Topic 1 - Biological Molecules Flashcards
Give the structure of a DNA nucleotide
Phosphate + Penrose sugar + nitrogenous base
How are polynucleotides formed?
What type of reaction is this?
Many nucleotides join up in a condensation reaction.
Phosphodiester bond forms between deoxyribose sugar and phosphate group.
What does the chain of phosphates and sugars make ?
The Sugar-phosphate backbone
What type of bond forms between one Pentose sugar and a phosphate group?
Ester bond
What is the structure of DNA ?
- Polymer forms Double helix
-Long chain of nucleotides
What are the four types of nitrogenous bases?
-Adenine
-Thymine
-Cytosine
-Guanine
What bond joins two DNA polynucleotide strands?
Hydrogen bonds between the bases
What is complementary base pairing ?
Each base only join with a specific partner.
A with T
C with G
How many hydrogen bonds form between
A and T
C and G
2 between A and T
3 between C and G
Why are the polynucleotide strands antiparallel ?
They run in opposite directions to form a double helix
Give four ways in which the structure of DNA and RNA is different ?
-DNA has deoxyribose but RNA has ribose
- DNA has thymine but RNA has uracil
-DNA have a double polynucleotide strand but RNA forms a single polynucleotide strand.
- DNA is long but RNA is shorter strands
Why does DNA replicate before division ?
So that each new cell has the full amount of DNA
What is the meaning of semi-conservative replication?
-Half of the strands in each new DNA molecule are from the original DNA molecule.
What is the role of DNA helicase ?
-Enzyme which breaks the hydrogen bonds between bases on the two polynucleotide strands.
How does complementary base pairing work ?
-Free floating DNA nucleotides are attracted to their complementary exposed bases on each template strand.
What type of reaction joins the nucleotides of the new strand together?
Condensation reaction
What is the role of DNA Polymerase
-Joins the nucleotides by a condensation reaction.
-Hydrogen bonds form between the strands.
What is the structure of ATP ?
Adenine + Ribose sugar + 3 phosphate groups
What are the products of the hydrolysis of ATP ?
ADP and Phosphate group (+energy)
What type of bond is broken in hydrolysis of ATP ?
Phosphate bond
What enzyme catalyses the breakdown of ATP ?
ATP hydrolase
Why is a water a polar molecule ?
- shared electrons pulled towards oxygen
- oxygen atom is slightly negative
- hydrogen atom has slightly positive charge
- Creates a polar molecule
What type of bond forms between slightly positive H and slight negatively charge in another molecule ?
Hydrogen bonds
Why is water a good solvent ?
- Water is polar ( one negatively charged end and one positively charged end)
-So slightly positive changed end is attracted to slightly negative end.
-Ions get totally surrounded by water molecules so they dissolve.
What does high latent heat of vaporisation mean ?
Lots of heat is required to change it from a liquid to gas.
Why is high latent heat of vaporisation a useful property of water ? And how does it work
-Takes a lot of heat energy to break hydrogen bonds between water molecules.
-So it has a high latent of vaporisation a lot of energy is used up when water evaporates.
-This is useful because it cools down organisms as because water loss through evaporation helps them to cool down ( eg humans sweat )
Why is a buffer a good property of water ?
-Hydrogen bonds between molecules absorb lots of energy.
-water has a high specific heat capacity.
-water doesn’t experience rapid temperature changes so helps to maintain a constant internal body temperature.
Why is the meaning of water molecules being cohesive ?
Water molecules stick together because they’re polar.
Why is cohesion a good property of water ?
-attraction of molecules of the same type. This is because they are polar
-Helps water to flow for transporting substances.Water travels in column up xylem for examples.
-Water also has high surface tension so forms sweat droplets which evaporate and allow organism to cool down.
What is the role of iron ions in haemoglobin ?
Large protein carries oxygen
Binds to oxygen in haemoglobin
What is the role of hydrogen ions ?
- More H+ ions present lower the pH
- movement of molecules across membranes
What is the role of sodium ions ?
Co- transport of glucose and amino acids.
What is the role of phosphate ions ?
Attached to another molecule as a phosphate group.
Bonds between phosphate groups store energy in ATP.
