Understanding Carbohydrates, Fats, Proteins, and Enzymes

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What are we made of?

Carbohydrates, Fats, Proteins, Water.


All chemical reactions that take place inside the body.


Include sugars and starches. Contain three types of atoms: carbon, hydrogen, oxygen.

Sugars: The simplest kind of carbohydrates are the simple sugars or monosaccharides, such as glucose and fructose. If two monosaccharides join, a disaccharide is formed.

If many simple sugars join together, a molecule called a polysaccharide is made. (Starch and glycogen are polysaccharides.)

Carbohydrates Functions:
Energy: Energy is released by respiration. The carbohydrate used in respiration is usually glucose.
Transport: Animals transport glucose around the body, plants transport sucrose.
Storage: Plants store carbohydrates as starch in seeds and tubers. Animals store carbohydrates as glycogen. Cellulose in plants helps maintain the shape of the plant.


Contain three types of atoms: carbon, hydrogen, and oxygen. A fat molecule is made of smaller molecules joined together (glycerol and fatty acids). Fats are insoluble in water.

Energy: Fats and oils can be used in a cell to release energy. They give twice as much energy as that released by a carbohydrate.
Storage: Fats are very useful for storing energy.
Thermal Isolation and Communication: Some fats are hormones, which are chemical messengers that aid communication between your cells.

Protein molecules:

Contain five types of atoms: carbon, hydrogen, oxygen, nitrogen, and small amounts of sulfur.

Amino acids: Like polysaccharides, protein molecules are made of long chains of smaller molecules joined together → amino acids. There are 20 different amino acids. Any of these can be joined together in any order and number to make a protein molecule.

Proteins are sometimes classified according to their solubility:
- Some proteins are soluble in water, e.g. haemoglobin.
- Others are insoluble, e.g., keratin.

Proteins Functions:
The body needs proteins for:
- Making new cells: new cells are needed for growing and to repair damaged parts of the body.
- Metabolic reactions: all enzymes are proteins.
- Communication: Some proteins are hormones, which are chemical messengers that aid communication between your cells, tissues, and organs.
- Energy: However, proteins are not frequently used for energy.


Many chemical reactions can be sped up by catalysts. A catalyst is a substance that increases the rate of a chemical reaction and is not changed by the reaction.

Biological catalysts:
Enzymes are proteins that function as biological catalysts. Within any living organism, chemical reactions take place all the time → metabolic reactions. Most metabolic reactions are controlled by enzymes.

Properties of enzymes:

  1. All enzymes are proteins
  2. Enzymes are made inactive by high temperature.
  3. Enzymes work best at a particular temperature.
  4. Enzymes work best at a particular pH.
  5. Enzymes are catalysts.
  6. Enzymes are specific.

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