Unit 6 markscheme bingo Flashcards
(40 cards)
1
Q
photosynthesis
A
- A chemical reaction
- In photosynthetic organisms (plants, algae, bacteria)
- Light energy converted to chemical energy
- In chloroplasts
- Facilitated by the pigment chlorophyll
Endothermic reaction (absorbs energy)
2
Q
Importance of photosynthesis
A
- Produces glucose
- Substrate for respiration: energy released from it
- Stored as starch: converted back when plant needs energy
- Converted into complex organic molecules = growth = increased biomass
- All organisms require the carbon fixed in photosynthesis to produce their biomass
- Produces oxygen
Used for aerobic respiration
3
Q
Equation for photosynthesis
A
- Word: carbon dioxide + water -> glucose + oxygen
Symbol: 6CO2 + 6H2O -> C6H12O6+ 6O2
4
Q
Factors affecting photosynthesis [limiting factors]
A
- Temperature
- Light intensity
- Carbon dioxide concentration
5
Q
Temperature and Photosynthesis
A
- Increase temp = more KE for enzymes in photosynthesis = more collisions = rate increases
- Optimum temp = 25C
Too high = enzymes denature; rate of photosynthesis decreases
6
Q
Light Intensity and Photosynthesis
A
- Directly proportional to each other
- Eventually plateaus
Another factor becomes limiting (eg: temp or CO2 conc)
7
Q
Measuring Photosynthesis and Light Intensity
A
- Use light meter
- Inverse square law
- light intensity = 1/distance^2
- Inversely proportional: as distance from light source increases, rate of photosynthesis decreases
8
Q
Carbon Dioxide Concentration and Photosynthesis
A
- Directly proportional to each other
- Eventually plateaus
Another factor becomes limiting (eg: temp or light intensity)
9
Q
Plants and Water
A
- Photosynthesis
- Maintenance of structure (turgidity)
Cooling effect (transpiration)
10
Q
Plant and Mineral Ions
A
- Growth
- fertilisers contain nitrates, potassium and phosphates
Nitrates important in amino acid and protein production
11
Q
Root Hair Cells
A
- Function: uptake of water and minerals
- Mineral transport:
- Lower conc of mineral ions in soil than root
- Active transport of minerals into the root
- Water transport:
- Active transport of minerals into the root lowers water concentration in the root
Water moves via osmosis into the root, down the water concentration gradient
12
Q
Adaptations of Plant Roots
A
- Contain millions of root hair cells:
- Long hairs - increases S.A for absorption
- Many mitochondria = large amounts of ATP/energy released = required active transport of mineral ions (e.g. Nitrates)
13
Q
Transpiration
A
- Transport of water and dissolved mineral ions through the xylem
- From roots to leaves (one-way)
14
Q
Transpiration Stream
A
- Water evaporates from mesophyll cell
- Water diffuses out of stomata
- Water molecules drawn from xylem vessels to replace lost water in spongy mesophyll
- Water molecules drawn up xylem to replace those lost at the xylem
- More water molecules absorbed by root hair cells
15
Q
Adaptations of Xylem
A
- Composed of dead cells laid end-to-end to form a long, hollow, continuous column
- No end walls = little resistance to water flow
- Cell wall + lignin = strength + support
16
Q
Stomata
A
- Tiny pores on surface of plant, important in gas exchange
- Surrounded by guard cells
17
Q
Guard cells and stomata size
A
- Open:
- Water enters guard cells
- Swell -> turgid
- Bend and draw away from each other -> stomata opens
- Occurs in high light conditions
- Close:
- Water leaves guard cells
- Shrink -> flaccid
- Closes stomata
- Occurs in low light conditions
18
Q
Factors affecting transpiration rate (3)
A
- Light intensity
- Temperature
- Air movement
19
Q
Light intensity and Transpiration Rate
A
- High light intensity
- more stomata open (more gas exchange for photosynthesis)
- increased diffusion of water vapour out the stomata
- Increased transpiration rate
- Rate of photosynthesis increases
- high water uptake from xylem
- Increased transpiration rate
- Low light intensity = fewer stomata open + decreased photosynthesis = lower transpiration rate.
