.
Anerobic Respiration
 Anerobic respiration is the breakdown of
food into energy without the use of oxygen.
 So, if you are not breathing properly, you
will undergo glycolysis-break down of
glucose into pyruvic acid- but the acid will
turn into either ALCOHOL or LACTIC
ACID…which one do animals do?
Fermentation-anerobic respiration
 The breakdown of Pyruvic Acid without the
use of oxygen to form LACTIC ACID or
ALCOHOL
 Fermentation occurs in two forms:
 Lactic Acid –when pyruvic acid is turned into
lactic acid-which pierces muscle cells in
animals
 Alcoholic Fermentation – occurs in some plant
and yeast cells as pyruvic acid is converted into
ethyl alcohol without the use of oxygen
Aerobic Respiration
 Pathways of cellular respiration
require oxygen
 Cellular respiration releases energy by
breaking down glucose and other food
molecules in the presence of oxygen!