Biological Molecules Flashcards
Why is water polar ?
Oxygen is more electronegative than hydrogen, so electrons are more strongly attracted to oxygen. Oxygen is slightly negative and hydrogen slightly positive
How do hydrogen bonds form between water molecules ?
The slightly negative oxygen atom from one water molecule is attracted to the slightly positive hydrogen end of another water molecule
6 properties of water
- Density based on temperature
- High surface tension
- Universal solvent
- High Specific heat capacity
- High latent heat of vaporisation
- Cohesion and adhesion
Why does ice float on water ?
Ice is less dense than water because Hydrogen bonds hold molecules in a fixed position further away from each other
Insulates water to stop it from freezing
Why is the high surface tension of water important for organism ?
Slows water loss due to transportation in plants
Water rises unusually in narrow tubes, lowering demand on root pressure
Some insects can skim across the surface of water
Why is water being a universal solvent important for organisms ?
Many ions and covalently bonded polar substances will dissolve in it
Allows chemical reactions to occur within cells
Metabolites can be transported efficiently
Why is water having a high specific heat capacity important ?
Large amounts of energy is required to change the temperature
Water is able to maintain a constant temperature, which is vital for maintains temperatures optimal for enzyme activity
Why is water having a high latent heat of vaporisation important ?
A lot of energy is needed to change state, which means only a small amount of water is required to evaporate for the organisms to loose a lot of heat
- Provides a cooling affect A lot of energy is needed to change state, which means only a small amount of water is required to evaporate for the organisms to loose a lot of heat
- Provides a cooling affect
Why is water having a high cohesion and adhesion important ?
Cohesion - Allows water to move through the xylem of plants and through blood vessels
Adhesion - Enables water to move up the xylem
How are polypeptides formed?
Condensation reactions between amino acids forming peptide bonds
Refer to GoodNotes
What is the Primary Structure of Protein ?
Order of amino acid sequence
Formed by covalent peptide bonds
What is the Secondary Structure of Protein ?
Folding into repeat patterns (α-helix or β-pleated sheet)
By hydrogen bonds between amine and carboxyl groups
What is the Territary Structure of Protein ?
Overall three-dimensional arrangement of a polypeptide
Determined by interactions between variable side chains
What bonds are involved in the tertiary structure of protein ?
Hydrogen Bonds
Ionic Bonds - Between charged r groups
Disulphide bridges - Strong covalent bonds
What is the Quaternary Structure of Protein ?
Presence of multiple polypeptides or prosthetic groups
What are Conjugated Proteins ?
A protein that consists of a protein combined with a non-protein. The non-protein group is called a prosthetic group
What is the molecule shape of fibrous Proteins ?
Long chains running parallel to each other
What is the molecule shape of Globular Proteins ?
Compact and rounded shape
What is the solubIlity of Fibrous Proteins ?
Insoluble in Water
What is the solubIlity of Globular Proteins ?
Soluble in water
What is the bonding of Fibrous proteins ?
Chains linked by disulphide cross bridges , making proteins very strong and stable
What is the bonding of Globular proteins ?
Hydrophobic groups point into the centre of molecules away from water
What are the functions of Fibrous Proteins ?
Structural
(Keratin,Collagen)
What are the functions of Globular Proteins ?
Functional
(Enzymes,Haemoglobin)
Describe the properties of Alpha Glucose
Small and water soluble
- Easily transported in the bloodstream
How do dissacharides form ?
When 2 monosaccharides are bonded together by glycosidic bonds
How do polysaccharides form ?
When many monosaccharides are joint together by glycosidic bonds
What are 3 examples of monosaccharides ?
glucose, fructose, galactose
What are 3 examples of disaccharides ?
Maltose (Glucose + Glucose)
Sucrose (Glucose + Fructose)
Lactose (Glucose + Galactose)
What are 3 examples of polysaccharides ?
starch, glycogen, cellulose
What is the structure of starch ?
Constructed of two different polysaccharides
Amylose - Linear with 1-4 glycosidic bonds between alpha glucose (Compact)
Amylopectin - Branched with 1-4 and 1-6 glycosidic bonds between alpha glucose
What is the structure of glycogen ?
1-4 and 1-6 glycosidic bonds between alpha glucose, Highly branched
What is the structure of Cellulose ?
Linear 1-4 glycosidic bonds between Beta-Glucose molecules
Beta Molecules must rotate 180°, which causes many hydrogen bonds to form giving it strength
What is the function of starch ?
Storage in plants
What is the function of Glycogen ?
Storage molecule in the liver
What is the function of Cellulose ?
Main structural component in cell walls
What happens in a condensation reaction ?
A chemical bond forms between 2 molecules & a molecule of water is produced
What happens in a hydrolysis reaction ?
A water molecule is used to break a chemical bond between 2 molecules
What is the structure of Amino Acids ?
Refer to GoodNotes
-COOH carboxyl / carboxylic acid group
- R Variable side group consists of carbon chain & may include other functional groups e.g. benzene ring or -OH (alcohol)
-NH² amine/amino group
How do triglycerides form ?
Condensation reaction between 1 molecule of glycerol & 3 fatty acids forms ester bonds
Refer to GoodNotes
Describe saturated fatty acids
Contain only single bonds
Straight-Chain molecules have many contact points
Higher melting point = Solid at room temperature
Found in animal fats
Describe Unsaturated fatty acids ?
Contain C=C double bonds
‘Kinked” molecules have fewer contact points
Lower melting point = Liquid at room temperature
Found in plant oils
Relate the structure of triglycerides to their functions
Insoluble hydrocarbon chain - Used for waterproofing
Slow conductor of heat - Thermal insulation
Less dense than water - Buoyancy of aquatic animals
Describe the structure of phospholipids
Glycerol backbone attached to 2 hydrophobic fatty acids tails & a hydrophilic polar phosphate head
What is the function of phospholipids ?
Forms a phospholipid bilayer - Plasma Membrane
Tails can act as waterproofing
Are phospholipids and triglycerides polymers ?
No, they are not made from small repeating units. They are macromolecules
Describe the structure of cholesterol
Structure of 4 hydrocarbon rings.
Hydrocarbon tail on one side, hydroxyl group on the other side
What is the function of cholesterol ?
Affects the fluidity and permeability of the cell membrane
How to test for proteins ?
Biuret tests
- Add (equal volume) of soidum hydroxide to sample
- Add drops of dilute copper (II) sulfate solution
- Positive result: Colour changed from blue to purple
Negative result: Remains blue
How to test for lipids ?
Dissolve solid samples in ethanol
Add (equal volume) water and shake
Positive result: Milky white emulsion forms
How to test for reducing sugars ?
- Add (Equal Volume) of Benedict’s reagent to a sample
- Heat the mixture in a water bath at 100 degrees for 5 minutes
- Positive result: Colour change from blue to orange, brick red precipitate forms
How to test for non-reducing sugars ?
- Hydrolyse non reducing sugars e.g. sucrose into their monomers by adding 1cm3 of hydrochloride acid. Heat in a boiling water bath for 5 minutes
- Neutralise the mixture using sodium carbonate solution
- Proceed with normal Benedict’s test
Negative result: Benedict’s reagent remains blue
What is the test for starch ?
- Add iodine solution
- Positive result: Colour change to Blue-Black
Draw the structure of Alpha and Beta Glucose
Both hexose monosaccharides (6C) with ring structure
Refer to GoodNotes
Draw the structure of ribose
Pentose monosaccharides (5C)
Refer to good notes