20
Q
Temperature and Transpiration Rate
A
- High temp
- high KE of water
- increased rate of evaporation and diffusion of water vapour out of stomata
- increased transpiration
- Rate of photosynthesis increases
- high water uptake from xylem
increased transpiration
21
Q
Air Movement and Transpiration Rate
A
- High air movement
- Moves water vapour away from stomata
- Decreased water vapour concentration around stomata
- Increased rate of diffusion of water vapour out of stomata
- Increased transpiration rate
22
Q
Measuring Transpiration Rate
A
- Potometer
- Rate of transpiration = rate of water uptake = distance moved by bubble/time taken
23
Q
Translocation
A
- Transportation of sugars (sucrose) up and down stem
- In the phloem
- Requires energy
24
Q
Adaptations of Phloem
A
- Sieve tube elements
- Long and thin
- Laid end-to-end with end plates = enable sugar flow
- No nucleus, little cytoplasm = sugar flow easily
- Companion cells
- Dense cytoplasm
- Nucleus
- Mitochondria (provide energy for processes)
25
Leaf Adaptations for Photosynthesis
* Broad
- Large S.A for light absorption
* Thin
- Small diffusion distance for gas exchange
- Light reaches all cell
* Xylem and phloem [vascular bundles]
- form a network to deliver water and remove glucose
* Chloroplasts
- Chlorophyll
- Light absorption
26
Leaf Cell Adaptations for Photosynthesis
* Palisade mesophyll layer
- Close to the surface
- Receives most light
- Greatest chloroplast density
* Upper epidermis
- transparent
- allows light to reach palisade layer
* Spongy mesophyll layer
- air spaces
- high rate of diffusion
* Lower epidermis
- many stomata
- gas exchange + transpiration
27
Plants Adaptation to Low Water Environments
* Small leaves
- less SA for water loss
* Spines
- Decrease consumption
- Trap humid layer of air around the plant
* Thick waxy cuticle
- reduces water loss from evaporation
* Thick, fleshy stem
- water storage
* Shallow, widespread roots
- Large SA for water absorption
* Stomata sunken in pits/curled leaves
- Trap humid layer around stomata
* Stomata ability to close
- Reduce water vapour diffusion out the leaf
28
Plant tropisms
* Growth of a plant in response to a stimulus
- Positive tropism = towards stimulus
- Negative tropism = away from stimulus
29
Auxins
* Plant hormones involved in tropisms
- Control growth in roots and shoots tips
- Stimulate = shoots
- Inhibit (restrict) = roots
- Move around the plant by diffusion (in solution)
30
Phototropism
* Growth response of a plant to light
- Shoots = positively phototropic
- Roots = negatively phototropic
31
Positive Phototropism
* Shoot tip exposed to light
* Auxin accumulates on shaded side
* Auxin promotes cell elongation on shaded side
* Shoot tip bends towards light
32
Negative Phototropism
* Root exposed to light
* Auxin accumulates on shaded side
* Inhibition of elongation on shaded side
* Root tip grows away from light
33
Gravitropism
* Growth response of a plant to gravity
- Shoots = negatively gravitropic
- Roots = positively gravitropic
34
Negative Gravitropism
* Shoot horizontal
* Gravity = auxin accumulates on lower side of shoot
* Auxin promotes cell elongation on lower side
* Shoot bends upwards = away from gravity
35
Positive Gravitropism
* Root horizontal
* Gravity = auxin accumulates on lower side of root
* Inhibition of elongation on lower side
* Root bends downwards = towards gravity
36
Benefits of Tropisms
* Enable plants to respond to environment
* Shoot growth
- Increased light
- Increased rate of photosynthesis
* Root growth
- maximises water/mineral uptake
- support of plant (anchorage)
37
Auxins in Commercial Plant Cultivation
* Rooting powders
- auxins stimulate growth of roots in cuttings
- rapid cloning
* Weed-killers
- target and alter growth patterns in weeds to kill them (over-growth)
- Increased yield in commercial crops
38
Gibberellins in Plant Cultivation
* Gibberellins: plant hormones for germination and flowering
- Initiate germination in seeds at unnatural times of year
- Ensure all seeds germinate at the same time
* Produces seedless fruit
- stimulating fruit growth from unpollinated flowers
* Reduce flower formation
- Improves fruit size
39
Gibberellins Mechanism of Action
* Gibberellins: plant hormones for germination and flowering
- Initiate germination in seeds at unnatural times of year
- Ensure all seeds germinate at the same time
* Produces seedless fruit
- stimulating fruit growth from unpollinated flowers
* Reduce flower formation
Improves fruit size
40
Ethene in commercial plant cultivation
* Stimulates enzymes controlling fruit ripening
* Enables unripe fruits to be picked and become ripened during transport
