Molecular Biology Flashcards
importance of carbon
- the most important element to life
- basic building block that can be used to make a wide range of different molecules
- forms covalent compounds
importance of hydrogen
- forms part of water
- forms hydrogen bonds, which gives water many of its properties
- bonds to carbon to form hydrocarbons
importance of nitrogen
- aids in digestion and growth
- necessary for foetus development
importance of Sulfur
- makes up some amino acids
- protects cells from environmental hazards (e.g. pollution, radiation)
- helps liver to function properly
- important in forming blood clots
- keeps skin supple and elastic
importance of calcium
- bone and teeth formation
- muscle growth
- electrical impulses in the brain
- aids in blood clotting
- helps maintain blood pressure
importance of iron
- component of haemoglobin
- aids in tendon and ligament formation
- needed to maintain a healthy immune system
importance of sodium
- needed for nerve impulses to be sent
- important part of blood plasma
- maintains the proper amount of water in our blood
importance of phosphorus
- found in membrane structures
- needed for healthy formation of bones and teeth
- central part of energy storage system
- aids in cell growth and repair
characteristics of water
polar molecule due to oxygen-hydrogen dipole
thermal properties of water
- high specific heat capacity
- high latent heat of vaporisation
- high boiling point but can evaporate below boiling point
- bc of the strong hydrogen bonds
- this makes water an effective coolant
cohesive properties of water
- water molecules stick to each other
- due to hydrogen bonds forming between them
solvent properties of water
- many substances can dissolve in water
- due to water’s polarity
organic compounds
based on carbon and can be found in living things
e.g. lipids, proteins, carbohydrates
inorganic compounds
anything that isn’t organic
properties of amino acids
- monomers that combine to form polypeptides, which in turn form proteins
- they are all soluble and have the same structure (except the R group)
carbohydrates
- monosaccharides
- disaccharides
- polysaccharides
monosaccharide
- carbohydrates with relatively small molecules
- soluble in water
- taste sweet
significance of glucose
- all cells use glucose to respire
- building block for a lot of larger molecules
ribose
- a pentose (5-carbon sugar)
- deoxyribose is a modified version, used in DNA as the sugar phosphate backbone
fatty acids
- the basis of triglycerides and many other lipids
- the basis of phospholipids
- hydrophobic
structural characteristics of fatty acids
- mostly made up of 16-18 C atoms but can be anywhere from 14-22
- the carboxyl end (you can tell by the C=O double bond) is hydrophilic
- forms spheres called micelles in water (imagine a round phospholipid bilayer, sans proteins and double tail)
examples of monosaccharides
- glucose
- galactose
- fructose
examples of disaccharides
- lactose: glucose + galactose
- sucrose: glucose + glucose
- maltose: glucose + fructose
examples of polysaccharides
- glycogen
- cellulose
- starch
most common elements in biological organisms
- carbon
- hydrogen
- oxygen
triglycerides
simple lipids
e.g. fats, oils
functions of lipids
- energy store: lipids transfer twice as much energy as carbohydrates
- metabolic water source: when fats are used in respiration, both energy and water are released
- thermal insulation
- buoyancy: fat isn’t as dense as muscle/bone
- electrical insulation: lipids form myelin sheaths around nerve cells
- hormone: steroids can act as hormones
- cell receptors: glycolipids’ role in phospholipid bilayer
- structure: e.g. phospholipid bilayer
DNA nucleotide components
- pentose sugar (ribose for RNA, deoxyribose for DNA)
- phosphate
- nitrogen base
types of nitrogen bases
- cytosine (C)
- guanine (G)
- adenine (A)
- thymine (T)
- uracil (U)
DNA structure:
- 2 anti-parallel polynucleotide chains
- double helix spiral structure
- held together by hydrogen bonds
- sugar-phosphate backbone
- complementary base pairing: A to T, G to C
- base order: G C T A
DNA replication process
catalyst: DNA polymerase
1. DNA double helix unwinds, catalysed by helicase, which causes breaking of hydrogen bonds between the base pairs (the structure is called a replication fork)
2. free nucleotides begin to attach to their complementary base pairs on the parent strands, which are still anti-parallel
3. the hydrogen bonds reform, and the sugar and phosphate on the free nucleotides condense to form the backbone on the new DNA molecules
significance of complementary base pairing
- makes sure the new DNA strands are perfect copies of the original
- the complete genome would be successfully copied, ensuring all genes remain intact
- opposite pairs are attracted, and the structure allows DNA polymerase to check for mistakes
explain the semi-conservative nature of DNA replication
- one of the strands always come from the parent chromosome
- the other strand is newly synthesised during replication from free nucleotides
- so half the original molecule is always conserved
RNA structure
- relatively short compared to DNA
- base order: G C U A
- complimentary base pairing: A to T, U to C
- made up of a single strand that can form mRNA, tRNA, or rRNA
DNA transcription process
catalyst: RNA polymerase
1. the DNA double helix is unwound by DNA helicase, breaking the hydrogen bonds
2. the DNA opens at the transcription site, and free nucleotides pair with DNA nucleotides. the main difference is that U replaces T, so it’s A to T, U to C instead
3. RNA polymerase forms phosphodiester bonds to make the backbone of the mRNA molecule
4. the mRNA detaches and leaves the nucleus via nuclear pores in the membrane, and enters the cytoplasm to travel to the ribosome
transcription site
position of gene that needs to be copied
sense strand
- coding strand
- template for the mRNA
anti-sense strand
- where the mRNA is built on
- has same pattern as sense strand due to complimentary base pairing
codon
- each sequence of 3 bases provides a code for one amino acid
- also called triplet code
- some codons are start/stop codons denoting where to begin/end the sequence
translation process
active process using ATP
- amino acids are activated by combining with tRNA in cytoplasm
- each tRNA binds to the anticodon and to the amino acid (this binding is catalysed)
- once the mRNA molecule is transcribed, it’s sent to the ribosome for translation
- the ribosomes move along the mRNA to “read” the code, beginning at the start codon
- the tRNA molecules, with their amino acids, find their complimentary codon on the mRNA chain
- the tRNA separates from the amino acid and the mRNA and goes back to find more amino acids
- the process continues until a stop codon is reached and the polypeptide chain is released
anticodon
the complimentary codon for the mRNA
