Week 2 Digestion and Excretion Review
Task 1 Review the Tests for Macro nutrients
Three macro-nutrients that are synthesised by plants are starch, proteins and lipids. These all contain the elements carbon, hydrogen and oxygen bonded together. Proteins also contain the element nitrogen.
These three macro-nutrients are are built of simpler sub-unit molecules. Heterotrophs eat food containing these large nutrient molecules and must break them down into the simpler sub-units so that they are small enough to be absorbed from the intestines into the circulatory system. |
Task 2 Complex molecules are digested to smaller sub-unit molecules during digestion
Large nutrient moleculesStarch molecules are built of thousands of glucose molecules joined together.
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Digested small nutrient moleculesGlucose molecules are the sub-units of starch molecules
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Complex lipid molecule or triglyceride molecule.
Proteins are complex folded chains of sub-units called amino acids.
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Sub-units of a lipid molecule are glycerol and three fatty acid molecules.
Twenty amino acids are the "alphabet" for protein "words".
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New Holland Honeyeater nestlings Phylidonyris novaehollandiae
27 October 2013 |
All animals have to eat food in order to supply nutrients and energy to their body cells. These baby New Holland Honeyeaters (left) are well-adapted to being fed. They are always hungry.
Animals need a digestive system to transform large food molecules into small nutrient molecules that can be absorbed into their blood stream. |
Task 3 Excretion of nitrogenous wastes
Amino acids are transported to the cells. Inside the cells are organelles called ribosomes. Ribosomes are the organelles that help construct amino acids into new protein molecules. As in any chemical process reactants are converted to products and some of the products may be wastes. In the process of protein synthesis nitrogenous wastes are produced.
In fish this nitrogenous waste is mainly toxic ammonia. In birds and reptiles this nitrogenous waste is the relatively non-toxic uric acid. In mammals this nitrogenous waste is the moderately toxic urea. |
Adaptive advantage of the excretion of the different types of nitrogenous wastes
Task 4 Dissection of the kidney
Pearson Science 8 page 124
Refer to Pearson Science 8 page 119 to 121 to label the diagrams and make notes on the worksheet below