CHAPTER 10 AP BIO

THE PROCESS THAT FEEDS THE BIOSPHERE

Life on earth is solar powered

Photosynthesis nourishes almost the entire living world directly or indirectly.

Autotrophs are “self-feeder”

autotrophs as the producers of the biosphere.

Photoautotrophs are organisms that use light as source of energy to synthesize organic substances.

Heterotrophs pbtain organic material by the second major mode of nutrition.

decomposers→ entities thatr consumes carcasses, feces and fallen leaves.

PHOTOSYNTHESIS CONVERTS LIGHT ENERGY TO THE CHEMICAL ENERGY OF FOOD.

the original chloroplast was a photosynthetic prokaryote.

CHLOROPLASTS: THE SITES OF THE PHOTOSYNTHESIS IN PLANTS.

leaves are the major sites of photosynthesis.

Half a million chloroplasts are present within a chunk of leaf.

Chloroplasts are found inside mesophylls the tissue interior of the leaf.

dioxide enters the leaf and oxygen exit.

STOMATA mouth+ and singular

chloroplast is surrounded by membranes a dense fluid called stroma.

Thylakoyds which segregate the stroma from the thylakoid space.

Thylakoid sacs are sracked in columns called grana.

Chlorophyll resides within the thylakoid membranes of the chloroplasts.

TRACKING ATOMS THROUGH PHOTOSYNTHESIS: SCIENTIFIC INQUIRY.

6CO2+12H20+LIGHT ENERGY→C6H12O6+6O2+6H2O

photosynthesis is the reverse of cellular espiration

THE SPLITTING OF WATER.

O2 given off byplants is derived from H2O and not from CO2

THE TWO STAGES OF PHOTOSYNTHESIS: A PREVIEW

light reactions and calvin ccle

O2 is byproduct

Nadp_>NADPH

photophosphorylation ATP to Adp

incorporation of carbnon into organic compunds is called carbon fixation.

CALVIN CYCLE=DARK REACTIONS

Cavin cycle ocurrs in stroma

THE NATURE OF SUNLIGHT

light = electromagnetic raditaiton.

distance between ccrests of electromagnetic waves is called wavelength.

range of radiation = electromagnetic spectrum

380nm to 750nm most important to live = visible light

The shorter the wavelength the greaer the energy of each photon of that light.

PHOTOSYNTHETIC PIGMENTS: THE LIGHT RECEPTORS

Substances that absorb visible light are known as pigments.

if a pigment absorbas all wavelenghts is dark

If it doesnt absirb any its white.

Spectrophotometer -aparatues used to measure the ability o f a pigment to absorb different wavelengths.

Chlorophyll a→key light capturing pigment

Chlorophyll B→ accesory with the carotenoids

Carotenoids are hydrocarbons that are various shades of yellow and orange because they absbord violatet and blue-green light.

Photoprotection→ absorbs and dissiate excessive light energy that would otherwise damage chlorophyll or interact with oxygen.

Phytochemicals

are naturally occurring compounds found in plants that contribute to their color, flavor, and disease resistance. They have been shown to provide various health benefits in humans, including antioxidant properties and potential anti-inflammatory effects.

EXCITATION OF CHLOROPHYLL BY LIGHT

electron igment molecule is said to be in its ground state

A PHOTOSYSTE: A REACTION-CENTER COMPLEX ASSOCIATED WITH LIGHT-HARVESTING COMPLEXES.

A photosystem is composed of a reaction-center complex surrounded by several light-harvesting complexex.

Proimary electron acceptor

Photosystem II and Photosystem I they are named in order of discovery but actuallyt photosystem II comes firsst.

Photosystem II→P680 while phOTOSYSTEM I → p700

LINEAR ELECTRON FLOW

light drives the syntehsis of ATP and NADPH

flow of electrons through ther photosystem =s is alled linear electron flow.

CYCLIC ELECTRON FLOW

Only uses photosystem I but no photosystem II.

pHTOSYNTHETIC bacteria are known to have a single photoystem related to either PSII OR PSI

is considered an evolutionary leftover

mutant plants are not able to carry out cyclic electron flow are capable of growing well in lo light, but do not grow well where light is intense.

A COOMPARISON OF CHEMIOSMOSIS IN CHLOROPLASTS AND MITOCHONDRIA

Mitochondria use chemiosmosis to rtansfer chemical energy while chloroplasts use light energy into chemical energy in atp.

THE CALVIN CYCLE USES THE CEHMICAL EERGY OF ATP AND NADH TO REDUCE CO2 TO SUGAR

citric acid cycle is catabolic

Calvin cycle is anabolic

it produces glyceraldehyde 3 phosphate or G3P

the cycle must take place three times fixing three molecules of CO2 for one G3P molecule.

Phases→

Carbon fixation→incorporates co2 molecules attaching it at a five carbon sugar named ribulose or RuBP

Reduction thr

three molecules of co2 equakll six molecules of G3P formed.

cycle begins with 15 carbons and finishes with 18 carbons.

G3P cpnsumes 9 ATP and 6 NADPH

ALTERNATIVE MECHANISMS OF CARBON FIXATION HAVE EVOLVED IN HOT, ARID CLIMATES

PHOTORESPIRATION: AN EVOLUTIONARY RE;IC?

C3 plants are called tat because the first product is a three carbon compund.

Rubisco is capable of binding co2

PHOTORESPIRATION→ because it occurs in light and consumes O2 while producing CO2, this uses ATP and decreases photosynthetic output.

This was created when the atmosphere was mostly co2 and less O2.

NOW IT PLays hthe role of protector neutralizing otherwise damaging products of the light reactions.

it drains 50% of co2 stored.

C4 PLANTS → named that way because they produc3e a 4 carbon compund.

They are chracterized by a bundle sheath cells anbd mesophyll cellss.

Bundle sheath are arranged packed in shesaths around the veins of the leaf.

PEP carboxylase binds co2 instead of Rubisco.

C4 overcome heat and arid conditions by concentrating co2 in the bundle sheat cells at the cost of ATP.

CAM PLANTS

these plants stomata open during the night and close during the day

It prevents water lose and co2 from entering the leaves.

The mesophyll cells store the acids they make during the night until orning.

THE IMPORTANCE OF PHOTOSYNTHESIS A REVIEW

about 50% of the organic material made by photosynthesis is consumed as fuel for cellular respiration in plant cell mitochondria.

Phtosynthesis makes an estimated 150 billion metric tons of carbohydrate per year.