6: Plant Structures + Functions - YK Flashcards
(21 cards)
How do plants and algae (a type of protist) make energy?
Energy from the sun is trapped in chlorophyll in the cells of the organism, then transferred into molecules of glucose (a sugar) through photosynthesis, plants can store energy in glucose and use this energy
What is biomass?
The material in an organism; plants and algae produce their own biomass (making them producers in food chains)
What is the reaction happening during photosynthesis?
carbon dioxide + water (+ energy transferred by light) –> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2
endothermic reaction
Where does photosynthesis occur in a cell?
The chloroplasts
Why is glucose turned into starch?
Glucose molecules can be linked together to form starch (a polymer), the starch stays in chloroplasts until photosynthesis stops, when it can be broken down into simpler substances which can be moved into cytoplasm to make sucrose
What is the function of sucrose in a plant?
Sucrose is transported around the plant, it can be used to make: starch (in storage organs like a potato), other molecules for the plant (cellulose, lipids, proteins), glucose for respiration (to release energy)
What adaptations do leaves have?
- Broad and flat to increase surface area so the chloroplasts in the palisade cells (near the top of the leaf) can absorb more light
- Microscopic pores (stomata) on their underside which allow carbon dioxide to diffuse into the leaf (for photosynthesis) and water vapour and oxygen to diffuse out
- Thin so carbon dioxide doesn’t have far to diffuse into the leaf before reaching the cells that need it
How are stomata controlled?
The openings are surrounded by guard cells which become swollen and rigid during the day as water flows into the cells (forming a gap between the cells), then losing the water at night causing the gap to close
What factors affect photosynthesis?
Concentration of carbon dioxide molecules (decreases with altitude)
Temperature (enzymes catalysing reactions in photosynthesis work better at warm temperatures)
Light intensity (light provides energy needed for photosynthesis)
What are limiting factors?
A factor that prevents a rate from increasing, maximum rate (of photosynthesis) is controlled by the factor in shortest supply
What does the inverse square law calculate and what is its formula?
Calculates new light intensity from original light intensity and distance and new distance, light intensity is inversely proportional to distance squared
new L = (orig L * orig D^2)/new D^2
What is the water absorbed by plant roots used for?
Carrying dissolved mineral ions, keeping cells rigid (stops wilting), cooling leaves (when it evaporates), photosynthesis
What is a root hair cell?
The cell which covers the surface of many roots to provide a large surface area so that water and mineral ions can be quickly absorbed (hairs have thin cell walls so that the flow of water is not slowed)
Where does diffusion occur in a plant?
Inside plant roots (water through open structures in cell walls), in leaves (gases diffuse in and out)
Where does osmosis occur in a plant?
Water passes into root hair cells (then tiny tubes join the cytoplasm of some cells so water can diffuse)
Where does active transport occur in a plant?
Mineral salts (natural ionic compounds) are pumped into root hair cells by proteins in the cell membrane (ions from the compounds needed, e.g. nitrate ions for protein synthesis)
What is transpiration?
The flow of water into a root, up the stem, and out of the leaves (evaporation keeps the leaves cool and helps move water + dissolved mineral ions up the plant)
What does xylem do?
Xylem vessels form tiny continuous pipes from roots to leaves with an unbroken chain of water (due to weak forces of attraction between molecules), water is pulled up xylem vessels in the stem as water evaporates from vessels in the leaves, water evaporates from xylem to the leaves as water diffuses out of the leaves
What factors affect the rate of transpiration?
Wind (moves water molecules away from stomata), humidity (water vapour in air decreases diffusion), temperature (diffusion increases with particle speed), light intensity (more light makes stomata widen)
How are xylem formed and structured?
During development xylem cells die and their top and bottom cell walls disintegrate, creating long empty vessels/tubes for water, the vessels are rigid because of the thick side walls and rings of hard lignin (prevents water pressure from bursting/collapsing vessels and supports the plant)
What is phloem?
The sieve tubes of phloem tissue translocate (transport) sucrose (made from glucose and starch from photosynthesis), the central channel of each sieve cell is connected to its neighbours by holes for the sucrose solution, companion cells pump sucrose into or out of the sieve cells (as it is pumped in, increased pressure causes the solution to flow up to growing shoots or down to storage organs)
