Section 1: Biological Molecules Flashcards
What is a monomer?
- Small, single molecule which can be joined together to form a polymer
What is a polymer?
- Large molecule made of monomers joined together
What is a condensation reaction?
- Joins 2 molecules together
- Eliminates a water molecule
- Forms a chemical bond e.g. glycosidic bond
What is a hydrolysis reaction?
- Separates 2 molecules
- Breaks a chemical bond using water
Names some monomers and their polymers.
- Nucleotide - Polynucleotide
- Monosaccharide - Polysaccharide
- Amino acid - Polypeptide (protein)
What is a monosaccharide?
- Monomers from which larger carbohydrates are made
- E.g. glucose, fructose and galactose
How do you draw an Alpha glucose?
- The OH group is below the plane of the ring
How do you draw a Beta glucose?
- The OH group is above the plane of the ring
How are disaccharides formed and what molecules are required to make each?
- Formed by the condensation of 2 monosaccharides
- Glucose + Glucose = Maltose
- Glucose + Fructose = Sucrose
- Glucose + Galactose = Lactose
What is the structure and function of glycogen?
- Energy store in animal cells
- Polysaccharide of a-glucose with C1-C4 and C1-C6 glycosidic bonds so it is branched
What is the structure of glycogen suited to its function?
- Branched; rapidly hydrolysed to release glucose for respiration to provide energy
- Large polysaccharide molecule, can’t leave
- Insoluble in water, water potential of cell not affected
What is the structure and function of starch?
- Energy store in cells
- Polysaccharide of a-glucose, unbranched or branched
What is the structure related to its function?
- Helical, compact for storage in cells
- Large polysaccharide, can’t leave cell
- Insoluble in water, WP not affected
What is the function of cellulose?
- Provides strength and structural support to plant cell walls
What is the structure related to its function of cellulose?
- Every other beta glucose molecule is inverted in a long straight unbranched chain
- Many hydrogen bonds link parallel strands to form microfibrils
- H bonds are strong in high numbers
- Provides strength and structural support to plant cells
What are examples of reducing and non-reducing sugars?
- Reducing sugar : Monosaccharides, some disaccharides (maltose/ lactose)
- Some disaccharides - sucrose
What is the Benedict’s test for reducing sugars?
- Add Benedicts reagent to sample and heat in a boiling water bath
- Positive = green/yellow/orange/red percipitate
What is the Benedict’s test for non-reducing sugars?
- Add a few drops of dilute hydrochloric acid
- Heat in a boiling water bath
- Neutralise with sodium hydrogen carbonate
- Add Benedict’s reagent and heat again
- Non-reducing sugar present = green/yellow/ orange/ red percipitate
How do you determine glucose concentration?
- Produce a dilution series of glucose solutions of known concentrations
- Perform a Benedict’s test on each sample
- Using a colorimeter, measure the absorbance of each sample and plot a calibration curve
- Repeat with unknown sample (find absorbance) and use graph to determine glucose concentration
What is the Iodine test for starch?
- Add iodine to solution and shake/stir
- Blue-black colour = starch present
What are the 2 groups of lipids?
- Triglycerides and Phospholipids
How are triglycerides formed?
- Formed by the condensation of 1 molecule of glycerol and 3 fatty acids. Forms ester bonds
How are triglycerides formed?
- Formed by the condensation of 1 molecule of glycerol and 3 fatty acids. Forms ester bonds
What are the properties of triglycerides related to its function?
- High ratio of C-H bonds to C atoms in hydrocarbon tail so release more energy than the same mass of carbohydrates
- Insoluble in water so no effect on WP
How are Phospholipids formed?
- One of the fatty acids of a triglyceride is substituted by a phosphate- containing group
What are the properties of phospholipids related to its function?
- Phospholipids form bilayers in cell membranes allowing diffusion of non-polar
- Phosphate heads are polar/ hydrophilic so are attracted to water orient to aqueous environment
- Fatty acid tails are non-polar/ hydrophobic so are repelled by water - orient to interior of membrane
What is the emulsion test for lipids?
- Add ethanol and shake
- Add water
- Positive: milky/ white emulsion
What is the general structure of an amino acid
What is the primary structure of a protein?
- Sequence of amino acids in a polypeptide chain
What is the secondary structure of a protein?
- Hydrogen bonding between amino acids between carbonyl O and amino H of another
- Causes polypeptide chain to coil into alpha helix or fold into a beta pleated sheet
What is the tertiary structure of a protein?
- Overall 3D structure of a polypeptide held together held by interactions between amino acid side chains
- Ionic bonds/ disulfide chains/ hydrogen bonds
What is the Quaternary structure of a protein?
- Some proteins are made of 2+ polypeptide chains
- Held together by more hydrogen, ionic and disulfide chain bonds
What is the test for proteins?
- Add biuret solution: sodium hydroxide + Copper sulfate
- Protein present = purple/ lilac colour
- Detects peptide bonds
What do enzymes do?
- Lowers the activation energy of the reaction it catalyses - speed up the rate of reaction
- Enzymes are biological catalysts
What is the lock and key model?
- Active site is a fixed shape/ doesn’t change shape
- It is complementary to 1 substrate
- After a successful collision, an enzyme-substrate complex forms leading to a reaction
What is the Induced Fit Model?
- Before reaction, enzyme active site not completely complementary to substrate
- Active site shape changes as substrate binds and enzyme-substrate complex forms
- This stresses/ distorts bonds in substrate leading to a reaction
What are the Factors that affect the rate of enzyme-controlled reaction?
- Enzyme Concentration
- Substrate Concentration
- Temperature
- pH
How does increasing enzyme concentration affect the rate and when does it plateau?
- Increases the rate when enzyme conc is the LF
- More enzymes - more available active sites
- More successful E-S collisions and E-S complexes
- At a certain point Substrate conc = LF
How does increasing the substrate concentration affect the rate of a reaction and when does this plateau?
- Rate of reaction increases when substrate concentration is the LF
- More successful collisions and E-S complexes
- Enzyme conc = LF
How does increasing temperature affect the rate of reaction?
- Rate of reaction increases
- Increase in Kinetic Energy
- More successful E-S complexes
What happens when increasing temperature above optimum?
- Rate of reaction falls
- Enzymes denature, tertiary structure and active site changes shape
- Fewer E-S collisions and E-S complexes
What happens to the rate of reaction with pH above and below the optimum?
- Enzymes denature, tertiary structure and active site changes shape
- Complementary substrate can no longer binds
- Fewer E-S complexes
How do competitive inhibitors decrease the rate of reaction?
- Similar shape to substrate
- Competes for/ blocks / binds to active site so substrates can’t
- Fewer E-S complexes
- Increasing substrate conc reduces the effect of inhibitors
How do non-competitive inhibitors decrease the rate of reaction?
- Binds to site away from the active site
- Enzyme tertiary structure/ active site changes shape so substrate can’t bind
- Fewer E-S complexes
- Increasing substrate concentration has no effect
