Biological Molecules section 1 Flashcards
Five roles of lipids in living organisms
Phosolipids give membranes flexibility Provide energy and release water Insoluble in water (water proofing ) Slow conductors of heat so help retain heat under skin surface Protection of delicate organs
Major properties of lipids
Excellent source of energy
Good storage molecules
Insoluble in water
Source of water
What is a saturated fatty acid
Has no double bonds between carbon atoms so all carbon atoms are linked to the maximum possible number of hydrogen atoms ( saturated with hydrogen )
Test for starch
Place sample into a test tube
Add two drops of iodine solution and stir
If starch is present the solution will go blue/black
Example of a non reducing sugar
Sucrose
How do you test for non reducing sugars
If Benedicta test comes back negative -
Add some of the food sample to an equal volume of hydrochloride acid and gently boil in a water bath for 5 mins
Hydrochloric acid hydrolyses disaccharides present
Slowly add some sodium hydrocarbonate solution and test with pH paper
Retest the solution with Benedicts test
Will turn orange if non reducing sugar is present
Test for reducing sugars
Benedicts test-
Add some of the food to a test tube ( if not liquid grind up in water)
Add an equal volume of Benedicts reagent
Heat the mixture gently in a boiling water bath for 5 mins
If a red precipitate forms a reducing sugar is present
What is a reducing sugar
Are capable of donating electrons to reduce another chemical ( e.g glucose )
Reduction reaction
A chemical reaction involving the gain of electrons or hydrogen
Structure of triglycerides
Made up of glycerol and three fatty acids
CH2OOC — fatty acid 1. R group varies
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CH2OOC — Fatty acid 2. + 3H20.
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CH2OOC — Fatty acid 2
What is a polar molecule
Have two ends that behave differently and form a bilayer within a cell-surface membrane
Tertiary structure of a protein
Can be twisted and folded even more to give a specific 3D structure which is maintained by a number of different bonds formed based on its primary structure
Secondary structure of a protein
The linked chains of amino acids
There is a -NH ( positive)and a - C=O (negative )n group on either side of the peptide bond
Primary structure of a protein
Many amino acids join through a series of condensation reactions in polymerisation
Determina the end function of the protein
How are monomers joined in a protein
Amino acid monomers combine to form di peptide should through a condensation reaction. Peptide bonds form between carbon and nitrogen atoms
Monomers joined in a protein
Amino acids
Structure of an amino acid
R group varies between different groups
Carboxylate group ( acidic group )
Hydrogen group
Amino acid group stays the same
Test for proteins
Place a sample of solution into a test tube and add an equal volume of sodium hydroxide solution
Add a few drops of very dilute copper sulfato solution and mix
Purple colour action indicates the presence of peptide Bonds.
Remains blue if no protein
Types of Bonds found in proteins
Disulfide Bonds are strong and not easily broken
Ionic bonds are formed between carbonyl and amino groups that are not involved in forming peptide bonds
Hydrogen bonds , there numerous but are easily broken
Peptide bonds
Quaternary structure of a protein
Large proteins form a complex molecule containing a number of polypeptide chains
The original structure determines the final 3D structure
Structure of phospholipids
Made up of glycerol, two fatty acids and phosphate
Phosphate - hydrophilic head interacts with water but not with fat
Fatty acid molecules - hydrophobic tail orients itself away from water but mixes readily with fat
Unsaturated fatty acid
Double bonds between carbon atoms
Mono-unsaturated = one double between atoms
Double bond cause the molecules to bend so molecules cannot pack close together, making them liquid
Poly-unsaturated = more than one double bond between atoms
Hydrolysis reaction
Breaking of chemical bonds by the addition of water
Role of condensation + hydrolysis in regards to polymers
Condensation reaction = every time a new sub-unit is attached to the polymer ,a molecule of water is formed
The binds linking two sub-units in polymers can be broken down through the addition of water in hydrolysis
Polymer
Monomers are linked to form polymers through polymerisation
Type of bond in disaccharides
Glycosidic
Reaction to form a disaccharide
Condensation
Reaction to breakdown disaccharides
Hydrolysis
Disaccharides
Formed when monosaccharides join in pairs
Monomers of carbohydrates
Monosaccharides
Cellulose
Made up of B-glucose monosaccharides
Major component of cell wall
Chains run parallel to one another, and hydrogen bond form cross-linkages between adjacent chains
Straight unbranched chains means hydrogen bonds can form
Strong because of cross links
What is a condensation reaction
Two molecules are joined and water is produced
Monomers of : Polysaccharide Polynucleotide Polypeptide Lipid
= monosaccharides
= mononucleotides
= amino acids
= fatty acids
What is a macromolecule
Molecule made up of a large number of atoms (e.g polysaccharides)
Polymerisation
A process of polymers being formed and broken down through condensation or hydrolysis reaction
Monomers of :
Maltose
Sucrose
Lactose
Maltose = glucose, glucose Sucrose = glucose, fructose Lactose = glucose, galactose
Organic molecule
Carbon containing molecule
Glycogen
Made of a-glucose monosaccharides
Function to store energy
Short, highly branched chains as glucose needs to be released rapidly
Branches give a higher surface area so it can break down quicker
Large and compact
Starch
Made up a-glucose monosaccharides
Function to store energy
Chains can be branched or unbraced
Large so doesn’t diffuse out of cells
Compact so a large amount can be stored in a small place
Branched for means that many ends can be added on so that glucose can be released rapidly
What element are monomers based on
Carbon
Formation of an enzyme subraye complex
The enzyme acts on the substrate which fits into the depression (active site)
Enzyme structure
Globular proteins with a specific 3D structure based on a sequence of amino acids
Activation energy
Minimum amount of energy need to activate the reaction . Enzymes lower this
Lock and key model
Each key ( substrate )has a specific shape that fits and only operates only one single lock (enzyme ).
