Biological Molecules

Question 1

What is the test for reducing sugars?

Answer 1

1. Add the food sample make sure it is in liquid form
2. Add equal volume of Benedict’s
3. Heat the mixture
4. If sugar present then goes from blue to orange, red

Question 2

What is the definition of a monomer?

Answer 2

Smaller units from which larger molecules are made

Question 3

What is the definition of a polymer?

Answer 3

Large number of monomers joined together

Question 4

What is a condensation reaction?

Answer 4

Joining of two molecules with the formation of a chemical bond and involves the elimination of a water molecule

Question 5

What is a hydrolysis reaction?

Answer 5

Breaks a chemical bond between two molecules and involves the use of a water molecule

Question 6

What two monosaccharides make maltose?

Answer 6

Two alpha glucose molecules

Question 7

What two monosaccharides make sucrose?

Answer 7

Alpha glucose molecule and a fructose molecule

Question 8

What two monosaccharides make lactose

Answer 8

A glucose molecule and a fructose molecule

Question 9

What is the structure of a-glucose and B-glucose?

Answer 9

A-glucose OH group on the bottom
B-glucose OH group on the top

Question 10

What is the test for non reducing sugars?

Answer 10

1. Sample in liquid form
2. Add Benedict’s reagent
3. Place in boiling water no colour change reducing sugar not present
4. Ass new food sample add HCl and boil hydrolyses disaccharide
5. Add sodium hydrogencarbonate
6. Heat with Benedict’s
7. If present turns an orange brown

Question 11

What is the test for starch?

Answer 11

1. Add food sample
2. Add iodine
3. Turns blue-black

Question 12

What are the features of starch?

Answer 12

1. Insoluble
2. Does not diffuse out of cells
3. Compact lots in small space
4. A-glucose used in respiration
5. Many ends so enzymes can act on it

Question 13

What are the features of cellulose?

Answer 13

1. Straight un branched chains
2. Collective strength of hydrogen bonds
3. Provides strength to the cell wall

Question 14

What are the features of glycogen?

Answer 14

1. Insoluble
2. Does not diffuse out of cells
3. Compact lots stored in small space
4. Highly branched can be acted on by enzymes

Question 15

How are triglycerides formed?

Answer 15

A condensation reaction of one glycerol molecule and 3 fatty acids. This forms an ester bond

Question 16

What is the structure of a phospholipid ?

Answer 16

One glycerol, 2 fatty acids and a phosphate group.

Question 17

What are the properties of triglycerides?

Answer 17

1. High ratio of energy storing carbon hydrogen bonds so good source of energy
2. Low mass to energy ratio good storage molecule good for animals less mass to carry
3. Large non polar so insoluble
4. Release water when oxidised

Question 18

What are the properties of phospholipids?

Answer 18

1. Polar molecules hydrophilic head and hydrophobic tail this means that they can form a bilayer and a hydrophobic barrier between the inside and outside of the cell
2. Can form glycolipids which are important in cell recognition

Question 19

What is the test for lipids?

Answer 19

1. Add the sample
2. Add the ethanol
3. Shake and then add the water
4. A milky while emulsion indicates a lipid present

Question 20

What is the general structure of an amino acid?

Answer 20

R
|
H2N——C—-COOH
|
H

Question 21

How are dipeptides formed?

Answer 21

In a condensation reaction between two amino acids

Question 22

What is a primary structure of a protein?

Answer 22

A sequence of amino acids in a polypeptide chain

Question 23

What is a secondary structure of a protein?

Answer 23

The folding of a polypeptide creating more hydrogen bonds can be hydrogen bonds and B pleated sheets

Question 24

What is the tertiary structure of a protein?

Answer 24

Further coiling and folding includes ionic, disulphide and hydrogen bonds

Question 25

What is the quaternary structure of a protein?

Answer 25

Different polypeptide chains associated with prosthetic groups into large complex molecules

Question 26

What is the test for proteins?

Answer 26

1. Place a sample of the solution and add biuret reagent 2. If the solution turns purple there is a peptide bond present if there is no protein remains blue

Question 27

What is the role of an enzyme?

Answer 27

Lowers the activation energy for the reaction it catalyses

Question 28

Describe the induced fit model for an enzyme?

Answer 28

When a substrate is present the enzyme is induced to change shape at the active site and to fit together with the substrate The enzyme and the substrate join to form an enzyme substrate complex the enzyme does its job and the products are released

Question 29

Explain the effect that temperature has on an enzyme?

Answer 29

1. Kinetic energy increases so more molecules collide with each other resulting in more enzyme substrate complex’s 2. The temperature rise breaks hydrogen bonds causing the active site to change shape which slows the rate of reaction 3. Eventually the enzyme will denature so the enzyme does not function again causing a falling line 4. Enzymes have an optimum temperature the enzymes work at

Question 30

What effect does PH have on an enzyme?

Answer 30

1. The change in PH alters the charges on the amino acids at the active site so the substrate can no longer bind 2. This may cause the bonds in the tertiary structure to break so the active site changes shape 3. pH changes more likely to reduce enzyme activity

Question 31

What is the effect on enzyme concentration on rate of reaction?

Answer 31

1. At low enzyme concentrations there are few enzymes to allow all substrate molecules to have an active site 2. Balanced concentration all substrate molecules can occupy an active site 3. High enzyme concentrations have no effect as there is enough active sites to occupy the substrate

Question 32

What is the effect of substrate concentration on rate of reaction?

Answer 32

1. At low concentration few molecules can occupy the active site 2. At balanced all the active sites can be occupied 3. High substrate concentration has no effect because there is not enough active sites

Question 33

What effect do competitive inhibitors have?

Answer 33

1. They have a similar shape to the substrate so they can occupy the active site 2. If substrate concentrations are increased there is a reduced effect on the inhibitor 3. When the inhibitor leaves there can be another molecule that can bind to the active site

Question 34

What effect do non-competitive inhibitors have?

Answer 34

1. They attach a an allosteric site this alters the shape of the active site 2. An increase in substrate concentration has no effect on the inhibitor