Suggest how glycogen acts as a source of energy? (2)
Glycogen is hydrolysed to glucose
Glucose is used in respiration
Explain the shape of a graph with increased substrate concentration and rate of reaction with no inhibitor?
Increases because more enzyme-substrate complexes formed
Levels of because all all enzymes involved in enzyme- substrate complexes.
Explain why the maximum initial rate of reaction with a competitive inhibitor is higher than with a non competitive inhibitor?
(4)
Competitive inhibitor binds to active site of enzyme but non competitive binds to allosteric site (away from active site )
Competitive inhibitor does not change shape of active site but non competitive does.
With competitive inhibitor, at high substrate conc enzyme still available but with non competitive inhibitor enzyme no longer available.
At high substrate conc enzyme substrate collisions increases with competitive inhibitor but not possible with non competitive inhibitor.
Describe how bacteria divide?
(4)
Binary fission
Replication of circular DNA
Division of cytoplasm to produce 2 daughter cells
Each with single copy of DNA
Explain why protease enzyme does not work as well at high temperatures? (4)
Enzyme is denatured
Denaturation is faster at higher temp due to more kinetic energy
Breaks hydrogen bonds between amino acids
Change in shape of active site (no longer complimentary) so fewer enzyme substrate complexes formed.
Suggest one advantage to a bacterium of secreting an extra cellular protease in its natural environment? (2)
To digest proteins
So they can absorb amino acids for growth
Describe the action of membrane bound dipeptidases and explain their importance? (2)
Hydrolyse to release amino acids
Amino acids can pass through the cell membrane
Give examples of monomers and their polymers ?
Monomer Polymer:
Glucose. Starch, cellulose, glycogen
Amino acids. Protein
Nucleotide DNA and RNA
Describe a condensation reaction ?
Joining of two molecules creating a chemical bond and removing a water molecule.
Describe a hydrolysis reaction ?
Breaks a chemical bond between two molecules and involves the use of a water molecule.
Describe how a disaccharide is formed and give examples.
Two monosaccharides are joined together in condensation reaction.
This forms a glycosidic bond
Glucose + glucose > maltose
glucose + galactose > lactose
glucose + fructose > sucrose
Structure and function of starch?
Starch:
Structure-
Monomer - alpha glucose
1,4 bonds in amylose ( unbranched) and 1,4 and 1,6 bonds in amylopectin ( branched ).
Related to function:
Compact to fit a lot of glucose in a small place.
Branched structure increases surface are for hydrolysis to glucose.
Insoluble so doesn’t affect water potential.
Structure and function of cellulose ?
Monomer: beta glucose
1,4 glycosidic bonds
Related to function:
Long straight chains held parallel by hydrogen bonds to form fibrils.
Many hydrogen bonds provide strength.
Insoluble so doesn’t affect water potential.
Structure and function of glycogen ?
Monomer- alpha glucose
1,4 and 1,6 glycosidic bonds
Related to function:
Branched so large surface area for hydrolysis to glucose
Insoluble so doesn’t affect water potential
Structure of triglycerides and functions?
Structure : condensation reaction between one molecule of glycerol and three molecules of fatty acid.Forms ester bond.
Large ratio of carbon hydrogen bonds to carbon make it good for energy storage.
Large and hydrophobic means they are insoluble so don’t affect w.p
Low mass so lots of energy can be stored without increasing mass.
High ratio of hydrogen to oxygen acts as metabolic water source.e.g for camels in desert
Structure and function of phospholipids ?
One glycerol, two fatty acid and one phosphate group.
Condensation reaction forms two ester bonds between glycerol and fatty acids.
Mainly used in bilayer of cell membrane
Heads are hydrophilic and tails are hydrophobic so form a double layer.
Centre of bilayer is hydrophobic so water soluble products cannot pass through.
Describe the structure of proteins ?
Proteins are made of long chains of amino acids (monomer)
Primary structure: sequence of amino acid in the polypeptide chain.
Secondary structure: hydrogen bonds form to produce a alpha helix or beta pleated sheet.
Tertiary structure: folding of secondary structure to 3D shape held by ionic, hydrogen and disulphide bonds.
