8.9.1 Gas exchange in plants COPY

Question 1

How do plants compare to animals re: their need for for energy?

Answer 1

• Plants like animals
• Need energy constantly
• So they respire all of the time

Question 2

What are the two processes

which allow plants containing chloroplasts to generate energy during the day?

Answer 2

• Photosynthesis
• Respiration

Question 3

What are the two ways a plant aquires the carbon dioxide it needs to conduct photosynthesis

Answer 3

• Some of the CO2 they need comes from respiration
• However the majority diffuses into the leaves from the atmosphere

Question 4

What happens to the oxygen which is produced via photosynthesis

Answer 4

• Some of the oxygen is used in respiration
• The rest diffuses out of the leaves into the atmosphere.

Question 5

What is the process by which plants generate energy at night

Answer 5

• At NIGHT there is NO SUNLIGHT so a plant produces energy by respiration only.
• SOME of the oxygen created by Photosynthesis is taken in by the roots and stem, however MOST gas exchange takes place in the LEAVES

Question 6

What are the differences between photosynthesis and respiration during the day

and respiration at night…

Answer 6

• During the DAY
  
  • The Rate of photosynthesis is FASTER than the rate of respiration
  • Therefore MORE oxygen is produced by photosynthesis than is used in respiration
  • Therefore OXYGEN is the gas which is released into the atmosphere from the leaves
• At NIGHT
  
  • Photosynthesis does not occur owing to the absence of sunlight
  • Therefore no O2 produced
  • So CO2 is released into the atmosphere
• It is the ratio between the net exchange of carbon dioxide and oxygen which matters.

Question 7

label a diagram of the leaf

Draw a diagram of a leaf structure

Question 8

Can plants and aerobic organisms produce oxygen

Answer 8

No

Aerobic organisms USE oxygen day and night

However

ONLY plants PRODUCE oxygen, during the day via photosynthesis.

Question 9

What is the benefit of a leaf being thin from a gas exchange perspective

Answer 9

• The diffusion pathway is short
• Allowing gaseous exchange to be more efficient

Question 10

What controls the diffusion gradients of oxygen and carbon dioxide between the inside and outside of a leaf?

Answer 10

• The diffusion gradients of O2 and CO2
  
  • between the inside and outside of a leaf
• are controlled by
  
  • mitochondria carrying out respiration
  • and chloroplasts carrying out photosynthesis.

Question 11

what is the cuticle

Answer 11

waxy covering on a leaf

which is secreted by epidermal cells

which reduces water loss.

Question 12

What is the benefit of a leaf being thin in gaseous exchange

Answer 12

A thin leaf

Has a short diffusion pathway

Which means that gaseous exchange is efficient

Question 13

What is the stomatal pore

Answer 13

• It is a pore on the lower leaf surface,
• and other arial parts of a plant,
• which are bounded by two guard cells
• through which gases and water vapour diffuse

Question 14

What is the significance of a large surface are for:

1. Gas exchange
2. Photosynthesis

Answer 14

1. There is room for many stomata to faciliate Gas exchange
2. It helps the plant to capture as much light as possible

Question 15

What is the significance of the cuticle and eperdermis being transparent

1. In photosynthesis

Answer 15

1. Allows light to penetrate the mesophyll

Question 16

What is the significance of a leafs thin structure

re: Gas exchange
re: photosynthesis

Answer 16

1. Short diffusion pathway which allows efficient gas exchange
2. allows light to penetrate the leaf easily

Question 17

What is the purpose of elongated palisade cells in photosynthesis

Answer 17

can accommodate a large number of chloroplasts

Question 18

• What is the significant of palisade cells being packed with chloroplasts
  
  • in photosynthesis

Answer 18

• Capture as much light as possible

Question 19

What is the significance of chloroplasts ability to rotate and move within mesophyll cells

in photosynthesis

Answer 19

• they move into the best positions for maximum absorption of light

Question 20

1. What is the significance of airspaces in the spongy mesophyll
   
   1. In gaseous exchange
   2. photosynthesis

Answer 20

1. Allows oxygen and carbon dioxide to diffuse between the stomata and the cells
2. Allow carbon dioxide to diffuse to the photosytnhesising cells

Question 21

What is the purpose of somtatal pores in gas exchange

Answer 21

• Gaseous exchange

Question 22

How do the features of a leaf, influence gas exchange

What features of a leaf influence gaseous exchange

How does the structure of a leave facilitate gas exchange

Answer 22

The structure of a leaf, can influence the process of gaseous exchange in a number of ways.

• Its Large surface area
  
  • Give room for many stomata
• The stomata
  
  • Allow Gas exchange in an out of the cell
• The air spaces in the spongy mesophyll
  
  • Allow O2 and CO2 to diffuse between the stomata and the cells

Question 23

How do the features of a leaf, influence photosynthesis

What features of a leaf influence photosynthesis

How does the structure of a leave facilitate photosynthesis

Answer 23

• It has a large surface area
  
  • which helps to capture as much sunlight as possible
• It is thin
  
  • Which allows the sun to penetrate into the leaf easily
• The cuticle and epidermis are transparent
  
  • Which allows the light to penetrate into the mesophyll
• Palisade cells are elongated
  
  • Which means they can accommodate as many chloroplasts as possible
• Chloroplasts rotate and move within the mesophyll cells
  
  • Which allows them to move into the best position to trap light
• Air spaces in the spongy mesophyll
  
  • Allows oxygen and CO2 to diffuse from the stomata to the cells and
  • Allow CO2 to diffuse to the photosynthesis cells