Reactions in Plants
What is the chemical formula for glucose?
C6H12O6
What cells control the opening and closing of stomata?
guard cells
What is the test for glucose?
Benedict's Reagent
What is yield?
the amount of useful product harvested from a crop
What is another name for burning?
combustion
What do phloem and xylem vessels each transport?
phloem: glucose
xylem: water & minerals
What is diffusion?
when particles move without anything moving them (from a high to a low concentration)
What is a polymer? Name one example
a molecule made of repeating units (monomers)
e.g. starch, cellulose
What type of pesticide kills weeds?
herbicide
What is the name of the process whereby plants and animals release carbon dioxide?
respiration (aerobic respiration)
The energy released from glucose during aerobic respiration transfers to what molecule?
ATP
Why do stomata close at night?
to reduce water loss (due to transpiration)
Why are lipids present in the cuticle of a leaf?
Lipids are insoluble in water; they make the leaf waterproof
What is selective breeding?
when humans choose an organism that has a certain characteristic and breed more of these organisms so the characteristic is more obvious
What is biomagnification?
the increase in toxin concentration in organisms higher up a food chain
What is a limiting factor?
a variable that affects the rate of a reaction (can slow down the rate of the reaction)
Name THREE things plants need water for
-- photosynthesis
-- keeping leaves cool
-- filling up cells to keep their shape
Why do plants need nitrates? (nitrogen)
Nitrates combine with glucose to form amino acids, which are the building blocks of proteins
Name FOUR ways farmers can increase their yield
increase space; efficiency (machines); greenhouses; fertilisers; pesticides; breeding varieties; selective breeding
What can happen to the biodiversity of an area if changes (like environmental changes) happen too quickly? Name TWO things
-- species can decline or die out
-- food webs are affected
-- habitats destroyed (etc.)
Under what conditions do photosynthesis and aerobic respiration occur, respectively?
Photosynthesis
-- only when there is light
-- green parts of a plant
Aerobic respiration:
-- occurs all the time
-- all cells
Name two adaptations of leaves for absorbing light
-- broad (wide) and flat with a large surface area
-- thin to allow light through the layers
-- arranged so the top leaves don’t shade lower leaves too much
Explain how starch is formed, starting from sunlight shining on a plant
Sunlight drives photosynthesis (with water & carbon dioxide)
Photosynthesis produces excess glucose (& oxygen)
Many glucose molecules join together to form starch
Starch is stored inside the plant cells
Why is manure put down before seeds are planted, whereas artificial fertiliser is put on after the plants have grown?
Manure: takes time for decomposers to break down into nutrients
Artificial fertiliser: dissolves in water immediately and can be absorbed by roots
Explain how fertiliser on a field can lead to fish dying in a river
Excess nutrients (nitrates & phosphates) enter water from fertilisers
Algae grows (algal bloom) and blocks sunlight → underwater plants die
Decomposers (bacteria) use oxygen to break down dead organisms
Amount of oxygen decreases → fish & other aquatic organisms die