B3 - Biological Molecules Flashcards
Maltose
Glucose + glucose
Sucrose
Glucose + Fructose
Lactos
Glucose + galactose
Glycosidic bond
Formed between two glucose molecules.
Condensation reaction
A reaction where water is formed as one of the products.
Alpha-glucose
Hydrogen above hydroxide on right side
Beta-glucose
Hydroxide above hydrogen on right side
General formula for monosaccharides
C(n)H(2n)O(n)
Monosaccharides
A single sugar unit
Disaccharide
When two monosaccharides link together.
Polysaccharide
When 2 or more monosaccharides link together.
Glycogen
Is the main storage carbohydrate in animal cells.
In mammals it is found mainly in liver and muscle cells.
Glycogen is also a polymer of alpha glucose with a branching structure similar to amylopectin.
Cellulose
Is a polymer of b glucose joined together by (1-4) glycosidic bonds.
In order to form these bonds alternate b glucose molecules are rotated 180 degrees
Starch
Is composed of long chains of alpha glucose molecules
In plant cells it is used as an energy storage molecule. Grains of starch can be observed in chloroplasts.
It is hydrolysed by amylases produced at various points along the humane gut during digestion to release maltose and glucose
Starch is not found in animal cells.
Lipids
Lipids include fats, oils and cholesterol - all composed of C, H and O
Oils are liquid at room temperature and if cooled solidify into fats.
Lipids are non-polar and are hydrophobic - insoluble in water
They are not miscible and tend to remain in droplets or globules.
Triglycerides
Fats and oils are called triglycerides
A triglyceride is composed of one molecule of glycerol joined via ester bonds to 3 molecules of fatty acid this is called esterification (an example of a condensation reaction)
Ester bonds
An alcohol group reacting with an acidic group produces an ester bonds
The triglyceride has 3 ester bonds connecting each of the -CH2 fatty acid chains
Hydrolysis breaks ester bonds and reverses the condensation reaction. This reaction occurs in the guy to allow transport across the gut membrane and into the blood.
Ester bonds equation
Triglyceride + H20 reacts with acid and lapse to form glycerol + fatty acids
Saturated fats
In saturated fats each C bonds to 4 other atoms
All the bonds between neighbouring carbon atoms are single bonds.
No more hydrogen atoms can be added
Fats are solid at room temperature and tend to contain saturated fats.
Unsaturated fats
Unsaturated fats have fewer hydrogen atoms than they might
There are one or more double bonds between carbon atoms.
A polyunsaturated chain has many unsaturated carbon atoms
Oils are liquid at room temperature and tend to contain unsaturated fats.
Phospholipids
Phospholipids are found in cell and organelle membranes.
In phospholipids one of the fatty acids is substituted by a phosphate molecule attached to choline
Cholesterol
Cholesterol is a large multi-ringed, hydrophobic structure.
Hydrophobicity allows it to fit between the fatty acid chains of the phospholipids. This is crucial to its role as a regulator of membrane fluid.
Cholesterol regulates the fluidity of the membranes by…
Blocking large lateral motions of the fatty acids
Preventing the lipids crystallising by fitting between them
ATP
Adenosine triphosphate
Is a small molecules
Water soluble
Energy is released as phosphate groups are removed
It comes from changes in chemical potential energy in the system (anhydride bonds are hydrolysed)
ADP and ATP are phosphorylated nucleotides.
Structure of ATP
2 adenine
One ribose
3 phosphate groups
ATP reactions
ATP + H20 = ADP + Pi (+30.6kJ mol^-1)
ADP + H20 = AMP + pi (+30.6kJ mol^-1)
AMP + H20 = Adenosine + Pi (+13.8kJ mol^-1)
ATP is broken down into…
ADP and inorganic phosphate, releasing the energy contained within the bond. ATPase catalyses this process. The energy is then used for ‘work’
Starch test
Use iodine to produce a dark blue-black colour from a yellow-brown colour. Works with starch dissolved in water or just by placing iodine directly on it.
