2.1.2 Biological Molecules Part 1 COMPLETE

Question 1

Condensation reactions

Answer 1

Water is produced as two Hs and one O is removed when molecules are being bonded together.

Question 2

Hydrolysis

Answer 2

A molecule of water is used to give the molecules that are being broken apart a hydrogen and/ or an oxygen

Question 3

Inorganic ions

Answer 3

Atoms or molecules with an uneven charge through the loss or gain of electrons. Once dissolved in water they become electrolytes

Question 4

Polarity

Answer 4

Due to an uneven distribution of charges across a molecule

Question 5

Hydrogen Bonds

Answer 5

Weak interactions that can occur whenever molecules contain slightly negatively charged ions that can bond with slightly positive hydrogens.

Question 6

Properties of Water

Answer 6

• Liquid
• Density
• Cohesion and surface tension
• Act as a solvent
• Polar

Question 7

Why waters a liquid

Answer 7

Hydrogen bonds are constantly shifting as they break and reform. This makes it difficult for molecules to escape by becoming a gas as high amounts of energy are needed.

Question 8

Uses of Water

Answer 8

• Provides habitats
• Major component in tissues
• Provides a reaction medium
• Effective transport medium

Question 9

Waters Density

Answer 9

As temperature falls molecules have less kinetic energy and move less. Therefore more H bonds form. This causes a semi crystalline structure to be made which is less dense than liquid.
The H bonds hold the molecules further apart

Question 10

Waters Cohesion and Water Tension

Answer 10

Molecules are attracted to each other due to the H bonds, this is cohesion. This is how droplets form.
Water can also adhere to other structures i.e. a straw

Question 11

Water as a solvent

Answer 11

Water is polar so polar substances can dissolve in it. The slightly positive and negative parts surround the others keeping the solute apart until they’ve dissolved

Question 12

Why do salts dissolve in water

Answer 12

Salt is an ionic compound with positive and negative parts. The O- and H+ surround them allowing it to dissolve

Question 13

Waters high SHC

Answer 13

Hydrogen bonds restrict movement therefore a relatively large amount of heat energy is required to increase the temp of water.
This means water temperature is fairly stable

Question 14

Water High Latent Heat of Vaporisation

Answer 14

Lots of energy is required to allow the molecules to break away and become gases. This is due to the hydrogen bonds holding it all together

Question 15

Carbohydrates Function and Examples

Answer 15

Energy store, source and for structure

Examples: Monosaccharides, disaccharides and polysaccharides

Question 16

Monosaccharides

Answer 16

The simplest carbohydrates (Monomers)
Sweet and soluble
Tend to be ring structures or straight chains
Example: Triose, Pentose, Hexose

Question 17

Glucose

Answer 17

C6 H12 O6

Has two forms Alpha (OH on the bottom) and Beta (OH diagonal)

Question 18

Disaccharide’s

Answer 18

Sweet, soluble and form crystals

Examples: Sucrose, Maltose, Lactose

Question 19

What holds together the Monosaccharides

Answer 19

1-4 or 1-6 Glycosidic Bonds

Formed in a condensation reaction

Question 20

Testing for Reducing Sugars

Answer 20

Mix solution with Benedict’s solution and heat.
A red ppt. forms because the sugar reacts with copper ions.
Works for all reducing sugars except sucrose

Question 21

Testing for Non Reducing Sugars

Answer 21

Sugars that don’t have/ Can’t form aldehyde groups. They give a negative result to the Benedict’s Test

Question 22

Reagent Strips

Answer 22

Quick ways to test for reducing sugars, simply dip the strip into the solution and compare the colour with a calibration chart.
Can collect quantitative measures of concentration

Question 23

Explain Polysaccharides with examples

Answer 23

Polymers made from multiple monosaccharides, undergone condensation reactions.
Examples: Amylose, Glycogen and Cellulose

Question 24

Polysaccharide Properties and Function

Answer 24

Insoluble in water, not sweet and can’t be crystallised
Therefore are good for compact storage as don’t affect osmosis. They can be broken down into glucose quickly when needed.

Question 25

Starch

Answer 25

Storage in plants (Polysaccharides)
Insoluble
Compact
Easily Hydrolysed

Question 26

Amylose

Answer 26

Condensation occurs between A glucose to make 1-4 bonds.
Produce compact helices
Insoluble
Dark blue/ black in iodine

Question 27

Amylopectin

Answer 27

Condensation occurs between A glucose to make 1-4 bond.
Also contains 1-6 bonds so the structure is branched
Soluble
Red/ Purple colour in iodine

Question 28

Glycogen

Answer 28

1-4 and 1-6 bonds between A glucose, storage in animals

Has lots of branches, more compact than starch

Question 29

Cellulose

Answer 29

1-4 bonds in B glucose, they have to rate so forms straight chains with OH groups projecting from them
These form H bonds with adjacent cellulose
Much stronger so used in the cell wall for structure

Question 30

Quantitative methods to determine concentration

Answer 30

Colorimetry

Test the conc. based on how much light is transmitted through a solution

Question 31

Explain Lipids with examples

Answer 31

Large complex molecules but are not polymers

Examples: Triglycerides, phospholipids, sterols

Question 32

Similarities between lipids

Answer 32

All contain hydrocarbons
All soluble in organic solvents (alcohol)
Insoluble in water

Question 33

Functions of lipids

Answer 33

• Energy storage
• Structural components
• Thermal + Electrical insulation
• Waterproofing
• Buoyancy
• Mechanical protection

Question 34

Testing for Lipids

Answer 34

1. Crush material with ethanol and decant the suspension to remove solid material
2. Carefully pour the ethanol mixture onto some water in another tube
3. If a milky emulsion forms in water a lipid is present

Question 35

Triglycerides

Answer 35

One molecule of Glycerol with three fatty acids held together by ester bonds
They’re insoluble due to hydrophobic tails that cannot form H bonds with H2O
Rich in energy so used as stores

Question 36

How double bonds affect the molecule

Answer 36

Unsaturated double bonds leads to kinks in the chain
This lowers the boiling point of the molecule
Polyunsaturated have multiple double bonds

Question 37

Esterification

Answer 37

Condensation reaction
Forms an ester bond
3 fatty acids on 1 glycerol

Question 38

Phospholipids

Answer 38

A phosphate group replaces one of the fatty acids found in a triglyceride and its ionised.
The head is hydrophilic so half the molecule attracts water, this is essential for membranes

Question 39

Phospholipid reactions to water

Answer 39

• Form a mono layer where the head is inside water and the tails stick out
• Also form bilayers bubbles where the tails point towards the centre

Question 40

Phospholipids for cell membranes

Answer 40

• Increases their stability as they never move to be exposed to water
• Selective Permeability as only let small non polar substances through

Question 41

Membrane fluidity

Answer 41

Higher fluidity when the phospholipids contain unsaturated fatty acids

Question 42

Advantages of Lipid respiration

Answer 42

• Gives twice the amount of energy than standard carbohydrates
• Insoluble so can be stored compactly without affecting the water potential
• More water also released than carbohydrates which may be vital in some organisms

Question 43

Explain Sterols with examples

Answer 43

Complex alcohol molecules that are based on a four carbon ring which is attached to a carbon tail.
The OH is polar and hydrophilic but the rest of the molecule is non polar and therefore hydrophobic

Question 44

Explain Cholesterol

Answer 44

Helps to regulate membrane fluidity in different temperatures. Also used to form steroid hormones
Composed of 4 carbon based rings joined together