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Sec 3 Pure Bio > Nutrition in Plants > Flashcards

Nutrition in Plants Flashcards

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Biology 101 flashcards
1
Q

Autotrophic nutrition

4 pts

A
  • Plants are able to synthesise their food by the process of photosynthesis
  • photo=light, synthesis=putting tgt or manufacturing
  • plants are known as autotrophs
  • all life on earth depends on photosynthesis
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2
Q

Glucose

3 pts

A
  • formed from CO2 during photosynthesis
  • carbohydrates: simplest energy-rich organic molecules
  • monosaccharides: simplest stable form of carbohydrates e.g. glucose
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3
Q

Starch

4 pts

A
  • presence of starch in leaves= photosynthesis took place
  • when glucose form up more that used up, excess changed to starch for storage
  • starch formation not photosynthesis
  • use iodine test to test for starch
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4
Q

Destarching (explanation)

3 pts

A
  • must be carried out on plants before experiments
  • ensures that starch is absent in leaves
  • thus all starch present after experiments must have been formed during the experiment
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5
Q

Destarching (Action to take)

4 pts

A
  • put plant in the dark for 2 days
  • darkness, photosynthesis stops
  • enzymes in leaves change starch to sucrose
  • surcose transported to other parts of plant
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6
Q

How to test for starch in leaf?

6 pts

A
  • remove a green leaf from a plant that has been exposed to sunlight for a few hours
  • put leaf in boiling water for 2 min (denature enzymes, stop photosynthesis)
  • put boiled leaf in a boiling tube containing alcohol/ethanol (alcohol removes chlorophyll from leaf)
  • place boiling tube in a water bath
  • gently remove the leaf and spread it evenly on white tile
  • add a few drops of iodine solution (if starch present, leaf turn blue-black)
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7
Q

Functions of leaves and roots

3 pts

A

Leaves:
-absorb CO2 from air
-contain chlorophyll which absorbs sunlight during the day
Roots: absorb water and mineral salts from the soil

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8
Q

Experiment to find out if sunlight is necessary for photosynthesis + observation
(5 pts)

A
  1. A potted plant is destarched by placing it in the dark for 2 days
  2. 1 Leaf is removed and tested for presence of starch
  3. Another leaf (still attached to plant) is sandwiched between two pieces of black paper, plant placed in strong sunlight
  4. The leaf is then tested for presence of starch after a few hours
    Observation: Only parts exposed to sunlight will be stained blue-black, so sunlight is necessary for photosynthesis
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9
Q

Experiment to find out if chlorophyll is necessary for photosynthesis

A
  1. A plant with variegated (has both green and non-green parts) leaves destarched by being placed in the dark for 2 days
  2. Plant placed in strong sunlight for a few hours
  3. Leaf is removed, decolourised and tested for starch
    Observation: only those parts containing chlorophyll will manufacture starch be stained blue-black, so chlorophyll is necessary for photosynthesis
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10
Q

Experiment to find out if CO2 is necessary for photosynthesis +observation + apparatus needed

A
  1. 2 potted plants destarched by being placed in dark for 2 days
  2. the pots of plants are enclosed in polythene bags and placed in strong sunlight for few hrs (one with normal atmospheric air, the other no CO2)
  3. After a few hrs, a leaf is removed from each pot and tested for presence of starch
    - Observation: The iodine turns blue-black for the leaf exposed to air with CO2, so CO2 is necessary for photosynthesis
    - Apparatus for no CO2: soda lime, potassium hydroxide solution (removes CO2)
    - Apparatus for control: pebbles, water
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11
Q

What are the conditions that are essential for photosynthesis?
(5 pts)

A
  • Sunlight
  • Chlorophyll
  • Carbon dioxide
  • Suitable temp (affects enzyme activity)
  • Water
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12
Q

What is photosynthesis?

A
  • process in which light energy is absorbed by chlorophyll and converted to chemical energy
  • requires inorganic molecules eg CO2 and water for synthesis of organic molecules like glucose
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13
Q

Where does photosynthesis occur?

A

Leaf’s mesophyll layer, cytoplasm of mesophyll cells, in an organelle called the choroplast which contains the green pigment chlorophyll

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14
Q

Name the 2 main stages of photosynthesis

A
  • light-dependent stage (light stage)

- light-independent stage (dark stage)

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15
Q

Light-dependent stage (processes that occur)

A
  • absorption of light energy to chlorophyll
  • conversion of light energy to chemical energy
  • photolysis of water (12 H2O molecules to 6 O2 molecules+ 24 H molecules)
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16
Q

Light-independent stage

A
  • hydrogen atoms produced from photolysis of water used to reduce CO2 to form glucose by a series of enzyme reactions
  • 6 CO2 to C6H12O6(glucose) +6H2O thru enzyme-controlled reactions
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17
Q

Factors that affect rate of photosynthesis

3 pts

A
  • light intensity
  • carbon dioxide concentration
  • temperature
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18
Q

Definition of limiting factors

A

A factor that directly affects or limits a process if its quantity or concentration is altered (increase/decrease)

