Chapter 1 Biological Molecules Flashcards
What is a monomer?
A single molecule that makes up larger molecules called polymers.
What is a polymer?
A large molecule made up of multiple smaller molecules called monomers
Name examples of monomers
Monosaccharide; amino acids, nucleotides.
What reaction joins monomers together?
A condensation reaction.
What happens in a condensation reaction?
Two monomers are chemically bonded together, water is formed as a by-product.
What reaction takes place when biological molecules are separated?
A hydrolysis reaction.
What happens in a hydrolysis reaction?
Two monomers are separated by breaking a chemical bond. Water is used up in this reaction
What are larger complex carbohydrates made from?
Monosaccharides
What are the common monosaccharides?
Glucose, galactose and fructose
What reaction forms the bond between two monosaccharides?
A condensation reaction.
What bond forms when monosaccharides join?
A glycosidic bond.
What is a disaccharide?
A molecule made from 2 monosaccharides
How is a disaccharide formed?
A condensation reaction between 2 monosaccharides
What is maltose and what is it formed from?
A disaccharide formed from the condensation reaction between 2 glucose molecules.
What is sucrose and what is it formed from?
A disaccharide formed from the condensation reaction between a glucose and a fructose molecule.
What is lactose and what is it formed from?
A disaccharide formed from the condensation reaction between glucose and a galactose molecule.
What is an isomer?
A variation of a particular molecule. The formula stays the same, but the structure is slightly different.
What are the isomers of glucose?
Alpha (α) and beta (β) glucose.
What is the difference between alpha and beta glucose?
The OH group on carbon 1 of α-glucose is below the ring, on β-glucose it is above. ABBA - Alpha Below Beta Above.
What is a polysaccharide?
A complex carbohydrate formed from the condensation reactions of many monosaccharides.
What is glycogen and what is it made of?
A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
What is starch and what is it formed from?
A complex carbohydrate, a polysaccharide made from multiple α-glucose molecules.
What is cellulose?
A complex carbohydrate, a polysaccharide made from multiple β-glucose molecules.
What is the purpose of glycogen?
It is an insoluble store of energy in animals.
What is the purpose of starch?
It is an insoluble store of energy in plants, and an energy source for animals
What is the purpose of cellulose?
It is an insoluble structural molecule for plants, especially for their cell walls.
What is the structure of glycogen?
Heavily branched polymer of α-glucose molecules. Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.
Give 3 ways glycogen’s structure is related to its function.
- It is insoluble so it does not diffuse out of cells.
- It is compact so lots can be stored in a small space.
- It is highly branched so can be acted on simultaneously by enzymes.
What is the structure of starch?
Lightly branched polymer of α-glucose molecules. Linked at 1-4 glycosidic bonds. Branched with 1-6 glycosidic bonds.
Give 5 ways that the structure of starch is related to its function.
- It is insoluble so doesn’t affect water potential and osmosis
- It is large so doesn’t diffuse out of cell
- It is compact so lots stored in small space
- It is hydrolysed to form a-glucose so it is easily transported and used for respiration
- It is branched so more enzymes can act simultaneously.
What is the basic structure of cellulose?
Straight lengths of polymers made of β-glucose molecules. Bonded with 1,4 glycosidic bonds.
How are the monosaccharides in cellulose arranged?
Alternative β-glucose molecules are turned upside down
Give 3 ways that the structure of cellulose is related to its function.
- It is made up of B-glucose so it forms long, straight unbranched chains.
- The chains run parallel to each other and are crossed linked by hydrogen bonds which add collective strength.
- Molecules are grouped to form microfibrils which are also grouped to form fibres which provide more strength.
Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.
Cellulose molecules form hydrogen bonds with each other to make microfibrils. Microfibrils join to make macrofibrils. Macrofibrils join to make fibres. Fibres are insoluble and tough.
Give 4 examples of reducing sugars.
All monosaccharides - glucose, galactose, fructose. Also some disaccharides - e.g. lactose
What is an example of a non-reducing sugar?
Sucrose
What is Benedict’s reagent used to test for?
Reducing sugars
What is the test for reducing sugars
Add equal volumes of the sample and Benedict’s reagent, then gently heat for 5 minutes and if reducing sugar present then colour from blue through to orange
What is the test for non-reducing sugars
If the reducing sugar test presents no colour change, add more of your sample to an equal volume of HCl, then slowly add sodium hydrogen carbonate and re-test with Benedict’s reagent whilst gently heating for 5 minutes and if sugar is present then colour will turn to orange
Explain how a positive result is formed in Benedict’s test.
