Photosynthesis Kerensa Flashcards
Define photosynthesis
Process in which light energy is used to make glucose from water and CO2
What’s the chemical equation for photosynthesis?
6CO2 +6H2O + Light energy > C6H12O6 + 6O2
Add 6 to balance equation.
Basically converting light energy to chemical energy.
What is respiration?
Release of stored energy from glucose. Giving you CO2 + H2O
What are the two types of respiration?
Aerobic- With O2
Anaerobic- Without O2
What’s the chemical equation fro aerobic respiration?
Glucose + Oxygen > Carbon dioxode + Water + Chemical energy.
C6H12O6 + 6O2 > 6CO2 + 6H2O + Chemical energy.
Add sixes to balance equation.
What’s the equation for Anaerobic respiration in different organisms?
Plants and Yeast = Glucose > Ethanol + Energy
Humans = Glucose > Lactic acid + Energy
What does ATP stand for?
Adenosine triphosphate.
Where does ATP carry energy and in what form?
Carries energy in phosphate bonds as chemical energy.
Why is ATP good for releasing energy?
- Can reduce other molecules by making them more reactive.
- Small and soluble.
- Trapped in cell.
- Releases short bursts of energy.
- Easy to break down.
- Unstable molecule so it can be quickly remade.
Define Metabollic Pathway.
Series of small reactions controlled by enzymes. (How photosynthesis works)
Define Phosphorylation.
Adding phosphates to a molecule. (Happens in everything).
Define Photophosphorylation.
Using light to add phosphates to molecules.
Define Photolysis
Splitting of molecules using light energy.
Define Hydrolysis.
Splitting of molecules using water.
Define Photoionisation.
Using Light energy to excite electrons in an atom giving them more energy and causing them to be released from PS11.
Define Decarboxylation.
Removal of CO2
Define dehydrogenation.
Removal of hydrogen (H2)
What is a Redox reaction? And what is the rule with them?
Oxidation and Reduction.
(Red) – (Ox)
You can’t have one without the other.
Define Oxidation and Reduction using OILRIG.
Oxidation
Is
Loss of electrons
Reduction
Is
Gain of electrons
What is a Co-enzyme?
Molecule that aids the function of an enzyme.
What do Co-enzymes transfer?
A chemical group between enzymes.
What co-enzyme is used in photosynthesis? And what does it transfer?
The co-enzyme in photosythesis is NADP.
It transfers Hydrogen protons.
What are the co-enzymes in respiration? And what do they transfer?
NAD transfers hydrogen protons.
FAD transfers hydrogen protons.
Co-enzyme A transfers Acetate
What’s the structure of a chloroplast and what do they do?
Thylakoid - Fluid filled sac
Stroma - Gel with enzymes , sugars ect.
Starch grains - Stores CO2
Lamellae - Has a thylakoid membrane, joins grana
Grana - plural for granum
Inner membrane - Holds together
Outer membrane - Protection.
What photosynthetic pigments are in thylakoid membranes? And define them.
- Chlorophyll A
- Chlorophyll B
- Carotene
They are coloured substances that absorb light energy.
What do photosynthetic pigments attach to? And what does this form?
Photosynthetic pigments attach to proteins and form Photosystems.
Photosynthetic pigments + protein = Photosystems
What are the two photosystems in photosynthesis? And what are the wavelengths of light they recieve?
- PS1 (write I) - Wavelength of light they recieve 700nm.
- PS2 (write II) - Wavelength of light they recieve 680nm.
What are the two main reactions in photosynthesis?
- Light dependant reaction
- Light independant reaction.
What happens in the light dependant reaction? And where does it occur?
Occurs in the Thylakoid membrane.
- Excites electrons
- Electrons released
- Chlorophyll has been photoionised
- You get ADP+Pi > ATP, NADP+H > Reduced NADP and water > 2H+ and 1/2 O2
*
What’s the first stage of photosynthesis?
Light energy is absorbed by chlorophyll
- Light energy absorbed by PSII
- Excites electrons in chlorophyll
- Electrons move to a higher energy level
- Due to higher energy they are released from the chlorophyll
- They move down an electron transfer chain to PSI via electron carrier.
What is the second stage of photosynthesis?
Replacing Excited electrons
- Excited electrons that leave PSII must be replaced.
- They are replaced by photolysis
- Light energy splits water in PSII into 2H+ and 1/2 O2 plus electrons
This is really just to tell you that oxygen comes into the photosynthesis equation because its created during photolysis as 1/2 O2
What’s the third stage of photosynthesis?
Transport of Hydrogen
- Excited electrons that left PSII and went to PSI down the electron transport chain are losing energy.
- Energy is lost as its being used to transport H+ from the stroma into the thylakoid, this creates a high concentration of H+ in the thylakoid. This forms a proton gradient. (Gradient because low conc.>high conc.)
- The hydrogen atoms (protons) move down their conc. gradient through facilitated diffusion by ATP synthase.
- Movement of H+ down ATP synthase gives energy to power ATP synthase, allowing it to catalyse ADP + pi > ATP.
What is the fourth stage of photosynthesis?
- Light energy is absorbed by PSI
- This excites electrons to an even higher energy level than PSII
- Electrons are transferred to NADP in the stroma along with a proton from the stroma. This forms reduced NADP.
What is photosynthesis steps 1-4 called?
Process called Non-cyclic Photophosphorylation.
True of false: Cyclic phosphorylation is in the light-dependant reaction.
