2.4 Proteins Flashcards
What are proteins comprised of?
Long chains of amino acids
What do all amino acids share?
A common basic structure
What is the basic structure of amino acids?
A central carbon atom attached to an amine group, a carboxylic acid group, a hydrogen atom and a variable side chain
How many different amino acids are there?
20
Where are amino acids joined together?
On the ribosome
What are the long chains of amino acids called?
Polypeptides
What do polypeptides make up?
Proteins
How does each type of amino acid differ?
The composition of the variable side chain
What causes each proteins fold and function differently?
Because they have a different distinct chemical properties
Why do proteins fold and function differently?
To work in accordance to its specific position within the polypeptide chain
Why are organisms capable of producing a huge range of possible polypeptides?
Because most polypeptide chains have 50 - 2000 amino acid residues
What is the bonding between amino acids?
Covalent bonding
What type of reaction is needed to join amino acids?
Condensation reaction
What is the covalent bond between the amino acids called?
A peptide bond
How can polypeptide chains be broken down?
Hydrolysis reactions
What does amino acids joining together form?
A dipeptide and water
What does the breakdown of polypeptide chains require and why?
Water to reverse the process
Where do the peptide bonds form?
Between the amine and carboxylic acid groups of adjacent amino acids
What forms water during the formation of a peptide bond?
The amine group losing a hydrogen atom and the carboxylic acid loses a hydroxyl (OH) creating water
What is the order of amino acid sequence called?
Primary structure
What does primary structure determine?
The way the chain will fold
Why will different amino acid sequences fold into different configurations?
Due to the chemical properties of the variable side chains
What will amino acids commonly fold into?
Secondary structures
What is it called when the amino acids fold into two stable configurations?
Secondary structures
When do alpha helices occur?
When the amino acid sequence folds into a coil/spiral arrangement
When do beta pleated sheets occur?
When the amino acid sequence adopts a directionally oriented staggered strand conformation
What causes both alpha helices and beta pleated sheets?
Hydrogen bonds forming between non adjacent amine and carboxyl groups
What happens when no secondary structure exists?
The polypeptide chain will form a random coil
What is the tertiary structure?
The overall three dimensional configuration of the protein
What determines the tertiary structure of a polypeptide chain?
The interactions between the variable side chains
What are four examples of interactions between the variable side chains?
Hydrogen bonds
Disulphide bridges
Ionic interactions
Polar associations
What affects the overall shape of the polypeptide chain?
The affinity or repulsion of side chains
What determines all levels of protein folding?
Primary structure
What determines the affinity or repulsion of side chains?
The position of specific amino acids within a sequence
What is it called when certain proteins have a fourth level of structural organisation?
Quarternary structure
Where do you find quaternary structures?
In proteins that have more than one polypeptide chain linked together
What type of structure is it when a protein has an inorganic prosthetic group as part of their structure?
Quaternary structure
Will all proteins have a quaternary structure and explain your answer?
No as many proteins only have a single polypeptide chain
What is an example of a protein with a quaternary structure?
Haemoglobin
How many and what polypeptide chains does haemoglobin have?
Four
two alpha chains
Two beta chains
Apart from multiple polypeptide chains what does haemoglobin have to make it have a quaternary structure?
A prosthetic group
What is denaturation?
Denaturation is a structural change in a protein that results in the loss of its biological properties
What will cause the tertiary structure to alter its activity and why?
Any change or abrogation to the tertiary structure as the way a protein folds determines its function
What are the two key conditions that can cause denaturation?
Temperature and pH
What will high levels of thermal energy do to the proteins?
Break the hydrogen bonds that holds the protein together, causing them to unfold and lose its ability to function
What does changing the pH of a protein do?
Alter the charge which alter the proteins solubility and overall shape
What is the perfect temperature or pH called?
The optimum
What is a gene?
A gene is a sequence of DNA which encodes a polypeptide sequence
What is a gene sequence converted into?
A polypeptide sequence
What are the two processes that convert gene sequence into a polypeptide sequence?
Transcription and translation
What does transcription do?
Makes an mRNA transcription based on a DNA template
What does translation do?
Uses the instructions of the mRNA transcript to link amino acids together
Typically one gene will code for what?
One polypeptide
What are the three exceptions to the fact that one gene will code for one polypeptide?
Genes may be alternatively spliced to generate multiple polypeptide variants
Genes encoding tRNA sequences are transcribed but never translated
Genes may be mutated and consequently produce an alternative polypeptide sequence
What is the proteome?
All of the proteins expressed within a cell, tissue or organism at a certain time
Why are proteomes of any given individual unique?
As protein expression patterns are determined by an individuals gene
Is the proteome larger or smaller than the number of genes in an individual?
Larger
What are the two reasons a proteome may be larger than the genes in a person?
Gene sequences may be alternatively spliced following transcription to generate multiple protein variants from a single gene
Proteins may be modified following translation to promote more variations
What are the different functions of proteins? (shits me)
Structure
Hormones
Immunity
Transport
Sensation
Movement
Enzymes
What are two examples of the protein function structure?
Collagen
Spider silk
What is collagen?
Component of the connective tissue of animals
What is spider silk?
A fibre spun by spiders to make webs
What are two examples of the protein function hormones?
Insulin
Glucagon
What is insulin?
Protein produced by the pancreas and triggers a reduction in blood glucose levels
What is glucagon?
Protein produced by the pancreas that triggers an increase in blood glucose levels
What is an example of the protein function of immunity?
Immunoglobulins
What are immunoglobulins?
Antibodies produced by plasma cells that are capable of targeting specific antigens
What are two examples of the protein function transport?
Haemoglobin
Cytochrome
What is haemoglobin?
A protein found in red blood cells that is responsible for the transport of oxygen
What is cytochrome?
A group of proteins located in the mitochondria and involved in the electron transport chain
What is an example of the protein function sensation?
Rhosopsin
What is rhodopsin?
A pigment in the photoreceptor cells of the retina that is responsible for the detection of light
What are two examples of the protein function movement?
Actin
Myosin
What is actin?
Thin filaments involved in the contraction of muscle fibres
What is myosin?
Thick filaments involved in the contraction of muscle fibres
What is an example of the protein function enzymes?
Rubisco
What is rubisco?
An enzyme involved in the light independent stage of photosynthesis
