Biological molecules

Question 1

What is a monomer?

Answer 1

A small repeat unit that forms a polymer

Question 2

What is a polymer?

Answer 2

A long chain of repeat molecules

Question 3

What structures can polymers have?

Answer 3

Polymers can be long, single stranded, short and / or highly branched

Question 4

What is the backbone of most polymers made of?

Answer 4

Carbon

Question 5

What are the three main types of biological molecule?

Answer 5

Carbohydrates
Proteins
Lipids

Question 6

What are the two main types of sugar (from shape)

Answer 6

Hexose (6 carbon ring)
and
Pentose (5 carbon ring)

Question 7

How do you perform the emulsion test?

Answer 7

1. Add ethanol and shake
2. Add water and shake
3. If cloudly, lipids are present.

Question 8

What are the main uses of lipids?

Answer 8

Membrane formation
Hormone production
Electrical insulation 
Waterproofing
Thermal insulation
Protects vital organs
Buoyancy in aquatic animals
Energy storage

Question 9

What are triglycerides made up of?

Answer 9

A hydrophilic glycerol head, ESTER BONDED to three hydrophobic fatty acid tails.

Question 10

What are the types of bonds in:

1) Carbohydrates
2) Lipids
3) Amino acids + Proteins

Answer 10

1) Glycosidic bonds
2) Ester bonds
3) Peptide bonds

Question 11

What are the two types of polymer in starch?

Describe them.

Answer 11

Amylose and amylopectin
Amylose - Alpha glucose joined by 1-4 glycosidic bonds. The angle means that amylose forms a helix, stabilised by hydrogen bonding, making it much less soluble than the molecules used to make it.
Amylopectin - 1-4 glycosidic bonds, but with 1-6 branching points approx every 25 glucose units.

Question 12

Why is ice less dense than water?

Answer 12

Because when water freezes, the hydrogen bonds between the molecules fix their positions slightly further apart than the average distance

Question 13

Why is water critical for sustaining life?

Answer 13

1. It is a solvent in which many solutes from organisms can be dissolved. As such, water can act as a medium for important chemical reactions
2. Water is a very efficient transport medium. Cohesion means that when water moves through a body, the molecules stay together. Adhesion means that water sticks to and is pulled along surfaces.
3. Water acts as a coolant, and can buffer temperature changes during chemical reactions. Maintaining a constant temperature is important as enzymes only have a narrow working range.
4. Many organisms live in water, as it is stable - does not change temp or become gas easily, and as ice floats, it forms an insulating layer on top of the water. Animals can also live on this ice or on water’s surface.

Question 14

What is the order of the upwards molecules on alpha and beta glucose?

Answer 14

ALPHA: CH2OH, H, OH, H, H
carbon: 6,5 4 3 2 1

BETA: CH2OH, H, OH, H, OH
6, 5 4 3 2 1

Question 15

What are the three main hexose monosaccharides?

Answer 15

1. Glucose
2. Fructose
3. Galactose

Question 16

How is the disaccharide sucrose made?

Answer 16

Glucose + Fructose

Question 17

How is lactose made?

Answer 17

Glucose + Galactose

Question 18

How does a condensation reaction occur?

Answer 18

2 hydroxyl groups react, leaving an O in the bond and “condensing” water out.

Question 19

How is cellulose formed?

Answer 19

Cellulose is formed from the glycosidic bonding of multiple beta glucose molecules, with every other one flipped so that the bonding can occur.

Question 20

How is cellulose organised into cellulose fibres?

Answer 20

Cellulose chains hydrogen bond with each other forming microfibrils.
These then group into macrofibrils
These then bundle together to form cellulose fibres, which are strong and insoluble.

Question 21

How do you test for reducing sugars?

Answer 21

1. Place the sample in a boiling tube
2. Add an equal volume of benedict’s reagent = Copper (II) sulfate
3. Heat the mixture in a boiling water bath for five minutes.
   If the solution turns brick-red, there is a reducing sugar.

Question 22

How do you test for non-reducing sugars?

Answer 22

Add hydrochloric acid and boil, then perform the normal test for reducing sugars. However, results may be a range of colours so must be referred to with a chart. If precise is needed, a colorimeter may be used to calculate %absorbance

Question 23

How do you test for starch?

Answer 23

Add a dew drops of iodine dissolved in potassium iodide solution, if solution changes to dark purple/black then starch is present.

Question 24

How are phospholipids formed?

Answer 24

A phosphate group replaces one of the fatty acid tails, forming a molecule with a hydrophilic head and a hydrophobic tail.

Question 25

What does the hydrophobic/philic properties of phospholipids mean?

Answer 25

They can form a bilayer, where the tails point to the centre of the sheet whilst the hydrophilic heads protect them from the water.

Question 26

What are sterols?

Answer 26

Alcohol molecules that have the same hydrophobic/philic characteristics as phospholipids.

Question 27

What is the function of cholesterol?

Answer 27

is positioned between the phospholipid tails in cell membranes. This adds stability to the cell membranes and helps to regulate fluidity by keeping membranes fluid at lower temperatures and stopping them from becoming too fluid at high temperatures.

Question 28

How many common amino acids are there?

Answer 28

20

Question 29

How do we get amino acids?

Answer 29

From digesting what we eat

Question 30

How are amino acids bonded?

Answer 30

A peptide bond forms between the amine group on one and the carboxyl group on another

Question 31

When many amino acids join, what is the result?

Answer 31

A polypeptide chain

Question 32

What are the levels of protein structure and how are they formed? What bonds are involved in each step?

Answer 32

Primary structure - The sequence in which amino acids are joined - Peptide bonds Secondary structure - Hydrogen bonds form in the chain. This can happen in two ways. A chain may coil and H-bond with itself to form an alpha helix, or may H-bond with another to form a beta pleated sheet. - Hydrogen bonds Tertiary structure - Folding of the protein. This is caused from interactions in the R groups i.e. - Hydrophobic/Philic interactions Hydrogen bonds Ionic bonds between oppositely charged ions Disulfide bonds - Form between sulfur atoms Quaternary structure - From the joining of two or more polypeptide chains - Same as tertiary structure/

Question 33

What are the main types of proteins?

Answer 33

Globular - Compact, soluble, spherical proteins. Conjugated - Globular proteins with a prosthetic group which is a non-protein component. Fibrous proteins - Long, insoluble, strong molecules.

Question 34

What are some examples of each type of protein: Glolar Conjugated Fibrous

Answer 34

Globular - Insulin Conjugated - Haemoglobin, Catalase Fibrous - Keratin, Collagen, Elastin

Question 35

What does having double bonds mean in fatty acid tails of lipids?

Answer 35

Having a double bond causes the tails to kink / bend, and so they cannot pack as closely together. This increases the fluidity of a membrane with them, and can make them liquid at room temperature.

Question 36

What food test can you do to work out if a protein is present in a sample?

Answer 36

Place your liquified food sample in a test tube Add equal volumes of potassium/sodium hydroxide and copper sulfate to the test tube to form a blue precipitate. Heat to when it is a solution Add egg white / milk, and if there is a protein, the blue colour will change to purple.