3.1- Biological Molecules Flashcards
What are biomolecules?
Groups of chemicals that are found in living organisms.
4 main types- carbohydrates, lipids, proteins, nucleic acids.
What are monomers? +3 examples
Small subunits that can be linked together to form long chains called polymers.
monosaccharides, amino acids, nucleotides
What are polymers? +3 examples
Molecules made from a large number of monomers joined together in a chain through process of polymerisation.
starch, DNA, protein
What is a condensation reaction?
Joining 2 molecules together with the formation of a chemical bond- involves the elimination (release) of a water molecule. (Giving out of water.)
What is a hydrolysis reaction?
A reaction that breaks a chemical bond between 2 molecules- involves the use of water molecule. (Taking in of water.)
What is a solvent?
A liquid that has dissolved a substance.
What is a solute?
The substance that has dissolved.
What is a solution?
Solvent+ Solute
What are carbohydrates?
Carbon molecules combined with water: made of C, H, O.
They are the sugars (saccharides.)
What are monosaccharides? +3 examples
The simplest carbohydrates, the monomers from which larger carbohydrates form.
Eg- glucose, galactose, fructose.
What does a condensation reaction between 2 monosaccharides form?
A glycosidic bond.
How is water formed in condensation reactions?
Water is formed through the grouping of a hydroxyl (-OH) from one monomer and a hydrogen (H) from another monomer.
Information about the monosaccharide glucose.
6 carbon sugar (hexose), atoms can be arranged in diff ways to produce 2 isomers- a-glucose and B-glucose.
Draw the structure of alpha and beta-glucose.
Alpha glucose has right OH group on bottom and H on top, Beta glucose has right OH group on top and H on bottom.
Why can the human body only use alpha-glucose?
Many chemical reactions in our bodies are controlled by enzymes.
Only 1 isomer of a given chemical fits the specific active site of the enzyme needed for it to react.
The reactions involving glucose are catalysed by an enzyme that only fits a-glucose in its active site.
What does the condensation of 2 monosaccharides create? +3 examples.
A disaccharide.
Eg- sucrose, maltose, lactose.
Word equation for sucrose?
+ what is it hydrolysed by?
a glucose + B fructose—-> sucrose + water
hydrolysed by sucrase
Word equation for lactose?
+ what is it hydrolysed by?
a glucose +B galactose—-> lactose + water
hydrolysed by lactase
Word equation for maltose?
+ what is it hydrolysed by?
a glucose + a glucose—-> maltose + water
hydrolysed by maltase
What are polysaccharides? + 3 examples.
Polymers formed by the condensation of many glucose units.
Eg- starch + glycogen (alpha glucose), cellulose (beta glucose.)
What is the test for reducing sugars?
Heat the liquid sample with Benedict’s reagent for 5 minutes in a boiling water bath.
A positive result would turn from blue—> red.
Why does a reducing sugar turn Benedict’s red?
It reduces copper (II) sulfate in Benedict’s to form insoluble red precipitate copper (I) oxide.
What is the test for non-reducing sugars?
If Benedict’s test remains blue:
1) The sugars need to be hydrolysed (broken down) into monosaccharides by using dilute HCl (an acid) in boiling water for 5 mins.
2) Neutralise the acid using an alkali such as sodium hydrogencarbonate as Benedict’s does not work in acidic conditions.
3) Test using Benedict’s reagent as usual- heat and if the colour changes to red then non-reducing sugars are present.
What is the test for starch?
Add a few drops of iodine solution to the sample at room temperature.
A positive result would be indicated by a colour change from yellow to blue/black (BRUISE colour.)
What is starch?
Polymer of alpha glucose
A large complex polysaccharide found in plants with main role of energy/glucose storage. Insoluble- doesn’t affect osmosis/ water potential in cells.
Quickly hydrolysed- to a-glucose used in respiration.
Naturally occurs as amylose and amylopectin.
What is the structure of starch?
Alpha glucose molecules can join by condensation reactions to make glycosidic bonds at either 1-4 or 1-6 carbon atoms.
2 types of chains made- branched + unbranched.
Amylose- Unbranched polymer chain of a-glucose joined by 1-4 glycosidic bonds: coil tightly to form helical chains so lots can be stored in small space. As it is unbranched, it will be hydrolysed slowly. Insoluble
Amylopectin- Branched polymer of a-glucose with 1-4 and 1-6 glycosidic bonds:
more ends for rapid breakdown by enzymes simultaneously releases lots of glucose quickly. Insoluble. Not as compact due to branching.
Where is amylose/ amylopectin broken down by amylase?
In the mouth- by salivary amylase (pH 6.5-7)
The duodenum in small intestine- by pancreatic amylase (pH is 7-8 due to bile salts)
What is glycogen?
Polysaccharide of a-glucose joined by glycosidic bonds formed in condensation reactions.
Storage for animals +bacteria.
More branched than amylopectin, not coiled.
Mass is not high in animals as fat is main energy storage molecule.
What is the structure of glycogen?
Highly branched chains with mix of 1-4 and 1-6 glycosidic bonds so there are more ends and enzymes can easily access+ hydrolyse glycosidic bonds to release glucose for respiration. The multiple ends allow simultaneous hydrolysis to occur.
