Test 23/9/21 Flashcards
cornea
A curved transparent disc at the front of the eye. Does most of the focussing.
pupil
A circular opening whose size is controlled by the Iris.
lens
It is soft, flexible and transparent. Its shape can be changed to fine tune the focussing of light onto the retina
ciliary muscles
A ring of muscle at the edge of the eye which circles the lens. When it relaxes, the lens gets thinner. When it contracts, the lens gets fatter.
suspensory ligament
Strong fibres which attach the lens to the ciliary muscle
retina
Contains light sensitive cells called rods and cones
optic nerve
Consists of many neurones which carry impulses from the retina to the brain
fovea
The region of the retina with the greatest number of cones
conjunctivia
A mucous membrane that covers the eye to prevent infection
Dim light eyes
Radial muscles contract
Circular muscles relax
Iris narrower
Pupil dilates
Bright light eye
Radial muscles relax
Circular muscles contract
Iris wider
Pupil constricts
Photosynthesis word and symbol equation
Carbon dioxide + water —> glucose + oxygen
6CO2 + 6H2O —> C6H12O6 + 6O2
How does carbon dioxide affect the rate of photosynthesis?
More carbon dioxide = faster reaction
As there are more molecules to collide with enzymes
However, it will reach a point when adding more carbon dioxide has no effect, there is a lack of energy
How does light intensity affect the rate of photosynthesis?
Brighter light = increased rate of photosynthesis
As there is more energy for the reaction to occur
This doesn’t last forever, as at high light intensities, a different factor is limiting and the graph levels off
How does temperature increase the rate of photosynthesis?
Increasing temperature = faster reaction
Enzymes and substrates have more kinetic energy and collide more often
However, at too high temperatures, photosynthesis decreases and the reaction stops
This is because the enzymes carrying out this stage of the photosynthesis have been denatured
MAGNESIUM (Mg)
Use by plant
Symptoms of deficiency
To make chlorophyll
Yellow leaves
NITRATES (NO3-)
Use by plant
Symptoms of deficiency
Amino acids (therefore proteins) Nucleic acids (DNA and RNA)
Stunted growth
PHOSPHATES (PO43-)
Use by plant
Symptoms of deficiency
Nucleic acids (RNA and DNA)
Poor root growth
Purple younger leaves
What happens to the eye when focusing on a far away object?
Relaxing ciliary muscles
Meaning suspensory ligaments are pulled tight
Lens is pulled thin and has a less convex shape
Therefore less refraction of light
What happens to the eye when focussing on an object close up?
Contracting the ciliary muscles
Meaning suspenseful ligaments are therefore slack
Lens is not stretched out so becomes thicker with more convex shape
Therefore more refraction of light
How is the leaf specially adapted for photosynthesis?
Surface area and thickness
The leaf has a large surface area and is thin, to maximise absorption of sunlight by the photosynthetic sells, it also increases the number of stomata, so thatthe carbon dioxide can diffuse quicker
How is the leaf specially adapted for photosynthesis?
Upper epidermis
The upper epidermis is transparent allowing light to penetrate to the mesophyll
How is the leaf specially adapted for photosynthesis?
Palisade cells
The palisade cells are long, thin and tightly packed
they contain large numbers of chloroplasts
this maximises the absorption of sunlight energy
the palisade mesophyll is the main site of the photosynthesis
How is the leaf specially adapted for photosynthesis?
Stomata
The stomata allows gases to diffuse into the air spaces of the leaf
this provides a short diffusion distance for carbon dioxide
How is the leaf specially adapted for photosynthesis?
Xylem
The xylem transports water into the leaves
this then provides a short diffusion distance for water to diffuse into the photosynthesis cells
How is the leaf specially adapted for photosynthesis?
Phloem
The phloem vessels transport sugars made in photosynthesis to other parts of the plant
