Biological Molecules

Question 1

What are the properties of water

Answer 1

Cohesion, Adhesion, Useful in Metabolic reactions, Forms ions, Organises non-polar molecules, Solid water less dense than liquid, High heat vaporisation, High specific heat capacity, An excellent solvent, High surface tension,

Question 2

What is Cohesion

Answer 2

Water molecules stick to other water molecules (hydrogen bonding),

Question 3

What is Adhesion

Answer 3

Water molecules stick to other polar molecules (hydrogen bonding),

Question 4

How is water used in metabolic reactions

Answer 4

Is a metabolite in many metabolic reactions and an important solvent for metabolic reactions to occur,

Question 5

How does water form ions

Answer 5

Hydroxide and Hydrogen ions form from the water molecule and can be used in chemical reactions such as photosynthesis,

Question 6

Why is it useful that solid water is less dense than liquid water

Answer 6

The molecules in a solid are more spread out than in liquid, bodies of water freeze from the top down, providing insulation for organisms under the ice,

Question 7

Why is high heat vaporisation of water useful (high latent heat of vaporisation)

Answer 7

It takes a lot of heat energy to evaporate energy so organisms can cool down without loosing too much water,

Question 8

Why is water having a high surface tension useful

Answer 8

Due to cohesion the water molecules stick together and allow the surface of the water to act as a habitat,

Question 9

Why is the high specific heat capacity of water useful

Answer 9

A large amount of energy is required to change the temperature of the water due to lots of hydrogen bonds per area, so temperature in bodies of water does not change rapidly and so is a good habitat,

Question 10

Why is water an excellent solvent

Answer 10

Water dissolves polar molecules and charged ions, Bodies of water contain dissolved substances like oxygen and organisms can live in them and respire, it is also useful for transporting substances like in the xylem,

Question 11

Why is carbon important

Answer 11

All living things are made of carbon containing molecules,

It forms the framework for proteins, carbohydrates and fats,

Makes glucose and carbon dioxide,

Carbon cycle,

Also in non-living and abiotic matter like rocks and soil

Question 12

How many bonds does carbon usually have

Answer 12

4

Question 13

What is polymerisation

Answer 13

The formation of a polymer from monomers (the monomers are linked together in a chain,

Question 14

What is hydrolysis

Answer 14

Breaking down polymers into monomers by adding water

Question 15

What is a condensation reaction

Answer 15

Forming a covalent bond between monomers to form polymers by the removal of water,

Question 16

What are lipids made of

Answer 16

Carbon, hydrogen and oxygen (less than carbohydrates)

Question 17

Are lipids soluble

Answer 17

Insoluble in water but soluble in organic solvents like ethanol

Question 18

What are Triglycerides

Answer 18

Lipids that store energy and act as thermal insulation, they come in the form of fats and oils

Question 19

What lipid is essential for the formation of cell membranes

Answer 19

Phospholipids

Question 20

What is the structure of glycerol

Answer 20

C3H8O3

Question 21

Structure of Triglycerides

Answer 21

One molecule of glycerol with three fatty acids attached to it, they are joined together by condensation reactions and are bonded by and ester bond

Question 22

What is the structure of a phospholipid

Answer 22

One molecule of glycerol, two fatty acids and one phosphate group

Question 23

Why are phospholipids so good at forming membranes

Answer 23

The fatty acid tails are non-polar and hydrophobic and the phosphate group is polar and hydrophilic, so when they are in water they arrange themselves so their heads are down and their tails are up or form spheres called micelles, the heads are near the water while the tails stay well away

Question 24

What are unsaturated and saturated fatty acids

Answer 24

Unsaturated means it is possible to join extra hydrogen to them due to a double bond and Saturated means there are no spare bonds so no extra hydrogen can be added,

Question 25

Why are animal fats solid at room temperature

Answer 25

Because the kinks (double bonds) in unsaturated fatty acids make unsaturated triglycerides be liquids at room temperature, However animal fats tend to be saturated so are solid at room temperature,

Question 26

What are some uses of triglycerides

Answer 26

Energy stores in plants and animals, Energy is released when they are oxidised in respiration, due to their high proportion of carbon and hydrogen they contain more energy than a carbohydrate, Adipose tissue acts as an excellent heat insulator in animals, In plants they are often found in seeds where they serve as lightweight, high-energy stores.

Question 27

Are triglycerides soluble in water

Answer 27

No, their molecules are non-polar and hydrophobic, Most form a layer on top of water and if they are stirred they group together to form droplets.

Question 28

What is the emulsion test

Answer 28

Grind the substance with a pestle and mortar then shake with ethanol, any lipids in the substance will dissolve in the ethanol, let the substances settle apart then pour the ethanol into another test tube containing water. If there are any lipids dissolved in the ethanol it will form little droplets in the water and create a cloudy white effect in the water.

