1 - Biological Molecules Flashcards
What is the function of H+ ions
- maintains pH levels in body
- movement of molecules across cell membranes
- forms ATP in respiration & photosynthesis
What is the definition of metabolism?
The sum of all reactions that occur in an organism
Where are inorganic ions found?
in solution in the cytoplasm and body fluids of organisms
What is the function of Fe 2+ (iron) Ions?
- component of haemoglobin
- transports o2 around the whole body (o2 binds to it)
What is the function of PO4 3- (phosphate) Ions?
components of:
- nucleic acids (DNA/RNA)
- ATP
- phospholipids in cell membrane
What is the function of Na+ (sodium) Ions?
Co - transport of glucose and amino acids
What are the thermal properties of water
HIGH SPECIFIC HEAT CAPACITY:
- buffers changes in temperature
LARGE LATENT HEAT OF VAPORISATION:
- provides a cooling effect through evaporation
- Good habitat for aquatic organisms as temperature more stable than land
- Organisms mostly made of water so helps maintain a constant internal body temperature – important as temperature affects enzyme activity
What are the cohesive properties of water?
Cohesion: so supports columns of water in plants
- produces surface tension supporting organisms eg pond skaters on water
Describe property of water: solvent
- metabolic reactions can occur
- allows transport of substances
Describe a condensation reaction
- Joins 2 molecules together
- releases water
- Forms a chemical bond e.g. glycosidic bond
Describe a hydrolysis reaction
- Separates 2 molecules
- uses water
- Breaks a chemical bond
Describe anabolism
- small to big
- uses condensation reactions
Describe catabolism
- big to small
- uses hydrolysis reactions
What are monosaccharides and disaccharides?
Simple carbohydrates
What is maltose made up from?
Glucose + glucose
What is sucrose made up from?
Glucose + fructose
What is lactose made up from?
Glucose + galactose
How does a glycosidic bond form?
By a condensation reaction between two monosaccharides
Where is the OH in alpha glucose?
Below carbon 1
Where is the OH in beta glucose?
Above carbon 1
What are examples of polysaccharides?
Starch
Cellulose
Glycogen
What is the structure & function of glycogen?
F: glucose so provides respiratory substrate for energy release
S:
- polysaccharide of alpha glucose with (1,4) and (1,6) glycosidic bonds
- helical/ coiled/ branched so more ends for faster hydrolysis
- insoluble in water so does not affect water potential
What’s the function of starch?
Energy store in plant cells
- helical = compact for storage in cell
- insoluble in water
- can’t leave cell
What’s the structure of starch?
Mixture of amylose and amylopectin
What’s the structure of amylose starch?
- (1,4) glycosidic bonds
- unbranched/linear
What’s the structure of amylopectin starch?
- (1,4) & (1,6) glycosidic bonds
- branched
What’s the function of cellulose? 6m
- provides strength & structural support to plant cell walls:
- unbranched/linear
- long and straight chains
- beta glucose
- has crosslinks to form strong fibres
- Lots of strong H bonds (strong in large numbers & hold chains together)
How are triglycerides formed?
By the Condensation of 1 molecule of glycerol and 3 fatty acids, and the removal of 3 molecules of water. Ester bond is formed.
What forms an ester bond?
A condensation reaction between glycerol and fatty acid
What are the functions of triglycerides?
- Effective energy stores - have a large number of hydrocarbon chains so rich in energy
- Insoluble in water so can be stored without affecting the cells water potential 
What is the structure of Phospholipids?
One of the fatty acids of the triglyceride is substituted by a phosphate containing group.
What do phospholipids form and why?
A bilayer in cell membrane allowing diffusion of small molecules due to its Phosphate heads and fatty acid tails
What are phosphate heads in phospholipids?
Polar/hydrophilic = attracted to/ interact with water
So face outwards
What are fatty acid tails in phospholipids?
Non-polar/hydrophobic = repelled by water
So face inwards
What’s the test for starch?
Iodine in potassium iodide solution turns blue/black
Compare and contrast triglycerides & phospholipids (7m)
- both contain ester bonds
- triglyceride has 3 fatty acids , phospholipids have 2 + a phosphate group
- both contain glycerol
- phospholipids form bilayer but triglycerides don’t
- fatty acids on both may be saturated or unsaturated
- both contain C, H, O but phospholipids also contain P
What are enzyme cofactors?
Enable enzyme controlled reactions to take place e.g. Coenzymes
Explain how the active site of an enzyme causes a high rate of reaction/ explain the induced fit model
- lowers activation energy
- induced fit causes active site to change shape
- so enzyme substrate complex cause bonds to form/break
What is the role of a competitive inhibitor?
has a similar shape to the substrate so it binds to the active site & prevents enzyme substrate complexes forming
- (increasing substrate conc reduces effect on inhibitor)
What overcomes inhibition in a enzyme?
Increased substrate concentration
- there is a greater probability of the substrate successfully colliding
What is the role of a non-competitive inhibitor?
Binds to a different part of the enzyme (not active site) and changes shape of the active site so active site and substrate no longer complementary so no substrate can fit
OR
- Irreversibly denatures the enzyme (so increasing substrate conc has no effect on ROR)
What is the effect of a non-competitive inhibitor?
Lowers the amount of enzymes that can do the reaction so rate of reaction decreases
What are the factors affecting the rate of enzyme controlled reactions?
- Enzyme concentration
- substrate concentration
- pH level
- temperature
How does enzyme concentration affect the rate of reaction?
increased rate of reaction as long as there is increased substrate concentration
- higher vmax can be achieved
How does substrate concentration affect the rate of reaction?
