topic 5 Flashcards
what is phosphorylation?
adding phosphate to a molecule
e.g. ADP is phosphorylated to ATP
what is photophosphorylation?
adding phosphate to a molecule using light
What is photolysis?
splitting a molecule using light energy
What is photoionisation?
when light energy ‘excites’ electrons in an atom/molecule, causing them to be released
The release of electrons causes the atom/molecule to become a positively-charged ion
What is decarboxylation?
the removal of carbon dioxide from a molecule
What is dehydrogenation?
the removal of hydrogen from a molecule
What is a coenzyme?
a molecule that aids the function of an enzyme
they work by transferring a chemical group
NADP is a coenzyme used in photosynthesis. It transfers hydrogen from one molecule to another
- this means it can reduce (give hydrogen to) or oxidise (remove hydrogen)
What are the 2 stages in photosynthesis?
Light-dependent reaction and the light-independent reaction
Both happen in chloroplast, but in different locations:
-LDR occurs on thylakoid membranes
-LIR occurs in the stroma
LDR is the first stage, LIR is the second stage
What are the stages of the light-dependent reaction in photosynthesis? (stage 1 of 2)
LDR requires light
Light energy and water are required to make ATP and NADP which are needed in this stage
1.Photolysis
2. Photoionisation or chlorophyll
3. Chemiosmosis
4. Production of ATP and reduced NADP
Describe the light-dependent reaction in photosynthesis
- Photolysis of water
-Light energy is absorbed by chlorophyll and splits water into oxygen, H+ and -e.
-The H+ is picked up by NADP to from NADPH (reduced NADP) and is used in the LIR
-the negative electrons are passed along a chain of electron carrier proteins
-oxygen is either used in respiration or diffuses out of the leaf through the stomata
-electrons are replaced in the chlorophyll when they leave during the next stage
- Photoionisation of chlorophyll
-Light energy is absorbed by the chlorophyll - energy results in electrons becoming excited and raising up an energy level to leave the chlorophyll
-therefore the chlorophyll has been ionised by light
-some of the energy released from the electrons is used to make ATP and reduced NADP in chemiosmosis
- Chemiosmosis:
-the electrons that gained energy and left the chlorophyll move along a chain of proteins embedded within the thylakoid membrane
-as they move along, they release energy which some is used to transport protons across chloroplast membranes.
-an electrochemical gradient is created, as the thylakoid has a higher concentration of protons than the stroma.
-the protons pass through the enzyme ATP synthase when they move down their conc gradient into the stroma, which results in the production of ATP, adding a phosphate group to ADP.
-the protons combine with the co-enzyme NADP to produce reduced NADP, as the protons move from a high to low concentration gradient - known as chemiosmosis
Describe the steps involved in the light-independent reaction of photosynthesis
-Occurs in stroma of chloroplast
-requires enzyme rubisco to catalyse reaction
-temp sensitive due to enzymes
-uses CO2, NADPH and ATP to form a hexose sugar (e.g. glucose)
-6 turns of cycle required to make one 6 carbon organic compound.
- Carbon dioxide is combined with ribulose biphosphate (RuBP) to form 2 molecules of glycerate -3 phosphate (G3P)
-Catalysed by enzyme rubisco
-Turns RuBP (a 5-carbon compound) into an unstable 6-carbon compound, which quickly breaks down into 2 molecules of a 3- carbon compound called glycerate-3 phosphate (G3P) - ATP and reduced NADP required for the reduction of (G3P) to triose phosphate (TP)
-Hydrolysis of ATP (from the LDR) provides energy to turn G3P into a different 3-carbon compound called triose phosphate (TP)
-Requires H+ ions, which come from NADPH (from the LDR), NADPH is recycled into NADP
-1 carbon from the TP is converted to be used in the production of useful organic compounds (e.g. glucose) and 5 carbons return to the cycle to regenerate RuBP - RuBP is regenerated
-5 out of 6 molecules of TP produced in the cycle are used to regenerate RuBP
-Regenerating RuBP uses the rest of the ATP produced by the LDR.
Calvin cycle also makes lipids, carbs and amino acids.
What are autotrophs?
use energy from the sunlight (photoautotroph) to produce glucose
What is biomass and how do you calculate it?
The dry mass of carbon in an organism
-Place material in an oven at 80 degrees for 24 hours
- Mass must be removed to be measured periodically
-Stop when mass stops decreasing
What are heterotrophs?
cannot fix carbon so obtains organic carbon by eating other organisms
What are saprobionts?
microorganisms that feed by releasing enzymes externally, decomposing and digesting the food. Cause decay