Protein test
Biuret solution contains sodium hydroxide and copper sulphate. It will go from blue to a violet colour. Intensity of colour gives a rough indication of the amount of protein.
Lipids test
Ethanol test. If lipids present a white emulsion will be present on top of the mixture
Sugar test (reducing sugars)
Benedict’s test only works for reducing sugars. (E.g glucose). The colour change depends on the amount of sugar present. It will go from blue to either green, orange or red.
Sugar test (non-reducing sugars)
Boil a non reducing sugar with dilute hydrochloride acid, then warm it with Benedict’s solution. The colour will go green, orange or red depending on the amount of sugar present.
How water helps living creatures
High boiling point allowing water to be liquid at room temperature. Absorbs a lot of heat energy
Polarity means that water has a high surface tension. Essential to pond skaters who glide on water.
Water moves as one body meaning plants can suck it up
Polarity of water allows it to be a good solvent and transport minerals around the body.
Very good at maintaining temperature, means bodies wont heat up or cool down too fast.
It’s solid form is less dense than its liquid form. Allows ice to float and not kill fish.
It’s also incompressible.
What are proteins
Proteins are macromolecules that are typically 200-300 amino acids in a long chain.
Every function in living cell depends on proteins
Proteins are polypeptides (chains of amino acids)
All proteins contain carbon, hydrogen, oxygen, and nitrogen.
What is an r group
It is a range of chemical groups different in each amino acid.
Joining amino acids together
Condensation reaction (water is produced)
A peptide bond is produced.
Joining 2 will produce a dipeptide
Joining many will produce a polypeptide
Primary protein structure
Sequence chain of amino acids
Secondary protein structure
Alpha helix
Beta pleated sheet
Alpha helix
Twisted shape like a spring
Hydrogen bonds between C and O and -NH groups to stabilise
Beta pleated sheet
Hydrogen bonds in parallel chains
Tertiary protein structure
Polypeptide chains bend to produce 3 dimensional shapes.
Chemical bonds and hydrophobic reactions between R groups keep this final tertiary structure
Contains hydrogen bonds, disulphide linkages, hydrophobic interactions and a polypeptide backbone.
Quaternary structure
2 or more proteins held together
Forming a biologically active molecule
A protein may be made up of several polypeptide chains held together
Example is haemoglobin - 4 chains held together
Haemoglobin (protein structure)
Haemoglobin has a quaternary structure made up of four individual proteins (two alpha and two beta) as well as haem groups containing iron.
Globular proteins (properties)
Compact, water soluble, and usually roughly spherical in shape.
The solubility helps in processes such as chemical reactions, immunity, muscle contraction and many more.
How globular proteins are formed
They are formed when proteins fold into their tertiary structures in such a way that the hydrophobic R-groups on the amino acids are kept away from the aqueous environment. The hydrophilic R-groups are on the outside of the protein. This means that they are soluble.
Insulin (as a protein)
Insulin is a globular protein involved in the regulation of blood glucose concentration. It is transported via the bloodstream so the soluble properties of globular proteins are essential.
Hormones also have to fit into specific receptors that means they to have precise shapes.
Conjugated proteins
Conjugated proteins are proteins that contain a non-protein component Called a prosthetic group.
Haemoglobin (as a conjugated protein)
Each subunit in haemoglobin contains a prosthetic haem group.
The iron (II) ions present in the haem groups are each able to combine reversibly with an oxygen molecule. This allows haemoglobin to transport oxygen around the body.
Fibrous proteins (structure)
Fibrous proteins are formed from long, insoluble molecules. They have repetitive sequences of amino acids that leads to organised structures reflected in their roles. They make strong, long molecules which are not folded into complex three-dimensional shapes like globular proteins
Fibrous proteins (examples)
Keratin, elastin and collagen
Keratin
Keratin is a group of fibrous proteins present in hair, skin, and nails. It forms strong, inflexible and insoluble materials. Hair contains fewer bond making it more flexible than nails.
