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36 Cards in this Set

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  • Back

Why does a higher light intensity increase the rate of photosynthesis?

More light is available to excite more electrons.

More electrons can take part in photophosphorylation so mare ATP and more reduced NADP is made.

What are autotrophs?

Organisms that use light energy or chemical energy and inorganic molecules to synthesis complex organic molecules.

What are heterotrophs?

Organisms that ingest and digest complex organic molecules releasing the chemical potential energy stored in them.

Whet are chemoautotrphs?

Prokaryotes that synthesis complex organic molecules using energy derived from exergonic chemical reactions.

What are photoautotrophs?

Organisms that use sunlight as their energy source and their raw materials are inorganic molecules.

Where does photosynthesis take place?

In the chloroplasts.

What is the size of a chloroplast?

Between 2 and 10 micrometers long.

What is the structure of chloroplasts?

They have double membranes.

The intermembrane space is about 10-20 micrometers wide.

The outer membrane is permeable to many small ions.

The inner membrane is less permeable.

What are the two distinct regions inside each chloroplast?



What are grana?

Stacks of flattened membrane compartments called thylakoids.

How are the chloroplasts adapted for their role?

Inner membrane controls the entry and exit of substances.

There are many grana which provides a large surface area for photosynthetic pigments.

The arrangement of photosystems allows maximum absorption.

Chloroplasts make some proteins they need for photosynthesis.

What are chlorophylls?

Mixtures of pigments that absorb light at different wave lengths.

What wavelengths do chlorophyll a and b absorb?

a - blue light at wavelength 450nm.

b - light at wavelengths 500nm and 640nm.

What are carotenoids?

Accessory pigments that absorb light that chlorophyll doesn't absorb very well and passes on the energy to the chlorophylls.

What are photosynthetic pigments?

Molecules that absorb light energy. Each pigment absorbs a range of wavelengths, other wave lengths are reflected.

What is photophosporylation?

The making of ATP from ADP and Pi in the presence of light.

What are electron carriers?

Molecules that transfer electrons.

What are electron acceptors?

Chemicals that accept electrons from another compound.

What is photolysis?

The splitting of water into H+ ions, electrons and oxygen.

What is cyclic photophosphorylation?

Where only photosystem one is used and excited electrons pass to the electron acceptor and back. Small amounts of ATP are produced.

What is the light-independent stage of photosynthesis?

Where carbon dioxide is fixed and used to build complex organic molecules.

What are the stages of the calvin cycle?

Carbon dioxide diffuses into the leaf then into the chloroplast. It is then in the stroma where it binds with RuBP, this reaction is catalysed by rubisco. Carbon dioxide is fixed and GP is made. The GP is reduced and phosphorylated to TP. Most TP molecules are recycled back into RuBP. The other molecules are used to form different substances.

What products are made in the calvin cycle?

GP is used to make amino acids and fatty acids.

TP molecules combine to form hexose sugars.

Glucose and fructose molecules combine to form sucrose.

TP is converted into glycerol.

Glycerol and fatty acids combine to form GP.

What is a limiting factor?

the factor that is present at the lowest or the least favourable value.

What three main effects does light have on a plant?

Causes the stomata to open.

Excites electrons.

Splits water molecules to produce protons.

How does temperature affect the rate of photosynthesis?

The rate increases up to 25 degrees Celsius. Any temperature above that the rate will fall as enzymes work less efficiently and will eventually denature.

What apparatus is used to measure the rate of photosynthesis?

A photosynthometer - air bubbles are collected in a capillary tube and the volume is recorded.

What is non-cyclic photophosphorylation?

It involves both photosystems. A pair of electrons get excited from photosystem two. The electrons pass along a chaing of electron carriers. Energy is released causing ATP to form. A pair of electrons are excited from photosystem one, they are replaced by the electrons from PS2, and they pass along electron carriers to NADP reductase losing energy to form ATP and reduced NADP is made. The electons in PS2 are replaced by broken down water.

What is photophosphorylation, how does it occur?

Light travels in photons and when a photon hits a chlorophyll molecule two electrons are excited Energy is released as the electrons pass along the chain of electron carriers. It porduces a force that joind ADP and Pi to make ATP.

What is water a source of?

Hydrogen ions.


What is the formula for working out light intensity?


What happens when there is no light available?

The light dependent stage cannot occur without light energy. Therefore, the light independent stage cannot occur without the products of the light dependent stage.

How does increased concentrations of carbon dioxide affect photosynthesis?

More carbon dioxide fixation leads to more molecules of GP and TP.

More gaseous exchange leads to more transcription which can lead to a stress response and stomata may close.

What are some limiting factors?

Light availability.

Carbon dioxide availability.


What are cotyledons?

Where seeds of dicotyledonous plants store food.

What is photosynthesis?

The process where light energy from the sun is transformed into chemical energy and used to synthesise organic molecules from inorganic substances.