Photosynthesis

Question 1

Photosynthesis definition

Answer 1

Converting sunlight energy into stored chemical energy (glucose)

Question 2

Photosynthesis equations

Answer 2

(6)CO2 + (6)H2O —-> [Chlorophyll and sunlight energy] C6H12O6 + (6)O2
carbon dioxide + water —-> glucose + oxygen

Question 3

Where CO2 comes from?

Answer 3

The atmosphere, enters bottom of leaf membrane through diffusion

Question 4

Where does H2O come from?

Answer 4

The soil. Enters the plant roots through osmosis

Question 5

Chloroplast

Answer 5

Large oval organelles, site of photosynthesis

Question 6

Leaf structure

Answer 6

-Transparent Upper Epidermal Layer
-Palisade layer (abundant with chloroplasts)
-Spongy mesophyll cells (few chloroplasts) with large air spaces between them
-Vascular bundle, xylem tubes that transport water into the leaves
-Transparent lower epidermal layer the bottom leaf membrane with tiny holes called stomata that are surrounded by 2 guard cells that regulate opening and closing. Gas Diffusion occurs here.

Question 7

Chlorophyll

Answer 7

Pigment within chloroplasts that give plants their green colour

Question 8

Osmosis

Answer 8

The movement of water from an area of high concentration to an area of low concentration, through a semi permeable membrane

Question 9

Light dependent stage

Answer 9

When solar energy from the sun hits the chlorophyll found on the grana in the chloroplast, it excites an electron which results in the production of some ATP.
This energy is then used to split H2O into hydrogen and oxygen molecules. The hydrogen molecules carries on to the next stage, and the oxygen is released (diffusion) because it is a waste product

Question 10

Light independent stage

Answer 10

Occurs in the stroma, the hydrogen along with carbon dioxide synthesise/produces glucose, which is transported to other parts of the plant to be stored as starch for future use for energy & growth. Glucose is also used for respiration.

Question 11

How the amount of water affects rate of photosynthesis

Answer 11

Low concentration of water: Reduction of photosynthesis since there is a low amount of water
High concentration of water: Water stress

Question 12

Process of photosynthesis

Answer 12

-Roots absorb water from soul through osmosis. Osmosis is the diffusion of water from a high conc to a low conc through a semi permeable membrane. In the case of photosynthesis, water from the soil diffuses into the root cell semi permeable membrane, since within it is a low conc of water (high conc of solutes). This is a passive transport which means no energy is required. Water travels up the stem and through the leaves.
-The water travels through the leaf along with with carbon dioxide. Carbon dioxide is from the atmosphere and flows into the leaf through tiny holes called stomata found in the bottom of the leaf. This is diffusion, the movement of particles from a high conc to a low conc. CO2 and H2O travel through the large air spaces between spongy mesophyll cells (for the exchange of CO2 and O2 gases) and reach the palisade layer containing an abundant amount of chloroplasts. This is where photosynthesis occurs.
-Photosynthesis is produced from the light dependent and light independent stages. The light dependent stage occurs in the grana, where the sunlight energy absorbed by the chloroplasts excites an electron which produces some ATP. This ATP is used to split H2O, carrying the H to the light independent stage and O is released out of the leaf through diffusion, out of the stomata in the bottom leaf membrane. In the light independent stage, within the stroma CO2 and H are used to produce glucose, where it is stored for future use & energy and transported throughout the leaf.

Question 13

Limiting Factors

Answer 13

Any of the reactants which slow down or stop the biochemical reaction.

Question 14

Factors limiting the rate of photosynthesis (Carbon Dioxide conc)

Answer 14

The effect of increasing the amount of CO2 increases the rate of p/S to a certain optimal point. Carbon dioxide is needed in the light independent phase to be converted into glucose. Without enough CO2, p/S will slow down and stop. Reactions won’t increase if the amount of CO2 is past its optimal point due to the chloroplasts being saturated with CO2 and another factor becomes limiting (light intensity, temperature)

Question 15

Factors limiting the rate of photosynthesis (Light intensity)

Answer 15

Without enough light, a plant cannot p/s very sufficiently, even if there is enough water or CO2. Increasing the light intensity will boost the speed of p/s up to an optimal point. Anything pass this has no increase in the rate of p/s

Question 16

Factors limiting the rate of photosynthesis (Temperature)

Answer 16

If it is too cold, p/s will decrease, but at very hot temperatures the rate of p/s will stop. At high temps, the hydrogen bonds holding the enzyme shape together weaken and break apart. This means the proteins have denatured and cannot work.