MODULE 2: Biological Molecules !! Flashcards
Elemental components of carbohydrates:
Carbon, hydrogen, oxygen
Elemental components of lipids:
Carbon, hydrogen, oxygen
Elemental components of proteins:
Carbon, hydrogen, oxygen, nitrogen and sulphur
Elemental components of nucleic acids:
Carbon, hydrogen, oxygen, nitrogen and phosphourous
Formation of polymers:
Biological molecules are often made up of many monomers to form a long chain polymer:
monomer –condensation–> polymer
polymer –hydrolysis–> monomer
Examples of monomers and polymers in biological molecules:
Sugar as a monomer to carbohydrates, amino acids as monomers to proteins
Properties of water:
- High boiling point
- Less dense as a solid
- Cohesive-adhesive properties
Why does water have a high boiling point?
Hydrogen bonding increases the energy required to break the intermolecular forces
Why is water less dense as a solid?
Hydrogen bonds have a fixed position slightly further away than as a liquid, causing an increase in volume but the same mass (D=m/v)
Why does water have cohesive and adhesive properties?
Polarity allows molecules to be attracted to each other and other materials
How is water essential for life?
- Acts as a solvent
- Water acts as a transport medium
- Water acts as a coolant
- Water acts as a habitat
How is water acting as a solvent essential for life? (example needed)
- Polarity of water allows solutes (that are often polar) to be dissolved
- Allows water to act as a medium for chemical reactions
- Aids transport of dissolved substances in and out of cells
E.G. cystol (aqueous component of a cytoplasm) of prokaryotes and eukaryotes mainly water
How is water acting as a transport medium essential for life? (example needed)
- Cohesion and adhesion cause CAPILLARY ACTION, so water (containing dissolved substances) can rise against gravity in narrow tubes
E.G. blood in vessels of multicellular animals, transporting necessary substances (oxygen, waste products)
How is water acting as a coolant essential for life? (example needed)
- Very stable, as does not change temperature easily and is not very volatile
- Therefore, is able to maintain a stable temperature within an organism during environmental changes and in chemical reactions (large amounts of energy used/given out)
- Important to maintain internal temperatures to maintain enzyme activity (active in narrow ranges) that catalyse metabolic processes
E.G. membrane proteins (channel + carrier) for active transport, DNA polymerase and helicase in DNA replication, ATP synthase in respiration
How is water acting as a habitat essential for life? (example needed)
- Very stable, as does not change temperature easily and is not very volatile
- Therefore maintains a temperature that aquatic organisms can live in with little variation despite seasonal changes
- During colder seasons, ice forms- but due to lower density, floats to the top of aquatic environments and forms an insulating layer for the habitats below
- Surface tension also supports small insects walking/travelling on top of the water
E.G. aquatic organisms in lakes/ponds and pond skaters using surface tension
Difference between alpha and beta glucose:
Position of -OH group on carbon one (alpha on bottom, beta on top)
Properties of glucose:
Polar, small and soluble
Hexose monosaccharides:
Fructose, galactose and glucose
Pentose monosaccharides:
Ribose and deoxyribose
Formation of disaccharides/polysaccharides:
Condensation reactions that form a glycosidic bond
Glycosidic bonds:
Covalent bonds that link ring-shaped sugar molecules
Formation of maltose:
Maltose (disaccharide)
glucose + glucose
Formation of sucrose:
Sucrose (disaccharide)
glucose + fructose
Formation of lactose:
Lactose (disaccharide)
glucose + galactose
Components of starch:
Amylose and amylopectin
Properties of amylose:
Glycosidic bonds on carbons 1-4, coiled and not branched
Properties of amylopectin:
Glycosidic bonds on carbons 1-4 and alternating 1-6, uncoiled and branched
Use of starch:
Glucose storage in plants
Use of glycogen:
Glucose storage in animals and fungi
Glycogen vs amylopectin:
Glycogen has more branching, so more free ends to add or remove glucose molecules. This means that more glucose can be released to maintain the higher metabolic demands of animals
Properties of glycogen:
High glucose density, insoluble, branched
