photosynthesis (week 12) Flashcards
(23 cards)
what is photosynthesis?
the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen
what are the word and chemical equations for photosynthesis?
carbon dioxide + water → glucose + oxygen
6CO2+6H2O → C6H12O6+6O2
reactants and products?
reactants:
- carbon dioxide (CO2)
- energy (ATP)
water (H2O)
products:
- glucose (C6H12O6)
- oxygen (O2)
anabolic vs. catabolic processes?
anabolic: builds larger molecules from smaller ones
catabolic: breaks down molecules to release energy
photosynthesis: anabolic
autotrophs vs. heterotrophs?
autotrophs: make their own food
heterotrophs: must consume other organisms from energy
plants: autotrophs
photosynthesis: autotrophic
where does photosynthesis occur in the cell?
in the chloroplasts
chloroplast structure
they have an outer membrane and inner membrane. in the inner membrane:
- thylakoids
- granum
- lumen
- stroma
thylakoids
- flattened, disk-shaped membranes
- site of light-dependent reaction
- contains chlorophyll
granum (grana - plural)
- a stack of thylakoids
- stacking increases the surface area for light absorption
lumen
- the fluid filled space inside each thylakoid
- involved in the light-dependent reaction
stroma
- the fluid filled space surrounding the granum
- contains enzymes, DNA and ribosomes
- is the site of light independent reaction
what pigment is essential for photosynthesis? where is it found?
chlorophyl, found in thylakoid membranes
- harvests energy by absorbing certain wavelengths
- plants are green because the green wavelength is reflected
why are leaves green?
because they contain chlorophyll, which absorbs light, and reflects green light
redox reactions?
the transfer of electrons
oxidation: the loss of electrons/gain of oxygen
reduction: the gain of electrons/loss of oxygen
what are the two main stages of photosynthesis?
light dependent reaction, light independent reactions (calvin cycle)
light dependent reaction?
light energy is absorbed by chlorophyll (in thylakoid membranes)
splits water into oxygen, electrons and protons
produces ATP and NADPH, to power the next stage
light independent reaction?
carbon dioxide combines with hydrogen to form glucose
uses ATP and NADPH to do this
no light is required
occurs in the stroma
what factors affect the rate of photosynthesis?
light intensity, carbon dioxide concentration, temperature
what is the role of the stomata in photosynthesis?
they allow gas exchange (CO2 in, O2 out)
what happens to glucose produced in photosynthesis?
used for respiration, stored as starch, or used to make other molecules
what are carotenoids and what colours do they display?
pigments involved in photosynthesis that appear red or yellow
when do carotenoids become visible in deciduous trees?
they are revealed in autumn when chlorophyll breaks down, and trees store nutrients for winter
why do leaves change colour in autumn?
as chlorophyll is broken down to store nutrients, the red and yellow pigments of carotenoids become visible
