Topic 1A: Biological Molecules Flashcards
What is a polymer?
Large, complex molecules composed of long chains of monomers joined together by a glycosidic bond.
What is a monomer?
A small, basic molecular unit that can form a polymer.
What is a condensation reaction?
Forming a polymer by removing a H₂0 molecule to join two monomers by a glycosidic bond.
What is a hydrolysis reaction?
Breaking down a polymer by adding a H₂0 molecule to break the glycosidic bond between two monomers.
What are monosaccharides?
The monomers that make up carbohydrates.
What are the 3 monosaccharides?
Glucose
Fructose
Galactose
What is the structure of glucose?
A hexose sugar made from carbon, hydrogen and oxygen atoms.
What are carbohydrates?
Organic molecules made up of carbon, hydrogen and oxygen which are used to provide energy in respiration.
How are disaccharides formed?
Two monosaccharides are joined together through a condensation reaction which forms a glycosidic bond.
What are the 3 disaccharides?
Sucrose
Maltose
Lactose
What is maltose made of?
Two alpha glucose molecules.
What is sucrose made of?
A glucose molecule and a fructose molecule.
What is lactose made of?
A glucose molecule and a galactose molecule.
What is the process of benedict’s test for reducing sugars?
1) Add Benedict’s reagent to a sample and heat in a boiling water bath.
2) If an orange precipitate forms, a reducing sugar is present.
What is the process of benedict’s test for non-reducing sugars?
1) Add Benedict’s reagent to a sample and heat in a boiling water bath.
2) If the sample remains blue, get a new sample and add hydrochloric acid to it before heating in the boiling water bath.
3) Then neutralise the sample by adding hydrogen-carbonate.
4) Then add Benedict’s reagent to it and heat again.
5) If an orange precipitate forms, a non- reducing sugar is present.
How are polysaccharides formed?
When two or more monosaccharides are joined together by condensation reactions which produces glycosidic bonds.
What are the 3 polysaccharides?
Starch
Glycogen
Cellulose
What is the structure of starch?
A mixture of amylose (a long unbranched chain of α-glucose) and amylopectin (a long branched chain of α- glucose).
What is the function of starch?
Stores energy in plants.
What are the adaptations of starch?
Insoluble:
Has no affect on water potential making it good for storage.
Compact:
Can store lots of energy in a small space.
Can be hydrolysed:
It can easily be broken down meaning glucose can be quickly released.
What is the structure of glycogen?
Made from long highly branched chains of α-glucose.
What is the function of glycogen?
Stores energy in animals.
What are the adaptations of glycogen?
Highly branched:
Can be hydrolysed very quickly meaning energy can quickly be released.
Compact:
Can store lots of energy in a small space.
What is the structure of cellulose?
Made of long unbranched chains of β-glucose which are linked together by hydrogen bonds to form microfibrils.
What is the function of cellulose?
To provide structure to plant cells.
What are the adaptations of cellulose?
Strong microfibrils:
Provides structural support to cells.
What is the process of the iodine test for starch?
1) Add iodine dissolved in potassium iodide solution to a sample.
2) If the sample turns black, starch is present.
What are lipids made from?
Hydrocarbons
What are hydrocarbons?
Molecules which contain only hydrogen and carbon atoms.
What are the two types of lipid?
Triglycerides and phospholipids.
What is the structure of triglycerides?
They have one molecule of glycerol with three fatty acid tails attached to it by Ester bonds. These tails are hydrophobic meaning lipids are insoluble in water.
What is the structure of saturated fatty acids?
They have no double bonds between carbon atoms, meaning they are straight. They are found in animals and solid.
What is the structure of unsaturated fatty acids?
They have double bonds between carbon atoms, meaning they are kinked. They are found in plants and are able to slide over each other so are runny.
How are triglycerides formed?
Condensation reactions occur between the fatty acids and glycerol molecule, to form ester bonds.
What is the structure of phospholipids?
They have one molecule of glycerol with two fatty acids and a phosphate group attached to it by Ester bonds.
