LESSON 1: Biomacromolecules

Unit 1; Area of Study 2Functioning OrganismsChapter 5Obtaining Energy and Nutrients for LifeWEEK 6: Obtaining NutrientsLEARNING OUTCOMESBy the end of this week, you should be able to explain:Biochemical processes including photosynthesis and cellular respiration in terms of inputs and outputs.Obtaining nutrients: organic and inorganic requirements; autotrophs; heterotrophs.Obtaining energy: inputs and outputs of photosynthesis; structural features of photosynthetic organisms.Processing nutrients: features of effective systems in heterotrophs; examples of systems in different animals.

3LESSON 1: Heterotrophs, autotrophs and photosynthesisLEARNING OUTCOMESBy the end of this lesson, you should be able to:Define autotroph and heterotroph.Distinguish between heterotrophs and autotrophs in terms of nutrient requirements for life.Summarise the process of photosynthesis in a word equation and chemical equation.Identify structural features of photosynthetic organisms that facilitate their ability to photosynthesise.4Active and PassiveWhat do the terms mean?Watch the clip....Is the whale shark an active feeder or a passive feeder?HeterotrophsActively obtain the energy they need for life by feeding on organic matter found in their surroundings (food!)They then use this organic matter to build and repair their cells.

Give some examples...What structural, physiological and behavioural adaptations do heterotrophs have to help them obtain their food?

AutotrophsOrganisms that just take up (absorb) the energy they need from their surroundings.They build organic matter from simple inorganic matter taken up from the air, soil or water.

Give some examples.....So what about these guys...?

Carnivorous PlantsCarnivorous plants still need water and sunlight like other green plants to make food/energy (glucose) but they get their mineral nutrients from trapping and consuming animals.Carnivorous plants are adapted to grow in places where the soil is thin or lacking nutrients, especially nitrogen, such as acidicbogsand rock outcroppings.

PhotosynthesisPlants, algae and some protists can make sugars by photosynthesis.Sunlight energy is converted into chemical energy (in the form of glucose) in the chloroplasts found in the cytosol of cells.

What do you know already?

Plants use the energy from the sun to make molecules such as glucose, starch and proteins.These molecules can then be used for food for the plant, but also for animals like us.A waste product of the process is oxygen, which is released into the atmosphere.

16The ImportanceThe importance of photosynthesis is in the conversion of unusable sunlight energy into usable chemical energy (glucose).It is one of the most important biochemical processes, since nearly all life on Earth either directly or indirectly depends on it as a source of energy.17The EquationWord equation:

Balanced chemical symbol equation:

lightchlorophylllightchlorophyllcarbon dioxide+ waterglucose+ oxygen6CO2+ 6H2OC6H12O6+ 6O218Or: six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen.

19Plants absorb water through their roots, and carbon dioxide through their leaves. Some glucose is used for respiration, while some is converted into insoluble starch for storage. The stored starch can later be turned back into glucose and used in respiration.

20Testing a green leaf for starchWill a plant that has been kept in a dark cupboard for a few days contain starch in its leaves?Structure of the LeafPhotosynthesis takes place mainly in the cells of the leaves.Leaves are well adapted for photosynthesis its structure is well suited to its function.Leaves are made up of four main layers:Upper epidermisPalisade layerSpongy layerLower epidermisMesophyll layerInside the leaf

Structure of the LeafWaxy cuticleVein/vascular bundleAir spaceStomaGuard cellUpper epidermisLower epidermisPalisade cellSpongy mesophyll cellLabel the diagram with the structures:

Waxy cuticleUpper epidermisPalisade cellSpongy mesophyll cellAir spaceLower epidermisGuard cellStomaVascular bundle (vein) xylem and phloem

ABCDEFGHIEpidermisSingle layer of cells on the upper and lower surfaces of the leaf.Helps to keep the leafs shape.Has closely fitting cells:Reduces evaporation from the leafPrevents bacteria and fungi from getting inThin waxy layer covering epidermis called the cuticle helps to reduce water loss further.Have stomata.In woody stems, the epidermis is bark.

StomataSingular: stomaStructures in the leaf epidermis.Consists of a pair of guard cells, surrounding an opening called the stomatal pore.The stomata can open and close by changes in the turgor and shape of the guard cells.In some plants they are located on the lower epidermis only, others have stomata on both sides of the leaf.

StomaGuard cellLeaf epidermal cell

How Do Stomata Work?Generally, they open during daylight hours (whilst photosynthesis is taking place) and close during the night.Why? What do plants need to photosynthesise?During the day they are open to allow carbon dioxide to diffuse into the leaf (and oxygen out) so photosynthesis can take place.

MesophyllTissue between the upper and lower epidermis.Consists of two layers (see diagram).PALISADE CELLS:Function to make food by photosynthesis.Hence, they have lots ofSPONGY MESOPHYLL CELLSVary in shape, and fit loosely together.Many air spaces between them.

chloroplasts.

Air SpacesWhilst photosynthesis is taking place, the air spaces in the mesophyll layer fill with carbon dioxide as it enters the leaf, and oxygen as it leaves the leaf.Veins (vascular bundles)Xylem vessels carriy water needed for photosynthesis to the mesophyll cells.The mesophyll cells take in water through osmosis.Branching network no cell is far away from a water supply.Sugars made in mesophyll cells are passed to the phloem cells carry sugar away from the leaf to the stem.