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19
Q

Experiment to find out how rate of photosynthesis is affected by light intensity (apparatus)
(7 pts)

A

Apparatus: beaker, boiling tube, water plant, thermometer, sodium hydrogencarbonate sol (source of CO2) , water bath, lamp (e.g. 60 w bulb)

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20
Q

Experiment to find out how rate of photosynthesis is affected by light intensity (observations)
(5 points)

A
  1. Set up apparatus
  2. air bubbles are given off at cut end of plant, some time is allowed for rate of bubbling to stabilise
  3. no. of bubbles produced over period of 5 min is counted, repeated a few times to obtain average rate
  4. experiment repeated by moving light source closer to plant
  5. observed that rate of bubbling increase as distance of lamp from plant decreases
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21
Q

Light intensity as limiting factor

A

-graph: increases until saturation pt, beyond saturation pt rate of photosynthesis remains the same tho light intensity increases

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22
Q

Experiment to find out how rate of photosynthesis is affected by temperature (apparatus)
(7pts)

A

sodium hydrogencarbonate sol, water bath, thermometer, beaker, boiling tube, water plant(e.g. hydrilla), lamp (60 W bulb)

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23
Q

Experiment to find out how rate of photosynthesis is affected by temperature (steps&observation)

A
  1. Set up apparatus
  2. Ice-cold water added to water bath to keep temp at 5°c
  3. when bubbles are coming out at a regular rate, no. of bubbles produced over a period of 5 min is counted. Repeat few times to get average rate
  4. experiment repeated at several temperatures
  5. observed that rate of bubbling increases as temp increases
24
Q

Effect of increasing temperatures on enzymes involved in photosynthesis

A
  • the reactions in photosynthesis are enzyme-dependent
  • at low temps, enzymes inactive
  • at extreme temps higher than optimum temp, enzymes denature
25
Q

Effect of temperature on rate of photosynthesis graph (enzymes)
(bottom, middle, top/peak, drop)

A
  • near bottom: rate of photosynthesis slow as enzymes are less active at low temp
  • middle: rate of photosynthesis increases, enzymes more active at higher temperatures
  • top/peak: rate of photosynthesis maximum as enzymes most active at this temp (optimum)
  • drop: rate of photosynthesis slows down as enzymes denature
26
Q

Temperature as a limiting factor

A vs B (0.03% CO2 conc vs 0.13%)

A
  • when temp is increased from 20°c to 30°c°, CO2 conc constant at 0.03%, rate of photosynthesis doesn’t increase greatly so temp not important limiting factor
  • when temp increased from 20°c to 30°c, CO2 conc constant at 0.13%, rate of photosynthesis increase greatly and is a limiting factor
27
Q

Experiment to find out how rate of photosynthesis is affected by carbon dioxide conc (apparatus)

A

sodium hydrogencarbonate sol, water bath, thermometer, beaker, boiling tube, water plant, lamp (60 W bulb)

28
Q

Experiment to find out how rate of photosynthesis is affected by carbon dioxide conc (steps&observation)
(5 pts)

A
  1. set up apparatus
  2. conduct experiment at room temp
  3. diff conc of sodium hydrogencarbonate sol are used
  4. when bubbles come out at regular rate, rate of bubbling for each conc of sodium hydrogencarbonate sol is measured
  5. it is observed that rate of bubbling increases as conc of sodium hydrogencarbonate increases
29
Q

Carbon dioxide as a limiting factor

2 pts

A
  • beyond saturation pt the rate of photosynthesis remains the same tho CO2 conc increases
  • rate of photosynthesis increases when CO2 conc is raised while keeping temp constant
30
Q

What happens to glucose in leaves (in leaf)

2 pts

A
  • used immediately by plant cells for cellular respiration or to form cellulose cell walls
  • excess glucose stored in leaves
31
Q

What happens to glucose in leaves (other parts of plant)

3 pts

A
  • converted into sucrose which is transported to storage organs e.g. seeds, stem tubers, root tubers via phloem
  • converted to starch or other forms of storage compounds at the storage organs
  • might be converted back to glucose when needed
32
Q

What happens to glucose in leaves (amino acids)

3 pts

A
  • reacts with nitrates and mineral salts to form amino acids
  • combined to form proteins for synthesis of new protoplasm in the leaf
  • excess amino acids transported away for synthesis of new protoplasm or storage as proteins
33
Q

What happens to glucose in leaves (fats)

A

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

34
Q

Importance of photosynthesis

3 pts

A
  • producers in food chain
  • purify air
  • fossil fuels
35
Q

Importance of photosynthesis: Producers in food chain

3 pts

A
  • plants are producers in food chain
  • sunlight/light energy converted to chemical energy, stored in plants
  • chemical energy transferred to other organisms thru feeding
36
Q

Importance of photosynthesis: Purify Air

A

-helps to purify air by removing carbon dioxide from atmosphere and releasing oxygen as a by-product

37
Q

Importance of photosynthesis: fossil fuels

2 pts

A
  • energy in fossil fuels like coal, oil and gas come from the Sun, captured thru photosynthesis
  • burning of fossil fuels releases energy
38
Q