Composition of cellulose:
Beta glucose, but due to arrangement of the molecule alternating molecules have to be ‘flipped’ for condensation to occur
Formation of cellulose fibres:
1 - Cellulose molecules form hydrogen bonds with each other
2 - Forms microfibrils, which join together to form macrofibrils
3 - Macrofibrils join together to form fibres that are strong and insoluble
Difference between unsaturated and saturated fats:
Unsaturated = double bonds (C=) Saturated = no double bonds (C-C)
Triglycerides:
One glycerol and three fatty acids form one triglyceride via condensation/esterification (forms 3 water molecules too)
Phospholipids:
One phosphate (PO4 3-) head and two fatty acids. Phosphate head is polar and hydrophilic and fatty acid tails is non-polar and hydrophobic
Sterols:
- Complex alcohol molecules w/ 4 carbon ring
- Amphipathic (both hydrophobic and hydrophilic)
- Cholesterol is an example
Cholesterol role:
Maintains fluidity (in temperature change) by packing between phospholipids in plasma membrane
Phospholipid role:
Form membranes/hydrophobic barrier between cell and environment
Biological importance of lipids:
- hormone production
- electrical insulation for nerve impulses
- water-proofing (bird feathers/plant leaves)
- thermal insulation (penguins)
- protection of vital organs (kidneys and heart)
- buoyancy (whales)
Structure of an amino acid:
NH2CH(R)COOH
- may be sourced from food
- may be released in protein synthesis
Synthesis of dipeptide/polypeptide:
amino acid + amino acid –> dipeptide + water
- condensation reaction catalysed by peptidyl transferase
- peptide bond (CONH) formed
- reverse reaction, hydrolysis, catalysed by proteases
Levels of protein structure:
Primary, secondary, tertiary, quaternary
Primary proteins:
- sequence of amino acids
- ONLY peptide bonds
- amino acid sequence influence shape (folding/coiling)
Secondary proteins:
ALPHA HELIX:
caused by INTERNAL hydrogen bonding
BETA PLEATED SHEET
caused by ADJACENT hydrogen bonds
Tertiary proteins:
- 3D shape (coiling + folding)
- R-group interactions: hydrophobic-hydrophilic interactions, hydrogen bonds, ionic bonds, disulfide bridges
Quaternary proteins:
- 2+ individual proteins (subunits)
- Same as tertiary
Globular proteins:
- Tertiary
- Hydrophobic R-groups on inside of protein
- Soluble in water
E.G. insulin
Conjugated proteins:
- Same as globular, but with a prosthetic group
- Soluble in water
E.G. haemoglobin (Fe2+) and catalase (Fe2+)
Fibrous proteins:
- Primary
- Small R-groups, hydrophobic
-Insoluble, strong and organised
E.G. Keratin, elastin and collagen
List all tests for biological molecules:
- Biuret test
- Benedict’s test
- Iodine test
- Emulsion test
What does the Iodine test test for and how is it carried out?
- Starch
- Add starch to sample
- Brown = negative
- Blue-black = positive
What does the Biuret test test for and how is it carried out?
- Proteins
- Add excess NaOH to sample
- Add CuSO4 one drop at a time until the solution turns blue
- Leave to stand for 5 minutes
- Blue = negative, purple = positive
What does the Benedict’s test test for and how is it carried out?
- Reducing and non-reducing sugars
- Place aqueous sample in boiling tube
- Add equal volume of Benedict’s solution
- Heat in water bath
- Blue = negative, green/yellow/red = positive
Benedict’s test on a non-reducing sugar:
- Boil sample with hydrochloric acid
- Repeat Benedict’s test as normal
Cause of colour change in Benedict’s test:
- Copper sulfate is blue
- ‘Free electrons’ from ketone or aldehyde group on sugar are donated to Cu2+ ions
- This forms the ‘brick-red’ Cu+ ions (precipitate)
What does the Emulsion test test for and how is it carried out?
- Lipids
- Sample mixed with ethanol
- Mixed with water and shaken
- Clear = negative, white emulsion (cloudy layer) = positive
Quantitative vs qualitative:
Qualitative: No numbers involved to conclude a number (interpretation)
Quantitative: Achieving a number to conclude a result
Colourimetry:
- filter placed in colorimeter
- calibrated with distilled water
- filtered, liquid sample added to a cuvette to measure absorbance
Use of chromatography (thin layer/paper):
Separate individual components of a mixture to identify individual biological compounds, such as proteins, carbohydrates, vitamins and nucleic acids
Rf equation:
distance moved by solute/distance moved by solvent
