Biomolecules

Elements in food

  • Carbon

  • Hydrogen

  • Oxygen

  • Nitrogen

  • Phosphorous

  • Sulfur

Water is often considered the sixth group


Functions of food

  • Energy

  • Intake of nutrients

  • Insulates

  • Growth and repair


Autotrophic and Heterotrophic

  • Green plants can make their own food through photosynthesis - plants are therefore autotrophs

  • Animals eat other organisms to get proteins and energy - heterotrophs 


Food constituents 

  • Carbohydrates 

  • Vitamins 

  • Starch

  • Minerals

  • Fats

  • Food supplies animals with energy for all animal activities

  • To provide materials for respiration, digestion, immunity etc

  • To provide raw materials for milk, egg, and wool production etc


Trace elements are required in our body in very small amounts: iron (Fe), copper (Cu) and Zinc (Zn).

These elements, when combined in different ratios form larger units called biomolecules.


Carbohydrates

Simple sugars - 

  • Monosaccharides are made of one sugar unit eg - glucose / fructose

  • Disaccharides are made of two sugar units eg - sucrose

  • They give a fast release of energy

Complex carbohydrates - 

  • Long chains of sugar units are called polysaccharides eg - starch, cellulose, glycogen 

  • They give slow release of energy

Testing for carbohydrates 

Glucose:

  • Blue Benedict’s solution turns brick red when it is boiled with glucose 

Starch:

  • Orange-brown iodine turns blue-black when it reacts to starch

  • The Benedict’s test is semi-quantitative (in between answers) because by observing the colour change on a scale from blue to red it’s possible to estimate the concentration


Lipids

  • Lipids contain carbon, hydrogen and oxygen

  • Fats are solid at room temperature and oils are liquid at room temperature

  • They are made of glycerol and 3 fatty acids

  • Fats are an energy store, they also form part of our cell membranes and nervous system (fats insulate nervous system)

  • Fats are insoluble in water (hydrophobic) meaning they do not mix with water

Testing for lipids

  • Lipids go cloudy white when they are mixed with ethanol and then water.

  • Can also do the brown paper test - rub food on the paper, if it dries in it is not a fat, if it leaves a transparent grease stain it is a fat


Protein

  • Contain carbon, hydrogen, oxygen and nitrogen

  • Long chains of amino acids folded into a specific 3D shape

  • Structural (form tissues) or metabolic (enzymes, hormones, antibodies)

Testing for protein 

  • In the Biuret test the blue solution turns purple in the presence of protein