Upload
ihmcbiology1213
View
1.600
Download
0
Tags:
Embed Size (px)
Citation preview
PHOTOSYNTHESISPhotos (light) + synthesis (put together or manufature)
Harness energy from the sun through chloroplasts
Then store the energy converted into carbohydrate molecules in the cell wall and vacuoles
Undergo PHOTOSYNTHESIS - the process by which plants convert energy from the sun to provide energy for themselves and almost all life forms
Plants…
Photosynthesis…
Allows plants to create organic molecules they use as fuel.
Basis of all food chains Occurs mostly in LEAVES, which
are the main organs for photosynthesis
Photosynthesis
Chloroplasts Organelles specialized for
photosynthesis Have two membranes
surrounding the liquid in its interior called the STROMA
Inside the inner membrane are series of flattened interconnected sacs called GRANA
Each of these flattened sacs is called a THYLAKOID
A closer look at the thylakoid will reveal its membrane separating it with the stroma or the liquid part of the chloroplast – it is in this membrane that light trapping molecules are located
LIGHT DEPENDENT REACTION of photosynthesis – aka PHOTOCHEMICAL STAGE occurs in thylakoid membrane (because of the
light trapping molecules) LIGHT INDEPENDENT REACTION of
photosynthesis – aka DARK REACTION/CALVIN CYCLE occurs in the stroma
Chloroplasts (cont’d)
Photosynthesis LIGHT and WATER are needed to
perform this process (sun heats water in plant leaves)
Chlorophyll in chloroplasts (scattered throughout each plant cell), absorb energy in the form of light from the sun
Plants take in carbon dioxide – obtained through tiny openings known as stomata
Plants absorb water and nutrients dissolved in the soil through their root system and its network of conducting cells called xylem vessels
ATP - Adenosine TriphosphateADP - Adenosine DiphosphateNADPH- Nicotinamide Adenine
Dinucleotide Phosphate(Hydrogen acceptor)
Reactant - substances that undergo chemical reaction
Product - outcome of the reaction
Words to Know: Photosynthesis
Photosynthesis Equation
Photosynthesis Is the reverse of the reactions
that occur in animals during cellular respiration
CELLULAR RESPIRATION – the splitting apart of glucose by water to produce carbon dioxide and energy
PHOTOSYNTHESIS – the splitting apart of water by energy to produce glucose from carbon dioxide, with oxygen given off
Occurs in thylakoid membrane Energy from the sun (light energy) is
absorbed by the chlorophyll and then converted into chemical energy.
Light energy is needed to split the water molecules into hydrogen and oxygen.
Oxygen is released as a waste product. These reactions are called
photochemical light reactions because they require light to occur.
Two Stages of Photosynthesis: Light Dependent Stage
Light Dependent Stage Involves two groups of light
absorbing molecules found in the thylakoid membranes: Photosystem I and Photosystem II
Both capture solar energy to energize electrons.
Both cooperate in the light reactions.
Photosystem II functions first.
When excited by light from the sun, chlorophylls release energized electrons. The photosystems transfer the energized electrons to electron transport chains.
Electrons in Photosystems II that were shuttled to Photosystem I provide energy to make ATP.
Electrons from Photosystem I reduce the coenzyme NADP+ (NAD = Nicotinamide adenine dinucleotide) to NADPH.
Photosystem II regains electrons by splitting water and releasing oxygen.
Light Dependent Stage
Steps: Light Dependent Reaction
Light energy
Chlorophyll A (becomes an energy carrier)
that becomes Energized chlorophyll
split
water
ATP
ADP
OH2
phosphate
combine
into
that are trapped by
NADP
NADPH2
(H acceptor)forms
to be used for dark reaction
withto form
to be used for dark reaction
1
2
3
4 4
5
7
6
5 is released56
is absorbed by
supplies energy to
Light Independent Stage Second stage of photosynthesis Formation of glucose from
carbon dioxide doesn’t directly require light.
Aka Calvin Cycle for Melvin Calvin
Occurs in stroma Consists of cyclical series of
reactions that assembles sugar molecules from carbon dioxide and the energy-containing products of the light-dependent reaction with the aid of enzymes.
In the stroma, the enzymes combine carbon dioxide with ribulose phosphate (RuBP) which is a five-carbon sugar and produce glyceraldehydes-three-phosphate (G-3-P), an energy-rich, three-carbon sugar formed by the splitting of sugar.
G-3-P can be used by a plant cell to make glucose and other organic molecules.
The glucose produced during photosynthesis is used by plans as fuel for cellular respiration, and starting material to make cellulose.
Excess sugar is combined with a large carbohydrate molecule and stored as starch in their roots, tubers or fruits.
Light Independent Stage
Steps : Light Independent Reaction
6 CO2 molecules
combines with
RuDP (CO2 acceptor)
forms
6-C sugar (unstable sugar)
splits to form2 molecules of PGA (3- C compound)
combines with2 H (from light reaction (NADPH))
forms
RuDP
H2O2 molecules of PGAL
by-product used in light reaction
is converted into
Glucose to be reusedto combine with CO2
1
2
5
3
4
66
7
-called:Biochemical Pathway
Comparison of the two
Reaction Light DarkSite of Occurence
Thylakoid-grana
stroma
Initial Requirement (Reactants)
Light Energy, water, and chlorophyll A
ATP, NADPH, and CO2,
End Product ATP, NADPH, Oxygen
Glucose, water, NADP, ADP and inorganic phosphate
Both reactions thus form a cycle in which the reactants: water and carbon dioxide produce oxygen and sugar (glucose) as products
Plants need: Carbon dioxide Water Oxygen (for cellular respiration) Hydrogen Nitrogen Potassium Phosphorus Calcium Magnesium Sulfur Boron Copper Iron Molybdenum Zinc