3.1 Biological molecules Flashcards
what are the 5 key molecules?
- Carbohydrates
- Proteins
- Lipids
- Nucleic acids
- Water
what is the glucose formula?
C6H12O6
what position is the hydroxide in Alpha glucose?
below the ring plane
what are the three carbohydrates that you need to know?
starch
glycogen
cellulose
what are the two types of starch
amylose
amylopectin
what is the difference between amylose and amylopectin?
amylose is unbranched.
what bond forms between saccharides (glucose)
glycosidic
what type of glucose is cellulose made of and what does i create?
Beta glucose causes hydrogen bonds to form between the unbranched chains.
what is the definition for monosaccharide
a single reducing sugar monomer
what is the definition for a disaccharide
two monosaccharides joined by a glycosidic bond
what is the defenititon for a polysaccharide
many monosaccharides joined together by glycosidic bonds
what is a glycosidic bond made from
two hydroxides
what type of reaction forms glycosidic bonds?
condensation
what type of reaction breaks down glycosidic bonds?
hydrolysis
what is the test for sugars (glucose)
benedicts test
what is the method for the benedicts test for reducing sugars.
-add benedicts solution to iquid sample
- place in water bath at 100 degrees c
take observations every 2 minutes
- positive test = colour change blue -> brick red
what is the method for the benedicts test for non reducing sugars.
- add hydrochloric acid
- incubate (100 degrees) for 2 minutes
- gradually add sodium hydrogen carbonate to sample until no more fizzing.
- check ph with litmus paper
- add benedicts reagent
- incubate
- record observations every two minutes
what are the examples of reducing sugars
galactose
glucose
fructose
maltose
whats an example of a non-reducing sugar?
sucrose
what is a reducing sugar
a sugar that can accept electrons
what does a colouromiter measure?
% absorption of light
true or false colouromiter results can be used against a concentration curve to quantify results
true
what do triglycerides consist of?
1 glycerol
3 fatty acids
what bonds form between the glycerol molecule and the fatty acid chain?
ester bonds
what functional groups make up a fatty acid chain?
carboxyl and methyl
when a chain has hydrogens on the same side of a double bond it is called a…
cis-fatty acid
when a chain has hydrogens on either side of the c=c double bond, the chain is called….
trans-fatty acid
what are the three functions of lipids?
increase buoyancy
store energy
insulation
what are phospholipids made from?
phosphate
glycerol
2 fatty acid chains
what do phospholipids form around a cell
a phospholipid bi-layer
what is the current model for the plasma membrane
fluid mosaic model
what factors effect fluidity of fluid mosaic model
cholesterol amount
temperature
fatty acid saturation (straight or bent tails)
what is the test for lipids?
emulsion test
what is the method for the emulsion test?
add ethanol, shake
add distilled water,shake
what is the positive result for the emulsion test?
milky white layer forms
** not cloudy **
what are the five functions of proteins
enzymes
structural
contractile
immunoproteins
transport
what are the two functional groups of an amino acid?
amine group
carboxyl group
what bond forms between amino acids
peptide bonds
how many variations of amino acid are there?
20
where does a peptide bond form?
(between which functional groups)
hydroxide and amine
what is the test for proteins?
buiret test
what is the method for the buirets test
add equal distilled water and sodium hydroxide solution to sample to make it alkaline.
Add copper(II) sulphate (buirets reagent is copper(II) sulphate + alkaline)
Colour change blue-> lilac/purple = positive
what is the test for starch?
iodine
what is the method for the iodine test for starch?
crush food and add distilled water
add iodine solution
positive = brown/orange -> blue black
What is the primary structure of proteins
The order of amino acids
What structure do fibrous proteins have?
Secondary structure
What are the two structures in the secondary structures of proteins?
Alpha helix
Beta pleated
What are the bonds formed in the primary structure of proteins?
Covelant peptide
What are the bonds formed in the secondary structure of proteins
Covelant peptide
Hydrogen bonds
What structure to globular proteins have
Tertiary structure
Round shape
What bonds form between tertiary structures (5)
Covelant peptide bonds
Hydrogen bonds
Hydrogen bonds between R-groups
Ionic bonds between charged R-groups
Hydrophobic bonds between non-polar R-groups
What protein structure is made of multiple polypeptide (protein) chains?
Quaternary
Globular proteins are made of two regions, hydrophobic and hydrophilic. Which one goes on the outside?
Hydrophilic
Give one example of a protein in the body with a quaternary structure
Haemoglobin
Which structures of proteins I.e primary, secondary are soluble in water?
Tertiary- globular
Quaternary
Which structures of protein, e.g primary, secondary are insoluble in water
Primary
Secondary- fibrous
What shaped proteins are enzymes
Globular - tertiary
What term means that enzymes are specific?
Enzyme specifity
What reactions breaks molecules down?
Catabolic reactions
What reactions builds molecules up?
Anabolic reactions
What reactions build molecules up?
Anabolic reactions
What enzyme breaks down hydrogen peroxide in the cell with the reaction: 2H2O2 -> 2H2O + O2
Catylase
Which enzyme breaks down starch into maltose
Amylase
What is the optimal ph for the enzyme amylase?
