Biological molecules pt1 Flashcards
Define metabolism
The sum total of all biochemical reactions taking place in an organism
What are anabolic reactions?
Building smaller molecules into larger ones. Often involves condensation and forms polymers
What are catabolic reactions?
Involves breaking down large molecules into small ones. Often involves hydrolysis
Condensation
Two molecules are joined together when a covalent bond is formed by the elimination of water.
Hydrolysis
A molecule is broken down when a covalent bond is broken by the addition of water.
Anion
Negatively charged ion
Cations
Positively charged ion
Carbohydrates main functions
Energy source e.g glucose
Energy store e.g starch
Structure e.g cellulose
3 main types of carbohydrates
Monosaccharides (single, simple molecules)
Disaccharides (molecules made by joining two single sugars together)
Polysaccharides (polymers made by joining many single sugars together)
Monosaccharides are…
Soluble in water
Sweet tasting
Crystalline
Glucose
C6H12O6
alpha glucose and beta glucose
two alpha glucose joined to make maltose
hundreds of alpha glucose joined to make glycogen and starch
Hundreds of beta glucose molecules joined to make cellulose
ABBA- alpha below and beta above
Draw alpha and beta glucose
See notes.
Disaccharides
Two alpha glucose joined by condensation to make maltose
maltose= disaccharide
The covalent bond formed by condensation is a 1,4 glycosidic bond
Tests for sugars (reducing sugars)
all monosaccharides and many disaccharides are reducing sugars
Reducing sugar is heated with Benedict’s solution (pale blue solution of alkaline copper II sulphate)
Sugar is reduces copper sulphate to form a Brick Red precipitate.
Goes to green- orange-brick red
Tests for sugars (non-reducing sugars)
Do the Benedict’s test for reducing sugar to make sure the result is negative and the solution stays pale blue.
Then boil the non reducing sugar with hydrochloric acid (hydrolyses molecule)
Cool the sample and neutralise with sodium hydrogen carbonate- breaks glycosidic bond
Do the Benedict’s test on the hydrolysed sample- a brick red precipitate will form.
Quantitative test for glucose
Benedict’s test is qualitative- tells if reducing sugar is present or not
Test can be made quantitative to find out how much reducing sugar is present
How does the quantitative test work
More reducing sugar= more copper sulfate used up in a reaction= paler Benedict’s solution= paleness can be measured using a colorimeter
How the colorimeter works
Light is shone through sample
Sample is placed a cuvette
cell measures how much light gets through sample
The % of light which gets through the sample is recorded as percentage transmission
How to do the quantitative test
Make up a range of glucose solutions of known concentrations
Do Benedict’s test on the standards
Filter off the precipitates and measure % transmission using colorimeter
Plot a calibration curve of % transmission against glucose concentration
Do Benedicta test n samples, filter and measure % transmission
Use the calibration curve convert transmission readings of samples to glucose concentrations
Starch
An energy store in plants
Mixture of two polysaccharides called amylose and amylopectin
Long chain of hundreds of alpha glucose joined together by 1,4 glycosidic bonds
Insoluble- does not affect water potential
chains of amylose coil into a compact helix shape
Test for starch
Iodine solution added to starch
Positive- blue-black
Negative- yellow-brown
Glycogen
an energy store in animals
Glycogen a polysaccharide polymer of alpha glucose joined by 1,4 glycosidic bond
Glycogen is branched making it compact
branches made by 1,6 glycosidic bonds between alpha glucose molecules
Why are starch and glycogen ideal energy stores?
Compact- a lot stored in a small space
insoluble- Doesn’t affect water potential, no osmotic effect
Unreactive- stable stores of glucose
Easily hydrolysed by enzymes- release glucose quickly when needed
Cellulose
Structural polysaccharide in a plant cell walls
Thousands of beta glucose joined by 1,4 glycosidic bonds formed through condensation
Every second beta glucose rotated 180 degrees
Straight and unbranched- cellulose molecules line up close together forming bundles called microfibrils
microfibrils held together by H bonds to form larger bundles called macrofibrils
Insoluble and very strong
Water
Two H atoms covalently bonded to one O atom
Electrons in these bonds are not shared evenly
O atoms are slightly negative and the H atoms are slightly positive
Held together by hydrogen bonds
An excellent solvent
Its polarity causes it to interact with other polar or charged substances
water molecules cluster around ionic substances and polar molecules and pull the individual ions and molecules apart
Roles of water
Transport medium- good solvent, H bonds make water a liquid at a wide range of temperatures, water can flow as a body carrying dissolved substances
Ice and insulation- Has a lattice structure , ice is less dense than water, floating ice insulates the water below it
Cohesion- H bonds are cohesive and helps to draw water up the xylem during transpiration, also creates surface tension
Environment- large specific heat capacity- large amount of energy needed to raise the temperature, oceans have fairly constant temperatures and provide a stable thermal environment
Reactant- used in hydrolysis reactions
Coolant- high latent heat of evaporation, when water evaporates it draws heat energy from its surroundings
