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IP Secondary 3 Biology > Chapter 4 - Nutrition in Plants > Flashcards

Chapter 4 - Nutrition in Plants Flashcards

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1
Q

What is photosynthesis?

A

The process in which light energy is absorbed by chlorophyll and converted into chemical energy
(requires inorganic molecules such as carbon dioxide and water for the synthesis of organic molecules such as glucose)

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2
Q

What is the chemical energy produced in photosynthesis used for?

A

The chemical energy is used to synthesise carbohydrates from water and carbon dioxide.

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3
Q

What occurs in the light-dependent stage (light stage)?

A
  • Light energy is absorbed by chlorophyll and converted to chemical energy
  • Photolysis of water: light energy is used to split water to form H+ ions and oxygen gas
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4
Q

Equation for photolysis of water

A

12H2O → 6O2 + 24H+

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5
Q

What occurs in the light-independent stage (dark stage)?

A
  • H+ ions produced from the photolysis of water are used to reduce carbon dioxide to form glucose by a series of enzyme reactions
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6
Q

Equation for Calvin cycle

A

6CO2 + 24H+ → C6H12O6 + 6H2O

enzyme-controlled reactions

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7
Q

Overall chemical equation of photosynthesis

A

6CO2 + 12H2O –light energy, chlorophyll–> C6H12O6 + 6O2 + 6H2

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8
Q

Overall word equation of photosynthesis

A

carbon dioxide + water –light energy, chlorophyll–> glucose + oxygen + water

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9
Q

Conditions essential for photosynthesis

A

sunlight, chlorophyll, carbon dioxide, suitable temperature (for enzyme activity), water

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10
Q

What is a limiting factor?

A

A factor that directly affects or limits a process if its quantity or concentration is altered

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11
Q

Factors affecting rate of photosynthesis

A

light intensity
temperature
carbon dioxide concentration

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12
Q

Effect of light intensity on the rate of photosynthesis

A

Rate of photosynthesis increases as light intensity increases (until light intensity is no longer a limiting factor)

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13
Q

Effect of temperature on the rate of photosynthesis

A
  • At low temperatures, rate of photosynthesis is slow as enzymes are less active
  • At higher temperature, rate of photosynthesis increases as enzymes become more active
  • At optimum temperature, rate of photosynthesis is maximum as enzymes are most active
  • At extreme temperatures higher than optimum temperature, rate of photosynthesis slows down as enzymes are denatured
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14
Q

Effect of carbon dioxide concentration on the rate of photosynthesis

A

Rate of photosynthesis increases as carbon dioxide concentration increases (until carbon dioxide concentration is no longer a limiting factor)

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15
Q

Fate of glucose in leaves (1): immediate uses

A

Used immediately by plant cells for cellular respiration or to form cellulose cell walls (made up of glucose)

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16
Q

Fate of glucose in leaves (2): storage

A

Excess glucose is temporarily stored as starch in leaves

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17
Q

Fate of glucose in leaves (3): transport

A

Converted into sucrose which is transported to storage organs

18
Q

Why is sucrose used as a form of transport?

A

Sucrose is a non-reducing sugar: will not reduce (take away O2 from) other molecules as it is transported

monosaccharide (glucose) → disaccharide (sucrose)

19
Q

Fate of glucose in leaves (4): amino acids

A

Reacts with nitrates and mineral salts to form amino acids → form proteins for synthesis of new protoplasm in the leaf
Excess amino acids are transported away for synthesis of new protoplasm or for storage as proteins

20
Q

Fate of glucose in leaves (5): fats

A

Used to form fats for storage, cellular respiration or synthesis of new protoplasm

21
Q

Importance of photosynthesis: food and energy

A

Plants are producers in the food chain. Chemical energy stored in plants is transferred to other organisms through feeding.
*can convert light energy to chemical energy

22
Q

Importance of photosynthesis: oxygen and carbon dioxide

A

Helps to purify air by removing carbon dioxide from the atmosphere and releasing oxygen as a by-product
*maintains a constant level of oxygen and carbon dioxide in the atmosphere

23
Q

Importance of photosynthesis: fossil fuels

A

Energy stored in fossil fuels (coal, oil, gas etc) is captured through photosynthesis
(this energy can be released and used through burning fossil fuels)

24
Q

Lamina (leaf blade)

A

large surface area to maximise absorption of sunlight

allows rapid diffusion of carbon dioxide to reach inner cells

25
Q

Petiole

A

positions lamina for maximum absorption of sunlight and gaseous exchange

26
Q

Veins

A

allow transport of water and mineral salts to the cells in the lamina
transport manufactured food from the leaves to other parts of the plant
- branch vein
- branch of mid-rib
- mid-rib

27
Q

Leaves

A

usually arranged in a regular pattern around the stem
paired arrangement / alternate arrangement: ensures that leaves are not blocking one another and each leaf receives optimum amount of light

28
Q

Cuticle

A

waxy layer above the epidermis (wax: fats formed from glucose)
prevents excessive water loss through evaporation
transparent to allow sunlight to penetrate to the mesophyll

29
Q

Upper epidermis

A

single layer of closely packed cells

not really used for photosynthesis, more for structural purposes

30
Q

Palisade mesophyll

A

a few layers of closely packed cells

cells are long, cylindrical and contain numerous chloroplasts for maximum absorption of light

31
Q

Spongy mesophyll

A

irregularly shaped cells

numerous intercellular air spaces for rapid diffusion of gases inside the leaf

32
Q

Vascular bundle

A

xylem and phloem

transport of water and food materials within the plant

33
Q

Lower epidermis

A

single layer of closely packed cells

stomata are found here

34
Q

Stomata and guard cells: during the day

A
  1. Water from adjacent epidermal cells enters guard cells (via osmosis)
  2. Guard cells swell and become turgid → becomes curved and pulls stoma open
35
Q

During the day, cell sap of guard cells has more negative water potential than surroundings because…

A
  • contains more glucose from photosynthesis
  • triggers even more photosynthesis as stomata open and more CO2 enters
  • other ions (e.g. K+) are pumped in to increase negativity of WP of cell sap
36
Q

Stomata and guard cells: at night

A
  1. K+ (and other) ions diffuse out of guard cells
  2. WP in guard cells increases → water exits by osmosis
  3. Guard cells become flaccid → stoma closes
37
Q

Entry of water into leaf

A
  1. Water is brought to the leaves via the xylem vessels in the veins
  2. Water leaves the veins and moves from cell to cell in the mesophyll by osmosis
38
Q

Entry of CO2 into leaf: during the day

A
  1. CO2 is rapidly used up during photosynthesis
  2. CO2 concentration inside the leaf is lower than atmospheric air
  3. CO2 DIFFUSES into leaf via stomata
  4. CO2 dissolves into the film of water surrounding the mesophyll cells and diffuses into the cells
39
Q

What is the absorption spectrum?

A

A graph of relative absorbance of different wavelengths of light by a photosynthetic pigment

40
Q

What is the action spectrum?

A

A graph of relative photosynthetic rates at different wavelengths of light

IP Secondary 3 Biology (8 decks)

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