Lifestyle & Risk Flashcards
What are the 4 bases in DNA?
Adenine,thymine,cytosine,guanine
Which dna bases are purines and which are pyrimidines?
A,G = purines. T,C = pyrimidines
What enzyme breaks the hydrogen bonds in dna replication?
DNA Helicase
Describe the 3 steps of dna replication
- DNA helicase unwinds and breaks hydrogen bonds exposing the bases and form 2 template stands
- New dna is built up from the 4 nucleotides( A,C,G,T) that are abundant in the nucleoplasm,they then attach themselves to the bases on the old strands through complimentary base pairing
- DNA polymerase joins new nucleotides to each other by strong covalent bonds forming the sugar-phosphate backbone then winding enzyme winds new strands up to form 2 double helixes creating 2 new identical molecules to the old singular molecule
Describe experiment carried out by Meselson and Stahl demonstrates the semiconservative replication of DNA. Include an outline
of the method and a description of the results (5).
• Bacteria initially fed on N15/heavy N
• Bacteria then fed on N14/light N
• DNA extracted and separated (centrifugation) after 1 and 2 (and more) cell cycles
• DNA initially as a single band of heavy DNA (or diagram)
• DNA after 1 cycle of DNA replication as a single band of
intermediate DNA (or diagram)
• DNA after 2 cycles as one band of intermediate and one band of light DNA (or diagram)
Define a monomer. Give examples
Smaller units that join together to form larger molecules
- monosaccharides(glucose,fructose,galactose)
- amino acids
-nucleotides
Define polymer.give some examples
Molecules formed when many monomers join together
- polysaccharides
- proteins
- DNA/RNA
What happens in a condensation reaction
Chemical bond forms between 2 molecules and a molecule of water is produced
What are disaccharides and polysaccharides and what bonds form these?
Disaccharides= 2 momomers joined together by 1 chemical bond
Polysaccharides= multiple monomers Joined by many chemical bonds
(1,4 or 1,6) glycosidic bond
What are carbohydrates and what bond joins them together ?
Carbohydrates are molecules which consist only of carbon,hydrogen and oxygen and they’re long chains if sugar units called saccharides. A single monomer is called a monosaccharide ant glycosidic bonds can join them together to create disaccharides(2 molecules) and polysaccharides (many molecules)
Give examples of monosaccharides,disaccharides and polysaccharides
Monosaccharides=
glucose(6 carbon atoms in each molecule,can be alpha or beta),fructose and galactose.
Disaccharides=
maltose(2 glucose molecules),
Sucrose(glucose & fructose) ,
Lactose(glucose & galactose)
Polysaccharides=
Glycogen( many alpha glucose)
Starch(many alpha glucose)
Cellulose(many beta glucose)
What are lipids and what are the main lipid types?
Biological molecules made of carbon,hydrogen and oxygen
Main lipid types=
triglycerides( 1 mol of glucose and 3 fatty acids joined by ester bonds.can be saturated or unsaturated)
Phospholipids(one fatty acid substituted by a phosphate-containing group)
What is the difference between saturated and unsaturated lipids?
Saturated-don’t contain any c-c double bonds,found in animal fats.
Unsaturated- DO contain c-c double bonds meaning they can bend,are liquid at room temp,found in plants.
What are the different properties of triglycerides and phospholipids?
Triglycerides-
high ratio of energy storing C-H bonds to carbon atoms,excellent energy store),
Low mass to energy ratio(+ storage molecule), ‘
What are the 2 key chemical reactions?
Condensation reaction- joining 2 molecules creating a chemical bond and removing water
Hydrolysis reaction- breaking of a chemical bond between 2 molecules involving the use of water