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Photosynthesis
Ms. Lowrie
Biology 11
Did you know???
Photosynthesis produces
160 billion kg
of carbohydrates each year!!!
That’s over 352
trillion lbs !
Photosynthesis Simplified
Vein
Chloroplast
Mesophyll
Inner
membrane
Outer
membrane
Stomata
Leaf cross section
Mesophyll cell
Grana
Structure of a Leaf
Stroma
Thylakoid
Thylakoid
space
Plant Pigments

Chlorophyll A, B and C


Captures sunlight
Other Pigments:


Beta carotene
/carotinoid
Xanthophyll
Chloroplast:
Site of
Photosynthesis
grana (plural)
Stack of
thylakoids
Contains
chlorophyll
- Space around thylakoids
- No chlorophyll
Did you know?
Each square
Light
Reflected
light
millimeter (mm2)
of a leaf contains
~500,000
chloroplasts!
Absorbed
light
Transmitted
light
Chloroplast
What is photosynthesis?




Process by which plants make food
"photo" = light
"synthesis" = making/putting together
Involves over 100
chemical reactions!
Why do plants need ‘food’?

Sugars used for life processes



Growing
Reproducing
Excess is converted to starch


Stored in plant parts
May be used as food by animals and
humans
How is it done?

Water & carbon dioxide (inorganic)

Light energy

Glucose

An organic carbohydrate
Figure 2 (pg 59)
Photosynthesis

Summary Equation:
Light energy
Carbon
dioxide
Water
Reactants
(starting materials)
Glucose
Oxygen
Products
(end materials)
Water
Two Phases
Light Reactions


Dark Reactions
Photophosphorylation

Light energy used to
drive reactions

Calvin Cycle OR
Carbon Fixation
Chemical energy
stored in glucose
Light Reactions – Name?

a.k.a. Photophosphorylation

Uses sunlight

Occurs in grana


Contains chlorophyll
Addition of a phosphate group to ADP
Light Reactions
Light energy absorbed by chlorophyll

“Energized”


Causes the following …
1. ADP undergoes phosphorylation
•
Add a phosphate group = becomes ATP
Light Reactions
2. Water is split into:
Hydrogen:
•
• Picked up by NADP+ (a hydrogen receptor)
• Creates NADPH
Oxygen:
•
•
Water
Released to atmosphere
H2
+
Oxygen
What is NADP+???

A hydrogen CARRIER

Transports hydrogen to next phase
Think:
Hydrogen can’t be alone in
the dark …
so it rides the “NADP bus”!
Light Reactions –
Overview
Calvin Cycle – Name?


a.k.a. Dark Reactions (light
independent) OR Carbon Fixation
Occurs in stroma


No chlorophyll
Creates glucose

Carbon molecules attached together
Calvin Cycle

Uses:


CO2 from
atmosphere
NADPH & ATP from
light reactions
Calvin Cycle

ATP & NADPH convert CO2
into PGAL


2 PGAL = 1 glucose (C6H12O6)
H2O is also created

Released to the atmosphere
What is PGAL???

Used to make
many organic
compounds



Carbohydrates
Lipids
Amino acid
Calvin Cycle –
Overview
Three CO2
ADP +
ATP
Calvin
cycle
NADP
PGAL
Two rounds = 2 PGALs

Making sugar from CO2
Glucose
Calvin Cycle –
Overview
Photosynthesis

Summary Equation:
Light energy
Carbon
dioxide
Water
Glucose
Oxygen
Water
Balanced Equation
– Note the Water!
Light
energy
Carbon
dioxide
Water
Photosynthesis
Glucose
Oxygen
gas
Any questions so far
Task

Use notes & pages 58 – 60

Answer:

#1, 2 & 4
(page 60)
#1 – Photosynthesis

“Photo” = light
“Synthesis” = to make

Photosynthesis


Making glucose using light energy
#2 – Chlorophyll



Contained in thylakoids in chloroplasts
Traps light energy
Helps convert energy into
carbohydrates
#4 – Energy Gain

Produces carbohydrate/glucose


High energy compound
Used by organisms as energy source
Complete Concept Map
Terms:
ATP, carbon dioxide,
glucose, NADPH, oxygen, water
Water
Light
Reactions
Carbon Dioxide
ATP
NADPH
Oxygen
ADP + P
NADP+
Calvin
Cycle
(Dark)
Glucose