Question 29

What are proteins made of

Answer 29

Many amino acids in long chains, There are 20 different naturally occurring amino acids that can be assembled in any order,

Question 30

What is the structure of an amino acid

Answer 30

One amino group, -NH2, which reacts and neutralises acids by accepting hydrogen ions to become NH3+ One carboxyl group, -COOH which breaks apart to produce hydrogen ions when dissolved in water and the carboxyl group becomes -COO- Because of the charged amino acids are soluble in water. They also each have a different group known as the R group/side chain.

Question 31

What is the primary structure of protein

Answer 31

Amino acids are joined in a condensation reaction resulting in a peptide bond between them (the molecule is a dipeptide), Long chains (polypeptides) of amino acids are proteins, A protein will always have an amino terminal at one end an a carboxyl terminal at the other, Each type of polypeptide has its own unique sequence of amino acids,

Question 32

What is the secondary structure of protein

Answer 32

Polypeptides can form regular coils or pleats, The alpha helix is when the chain coils around in a spiral, held in place by hydrogen bonds between the hydrogen atom of an amine group and the oxygen atom of a carboxyl group from another amino acid, Can also form beta pleated sheets, where the polypeptide is folded rather than coiled, depends on the sequence of amino acids,

Question 33

What is the tertiary structure of protein

Answer 33

The polypeptides can form again forming complex 3d shapes, They are held in place by different bonds between the R groups of the amino acids; hydrogen bonds, ionic bonds and disulphide bridge bonds, The shape is determined by where the bonds can form and therefore by the sequence of amino acids,

Question 34

What is the quaternary structure of protein

Answer 34

Proteins made of several polypeptides joined together, They are held in place by hydrogen bonds, disulphide bridge bonds, ionic bonds and hydrophobic interactions,

Question 35

What are fibrous proteins

Answer 35

Often made of repeating amino acid sequences, Secondary structure, Insoluble in water Long, thin parallel chains that have important structural functions but metabolically inactive, e.g. collage and keratin (bone and hair)

Question 36

What are globular proteins

Answer 36

Very precise primary structure made of non-repeating sequence of amino acids, Chain is always the same length, Tertiary structure, Very specific shapes linked to their functions, Soluble in water, Metabolically active, E.g. Haemoglobin, enzymes, antibodies,

Question 37

What is the general formula of carbohydrates

Answer 37

CH2O

Question 38

What are the three basic types of carbohydrates

Answer 38

Monosaccharide, Disaccharide and Polysaccharide

Question 39

What are monosaccharides

Answer 39

Simple sugars, small molecules that dissolve in water and taste sweet, They are the monomers that larger carbohydrates are made from,

Question 40

What is the structure of glucose

Answer 40

A monosaccharide, Five carbon atoms form a ring, Alpha glucose and beta glucose exist based on the orientation of the hydrogen and hydroxyl group on carbon atom 1,

Question 41

What are two other monosaccharides

Answer 41

Fructose and Galactose, They all have the formula C6H12O6 but slightly different properties,

Question 42

What are disaccharides

Answer 42

Molecules made of two monosaccharides joined together, They taste sweet and are soluble in water, They can be broken down into their component monosaccharides using hydrolysis.

Question 43

What is a disaccharide example

Answer 43

Maltose (Two glucose), Sucrose (Glucose and fructose) and Lactose( glucose and galactose)

Question 44

How do disaccharides form

Answer 44

Condensation reactions form a glycosidic bond between the two sugar molecules and a water molecule is formed,

Question 45

What is a polysaccharide

Answer 45

Giant molecules made from many monosaccharides joined by condensation reactions, They are insoluble because their molecules are so large and cannot spread out in between water molecules, They are also not sweet,

Question 46

What is an example of a polysaccharide

Answer 46

Starch, Glycogen and cellulose,

Question 47

Animal storage carbohydrate Animal structural carbohydrate Plant storage carbohydrate Plant structural carbohydrate

Answer 47

Glycogen Chitin Starch Cellulose

Question 48

What is the starch test

Answer 48

Add Iodine and the starch will turn blue-black

Question 49

What is a reducing sugar

Answer 49

A sugar that is ready to loose electrons to another, making the sugar oxidised and the other substance reduced, Examples are glucose, fructose and maltose, To test for them you add Benedict's solution and heat at 80 degrees, the solution should go Brick Red if reducing sugar is present,

Question 50

What is a non-reducing sugar

Answer 50

A sugar that is not readily oxidised and so does not reduce other substances, Example; Sucrose, To test you must boil the substance with a dilute acid (usually hydrochloric) then neutralise it by adding hydrogen carbonate solution. Then you add the benedict's solution and heat at 80 degrees again, It will turn brick red if the reducing sugar is present,