2.1.2 Biological Molecules Flashcards
Structure and function of amylopectin
Helical shape so is compact and tightly packed.
Large insoluble molecule so does not affect water potential.
Branched with alpha 1-4 and 1-6 glycosidic bonds so glucose is easily released.
Large molecule so cannot leave cell/cross plasma membrane.
Functions of lipids in animals.
Energy source/store, has high energy value and is compact so minimises mass.
Thermal insulation, poor heat conductor, minimises heat loss from body.
Waterproofing, non-polar, hydrophobic and insoluble.
Buoyancy, loess dense than water.
Protection around organs, elastic, and forms a protective layer around organs, helps to cushion them from external forces.
How does the change to one amino acid affect the structure of a protein.
There’s a change in the amino acid sequence in the primary structure.
This causes a change in the disuflide/ionic/hydrogen bonds between R groups.
Therefore causes a change in the protein tertiary structure.
Properties of collagen
Strong hydrogen bonds between triple helix structure provides tensile strength.
Stable protein and forms connective tissue.
Insoluble in water so it provides structural support.
Making Disaccharides
Glucose + Glucose = Maltose + Water
Glucose + Fructose Sucrose = water
Glucose + Galactose = Lactose + water
Polysaccharides
Cellulose, Starch, Glycogen
Cellulose: plants structural strength, beta glucose, long straight chain, 1-4 glycosidic bonds.
Starch: plants store of energy, alpha glucose, Amylose - 1-4 glycosidic bonds - unbranched helix. Amylopectin - 1-4, 1-6 glycosidic bonds - branched.
Glycogen: animals store of glucose, alpha glucose, 1-4, 1-6 glycosidic bonds - highly branched.
Triglycerides formation
Composed of one molecule of glycerol joined via ester bonds to 3 molecules of fatty acids.
Glycerol - 3 carbon molecule with 3 -OH groups.
Hydrolysis breaks ester bonds + reverses condensation reaction.
Biosensors
Use biological components to determine the presence and conc. of molecules such as glucose.
Molecular recognition: protein or simple strand of DNA is immobilised to a surface.
Will interact with/bind to the specific molecule under investigation.
Transduction: Interaction causes a change in a transducer. Detects changes (pH) + produces a response.
Display: produces a visible qualitative/quantitative signal (release of immobilised dye on test strip).
Colorimeter
- Set filter in colorimeter
- Calibrate to 0 using distilled water
- Insert samples from biochemical test (e.g. different conc of glucose with Benedict’s solution + filter to remove precipitates)
- Measure percentage transmission of light
- Draw calibration curve using results from known conc of glucose.
Structure of ATP
Used for: muscle contraction, cell division, transmission of nerve impulses.
Synthesis, transport, movement.
3 phosphate groups
1 ribose
adenine
Not a good long term energy store - don’t store large amounts of ATP due to instability.
Properties: small - moves easily in/out of cells.
Water soluble - energy requiring processes occur in aq environments.
Contains bonds between phosphates with intermediate energy: large enough to be used for cellular reactions, not as large that energy is wasted as heat.
Easily regenerated.
Triglycerides uses
Energy storage: large ratio of energy storing carbon-hydrogen bonds.
Metabolic water source: release water if oxidised, essential for animals in desert.
Do not affect water potential: large + hydrophobic - insoluble in water.
Low mass: a lot can be stored without increasing mass + preventing movement.
Insolation: stored in adipose tissue - heat + electrical insulator - hibernating animals.
Buoyancy: less dense than water, keep aquatic animals afloat + protection of organs from damage.
Uses and properties of water
Polar: hydrogen bonds between water molecules.
Metabolite: involved in chemical reactions.
Solvent: dissolves solutes - easily transported around the body in cytoplasm + plasma.
High heat capacity: buffers temp, keeps body temp constant - aquatic organisms survive.
High latent heat of evaporation: provides cooling effect - energy transferred for evaporation.
Strong cohesion: supports water columns in plants + surface tension - habitat for insects.
Phospholipids
Modified triglycerides: non-polar fatty acid tail, polar phosphorous head.
Pi found in cytoplasm of cell - soluble in water.
Surfactants: form layer on surface of water.
Bilayer: form cell membranes - separate aq environment from aq cytosol in cell.
Cholesterol
Hydrophobic and hydrophilic regions - exist in membrane bilayer.
Changes fluidity of cell membrane - reduce fluidity at high temp and increase fluidity at low temp.
Acts as a barrier + prevents water soluble substances diffusing across membrane.
Proteins structure
Primary: sequence of amino acids connected by peptide bonds.
Secondary: first level of folding, held by hydrogen bonds. Alpha helices and/or beta pleated sheets. Found in soluble proteins - enzymes + hormones.
Tertiary: Compact structure formed by folding of a whole peptide chain. Every protein has unique tertiary structure responsible for its properties + function. lobular structure held together by bonds between R groups.
Hydrogen bonds - weak O-H
Hydrophobic + hydrophillic interactions - between non-polar R groups
Ionic bonds - strong - between R groups with positive or negative charge
Disulfide - very strong - covalent S-S bonds.
Quaternary: found in proteins containing more than one polypeptide chain - haemoglobin.
Fibrous proteins
Long rope-like shape.
Polypeptide chains form long twisted strands linked together
Stable (unreactive) structure
Form hydrogen bonds with adjacent chains
Insoluble in water
Strength gives structural function.
e.g. collagen in bone and keratin in hair.
Collagen
Forms part of skin, tendons, cartilage, ligaments, bone + connective tissue in bronchi, bronchioles + trachea.
Quaternary structure contains 3 polypeptide chains, wound around like a rope.
Chains held together by H + covalent crosslinks between the molecules.
Crosslinks are staggered for strength + chains lie close each other due to 35% of its amino acids being glycine.
Collagen is flexible but not stretchy.
Keratin
Used to form skin, nails + hair - all protect the body.
Important it’s insoluble so these structures are not broken down by water in the environment.
Elastin
Common fibrous protein, makes up elastic fibres around alveoli + blood vessels.
Allows these structures to stretch + recoil to their original shape + size.
Globular Proteins
Spherical shape
Polypeptide chains ‘roll up’ into spherical shape
Relatively unstable structure
Have hydrophobic R groups on the inside and hydrophilic R groups on the outside
Soluble
Metabolic functions
e.g. all enzymes, antibodies, some hormones (e.g. insulin), haemoglobin.
Haemoglobin
Globular protein responsible for transport of oxygen.
4 polypeptide chains (2 alpha + 2 beta) each bind to one molecule of oxygen doe to its prosthetic haem group.
Pepsin
Enzyme found in the stomach.
A protease enzyme, able to digest other proteins using its specifically shaped active site which is complimentary to its substrate.
Insulin
Globular protein + hormone produced in beta ells in pancreas to lower blood glucose conc.
Specific 3D shape is complementary to receptors on the cell surface membrane of its target cells (hepatic + muscle cells)
Chromatography
Investigations into separation of proteins, carbs, vitamins, or nucleic acids can be conducted using TLC or paper chromatography.
Stationary phase (silica covered plate or paper -does not move)
Mobile phase (solvent - does move)
Conc sample of biological molecule placed 1cm from end of the stationary phase.
Stationary phase placed in a beaker with less than 1cm depth of solvent.
As solvent moves up, has an affinity for the biological molecules + dissolves them, carrying them up the stationary phase.
