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LS 11 - Life Sciences > Photosynthesis > Flashcards

Photosynthesis Flashcards

0
Q

Two major metabolic pathways for energy conversion in organisms

A
  • Photosynthesis
  • Respiration
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1
Q

Metabolism

A

Any chemical reaction taking place in an organism

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2
Q

Respiration

A
  • Process whereby energy from nutrients is converted into energy
  • can be used by the cell in the form of ATP.
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3
Q

ATP

A
  • Adenosine triphosphate
  • Energy carrier of the cell
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4
Q

Anabolic vs catabolic metabolic processes

A
  • Anabolic = building-up process e.g. Photosynthesis
  • Catabolic = breaking down process e.g. Respiration
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5
Q

Energy is…

A

The ability to do work or bring about change

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6
Q

First law of energy

A

Energy can be transformed from one form into another, but it cannot be created or destroyed

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7
Q

Second law of energy

A

When one form of energy is transformed into another form, some useful energy is always lost as heat

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8
Q

Photosynthesis takes place where?

A

In the chloroplasts of plants (and photosynthetic bacteria) that contain chlorophyll

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9
Q

Word equation for photosynthesis

A

(In the presence of light)

(Chlorophyll & enzymes)

Carbon dioxide + water —> glucose + oxygen

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10
Q

Chemical equation for photosynthesis

A
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11
Q

The process of photosynthesis described in words.

A

Carbon dioxide reacts with water in the presence of light, chloroplasts and enzymes to form glucose and oxygen.

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12
Q

Requirements for photosynthesis

A
  • Carbon dioxide
  • Water
  • Light
  • Chlorophyll
  • Enzymes
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13
Q

Products of photosynthesis

A
  • Glucose
  • Oxygen
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14
Q

Plant organs where photosynthesis takes place

A
  • Leaves
  • (and to a lesser extent green stems)
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15
Q

How can a scientist establish whether photosynthesis has taken place in a leaf?

A
  • Test the leaf for starch
  • Glucose is formed by photosynthesis and this is then stored as starch.
16
Q

The outline the test for starch

A
  • Boil leaf in water to soften
  • Pickle leaf in alcohol to dissolve chlorophyl
  • Return leaf to hot water to soften and rince
  • Place in petri dish and add iodine solution
  • If iodine turns black then starch is present
17
Q

How and why is a plant de-starched for an experiment?

A
  • Plant is placed in the dark for a period of time
  • Plant uses up all stored starch in its leaves
  • De-starched plant can now be experimented on, the amount of starch the plants started with is fixed (i.e. none).
18
Q

A leaf with parts that contain no chloroplasts

A

Variegated

19
Q

How to test the requirement of chloroplasts for photosynthesis

A
  • A variegated leaf is exposed to sunlight
  • It is then tested for starch
  • Where the leaf was green, the iodine turns black
  • Where the leaf was cream, the iodine does not change colour
20
Q

How to test the requirement of light for photosynthesis

A
  • A de-starched plant has a leaf or part of a leaf covered with a material that excludes light (e.g. foil).
  • The plant is exposed to sunlight.
  • The leaf is tested for starch.
  • Where the leaf was uncovered, the iodine turns black
  • Where the leaf was covered, the iodine does not change colour
21
Q

How to test the requirement of carbon dioxide for photosynthesis

A
  • de-starched plants are sealed in a container containing either potassium/sodium hydroxide which removes atmospheric carbon dioxide or sodium bicarbonate which adds atmospheric carbon dioxide.
  • The plants are exposed to sunlight.
  • Leaves from each container are tested for starch.
  • Where the plant was had carbon dioxide, the iodine turns black

Where the plant had carbon dioxide excluded, the iodine does not change colour

22
Q

Main parts of a chloroplast

A
  • Double membrane
  • Fluid matrix inside called the stroma
  • Parallel flattened sacs called thylakoids (contains chlorophyll)
  • Clusters of thylakoids are called grana
  • Grana connected by lamellae
23
Q

Two-stages of photosynthesis

A
  • Light-dependent phase: requires light to occur
  • Light-independent phase: does not require light to occur, only occurs if the light-dependent phase has taken place
24
Q

Importance of photosynthesis

A
  • Source of food in food chains
  • thus all heterotrophs ultimately depend on it for food
  • maintain constant global levels of oxygen and carbon dioxide
25
Q

Factors that affect the rate of photosynthesis

A
  • Temperature
  • Levels of carbon dioxide
  • Light intensity
  • Type/wavelength of light
  • Water availability
26
Q

Effect of carbon dioxide concentration on rate of photosynthesis

A

Generally:

  • Lower carbon dioxide levels decreases rate
  • Higher carbon dioxide levels increases rate up to a point, above which the rate decreases again.

Specifically:

  • normal levels in atmosphere average about 0,04% carbon dioxide
  • An increase of carbon dioxide up to about 0,5% increases rate of photosynthesis.
  • however, after 10-15 days the rate decreases
27
Q

Effect of temperature on rate of photosynthesis

A
  • Optimum temperature generally around 25°C
  • Rate of photosynthesis increases from about 10-25°C
  • Rate decreases above 25°C as enzymes controlling photosynthesis become denatured.
28
Q

Effect of light intensity on rate of photosynthesis

A
  • Rate of photosynthesis increases as light intensity increases up to a maximum.
  • The maximum rate is less if plant is not at optimum temperature or carbon dioxide concentration (limiting factors)
29
Q

Explain a limiting factor for photosynthesis

A
  • Photosynthesis rate being limited by one particular factor.
  • E.g. Light, water and carbon dioxide could all be available at optimum levels yet it is a cold winters day.
  • Thus the temperature will be a limiting factor on the growth of plants.
30
Q

How can farmers increase the rate of growth of plants in a greenhouse system?

A
  • Increase the amount of any limiting factor affecting the rate of photosynthesis for their crop.
  • temperature
  • carbon dioxide
  • light
  • water
31
Q

How is temperature regulated in a greenhouse system

A
  • greenhouses trap incoming radiation making it warmer
  • and this can be regulated
  • e.g. with windows or shade netting
32
Q

How can carbon dioxide be regulated in greenhouse systems?

A

greenhouses can have extra carbon dioxide introduced

e.g. From respiration/combustion

Bacteria in compost respire increasing the levels

Artificially it can be pumped in from storage units

33
Q

How can light be increased in greenhouse systems?

A
  • extra lighting on dull/short days
  • appropriate wavelength producing bulbs
34
Q

How can water be regulated in greenhouse systems?

A
  • Irrigation provided when water is limited
  • Timers set to water the correct amount
  • Nutrients can be added to the water
  • Excess water and nutrients can be collected to be recycled

LS 11 - Life Sciences (18 decks)

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