Topic 5 - Energy transfers in and between organisms Flashcards

Question

What are the photosystems and what nm do they absorb light best at?

Answer 1

Photosystem I 700nm Photosystem II 680nm

Answer 2

Contained within the inner membrane of the chloroplast and surrounding the thylakoids is a gel-like substance called the stroma

Answer 3

Enzymes, sugars and organic acids Carbohydrates produced by photosynthesis and not used straight away are stored as starch grains in the stroma

Answer 4

Reactions that involve oxidation and reduction

Answer 5

Has gained electrons May have gained hydrogen Or lost oxygen

Answer 6

Lost electrons May have lost hydrogen Or gained oxygen

Answer 7

Molecule that aids the function of an enzyme They work by transferring a chemical group from one molecule to another

Answer 8

NADP Transfers hydrogen from one molecule to another

Answer 9

1. Light energy excites electrons in chlorophyll - Light energy absorbed by PSII -Light energy excited electrons in chlorophyll -Electrons move to higher energy level -The high-energy electrons are released from the chlorophyll and move down the electron transport chain to PSI

Answer 10

Photolysis of water produces protons, electrons and oxygen -As the excited electrons from chlorophyll leave PSII to move down the electron transport chain, they must be replaced -Light energy splits water into protons, electrons and oxygen - this is photolysis -Reaction is H2O --> 2H++ 1/2O2

Answer 11

Energy from the excited electrons makes ATP -The excited electrons lose energy as they move down the electron transport chain -This energy is used to transport protons into the thylakoid so that the thylakoid has a higher concentration of protons than the stroma -This forms a proton gradient across the thylakoid membrane -Protons move down their concentration gradient, into the stroma, via the enzyme ATP synthase, which is embedded into the thylakoid membrane -The energy from this movement combines ADP and Pi to form ATP

Answer 12

Energy from the excited electrons generates reduced NADP -Light energy is absorbed from PSI, which excited the electrons again to an even higher energy level -Finally, the electrons are transferred to NADP, along with a proton from the stroma, to form reduced NADP

Answer 13

The process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive ATP synthesis is called chemiosmosis

Answer 14

The electrons from the chlorophyll molecule aren't passed onto NADP, but are passed back to PSI via electron carriers This means electrons are recycled and can repeatedly flow through PSI This process doesn't produced any reduced NADP or oxygen - only small amounts of ATP

Answer 15

The Calvin Cycle

Answer 16

Stroma of chloroplasts

Answer 17

CO2 enters the leaf through the stomata and diffuses into the stroma of the chloroplast Here, it is combined with ribulose bisphosphate This reaction is catalysed by the enzyme rubisco This gives an unstable 6-carbon compound, which quickly breaks down into two molecules of a 3-carbon compound called glycerate 3-phosphate

Answer 18

Hydrolysis of ATP provides energy to reduce the 3-carbon compound, GP, to a different 3-carbon compound called triose phosphate (TP) This reaction also requires H+ ions, which come from reduced NADP (from light-dependent reaction) Reduced NADP is recycled to NADP Some triose phosphate is the converted into useful organic compounds and some continues in Calvin cycle to regenerate RuBP

Answer 19

Five out of every six molecules of TP produced in the cycle aren't used to make useful organic compounds, but to regenerate RuBP Regenerating RuBP uses the rest of the ATP produced by the light-dependent reaction

Answer 20

Two molecules of triose phosphate

Answer 21

Three turns of the Calvin cycle produces six molecules of triose phosphate because two molecules of TP are made for every one CO2 molecule used Five out of six of these TP molecules are used to regenerate RuBP This means for three turns of the cycle, only one TP is produced that's used to make a hexose sugar A hexose sugar has 6 carbons, so two TP molecules are needed to form one hexose sugar This means the cycle must turn six times to produce two molecules of TP that be used to make one hexose sugar Six turns of the cycle need 18 ATP and 12 reduced NADP from the LDR

Answer 22

Hexose sugars are made from two triose phosphate molecules and larger carbohydrates are made by joining hexose sugars in different ways

Answer 23

These are made using glycerol, which is synthesised from triose phosphate, and fatty acids, which are synthesised from glycerate 3-phosphate

Answer 24

Some amino acids are made from glycerate 3-phosphate

Answer 25

1. High light intensity of a certain wavelength 2. Temperature around 25 degrees Celcius 3. Carbon dioxide at 0.4% 4. Constant supply of water

Answer 26

Light is needed to provide the energy for the light-dependent reaction - the higher the intensity of the light, the more energy it provides Only certain wavelengths of light are used for photosynthesis The photosynthetic pigments chlorophyll a, chlorophyll b and carotene only absorb the red and blue light in sunlight

Answer 27

Photosynthesis involves enzymes If the temp falls below 10 the enzymes become inactive, but if the temp is more than 45 they may start to denature Also, at high temperatures stomata close to avoid losing too much water This causes photosynthesis to slow down because less carbon dioxide enters the leaf when the stomata are closed

Answer 28

CO2 makes up 0.04% of the gases in the atmosphere Increasing this to 0.4% gives a higher rate of photosynthesis, but any higher and the stomata start to close

Answer 29

Too little water and photosynthesis has to stop but too much and the soil becomes waterlogged (reducing the uptake of minerals, such as magnesium, which needs to make chlorophyll a)

Topic 5 - Energy transfers in and between organisms Flashcards

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