External features of leaf: Lamina

3 pts

A
  • also known as the leaf blade
  • large sa:v, maximum absorption of sunlight
  • large&thin, rapid diffusion of carbon dioxide to reach leaf’s inner cells
39
Q

External feature of leaf: Petiole

A

-positions the lamina for maximum absorption of sunlight and gaseous exchange

40
Q

External features of leaf: Veins

2 pts

A
  • allow transport of water and mineral salts to cells in lamina
  • transport manufactured food from the leaves to other parts of plant
41
Q

External features of leaf: Leaf arrangement

4 pts

A
  • leaves arranged in regular pattern around stem
  • ensure leaves not blocking each other from getting sunlight
  • allows each leaf to receive optimum amt of light
  • paired or alternate arrangement
42
Q

Internal features of leaf: Cuticle

A
  • waxy layer above epidermis
  • prevents excessive water loss
  • transparent, allow sunlight to penetrate to the mesophyll
43
Q

Internal features of leaf: Upper Epidermis

A

single layer of closely-packed cells

44
Q

Internal features of leaf: Palisade Mesophyll

A
  • few layers of closely-packed cells
  • cells are long & cylindrical
  • contains numerous chloroplasts for max absorption of sunlight
45
Q

Internal features of leaf: Spongy Mesophyll

A
  • Irregularly shaped cell
  • numerous large intercellular air space
  • allow rapid diffusion of gases inside leaf
  • fewer chloroplasts than palisade mesophyll
  • covered in thin film of moisture
46
Q

Internal features of leaf: Vascular bundle

A
  • contains xylem and phloem

- transport of water and food materials within plant

47
Q

Internal feature of leaf: Lower Epidermis

3 pts

A
  • single layer of closely packed cells
  • covered with outer layer of cuticle
  • many minute openings called stomata found here
48
Q

Guard cells

A
  • each stoma is surrounded by guard cells
  • guard cells control size of stomata
  • stomata open in light and close in dark
49
Q

Guard cells (Day- How water enters guard cells)

A
  • guard cells photosynthesize, chemical energy formed used to pump K+ into guard cells from neighbouring epidermal cells
  • lowers water potential of guard cells
  • water from adjacent epidermal cells enters guard cells by osmosis
50
Q 
Guard cells (Day- What happens when water enters guard cells) 
(3 pts)
A
  • guard cells swell, turgid
  • guard cells have thicker cell wall on the side of stomatal pore
  • this causes guard cells to become curved and pull the stoma open
51
Q 
Guard cells (Night)
(3 pts)
A
  • K+ ions diffuse out the guard cells
  • water potential in guard cells increases, water exits via osmosis
  • guard cells flaccid, stoma closes
52
Q

Entry of CO2 into leaf (during the day)

4 pts

A
  • CO2 rapidly used up during photosynthesis
  • CO2 conc inside leaf lower than atmospheric air, conc gradient exists
  • CO2 diffuses into leaf via stomata
  • CO2 dissolves into film of water surrounding mesophyll cells and diffuses into cells
53
Q

Entry of water into leaf

2 pts

A
  • water is brought to leaves via xylem vessels in veins

- water leaves veins and moves from cell to cell in the mesophyll via osmosis

54
Q

Describe an experiment to investigate effect of CO2 conc on rate of photosynthesis (Steps+control)
(7pts) (Practice paper question)

A
  1. set up apparatus
  2. dissolve 2-10g of sodium hydrogencarbonate in the water in the beaker (provides CO2)
  3. Place apparatus in strong sunlight for a few hours and at room temp
  4. 5 different conc of sodium hydrogencarbonate are used (5%,10%, 15%, 20%, 25%)
  5. Air bubbles are given out from cut end of plant. Allow plant to acclimatise to surroundings for about 5 min
  6. measure vol of oxygen produced using a syringe and find values for each of the CO2 conc
    Control: distilled water (sodium hydroxide, soda lime might change pH of water plant)
55
Q

Control variables when investigating effect of CO2 conc/light intensity/temperature on rate of photosynthesis (Practice paper question)
(5 pts)

A
  • Light intensity (wattage of light bulb, distance between lamp and set-up/beaker)
  • Temperature (state what temp)
  • Time for acclimatisation (5 min)
  • Mass of plant must be constant (e.g. 5g)
  • Time taken for collection of O2 (10 min)
  • Always specify vol/distance/quantity used!
56
Q

Why is there a rapid rise in water absorption in the day/morning? (practice paper question)
(3 pts)

A
  • plant uses water as raw material of photosynthesis
  • increased light intensity would cause plant to have higher rate of photosynthesis, increasing water absorption
  • stomata opening larger due to higher light intensity, increasing rate of transpiration
57
Q

Suggest why light intensity has an effect on rate of photosynthesis (practice paper question)

A
  • more light energy converted to chemical energy by chlorophyll
  • used for photolysis of water
  • greater production of oxygen gas

Sec 3 Pure Bio (16 decks)

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