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
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
Explain the parts of the nitrogen cycle
- Nitrogen fixation -
- Nitrogen-fixing bacteria exist in anaerobic conditions in soil. Possess enzyme nitrogenase which allows them to combine nitrogen with hydrogen to produce ammonia -some ammonia enters soil.
-Symbiotic nitrogen-fixing bacteria live in root nodules of legumes and produce ammonia which is mainly used by the plant. The bacteria get carbohydrates produced by the plant in photosynthesis - Ammonification -
- Saprobionts include putrefying bacteria and fungi that release digestive enzymes that break down organic matter.
-Proteins are hydrolysed into amino acids then deaminated (removing the amine group). The free amine group reacts with hydrogen to form ammonia
3.Nitrification -
- Ammonia becomes ionised in the soil and exists as ammonium ions
-Nitrifying bacteria are chemoautotrophs - they derive energy from the chemical conversion of ammonium ions to nitrites and nitrates
-Nitrification is a 2 step process: ammonium ions are oxidised to nitrite ions and these are then further oxidised to nitrate ions (aerobic process)
- Denitrification -
- Denitrifying bacteria thrive in anaerobic conditions - include waterlogged soil or soil that has been compacted
- Denitrifying bacteria use the oxygen present in nitrate ions for respiration. Nitrate ions become reduced to either oxides of nitrogen or nitrogen gas
-Nitrogen gas is released back into the atmosphere.