Quaternary structure: protein made up of more than one polypeptide chain.
Non competitive inhibitor action?
-Bind to allosteric site
-Causes active site to change shape so substrate molecules can no longer bind
-No enzyme substrate complex is formed so decreases rate of reaction
( increasing substrate concentration to reaction rate )
Competitive inhibitors action?
Similar shape to the substrate
Binds to the active site on enzyme so substrate can no longer bind
Prevents enzyme substrate complex from forming so decreases the rate of reaction/ catalysing of reaction
( increasing concentration of substrate will increase the rate of reaction up to a point )
Test for starch
Add potassium iodide solution.
A positive test is indicated by a colour change from browny-orange to blue- black
Test for reducing sugars?
Add Benedict’s reagent and heat in water bath that has been boiled.
A positive test solution turns from blue to green, yellow orange or brick red
Test for non-reducing sugars?
Following a negative Benedict’s test wheere reagent remains blue
Add acid and boil
Cool the solution, then add alkali to neutralise
Add Benedict’s reagent and heat
A positive test solution turns from blue to orange or brick red
Test for proteins ?
Add sodium hydroxide solution
Add copper sulfate (II) solution
Positive test results a means solution turns from blue to purple
Test for lipids ?
Dissolve sample in ethanol
Add distilled water
A positive result, cloudy white emulsion forms
RNA nucleotide
Nucleotide formed of the ribose sugar, nitrogenous, base and phosphate group.
Nitrogenous bases-adenine, guanine, cytosine, and uracil
Function of RNA ?
Transfer genetic information from DNA in the nucleus to ribosomes. Some RNA (rRNA )is also combined with protein to create ribosomes.
Semiconservative replication description ?
-DNA helicase breaks hydrogen bonds between complementary base pairs between two strands within double helix.
Each DNA strand acts as a template
Free floating DNA nucleotides attracted to complementary base pairs on template strand.
Adjacent nucleotides are joined together by condensation reaction and form phophodiester bond.
DNA polymerase catalysed the joining of adjacent nucleotides.
Two sets of daughter DNA contains one strand of parental DNA and one newly synthesised strand.
Structure of ATP ?
Adenine , ribose sugar and 3 phosphate groups.
Immediate source of energy
How is ATP made ?
During respiration from ADP and Pi by condensation reaction using enzyme ATP synthase.
How is ATP hydrolysed ?
Releases energy and is hydrolysed into ADP and Pi by ATP hydrolase.
Properties of water ? (5)
Acts as a metabolite
An important solvent in chemical reactions
High heat capacity so act as a temperature buffer
Large, latent heat of vaporisation, providing a cooling effect with loss of water through evaporation
Strong cohesion between water molecules so supports water columns and provide surface tension
Functions of proteins and how they are specialised?
Enzymes- usually spherical in shape.Soluble and have role in metabolism in both breaking down large food molecules and synthesising large molecules.
Antibodies- immune response and made of two light and two heavy polypeptide chains bonded together.Antibodies have variable regions the amino acid sequence in these regions vary greatly.
Transport protein- channel proteins contains hydrophilic and hydrophobic amino acids, which causes the protein to fold up and form channels to transport ions across membranes.
Structural proteins- strong and consist of long polypeptide chains lying parallel to each other with cross links.e.g keratin and collagen.
Why is metabolite an important property of water?
Many metabolic reactions involve condensation or hydrolysis
E.g amino acids joined to make polypeptides by condensation reaction.Energy from ATP is released through hydrolysis reaction.
Use of ATP?
Breaking of bonds between inorganic phosphate group in hydrolysis, energy is released.
Can also transfer energy to other compounds as phosphate group added to molecule to make it more reactive and is known as phosphorylation.
Properties of ATP as immediate energy source?
-Releases energy in small manageable amounts as glucose releases wasted energy.
-Small and soluble so easily transported across the cell similar to glucose.
-Only one bond is hydrolysed so energy release is immediate but glucose needs several bonds to be broken.
-Transfer energy to other molecules by phosphorylation but glucose cannot do this.
-ATP cannot pass out of cell, so always immediate source of energy but glucose can pass through.