Reducing sugar reacts with blue Cu2+ –> to make brick-red Cu+
How can we test for starch?
Iodine solution turns from orange to blue/black if starch is present.
How can we use a colorimeter to do a quantitative Benedict’s test?
Use a colorimeter to measure the absorbance or transmission of light by a coloured solution.
The more concentrated solution is the more light is absorbed (less light transmitted).
Compare this to a data table or calibration curve (known concentrations vs. abs/trans value)
What is the role of lipids?
A source of: energy/waterproofing/insulation/protection
What are the 2 main groups of lipids?
Triglycerides and phospholipids
What are the components of a triglyceride?
1 glycerol molecule and 3 fatty acids bonded with a condensation reaction.
Give 4 ways that the structure of triglycerides are related to their properties.
- High ratio of energy storing C-H bonds so an excellent energy store.
- Low mass to energy ratio so good storage molecules
- Large and non-polar so insoluble in water meaning they will not affect osmosis in cells.
- There is a high ratio of H to O atoms so they will release water when oxidised to provide a source of water.
What reaction occurs to form a triglyceride?
A condensation reaction.
What bond is formed when a fatty acid joins to glycerol?
An ester bond.
What is an R-group?
A long chain of carbon atoms with attached hydrogen atoms.
What does monounsaturated and polyunsaturated mean?
Monounsaturated means that there is one carbon carbon double bond. Polyunsaturated means that there are many carbon-carbon double bonds.
Describe the structure of a phospholipid.
Phospholipids have a hydrophobic tail which orients itself away from water but mixes readily with fat and a hydrophilic head which interacts with water.
What will a phospholipid do if placed in water?
It will sit on the water, head down and tails up, or form a sphere with heads in the water and tails inside being protected.
Describe the steps in identifying lipids and state the positive result.
- Mix sample with ethanol
- Mix solution with water and shake
- If a white emulsion layer is formed then a lipid is present.
What is the basic structure of an amino acid?
What reaction causes two amino acids to bond together?
A condensation reaction.
What is the secondary structure of a protein?
alpha-helix + beta-pleated sheets
What is the quaternary structure of a protein?
Multiple polypeptide chains with the additional prosthetic groups.
Name the reaction that breaks down proteins.
Hydrolysis
Describe the test for proteins.
- Add equal volumes of the sample and Biuret reagent.
- Mix gently.
- If protein is present then a colour change from blue to purple will be observed.
What are prosthetic groups?
Non-protein component in a protein, e.g. iron containing haem group in haemoglobin.
What is thin layer chromatography?
A technique to separate individual components of a mixture (eg. Amino acids).
What are the two main types of proteins?
Globular, fibrous
What are catabolic reactions?
Breaking down molecules. This is a breakdancing cat.
How does an enzyme catalyse a reaction?
By lowering the activation energy.
Describe the lock and key model of enzyme action.
The shape of the active site is rigid. Only exactly complementary substrates can bind to form enzyme-substrate complexes.
What is the induced fit model?
The theory that the active site of an enzyme changes shape as the substrate binds to it. This is so that it can fit exactly to form an enzyme-substrate complex.
How does enzyme concentration affect the rate of a reaction?
The higher the enzyme concentration, the higher the rate of reaction. This is because there are more active sites available for the reaction to take place.
How does substrate concentration affect the rate of a reaction?
The higher the substrate concentration, the higher the rate of reaction. This is because more of the active sites are filled, and so the reaction occurs at a faster rate.
How does a competitive inhibitor affect the working of an enzyme?
They have a similar shape to the substrate, so compete for the active site. Bind to it, and stop the substrate binding.
How do the concentrations of substrate and competitive inhibitor affect the rate of reactions?
The greater the concentration of substrate, the less effective the competitive inhibitor is.
The greater the concentration of a competitive inhibitor, the slower the reaction.
How does a noncompetitive inhibitor affect the working of an enzyme?
A noncompetitive inhibitor binds to an area of the enzyme which is not the active site. It alters the shape of the protein and so the substrate can’t fit in the active site anymore.
How does increasing the substrate concentration affect the effect of the non-competitive inhibitor?
As they aren’t competing, the non-competitive inhibitor’s effect is not altered.
