Biological Molecules Flashcards
Monomer is …
small, single molecule many of which can be joined together to form a polymer
Polymer is…
large molecule made up of many similar monomers joined together
A condensation reaction..
Joins 2 molecules together, eliminates a water molecules, forms a chemical bond
A hydrolysis reaction
Separates 2 molecules, requires addition of a water molecule, breaks a chemical bond
Disaccharide e.g.
glucose+glucose →maltose
glucose+fructose →sucrose
glucose+galactose →lactose
Monosaccharides are…
the monomers from which larger carbohydrates are made
What bond is formed from a condensation reaction between 2 monosaccharides
Glycosidic
Difference between alpha and beta glucose
OH group is below C1 on a-glucose, but above C1 on b-glucose
*remember ABBA (honourable mamma mia mention)
Alpha
Below
Beta
Above
Glycogen: function and structure
Energy store in animal cells
Polysaccharide of a-glucose with C1-C4 and C1-C6 glycosidic bonds so branched
Structure of glycogen related to its function
Branched; can be rapidly hydrolysed to release glucose for respiration to provide energy
Large polysaccharide molecule; cant leave the cell
Insoluble in water; water potential of cell isn’t affected
Starch: function and structure
-Energy store in plant cells
-Polysaccharide of a-glucose
-Mixture of amylose and amylopectin
-Amylose (C1-C4 glycosidic bonds)
-Amylopectin (C1-C6 glycosidic bonds) so branched
Structure of starch related to its function
Helical; compact for storage in cells
Large polysaccharide; can’t leave cell
Insoluble in water; water potential of cell not affected
Cellulose: function
Provides strength and structural support to plant cell walls
Structure of cellulose related to its function
-Every other beta glucose molecule is inverted in a long, straight, unbranched chain
-Many H bonds link parallel strands to form microfibrils
-H bonds are strong and high in number
-Providing strength and structural support to plant cell walls
Benedicts test for reducing sugars
-Add benedict’s reagent (blue) to sample
-Heat in boiling water bath
-Positive= green/yellow/orange/red (depending amount of reducing sugar conc)
Benedicts test for non reducing sugar
-Add a few drops on dilute HCl ( to hydrolyse sugar)
-Heat in a boiling water bath
-Neutralise with sodium bicarbonate
-Add Benedict’s and heat again
-Non reducing sugar present= green/yellow/orange/red (depending amount of reducing sugar conc)
Determining glucose concentration
-Produce a dilution series of glucose solutions of known concentrations
-Perform a Benedict’s test on each sample
-Use same amount for each solution
-Remove precipitate by filtering
-Using a colorimeter measure the absorbance and plot a calibration curve
-Calibrate using unreacted Benedict’s
-Use red filter
-Absorbance against glucose concentration
-Repeat with unknown samples and use graph to determine glucose concentrations
Iodine test for starch
-Add iodine dissolved in potassium iodide to solution and shake
-Blue/black colour =positive
Formation of triglycerides
Condensation of 1 glycerol and 3 fatty acids, forming an ester bond
Properties related to a triglycerides structure
-Energy storage molecule
-High ratio of C-H bonds to C atoms in hydrocarbon tail so more energy is released compared to the same mass of carbohydrates
-Insoluble in water so no effect on water. potential
Formation of phospholipids
One of the fatty acids of a triglyceride is substituted by a phosphate-containing group
Properties related to a phospholipids structure
-Form bilayer in cell membrane, allowing diffusion of non-polar, small molecules
-Phosphate heads are polar/hydrophilic
-Fatty acids tails are non-polar/hydrophobic
Emulsion test for lipids
Add ethanol and shake
Then add water
Positive; milky/cloudy white emulsion
General structure of amino acids
-amine group
-carboxyl group
-R group (variable)
-CH
Amino acids can form
-Dipeptides; 2 amino acids joined
-Polypeptide; many amino acids joined
Structure of proteins
Primary; Sequence of amino acids in a polypeptide chains
Secondary; H bonding between amino acids causes polypeptide chain to fold into a repeating pattern (a-helix or b-pleated sheets)
Tertiary; Overall 3D structure of a polypeptide held together by interactions between amino acid side chains: ionic. bonds/disulphide bridges/H bonds
Quaternary; Some proteins made of 2+ polypeptide chains held together by more H, ionic and disulfide bonds
Biuret test for proteins
-Add biuret solution; NaOH + CuSO4
-Positive= purple colour
-Detects presence of peptide bond
Lock and key model (old)
-Active site is a fixed shape and is complementary to one substrate
-After a successful collision, an E-S complex forms leading to a reaction
Induced fit model (accepted)
-Before reaction, enzyme AS isn’t completely complementary to specific substrate
-AS shape changes slightly as substrate binds and E-S complex forms
-This distorts bonds in sublate leading to a reaction
The specificity of enzymes
-Enzymes have a specific tertiary stucture and active site (determined by the sequence of amino acids in primary structure)
-AS complimentary to specific substrate
How does enzyme conc affect rate of enzyme controlled reactions
-Increasing enzyme conc., increases RoR
-More enzymes= more available active sites
-More successful E-S collisions and complexes
-Until RoR plateaus
How does substrate conc affect rate of enzyme controlled reactions
