1 - The Molecules of Life - Intro Flashcards
What can causes random variation in organisms
Random mutation - can change structure and function of protein, etc.
different effects of mutations
silent - no effect
small effect, no real advantage or disadvantage
missense or nonsense - disadvantageous
advantageous - very rare, confers selective advantage (prodcues selective pressure)
when did prokaryotes first appear
~3500 years ago
5 kingdoms
animalia
plantae
fungi
protist
monera
3 domains
archaea, eubacteria, eukaryotae
multicellular organisms - levels of interrelationship
organ systems
organs
tissues
cells
molecules
- all work together, and coordinated by signalling systems - e.g. cell signalling - enzymes, etc.
which molecules account for moost living matter
- what do they do
water
inorganic ions
other small molecules
- usually serve as substrates that for many chemcial reactions inside cells - metabolites - used in metabolism and cell signalling
universal energy molecule
ATP - Adenosine Triphosphate
- stores readily available chemical energy in two of its chemical bonds
ATP breakdown products
ADP - adenosine diphosphate
inorganic phosphate - Pi/HPO4^2-
use of chemical energy released from ATP bond breaking
energy requiring (active) processes
- e.g. muscle contraction, protein biosynthesis
where energy comes from to produce ATP
- example
many types of cells break down food molecules which contain chemical energy in their bonds
- sugar broken down, energy in chemical bonds released, captured in energy rich bonds in ATP
- process occurs in most bacteria, animal and plants cells, and other types of cell
Catabolism def
breaking of bonds in polymer chains (macromolecules) via hydrolysis reaction to produce monomers (small monomers)
Anabolism def
joining of monomers by condensation reaction via ATP to produce polymers
other term for polymer
macromolecules
4 macromolecules and monomers
polysaccharides - sugars (hexose or pentose)
proteins - amino acids
nucleic acids - nucleotides
lipids - fatty acids
two types of glucose
alpha
beta
amino acid common chain length in proteins
100 - 1000 amino acids
some functions of proteins
- enzymes - catalyse cellular reactions involving molecules or macromolecules
- structural components of cells - e.g. cytoskeleton
- some proteins in cytoskeleton associated with movement of subcellular structures, e.g. chromosomes using chemical energy in ATP bonds
- bind adjacent cells together or form part of extracellular matrix
- sensors - some change shape as conditions in a cell change, e.g temp, ion conc., pH etc.
- embedded in plasma membrane - import and export molecules and ions in cell
cell signalling - hormones or receptors
transcription factors - turn genes on or off
who discovered DNA and when
Watson and Crick - 1953
- based on X-ray crystallography by Rosalind Franklin
simple DNA strcuture
two long helical stands coiled around a common axis to form a double helix structure
- bases projected from sugar phsophate backbone
- complementary bases join via weak hydrogen bonds, AT and CG
why is the double helix shape so important
allows heredity - transfer of genetically determined characteristics from one generation to the next
four cyclic organic bases in DNA
ATCG
what does complementary base pairing allow in DNA molecules
allows DNA replication and inheritance, and zipping back together of complementary strands in correct conditions
- other DNA techniques such as electrophoresis, DNA sequencing etc.
where is genetic info held in DNA
its sequence - linear order of nucleotides along a strand
what are genes
specific segments of DNA
How many protein encoding genes for some organisms
bacteria - a few thousand
yeast and other unicellular eukaryotes - ~5000
humans and other metazoans ~13000 - 23000
Plants - many more than animals
What are metazoans
Eukaryotic multicellular organisms - most animals
what are conserved genes
genes that have …
two processes in protein encoding and production
transcription and translation
Transcription and translation simple
Transcription: protein coding region of gene os copied into single stranded RNA
- the RNA contains the same sequence as the double stranded DNA - uses it as a template
- RNA polymerase catalyses linkage of nucleotides with complementary bases via condensation reaction (produce phosphodiester bonds) using DNA as a template
- RNA is processed into mRNA, which moves out of the nucleus via nuclear pores to the cytoplasm adn to the ribosome
- Ribosome (composed of RNA and proteins) attaches to mRNA and carries out translation
Translation: ribosome assembles and linsk together amino acids in precise order dictated by mRNA sequence - according to the genetic code
RNA uses
- transcription and translation in protein biosynthesis
- catalyse some reactionss - certain RNA molecules catalyse peptide bond formation between amino acids
How do genes affect different cell types
certain genes are transcribed in different cells.
Some genes may be active/turned on to make proteins, or turned off (via transcription factors).
Two main parts of protein-encoding genes
- coding region - specifies amino acid sequence of protein
- regulatory region - where transcription factors activate or repress transcription of certain genes
- meaning the regulatory region controls when and in which cells the gene’s encoding protein is made
Main function of phospholipids
Phospholipid bilayer in plasma membranes
Basic structure of plasma membranes - phospholipid bilayer
bipartite
- hydrophilic phosphate head - faces outwards
- hydrophobic fatty acid tail - facing inward
- transmembrane and transport proteins
- cholesterol scattered throughout - regulated fluidity of membrane
function of some proteins in plasma membrane
phospholipid bilayer impermeable to water
- so transport proteins used to move certain molecules and ions in and out of the cell
- used to attach cell to other cells or to surrounding polymers
- some give the cell its shape or allow it to change shape
risks of damaged DNA
- what defences are there against this
UV and gamma radiation, as well as some chemical may damage DNA
- this can cause mutations
- causes errors in DNA replication
risks of damaged DNA
- what defences are there against this
UV and gamma radiation, as well as some chemical may damage DNA
- this can cause mutations
- causes errors in DNA replication
- can cause uncontrolled cell growth - tumour formation etc.
- ther are checkpoints in the cell cycle and other mechanisms that can prevent erroneous DNA replication
