2.1.2 Biological Molecules Part 1 COMPLETE Flashcards
Condensation reactions
Water is produced as two Hs and one O is removed when molecules are being bonded together.
Hydrolysis
A molecule of water is used to give the molecules that are being broken apart a hydrogen and/ or an oxygen
Inorganic ions
Atoms or molecules with an uneven charge through the loss or gain of electrons. Once dissolved in water they become electrolytes
Polarity
Due to an uneven distribution of charges across a molecule
Hydrogen Bonds
Weak interactions that can occur whenever molecules contain slightly negatively charged ions that can bond with slightly positive hydrogens.
Properties of Water
- Liquid
- Density
- Cohesion and surface tension
- Act as a solvent
- Polar
Why waters a liquid
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.
Uses of Water
- Provides habitats
- Major component in tissues
- Provides a reaction medium
- Effective transport medium
Waters Density
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
Waters Cohesion and Water Tension
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
Water as a solvent
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
Why do salts dissolve in water
Salt is an ionic compound with positive and negative parts. The O- and H+ surround them allowing it to dissolve
Waters high SHC
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
Water High Latent Heat of Vaporisation
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
Carbohydrates Function and Examples
Energy store, source and for structure
Examples: Monosaccharides, disaccharides and polysaccharides
Monosaccharides
The simplest carbohydrates (Monomers)
Sweet and soluble
Tend to be ring structures or straight chains
Example: Triose, Pentose, Hexose
Glucose
C6 H12 O6
Has two forms Alpha (OH on the bottom) and Beta (OH diagonal)
Disaccharide’s
Sweet, soluble and form crystals
Examples: Sucrose, Maltose, Lactose
What holds together the Monosaccharides
1-4 or 1-6 Glycosidic Bonds
Formed in a condensation reaction
Testing for Reducing Sugars
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
Testing for Non Reducing Sugars
Sugars that don’t have/ Can’t form aldehyde groups. They give a negative result to the Benedict’s Test
Reagent Strips
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
Explain Polysaccharides with examples
Polymers made from multiple monosaccharides, undergone condensation reactions.
Examples: Amylose, Glycogen and Cellulose
Polysaccharide Properties and Function
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.
Starch
Storage in plants (Polysaccharides)
Insoluble
Compact
Easily Hydrolysed
Amylose
Condensation occurs between A glucose to make 1-4 bonds.
Produce compact helices
Insoluble
Dark blue/ black in iodine
Amylopectin
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
Glycogen
1-4 and 1-6 bonds between A glucose, storage in animals
Has lots of branches, more compact than starch
Cellulose
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
Quantitative methods to determine concentration
Colorimetry
Test the conc. based on how much light is transmitted through a solution
Explain Lipids with examples
Large complex molecules but are not polymers
Examples: Triglycerides, phospholipids, sterols
Similarities between lipids
All contain hydrocarbons
All soluble in organic solvents (alcohol)
Insoluble in water
Functions of lipids
- Energy storage
- Structural components
- Thermal + Electrical insulation
- Waterproofing
- Buoyancy
- Mechanical protection
Testing for Lipids
- Crush material with ethanol and decant the suspension to remove solid material
- Carefully pour the ethanol mixture onto some water in another tube
- If a milky emulsion forms in water a lipid is present
Triglycerides
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
How double bonds affect the molecule
Unsaturated double bonds leads to kinks in the chain
This lowers the boiling point of the molecule
Polyunsaturated have multiple double bonds
Esterification
Condensation reaction
Forms an ester bond
3 fatty acids on 1 glycerol
Phospholipids
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
Phospholipid reactions to water
- 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
Phospholipids for cell membranes
- Increases their stability as they never move to be exposed to water
- Selective Permeability as only let small non polar substances through
Membrane fluidity
Higher fluidity when the phospholipids contain unsaturated fatty acids
Advantages of Lipid respiration
- 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
Explain Sterols with examples
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
Explain Cholesterol
Helps to regulate membrane fluidity in different temperatures. Also used to form steroid hormones
Composed of 4 carbon based rings joined together
