Unit 1.2c(ii) Flashcards
What is a ligand?
A substance that binds to a protein
What do R groups stabilise?
Folding of tertiary structures in proteins
What facilitates molecule binding?
R-groups on the proteins outer surface
What causes ligand binding sites on the protein surface?
Proteins folding
What on binding sites is complementary to ligands?
Their shape and chemistry
What matching elements bind the protein and ligand together?
Charged, polar and non-polar R-groups
What is the enzyme specific shape called?
The active site
What is ligand binding essential for?
Cell signalling that activates receptors or channels
Why is DNA considered a ligand?
Because it binds to proteins involved in replication, transcription and translation regulation in operons
How do DNA-protein interactions help fit DNA into the nucleus?
They help package long DNA into chromosomes
In eukaryotes how does DNA Lind to histone protein?
DNAs negatively charged backbone binds to the positively charged histone
What is formed when DNA wraps around a histone?
It forms a nucleosome
What happens when double stranded DNA binds to transcription factors?
Transcription is inhibited or initiated
What do transcription factors do?
Control gene expression
What happens if an activator protein binds to a specific DNA sequence?
Transcription of downstream genes is stimulated
What is the enhancer?
The part of DNA that that recruits transcription factors and RNA polymerase to the promoter region of the transcribed gene
Why do conformational changes occur?
The interaction between the ligand and protein binding site pull the polypeptide towards the ligand
What is a proteins change in shape called?
Conformational change
What does a change in protein shape cause?
A change in the proteins function
What regulates the proteins activity?
Conformational change
What is an allosteric enzyme/protein?
An enzyme/protein that has multiple sub-units (quaternary structure) with multiple binding sites
What happens when a ligand binds to an allosteric subunit?
The affinity of the rest increases
What causes allosteric enzymes activity to vary?
Small changes in substrate concentration
What are ligands that bind to allosteric enzymes called?
Modulators
When the subunits affinity increases how would they be described?
As showing cooperativity
Do conformational changes affect enzymes activity?
Yes as the active sites affinity changes
What is affinity?
The attractive force that binds atoms in molecules
What is cooperativity?
When the binding of 1 sub-unit increases the affinity for the remaining sub-units
What is the Haemoglobin subunit called?
Haem
What does Haem bind to?
Oxygen
What happens to the other 3 harms once one oxygen binds?
The next one will be easier and so on (affinity increases)
What the name given to the oxygen-Haem compound?
Oxy-Haemoglobin
What happens to the other subunits if oxy-Haemoglobin releases one of the oxygens?
The next will find it easier to release its oxygen and so on
How does low pH affect Haemoglobins affinity for oxygen?
It decreases the affinity
How does high temp affect Haemoglobins affinity for oxygen?
It decreases the affinity
Why does exercise cause more oxygen to be delivered to the tissue?
Exercise increases body temp, CO2 is produced and blood becomes acidified. This means less oxygen binds to the Haemoglobin so more goes to the tissue.
When would Haemoglobin hold lots of oxygen?
When it’s in a rich oxygen environment
When would Haemoglobin hold little oxygen?
In low oxygen environments
