Chapter 1: Biological molecules Flashcards
What is Molecular Biology?
The study of particular groups of biological molecules found in living organisms.
What is Covalent Bonding?
A bond between atoms share a pair of electrons in their outer shells. Forms a more stable molecule.
What is Ionic Bonding?
A bond formed between ions of opposite charge attracting one another. They are weaker than covalent bonds. (eg. Na+ and Cl- making sodium Chloride)
What is Hydrogen Bonding?
The attraction of the negative charges region of a polarised molecule to the positively charged region of another, forming a weak electrostatic bond. (Individually Weak, Collectively Strong)
Whats is a polar molecule?
A molecule with unevenly distributed charge of electrons, this causes separate positively/negatively charged regions. These molecules are said to be Polarised
What are Polymers?
Long chains of monomer sub-units
What is formed each time a monomer is added to a polymer chain?
a molecule of water/H2O
What is the formation of polymers called?
Polymerisation
What are reactions that produce water
called?
Condensation reactions
How are polymer chains broken down?
through the addition of water
What type of reaction involves the breaking down of polymers through the addition of water?
Hydrolysis
What do Polynucleotides (nucleic acids) hydrolyse to make?
Mononucleotides
What do Nucleotides make after condensation?
Polynucleotides (nucleic acids)
What do Polysaccharides (carbohydrates) hydrolyse to make?
Monosaccharides
What do Monosaccharides make after condensation?
Polysaccharides (carbohydrates)
What do fatty acids or glycerol hydrolyse to make?
Lipids
What do Lipids make after condensation?
Either fatty acids or glycerol
What do Polypeptides hydrolyse to make?
Amino acids
What do Amino acids make after condensation?
Polypeptides
What is the metabolism?
All the chemical processes in the body
What is a mole?
The SI unit for measuring the amount of a substance (abbreviated to mol)
How many particles are in one mole?
6.022x10^23
What is this number ,6.022x10^23, called?
Avagadros constant
What is a molar solution?
A solution with one mole of solute per litre of solution
What are Carbohydrates?
Carbon molecules combined with water, that range in size.
What are Organic molecules?
Carbon containing molecules
What is a significant feature of carbon atoms?
They readily form bonds with other carbon atoms, so can build up.
What is the most basic monomer unit in Carbohydrates?
A Sugar or Saccaride
What is a monosaccharide?
A single molecule of sugar ; a single saccharide molecule
What is a Disaccharide?
A Pair of Saccharides
What are Polysaccharides?
Monosaccarides combines in much larger numbers to make a chain.
What is the General formula for Monosaccarides?
(CH2O)n , n being any number from 3 to 7
Give three examples of Monosaccharides.
Glucose, Galactose and Fructose.
What are the two isomers of glucose?
α- glucose and β-glucose
What is a Reduction reaction ?
A chemical reaction involving the gain of electrons or hydrogen.
What is a Reducing sugar?
A sugar that can donate electrons to another chemical.
What is Benedict’s reagent?
an alkaline solution of copper (II) sulfate.
How do you test for reducing sugars?
The Benedict’s test
Describe Benedict’s test.
form a solution of food sample, add and equal amount of Benedict’s solution then heat in a water bath for five mins.
What colour would the Benedict’s reagent turn if a reducing sugar is present?
an orange brown colour
What two monosaccharides form the disaccharide maltose?
Glucose joined to Glucose
What two monosaccharides form the disaccharide sucrose?
Glucose joined to Fructose
What two monosaccharides form the disaccharide lactose?
Glucose joined to Galactose
What is the bond formed between two monosaccharides after a condensation reaction?
a glycosidic bond between the two OH molecules
What are non-reducing sugars?
saccharides that do not change colour of Benedict’s reagent they are heated with.
Describe the test for non-reducing sugars.
complete Benedict’s test for reducing sugars, if it remains blue continue; hydrolyse solution with hydrochloric acid in a hot water bath; neutralise solution w/ sodium hydrogencarbonate; repeat Benedict’s
Describe the test for starch.
add two drops of iodine to 2ml of solution; shake solution. If starch is present the solution would turn blue-black.
Why are polysaccharides suitable for solution?
They are very large insoluble molecules.
What is the structure of starch?
its made of chains of α-glucose, can be branched and unbranched and is wound into a tight coil that makes the molecule compact
How is the structure of starch suited to its function?
large and insoluble, so doesn’t diffuse out cells; coils make it compact for storage; hydrolysed into α-glucose for respiration; is branched so can be easily acted on by enzymes, breaking it down quickly.
Where is starch commonly found?
in plants such as potatoes, never found in animal cells.
Describe the structure of Glycogen.
shorter chains of α-glucose that are highly branched.
How does glycogen’s structure suit it’s function?
insoluble so doesn’t diffuse out cells or affect water potential; is compact; highly branched so eaisly broken down for resperation (animals have higher metabolic rate)
Where is glycogen commonly found?
in animal and bacteria cells, but never in plant cells.
How does the structure of cellulose majorly differ to glycogen and starch?
instead of α-glucose it uses β-glucose and forms straight unbranched chains
Describe the structure of the cellulose chains
they run parallel to one another allowing hydrogen bonds to form cross-linkages between adjacent chains. goruped together they form microfibrils
What is the structure of cellulose fibres?
