biological molecules Flashcards
Three monosaccharides
-Glucose (C6H12O6)
-Galactose
-Fructose
Three disaccharides
Maltose
Lactose
Fructose
Three polysaccharides
Starch
Glycogen
Cellulose
Monosaccharides
-Simple sugars
Names end in ose
General formula =Cn (H2O ) n
Monosaccharides together form a disaccharide
-Condensation reaction form timers called disaccharides
_Disaccharides link together to form polysaccharides
- bonds formed between two monosaccharides to form a disaccharide is a1,4 glycosidic bond
Linked polymers
-polymers are made by linking many monomers together
-2 monomers link to form a dimer
-3 monomers link to form a trimer
Condensation reaction
-when two biological monomers join together water is produced
( think about how when two stones join together they push the water in between them out)
- water is produced
Hydrolysis reaction
Biological molecules can be separated into monomers by adding water to break the bond
Requires a catalyst, within the lab we can use acid or alkali as a catalyst (normally an enzyme)
What do we need to do when bonding monosaccharides
Need to take out water H2O due to a condensation reaction
Bond together after water has been taken out with an O
What makes maltose
Glucose + glucose
What makes sucrose
Glucose + fructose
What makes lactose
Glucose + galactose
Reducing sugars
Classed as simple sugars
They include all monosaccharides and most disaccharides
(Lactose and maltose)
Non reducing sugar
In sucrose the ring form of glucose and fructose cannot become linear so there is no free aldehyde group to react
Therefore cannot be oxidised and sucrose is described as a non reducing sugar
Carbohydrates , starch
-Polysaccharide
-Plant storage in the from
-seeds and storage organs (potatoes)
- component of food
- major source of energy
-energy store
What is starch made from
-chains of alpha glucose
- monomers are linked with glycosidic bonds during condensation reaction
-chains can be branched or unbranched
Starch
Structure relating to function
Insoluble =doesn’t draw water into cells by osmosis
Therefore the water potential of the cell is not effected
Large and insoluble so can’t diffuse out of the cell
Compact=large amount stored in a small space
Easily hydrolysed =glucose readily transported and available for use in respiration
Branching gives many ends = more sights for enzyme action
Never found in animal cells.
Glycogen
Found in animals and bacteria, never plants
Called animal starch =carbohydrate storage
-small granules in liver and muscles
-stored in small amounts - fat main storage molecule
-similar to Starch - shorter chains but more branched
Readily hydrolysed to alpha glucose
Glycogen- structure related to function
Insoluble =doesnt draw water into the cells by osmosis
Therefore the water potential of the cell is not effected
-large and insoluble so can’t diffuse out of cell
-compact large amounts stored in small spaces
-More branches than starch so has more ends
This speeds up enzyme action so is more rapidly hydrolysed to glucose monomers which are used in respiration
Animals therefore have a higher metabolic rate than plants
Cellulose
Structural polysaccharide in plants
-beta glucose monomers held together by 1,4 glycosidic bonds
Huge difference in structure compared to starch and glycogen
-forms straight and unbranched chains
Cellulose
Structure related to function
-straight chains run parallel with hydrogen bonds forming cross linkages between them
-each hydrogen is weak but the huge number of them strengthens the molecule
-this makes cellulose a valuable structural material
-every second glucose molecule is rotated through 180 degrees
-this produces a linear chain
-the cellulose molecules group to form microfibrils
-microfibrilis arrange in parallel groups to form fibres
- major component of cell walls
-stops cell lysis due to osmosis
-exerts inward pressure that stops water influx
-allows stem to be semi-rigid
-allows maximum area for photosynthesis.
4 main lipids
-triglycerides
-phospholipids
-cholesterol
-steroids
function of lipids
- substrate for respiration
- source of energy
- insulation ( slow conductors of heat and electrical insulators in the myelin sheath)
- protection of organs
- buoyancy and streamlining in aquatic animals
6.cell membranes ( waxy cuticle in plants and insects) - hormones ( steroids e.g oestrogen , testosterone)
- waterproofing ( waxy cuticle in plants and insects oil secretion from bebaceous glands)
hydrophilic
molecules/ groups are polar or charged and can mix/ dissolve in water
hydrophobic
molecules/groups are not polar or charged and so not dissolved in or mix with water
saturated
means a hydrocarbon chain with no c=c double bonds
unsaturated
means a hydrocarbon chain that contains one or more c=c bond
lipids
- contains carbon, hydrogen, oxygen
-insoluble in water
-soluble in organic solvents ( alcohol/ acetone)
whats the difference between fats and oils
-fats are solid at room temp
- oils are liquid
triglycerides
-Fats and oils
- formed from a glycerol ( a troil) - this always stays the same.
-3 fatty acids - these can change
-glycerol is joined to fatty acids by an ester bond.
ester bond
- formed when a carboxylic acid group (COOH) reacts with a hydroxyl group (-OH)
-within a triglyceride 3 fatty acids have reacted with 3 -OH groups.
