heredity - DNA and polypeptide synthesis Flashcards
why is polypeptide synthesis important?
- The role of DNA is to code for specific polypeptides (proteins).
- All organisms produce proteins.
- These proteins have specific functions: transport, enzymes, structural, hormones, and antibodies.
- Without these proteins, these functions would not occur.
- Life would cease to exist.
prokaryote structure
- lack distinct nucleus and no membrane enclosed organelles
- contain free floating ribosomes
- generally small 1-10 micrometres
- unicellular
eukaryote structure
- distinct nucleus and contain membrane enclosed organelles
- contain ribosomes
- generally larger in size 10-100 micrometres
- unicellular or multicellular
DNA in prokaryotes
DNA in prokaryotes are usually a single circular chromosome and plasmids. DNA contains no histones and is found in the cytoplasm (nucleoid). The DNA does not contain introns.
plasmid
Small circular, independent double stranded DNA molecule. Plasmids can frequently be transmitted from one bacterium to another.
intron
A segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes
intron
A segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes
DNA in eukaryotes
DNA in eukaryotes is linear, associated with histones and is found in the nucleus. The genes contain introns.
mitochondrial DNA
Both mitochondria and chloroplasts have their own DNA separate to the nucleic DNA.
Mitochondrial DNA (mtDNA) is a double stranded, circular molecule with no introns (similar to prokaryotes).
endosymbiosis
A relationship in which one organism lives inside the other, the two typically behaving as a single organism. It is believed to be the means by which such organelles as mitochondria and chloroplasts arose
within eukaryotic cells.
chloroplast DNA (cpDNA)
a double-stranded, circular molecule with no introns.
peptide
short chain of 2-50 amino acids
polypeptide
linear molecules made up of multiple peptides
polypeptide
linear molecules made up of multiple peptides
proteins
proteins are the functional unit, made up of one or more polypeptides
amino acids
Amino acids are simple organic compound containing a carboxyl (— COOH) and an amino (— NH2) group. They are the building blocks of proteins.
essential amino acids
- must be obtained from food
- histide, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine
non-essential amino acids
- produced by our bodies
- arginine, alanine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine and tyrosine
advantages of models
- simplifies complex concepts
- predictive power
- leads to increased understanding and future research
disadvantages of models
- over-simplification can be misleading
- may not be accurate
- lack detail
transcription
the process by which a complementary copy (mRNA) of a gene (DNA) is made in the nucleus
translation
the process by which mRNA sequence is converted into a specific sequence of amino acids (carried by tRNA) in the ribosomes
mRNA
single stranded nucleic acid, consisting of ribose sugar, phosphate backbone and nitrogen bases (A, U, G, C)
tRNA
small RNA molecule that transfers specific amino acids to the ribosome during formation polypeptides
codon
set of three nitrogen bases in mRNA
anti-codon
complementary set of three nitrogen bases on tRNA
the importance of mRNA and tRNA in transcription and translation
explain - DNA does not leave the nucleus. As a result, a message must be sent from the nucleus to the ribosomes where protein synthesis occurs. This message is sent in the form of mRNA
assess - protein synthesis would therefore not be possible without mRNA
the function and importance of polypeptide synthesis
As a result of the complementary nature of the mRNA and tRNA codon-anticodon complex the
specific sequence of amino acids required for protein synthesis occurs. Protein synthesis would therefore not be possible without tRNA.
the function and importance of polypeptide synthesis
every organism makes proteins which are vital for key functions meaning that without proteins, life would cease to exist, hence why the process of making proteins is a significant one
primary protein structure
The primary structure is the specific linear sequence of amino acids that make up a polypeptide chain.
secondary protein structure
Regular, repeated patterns of folding of the protein backbone.
tertiary protein structure
The overall folding of the entire polypeptide chain into a specific 3D shape.This final shape is determined by disulphide and ionic bonds between the “side chains” on the amino acids in the alpha helices and beta sheets.
quaternary protein structure
Occurs when a protein is made up of two or more polypeptides. Quaternary structure describes the way in which the different polypeptide subunits are arranged together to form the overall structure of the protein.
transport proteins
involved in either the active or passive movement of substances across cellular membranes or between cells (an example is haemoglobin).
structural proteins
the largest of the protein groups. They are typically found in body tissues that require tensile strength which is provided by the long and fibrous structural proteins. Some examples are collagen and keratin.
enzymes
Enzymes speed up reactions by lowering the activation energy required for the reaction to occur. They hold substrate molecules in a way that makes the reaction more likely to occur. Without enzymes, metabolism would be too slow to support life.
protein hormones
Protein hormones are typically globular in shape and water soluble. They function by binding to receptors on the outside of a cell and causing a change to occur inside the cell. Some examples are insulin, glucagon.
genotype
the set of genes in the DNA responsible for a particular phenotypic trait
phenotype
the physical expression of that trait, as a protein or physically observable characteristic
effect of temperature on reptile gender
During a thermosensitive period (TSP) of reptile egg incubation, gonadal tissue is responsive to temperature. This influences the gender of the offspring.
effect of soil on pH on hydrangea
Flower colour is determined by soil pH. The pH effects the availability of other ions in the soil and these ions are responsible for the colour change.
