BIOLOGICAL MOLECULES Flashcards
carbohydrate
Carbon, hydrogen, oxygen
Fat/ oil (oils are liquid at room temperature but fats are solid)
Carbon, hydrogen, oxygen (but lower oxygen content than carbohydrates)
protein
Carbon, hydrogen, oxygen, nitrogen, sometimes sulfur or phosphorus
Large carbohydrate molecules such as
starch, glycogen and cellulose are made up of long chains of smaller units – monosaccharides such as glucose – held together by chemical bonds
Fats are made up of
three units of fatty acids chemically bonded to one glycerol unit (Figure 4.2).
Proteins are made of
long chains of amino acids chemically bonded together (Figure 4.3). As there are about 20 different amino acids, their pattern in the chain can be quite complex, and the molecules can be very large.
Food tests do not all involve
heating – the only food test that needs heating is the Benedict’s test.
Water is
important to living things as a solvent – many substances (solutes) dissolve in it. Examples include glucose, salts and amino acids.
The different
combinations and sequences of amino acids in a protein molecule can result in creating different three-dimensional shapes. Some proteins are dependent on their shape to perform a specific function. For example, the groove along an enzyme molecule is its active site (where it combines with a substrate molecule; see Chapter 5). If the shape of the enzyme molecule is changed, the substrate will no longer fit in the active site. Antibodies have a binding site with which they can attach themselves to an antigen with a particular shape
Structure of DNA
A DNA molecule is made up of two strands. Each strand is a chain of units called nucleotides. It can be thousands of nucleotides long. Each nucleotide has one of four organic bases: A, T, C or G. Each base in one strand is cross-linked to a base in the other strand by a bond. A always bonds with T; C always bonds with G. The double strand is twisted to form a double helix (a double spring).
Importance of water as a solvent
• Most cells contain about 75% water. • Many substances move around a cell when they are dissolved in water. • Many important reactions take place in water. • Food can be digested only when it is in liquid form – enzymes need to be in water to carry out their reaction. • Excretory products such as urea are dissolved in water to dilute them and to allow their removal from the body. • Transport systems, e.g. the bloodstream, are water based. Plasma is mainly water with substances dissolved in it (see Chapter 9).
carbohydrate image
fat image
protein image
starch
reducing sugar
protein
fats test
VITAMIN C
