Topic 1

Question 1

Test for non-reducing sugars

Answer 1

Boil with acid AND neutralise

Heat with benedicts

Red precipitate

Question 2

Difference between cellulose and glycogen

Answer 2

Cellulose made of Beta glucose
Glycogen made of alpha glucose

Cellulose has straight chain
Glycogen is branched

Cellulose has straight chain
Glycogen is coiled

Cellulose has 1-4 glycosidic bonds
Glycogen has 1-4 AND 1-6 glycosidic bonds

Question 3

Features of starch which make it a good storage molecule

Answer 3

Insoluble - Doesnt affect water potential

Branched/Helical - Makes molecule compact

Large molecule - Cannot cross cell membrane

More ends - Fast enzyme action

Question 4

Structure of glycogen

Answer 4

Polymer of alpha glucose

Joined by glycosidic bonds

Question 5

How does glycogen act as a source of energy

Answer 5

Hydrolysed to glucose

Glucose used in respiration

Question 6

How is cellulose adapted to its function

Answer 6

Long and straight chains

Become linked together by many hydrogen bonds to form fibrils

Provide strength to cell wall

Question 7

How to test for presence of a lipid in a sample of food

Answer 7

Add ethanol
THEN add water
AND shake

Milky/White emulsion

Question 8

How is triglyceride molecule formed

Answer 8

ONE glycerol and THREE fatty acids

Condensation reactions AND removal of THREE molecules of water

Ester bonds formed

Question 9

How is ester bond formed in phospholipid

Answer 9

Condensation reaction

Between glycerol and fatty acid

Question 10

Describe the induced fit model

Answer 10

Substrate binds to the active site

Active site changes shape slightly so it is complementary to substrate

Question 11

How do competitive inhibitors decrease the rate of enzyme controlled reactions

Answer 11

Inhibitor similar shape to substrate

Binds to active site

Reduces enzyme substrate complexes forming

Question 12

How does the structure of a protein vary depending on the amino acids it contains

(5 Marks)

Answer 12

Structure is determined by position of amino acid

Primary structure is sequence of amino acids

Secondary structure formed by hydrogen bonding

Tertiary structure formed by interactions

Creates active sites in enzymes

Quarternary structure contains multiple polypeptide chains

Question 13

How does active site of enzyme cause a high rate of reaction

Answer 13

Lowers activation energy

Induced fit causes active site to change shape

Enzyme substrate complex causes bonds to break

Question 14

Describe the test for a protein in a solution

Answer 14

Add biuret reagent

Positive result - Purple/Lilac

Question 15

Similarities between dipeptides

Answer 15

Amine group (NH2) at end

Carboxyl group (COOH) at end

2 R groups

All contain C and H and N and O

Question 16

Difference between dipeptides

Answer 16

Different R groups

Question 17

How do non competitive inhibitors reduce the rate of an enzyme controlled reaction

Answer 17

Attaches to the enzyme at a site other than the active site

Changes shape of active site

So active site and substrate are no longer complementary

So no substrate can bind

Question 18

Describe how a peptide bond is formed between two amino acids to form a dipeptide

Answer 18

Condensation reaction

Between amine group and carboxylic group

Question 19

How is the secondary structure of a polypeptide produced by binds between amino acids

Answer 19

Hydrogen bonds

Forming beta pleated sheets
Or
Forming alpha helix

Question 20

Why can 2 proteins have the same number and type of amino acids but different tertiary structures

Answer 20

Different sequence of amino acids

Forms ionic/hydrogen/disulfide bonds in different places

Question 21

How does a formation of an enzyme substrate complex increase the rate of reaction

Answer 21

Reduces activation energy

Due to bending bonds

Question 22

What is the definition of a genetic code

Answer 22

More than one codon codes for a single amino acid

Question 23

Variables that can be controlled in an enzyme controlled reaction

Answer 23

Initial substrate concentration

Enzyme concentration

pH

Question 24

Describe the structure of DNA

Answer 24

Polymer of nucleotides

Each nucleotide formed from deoxyribose, a phosphate group and organic base

Phosphodiester bonds between nucleotides

Double helix held by hydrogen bonds

Pairing between adenine, thymine, guanine and cytosine

Question 25

How is a phosphodiester bond formed between 2 DNA nucleotides

Answer 25

Condensation reaction Between phosphate and deoxyribose

Question 26

Role of single stranded DNA fragments in DNA replication

Answer 26

Template Determines order of nucleotides

Question 27

Role of DNA nucleotides

Answer 27

Forms complementary pairs

Question 28

Features of DNA and how they are important in DNA replication

Answer 28

Weak hydrogen bonds between bases - Allows 2 strands to separate 2 strands - Both can act as template Complementary base pairing - Allows accurate replication

Question 29

Why do enzymes on DNA strands act in opposite directions

Answer 29

DNA has antiparallel strands Enzymes have active sites with specific shape Only substrates with complementary shape can bind with active site of enzyme Shape of the nucleotides is different

Question 30

How is an ATP molecule formed from its component molecules

Answer 30

Components - Adenine, Ribose, 3 phosphates Condensation reaction Involving ATP synthase

Question 31

Ways in which ATP is a suitable energy source for cells to use

Answer 31

Releases relatively small amounts of energy Releases energy instantaneously Phosphorylates other compounds, making them more reactive Can be rapidly re-synthesised Does not leave cells

Question 32

How is the hydrolysis of ATP used in cells

Answer 32

To provide energy for other reactions To add phosphate to other substances and make them more reactive

Question 33

Properties of water that are important in the cytoplasm of cells

Answer 33

Polar molecule- Acts as a solvent Reactive - Takes place in hydrolysis

Question 34

Describe the events which take place during DNA replication.

Answer 34

Unwinding of DNA's double helix structure Through DNA helicase breaking the hydrogen bonds between base pairs Each strand acts as a template Addition of free nucleotides to the exposed polynucleotide strand DNA polymerase being involved in the condensation reactions that join the nucleotides Forming a new polynucleotide strand

Question 35

The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how.

Answer 35

DNA replicated Involving complementary base pairing 2 sister chromatids Each chromatid moves to opposite poles of the cell

Question 36

Properties of water

Answer 36

Meabolite - In condensation reactions Solvent - So metabolic reactions can occur High specific heat capacity - Buffers changes in temperature Large latent heat of vaporisation - So provides cooling effect Cohesion - So supports columns of water

Question 37

Role of iron ions, sodium ions and phosphate ions

Answer 37

**Iron ions** Haemoglobin associates with oxygen **Sodium ions** Cotransport of glucose As sodium moved out by Na/K pump Affects water potential Creates sodium diffusion gradient **Phosphate ions** Used to produce ATP Hydrophilic part of phospholipid bilayer