Biology Unit 1 Booklet 3

Question 0

Test for non-reducing sugars (3)

Answer 0

Heat with Benedicts reagent and no colour change (1)
Boil with dilute HCl and then neutralise with NaHCO3 (1)
Reheat with Benedicts reagent and colour change from blue to brick-red (1)

Question 1

Test for reducing sugars (2)

Answer 1

Heat with Bendicts reagent (1)

Colour change from blue to brick-red (1)

Question 2

Test for starch (2)

Answer 2

Add iodine in potassium iodide solution (1)

Colour from brown to blue-black (1)

Question 3

Test for protein (2)

Answer 3

Add biuret reagent to the sampe and add NaOH and CuOH to neutralise (1)
Colour change to form a lilac band (1)

Question 4

Emulsion test for lipids (2)

Answer 4

Add ethanol and shake (1)

Add water and goes milky (1)

Question 5

Protein structure (6)

Answer 5

Amino acids join together as primary structure (1)
By a condensation reaction (1)
Forming peptide bonds; specific structures form during secondary folding - alpha helix and beta pleated sheet (1)
Hydrogen bonds form between O and H atoms (1)
Secondary structure further folds to form tertiary structure held together by ionic and disulphides bonds (1)
Quaternary structure is where more than one polypeptide chain folds together e.g. Haemoglobin (1)

Question 6

Increased temperature and reaction rate (4)

Answer 6

Particles have more kinetic energy (1)
Therefore they move more (1)
So there are more collisions (1)
So more enzyme-substrate complexes form (1)

Question 7

Activation energy (2)

Answer 7

The minimum amount of energy required to bring particles in close contact (1)
So that they will collide and react (1)

Question 8

Lock and key theory (3)

Answer 8

Enzyme have an active site of specific shape (1)
The substrate that is a complementary shape (1)
Binds to the active site (1)

Question 9

Induced fit model (2)

Answer 9

The substrate has a complementary shape to the active site of the enzyme (1)
Upon binding the active site of the enzyme moulds around the substrate (1)

Question 10

Enzyme Denaturation (5)

Answer 10

Heat above the optimum to break hydrogen bonds (1)
This causes the tertiary structure to unfold (1)
Active site is distorted/ changes shape (1)
Substrate can no longer bind to active site (1)
Fewer enzyme-substrate complexes form (1)

Question 11

Effects of changes on pH on enzyme activity (4)

Answer 11

Ionic bonds holding the tertiary structure break (1)
Active site distorts and substrate no longer binds to active site (1)
Charges in amino acids in active site affected (1)
Fewer enzyme-substrate complexes form (1)

Question 12

Competitive enzyme inhibitor (4)

Answer 12

Inhibitor has a similar shape to the substrate (1)
Binds competitively for the active site (1)
As it has a complementary shape (1)
Therefore enzyme-substrate complexes can no longer form (1)

Question 13

Non-competitive enzyme inhibitor (4)

Answer 13

Inhibitor binds to regulatory region as it does not have a complementary shape to the active site (1)
This causes a conformational change in the shape of the active site (1)
Meaning the substrate can no longer bind (1)
Therefore enzyme-substrate complexes can no longer form (1)

Question 14

How starch digestion occurs in the human body (6)

Answer 14

Salivary amylase (1)
Breaks down starch to maltose (1)
Maltase (1)
Breaks down maltose to glucose (1)
This is hydrolysed (1)
Enzymes catalyse the breakdown of the glycosidic bond (1)

Question 15

How lactose intolerance causes diarrhoea (3)

Answer 15

Undigested lactose in small intestines causes water potential to become more negative (1)
Water moves from epithelial cells into lumen (1)
By osmosis (1)

Question 16

Adaptions of micro villi for efficient diffusion (4)

Answer 16

Increase surface area (1)
Thin walled therefore reduce length of diffusion pathway (1)
Able to move and so maintain a concentration gradient (1)
Well supplied with blood vessels to maintain a concentration gradient (circulation of blood) (1)

Question 17

Co-transport of glucose (7)

Answer 17

Na+ ions actively pumped out of epithelial cells (1)
Into blood (1)
Maintaining a low concentration of sodium in the cell (1)
Glucose moves into cell with sodium (1)
Via membrane protein- this is co-transport (1)
Glucose moves from cells into blood (1)
By facilitated diffusion (1)