What are the adaptations of triglycerides?
Long hydrocarbon tails:
Can store lots of energy which is released when they are broken down.
Bundle together as insoluble droplets:
Has no affect on water potential making it good for storage.
How do triglycerides bundle together?
Their fatty acid tails are hydrophobic so face inwards to shield themselves from water with their glycerol heads.
What is the process for the emulsion test for lipids?
1) Add ethanol to a sample and shake.
2) Then, add water to the sample.
3) If the sample turns milky, a lipid is present.
What is the structure of a protein?
A polypeptide made of a long chain of amino acids held together by peptide bonds formed in condensation reaction.
What is the structure of an amino acid?
They are made of an amino acid, variable group, carbonyl group and hydrogen atom which are all attached to a carbon atom.
How are dipeptides and polypeptides formed?
Amino acids are joined together by peptide bonds formed in condensation reactions to form dipeptides and polypeptides.
What is the primary structure of proteins?
The sequence of amino acids in a polypeptide chain.
What is the secondary structure of proteins?
The shape of a polypeptide chain produced by hydrogen bonds which form between amino acids to produce β pleated sheets and α helix.
What is the tertiary structure of proteins?
The overall 3D structure of a polypeptide chain produced by hydrogen and ionic bonds and disulphides bridges.
What is the quaternary structure of proteins?
When several polypeptide chains join together affecting the overall shape of a protein.
How are disulfide bridges formed?
When two cysteine molecules come close together and sulfur atoms within them bond together.
What is the process for the biuret test for proteins?
1) Add hydroxide solution to the sample to make it alkaline.
2) Then add copper sulphate solution.
3) If the solution turns purple, a protein is present.
What are enzymes?
Proteins which act as biological catalysts to increase the rate of reactions.
What is an active site?
The part of an enzyme which substrate molecules bind to.
How do enzymes speed up the rate of reactions?
Substrates fit into the active site, forming enzyme-substrate complexes which:
1) Reduces the repulsion between molecules meaning they can bond more easily.
2) Puts strain on bonds meaning they can be broken down more easily. This lowers the activation energy of the reaction.
What is activation energy?
The specific amount of energy which is needed for a reaction to begin.
Enzyme action: Lock and key hypothesis
The active site is rigid and the substrate is complementary to it meaning the substrate fits perfectly without being induced to change shape.
Enzyme action: Induced fit hypothesis
The substrate and active site do not fit perfectly so the substrate induces the active site to change shape making them complementary.
How does temperature affect enzyme activity?
If you increase the temperature, the molecules have more energy meaning collisions between substrates and enzymes are more likely to occur, forming more enzyme substrate complexes. Therefore, the rate of reaction increases. If the temperature is too high, bonds in the enzyme break, causing the enzyme to denature. Therefore, the active site changes shape and the substrate will no longer fit, meaning the reaction stops.
How does pH affect enzyme activity?
If the pH is too low, there are lots of H⁺ ions which are attracted to the OH⁻ ions in the amino acids. This pulls them out of shape, denaturing the enzyme, meaning enzyme substrate complexes can no longer be formed. If the pH is too high, there are lots of OH⁻ ions which are attracted to the H⁺ ions in the amino acids. This pulls them out of shape, denaturing the enzyme, meaning enzyme substrate complexes can no longer be formed.
How does substrate concentration affect enzyme activity?
As you increase substrate concentration, more active sites get used up and become full. Therefore there are less active sites available and so the rate of reaction begins to plateau.
What are competitive inhibitors?
Have similar shape to substrate molecules so compete for active site, sitting there meaning the substrate cannot fit. Therefore it prevents ES complexes from being formed, reducing the rate.
What are non-competitive inhibitors?
Bind to the enzyme, away from the active site causing the active site to change shape. Therefore the substrate cannot fit reducing the rate of reaction. The inhibitor fits in any enzyme even if the substrate is present meaning a reaction will never reach its V-max.
What is the simple structure of alpha glucose?
What is the simple structure of beta glucose?
