Topic 1 - A: Biological molecules

Question 1

Difference between monomers and polymers

Answer 1

Polymers are large, complex molecules composed of long chains of monomers joined together
Monomers are small basic molecules that can form a polymer

Question 2

What is a condesation reaction

Answer 2

Forms a chemical bond between monomers and releases water

Question 3

What is a hydrolisis reaction

Answer 3

Breaks chemical bonds between monomers using a water molecule

Question 4

What is a monosaccharide

Answer 4

Contains elements H, C and O. Monosaccharides make up carbohydrates

Question 5

Draw the two types of glucose

Answer 5

Alpha - OH is on bottom
Beta - OH is on top

Question 6

What is a dissacharide

Answer 6

Formed when two monosaccharides join together via a condensation reaction - a glycosidic bond forms between two monosaccharides as a molecule of water is released

Question 7

Describe benedicts test for reducing sugars.

Answer 7

Add benedicts reagent (blue) to your sample and heat in a water bath thats been brought to boil. If the test is posotive it will turn brick red, if negative it will stay blue

Question 8

How to test for non reducing sugar

Answer 8

After having tested for a reducing sugar the solution may have stayed blue, this means there could still be a non reducing sugar still present. Heat a new sample with dilute hydrochoric acid then neutralise with alkaline. Then you must heat with Benedicts reagent, if the sample turns brick red, then there is a non-reducing sugar present, if it stays blue, there is neither a non-reducing sugar or a reducing sugar

Question 9

How is Sucrose formed

Answer 9

Glucose + Fructose

Question 10

How is Lactose formed

Answer 10

Glucose + Galactose

Question 11

Function of starch

Answer 11

Plants store excess glucose as starch
Starch is a mixture of to polysaccharides :
Amylose: long unbranched chain of a-glucose
coiled structure make it compact so its good for storage
Amylopectin: long branched chain of a-glucose
as it has more side branches , enzymes can break it down more efficiently
therefore it is good for rapid energy
release.

Question 12

Function of glycogen

Answer 12

Animal cells store excess glucose as glycogen.
It has a very similar structure as amylopectin, except it has loads more side branches, this means the glucose can be released at a very high rate
Its also very compact meaning it is good for storage

Question 13

Function of cellulose

Answer 13

Cellulose is a long unbranched chain of beta glucose unlike Starch and Glycogen
When the b-glucose molecules bond they are linked together by weak hydrogen bonds to create strong fibres called microfbrils. These strong fibres mean cellulose provides structural support for cell walls in plants.

Question 14

How to test for presence of starch

Answer 14

Add iodine dissolved in pottasium iodide solution to the test sample. If starch is present, the colour will change from orange/yellow to blue

Question 15

What are tryglicerydes

Answer 15

One molecule of glycerol with three fatty acids attached to it.
Fatty acids have long tails made of hydrocarbons
These tails are hyrophobic

Question 16

What is the difference between saturated and un-saturated fatty acids

Answer 16

Saturated-no double bond
Unsaturated-double bond present between carbon atoms

Question 18

How are triglycerides formed

Answer 18

formed by condensation reaction
As the fatty acid and glycerol join a watere molecule is released.

Question 19

What are phospholipids

Answer 19

one of the fatty acids is replaced by a phosphate group. The phosphate group is hydrophilic and the fatty acid is still hydrophobic like regular.
These are stored in the cell membrane

Question 20

Properties of triglycerides and phospolipids

Answer 20

Triglyceride: Long hydrocarbon tails of fatty acids contain alot of energy
Insoluble so they dont affect water potential meaning the cell will swell
Phospholipid: Make up the bilayer of the cell membrane and control what enters and leaves a cell
The heads are hydrophillic and their tales are hydrophobic so they form a double layer with their heads facing outwards towards the water and their tales on the inside which are hydrophobic meaning water-soluble substances cant pass through easily

Question 21

Describe the emulsion test

Answer 21

Shake the test substance with ethanol for about a minute then pour solution into water
Any lipid will show as milky emulsion

Question 22

What reaction links amino acids together and what bond forms between them

Answer 22

Condensation reaction
Peptide reaction

Question 23

What reaction breaks down dipeptides and polypeptides

Answer 23

hydrolisis

Question 24

What is the primary structure

Answer 24

The sequence of amino acids in the polypeptide chain

Question 25

What is the secondary structure

Answer 25

The polypeptide chain doesn’t remain flat

i.e. Hydrogen bonds form between the amino acids in the chain making it automatically coil

Question 26

What is the tertiary structure

Answer 26

The coiled or folded chain of amino acids is folded or coiled even further
Further bonds created (hydrogen and ionic)
Disulfide bridges also form

Question 27

What is the quaternary structure

Answer 27

Some proteins are made from several seperate polypeptide chains held together by bonds
The quaternary structure is the way these polypeptide chains are assembled together.

Question 28

How to test for proteins

Answer 28

BUIRET TEST
The test solution must be alkaline-to do this add a few drops of sodium hydroxide solution
Then add copper sulfate solution
If there is a protein present the solution will turn purple, if there’s no protein it will stay blue

Question 29

What is the induced fit model

Answer 29

Substrate binds into active site, but the active site changes slightly to fit substrate. The products are then produced like normally

Question 30

What factors affect enzyme activity

Answer 30

Temperature -higher temperature, higher rate of reaction until a certain temperature where the enzyme will denature
pH - Generally optimum pH is 7
Substrate concentration - The higher the substrate concentration the higher the rate of reaction, this is true until you reach the point of saturation where all the active sites are filled and it will not make a difference if there are more substrates
Enzyme concentration works the same as the above

Question 31

Competitive inhibitors

Answer 31

molecules that have a similar shape to that of the substrate molecules. They compete with the substrate to block the active site from the substrate. no reaction takes place with them, they purely block the active site from reacting
In the long run it will reach the same rate of reaction it will just take longer to reach this point

Question 32

Non competitive inhibitor

Answer 32

Bind to the enzyme away from the active site changing the shape of the active site meaning substrate molecules can no longer fit to the active site.
This means rate of reaction will never be reached as the shapes are being changed forever.