Biological Molecules 2.2 Flashcards
How does hydrogen bonding occur between water?
The slight negative charge on the oxygen atom is attracted to the slight positive charge on the hydrogen atom of another water molecule. This attraction forms a hydrogen bond.
How does hydrogen bonding affect waters properties?
The numerous hydrogen bonds between molecules make water a very stable structure. Individual hydrogen bonds are weak and can be broken easily meaning the structure of water is not permanent and very fluid.
How does water’s thermal properties help living things survive?
The hydrogen bonds between water means that it can not easily escape and become a gas.
It has a high specific heat capacity and a high latent heat of vaporization, meaning it is a liquid over a large range of temperatures and does not heat up or cool down easily.
This is important for enzyme controlled reactions and acting as a coolant for mammals. Water being a liquid means it is an effective transport medium in tissues and blood as well as providing homes for aquatic animals.
How does waters cohesion and surface tension help living things to survive
Hydrogen bonds allow for strong cohesion between water molecules. This means that water can travel in columns through xylem vessels in plants.
How does waters density help living things survive?
Waters density is ideal for living things. If water was less dense, aquatic organisms would find it very difficult to float. Ice is also less dense than water which means ice can float and insulate the water underneath.
Why is it important that water is a good solvent?
As water is a polar molecule, it is a good solvent for ionic and covalent solutes. Molecules and ions can move around and react together in water, for example in the cytoplasm. Molecules and ions can also be transported around living things whilst dissolved in water.
Why is water described as dipolar?
A dipolar molecule is a molecule that possesses an electric dipole. Oxygen has a greater number of positive protons (a greater affinity for electrons) and ‘pulls’ the electrons closer creating a slighly negative region and a slightly positive region. The seperation of charge is an electric dipole moment.
What is a monomer?
A small molecule which binds to many other identical molecules to form a polymer.
What is a condensation reaction?
A reaction that occurs when two molecules are joined together with the removal of a water molecule.
What is a hydrolysis reaction?
A reaction that occurs when a molecule is split into two smaller molecules with the addition of water.
What chemical elements make up the 4 key biological molecules?
C, H, O for carbohydrates
C, H, O for lipids
C, H, O, N, S for proteins
C, H, O, N, P for nucleic acids
What is the difference between alpha and beta glucose?
On a ring of alpha glucose, the hydroxyl group (-OH) is below the ring on carbon 1, on beta glucose, the hydroxyl group is above the ring on carbon 1.
What is the difference between a hexose and a pentose monosaccharide?
Pentose is a five carbon monosaccharide whereas hexose has six carbons.
What is a glycosidic bond and how are they formed?
A glycosidic bond is a type of covalent bond formed from a condensation reaction which joins monosaccharides together. In carbohydrates, the glycosidic bond is between the atoms attached to carbon 1 and on carbon 4 for the consecutive monosaccharide.
What are examples of monosaccharides?
Glucose, fructose, ribose, deoxyribose
What are examples of disaccharides?
Maltose, sucrose, lactose
What are examples of polysaccharides?
Startch, glycogen, cellulose
What is maltose?
Two alpha glucose bonded together
What is sucrose?
An alpha glucose bonded to a fructose molecule
What is lactose?
An alpha glucose bonded to a beta galactose
What is present in startch?
Amylose, 10-30% and Amylopectin, 70- 90%
Describe the structure of amylose
Unbranched, helix shaped chain with 1,4 glycosidic bonds between alpha glucose
The helix shape, reliant on hydrogen bonds, makes it compact and therefore more resistant to digestion
Describe the structure of amylopectin
1,4 glycosidic bonds between alpha glucose molecules and 1,6 glycosidic bonds between molecules forming branches.
It also coils into a spiral shape with hydrogen bonds holding it in place
What is glycogen and what is its structure?
Glycogen is a polysaccharide found in animals and is made up of alpha glucose molecules. There are 1,4 and 1,6 glycosidic bonds meaning it is a branched molecule, it has more branches than amylopectin
What is cellulose and describe its structure?
Cellulose is a polysaccharide found in plants. It consits of long chains of beta glucose. Consecutive molecules are rotated 180 degrees of eachother. Hydrogen bonds give it high tensile strength.
What is cellulose and describe its structure?
Cellulose is a polysaccharide found in plants. It consits of long chains of beta glucose. Consecutive molecules are rotated 180 degrees of eachother. Hydrogen bonds give it high tensile strength.
What are triglycerides and how are they formed?
Triglycerides are non polar and hydrophobic molecules, they are made from one glycerol and three fatty acids, the two are joined together with ester bonds.
What are the functions of triglycerides?
Energy storage and source
Electrical insulation
Protection
Buoyancy
What is the difference between a saturated and unsaturated fatty acid?
Saturated means there are no double bonds between carbons. Unsaturated means there are double bonds, one (mono-) or more (poly-).
What is the difference between a saturated and unsaturated fatty acid?
Saturated means there are no double bonds between carbons. Unsaturated means there are double bonds, one (mono-) or more (poly-).
What is the effect of double bonds on the acid?
More fluid as the ‘kinks’ push the molecules further apart. Unsaturated acids also have a lower boiling point.
What are phospholipds?
They are a type of lipid, they are formed of one glycerol and two fatty acids, the third is replaced with a phosphate ion.
What are the properties of phospholipids?
They are amphipathic, the phosphate head is polar and soluble (hydrophilic) whereas the fatty acid tails are non- polar and insoluble (hydrophobic)