Microfibrils are collected together and arranged in parallel groups of fibres.
What do the hydrogen bonds in cellulose do?
the large number provides collective strength.
Why is Cellulose’s structure suited to it’s function?
the straight unbranched chains; hydrogen bonds bring collective strength; grouping of microfibrils provides more strength.
What is the function of Cellulose in a plant?
to provide support and rigidity
What are common characteristics of lipids?
they contain carbon, hydrogen and oxygen in smaller proportion than carbs; insoluble in water ; soluble in organic solvents (alcohols and acetone)
What are the main groups of lipids?
Triglycerides and phospholipids
What are the roles of lipids?
- cell membranes
- source of energy (2x than carbohydrates)
- insulation (slow conductors of heat)
- waterproofing (insoluble, found on cuticle)
-protection (stored around delicate organs)
Describe the structure of Triglycerides.
three fatty acids combined with a glycerol, with three ester bonds
What is a saturated fatty acid?
a fatty acid with no double bond between carbon atoms.
What is an mono-unsaturated fatty acid?
a fatty acid with one double bond between carbon atoms
What is an poly-unsaturated fatty acid?
a fatty acid with multiple double bonds between carbon atoms
How does the structure of triglycerides suit their function?
have a high amount energy storing bonds so good source of energy; low mass to energy ratio; insoluble so doesn’t affect cell’s water potential; release water when oxidised, so important source of water
What provides variation in triglycerides?
the variation of over 70 fatty acids
Whats the structure of fatty acids?
a carboxyl group (COOH) with hydrocarbon chain attached
Describe the structure of phospholipids.
two fatty acid and a phospholipid molecule connected to a glycerol molecules.
What two parts is the phospholipid molecules split into?
a hydrophobic ‘tail’ - fatty acids
a hydrophilic ‘head’- phosphate molecule
How does the structure of phospholipids suit their function?
polar so can form a bilayer as hydrophobic tail and hydrophilic tail; can form glycolipids at cell surface membrane
How would you test a solution for lipids?
add solution and ethanol to a dry grease-free test tube. shake tube then add water. for a control test, use water as a solution.
What is the result of a lipid test if a lipid is present?
a milky-white emulsion is formed
What do polypeptide chains combine to form?
a Protein
What are the four chemical groups in amino acids?
- amino group (-NH₂)
- carboxyl group (-COOH)
- hydrogen atom (-H)
- R group
What bond is formed between two proteins?
a peptide bond between the carbon of the carboxyl group of one amino acid and the nitrogen of the amino group of the other
What is the primary structure of a protein?
the sequence of amino acids found in its polypeptide chain
Why does the primary structure of a protein affect it’s function?
the function of a protein depends on the shape, a single change in the primary structure could alter the bonds formed in the tertiary structure and thus proteins shape.
What is the secondary structure of a protein?
the polypeptide chains form weak hydrogen bonds as amino acids are polarised, this causes the chains to twist into an α-helix coil.
What is the tertiary structure of a protein?
the coiling, bonding and twisting of the α-helix polypeptide chain caused by disulphide bridges, ionic and hydrogen bonds
What is the Quaternary stricture of a protein?
the combination of a number of different polypeptide chains and associated prosthetic (non-protein) groups into large complex protein.
What is the test for protein called?
the Biuret test
Describe the test for proteins.
place solution in a test tube with an equal amount of sodium hydroxide. then add a few drops of very dilute of. copper (II) sulfate solution.
What colour would the solution turn in the Biuret test is protein is/isn’t present?
it will turn purple if peptide bonds (protein) are present, and will remain blue if not.
What are the two basic molecular types of protein?
fibrous and globular proteins
what are fibrous proteins? and give an example.
structural functions eg. collagen
what are globular proteins? and give an example.
metabolic functions eg. enzymes and haemoglobin
What are Catalysts?
chemicals that alter the rate of a chemical reaction without undergoing permanent changes to themselves.
What are enzymes?
proteins that act as catalysts
How do enzymes increase the rate of reaction?
they lower activation energy allowing reactions to take place at a lower temperature than normal
What is the active site of an enzyme?
the functional depression on the molecule where the substrate binds and is acted on
What is an enzyme-substrate complex?
the complex formed by the bonding between enzyme and substrate at the active site.
What is the induced-fit enzyme model?
the enzymes active site slightly changes shape to bind with the substrate
What factors affect the rate of enzyme controlled reaction?
Temperature, pH, substrate concentration, enzyme concentration and inhibitors
How does a lower temperature affect the rate of enzyme reactions?
lower temp means not enough kinetic energy for substrate and enzymes to successfully collide.
Why does the rate of reaction drop off when the temperature gets too high?
the enzyme denatures due to temperature
How does significant changes in pH affect enzymes?
they could denature them
What are the two types of enzyme inhibitor?
competitive and non-competitive inhibitors
What is a competitive inhibitor?
an inhibitor that competes with the substrate to occupy the active site
What is a non-competitive inhibitor?
an inhibitor that attaches to the enzyme molecule changing the enzymes shape and thus making it unable to form a substrate-enzyme complex.
