Photosynthesis. 1) Heterotrophs: 2) Autotrophs: 3) Phytoplankton:

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1 CAPE BIO UNIT 2 Lesson 1-10 th Sept Define the following: Photosynthesis 1) Heterotrophs: 2) Autotrophs: 3) Phytoplankton: Photosynthesis is simply the process by which organisms convert solar energy to chemical energy: 12H CO 2 C 6 H 12 O 6 + 6O 2 + 6H 2 O or, in a more balanced form: 6H CO 2 C 6 H 12 O 6 + 6O 2 This is an energy requiring reaction - the energy source is sunlight Plants produce sugars as a source of food. However, they produce way more than they need to survive. This is good because all other life on earth must survive on the food energy obtained by this excess. Leaf structure and Function: Annotate structure to give functions of the parts

2 2012 AApplewhaite 2 Description of ways the leaf is adapted in order to accomplish Photosynthesis 1) Cuticle: - Is non-cellular, water proof and transparent. It allows light to pass through. 2) Chlorophyll arranged on flat membranes to expose as much chlorophyll as possible to sunlight. 3) No chloroplasts in epidermis to allow sunlight to penetrate to Mesophyll layer. 4) Upper epidermis: - Is a single layer of cells on the upper surface of a leaf. It allows light to pass to the cells below. Find some others. See Pages 3 and 4 of resource material

3 CAPE BIO UNIT 2 Lesson 1-10 th Sept Chloroplasts All photosynthesis occurs in the chloroplast, so let's review the anatomy of a chloroplast The innermost membrane of the chloroplast is called the thylakoid membrane. The thylakoid membrane is folded upon itself forming many disks called grana (singular = granum). The "cytoplasm" of the chloroplast is called the stroma Label the below chloroplast to show their internal structures: (see page 5 of resource material)

4 2012 AApplewhaite 4 The photosynthesis reactions can be broken down into two components: The light-dependent reactions (the "light" reactions) - occur on the thylakoid membranes The light-independent reactions (the "dark" reactions) - occur in the stroma Quick Check: 1) Give the precise location in a typical plant of: a) The light dependent stage: b) The light independent stage: 2) List the features of a chloroplast that aid photosynthesis Photosynthetic Pigments: Chloroplasts contain two different kinds of chlorophyll, called chlorophyll a and b, together with a number of other light-absorbing accessory pigments, such as the carotenoids and xanthophylls. These different pigments absorb light at different wavelengths, so having several different pigments allows more of the visible spectrum to be used. The absorption spectra of pure samples of some of these pigments are shown in the graph on the left. A low absorption means that those wavelengths are not absorbed and used, but instead are reflected or transmitted. Different species of plant have different combinations of

5 CAPE BIO UNIT 2 Lesson 1-10 th Sept photosynthetic pigments, giving rise to different coloured leaves. In addition, plants adapted to shady conditions tend to have a higher concentration of chlorophyll and so have dark green leaves, while those adapted to bright conditions need less chlorophyll and have pale green leaves. Quick Check: 1) Which colours of the spectrum does chlorophyll a absorb the most? 2) Turn to page 6 of the resource sheet and a. explain why chlorophyll looks green b. What are the colours of carentoids?

6 2012 AApplewhaite 6 Essay Question: a. By means of an annotated diagram only, describe the structure and function in photosynthesis of: a. The external structure of the dicotyledonous leaf 3 marks b. A palisade cell 3 marks c. A chloroplast 5 marks b. Explain what is meant by the term photosynthetic pigment and explain the difference between a primary pigment and an accessory pigment 4 marks

7 CAPE BIO UNIT 2 Lesson 1-10 th Sept References used: Biology Unit 2 for CAPE Examinations by Myda Ramesar, Mary Jones, Geoff Jones