Biological Molecules Flashcards
What is a monomer?
Give some examples
Monomer = small sub unit that firms larger molecules
e.g. monosaccharides, amino acids, mononucleotides
What is a polymer?
Give some examples
Polymer = multiple monomers joined together
e.g. polysaccharides, protein, DNA
What reaction occurs when 2 monomers join together to form a polymer?
Condensation reaction
What’s a hydrolysis reaction?
When a chemical bond is broken down between 2 molecules using water
Name 3 structures and functions of starch
insoluble = no osmosis occurs
large = don’t diffuse out of cells
H bonds = compact
Name 3 structures and functions of glycogen
branched = terminal end for hydrolysis
insoluble = no osmosis or diffusion occurs
1,4 + 1,6 glycosidic bonds = compact
Name 3 structures and functions of cellulose
straight, unbranched molecule
H bonds link myofibrils = high tensile strength
1,4 glycosidic bonds
Describe Benedict’s test for reducing sugars
- Add equal vol. Benedict’s reagent to sample
2.Heat in water bath for 5 minutes - +ve result = blue –> brick red ppt.
Describe Benedict’s test for non-reducing sugars
- -ve result = sol. remains blue
- Hydrolyse non-reducing sugar + heat in water bath for 5 minutes
- Neutralise mixture with sodium carbonate
- Proceed with Benedict’s test with same outcome
Describe the test for starch
- Add iodine
- +ve result = orange –> blue-black
Describe the test for lipids
- Add ethanol + shake
- +ve result = cloudy white ppt
How are triglycerides formed?
Condensation reaction between 1 glycerol and 3 fatty acids (forms ester bonds)
What’s the difference between a saturated and unsaturated fatty acid?
Saturated contain only single bonds
Unsaturated contain C=C double bonds
Describe the structure and function of phospholipids
Hydrophilic phosphate head
Hydrophobic fatty acid tails
Form a bilayer
Why is water a polar molecule?
Forms from delta -ve O and delta +ve H
O is more EN than H
What are the roles of hydrogen, iron ,phosphate and sodium in the body?
H = denatures H bonds + controls pH
Fe = used in forming Hb which transports oxygen in the blood
P = DNA, ATP and NADP
Na =
State the properties of water
High S.H.C
High L.H.V
Solvent for chemical reactions
Describe a test for proteins
- Add sodium carbonate + dilute copper sulfate to make Biuret’s reagent
- +ve result = blue –> purple
Primary structure of a protein
Number and type of amino acids in the sequence
Determined by codons on mRNA
Secondary structure of a protein
Alpha helix (N-H bonds on same side)
Beta-pleated sheet (N-H + C=O alternate sides)
Tertiary structure of a protein
Disulfide bridges (strong covalent bonds)
Ionic bonds (Relatively strong between R groups)
H bonds (easily broken + numerous)
Quaternary structure of a protein
More than one polypeptide chain
3D structure held by same bonds as tertiary
What are enzymes?
Biological catalyst
ES complex lowers Ea
Describe the induced fit model of enzyme action
Shape of active site is flexible to substrate
Enables ES complex to form
Lowers Ea
Name 5 factors that affect the rate of enzyme-controlled reactions and explain how?
Enzyme concentration (rate increases proportionally until ES complex forms)
Substrate concentration (rate increases proportionally until ES complex forms)
Inhibitor concentration
pH (increases proportionally to an optimum pH where the enzyme denatures after that point)
Temperature (increases proportionally to an optimum temp where the enzyme denatures after that point)
What’s the difference between competitive and non-competitive inhibitors?
Competitive bind to active site
Non-competitive bind at allosteric binding site
Increasing substrate concn decreases effect of competitive
Increasing substrate concn has no effect on non-competitive
What’s the role of DNA and RNA in living cells?
DNA = genetic info that determines inherited characteristics (codes for RNA and amino acids)
RNA = transfers genetic info from DNA to ribosomes
What are the components of a DNA nucleotide?
Deoxyribose sugar
Phosphate group
Organic base (A,C,G,T)
Compare and contrast the bases in DNA from those in RNA?
DNA = adenine + THYMINE (2 H bonds)
cytosine + guanine (3 H bonds)
RNA = adenine + URACIL (2)
cytosine +guanine (3)
Describe the structure of DNA
Sugar phosphate backbone (stability)
Many weak H bonds (break for replication)
Double helix
Complementary base pairing
Outline DNA semi-conservative replication
- DNA helicase breaks H bonds between base pairs
- Strands act as templates
- Free nucleotides attach to complementary base pairs
- DNA polymerase catalyses the condensation reaction joining adjacent nucleotides
- H bonds re-form
Describe the Meselson-Stahl experiment
- Bacteria grown in medium containing N15 for many generations
- Some bacteria moved to medium containing lighter N14 (samples extracted after a few cycles of DNA replication)
- Centrifugation meant heavier pellets settled at the bottom of the tube
What’s the role of ATP in cells?
Releases energy couple to metabolic reactions
Phosphorylates compounds to make them more reactive
How is ATP hydrolysed and re-synthesised in cells?
ATP hydrolase catalyses:
ATP —> ADP + Pi
ATP synthase catalyses condensation reaction:
ADP + Pi —> ATP
How is ATP suited to its function?
High energy bonds
Small amounts of energy released at a time (less wasted)
Single-step hydrolysis (available quickly)
Readily re-synthesised
How is ATP suited to its function?
High energy bonds
Small amounts of energy released at a time (less wasted)
Single-step hydrolysis (available quickly)
Readily re-synthesised
