Photosynthesis and respiration ( module 5)

Where does photosynthesis occur

Chloroplast

why do plants need energy?

biological processes like photosynthesis, active transport, DNA replication and cell divison

plant would die without these processes

why do organisms need energy

DNA replication, Cell division

organism would die without processes

what are the 2 types of respiration

Anaerobic → Without Oxygen

Aerobic → With Oxygen

what properties make ATP a good energy source ?

Small, soluble molecule → easily transported around the cell

Easily broken down → energy can be released

ATP cant pass out the cell → cell always has a energy supply

where are Photosynthetic pigments located?

Thylakoid membrane

they are attached to a protein this forms a photosystem

Function of photosynthetic pigments

absorb the light energy needed for photosynthesis

Example of Photosynthetic pigments

chlorophyll a

chlorophyll b

carotene

what organism are autotrophs ?

Plants and Cyanobacteria

what type of organisms are plants

photoautotrophs

what does photoautotrophs mean?

use energy from light to form organic molecules

what does autotrophs mean

organisms that can take inorganic molecules and build them up into organic molecules

what organisms are heterotrophs ?

animals and fungi

what does heterotrophs mean

organisms that cant synthesise organic molecules

where do light dependent reactions happen?

Thylakoid membrane due to the photo pigments

where do light interdependent reactions occur?

stroma

what type of membrane is the thylakoid membrane

Phospholipid bilayer which is hydrophobic so ions cant enter

what type of ribosomes do Chloroplast contain

70s

what evidence is there that the chloroplast were once prokaryotic cells

they contain 70s ribosomes

what are the two types of photosystems

PSI

PSII

what do Photosystems have located in there centre

Chloroplast

why plant leaves green?

chlorophyll reflects green light

what ions does Chlorophyll A contain

Mg and NO₃⁻ ( nitrate)

what happens if a plant lacks mg or nitrates

reduces the amount of chlorophyll → causes chlorosis → yellow colour → less photosynthesis

method to investigating the pigment in leaves

1)Grind up green leaves with anhydrous sodium sulphate then add drops of propanone

2) Transfer to test tube add petroleum ether, gently shake tube → forms two layers , top layer is the pigment

3) transfer top layer liquid into a second test tube with anhydrous sodium sulphate

4) draw a line with a pencil ( bottom of paper), add spot to the line

5) dry and repeat

what does a absorption spectrum show?

Wavelengths of light absorbed by each pigment

what does a action spectrum show

Overall rate of photosynthesis at each wavelength of light

equipment to produce a action spectrum

O₂ / time taken = rate of photosynthesis

what is the method to producing a absorption spectrum

shine light through a filter

shine through a colorimeter ( set to zero absorbance with distilled water)

measure the absorption

relationship between rates of photosynthesis and absorption of pigments

strong correlation → High rates of absorption = high rates of photosynthesis

differences between PSI and PSII

PSII contains chlorophyll a which absorbs shorter wavelengths of light ( 680 nm)

PSI absorbs longer wavelengths ( 700nm)

Risk assessment for TLC experiment

Chromatography solvent are toxic and highly flammable

Wears goggles

why does the pigment separate during TLC

pigments have different solubilities

state a material that can be used as the stationary phase in TLC

Silica

why should you do step 1 and 2 of TLC quickly or in a fume cupboard

Prevents the solvent from evaporating

structure of thylakoid membrane

adaptations of the Thylakoid membrane

Large Sa : Vol ratio

what are the 2 stages of photosynthesis

The light - dependent reaction

The Light- Independent reaction ( The Calvin cycle)

Oxidation definition

losing e⁻ / loses Hydrogen

Reduction definition

gain e⁻/ gains Hydrogen

what are the 2 components of the LDP

Cyclic photo phosphorylation ( CPP)

Non cyclic photo phosphorylation ( Non CPP)

differences between CPP and Non CPP

CPP —> e⁻ are recycled, produces only ATP, Only involves PSI

Non CPP —> / involves PSI and PSII, Produces NAPH , ATP and O₂, involves Photolysis

what does the Light- Dependent reaction need?

Light

function of light in LDR

absorbed by the photosynthetic pigment and excites the e⁻

what is the Cyclic photo phosphorylation stage

Light energy excites the chloroplast and causes releases it e⁻

e⁻ flows through electron transport system ( returns to chloroplast) → releases energy

energy causes protons in the stroma to actively move into the compartment ( proton pumps)

creates a proton conc gradient, protons move back into the stroma through protein channels ( facilitated diffusion)

protons flows into ATP synthase causing it to catalyse ADP + Pi ⇌ ATP

what is photolysis

using light energy to split water into Protons , electrons and ½ O₂

In the light dependent reaction what is the light energy absorbed by the photosystems used for

Making ATP from ADP + Pi ( photophosphorylation)

making NADPH from NADP

Photolysis

Cyclic Photophosphorylation ( image)

what are electron carriers

proteins that carry electrons

what are electron transport chains

Photosystems and electron carriers form electron transport chains and excited electrons flow through them

what happens during Non cyclic photophosphorylation

Light energy is absorbed by PSII, light energy excites e⁻ in chlorophyll

e⁻ move along the electron transport chain to PSI

in order to replace the e⁻ lost → Photolysis occurs

( CPP happens)

PSI absorbs light energy exciting electrons again

e⁻ react with protons forming hydrogen

NADP gets reduced forming NADPH —> to the LIR

why do electrons move after being excited

Move to a higher energy level

equation for photolysis

H₂O → 2 H⁺ + ½ O₂ + 2 e⁻

what happens to the Oxygen produced in photolysis

diffuses out of the chloroplast and plant through stomata

function of NADP

Hydrogen carrier

Non cyclic photophosphorylation (image)