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science > biology chapter 6 > Flashcards

biology chapter 6 Flashcards

1
Q

define photosynthesis

A

Photosynthesis is the process by which green plants use the energy from sunlight to synthesize nutrients from carbon dioxide and water. Photosynthesis in plants generally involves the green pigment chlorophyll and generates oxygen as a by-product.

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2
Q

what are the inputs of photosynthesis

A

carbon dioxide and water

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3
Q

what are the outputs of photosynthesis

A

glucose and oxygen

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4
Q

what is the word equation of photosynthesis

A

carbon dioxide + water —–> glucose + oxygen

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5
Q

what is the balanced equation for photosynthesis

A

6CO2 + 6H2O → C6H12O6 + 6O2

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6
Q

how do we test for the presence of starch

A

to test for the presence of starch in a leaf

  1. remove the green leaf from a plant that has been exposed to sunlight for a few hours.
  2. immediately put the leaf in boiling water for two minutes
  3. put the boiled leaf in a boiling tube containing some alcohol or ethanol. place the boiling tube in a beaker of hot water
  4. the leaf is now very brittle. gently remove the leaf and put it back into the hot water. this softens the leaf and makes it more permeable to iodine solution
  5. remove the leaf and spread it evenly on a white tile. add a few drops of iodine solution to the leaf
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7
Q

how do we find whether sunlight is necessary for photosynthesis

A

to find out whether sunlight is necessary for photosynthesis

  1. destarch a potted plant by placing it in the dark for two days
  2. remove the leaf and test it for starch
  3. place a leaf, which is still attached to the plant, between two pieces of black paper. each piece of paper has a certain pattern cut out from it. fasten the pieces of paper using paper clips. place the plant in strong sunlight.
  4. after a few hours, remove the leaf and test it for starch.
  5. make a drawing of the leaf to show the regions that are stained blue-black
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8
Q

how do plants absorb sunlight

A

chlorophyll is a green pigment found in the chloroplasts of plants. it absorbs sunlight, the green colour in the leaves is due to the presence of chlorophyll

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9
Q

how to we find out whether chlorophyll is necessary for photosynthesis

A
  1. destarch the plant with variegated leaves, such as a Duranta, placing it in the dark for two days
  2. expose the plant to strong sunlight for a few hours
  3. remove one leaf. make a drawing to show the distribution of the green parts, which are the parts that contain chlorophyll
  4. decolourise the leaf and test it for starch
  5. make a drawing of the leaf to show the distribution of your black-blue colour. compare this with your drawings in step 3
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10
Q

how do we find out whether carbon dioxide is necessary for photosynthesis

A
  1. destarch two plotted plants by placing them in the dark for two days
  2. enclose the pot in polythene bags. secure the bags to the plant stems
  3. place one pot in the bell jar. the plant does not have a supply of carbon dioxide from the air because the soda lime and potassium hydroxide solution rapidly absorb carbon dioxide
  4. set up a control using pebbles and water in place of soda lime and potassium hydroxide solution respectively
  5. leave both set ups in strong sunlight for a few hours
  6. remove a leaf from each plant. test the leaves for starch
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11
Q

what are essential for photosynthesis

A

sunlight, carbon dioxide, chlorophyll

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12
Q

what are some conditions that are also needed for photosynthesis

A

suitable temperature and water

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13
Q

what are some of the factors that affect the rate of photosynthesis

A
  • light intensity
  • the concentration of carbondioxde
  • temperature
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14
Q

what happens to the glucose that is formed during photosynthesis

A
  • used immediately to provide energy source for respiration
  • energy is used to turn sugars, nitrates and other nutrients into amino acids which build up proteins
  • to make cellulose, the main structural material in cell walls
  • energy stored as starch in leaves, seeds, roots and tubers
  • energy stored as sucrose
  • to make fats and oils
  • raw materials fro growth, repair and replacement of the damaged parts
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15
Q

why is photosynthesis important

A
  • photosynthesis makes chemical energy available to animals and other organisms
  • photosynthesis removes carbon dioxide and removes oxygen
  • energy is stored in fossil fuels through photosynthesis
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16
Q

state some facts about chlorophyll

A
  • the green pigment involved in photosynthesis
  • traps light and passes high energy electrons into photosynthesis
  • gives a green colour to chloroplasts
17
Q

state some facts about chloroplasts

A
  • the organelle involved in photosynthesis
  • organised into chloroplasts which provide space for both light and dark reactions of photosynthesis
  • gives a green colour to plants
18
Q

how to guard cells control the size of the stomata

A

in sunlight: the guard cells contain chloroplasts, but epidermal cells do not. in daylight, the guard cells manufacture glucose by photosynthesis, they absorb water from nearby epidermis cells. they become turgid and more curved. this is because the cell wall around the stomatal pore is thicker than the other parts of the cell. hence the cell curves around the stoma and the stoma opens

on a hot sunny day: when the leaf loses too much water in strong sunlight, the stomata close. this prevents excessive loss of water by the leaf. in this way, the guard cells can regulate the rate of diffusion of gases into and out of the leaf.

