Photosynthesis

Question 1

What is the difinition

Answer 1

Photosynthesis is a process by which chlorophyll in the chloroplast of green plants absorbs radiant energy from the sun ,CO2 from the atmosphere,water from the soil to produce carbohydrates (glucose stored in plants ). Oxygen is released into the atmosphere during this process. Enzymes in the cells are also needed for the process. Excess glucose is converted into starch in the plant

Question 2

What is the equation

Answer 2

CO2.+ water —-(radiant energy , chlorophyll, enzymes ) ——- glucose + oxygen

Question 3

What is chlorophyll

Answer 3

The green , light trapping pigment found in plant cells

Question 4

What is chloroplast

Answer 4

A chlorophyll containing organelle in the cytoplasm of plant cells

Question 5

What is photolysis

Answer 5

splitting of water molecules into oxygen and hydrogen
atoms during photosynthesis

Question 6

What is light phase

Answer 6

The light dependent phase in photosynthesis taht takes place in the grana ( stacked) of chloroplast

Question 7

What is dark phase (Calvin cycle )

Answer 7

The light independent phase in photosynthesis that takes place in the stroma of a chloroplast

Question 8

What is stroma

Answer 8

Fluid part of the chloroplast where the dark phase takes place

Question 9

What is ATP(adenosine triphosphate)

Answer 9

Energy carrier in cells that takes chemical energy to the dark phase during photosynthesis

Question 10

What is the chemical equation of photosynthesis

Answer 10

6CO2 + 6H2O——C6H12O6 + 6O2

Question 11

Explain the light phase

Answer 11

• Radiant energy is absorbed by chlorophyll in the grana (thylacoid

) - water is absorbed into the grana of the chloroplast

• Radiant energy is used to split the water molecules (protolysis) to release oxygen,hydrogen

-oxygen Which goes back into the atmosphere

-releases energy rich hydrogen ions which are taken
Into the light independent phase

-radiant energy also causes the energy carrier
ATP to be formed (phosphorylation) which
will be used in the lignt independent phase

Question 12

Explain the light independent phase

Answer 12

-Carbon dioxide is absorbed from the atmosphere

-carbon dioxide and energy rich hydrogen atoms from
the light light dependent phase are combined using
ATP from the light dependent phase to form glucose

-excess glucose is stored as starch granules
This phase can take place in the presence of light or during the absence of light because light is not required during is phase

Question 13

What’s re the difference between light and dark phase

Answer 13

Light phase - Occurs in the grana
Dark phase- Occurs in the stroma

Light phase -Light is required
Dark phase - Light is not required

Light phase - Radiant energy and water are absorbed and used for the reactions of photolysis & phosphorylation
Dark phase-Carbon dioxide is absorbed fro atmosphere

Light phase - Photolysis occurs hydrogen and oxygen formed by splitting
H2O.Phosphorylation occurs: ATP is produced and oxygen is released to the atmosphere
Dark phase -Hydrogen and carbon dioxide combine by using ATP to form glucose. Glucose is formed and excess is stored as starch

Question 14

What is the importance of photosynthesis

Answer 14

1. It supplies energy to almost all living organisms. Plants are the only organisms that can convert the sun’s energy into organic compounds.
2. Plants convert the simple sugars made during photosynthesis into more complex organic compounds such as starch, fats, proteins and vitamins which form food source for all living organisms.
3. Photosynthesis regulates the concentrations of carbon dioxide, and oxygen in the atmosphere, and plays a key role in the carbon cycle in preventing global warming.
4. Plants absorb more carbon dioxide during photosynthesis than they release during cellular respiration.
5. Organisms require the oxygen released during photosynthesis for cellular respiration to provide energy to all cells and organs.

Question 15

What’s are the factors affecting the rate of photosynthesis

Answer 15

Light intensity
Concentration of carbon dioxide (COz)
Temperature

Question 16

Explain light intensity

Answer 16

When light intensity increases, the rate of photosynthesis also increases to an optimum level. If light intensity continues to increase, there will be no effect on the rate of photosynthesis.
When light intensity decreases, the rate of photosynthesis also deceases.
• When the light intensity is low, the rate of photosynthesis is low.

Question 17

Explain concentration of CO2

Answer 17

As the carbon dioxide concentration level increases, the rate of photosynthesis increases.
If the carbon dioxide concentration is higher than the optimum amount, photosynthesis will remain constant.

Very high CO, levels in the plant cause the rate of photosynthesis to drop. This happens because the excess CO, combines with HO to form carbonic acid.
The acidic conditions damage the enzymes that control photosynthesis, causing a drop in the rate of photosynthesis.

When carbon dioxide concentration is low, the rate of photosynthesis is low. Light independent phase cannot take place more quickly than what it does the optimum level of carbon dioxide concentration.

Question 18

Explain temperature

Answer 18

Temperature
Photosynthesis can take place in mesophytic plants between 10°C and 35°C, the optimum being 25°C. As the temperature increases, the rate of photosynthesis also increases, until an optimum temperature of 25°C is reached.
Increasing temperatures above 25°C, cause the rate of photosynthesis to rapidly decline, to the point at which photosynthesis can no longer take place. This is because, when exposed to very high temperatures, the enzymes involved in photosynthesis become denatured (lose their shape) and are rendered useless.

At low temperatures photosynthetic enzymes become inactive and the energy available for the reaction is reduced.