Chapter 5: Obtaining energy and nutrients for life Heterotrophs and autotrophs Autotrophs and photosynthesis Heterotrophs and food The digestive system Digestion in animals

Today’s lesson Heterotrophs and autotrophs Autotrophs and photosynthesis

Autotrophs PlantsAlgae

Soak up sunlight to gain energy they need for living (photosynthesis) Build their organic matter from simple inorganic matter taken up from their surroundings Terrestrial autotrophs (air and soil) Aquatic autotrophs (water) Autotrophs

Heterotrophs All animals All fungi Some bacteria

Heterotrophs Obtain energy for living and material for building and repairing their structure from organic matter in their surroundings Organic matter used by heterotroph is its food

Autotrophs and photosynthesis

Plants algae and some protists (phytoplankton) can make organic molecules (sugar) by photosynthesis Energy is obtained from sunlight Organisms that can do this are autotrophic Photosynthesis occurs in the chloroplasts, found in the cytosol of some cells.

Ins and outs of photosynthesis Sunlight is converted to chemical energy in sugars 2 sets of reactions 1.First set of reactions depends on the availability of light and presence of chlorophyll 2.Second set of reactions does not depend on light but depends on products from the first set of reactions

First set of reactions Water + ADP Sunlight Chlorophyll oxygen + hydrogen ions + ATP ADP = Adenosine diphosphate ATP = Adenosin triphosphate

Second set of reactions Carbon dioxide + hydrogen ions + ATP ADP = Adenosine diphosphate ATP = Adenosin triphosphate Where does Carbon dioxide come from? Glucose + ADP

Combining the two ATP and ADP are used during the reactions (chemical energy) End result: Carbon dioxide + water Sunlight Chlorophyll Glucose + oxygen 6CO 2 + 6H 2 0C 6 H 12 O 6 + 6O 2 Sunlight

What makes it all happen? Sunlight provides the energy required to drive the first reaction The ATP produced from the first reaction is a high-energy compound that provides energy that drives the second set of reactions This leads to the production of glucose from the carbon dioxide and hydrogen ions

Plant structures in relation to photosynthesis Certain characteristics exist in plants which enable photosynthesis to occur Leaves, trunk and roots

Leaves Flat shape- provides large surface area exposed to sunlight Chloroplasts- enables it to trap energy from sunlight Stomata (pores) on leaf surface provide access into leaf for carbon dioxide Thinnes- diffusion of carbon dioxide to photosynthetic cells in the leaf tissue Vascular tissue and xylem vessels- transport water and other compounds

Stems Xylem vessels and fibres give rigidity to a stem and assist upright stance Branching of stems allows layers of leaves, increasing total surface area Xylem vessels transport water and minerals from roots to all aerial parts of plant Phloem transports products of photosynthesis

Roots Extensive root systems taps a significant volume of soil for water and mineral salts Root hairs- increases area available for absorption of water and mineral salts Oxygen from air in soil diffuses through root hairs into plants

All the characteristics of leaves, stems and roots ensure that these structures combine to provide the sunlight energy, carbon dioxide and water that a plant requires for photosynthesis In other words, it enables the plant to get what it needs for the reactions to take place efficiently

Summary Heterotrophs- all animals, fungi, bacteria Autotrophs- all plants, algae, some bacteria Autotrophs make their own organic material from inorganic substances (using sunlight) Heterotrophs rely on food, organic matter Photosynthesis- converting energy of sunlight to chemical energy in sugars Raw materials of photosynthesis are carbon dioxide and water, products are sugar and O 2 Structures of various parts of plants maximise plant’s ability to obtain raw materials necessary for photosynthesis