Module 5 - Energy for biological processes

What is the relationship between photosynthesis and respiration?

photosynthesis captures light energy to make glucose from carbon dioxide and water where cellular respiration breaks down respiratory substances like glucose releasing energy that is temporarily stored in the form of ATP
products of photosynthesis, glucose and oxygen can be used as reactants in respiration to synthesis ATP + products of respiration carbon dioxide and water can be used as reactants in photosynthesis

What are the three main stages of photosynthesis?

capturing light energy - done by pigments such as chlorophyll
light-dependent stage - light energy is converted into chemical energy
light-independent stage - when sugars and other organic molecules are produced

What is the importance of photosynthesis?

photosynthesis light energy from sun transformed into chemical energy used to synthesize large organic molecules from inorganic substances where both photoautotrophs and heterotrophs release chemical potential energy in complex organic molecules made in photosynthesis in respiration where also can use oxygen for aerobic respiration
once earths atmosphere contained free oxygen organisms evolved that could use oxygen for aerobic respiration which releases carbon dioxide back into atmosphere and produces water

What is the compensation point?

plants respire all the time but only photosynthesise in daylight where light intensity has to be sufficient to allow photosynthesis at a rate that replenishes carbohydrates stores used up in respiration
when respiration and photosynthesis proceed at the same rate so no net gain or loss of carbohydrates plant is at its compensation point where time takes to reach point compensation period where shade plants have shorter compensation period than sun plants which require higher light intensity to reach optimum rate of photosynthesis

What is the function of chloroplasts?

site of photosynthesis where found in mesophyll tissue of leaves mainly with the main role to absorb light energy to drive photosynthesis + convert light energy into chemical energy

What is the structure of a chlorplast?

surrounded by double membrane
thylakoids - flattened sacs containing complexes of pigments like chlorophyll in membranes to absorb light for the light-dependent reaction
grana - stacks of thylakoids
lamellae - membranous extensions that connect thylakoids
stroma - fluid surrounding thylakoids where light-independent reaction occurs
starch grains - store sugars + ribosomes - protein synthesis within the chloroplast
chloroplast DNA - has genes that code for proteins involved in photosynthesis

What are photosynthetic pigments?

plants contain different photosynthetic pigments that can absorb energy from light where the absorption spectrum shows that range of wavelengths absorbed by pigments in a chloroplast

What are the 3 main photosynthetic pigments you need to know?

chlorophyll a - main pigment which absorbs red and blue light and reflects green light so most plants look green
chlorophyll b - accessory pigment most found within chlorphyll a in light-harvesting complexes
xanthophylls + carotenoids - absorb different wavelengths than chlorophyll broadening spectrum of light that can drive photosynthesis

What are photosystems and how do they work?

chloroplasts contain clusters of pigments called photosystems embedded in the thylakoid membranes
the light-harvesting system absorbs light energy where this energy is transferred to reaction centre where reaction system than emits high-energy electrons to drive the light-dependent reactions

What does a photosystem contain?

a light-harvesting system which contains pigments like chlorophyll a + b and carotenoids
a reaction centre which contains two chlorophyll a molecules

How can chromatography be used?

can separate and identify different photosynthetic pigments found in chloroplasts and works as each type of pigment travels different distance up chromatography paper where the Rf value allows us to identify pigments as each pigment has characteristic Rf value
calculated by distance travelled by pigments from origin / distance travelled by solvent from origin