Elastin
A fibrous protein found in elastic fibres. It is present in the walls of blood vessels and in the alveoli of the lungs. They give structures flexibility to expand and return back to their original shape. It is a quaternary protein made from many stretchy molecules called tropoelastin.
Collagen
Collagen is another fibrous protein. It is a connective tissue found in skin, tendons, ligaments and the nervous system. Like rope, collagen has flexibility.
Gene
A segment off DNA that codes for a protein, which in turn codes for a trait (skin tone, eye colour), a gene is a stretch of DNA
Who discovered DNA
The structure of DNA was discovered by James Watson and Francis Crick
Structure of nucleotides
One phosphate, one Pentose sugar, one nitrogenous base
Complimentary base pairings
A pairs to T
C pairs to G
A and T has two hydrogen bonds
C and G has three hydrogen bonds
The DNA strands run anti-parallel
A and G are bigger than C and T
Semi conservative DNA replication
Where you form two identical molecules of DNA. Each new molecule of DNA is composed of one original strand and one newly formed molecule.
Semi-conservative DNA replication (process)
A DNA helicase cause two strands of DNA to separate. Meanwhile free nucleotides are attracted to their complimentary bases. One the complimentary bases are lined up, they are joined together by DNA polymerase. When all the nucleotides are joined, two identical molecules of DNA are formed.
DNA transcription
The process in which base sequences of genes are copied and transported to the site of protein synthesis. It results in a short strand of RNA called messenger (m)RNA
DNA translation
The process where mRNA leaves the nucleus and binds to a specific site on the small subunit of a ribosome. The mRNA is held in placed while it is decoded into a sequence of amino acids.
mRNA
Messenger (m)RNA is used to transport genetic information outside of the nucleus for protein synthesis
Transfer (t)RNA
Is necessary for the translation of the mRNA. It is composed of a strand of RNA folded in such a way that three bases, called the anticodon, are at one end of the molecule. This anticodon will bind to a complementary codon on mRNA following the normal base pairing rules. The tRNA molecules carry an amino acid corresponding to that codon. When the tRNA anticodons bind to complementary codons along the mRNA, the amino acids are brought together in the correct sequence.
Protein synthesis
The mRNA binds to the small subunit of the ribosome at its start codon. A tRNA with the complimentary anticodon binds to the mRNA start codon. Another tRNA with the right anticodon and carrying the corresponding amino acid then binds to the next codon on the mRNA (max 2 tRNAs). The first amino acid is transferred to the amino acid on the second tRNA by the formation of a peptide bond.
DNA helicase
An enzyme that separates the two strands of DNA, breaking the hydrogen bonds between the bases.
RNA polymerase
An enzyme that formed phophodiester bonds between the RNA nucleotides.
Ribosomal (r)RNA
Important in maintaining the structural stability of the protein synthesis sequence and plays a biochemical role in catalysing the reaction.
What bond is formed when a nucleotide is polymerised
Peptide
What bonds link adjacent nucleotides
Phosphodiester bonds
Inorganic ions (what are they)
Inorganic ions are ions from a non-organic source. They occur in solution in the cytoplasm and body fluid or organisms.
Inorganic ions (examples)
Hydrogen ions - determine the pH of substances
Iron ions - component of haemoglobin
Sodium ions - involved in co-transport of glucose and amino acids
Phosphate ions - component of DNA and ATP
Examples of disaccharides
Maltose
Sucrose
Lactos
Examples of polysaccharides
Glycogen
Cellulose
Monosaccharides bonding
Form glycosidic bonds which are formed in condensation reactions.
Reagent strips
Can be used to test for the presence of reducing sugars. With a colour coding chart, the concentration of sugar can be determined.
Groups of lipids (examples)
Triglycerides
Phospholipids
