Section 1 Flashcards
Biological molecules
What reactions make and break biological polymers?
condensation reaction releasing water
hydrolysis reaction using water
What are the three dissacharides and thier monosaccharides?
glucose + glucose = maltose
glucose + fuctose = sucrose
glucose + galactose = lactose
Draw alpha and beta glucose
What bond forms between monosacchharides?
glycosidic
Whats the test for reducing sugars?
- add benedicts reagent (blue)
- heat in a water bath to boil
- positive = green to yellow to orange to brick red ppt (gradient)
Whats the test for non reducing sugars?
- heat with HCl
- neutralise with sodium hydrogencarbonate
- heat with benedicts solution
- positive = green to yellow to orange to brick red ppt (gradient)
What is the function of starch?
Plants store excess glucose as starch which is broke down to release energy
Describe the two polysaccharides of starch
Amylose
- long, unbranched chain of A glucose
- coiled and compact for storage
Amylopectin
-long, branched chain of A glucose
-branched so can be easily hydrolysed
How does starches strucutre relate to its function?
Insoluble, doesn’t effect WP so can’t cause water to enter the cell by osmosis which would make it swell
Branched so easily hydrolysed for quick release of glucose
Coiled and compact polysaccharide of A glucose so good for storage
How does glycogens structure relate to its function?
Insoluble, doesn’t effect WP so can’t cause water to enter the cell by osmosis which would make it swell
Branched so easily hydrolysed for quick release of glucose
Coiled and compact polysaccharide of A glucose so good for storage
How does cellulose structure related to its function?
Made of long, unbranched chains of B glucose
Straight chains linked by hydrogen bonds to form strong microfibrils which provide structural support for the cell wall
Test for starch
- add iodine solution (potassium iodide - orange)
- positive = blue/ black colour
What are triglycerides made from?
One glycerol molecule and three fatty acid chains which are hydrophobic in a condensation reaction
What are saturated/ unsaturated fatty acids?
Saturated - no C=C (saturated with hydrogen)
Unsaturaed - C=C (unsaturated with hydrogen causing the chain to kink)
What bond forms in lipids?
ester
What are phospholipids made from?
phosphate group, glycerol and two fatty acids
How dose triglyceride structure relate to its function?
Used as energy storage molecules
Fatty acids contain lots of chemical energy (lots of energy released when broken down)
Insoluble in water so don’t effect WP
Bundle together in insoluble droplets with tails facing (hydrophobic) in and glycerol on the outside (hydrophillic)
How do phospholipids strucutre relate to its function?
They make up the bilayer of cell membranes which controls what enters and leaves the cell
Hydrophilic heads and hydrophobic tails
The center of the bilayer is hydrophobic so water soluble substances can’t pass through
Whats the test for lipids?
Shake substance with ethanol then pour into water
positive = milky white emulsion
What monomer are proteins made from?
amino acids
whats a polmer of amino acids called?
polypeptide
whats the general sturcture of an amino acid?
Whats the reaction that makes dipeptides and polypepdites and whats the bond called?
condensation
peptide
What is the primary structure of a protein?
sequence of amino acids in the polypeptide chain
what is the secondary structure of a protein?
hydrogen bonds form between amino acids folding the chain into an alpha helix or a beta pleated sheet
what is the tertairy structure of a protein?
Further folding with hydrogen bonds and ionic bonds
Disulhpide bridges when there is sulfur present
3D structure
what is the quaternary structure of a protein?
More than one polypeptide chain bonded together
Whats the test for proteins?
add sodium hydroxide
add copper sulfate solution
positive = blue to purple
How do enzyme substrate complexes speed up rate of reaction?
if two substrate molecules need to be joined the enzyme holds them close together reducing any repulsion so bonds can break more easilly
Describe the lock and key modle of enzymes
the substrate fits perfectly complimentary into the active site
Describe the induced fit modle of enzymes
the active site changes slightly to be complimntary to the substrate
How can you measure enzyme activity?
measure the amount of prodcut made
measure how fast the substrate is broke down
Whats the difference between competative and non- competative inhibitors?
Competative have a similar shape to substrate and will block active sites. Increasing substrate concentration can overcome this as a substrate is more likely to collide with an enzyme than an inhibitor
Non- competitive don’t bind to the active site but they cause a change in the shape so substrate can’t bind
Increasing substrate won’t have any affect D
How does pH affect enzyme rate?
Above and below optimum pH H+ and OH- ions found in acids and alkalis can disrupt the ionic bonds in the tertairy structure and the enzyme becomes denatured
How would you answer a question asking to describe and explain a graph?
