photosynthesis

Question 1

photosynthesis

Answer 1

photosynthesis is a biochemical pathway that absorbs light energy(light energy is the ultimate supply for energy for living things is the light energy from the sun )and it uses it to synthesis chemical energy it has two stages the first stage being the light dependant stage and the light independent stage

Question 2

anabolic reaction

Answer 2

is endergonic and requires energy

Question 3

light-dependent stage

Answer 3

light dependant stage occurs in the thylakoid (requires light to occur)

• the light energy from the sun is absorbed by the chlorophyll
• then the energy used to energise electrons SPLIT water molecules into hydrogen ion and oxygen gas
• ATP is then produced from ADP and Pi with energy from the sun
• NADPH is produced from NADP+ with electrons and H+ ions

the inputs of the light-dependent stage include: light water, ADP+Pi and NADP+

the outputs: oxygen, ATP and NADPH

Question 4

light-independent stage

Answer 4

the light-independent stage occurs in the stroma(doesn’t need light to occur)

• this stage uses the ATP and NADPH synthesised in the light-dependent stage.
• carbon dioxide is taken into a leaf via stomata
• ATP and NADPH provide energy to reduce CO2into GA3P (3 carbon molecule)
• GA3P molecule leaves chloroplast and enters the CYTOSOL
• 2 GA3Pmolecues then combine to form glucose

the inputs of the light-independent are: carbon dioxide, ATP and NADPH

outputs: glucose, water ADP + Pi and NADP+

Question 5

chroloplasts

Answer 5

chloroplasts are the specialised plastids in which photosynthesis occurs. the structure of chroloplasts is enclosed by a double membrane envelope (inner and outer membrane )

• it has a thylakoid which looks like a flattened membrane sac that contains chlorophyll it has a surface area for light absorption
• a stack of thylakoids which are called grana
• a stroma is a fluid matrix that contains enzymes
• and a sheet-like thylakoid membrane between grana (usually looks like a line that’s not part of the stack)this is called thylakoid lamellae

Question 6

origins of chloroplasts

endosymbiosis

Answer 6

endosymbiosis is were cyanobacteria were engulfed by eukaryote cells that lived in a symbiotic relationship

the evidence that supports this is

• chroloplasts contain circular DNA (plastids) unquie to the nuclear DNA
• chlroloplats have similar ribosomes to bacteria
• plant cells cannot reproduce chloroplasts if they are removed from the cell
• outter membrane of chrloplats contains porin

Question 7

what are the factors that affect the rate of photosythesis

Answer 7

• carbon dioxide
• light intensity
• temputure

Question 8

carbon dioxide( a factor that affects the rate of photosynthesis )

Answer 8

The amount of carbon dioxide that enters a plant depends on the number of stomata and whether they are open or closed (due to water stress). The rate of photosynthesis is greater at higher concentrations of CO2.

Question 9

light intensity ( a factor that affects the rate of photosynthesis )

Answer 9

The rate of photosynthesis increases as light intensity increases until a certain point, where there is a plateau (which indicates the maximum photosynthetic rate).

Question 10

temperature ( a factor that affects the rate of photosynthesis )

Answer 10

Photosynthesis will be greatest in a temperature which is optimum for the functioning of its enzymes.

Temperatures above this range can cause denaturation of enzymes and reduce the rate of photosynthesis.