Increasing substrate concentration increases rate of reaction INITIALLY
- Eventually the rate of reaction will tail off as Vmax is achieved (all active sites are occupied and enzyme cannot work any faster)
How does pH affect the rate of reaction?
- affects ionic bonds
- Highest rate of reaction is at optimum pH of enzyme
- Extreme pH values denature enzyme permanently
How does temperature affect the rate of reaction?
Higher temperature = higher rate of reaction (more kinetic energy so more collisions) until the optimum
- above the optimum temperature hydrogen/ionic bonds in tertiary structure start to break
What is secondary protein structure made of?
hydrogen bonding between amino acids - between the NH group of one and the C=O of another
Causing polypeptide chain to fold into Beta pleated sheets and alpha helixes
Describe tertiary protein structure
formed by interactions between R groups - H bonds, ionic bonds & disulphide bridges
- gives things their specific 3D shape
What are the roles of hydrogen bonds in protein?
can form in multiple places and help stabilise the structure
Describe ionic interactions in a protein
- Some amino acids have either a positive or negative charge
- These charges attract the opposite charge & cause folding
Describe disulphide bonds/bridges?
Covalent bonds that can only form between cysteine amino acids as they contain sulfur
Describe quaternary protein structure
- multiple polypeptide chains linked together formed by interactions between different polypeptides
What are the roles of ATP?
Immediate source of energy:
- releases energy in small manageable amounts so no energy is wasted
- only one bond is hydrolysed (single reaction) to release energy fast
Describe the structure of ATP
Nucleotide derivative
- 1 molecule of adenine
- ribose
- 3 phosphate groups
CANNOT BE STORED
Describe the structure of ADP?
The same as ATP minus one phosphate
Describe ATP hydrolysis
(ATP —> ADP + Pi)
- Catalysed by the enzyme ATP hydrolase
- to provide energy for other reactions
-  to add phosphate to other substances and make them more reactive
Describe ATP condensation /synthesis
(ADP + Pi —> ATP)
- Catalysed by the same enzyme ATP synthase
- happens during respiration or photosynthesis
How many hydrogen bonds do G and C form (in dna)
3
How many hydrogen bonds do A and T form? (In dna)
2
What are nucleotides made up of
- a phosphate group
- a sugar (deoxyribose/ribose)
- a nitrogenous base (A/T/C/G)
How are phosphodiester bonds formed?
Condensation between phosphate and deoxyribose
3) Describe the Role of DNA polymerase in semi conservative dna replication
- DNA polymerase synthesises new strands from the two parental template strands
- free nucleotides form hydrogen bonds with their complementary base partner (C to G, A to T)
- DNA polymerase joins adjacent nucleotides by condensation forming phosphodiester bonds
- sugar phosphate backbone forms
1) Describe the Role of DNA helicase in semi conservative dna replication
- DNA helicase unwinds the double helix and unzips the two polynucleotide strands
- hydrogen bonds between complementary base pairs break
2) What is a replication fork?
the 2 separated DNA strands act as templates for the synthesis of new complementary strands
How are all dipeptides similar and different?
Similar:
- amine group at the end
- COOH group at the end
Different: different R groups
How is a peptide bond formed between two amino acids to form a dipeptide?
Condensation reaction between amine and carboxyl
What is the structure of DNA (5m)
- polymer of nucleotides
- each nucleotide formed by deoxyribose, a phosphate group and nitrogenous base
- Phosphodiester bonds between nucleotides
- Double helix held by H bonds
- H bonds between adenine, thymine, guanine and cytosine
What is the protein associated with DNA in a chromosome?
Histone
Name the two scientists who proposed models of the chemical structure of DNA replication?
Watson and crick
Give two features of DNA and explain how each one is important in semiconservative application
1) Weak hydrogen bonds between bases allow two strands to unzip
2) Two strands, so both can act as templates
What’s the test for reducing sugars?
Benedict’s test - turns brick red
What’s the test for lipids
- add ethanol to the sample and shake
- add water
- if it turns to milky emulsion it has lipids
What’s the test for proteins?
Biuret turns purple
What is a monomer
A smaller molecule from which larger molecules are made of
Describe how monomers join to form the primary structure of a protein
- condensation reaction
- to form a peptide bond between amino acids
- primary structure is a sequence of amino acids
Describe property of water: metabolite
A metabolite in condensation/hydrolysis
Explain how differences in the primary structure of haemoglobin can provide evidence of phylogenetic relationships between species (5m)
- mutations change base sequence
- causing change in amino acid sequence
- mutations build up over time
- there are more mutations between distantly related species
- closely related species have a recent common ancestor
Describe primary protein structure
The sequence of amino acids joined by peptide bonds in a polypeptide chain
The overall structure is determined by the relative position of R groups
How is the tertiary structure of a protein changed eg by pH
Ionic/Hydrogen bonds are broken
What is the purpose of DNA replication?
Insures genetic continuity between generations of cells
How does DNA polymerase move in opposite directions along a DNA strand?
- dna has antiparallel strands
- dna polymerase has a specific shaped active site which can only bind and add nucleotides to the phosphate (3’) end of the developing strand.
- it goes from 3’ to 5’ in opposite directions for each strand
Why is the model of DNA replication where the first strand doesn’t unwind or split unsupported
Because there should be two peaks in generation one
Why is the model of DNA replication where the first strand splits into loads of little bits unsupported
Because:
- there should be more than 2 peaks in generation 2/3
- there should be one wide overlapping peak in generation 3
Outline complete carbohydrate digestion
- describe starch to glucose digestion and all enzymes involved eg amylase and breaking glycosidic bonds
- glucose is absorbed by active transport via co-transporters
- fructose is absorbed via F.D
