Lecture 5: Photosynthesis, Transpiration, Respiration

Question 1

What are the purposes of leaves?

Answer 1

To carry out photosynthesis and transpiration

Question 2

What is photosynthesis?

Answer 2

Process where glucose is produced from carbon dioxide and water, using energy from light

Question 3

What is the chemical equation for photosynthesis?

Answer 3

CO2 + H2O -> (Light and chlorophyll) C6H12O6 + O2

Question 4

Balance the equation for photosynthesis

Answer 4

Write it out

Question 5

Describe the process of photosynthesis.

Answer 5

• Plant cells contain chloroplast where photosynthesis takes places
• Chloroplasts contain chlorophyll (green pigment) used to absorb light
• CO2 enters the plant from the atmosphere through the stomata
• Roots absorb water from the soil
• Sugars produced by photosynthesis are translocated throughout the plant through the phloem
• Glucose provides energy to run other chemical reactions and produce other carbs (starch and cellulose)

Question 6

What does chlorophyll do?

Answer 6

Absorb light in the chloroplast

Question 7

What are the differences between photosynthesis and respiration?

Answer 7

• Photosynthesis
  
  • Produces glucose
  • Traps energy
  • Consumes H2O and CO2
  • Produces O2
  • Needs light
  • Only happens in cells that have chlorophyll
• Respiration
  
  • Consumes glucose
  • Releases energy
  • Produces H2O, and CO2
  • Consumes O2
  • Does not need light
  • Happens in all living cells in the mitochondria

Question 8

What is the chemical equation for respiration?

Answer 8

C6H12O6 + O2 -> CO2 + H2O + ATP

Question 9

What is transpiration?

Answer 9

Loss of water vapour in a plant mostly from stomata

Question 10

What is the purpose of transpiration?

Answer 10

Allows water and nutrients from roots/soil to enter the rest of the plant.

Lifts water and dissolves minerals up the plant against the force of gravity.

Presence of stomata allow CO2 to be absorbed for photosynthesis which cools leaves. (Like sweating)

Question 11

What is transpirational pull?

Answer 11

Force exerted by transpiration from the leaves draws water up from the roots through the plants.

Force of gravity from leaves transpiring, making the roots draw up more water

Question 12

Fill in the blank: _____ of the water that enters the roots is released in vapour form

Answer 12

98%

Question 13

What time of day does transpiration happen?

Answer 13

Daytime because stomata are present

Question 14

How do stomata work?

Answer 14

Stomata open and close through the use of guard cells. Water flows into guard cells and guard cells become turgid and open a stoma.

Question 15

What affects transpiration?

Answer 15

High temperature = more evaporation and more diffusion = more transpiration

High humidity = less water vapour movement = less transpiration

Light breeze removes water vapour = increased transpiration

Strong wind causes stomata to be absent = no transpiration

Lots of light enlarges stomata opening = more transpiration

Question 16

What reduces the rate of transpiration?

Answer 16

Drought-tolerant leaves with thick waxy cuticles prevent evaporation.

Spines can store water and reduce water loss.

Sunken stomata are located deeper in the epidermis and trap moist air.

Rolled leaves cover the stomata as less surface area is exposed.

Smaller leaves reduce the rate of transpiration due to a smaller surface area.

Question 17

What can hydrophytic plants do to increase their oxygen supply?

Answer 17

Air spaces in tissue to make the plant buoyant. That way leaves can float on the water surface to absorb light and create O2.

Stomata on the upper leaf surface absorb CO2 then H2O in water allows photosynthesis to occur. Therefore, respiration (a method to create ATP) can happen!

Question 18

Why do hydrophytic plants receive less oxygen?

Answer 18

Oxygen has low solubility in water which makes it hard for hydrophytic plants to absorb it.

Question 19

What is the glucose produced in photosynthesis used for?

Answer 19

Provides energy to run other chemical reactions (ie. respiration) and helps produces other carbs like starch and cellulose