True.
Why is Cyclic Phosphorylation different to Non-Cyclic phosphorylation?
Cyclic Phosphorylation only produces ATP and only uses PSI.
Why is Cyclic-phosphorylation called Cylic?
Electrons from the chlorophyll aren’t passed onto NADP but recycled in PSI.
What happens in Cyclic-phosphorylation?
Electron uses energy to get H+ across, then returns to PSI to get energy again.
Define Chemiosmosis.
‘Chemi’ as it uses electrons.
Process of electrons flowing down the electron transport chain and creating a proton gradient across the thylakoid membrane. To drive ATP synthesis.
What are the three main factors about the Light Independant reaction?
- Takes place in the Stroma
- Doesn’t need light
- Needs products of light dependant reaction. ATP and reduced NADP.
Whats another name for the Light Independant reaction?
The Calvin cycle.
What’s the first process of the Light Independant reaction?
- CO2 enters leaf through the stomata, and diffuses into stroma of chloroplast.
- CO2 combines with the ribulose biphosphate (RuBP) (5 Carbon compound) which is then catalysed by Rubisco.
- Adding CO2 to 5 Carbon compound makes an unstable 6 Carbon compound. So it quickly breaks into a 2x Glycerate, 3 - Phosphate molecule. (3 Carbon compound).
What’s the second process of the Light Independant reaction?
- Reduction of 2x glycerate, -3 Phosphate molecule to Triose Phosphate (3 Carbon) (TP)
- 2 molecules of ATP > ADP + Pi which provides energy for the reaction.
- 2 molecules of reduced NADP > NADP which provides H+ ions.
- After hydrolysis of ATP and catalysing of ATP Hydrolase and the breakdown of reduced NADP. Energy from electrons, and the hydrogen ions are used to rearrange 2x Glycerate,-3 Phosphate molecule to triose phosphate.
What’s the third process of the Light Independant reaction?
- Ribulose biphosphate is regenerated.
- 5 out of 6 triose phosphate molecules produced in the cycle are used to regenerate ribulose biphosphate, as it’s a 5 carbon compound.
- ATP > ADP+ Pi Provides the energy for this.
- ( Just a side note mention enzymes such as ATP Hydrolase in exam question as these may get you extra marks).
Kerensa’s teachings are more simplified but keep them in mind as they also get you marks.
Where does the energy from ATP come from when ATP is hyrdolysed/catalysed by ATP hydrolase?
Energy comes from breaking of phosphate bonds.
What can carbohydrates be formed by?
Hexose sugars e.g. glucose are formed by 2 triose phosphate molecules.
Larger carbs such as starch and cellulose are formed by joining hexose sugars together.
What are lipids formed by?
Glycerol - Made of triose phosphate.
Fatty acids - made from glycerate 3 - Phosphate.
What can some amino acids be made from?
Glycerate 3 - phosphate
How many turns of the Calvin cycle does it take to produce 6 molecules of Triose Phosphate?
3 turns of Calvin cycle as it produces 3 CO2 molecules.
True or false: For every 3 turns of the Calvin cycle, 1/6 Triose phosphate molecules go on to assist cell processes.
True.
Glucose needs 6 turns of the calvin cycle to be made. Why?
Glucose is made of two triosphosphate molecules (two 3 carbon compunds). And as 1/6 Triosphosphate molecules can go on to make glucose every 3 turns. Then 6 turns is needed for two 3 carbon molecules of TP to make a 6 carbon molecule fo glucose.
For six turns of the Calvin cycle how many ATP molecules and Reduced NADP molecules are needed? And why? And where do they come from?
For six turns,
18 ATP molecules are needed as theres 3 molecules needed per turn.
12 Reduced NADP molecules are needed as 2 are needed per turn.
ATP and Reduced NADP come from Light dependant reaction.
What is the purpose of Glycolysis?
Make pyruvate (3 Carbons) from Glucose (6 Carbons).
Where does glycolysis occur?
Cytoplasm of cells.
Why is Glycolysis used in both aerobic and anaerobic respiration?
No Oxygen is used.
What’s the first stage of Glycolysis?
- Glucose is phosphorylated from a molecule of ATP producing a molecule of glucose phosphate and one ADP.
- ATP is used to add another phosphate forming Hexose Biphosphate.
- Hexose Biphosphate is then split into two molecules of Triose Phosphate.
What’s the second stage of Glycolysis?
- Triose phosphate is Oxidised (Loses Hydrogen) to form Pyruvate.
- NAD collects the Hydrogen ions forming 2 Reduced NAD molecules.
- 4ADP + 4Pi > 4ATP
What’s the Net gain of ATP from Glycolysis? Why?
2 Net gain of ATP as 4 molecules are made but 2 molecules are used.
What’s the equation for Anaerobic respiration in multiple organisms?
Mammals + Some Bacteria = Lactate
Plants + Yeast = Ethanol
What’s the process of Lactate production in Mammals?
Pyruvate > Lactate (Lactic Acid)
Reduced NAD > NAD Hydrogen used to convert Pyruvate > Lactate.
What’s the process of Ethanol production in Plants and yeast?
Pyruvate - loses CO2 - Ethanal - Hydrogen ion from Reduced NAD to NAD - Ethanol
What does production of Ethanol or Lactate do?
Regenerates oxidised NAD
This can be used to continue Glycolysis when there is little oxygen around.
So a small amount of ATP can still be produced.
