IB Biology HL Photosynthesis

Photosynthesis

The conversion of light energy into chemical energy in plants, to generate an organic molecule (glucose) by CO2 and H2O

What produces oxygen in photosynthesis?

Photolysis

Impacts of photosynthesis on Atmosphere:

• decreased methane due to high oxygen by photosynthesis (oxidation)

• decreased CO2 due to absorption

• decrased greenhouse gases - decreased temperatures

Light Dependent Reactions (LDR)

Uses light energy to produce ATP and to split water molecules into H+ ions

How did photosynthesis in early life forms change Early Earth?

• photosynthetic prokaryotes carried it out

• increased oxygen in oceans (algae) stimulating sea life

• decreased methane due to oxidation

• decreased CO2

What reaction occurs in the stroma?

Calvin cycle

Light Independent Reactions (LIR)

Calvin Cycle, uses ATP and H+ ions to 'fix' carbon dioxide. makes glucose

Condensation Reaction

The process where monosaccharides are combined to make carbohydrates

Pigment

Absorbs useful wavelengths of light that contain energy appropriate for photolysis in light dependent reactions

Chlorophyll

A chemical pigment that changes the color of reflected light stored in chloroplasts

Action Spectrum

Indicates which wavelengths of light can be used by a plant for photosynthesis

Absorption Spectrum

The spectrum used to measure absorption where various wavelengths of light represent different colors of light

Photolysis

The splitting or decomposition of a chemical compound by means of light energy or photons

Biomass

The total mass of all living material in a specific area, habitat, or region

Chloroplast

Plastid organelle containing chlorophyll and other pigments

Stroma

A thick fluid between grana where various enzymes, molecules, and ions are found, and where the light independent reaction of photosynthesis occurs

Thylakoid

A disk-like structure in the chloroplast that contains chlorophyll and is where the light dependent reaction occurs

Grana

A stack of thylakoids within the chloroplast of plant cells

Non-cyclic Photophosphorylation

light dependent, an electron donor is required, oxygen is produced as a waste product. It consists of two photoreactions, resulting in the synthesis of ATP and NADPH

Cyclic Photophosphorylation

an electron is excited by light and is used to transform ADP into ATP. The same electron can be used to repeat the process

Photosystem I

makes use of light to transfer electrons and whose reaction center chlorophyll is P700

Photosystem II

absorbs light for use to drive the oxidation of water and the reduction of plastoquinone, and whose reaction center chlorophyll is P680

Photoactivation

The initial stage of photosynthesis in chlorophyll molecules where the presence of light energy raises the total energy

Chemiosmosis

The movement of ions from an area of high concentration to an area of low concentration through transport proteins to create a concentration gradient

Ribulose Biphosphate

(RuBP) A 5 carbon sugar found in the Calvin Cycle

Glycerate-3-phosphate

(G3P) A phosphorylated three-carbon sugar that is an intermediate in the Calvin Cycle

Triose Phosphate

(TP) A compound derived from G3P in the light independent reaction and will be used to create glucose

Adenosine Triphosphate

(ATP) An organic compound composed of adenosine and 3 phosphates and is the energy molecule for the cell

Limiting Factor

A factor present in an environment that controls a process

NADP+

Nicotinamide adenine dinucleotide phosphate - reduced to NADPH in the light dependent reaction of photosynthesis

NADPH

Formed from NADP+ and is a reducing agent in the reactions of the Calvin cycle.

Rubisco carboxylase

Used in the Calvin Cycle to fix carbon dioxide by adding it to RuBP

PEP (phosphenol pyruvate)

assists Rubisco in fixing CO2 when less affinity occurs in the protein due to a high O2 concentration

Rubisco Enzyme

most abundant protein on Earth (50% of plant components are this)

Describe a structure thatenable maximum absorption of light:

• multiple granum stacks

• increased SA for photosystems

Uses of hexose sugars by plants:

• respiration to produce ATP

• conversion into cellulose for cell wall

• conversion into starch for storage

• conversion into sucrose for transporation (phoelm)

Why is it important that not all TP is converted into usable products?

• 5/6 needed for regenration of RuBp

• to allow carbon fixation and Calvin cycle to continue