7
What does the optimum rate mean
Enzymes and substrate have the highest kinetic energy without denaturing and therefore the highest rate of reaction
What conditions can cause enzymes to denature?
Too high temperature
Too extreme ph
What is it called when you use a line of best fit between two points
Interpolation
What is it called when you extend the line of best fit outside of existing points
Extrapolation
How do we calculate uncertainty
Smallest value measurable / 2
How do we calculate percentage uncertainty
( Uncertainty / measured value ) x 100
Why does extreme ph denature proteins
It disrupts hydrogen bonds
What are the two hypotheses on enzyme action and what do they consist of?
Lock and key hypothesis- enzymes and substrate are rigid and fit perfectly into each other so that only 1 enzyme is complementary to 1 substrate
Induced for hypothesis- enzymes and substrate aren’t completely rigid so that the active site can move slightly called conformational changes to accommodate for the substrate
Why might the rate of reaction not increase when another factor e.g concentration increases
Limiting factor reached
What are enzymes inhibitors
Proteins that stop or reduce enzyme action
Where do competitive inhibitors attach to enzymes?
Active site
What is the site called that non- competitive inhibitors attach to?
Allosteric site
Which inhibitor blocks the active site and which changes the shape of the active site
Non-competitive changes the shape of the active site
Competitive blocks the active site
Which inhibitor can still eventually reach the same rate as normal
Competitive inhibitors
What is the negative feedback route of metabolic reactions that use inhibitors called
Inhibition systems
What are the three parts of a DNA neucleotide
Phosphate group
Deoxyribose sugar
Nitrogenous base
Name the five nitrogenous bases
Adenine
Thymine
Uracil
Guanine
Cytosine
What bonds form between nucleotides
Phosphodiester bonds between sugar and phosphate
Hydrogen bonds between nitrogenous bases
What sugar is found in RNA
Ribose
How many rings do purines have and what bases are purines
2 rings
Adenine and Guanine
What is it called when one of the strands of DNA are 180 degrees to the other?
Anti parallel strands
If 25% of bases in a strand of DNA are thymine, what percentage is guanine, and why?
25%
Complementary base pairs are always equal amounts T+A= 50% so G+C must = 50% (to total 100%) so G= 25% because G and C are equal
Why did early scientists think genetic material was stored in a protein form rather than by DNA
They thought DNA was too simple and couldn’t carry enough information because there wasn’t enough variation in bases. where as proteins are a lot more complicated so could carry more info
We use the triplet code in DNA to overcome the low variation. The code is universal and degenerate, what does this mean?
It is in every organism (universal)
Multiple combinations code for the same amino acid (degenerate)
Who came up with the double helix structure using franklins x-ray images of DNA
Watson & Crick
What is the believed model of DNA replication?
Semi-conservative replication
What is the process of semi-conservative replication
- DNA is unwound and unzipped
- Nucleotides pair up
- Condensation between deoxyribose sugar and phosphate groups
What enzymes :
unwind DNA
unzip DNA
catalyse condensation reaction between sugar and phosphate
Joins segments of the lagging strand together
DNA gyrase
DNA helicase
DNA polymerase
DNA ligase
Where does the energy for DNA polymerase come from
Breaking off extra phosphates on neucleotides
What direction does the lagging strand travel in? Why is this an issue?
3’ -> 5’
DNA polymerase can only work on the 5’ to 3’ strand because it only work in the 3’ to 5’ direction
What were the three different theories of DNA replication and what did they involve?
Conservative- 1 DNA molecule with both parent strands and 1 DNA molecule with both new strands
Semi-Conservative- 2 DNA molecules with 1 parent and 1 new strand in each
Dispersive- hybrid strands made of a mixture of parent and new strands
Who provided the evidence for the semiconservative model of replication?
Meselsohn and Stahl
What experiment did meselsohn and stahl conduct?
Used different isotopes of nitrogen to find how much of different DNA strands were made form their parent strands
What method is DNA extracted from human cheek cells?
- Swill drinking water around mouth for 30s
- Pour some of the water into a clean test tube
- Add salt, detergent solution, and protease solution.
- Invert the test tube to mix contents
- Heat gently in water bath
- Add cold ethanol down the side of the test tube AT AN ANGLE
- Leave the test tube to stand upright for five minutes, DNA will float to the top because it is insoluble in ethanol
What does ATP stand for?
Adenine Triphosphate
What enzyme is used to hydrolyse ATP?
ATP hydrolase or ATP-ase for short.
What are the benefits of ATP?
(6)
- only needs one enzyme
- releases small amounts of energy at at time (reduce waste)
- stable
- readily available
- not a lost form
- easily re- synthesised
What is the equation when ATP looses an inorganic phosphate.
ATP -> Pi + ADP
Why is the final phosphate of ATP rarely removed? And what is the molecule that remains called?
Removing the final phosphate release half the amount of energy that the other phosphates would so it isn’t as beneficial.
Adenosine is left behind
Which reactions do we gain water through and which do we loose water through?
We gain water through condensation reactions
We lose water through hydrolysis
What are the properties of water that make it so great? (6)
- it’s a good solvent
- less dense when frozen so ice floats
- high specific heat capacity
- high surface tension and cohesion
- high latent heat of vaporisation
- can act as a reactant