Insoluble in water so will have no osmotic effect on the cell which could cause it to burst.
What is cellulose?
Polysaccharide made from 1-4 glycosidic bonds between beta-glucose monomers which forms long, straight, unbranched chains.
Chains held in parallel by many hydrogen bonds to form fibrils.
Found in plant cell walls.
What is the structure of cellulose?
It does not need to be broken down after it is made due to its function, so there is no branching.
Many hydrogen bonds provide collective strength for the cell wall.
Insoluble so won’t affect water potential of the cell.
Why is cellulose not broken down by animals?
They do not have cellulase
What are lipids? +2 main groups
They are biomolecules that are insoluble in water but soluble in organic solvents such as chloroform or acetone.
They are composed of fatty acids and glycerol or other alcohol backbones.
2 main groups- Triglycerides, phospholipids.
What are lipids main roles?
1) Flexibility and transfer role in plasma membrane.
2) An energy source
3) Waterproofing- insoluble in water-waxy cuticles of plants+insects.
4) Insulation- slow heat conductors
5) Protection- stored around delicate organs eg kidneys.
What are triglycerides?
Fats and oils- fats solid at room temp, oils liquid at room temp.
Called triglycerides: 3 fatty acids joined to 1 glycerol- formed by the condensation of 1 glycerol molecule and 3 fatty acid molecules. 3 water molecules removed, 3 ester bonds formed.
Structure of triglycerides?
All have same basic structure- carboxyl group (-COOH) but hydrocarbon tail (R group) varies.
The difference in properties of fats +oils come from variations in the fatty acid/tail.
Why are lipids insoluble in water?
The hydrocarbon tails are hydrophobic- they repel water molecules.
How are the properties of triglycerides related to their structure?
High ratio C-H bonds to C atoms in hydrocarbon chain so used in respiration to release a lot of energy.
Hydrophobic/non-polar fatty acids so insoluble in water so no effect on water potential of cell.
What are the 2 types of fatty acids R group?
Saturated + unsaturated.
Saturated- these do not have any double bonds between their carbon atoms.
Unsaturated- these have at least 1 double bond between their carbon atoms.
The double bond causes the chains to have a kink and the molecules to bend, they cannot pack closely together so they are liquid at RT (oils.)
1 double bond= monounsaturated, more than 1= polyunsaturated.
Compare triglycerides and phospholipids.
Both contain a glycerol molecule and fatty acids.
Triglyceride contains 3 fatty acid chains whereas phospholipid only has 2 fatty acid chains as 1 is replaced by a phosphate group
Structure of phospholipids?
Made of a glycerol molecule, 2 fatty acid chains and a phosphate group (attached to the glycerol.)
The 2 fatty acids bond to the glycerol via 2 condensation reactions, resulting in 2 ester bonds.
Properties of phospholipids?
Due to the negative charge of phosphate group, the head is hydrophilic- it can attract and interact with water.
The fatty acid chains do not have any charge so they are hydrophobic- they repel water but are able to attract and interact with lipids.
What is the emulsion test for lipids?
1) Add ethanol to sample
2) Dissolve sample by shaking vigorously
3) Add water, shake gently
4) Positive result= white/milky EMULSION
What happens when phospholipids are placed in water?
They arrange themselves in a 2 layer structure = phospholipid bilayer
This is the structure we see on membranes, cell surface membranes, or membranes on organelles in eukaryotic cells.
They are polar- due to 2 different charged regions: tails move inwards as they are repelled by water and hydrophilic heads move to the outside as they can interact with water.
What are proteins?
Polymers (and macromolecules) made of monomers called amino acids.
The sequence, type + number of the amino acids within a protein determines its shape and therefore its function.
What are proteins made of?
Large polymer biomolecules made up from amino acids (containing mostly hydrogen, carbon, nitrogen, oxygen) which are joined together by peptide bonds.
What is the test for proteins?
Add Biuret to sample.
Positive result = blue—>purple
What is general structure of amino acids?
A central carbon atom bonded to:
1) An amine group -NH2/ H2N
2) A carboxylic acid group -COOH
3) A hydrogen atom
4) An R group (how each amino acid differs + why amino acid properties differ e.g. whether they are acidic or basic or whether they are polar or non-polar.)
What is a peptide bond?
When a condensation reaction forms a bond between 2 amino acids.
Made by combining C atom of one amino acid and N atom of another atom.
How is water made in peptide bond?
Combining the -OH of carboxyl group of 1 amino acid and -H from the other amino acid.
What is a dipeptide?
The molecule formed when two amino acids react together in a condensation reaction
What is a polypeptide?
A polymer made of many amino acids joined together by peptide bonds.
What are the structural levels of proteins?
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
What is the primary structure?
The sequence of amino acids bonded by covalent peptide bonds.
DNA of cell determines primary structure of a protein by instructing the cell to add certain amino acids in specific quantities in a certain sequence- affects the shape + function of the protein.
Specific for each protein.
What is the secondary structure?
Folding of polypeptide chain to form:
α-helix: polypeptide is wound to form a helix, held by H bonds running parallel with the long helical axis. Very stable
β-pleated sheet: polypeptide chain zigzags forming a sheet of antiparallel strands.
Between NH (group of one amino acis) and C=O group, as a result of hydrogen bonding between the amino acids.