Compare rates of reaction at the start of the graph and say why its like that using biological knowlage
look at the rest of the graph describe what happens for different lines and say why using biological knowlage
Describe an experiment to measure the rate of an enzyme controlled reaction (gas collection)
Put reactants in a boiling tube with a bung and delivery tube leading to an upsidedown measuring cylinder filled with water in a water trough
Measure the amount of gas made
Describe an experiment to measure the rate of an enzyme controlled reaction (quenching)
Start the reaction in a test tube and every 10 seconds pipette a bit out into a spotting tile with something that stops the reaction e.g neutraliser
How do you work out inital rate of reaction on a graph?
Draw a tangent at t = 0 and calculate the gradient = change in Y over change in X
What is the function of DNA?
store genetic information
Whats the function of RNA?
transfere genetic information from the DNA to the ribosomes
Draw and lable a nucleotide
What bonds form in the phosphodiester back bone and between what and what type of reaction?
phosphodiester bonds between a nucleotide of one monomer and the sugar of another
In a condensation reaction
What is the structure of DNA?
double helix with anti parralel strands and complimentary base pairings
How does the structure of RNA differ to DNA?
RNA has…
- ribose sugar instead of deoxyribose (both pentose sugars tho)
- Uracil instead of thymine
- Single strand not double
- shorter than DNA
Describe DNA replication
1) The enzyme DNA helicase breaks hydrogen bonds between bases making it unzip
2) Each strand acts as a template. Free floating nucleotides are attracted to their complimentary base pairs A + T and C + G
3) Condensation reaction join nucleotides of the new strand together with DNA polymerase froming hydrogen bonds. Each DNA has one old and one new strand (semi- conservative replication)
How does DNA polymerase work?
The active site of DNA polymerase is only complimentary to the 3’ end of the newly forming DNA so the enzyme can only add nucleotdies to the new strand at the 3’ end
So the new strand is made in a 5’ to 3’ directionand DNA polymerase moves down the template strand in a 3’ to 5’ direction
Becuase the strands are antiparallel the enzymes on the different strands (templates) move in oppostite directions
What is the experiment that provides evidence for semi conservation replication?
1) Two smaples of bacteria were grown for many generations - one in nutrient containing light nitrogen and the other heavy nitrogen. As the bacteria reproduced the took up nirogen from the nutrient to make nucleotides
2) A sample was taken from each and spun in a centrifuge. The heavy DNA settled lower than the light DNA
3) The heavy DNA bacteria were taken out and put in the light nitrogen nutrients and left to replicate and centrifuged again
4) The bacteria contained some of the old DNA (heavy) and some of the new DNA (light)
5) In the centrifuge it settled in the middle showing it contained both light and heavy
Draw and lable the structure of ATP
How does ATP release energy?
Hydrolysed by ATP hydrolase making ADP + Pi
Whats the relationship between ATP glucose and energy?
In respiration the energy released from glucose is used to make ATP
What is phosphorylation
Adding a Pi to a compound to make it more reactive
How it ATP made again?
Condensation reaction between ADP and Pi with ATP synthase
Name the 5 properties of water
Metabolite
Solvent
High latent heat
High specific heat capacity
Cohesive
Why is water polar?
slightly positive hydrogens and slighly negative oxygen
What is hydrogen bonding in water?
Weak bonds between slightly positive hydrogen and slightly negative oxygen
Explain the importance of water being a metabolite
Many metabolic reactions involve hydrolysis or condensation reactions which require/ relase water
E.g amino acids joining together to make proteins or energy being release from ATP
Explain the importance of water being a good solvent
A lot of important substances in biological reactions are ionic so polar water molecules can surround and dissolve them and transport them around the body
Explain the importance of water having high latent heat of vapourisation
Water evapourates (vapourises) when hydrogen bonds are broken so water becomes a gas this takes a lot of energy. This is useful for organisms as is provides a cooling effect without loosing too much water. When it evapourates is takes away heat energy (e.g sweat)
Explain the importance of water having high specific heat capacity
This is the energy needed to raise the temp of 1g of a substance by 1 degree C. This is useful for organisms as it buffers changes in temperatures helping them maintain a constant body temp
Explain the importance of water being cohesive
Water molecules stick together (cohere) becuase they are polar. Cohesion helps water flow so its good for transporting substances. E.g water travels up in collums in the xylem. Strong cohesion also means water has a high surface tension so insects can walk on the surface.
What is the importance/ role of iron ions?
It is in the center of polypeptide chains in haemoblobin. The Fe2+ binds to the oxygen and becomes Fe3+ until the oxygen is released
What is the importance/ role of sodium ions?
Co-transport
a molecule of glucose can be transported into a cell alongside Na+
What is the importance/ role of hydrogen ions?
pH is calculated based off the concentration of H+
enzyme controlled reactions are affected by pH
What is the importance/ role of phosphate ions?
When PO3 4- is attached to another molecule it is a phosphate group. DNA, RNA and ATP all contain phosphate groups. The bonds between phosphate groups store energy in ATP. The phosphate groups in DNA and RNA allow nucleotides to join up to form polynucleotides.
