Lec 6 : Photosynthesis Flashcards
Consumers
Heterotrophs (Animals)
Get their energy from “eating others”
Heterotrophs
How does heterotrophs make energy?
Through respiration
Formula of heteretrophs (respiration)
C6H12O6+O2 -> 6CO2+ H2O + ATP
Gluclose + oxygen -> Carbon dioxide + water + energy
Produce their own energy (from self)
Autotrophs
making energy & organic molecules from light energy
Autotrophs
Formula for Autotrophs (photosynthesis)
6CO2+ H2O + light energy -> C6H12O6+O2
Carbond dioxide + water + light energy - > Glucose + oxygen
What does it mean to be a plant
Need to;
- collect light energy
- store light energy
- need to get building blocks of atoms
- produce all organic molecules
Building blocks of atoms from the environment needed to get by plants
- C,H,O,N,P,K,S,Mg
Why plants need to produce all organic molecules?
For growth
Organic molecules needed to be produce by plant
- Carbohydrate
- Protein
- Lipids
- Nucleic acids
Plant structures for obtaining raw materials
- Leaves
- Stomates
- Roots
the structure for Sunlight , solar collectors
Leaves
the structure for CO2, gas exchange
Stomates
the struture for H2O uptake
roots
the structure for nutrients uptake
Roots
Nutrients uptake from roots
- N, P, K, S, Mg, Fe
contain chlorophyll
Chloroplast
Components of Chloroplast
- Stroma
- Thylakoid sacs
- Grana stacks
fluid-filled interior
Stroma
pouch-like sacs
Thylakoid sacs
stacks of thylakoid discs
Grana stacks
Components of Thylakoid membrane
- Chlorophyll molecules
- ETC
- ATP synthase
the membrane located inside the chloroplast
Thylakoid Membrane
Where does photosynthesis happen?
Choloroplast
Types of Photosynthesis reactions
- Light reactions
- Calvin cycle
Also known as light-independent reaction?
Calvin cycle
Where does ETC respiration happens?
- Mitochondria, uses electron carrier NADH
Where does ETC photosynthesis happens?
- Chloroplasts, uses electron carrier NADPH
transfer chemical energy from food molecules into chemical energy of ATP
Mitochondria
transform light energy into chemical energy of ATP
Chloroplasts
- convert solar energy to chemical energy
- ATP & NADPH
energy conversion reactions
uses chemical energy (ATP & NADPH) to reduce CO2 & synthesize C6H12O6
Sugar building reactions
- embedded in thylakoid membrane
- arranged in Photosystem
- Structure-function relationship
Chlorophyll and other pigments
It is the collection of molecules
Photosystem
Photosynthesis gets energy by absorbing wavelengths of light
Light: Absorption spectra
absorbs best in red & blue wavelengths & least in green
Chlorophyll a
By definition it is the other pigments with different structures help absorb light of different wavelengths
Accessory pigments
Examples of accessory pigments
- Chlorophyll b
- Carotenoids
- Xantophyll
Absorbs light at slightly different wavelengths than chlorophyll a
Chlorphyll b
Absorb blue-green wavelengths
Carotenoids
- Absorb blue or blue-green light
- transfer the energy to chlorophylls
Xanthophylls
2 Photosystem in Thylakoid membrane
- Photosystem II
- Photosystem I
absorbs 680nm
wavelength red light
- Chlorophyll a
Photosystem II
absorbs 700nm wavelength red light
- chlorophyll b
Photosystem I
Uses light energy to produce ATP and NADPH
- ETC
Where do excited electron passes from chlorophyll
Primary electron acceptor of PS II
enzyme exctract electrons from ___ and supplies them to chlorophyll
H2O
What happens to oxygen atoms after being split from H2O
Oxygen atoms combineto form O2
Types of Phosphorylation
- Noncyclic Photophosphorylation
- Cyclic Photophosphorylation
- Happens in PS II and I
- Light reactions elevate electron in 2 steps
Noncyclic phosphorylation
The 2 steps in nonclyclic photophosphorylation
- PS II- generates energy as ATP
- PS I - generates reducing power as NADPH
Occurs only in Photosystem I
Cyclic Photophosphorylation
- Happens in the Stroma
- does not need light
Calvin cycle
product needed by calvin cycle to drive synthesis reactions
Products from Light reaction, ATP and NADPH
Stages of calvin cycle
- Carbon fixation
- reduction
- Regeneration of RuBP
Final product of calvin cycle
Glucose
How many terms of calvin cycle for 1 glucose?
6 turns
end product of Calvin cycle
Glyceraldehyde-3-P
Important intermediate
Glyceraldehyde-3-P
- Enzyme which fixes carbon from air
- the most important enzyme in the world!
Rubisco
RUBISCO full name
Ribulose biphosphate carboxylase
3 turns of calvin cycle =?
1 G3P
3 CO2 ->?
1 G3P (3C)
What happened to the left over ATP from light reactions
used elsewhere by the cell
for transporting water
Xylem
for sugar and nutrients
Phloem
structure that control water from leaves
Stroma
What happens when stoma opens?
Gains H2O
What happens when stoma closes
Lose H2O
- pairs of epidermal cells that control gas diffusion
- regulates the opening and closure of stomatal pores
Guard Cells
Closed stomates leads to
O2 buils up -> from light reactions
CO2 -> in calvin cycle
Can drive or hinder photosynthesis
RUBISCO
2 main types of reactions catalyzed by RUBISCO
- Carbon fixation (Carboxylase)
- Photorespiration (Oxygenase)
- Bonds Carbon to RuBP
- Building sugar
Carbon Fixation enzyme
- Rubisco bonds O to RuBP
- Oxidation or RuBP
- breadown of sugar
Photorespiration
consumes resources without producing sugars.
Photorespiration
optimal functioning of Rubisco under ideal conditions when CO₂ is available. Successful sugar production and energy storage.
Photosynthesis
Types of reducing photorespiration
- C4 Photosynthesis
- CAM photosynthesis
physically separate carbon fixation from actual Calvin cycle
- uses different enzyme to capture CO2
C4 photosynthesis
Different enzyme that captures CO2 in C4
PEP carboxylase
-Separated by time of day
-Carbon fixation during night
CAM photosynthesis
CAM stands for?
Crassulacean Acid Metabolism
Example of plants that employ C4 photosynthesis
Sugar cane
Corn
other grasses
higher affinity for CO2 than O2
- regenerates CO2 in inner cells for Rubisco
PEP carboxylase enzyme
Separate reactions in different cells
- Light reactions
- Carbon fixation
- Calvin cycle
What happens on outer cells of C4 photosynthesis
- Light reaction & carbon fixation
- Pumps CO2 to inner cells
- Keeps O2 away from inner cells
What happens on inner cells of C4 photosynthesis
Calvin cycle, glucose veins
CAM during night
- Open stomates & fix carbon in storage compounds
CAM during day
- close stomates
- release CO2 from storage to calvin cycle
separate 2 steps of C fixation anatomically
in 2 different cells
C4 plants
separate 2 steps of C fixation temporally at 2 different times
CAM Plants
Why the C3 problem?
- possible evolutionary baggage