Limitations of lock and key method
The enzyme is considered to be a rigid structure however it was observed that the enzymes shape can be altered so is therefore flexible.
Induced fit model
The active site forms as the enzyme and substrate interact
When the substrate comes close the active site change shape
The enzyme is flexible and can mould itself around the substrate
As the enzyme changes shape it puts strain on the substrate which distorts bonds and lowers the activation energy needed to break the bond
How to measure the rate of reaction
Measure the time taken for the formation of products and the disappearance of substrates
Using a graph to measure the rate of reaction
Draw a tangent to a curve and calculate the gradient of the tangent
Why is the optimum temperature for humans 37 degrees
Higher temperatures would increase metabolic rate but the advantages of this are offset by the additional energy required to maintain the temperature
Effect of temperature on enzymes
A rise in temperature increases the kinetic energy of molecules so the molecules move around more rapidly and collide more. More enzyme substrate molecules are formed so the rate of reaction increases
The temperature rise also begins to the cause the hydrogen and other bonds to break so the enzyme and its active site changes shape. The substrate begins to not fit into the active site because it is denatured .
Effect of pH on enzymes
A change in pH alters the amino acids that make up the active site of the enzyme and as a result the substrate no longer can attach to the active site t=so the enzyme substrate complex cannot be formed .
Depending on how significant the change in pH it may cause the bonds maintaining the enzymes tertiary structure to break
Each enzyme has an optimum pH
Effect of enzyme concentration on enzyme
As long as there i an excess of substrate, an increase in the amount of enzyme leads to a proportionate increase in rate of reaction. As the excess substrate can be also be acted on.
If the substrate is limiting then any increase in enzyme concentration will have no effect on rate of reaction
Effect of substrate concentration on enzymes
If the concentration of enzyme is fixed and the substrate concentration is increased then the rate of reaction increases. This is cause more active sites will gradually be filled until all of them are working as fast as they can.
When there is an excess of substrate the rate of reaction levels off
Denature of enzymes
Desaturation is a permanent change and once it has occurred the enzyme does not function again. This occurs during a too high pH or temperature. The bonds in the active site are broken so the it changes shape
Competitive inhibitors
Have a molecular shape similar to that of the substrate which allows the to occupy the active site
They comete with the substrate for the active site
It’s the difference between the concentration of the inhibitor and that of the substrates
The inhibitor is not permanently bound to the active site so when it leaves another molecule can take its place
Eventually all the active sites will be filled with substrates
E.g malonate inhibits a respiratory enzyme that acts on succinate
Non-competitive inhibitors
Attach themselves to the enzyme at a binding site that is not the active site
It alters the shape of the enzyme and its active site and substrates can no longer fit so the enzyme can not function
An increase in substrate concentration does not decrease the effect of the inhibitor
Bonds in lipids
Ester bonds formed in a condensation reaction
Test for lipids
Emulsion test = ethanol is added to the sample, it is then shaken to dissolve any lipids.
Water is then added and it is shaken again
If it turns cloudy white, then a lipid is present
Where is the peptide bond found
Between the carboxyl and the amino acid group in a condensation reaction
Why are enzymes specific
Each enzyme has a specific shape because of its primary structure
With an active site that matches a particular substrate and wont fit other substrates
A specific amino acid sequence will code for the active site
