C17 - Photosynthesis Flashcards
Why do you living organisms need energy
Active transport
DNA replication
Cell division
Protein synthesis
What is the enzyme that hydrolyses ATP
ATPase
What is the enzyme that synthesises ATP and what are its reactants
ATP synthase, ADP and Pi
Why is ATP a good source of energy
Small quantities of energy – efficient
Easily hydrolysed – single step reaction
Small and soluble – easily transported
Give two ways chloroplasts are adapted for function
Network of membranes – high surface area – max absorption of light
Contain photosynthetic pigment to absorb light
What are the flattened membraneous sacks in chloroplasts called and what are their stacks called
Thylakoids
Grana
What are lamellae
Membranes that join Grana
What is the fluid in chloroplasts called
Stroma
What is chlorophyll and what is its function
Photosynthetic pigment
Absorbs specific wavelengths of light
Absorbs red and blue, reflects green
name one primary and one accessory photosynthetic pigment and where they are located
Primary – chlorophyll a in reaction centre
Secondary chlorophyll b in thylakoid membrane
What is the role of accessory pigments
Absorb maximum light by absorbing a range of colours
What is the difference between photosystem i and photosystem II in the light dependent reaction
Photosystem I I – lower energy level, first photosystem – noncyclic phosphorylation
Photosystem I - second, higher energy level
What are the three steps in the light dependent reaction
Photoionisation of chlorophyll
Synthesis of ATP
Photolysis of water
What happens in the photoionisation of Chlorophyll
PSII absorbs light energy
Energy causes electrons to become excited, with sufficient energy they leave
High energy electrons pass along electron transport chain
Energy released used to pump H+ ions across the thylakoids membrane
How is ATP is synthesised in the light dependent reaction
Chemiosmosis causes flow with H+ ions across thylakoid membrane
Ions cause a conformational change
ATP synthase synthesise ATP from ADP and PI
Where do the electrons to replace those lost in PS1 come from
End of electron transport chain from PS I I
Where do electrons come from to replace those lost in psII
Photolysis of water
Where do electrons go after being passed down PSI transport chain
Combined with H+ and NADP to make NADPH
What happens in the photolysis of water
Water split into H+, e- and O2 using energy from sun
Describe the process of cyclic phosphorylation
Energy from the Sun absorbed by psi
Electrons excited, passed along electron transport chain
Given back to psi
Energy released used for chemiosmosis and synthesis of ATP
What word describes the loss of electrons from chlorophyll when A light shines on it
Photoionisation
What stages is the light independent stage of photosynthesis made of
Calvin cycle
One – CO2 fixation
Two – reduction of GP
Three – regeneration of RuBP
What happens in CO2 fixation in the Calvin cycle
CO2 enters
RuBP (5C) fixes to C in CO2
Carboxylation reaction
Catalysed by RuBP
What happens during reduction of GP in the Calvin cycle
GP to TP
Uses energy from ATP—> ADP +Pi
Uses H+ from NADPH—> NADP
What happens during the regeneration of RuBP in Calvin cycle
TP (6C) to RuBP (5C) +C
C goes to forming organic molecules (eg. Glucose)
Uses energy from ATP—> ADP +Pi
What are the uses of glucose
Substrate for aerobic respiration Cellulose production Store amylase and amylopectin Make sucrose Stored as lipids Make amino acids and proteins Synthesis of nucleic acids
What are the three factors that affect the rate of photosynthesis
Light intensity
Concentration of CO2
Temperature
How does light intensity affect the rate of photosynthesis
Needed for ATP and NADPH production in light dependent reaction
How does the concentration of CO2 affect the rate of photosynthesis
Needed for carbon fixation in Calvin cycle
How does temperature affect the rate of photosynthesis
Affects rate of enzyme controlled reactions (e.g. carbon fixation and RuBP)
However too hot and will denature
Is water a factor that will affect the rate of photosynthesis
No.
Although water is required it is never considered a limiting factor because the stomata will have closed so no CO2 will be able to enter
How will reducing light intensity affect the concentration of the products in the Calvin cycle
Increased GP
Reduced RuBP and TP (ATP needed for their synthesis coming from LDR)
