Cells Biology

Reactants for Photosynthesis

Reactants for Photosynthesis

Water and Carbon Dioxide

Where does Water and Carbon Dioxide enter the plant

Water enters through the roots of the plant and Carbon Dioxide enters through the Stomata (on the underside of the leaves)

How does Carbon Dioxide enter the plant

Diffusion through the Stomata

Diffusion

Movement of molecules from high to low concentration

Does diffusion require energy?

No

How does Water enter the plant?

Via Osmosis through the roots

Osmosis

The diffusion or movement of water through a semi-permeable membrane from high to low concentration

Plant roots drawing water from soil is an example of

Osmosis

Semi-permeable membrane

A membrane which only allows some molecules to pass through, usually only smaller ones

Function of Outer Membranes

They are clear to let light into the grana/thylakoids so that light reaction can happen

Clear Membranes allow

light to pass into the chloroplast

Thylakoids are filled with

Chlorphyll

Chlorophyll function

Captures the light for the light reaction

Light Reaction

Breaks water into H⁺ and O₂ and the Oxygen is released as a byproduct of the reaction

The stacked grana provide a

Large surface area which maximises light capture for the light reaction

What does maximising the light capture for the light reaction do

Maximise the amount of hydrogen provided and increase oxygen release

The light dependent phase produces ATP which..

is used to drive the light independent phase

One of the functions of the chloroplast is to aid the diffusion of

Carbon Dioxide, which is needed to make glucose

Semi Permeable Membrane allows

for carbon dioxide to diffuse easily into the liquid storma

The liquid of the Stroma allows for

Easier diffusion of carbon Dioxide

The liquid of the Stroma allowing for easier diffusion of carbon dioxide allows for

Increased rate of the light-independent reaction and glucose production

Semipermeable membrane and liquid storma both

aid diffusion for the transport and fixation of carbon dioxide in the light independent reaction which will produce more glucose

Word equation for Photosynthesis

Carbon Dioxide + Water → Glucose + Oxygen ( In the presence of light and chlorophyll)

What does the light-independent reaction do?

Captures the Carbon Dioxide and joins the H⁺ with the CO₂ to produce glucose

In Photosynthesis, an increase in CO₂/ Water concentration will

Allow Photosynthesis to increase

Why does an increase in CO₂/ water concentration allow photosynthesis to increase?

Because an increase in substrate/ reactants concentration will increase the rate of enzyme reactions

Why does an increase in substrate/ reactants concentration increase the rate of enzyme reactions in photosynthesis?

Because the water/ CO₂/ Substrate will join with the enzyme to form the enzyme-substrate complex more often

Increased substrate concentration will aid/speed up photosynthesis due to

the increased formation of the enzyme-substrate complex

Decreased substrate concentration will slow/stop photosynthesis due to

reduced formation of the enzyme-substrate complex

Photosynthesis can only occur if

all substrates are at a sufficient concentration

Increased Carbon Dioxide will increase the speed of light independent reactions as

More carbon can be obtained to make glucose

Carbon Dioxide forms a substrate + enzyme complex with

the enzymes of the light-independent reaction

Increased water will increase the speed of the light-independent reactions as

the higher concentration will allow water to form an enzyme-substrate complex with the enzymes of the light-dependent reaction at a faster rate

What does an increase in the rate of forming an enzyme-substrate complex with the enzymes of the light-dependent phase do?

The water molecules split at a faster rate, releasing oxygen and making the Hydrogen ions for the light-independent phase

CO2 decrease slows the

Light-independent reaction

H2O decrease slows the

Light-dependent reaction

Decreased CO2/ Water concentration

Slows down the photosynthesis reaction

Increasing substrate concentration

Will speed photosynthesis until some other factor, such as enzyme saturation, becomes the limiting factor

High Temperatures

Will speed up photosynthesis at first

Why will high temperatures at first speed up the rate of photosynthesis?

Because collisions between water/CO2 and the photosynthesis enzymes will happen at a faster rate, allowing for more successful collisions

What will happen if the temperature gets very high?

The enzyme will denature and stop the reaction

Why will a too high temperature cause the enzyme to denature and stop the reaction?

The high temperature will break the H-bonds within the enzyme which will cause the active site to change shape and the substrate/H2O/CO2 will no longer fit the active site, therefore stopping photosynthesis

Low temperatures will

slow the rate of enzyme reactions

Why will low temperatures slow the rate of enzyme reactions?

Because they will cause the enzymes to collide with the substrate/water/CO2 less often due to slower molecule movement

Does low temperature denature enzymes?

No, so once the temperature rises again, the enzymes and photosynthesis reactions can resume at a faster pace

Very low temperatures that would turn the water to ice would

stop photosynthesis because water must be in liquid form for photosynthesis

How does water enter a plant?

Osmosis

How does water in the soil enter the roots of a plant?

Tiny root hairs

Water is transported from the root of the plant to the

Chloroplast within a leaf cell

Purpose of the pigment Chlorophyll

To absorb thylakoid membrane light energy in Chloroplasts

How does water availability affect the rate of photosynthesis?

If there is not enough water, the plant will be deprived of hydrogen, so will be unable to construct the glucose molecule and thus lower photosynthesis rate

How does the concentration of Carbon Dioxide affect the rate of photosynthesis?

Carbon Dioxide is combined with Oxygen in the light independent phase to form glucose

The rate of Photosynthesis will always correspond to the

factor which is in least supply

When other factors necessary for photosynthesis become ‘limiting factors’

those other factors need to increase to bring about a further increase in the rate