18
Q

how do carbon dioxide and water enter the leaf

A
  1. in daylight when photosynthesis occurs, the carbon dioxide in the leaf is rapidly used up. the carbon dioxide concentration in the leaf becomes lower than that in the atmospheric air, so a diffusion gradient exists. therefore, carbon dioxide diffuses from the surrounding air through the stomata into the air spaces in the leaf
  2. the surfaces of the mesophyll cells are always covered by a thin film of water. this is so that carbon dioxide can dissolve in it
  3. the dissolved carbon dioxide then diffuses into the cells
19
Q

how does xylem transport water and mineral ions to the leaf

A
  1. the xylem transports water and dissolved mineral ions to the leaf from the roots.
  2. once out of the veins, the water and mineral ions move from the cell right through the mesophyll of the leaf
20
Q

describe the waxy cuticle

A

PROTECTIVE LAYER ON TOP OF THE LEAF, PREVENTS WATER FROM EVAPORATING

21
Q

describe the upper epidermis

A

THIN AND TRANSPARENT TO ALLOW LIGHT TO ENTER PALISADE MESOPHYLL LAYER UNDERNEATH IT

22
Q

describe the palisade mesophyll

A

COLUMN SHAPED CELLS TIGHTLY PACKED WITH CHLOROPLASTS TO ABSORB MORE LIGHT, MAXIMISING PHOTOSYNTHESIS

23
Q

describe the spongy mesophyll

A

CONTAINS INTERNAL AIR SPACES THAT INCREASES THE SURFACE AREA TO VOLUME RATIO FOR THE DIFFUSION OF GASES (MAINLY CARBON DIOXIDE)

24
Q

describe the guard cell

A

ABSORBS AND LOSES WATER TO OPEN AND CLOSE THE STOMATA TO ALLOW CARBON DIOXIDE TO DIFFUSE IN, OXYGEN TO DIFFUSE OUT

24
Q

describe the stomata

A

WHERE GAS EXCHANGE TAKES PLACE; OPENS DURING THE DAY, CLOSES DURING THE NIGHT. EVAPORATION OF WATER ALSO TAKES PLACE FROM HERE. IN MOST.
PLANTS, FOUND IN MUCH GREATER CONCENTRATION ON THE UNDERSIDE OF THE LEAF TO REDUCE WATER LOSS

24
Q

describe the vascular bundle

A

CONTAINS XYLEM AND PHLOEM TO TRANSPORT SUBSTANCES TO AND FROM THE LEAF

25
Q

describe the lower epidermis

A

CONTAINS GUARD CELLS AND STOMATA

26
Q

describe the xylem

A

TRANSPORTS WATER INTO THE LEAF FOR MESOPHYLL CELLS TO USE IN PHOTOSYNTHESIS AND FOR TRANSPIRATION FROM STOMATA

27
Q

describe the phloem

A

TRANSPORTS SUCROSE AND AMINO ACIDS AROUND THE PLANT

28
Q

During the day plants photosynthesise at a faster rate than they respire so the overall direction of gas exchange is:

A

Carbon dioxide diffuses out of leaves
Oxygen diffuses in

28
Q

At night plants respire at a faster rate than they photosynthesise so the overall direction of gas exchange is different:

A

Oxygen diffuses into leaves
Carbon dioxide diffuses out

29
Q

how do we investigate the gas exchange in plants

A

We can investigate the effect of light on the net gas exchange in an aquatic plant using a pH indicator such as hydrogencarbonate

30
Q

what does it mean when the colour of the hydrogen carbon indicator is yellow

A

highest concentration of carbon dioxide, more respiration than photosynthesis and a lower pH

31
Q

what does it mean when the colour of the hydrogen carbon indicator is orange

A

higher concentration of carbon dioxide, more respiration than photosynthesis and a lower pH

32
Q

what does it mean when the colour of the hydrogen carbon indicator is red

A

photosynthesis= respiration

32
Q

what does it mean when the colour of the hydrogen carbon indicator is magenta

A

lower concentration of carbon dioxide, more photosynthesis than respiration, higher pH

32
Q

what does it mean when the colour of the hydrogen carbon indicator is purple

A

lowest concentration of carbon dioxide, more photosynthesis than respiration, higher pH

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