Lecture 12a Flashcards
where do we get energy from?
the sun
the chemical elements essential to life are recycled
what are the two major modes of acquiring nutrition?
1) autotrophic nutrition
2) heterotrophic nutrition
autotrophs are self feeders whereas heterotrophs are other feeders
what do photoautotrophs do?
they convert light energy (sunlight) into chemical energy (sugar) through photosynthesis
- they use c02 from the atomosphere as their source of carbon
plants, algae, cyanobacteria, purple and green sulfur bacteria
what is the order of food chain in both terrestrial and aquatic food chains?
primary producers = base of all food chains = autotrophs
what are the two types of photosynthesis?
1) oxygenic
2) anoxygenic
what are the two reactions of photosynthesis
oxygenic & anoxygenic
what are the four leaf and plant structures aiding photosynthesis?
1) mesophyll
2) stomata
3) vascular tissue (found everywhere in the plant)
4) chroloplasts
what is the structure of the leaf tissue?
- flat and thin creating a large surface area
leaf tissue consists of: - epidermis
- vascular tissue
- mesophyll
chloroplasts and stoma are smaller components within the mesophyll and epidermis
what causes the green color on leafs?
chlorophyll pigments are found in the mesophyll
how does the leaf reduce dessication?
it has a top and bottom epidermis that are coated with a waxy cuticle which helps prevent water from escaping and keeps co2 and O2 from passing through
where does gas exchange happen on the leaf?
pores on the leaf called stomata (stoma) located in the lower epidermis
what is vascular tissue?
a system of vessels to distribute substances throughout the plant
- from the root to the tip of the leaf
what is the mesophyll?
tissue composed of cells that peform photosynthesis in leaves
- contain a high amount of chloroplasts for photosynthesis
name the structures of this chloroplast
how are chloroplasts similar to the mitochondria?
they have a double membrane enclosed organelle
what is the fluid inside the inner membrane of the chloroplast called?
stroma
contains DNA and enzymes
contains internal called thylakoids
the thylakoids are stacked up to form towers called Granum
do chloroplats move?
they are non static organelles like the mitochondria - they move along the tracks of the cytoskeleton
- they have a changeable shape and pinch in two - reproducing themselved
what is a pigment?
substance that absorbs light energy
chloroplasts can convert light energy into chemical energy because they contain pigments
where are photosynthetic pigments found?
they are found embedded in the thylakoid membranes of chloroplasts
- each pigment absorbs different wavelengths of light and reflect others
what are the three types of pigments being reflected?
1) chlorophyll a
2) chlorophyll b
3) cartenoids
what is the difference between chlorophyll a and b?
a:
- key light capturing pigment
b:
- works in conjunction with chlorophyll a
both have a central atom of magnesium
what are the two parts to chlorophylls?
1) has a porphyrin ring:
light absorbing head of the molecule - magnesium is at the center
2) has a hydrocarbon tail:
interacts with the hydrophobic regions of proteins inside thylakoid membranes of chloroplasts
serves to stablilize the pigment in the thylakoid membrane
what are cartenoids?
large group of pigments that gives leaves, fruits and vegetables their **yellow-orange coloration **
- the chlorophyll is broken down in response to shorten day lengths and cold temperatures
what is the job of cartenoids?
have the job of photoprotection:
- absorb and dissipate excess light to prevent damage to the chlorophyll pigments
- prevents the formation of free radicals which could harm the cell
what is the wavelength range that photosynthesis falls under?
380nm (shorter wavelength but high energy) - 750nm (longer wavelength but lower energy)
what do we see when pigments absorb light?
we see the wavelengths reflected
what color do chlorophyll a and b absorb and reflect?
a:
absorb violet-blue and red light
reflects blue-green light
b:
absorb violet-blue and red light
reflects yellow-green light
the only color reflected by the chloroplasts main pigments is the green spectrum
what colors do carotenoids reflect and absorb?
absorb: violet and blue-green
reflect: shades of yellow and orange
what is the basis of photosynthesis?
energy transfer
the electron moves into a higher energy level
- only photons absorbed are those whose energy is exactly equal to the energy difference between the ground and excited states of a pigment molecule
what happens when the chlorophyll molecule is isolated?
- the excited electron drops back down
- absorbed energy is released as heat, vibration or light
although chlorophyll molecules are not isolated in chloroplasts
what is inductive resonance?
when the light is being transfered and the electrons are getting excited untill they reach a reaction center
- vibration energy is transferred
what is a photosystem composed of?
composed of a reaction center (electrons are excited and vibrate till they reach here) that is surrounded by several light-harvesting complexes
what is the reaction-center complex?
organized association of proteins holding a special pair of chlorophyll a molecules
how many photosystems are there?
two
photosystem II comes before photosystem I
found in thylakoid membranes of chloroplasts
what does photosynthesis convert the energy from sunlight into?
convert carbon dioxide and water into glucose and oxygen
some of the glucose produces will be used to make ATP in cellular respiration
what is carbon fixation?
when glucose is synthesized into macromolecules which are incorporated into the tissues of the plant
what gets reduced and what gets oxidized in photosynthesis?
CO2 gets reduced:
- all the carbon atoms it holds are fixed into sugar
- half of the oxygen atoms go into making sugars and the other half into making water
water gets oxidized :
- oxygen atoms are released as O2 ( gain of oxygen = oxidation )
- hydrogen atoms are transferred to form sugars
what is the difference in terms of redox reactions between photosynthesis and cellular respiration?
their redox reactions are reversed
the flow of electrons in photosynthesis is reversed
what are the two steps in photosynthesis and what do they generate?
1) light reactions:
- occurs in thylakoid membranes
- generates O2, ATP and NADPH from light energy and water
2)** calvin cycle **
- light independent reactions ( doesn’t need direct sunlight as it has enough stored ATP to use )
- occurs in the chloroplast stroma
- generates sugar molecules from ATP, NADPH, and CO2
