SB6 Flashcards
What is the formula for photosynthesis
Carbon dioxide + Water –>(energy transferred by light) Glucose + oxygen
Where does photosynthesis occur
In the chloroplasts
Palisade mesophyll
What happens to glucose molecules after they are made
They link together to form a starch polymer and stay in the chloroplasts until photosynthesis stops
It’s moved into the cytoplasm and used to make surcrose
What does sucrose do
It’s transported around the plant and used to make starch, other molecules for the plant (eg: cellulose) and glucose for respiration
Name some leaf adaptations
- Broad and flat leaves, large surface area
- Waxy cuticle
- Palisade cells near the top (packed with chloroplasts)
- Stomata allows carbon dioxide to diffuse into leaf
- Guard cells open and close stomata (water flows into guard cells making them rigid in the light)
- Thin leaves so carbon dioxide doesn’t have to diffuse far to get to cells that need it
What is gas exchange
The flow of different gases in and out across a membrane
Name the limiting factors of photosynthesis
- Carbon dioxide concentration
- Temperature
- Light intensity
What does it mean when one limiting factor doesn’t affect the rate anymore
Something else is a limiting factor
Or if it’s temperature, the temperature is too high
What is the formula for a new light intensity
Iⁿᵉʷ=(Iᵒʳᶦᵍᶦⁿᵃˡ x d²ᵒʳᶦᵍᶦⁿᵃˡ)÷d²ⁿᵉʷ
I= light intensity d= distance
Why do we use inverse square law for light intensity
Because light intensity is inversely proportional to the new distance squared
What are some control variable of the light intensity practical
- The number of algal balls
- The temperature
How can you improve the experiment (light intensity)
If the bubbles are too fast, you can measure the volume of gas using a gas syringe or a measuring cylinder
What is the water absorbed by plant roots used for
- Carrying dissolved mineral ions
- Keeping cells rigid
- Cooling the leaves
- Photosynthesis
What are root hair cells used for
They provide an extended surface area so that water and mineral ions can be absorbed, they also have thin cell walls so water can flow into the cells quickly
Describe how water can enter the root hair cells
Water enters through osmosis into the cytoplasm of the root hair cells
Water can also enter by diffusion and the water diffuses through the cell wall
How does active transport work in the root hair cell
- The concentration of mineral ions is great in the root hair cell than the soil
- Minerals cannot diffuse against this gradient
- Proteins in the membrane pump ions into the cell
What is transpiration
The flow of water into a root, up the steam and out the leaves
What are xylem vessels
Long thick tube in plants that carry water
How does transpiration work
- Unbroken chain of water held by weak intermolecular forces of attraction between water
- Water is pulled up the xylem vessels as it evaporates from the xylem vessel in the leaf
Factors that affect transpiration
Wind- moves water molecules away from the stomata
Low humidity
Higher temperatures, particles move and diffuse faster
-Greater light intensity, makes the stomata wider
How are xylem cells adapted to allow water to flow through them quickly
Thick side walls to provide support, prevent collapsing and will not burst
Dead cells, no cytoplasm to form an empty tube
Tiny pores to allow water an mineral ions to enter the xylem vessels
What is translocation
The movement of sugars throughout the plant through phloem cells (in both directions)
Name some adaptations of phloem cells
Small amount of cytoplasm for more room
Pores that can pump sucrose solution
What do spongy cells do
They do not fit well together, creating spaces that allow gases to diffuse easily
How are chloroplasts adapted
Have a lot of chlorophyll and can move away or towards light
What are epidermis cells
Form the outer layers of a leaf that are transparent and allow light to pass through easily
What does the cuticle do
It’s a waxy cuticle that prevents water loss and stop microorganisms entering the leaf
How are cacti adapted
Thick cuticle
Stomata only open at night (carbon dioxide is stored)
Spines instead of leaves (protect stem and minimise surface area)
What is tropism
Responding to a stimulus by growing towards or away from it
What is phototropism
A tropism caused by light, triggering auxins (plant hormones)
How does positive phototropism work
Auxins are produced in the shoots and cause elongation of cells, when light comes from one direction, auxins move to the shaded part of the root, triggering them to elongate to the light
What is gravitropism
Growth in the direction of gravity that helps a root reach moisture underground
What does gibberellins do
It helps germinate seeds and start to grow shoots and roots
Can be used to make bigger fruit
What does ethene gas do
It helps fruit ripen
What are selective weedkillers and what do they do
They contain auxins that kill plants with broads leaves but not narrow leaves
Farmers can use these to kill weeds without affecting a crop
What is photoperiodism
The response an organism has after a specific number of daylight hours
What is germination
The process in which a seed turns into a new young plant
