CSEC BIOLOGY February 29, 2016 MRS. HAUGHTON 10DM PHOTOSYNTHESIS CSEC BIOLOGY February 29, 2016 MRS. HAUGHTON 10DM

TWO TYPES OF NUTRITION The two main types of nutrition are: Autotrophic nutrition (self-feeding e.g. plants and some bacteria) Heterotrophic nutrition (other-feeding e.g. animals, some plants and parasitic organisms)

PLANT CELLS VS. ANIMAL CELLS Plant cells contain chloroplasts and animal cells do not. Chloroplasts are the site of a process called PHOTOSYNTHESIS.

Photosynthesis occurs wherever the green pigment of chlorophyll is found (mainly in leaves). Chlorophyll is found in the chloroplasts. Chloroplasts are found in the cells of leaves and stems of plants, but are concentrated mainly in the leaves.

DEFINITION OF PHOTOSYNTHESIS Photosynthesis is the process where green plants combine water and carbon dioxide using sunlight energy to produce glucose and the by-product oxygen.

The reactants water and carbon dioxide are inorganic substances (from non-living sources). The product glucose is an organic substance (made by a living organism).

The carbon dioxide and water are called the raw materials of photosynthesis. The GLUCOSE is the main product and the oxygen is a by-product of the process.

EQUATIONS The word equation for photosynthesis is: The chemical equation is:

TWO STAGES Photosynthesis actually occurs in TWO stages. These are The Light Stage The Dark Stage Both stages occur at different places in the chloroplast.

LIGHT STAGE Water molecules enter the roots of plants by osmosis and travel up to the chloroplasts in the leaves.

In the light stage, sunlight energy enters the leaf and splits the water molecules into hydrogen and oxygen. This process is called photolysis. Therefore, the light stage must occur in the presence of sunlight.

Recall from the equation, Therefore,

The Oxygen will diffuse into the atmosphere to facilitate respiration. The Hydrogen will be used in the dark stage.

DARK STAGE The DARK stage can occur in either light or darkness. In the DARK stage, the Hydrogen from the LIGHT stage, will combine with the carbon dioxide gas to make glucose.

Recall from the equation, Therefore,

Conditions Necessary for Photosynthesis 1. Carbon dioxide (diffuses into leaf through stomata) 2. Water (absorbed from soil by roots) 3. Sunlight energy (absorbed by chlorophyll) 4. Chlorophyll (green pigment in chloroplasts) 5. Enzymes (present in chloroplasts) 6. Mineral elements (absorbed from soil by roots) 7. Correct temperature (0°C to 40°C for enzymes)

What Happens to the Products of Photosynthesis? The oxygen produced by photosynthesis will diffuse into the atmosphere for animals to breathe. But the Glucose, which is the main product, is a very important starting material for all the other nutrients a plant needs..

The excess glucose that is made during photosynthesis is stored as the starch grains in the chloroplasts

The Leaf The leaf is the main site of photosynthesis and so is where most food is made for the plant. The leaf therefore has many adaptations that make it suitable for making food for the plant.

External Structure of the Leaf These are the outer features that we can see. Broad, flat laminae Thin laminae Petiole or leaf stalk hold the leaf lamina 90° to the sunlight Laminae are spaced out around stems so they do not overlap and block sunlight

Internal Structures of Leaf Below is a diagram showing how the inside of a leaf looks. Notice that even though a leaf blade is very thin, it consists of many layers that each have a specific function. Also take note that quite a few of the specialized plant cells are located there.

1. Carbon dioxide enters and oxygen leaves through stomata 2. Air spaces for gases to diffuse 3. Palisade cells contain the most chloroplasts 4. Palisade cells are elongated and arranged end to end

5. Chloroplasts can move to get into a position to trap as much sunlight as possible 6. Root hair cells absorb as much water as possible from the soil. 7. Xylem vessels carry water and minerals from roots to leaves

8. Phloem sieve tubes transport glucose from leaves all around plant 9. Waxy cuticle prevents water loss needed for photosynthesis

Internal Leaf Structure

FROM A LEAF ON A PLANT

TO A SECTION THROUGH THE LEAF

TO A DETAIL OF THE CELLS IN THE LEAF SECTION

TO A DETAIL OF ONE CELL

Let’s now label the internal structure. Paste the diagram given to you in your books. Label the internal parts of the leaf with a pencil. Give your book to the teacher for marking.

FATE OF THE PRODUCTS OF PHOTOSYNTHESIS The oxygen produced by photosynthesis will diffuse into the atmosphere for animals to breathe. But the Glucose, which is the main product is a very important starting material for all the other nutrients a plant needs.

DIAGRAM SHOWING USES OF GLUCOSE MADE BY PLANTS

NOTE Note that the excess glucose that is made during photosynthesis is stored as the starch grains in the chloroplasts.

LINK TO ANMALS But what does photosynthesis have to do with animals? It is the way humans get oxygen for breathing. It is the way that sunlight energy is used by plants to make different nutrients that can enhance humans’ diets. Also, these plant nutrients are eaten by the animals that humans eat to stay alive.

worksheet

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Food Tests

REVISION QUESTIONS 1). In what type of organism does photosynthesis occur? 2). Where in the cell does photosynthesis occur? 3). What are the raw materials of photosynthesis? 4). What are the products of photosynthesis? 5). Where does the energy used to drive photosynthesis come from?

6). How many stages are there in the process photosynthesis? 7). What are these stages called? 8). Describe what happens in one of the NAMED stages of photosynthesis. 9). Describe what happens in the other NAMED stage of photosynthesis.

10). What is the MAIN product of photosynthesis used for in the plant? 11). What is chlorophyll? 12). Do you think that white leaves can photosynthesize? Why? Why not?

FOOD TEST QUESTION 1). Tests were performed on an unknown food. It turned black in iodine solution Left a grease spot on filter paper. Did not convert blue Benedict’s solution to red, but did so after addition of acid. Formed a pale purple coloration with copper sulphate and potassium hydroxide. The food tested was most likely which of the following: cake, bread, chips or butter? Why?

HOMEWORK 1. State five internal features of a leaf and 2. Five external features of a leaf that makes the leaf well adapted for the process of photosynthesis. Make sure you are able to explain why these features are important for the process.