IGCSE Science - Biology: Nutrition 

Nutrients and Nutrition

• Nutrition is one of the 7 characteristics of living organisms

  Nutrition is the %%taking in of nutrients (organic substances and mineral nutrients)%% that contain the %%raw materials or energy needed by the organism.%% It also includes %%absorption%% %%and assimilation%% of these nutrients into new %%body tissue during growth and tissue repair.%%

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Plant nutrition %%does not include taking in organic substances%% because plants make their own %%carbohydrates using photosynthesis.%% However, plants need to take in %%mineral ions through their roots%% to make other %%substances needed for healthy growth and tissue repair.%%

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Carbohydrates, Proteins, and Lipids

Most molecules found in living organisms fall into %%three main groups:%%

• carbohydrates
• proteins
• lipids

Which are commonly %%called fats and oils.%%

All these molecules contain %%carbon (C), Hydrogen (H), and Oxygen (O)%%. All %%proteins%% contain %%Nitrogen (N)%% and s%%ome also contain Sulfur (S).%%

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%%Carbohydrate%% molecules are made up of %%small basic units called simple sugars%%. These are formed %%from carbon, hydrogen, and oxygen atoms,%% sometimes arranged in a ring-shaped molecule. E.g. glucose.

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Simple sugar molecules %%can link together to form larger molecules%%. They can %%join in pairs%%, such as sucrose (the sugar we use in our food). They can also %%form much larger molecules called polysaccarides%%, such as starch and glycogen, which are both chains of glucose molecules.

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%%Protein%% molecules are made up of %%long chains of amino acids linked together%%. There are %%20 diff. kinds%% of amino acids in plant and animal cells. These can join in l%%ong chains, in any order, to make all the diff. proteins%% within the plant or animal body. E.g. the %%structural proteins in muscles%% as well as %%enzymes that help control cell reactions.%%

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A %%lipid%% is what is commonly know as %%a fat or oil%%. Fats are %%solid at room temp, whereas oils are liquid, both they both have similar structure.%% Both are made from %%basic units called fatty acids and glycerol.%% There are 3 %%fatty acids in each lipid%%, and the %%acids differ in different lipids%%. Lipid are important in %%forming cell membranes%% and many other %%molecules such as fats in storage cells.%%