-Increasing substrate conc, increases RoR
-More successful E-S collisions and complexes
How does temperature affect rate of enzyme controlled reactions
-Increasing temp to optimum, increases RoR
-Increase in kinetic energy
-More successful E-S complexes and collisions
-Increasing temp above optimum, rate of reaction falls
-Enzymes denature; tertiary structure and active site changes shape
-Fewer E-S collisions and E-S complexes, as substrate can no longer bind
How does pH affect rate of enzyme controlled reactions
-pH above/below optimum,RoR decreases
-Enzymes denature; tertiary structure and active site changes shape
-Fewer E-S collisions and E-S complexes, as substrate can no longer bind
Competitive inhibitors
-Similar shape to substrate
-Compete to bind to AS so substrates cannot bind
-Fewer E-S complexes
-Increasing substrate conc reduces effect of inhibitor
Non- competitive inhibitor
-Binds to allosteric site
-Enzyme tertiary structure/ changes shape so substrates can’t bind to AS
-Fewer E-S complexes
Function of DNA and RNA
DNA- holds genetic information
RNA- transfers genetic info from DNA to ribosomes
-Ribosomes are formed from RNA and proteins
The differences between DNA and RNA
-DNA nucleotides have the pentose sugar deoxyribose, whereas RNA nucleotides have the pentose sugar ribose
-DNA nucleotides have the bases thymine, whereas RNA nucleotides have uracil instead
-DNA has two strands, RNA is single stranded
-DNA has H bonds, RNA doesn’t
-DNA is longer, RNA is shorter
Structure of DNA related to its function
-Double stranded; both strands can act as templates for semi-conservative replication
-Weak H bonds between bases; can be unzipped for replication
-Complementary base pairing; accurate replication
-Many H bonds between bases; stable molecule
-Double helix with sugar phosphate backbone; protects H bonds
-Long molecule; stores lots of genetic info
-Double helix; compact
Semi conservative replication
-DNA Helicase breaks H bonds between bases, unwinds double helix
-2 strands act as templates
-Free floating DNA nucleotides attract to exposed bases by specific complementary base pairing, H bonds are formed
-DNA polymerase joins adjacent nucleotides by condensation, forms phosphodiester bonds
-Replication is semi conservative- each new strands formed contains one original
-Ensuring genetic continuity between generations of cells
How does DNA polymerase move along DNA antiparallel strands
-DNA polymerase is an enzyme with a specific AS which can only bind two substrate with complementary shape
-Can only bind to the phosphate 3’ end
Evidence for semi-conservative (Meselson and Stahl)
-Bacteria is grown in a nutrient solution contain heaving Nitrogen (15N) for several generations
-Nitrogen is incorporated into bacterial DNA bases
-Bacteria is transferred to a nutrient solution containing light Nitrogen (14N) and allowed to grow and divide twice
-During this process, DNA moves from different samples of bacteria was extracted, suspended in a solution in separate tubes and spun in a centrifuge.
Structure of adenosine trisphosphate
-Ribose, a molecule of adenine, 3 phosphate groups
-Nucleotide derivative
-The structure of ADP= is the same as ATP, minus a phosphate
ATP hydrolysis
-Catalyses by ATP hydrolase
-Inorganic phosphate releases can phosphorylate other compounds often making them more reactive
ATP condensation
-Catalysed by ATP synthase
-Happens during respiration or photosynthesis
Properties of ATP
-ATP cannot be stored
-ATP releasees energy in small, manageable amounts to reduce waste
-Only one bond hydrolysed, to release energy
How does H bonding occur between water molecules
-Water is polar
-Slightly negative O atoms attract slightly positive H atoms of other water molecules
-So H bonds form
Water: High SHC explanation and importance
Polar so many H bonds between water→allow water to absorb a large amount of heat energy before its temp change
-Good habitat for aquatic organisms
-Organisms mostly made of water so helps maintains a constant internal body temp
Water: High LHE explanation and importance
Polar so many H bonds between water→allow water to absorb a lot of energy before breaking when water evaporates
-Evaporation of small amount of water is an efficient cooling mechanism
-Helping organisms maintain a constant body temp
Water: Cohesive explanation and importance
Polar so many H bonds between water→so water molecules tend to stick together
-Columns of water don’t break
-Produces surface tension at an air water. surface so invertebrates can walk on water
Water: Solvent explanation and importance
Polar so can separate ionic compounds
-Can dissolve other substance so water acts as a medium for metabolic reaction
Water:Metabolite explanation and importance
Reactive
-Involved in condensation and hydrolysis reactions
Role of phosphate ions
Attached to other molecules as a phosphate group e.g:
-DNA nucleotides, so nucleotides can join together and form phosphodiester bonds
-ATP; bonds between these store/release energy
Role of Hydrogen ions
-Maintain pH levels in the body
-Affects rate of enzyme controlled reactions
Role of Iron ions
-Component of Haem group of Haemaglobin
-Transports Oxygen around body, O2 bind stocks it temporarily and forms Fe3+
Role of Sodium ions
-Co transport of glucose and amino acids across cell membranes
-Involved in generating nerve impulses and muscle contraction