Unsaturated
-double bonds cause molecule to bend
-they cannot pack as tightly together
-this makes them liquid at room temperature
Triglyceride structure to function
High ratio of energy storing C-H bonds to C atoms
Excellent energy store
Low mass:energy
Good energy store -large amounts stored in a small space
Large,no polar insoluble
Insoluble -won’t effect osmosis
Won’t effect water potential
High hydrogen : oxygen atoms
Release water when oxidised - desert animals
(Remember letter R represent variable group)
What’s a colorimeter
-device used for measuring colours or colorimetric
-it measures the absorbency of different wavelengths of light in a solution
-it can be used to measure the concentration of a known solute
What’s the test for lipids
-Emulation test
-If lipid is present and its a positive result - white opaque suspension
-if lipid isn’t present and its a negative result- colourless
Why does it form a white opaque suspension
Lipids dissolve in ethanol forming an emulsion
Structure of a phospholipid
-similar to triglycerides because they both contain a glycerol linked by an ester bonds to a hydrophobic fatty acid
-phospholipids differ from triglycerides in that instead of three fatty acids they have two
-the third is replaced by a polar (hydrophilic) phosphate containing group
-this gives phospholipid molecules :
-a hydrophillic head
-a hydrophobic tail
Hydrophilic head
-interacts with water
-but not with fat
Hydrophobic tails
-orients itself away from water
-mixes readily with fat
Micelles
-in solutions phospholipids form spherical structures called micelles
-hydrophobic tails pointing inwards and hydrophilic heads on the outside
-they can also forma monolayer on the water surface
Phospholipid bilayer
-phospholipids are a major component of cell membranes in which they form a bilayer
-hydrophobic tails on the inside and hydrophilic heads facing outwards
Are enzymes proteins
-enzymes are proteins
-all enzymes are proteins not all proteins are enzymes
Amino acids
The monomers that form the polymers called polypeptides
Polypeptides
-polypeptides join together to form protein
-there are 20 amino acids that occur naturally in proteins
- the fact that the same 20 amino acids occur in every living organism is proof for evolution
Protein structure
Monomer =amino acids
Polymer = polypeptide
2 monomers = dipeptide
3monomers = tripeptide
Bonds that link is a peptide bond
Amino acid structure
All amino acids include 5 different parts :
-central carbon atom
-amino group (-NH2) basic
-carboxyl group (-COOH) acid
-hydrogen atom (-H)
-R (side) group
Formation of peptide bonds
-similar to monosaccharides to disaccharides
-amino acid monomers join and form a dipeptide
-this is also a condensation reaction H2O is removed
Function of protein
-structure e.g collagen and keratin
-enzymes e.g amylase
-some hormones e.g insulin
-membrane transport
-antibodies
- ass transport e.g haemoglobin
-receptors
-cell recognition
Amino acids dissolve in water- they have different charges at both ends
Protein structure
- primary structure
-secondary structure
-tertiary structure
-quaternary structure
Protein structure
Primary structure
-the sequence of amino acids in the polypeptide chain form the primary structure of the protein
Protein structure
Secondary structure
-the sequence of amino acids causes parts of the protein molecule to bend into alpha -helix shapes or folded into B pleated sheets
-the linked amino acids that make up a polypeptide each have -NH and -C=O groups on either side of the bond
-the H of the -NH group has a positive charge
-the o of the -c=o has a negative charge
These two groups therefore easily form a weak hydrogen bond
-this causes the long peptide chain to twist into a 3D structure
Protein structure
Tertiary structure
-the a-helix of the secondary protein structure can be twisted and folded even more
-this forms a complex and often unique 3D structure known as the tertiary structure
This structure is maintained by a number of bonds including :
-disulfide bonds =strong
-ionic bonds =between carboxyl and amino groups not involved in the forming of the peptide bonds
Weaker than disulfide and easily broken by Ph changes
Hydrogen bonds-lots of them and easily broken
-it’s the 3D shape of the protein that controls its function
-the shape allows protein to recognise and be recognisable to other molecules
Protein structure
Quaternary structure
Large protein can form complex molecules consisting of many individual peptide chains
Summary of protein structure -bond in each structure
-primary =peptide bond
-secondary structure =hydrogen bond
-tertiary structure =disulfide, ionic bonds, hydrogen bonds
-quaternary structure=more than one polypeptide chain
Overall protein structure
The overall 3D structure of a protein can be classified as globular or fibrous
Fibrous protein
-form long chains parallel to each other
-chains link by cross bridges
-form very stable molecules
E.g collagen ,structural
Globular protein
-compact
-roughly spherical
-water soluble
-e.g haemoglobin, enzymes
Reaction coordinate and energy graph
Reactants = CO2 + H2O
With enzyme = activation energy is lower
Without enzyme =activation energy is higher
Induced fit model
-active site changes shape as the substrate bind at the same time causing a change in shape of the substrate
-this results in a tight fit where the active site is now complementary to the altered substrate
-the change in substrate shape induces strain in the substrate bonds which lowers the activation energy required for the reaction to occur by lowering the amount of energy needed to break bonds In the substrate
Advantages of the induced fit model
-explains how the enzyme substrate complex lowers the activation energy
-explains how products are released because active site is complimentary to transition state not products
-flexibility of active site explains how an enzyme may act on two two similar but non identical substrates
-flexibility of protein also provides better explanation of non competitive inhibition
Factors effecting the rates of an enzyme controlled reaction
-enzyme concentration
-substrate concentration
-ph
-temperature
How would you measure the rate of an enzyme catalyst reaction
-normally measured by measuring the enzyme reaction time course
-the events must be frequently measured for accurate data
-this can be done by :
-measuring products
The consumption of a substrate
Temperature
-if the temp is increased to far hydrogen bonds and other and other weak bonds will break down
-to begin with the substrate will fit , but less easily slowing the reaction down
-if the temp continues to rise the active site will loose its shape and the enzyme will denature
Denaturation is permanent
(More /less enzyme substrate complex formed )
In humans 40-45 is the absolute limit
Optimum temperature differs depending on three enzyme
Most enzymes in the human body have an optimum of 40
Ph
pH =hydrogen ion concentration
-altering ph causes a change in the charges on amino acids that form the active site
-this means that the substrate can no longer attach to the active site
-enzyme substrate complex not possible
-changing the ph can break the bonds involved in the enzymes tertiary structure
-this causes a change in the shape of the active site
-the substrate can no longer fit ans the enzyme is denatured
The rate of reaction is at its max (V Max) when all available active sites are occupied at one time
