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biology igcse > B5 > Flashcards

B5 Flashcards

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1
Q

Explain the process of photosynthesis

A

Photosynthesis occurs in leaves -> process that manufactures carbs (glucose) from raw materials using energy from light

Leaves -> CO2 from air
Roots -> water from soil
Energy -> light energy from the sun converts CO2+ water -> food-glucose (occurs in chloroplast that has chlorophyll (the part that absorbs light energy))

Photosynthesis produces glucose and oxygen

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2
Q

What is the word equation for photosynthesis?

A

Carbon dioxide + water -> glucose + oxygen

NEED LIGHT AND CHLOROPHYLL

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3
Q

What is the balanced equation for photosynthesis?

A

6 CO2 + 6 h2O -> C6H12O6 + 6 O2

IN THE PRESENCE OF LIGHT AND CHLOROPHYLL

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4
Q

What does chlorophyll do?

A

Chlorophyll -> green pigment in chloroplast which is in plant cells

Sunlight on chlorophyll -> absorb light energy -> released-> helps CO2 and water combine with help of enzymes -> glucose contains energy from (CO2 and H2O reaction)

Light energy -> chemical energy

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5
Q

What are the ways carbs/glucose is used and stored in the body?

A

Synthesis

Storage

Transport

Respiration

Cellulose

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6
Q

How is glucose used in synthesis?

A

Glucose + minerals from soil -> compounds

Nitrate ions:
Glucose provides material for protein/cell growth

Magnesium ions:
Glucose + ions -> chlorophyll

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7
Q

How is glucose stored in plants?

A

Glucose molecules join together -> insoluble starch -> stored until needed

Can be used as energy source (carbs -> lipids) or as nectar

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8
Q

How is glucose used in respiration?

A

Energy is released from glucose

Used for molecule growth
And food (mostly for animals)

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9
Q

How is glucose used to make cellulose?

A

100s of glucose molecules join -> rough fibrous carbohydrate material -> used for cell wall

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10
Q

Explain an experiment that shows why light is necessary for photosynthesis

A

Before experiment:
Plant destarched (prevents starch already there from affecting results) -> dark cupboard for 24 hours
Test leaf for presence of starch

Experiment:
Cover leaf on plant partially with aluminum foil/black paper (make sure it stuck well) -> place in sunlight for one day
After -> test for presence of starch

Result:
Area covered -> orange brown (bc it didn’t receive light and couldn’t photosynthesis)
Area exposed -> blue black (was exposed to light and could photosynthesis)

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11
Q

Explain an experiment that shows why chlorophyll is necessary for photosynthesis

A

Chlorophyll -> test for starch to see which parts of the leaf are photosynthesising

Experiment:
1. De starch
2. Leave plant in warm+sunny spot
3. Leaf dropped in boiling water (kills cells+breaks down membranes)
4. Leave leaf in hot ethanol for 5-10 min using double boiler (ethanol removes chlorophyll (color change later is easier to see))
5. Left washed/dipped in boiling water
6. Leaf spread onto a white tile
7. Cover in iodine solution
8. entire leaf turns blue-black (bc photosynthesis is happening in whole leaf)

Test for chlorophyll by using a variegated leaf (partially white and green (white parts -> no chlorophyll -> no photosynthesis -> no starch))

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12
Q

Explain an experiment that shows why carbon dioxide is necessary for photosynthesis

A

Experiment:
1. Destarch 2 plants
2. One plant -> bell jar with sodium hydroxide (absorbs CO2)
3. Second plant -> bell jar with beaker of water (control)
4. Place both in sunlight more several hours
5. Test plants for starch

Results:
Sodium hydroxide plant -> orange brown -> couldn’t photosynthesis without CO2
Water plant -> blue black -> had all requirements for photosynthesis

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13
Q

What could effect the rate of photosynthesis?

A

Light -> more light, faster photosynthesis -> if light has damaging UV or is too hot -> damage

Carbon dioxide -> more cO2 -> faster photosynthesis

Temp -> enzymes in photosynthesis (chemical reaction requires enzymes) work best at optimum -> nothing above 40°C or they denature

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14
Q

What can be used in an experiment to observe the rate of photosynthesis?

A

Aquatic plant -> elodea or cabomba
Photosynthesis -> gas released -> if plant is in water oxygen can be seen as bubbles -> # of bubbles/min can show rate of photosynthesis or collect gas in upside down test tube

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15
Q

What experiment can be done to investigate the effect of light intensity on photosynthesis?

A

Set up:
- Beaker of water (with sodium hydrogencarbonate) with:
Inverted funnel with aquatic plant under it
- test tube over opening of funnel to collect gas
- thermometer to monitor temp

Lamp going through glass tank of water -> distance of lamp changes to observe the rate of photosynthesis
More light more photosynthesis

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16
Q

What experiment can be done to investigate the effect of changing temp on photosynthesis?

