Biological Molecules Flashcards
What makes water a polar molecule? (structure)
- One oxygen Atom (O) join with two Hydrogen atoms (H2) by shared electrons.
- Shared hydrogen electrons are pulled towards the oxygen atom meaning the other side of each hydrogen atom is left with a slight positive charge.
- The unshared negative electrons on the oxygen atom give it a slight negative charge.
- This makes water a polar molecule.
Properties of Water (5)
- High specific heat capacity.
- High latent hear of evaporation.
- Cohesive.
- Good solvent.
- Less dense when solid.
High specific heat capacity
- Hydrogen bonds between water molecules can absorb a lot of energy.
- Meaning it takes a lot of energy too heat up (high specific heat capacity).
- Means water doesn’t experience rapid temperature changes, making it a good habitat.
High Latent Heat Of Evaporation.
- It takes a lot of energy (heat) to break the hydrogen bonds between water molecules.
- This means a lot of energy is used up when water evaporates.
- Means water is a good coolant. (This is why some mammals sweat).
Cohesive
- Water is very cohesive (meaning they stick together) because they’re polar.
- Makes it easier for water to flow.
- Means water is good for transporting substances and helps water transport up plant stems in the transpiration stream.
Good Solvent
- Water’s polarity will mean ions dissolve in water.
- Important ions can dissolve in the water in blood and then be transported around the body.
Less dense when solid.
- Water molecules are held further apart in ice (less dense).
- Therefore, ice floats.
- Means ice forms an insulating layer on top of water in cold temperatures.
- This means water below doesn’t freeze so organism that live in water like fish don’t freeze and can still move around.
What is a Monomer?
Monomers are small units which are the components of larger molecules. E.g monosaccharides such as glucose and Amino Acids.
What is a Polymer?
Polymers are molecules made from monomers joined together. E.G Amino Acids join together form a polypeptide chain.
A condensation reaction
A condensation reaction is a reaction which joins monomers by chemical bonds and it involves the loss of a water molecule.
What are the 3 Main carbohydrates?
- Monosaccharides (sugar).
- Disaccharid (sugar).
- Polysaccharides
Carbohydrate def
- Contains only oxygen carbon and Hydrogen.
- Stores energy in plants and animals.
- Cellulose cell wall dependant on structural role of some carbohydrates.
Glucose+Glucose=
Maltose
Glucose+Fructose=
Sucrose
Glucose+Galactose=
Lactose
Disaccharides def
- Molecule consisting of 2 monosaccharides joined by a glyosidic bonds by a condensation reaction.
Monosaccharides def
- A molecule consisting of a single sugar.
Polysaccharide def
- A polymer made from many sugar monomers (monosaccharides).
What is a Monomer
- Single Molecule.
How is cellulose adapted to their function in plant cells?
- Long Chains which are Linked to form fibrils. This Provide strength to cell wall.
Starch function
- Main energy storage in plants.
- Mixture of two polysaccharides, Amylose and Amylopectin.
Starch adaptations.
- Amylose,Compact so it’s good for storage because you can fit more into a small space.
- Amylopectin,Branches allow enzymes that break down the molecule to reach the glycolic bonds easily.
Glycogen.
- Main energy storage material in animals.
Glycogen adaptations
- Many side branches means stored glucose can be released easily.
- Compact molecule which is good for storage.
Cellulose
- The major component of cell walls in plants.
Triglyceride structure.
- one molecule of glycerol and three fatty acids (tails) attached to it.
- Tails are hydrophobic.
- Contain ester bonds. (Broken in hydrolysis reactions)
Esterification.
- The process by which triglycerides are synthesised.
Difference between Saturated and Unsaturated fatty acids.
- Saturated=No double bonds between carbon atoms.
- Unsaturated=At least one double bond between carbon atoms. (Causes the chain to kink)
Similarity and difference between a phospholipid and triglyceride.
Similarity= They are both macromolecules. Difference= One of the fatty acids(hydrophobic) in a phospholipid is replaced by a phosphate group (hydrophilic).
Triglyceride properties.
- Long hydrocarbon tails of the fatty acids contain lot of chemical energy, means a load of energy is released when broken down.
- Insoluble, Don’t cause water to enter the cell by osmosis, which would make them swell.
Phospholipid proporties
- Hydrophilic heads and hydrophobic tails, meaning they form a double layer with their heads facing out towards the water.
- Centre of the Bilayer is hydrophobic so the membrane acts as a barrier to water soluble substances.
Cholesterol properties.
- Small size and flattened shape, allows it to fit between the phospholipid’s in the membrane.
- They bind to phospholipids tails, causing them to pack more close together,making the membrane more rigid.
What are the three ‘main’ lipids?
- Cholesterol.
- Phospholipids.
- Triglycerides.
What are the monomers in a protein?
-Amino Acids.
What is a dipeptide?
When two Amino Acids join together.
What is a polypeptide?
When more than two amino acids join together.
Amino Acid structure.
