Biological molecule Flashcards
What is a monomer?
Smaller units which can create larger molecules
What is a polymer?
A chain of monomers bonded together
Examples of monomers and their polymers
- Glucose: Starch, Cellulose, Glycogen
- Amino acid: Protein
- Nucleotide: DNA + RNA
Monomer for carbohydrates and examples
Monosaccharides:
- Fructose
- Glucose
- Galactose
Structure of a-glucose
- C6H12O6
- H-OH on carbon 1 + 4
- O before carbon 1
- Methyl group on carbon 5
Structure of B-glucose
- C6H12O6
- OH-H on carbon 1
- H-OH on carbon 4
- O before carbon 1
- Methyl group on carbon 5
Describe disaccharides and examples
- 2 monosaccharides joined by a glycosidic bond
- Formed via condensation reaction
EXAMPLES: - glucose+glucose = maltose
- glucose+galactose = lactose
- glucose+fructose = sucrose
Describe condensation reaction
Joining of 2 molecules together by removing water
Describe hydrolysis reaction
Splitting apart molecules by the addition of water
Describe polysaccharides and examples
Condensation reaction between many glucose monomers
EXAMPLES:
- Starch
- Cellulose
- Glycogen
Describe starch
- Alpha-glucose
- Store of glucose in plant cells
- Insoluble so doesn’t affect WP
AMYLOSE: - 1-4 glycosidic bond
- Unbranched helix
- Helix = compact so can fit a lot of glucose into small spaces
AMYLOPECTIN: - 1-4/1-6 glycosidic bond
- Branched molecule
- Branched = increased SA for rapid hydrolysis back to glucose
Describe glycogen
- Alpha-glucose
- 1-4/1-6 glycosidic bonds
- Store of glucose in animal cells e.g. muscle + liver cells
- Highly branched structure
- Branched = increased SA for rapid hydrolysis back to glucose
- Insoluble = won’t affect WP
Describe cellulose
- Beta-glucose
- 1-4 glycosidic bonds
- Provides structural support + strength to plant cell wall
- polymer forms long straight chains held parallel to each other with H-bonds = fibrils
- H-bonds = Collective strength so avoid bursting under pressure
- Insoluble = won’t affect WP
Describe how triglycerides are formed
- Condensation reaction 1 glycerol molecule + 3 fatty acids
- Forms 3 ester bonds + 3 water molecules
Describe a saturated fatty acid
The hydrocarbon chain has only single bonds between carbons
Describe a unsaturated fatty acid
The hydrocarbon chain has at least 1 double bond between carbons
Properties of triglycerides
1) High enerygy:mass = C-H bonds store a lot of energy
2) Metabolic water source = Can release water when oxidized which is beneficial for desert animals
3) Insoluble = Don’t affect WP as the hydrocarbon chain is hydrophobic
4) Slow heat conduction = Good for thermal insulation
5) Less dense than water = Buoyancy in aquatic animals
Structure of phospholipid
- Phosphate attached to glycerol = Hydrophilic head
- 2 fatty acid chains attached to glycerol = Hydrophobic tail
- 2 fatty acid bond via 2 condensation reactions = 2 ester bonds
Properties of phospholipids
- 2 different charged regions = polar
- Can form the phospholipid bilayer with the hydrophilic heads on the outside and hydrophobic tails on the inside = cell membrane
- Hydrophobic tails can splay outwards = waterproofing
Structure of an amino acid
. R
I
NH2 – C – COOH
I
H
- NH2 = Amine group
- COOH = Carboxyl group
- R = Variable group of 20 options
Describe how a dipeptide is formed
- Condensation reaction between the OH of carboxyl group and H of amine group of another
- H2O removed = Peptide bond
Describe primary structure
The sequence of amino acids in the polypeptide chain = polymer
Importance of primary structure
- A difference in even 1 amino acid in the sequence = bonds will form in different locations = different 3’ + 3D structure
- e.g. enzyme + carrier proteins
Describe secondary structure
- The specific sequence causes protein molecule to bend into a-helix or fold into B-pleated sheet
- H-bonds form between C=O in carboxyl group of 1 amino acid and H in the amine group of another
Describe tertiary structure
- Further folding for 2’ structure
- Forms unique 3D shape
- Held in place by H-bond/ionic/disulfide bonds
- H-bonds = Between C=O + H
- Ionic bond = Between R groups of opposing charges
- Disulphide bonds = Between S-S between R groups
Describe quaternary structure
More than 1 polypeptide chain bonded by H-bonds/ionic/disulfide bonds
Describe denaturing of proteins
- Bonds which hold the 2’/3’ break = 3’ 3D structure is lost
- Caused by increased heat = too much KE
- Caused by increase/decreased pH = too many OH-/H+
Biochemical test for starch
- Add iodine to sample
- Positive = blue/black
Biochemical test for reducing sugar
- Add benedict’s reagent + heat
- Positive test = green-yellow-orange-brick red
- The higher the concentration = more red
Biochemical test for non-reducing sugar
- Negative benedict’s = stays blue
- Add HCl + boil
- Cool sample then add sodium carbonate = neutralize = broken glycosidic bonds
- Add benedict’s reagent + heat
- Positive test = green-yellow-orange-brick red
Biochemical test for proteins
- Add biuret to sample
- Positive test = from blue to purple
Biochemical test for lipids
- Dissolve in ethanol
- Add distilled water
- Positive test = white emulsion
Describe an enzyme
- Tertiary structure proteins = catalyze reactions
- When attached with substrate = lower AE needed for reaction to occur = speeds up
Describe the active site
- Where the substrate attaches to the enzyme
- Specific shape = folding/bonding in 3’
- Specificity = only complementary substrate can bind
Describe the lock and key model
- Enzyme = lock / Substrate = key
- Enzyme active site is a rigid + fixed shape
- Enzyme-substrate complexes form due to random collisions
- This puts strains on the substrate bonds = lowered activation energy
Describe the induced fit model
- Shape of active site is not initially complementary but flexible
- The active site is induced and shape changes to model around the substrate
- Moulding = strain on bonds = lower AE
How does temperature affect enzymes
TOO LOW:
- Not enough KE for successful collisions between enzyme + substrate
TOO HIGH:
- Enzyme denatures = active site shape changes = can’t form enzyme-substrate complex
How does pH affect enzymes
- Enzyme denatures = fewer enzyme-substrate complexes form
- Enzymes must be optimum pH
TOO HIGH: - Too many OH- interfere with charges on aminos in active site = breaks bonds holding 3’ = shape changes
TOO LOW: - Too many H+ interfere with charges on aminos in active site = breaks bonds holding 3’ = shape changes
How does concentrations affect enzymes
INSUFFICIENT SUBSTRATE:
- Reaction will be slower as there will be collisions = empty active sights = line plateau
INSUFFICIENT ENZYME:
- Active sites will become saturated with substrate = unable to work faster as all active sites are in use = line plateau