A

Set up:
- Beaker of water (with sodium hydrogencarbonate) with:
Inverted funnel with aquatic plant under it
- test tube over opening of funnel to collect gas
- thermometer to monitor temp
- lamp at constant distance

  • hot plate heating from the bottom -> vary temp and observe the changing rate of photosynthesis
    Generally more temp more photosynthesis (but not past denature point of enzymes)
17
Q

What experiment can be done to investigate the effect of changing carbon dioxide on photosynthesis?

A

Set up:
- Beaker with:
Inverted funnel with aquatic plant under it
- test tube over opening of funnel to collect gas
- thermometer to monitor temp
- lamp at constant distance

water -> varying amounts of sodium hydrogencarbonate solution
More CO2 more photosynthesis

18
Q

What is a limit factor?

A

If plant had unlimited resources -> limited by its own ability to absorb and react the materials

Reality -> limiting factor is the material that is the lowest at the time

WATER IS USUALLY NOT CONSIDERED TO BE A POTENTIAL LIMITING FACTOR -> amount needed is less than compared to water transpired

19
Q

Using a diagram, label the different parts in leaves of dicotyledonous plants.

A

Chloroplast
Cuticle
Guard cells
Stomata
Upper epidermis
Lowe epidermis
Palisade mesophyll
Spongy mesophyll
Vascular bundles
Xylem
Phloem

20
Q

What is the functions of: palisade mesophyll

A

Column shaped cells
Packed and evenly distributed with chloroplast (absorb the most light) -> maximise photosynthesis

21
Q

What is the functions of: stomata

A

Where gas exchange takes place
Open during day, closed at night
Where evaporation of water takes place
In greater concentration on the underside of the leaf -> reduce water loss

22
Q

What is the functions of: spongy mesophyll

A

Has internal air spaces -> increase surface area: volume ratio for diffusion of gas

23
Q

What is the functions of: guard cells

A

Absorb/lose water to open/close the stomata -> allow CO2 in and O2 out

24
Q

What are the functions of the stomata, spongy mesophyll and guard cells in gas exchange?

A

Low CO2 -> guard cells are turgid (full of water ) -> curve out
Opens stomata -> gas exchange and evaporation of water

High CO2 -> guard leaf lose water (evaporation) -> flaccid -> stomata closes

Allow for easy movement of gas thorough palisade mesophyll (chlorophyll)

25
Q

What is the functions of: xylem

A

Transports water + mineral ions from shoot -> leaves

Made of dead cells

lignin (protein) to strengthen tubes -> support

26
Q

What is the functions of: phloem

A

Transports sugar (glucose) produced in leaves -> stem to growing/storage tissue

Living cells -> sieve tubes with small holes in the cell wall -> flow between cells

27
Q

Why are nitrate ions important?

A

Nitrate ions + glucose -> amino acids -> protein -> cell growth

Absorbed by root hair cells from soil

28
Q

Why are magnesium ions important?

A

Magnesium ions + nitrate ions + glucose -> chlorophyll -> needed for photosynthesis and healthy plant

Absorbed by root hair cells from soil

29
Q

What is the effect of a nitrate ion deficiency in plants?

A

Stunted growth (proteins needed for growth)
Yellowing of leaves (nitrates needed for chlorophyll)

30
Q

What is the effect of a magnesium ion deficiency in plants?

A

Yellowing between veins of leaves (chlorosis)

-> needed to make chlorophyll

31
Q

What are some plant adaptation?

A

Large surface area:
More space for diffusion of gas and absorption of light

Thin:
CO2 diffuses to palisade mesophyll quickly

Chlorophyll:
Absorbs light energy

Network of veins:
Transport of water, carbohydrates

Stomata:
CO2 and O2 can easily diffuse

Epidermis -> thin and transparent:
More light reach palisade cells

Thin cuticle of wax:
Protect leaf without blocking sun

Palisade cell layer on top of leaf:
Maximizes light absorption

Spongy layer:
Air -> diffusion allow CO2 to get through leaf faster (by increasing surface area)

Vascular bundles:
Thick cell wall -> support stem and leaf

32
Q

What is the function of: wax cuticle

A

Protective layer on top of leaf
Prevents water from evaporating where it isn’t supposed to

33
Q

What is the function of: upper epidermis

A

Thin+transparent -> allows light to enter

34
Q

What is the function of: lower epidermis

A

Contains guard cells+stomata

35
Q

How is glucose transported?

A

Sugars transported as sucrose

biology igcse (11 decks)

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