- A Carboxyl group (-COOH) and an amine group(-NH2) attached to a carbon atom.
What is the difference between the structure of Amino Acids?
- The variable group they contain.
What bond join up Amino Acids and how is it broken/formed.
- Peptide bond.
- Formed by a condensation reaction, molecule of water released.
- Broken by a hydrolysis reaction, molecule of water added.
What are the 4 protein structural levels?
- Primary structure.
- Secondary structure.
- Tertiary Structure.
- Quaternary structure.
What is the Primary structure?
- The sequence or amino acids in a polypeptide chain.
What is the secondary structure?
- Hydrogen bonds form between the amino acids in the chain.
- This makes it coil into an alpha helix or fold into a beta pleated sheet.
What is the tertiary structure of a protein?
- Coiled chain of Amino acids is coiled and folded further.
- More bonds form between different parts of polypeptide chain.
- Final 3D structure for protein made from 1 polypeptide chain.
What is the quaternary structure of proteins?
- The way polypeptide chains are assembled together. e.g Haemoglobin.
- Final 3D structure for protein made from more than 1 polypeptide chain.
Primary structure bonds.
- Peptide bonds between Amino Acids.
Secondary structure bonds .
- Hydrogen bonds.
Tertiary structure bonds
- Ionic bonds (Attraction between negatively and positively charged R groups)
- Disulphide bonds.
- Hydrogen bonds.
Quaternary structure bonds.
- Determined by the tertiary structure of the individual polypeptide chains being bonded together.
- Therefore, can be influenced by all the bonds.
Globular protein
- Round and compact.
- Hydrophilic R groups on the Amino Acids tend to be pushed on the outside of the molecule, this makes globular proteins soluble, so they’re easily transported in organisms.
Examples of globular proteins
- Haemoglobin.(Carries oxygen around the body in red blood cells).
- Insulin.(Helps regulate blood glucose levels).
- Amylase. (Catalyses the breakdown of starch in the digestive system).
Fibrous protein.
- Tough and rope-shaped.
- Insoluble.
- Fairly unreactive.
Examples of fibrous proteins.
- Collagen (Found in animal connective tissues, strong molecule, minerals can bind to increase rigidity).
- Keratin.(Found in skin, nails and hair, can be flexible or hard and tough.
- Elastin (Found in connective tissues, allows tissues to turn to its original shape after is has been stretched.
What is a conjugated protein?
-A protein with a non-protein group attached.
What are inorganic ions?
- An atom that has an electric charge.
What is a ion with a positive charge called?
- Cations.
Cations.
- Calcium (ca2+).
- Sodium (Na+).
- Potassium (K+)
- Hydrogen (H+).
- Ammonium (NH4+)
What are ions with a negative charge called?
- Nitrate (NO3-)
- Hydrogencarbonate (HCO3-).
- Chloride (Cl-)
- Phosphate (PO43-)
- Hydroxide (OH-)
Biuret test for proteins
- Add a few drops of sodium hydroxide to the solution (so it becomes an alkaline).
- Add some copper surface solution.
- Protein present=purple.
- No protein= stays blue.
Iodine test for starch.
- Add iodine dissolved in potassium solution to the test sample.
- Starch present=Dark blue-black.
- No starch= stays browny-orange.
Emulsion test for lipids.
- Shake the test substance with ethanol for about a minute, then pour the solution into water.
- Lipid present=Milky.
- No lipid= Solution remains clear.
Benedicts test for reducing sugars.
- Add benidicts to a sample and heat it in a water bath.
- Reducing sugars present= Coloured precipitate, Green-Yellow-Orange-Brick red. (The higher than concentration of reducing sugar present, the further the colour change.
- No reducing sugar present= Sample stays blue.
Benedicts test for non-reducing sugars. (E.g sucrose).
- Add dilute hydrochloric acid to the sample and heat it in a water bath.
- Neutralise the solution it’s sodium hydrogen carbonate.
- Non-reducing sugar present=Coloured precipitate.
- No Non-reducing sugar present= stays blue.
What is a colorimeter?
- A device that measures the strength of a coloured solution by seeing how much light passes through it.
Chromatography
- Draw a pencil line near the bottom of a piece of chromatography paper.
- Put a concentrated spot of the mixture of the molecule on it.
- Add a small amount of prepared solvent to a beaker and dip the bottom of the paper into it.
- Cover with a lid to stop the solvent evaporating.
- When the solvents near the top, take the paper out and marker the solvent front with pencil.
- Let the paper dry out and then analyse it.
Rf values.
- Distance travelled by spot/distance travelled by solvent.
What Is the mobile phase in chromatography?
- Where the molecules can move.
What is the stationary phase in chromatography?
- Where the molecules Can’t move,
Which chemical elements make up carbohydrates?
- C,H and O
Which chemical elements make up lipids?
- C, H and O
Which chemical elements make up proteins?
- C, H, O and S
Which chemical elements make up nucleic acids?
- C,H,O,N and P
