Aqa Biol4 3.1 - Overview Of Photosynthesis

Front 1

How are leaves adapted for photosynthesis?

Back 1

Large SA that collects lots of sunlight

Minimum overlap of leaves on the plant

Thin (light absorbed in first few millimetres and short diffusion distance)

Transparent cuticle and epidermis that let light through to the photosynthetic mesophyll cells beneath

Long, narrow upper mesophyll cells packed with chloroplasts

Front 2

6CO₂ + 6H₂O --light-->

Back 2

C₆H₁₂O₆ + 6O₂

Front 3

What are the three main stages to photosynthesis?

Back 3

Capturing of light energy
LDR
LIR

Front 4

What happens in the LDR? What are the products?

Back 4

Light energy is converted into chemical energy. An electron flow is created by the effect of light on chlorophyll and this causes photolysis of water into protons, electrons and oxygen
Products are: NADP, ATP and oxygen

Front 5

What happens in the LIR? What are the products?

Back 5

Protons from LDR are used to reduce carbon dioxide to produce sugars and other organic molecules

Front 6

Where does the LDR take place?

Back 6

Membranes of the thylakoids

Front 7

Where does the LIR take place?

Back 7

In the fluid-filled matrix

Front 8

What is oxidation?

Back 8

Loss of electrons or hydrogen, gain of oxygen

Front 9

Photolysis of water:
2H₂O -->

Back 9

4H⁺ + 4e⁻ + O₂

Front 10

How are chloroplasts structurally adapted to their function of capturing sunlight?

Back 10

The thylakoid membranes provide a large SA (e.g. for attachment of chlorophyll

Network of prteins in grana hold chlorophyll in a very precise manner (max absorption of light)

Granal membranes have enzymes attached (help with ATP manufacture)

Chloroplasts contain DNA and ribosomes so they can quickly and easily manufacture proteins needed for LDR

Front 11

Where is the site of the LIR?

Back 11

The stroma of the chloroplasts

Front 12

How is the chloroplast adapted to carryingout the LIR?

Back 12

Fluid filled stroma contains all the enzymes needed to carry out the LIR

Stroma surrounds the grana and so the products of the LDR in the grana can readily diffuse to the stroma

Contains both DNA and ribosomes --> Can quickly manufacture some proteins needed for LIR

Front 13

What is a limiting factor?

Back 13

At any given moment, the rate of a physiological process is limited by the factor that is at its least favourable value

Nice :) - Remember PS is made up of a series of small reactions - the slowest reaction determines the overall rate of PS

Front 14

What are the two common ways of measuring the rate of PS in a plant?

Back 14

The volume of oxygen released by a plant

The volume of carbon dioxide taken up by the plant

Front 15

When light is the limiting factor, the rate of PS is ________ ____________ to _____ _________

Back 15

directly proportional, light intensity

Front 16

What is the compensation point?

Back 16

When there is no net exchange of gases by the plant

Front 17

Between 0 and 25*C the rate of photosynthesis is approximately doubled for each __*C rise in termperature

Back 17

10

Front 18

Purely photochemical reactions are not usually affected by temperature....

Back 18

This told researchers that there was also a totally chemical process involved as well as a photochemical one