Biological Molecules Flashcards
What is the evidence for evolution?
- Information that supports theory of evolution- all organisms on earth are descended from one or a few common ancestors and that they have changed and diversified over time
- Life is based on carbon
- All have same carbon-based compounds that interact in similar ways (use same nucleic acids as genetic material and same amino acids to build proteins)
- Similarities suggest that animals and plants have a common ancestor
Polymers
Large, complex molecules composed of long chains of monomers joined together (carbohydrates, proteins and nucleic acids)
Monomers
Small, basic molecular units that can form a polymer (monosaccharides, amino acids and nucleotides)
Condensation reaction
Forms a chemical bond between monomers by releasing a molecule of water
Hydrolysis reaction
Breaks a chemical bond between monomers by adding a water molecule
Monomers of carbohydrates
Monosaccharides (glucose,galactose and fructose)
Starch
- Found in many parts of plants like small granules and starch
- Plants store excess glucose as starch
- When a plant needs energy, starch is broken down to release the energy
- Starch is a mixture of 2 a-glucose polysaccharides= amylose and amylopectin
Amylose
- Long, unbranched chain of alpha glucose
- Angles of glycosidic bonds give it a coiled structure, almost like a cylinder
- Makes it compact so it’s really good for storage because you can fit it into a small space
- Hydrogen bonds between alpha glucose molecules helps to hold amylose in its helical structure
Amylopectin
- Long, branched chain of alpha glucose
- It’s side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily
- Means that glucose can be released quickly
Starch Properties
- Insoluble in water so doesn’t affect water potential and cause water to enter cells by osmosis, which would make them swell (this is good for storage)
- Main role is energy storage
- Large and insoluble- can’t diffuse out of cells
- Compact- lots can be stored in a small space
- Branched form has many ends so glucose released rapidly
- Alpha glucose easily transported and readily used in respiration
Glycogen
- Highly branched and shorter chains
- Animals store excess glucose as glycogen (another polysaccharide of alpha glucose)
- Structure similar to amylopectin, except more side branches
- Loads of branches means stored glucose can be released quickly, which is important for energy release in animals
- Very compact molecule so good for storage
Polysaccharide formation
- Large,insoluble molecules
- Formed when more than 2 monosaccharides join together by condensation reactions (loads of a-glucose molecules joined together by glycosidic bonds to form amylose)
Hydrogen Bonding
- Electrons within a molecule are unevenly distributed
- One side is more negative (polarised so polar molecule)
- Weak electrostatic bond between positive of one molecule and negative of another
- Gives water its physical properties
Metabolism
All the chemical processes that take place in living organisms
Molar solution
Solution that contains one mole of solute in each litre of solution (mole is molecular mass expressed as grams)
Reduction
Chemical reaction involving gain of electrons or hydrogen
Reducing sugar
Can donate (or reduce) another chemical (benedict’s reagent)
Why should an excess of Benedict’s be used?
To make sure all the sugar reacts
What should you do if sample is solid in sugars test?
Grind with water and filter out solid
What is Benedict’s?
Alkaline solution of copper (II) sulfate
What conditions won’t BR work in?
Acidic conditions (test to see if alkaline using pH paper)
Test for Reducing sugars
- Reducing sugars include all monosaccharides and some disaccharides (maltose and lactose)
- Add blue BR to a sample and heat it in a water bath which has been brought to boil
- If positive a coloured precipitate will be formed (green-yellow-orange-brick red)
Measuring amount of sugar
- Higher concentration of reducing sugar, the further the colour change goes (can use this to compare amounts in different solutions)
- Could filter solution and weigh precipitate or remove precipitate and use colorimeter to measure absorbance of remaining BR
Testing for Non-reducing sugar
- (sucrose) First have to break down sugar into monosaccharides
- Get a new sample and add dilute hydrochloric acid (hydrolysed disaccharides into monosaccharides), carefully heat it in a water bath that’s been brought to boil
- Then neutralise it by adding sodium hydrogencarbonate
- Carry out benedict’s as usual
Disaccharide formation
- When 2 monosaccharides join together by a condensation reaction (glycosidic bond forms)
- Sucrose forms from glucose and fructose
- Lactose forms from glucose and galactose
- 2 a-glucose molecules forms maltose
Glucose
- Hexose sugar- monosaccharide with 6 carbon atoms in each molecule
- Have alpha and beta glucose (isomers of each other)
