MGD S3 - Protein activity regulation, Chromosomes, DNA and Nucleotides Flashcards
What is Allosteric enzyme control and what kind of enzymes does it control?
Activator or inhibitor binds to one subunit to either enhance or inhibition started binding to other sites
Activators increase proportion of enzyme in the high affinity R state
Inhibitors increase the proportion of enzyme in the low affinity T state
Controls multisubunit enzymes
Describe covalent modification of enzymes.
What is the most important modification made and why?
Additional groups covalently bound to amino acids in the chain.
Phosphate groups bound by kinase or removed via phosphatase.
This is important because phosphate group are charged and large, which can have a great effect on enzyme activity/conformation.
What is Proteolytic activation?
Cleavage of a protein (E.g. Inactive precursor such as a zymogen) by a protease enzyme to activate when required.
List the major regulatory mechanisms that control enzyme activity.
Allosteric control Substrate or product conc Covalent modification Proteolytic activation Regulation of enzyme amount (synthesis vs degradation)
What enzyme controls the rate determining step of glycolysis and what is the major factor in its regulation?
Phosphofructokinase
Allosteric control
What are phosphofructokinase inhibitors and what effect does this have on its substrate affinity?
ATP, citrate, H+
Shifts affinity curve to the right hence decreasing affinity.
What are phosphofructokinase’s activators and what effect does this have on it’s substrate affinity?
AMP, fructose-2,6-biphosphate
Shifts affinity curve to the left, hence increased affinity.
What is an enzyme cascade?
A chain of enzymes that activate other enzymes.
What is the function of kinase enzymes?
Kinase enzymes transfer a phosphate from ATP to the -OH group of Ser, Tyr or Thr
List some zymogens, their post cleavage enzymes and where they’re found.
Stomach:
Pepsinogen –> pepsin
Pancreas: Chymotrypsinogen --> chymotrypsin Trypsinogen --> trypsin Procarboxypeptidase --> carboxypeptidase Proelastase --> elastase
Name the purine bases and give a short description of their general structure.
Guanine, adenosine
Two ring structure
Name the pyrimidine bases and give a short description of their general structure.
Thymine, cytosine, uracil
One ring structures
What is a base pair?
List the base pairs found in DNA or RNA
Hydrogen bonded pair of bases, one purine, one pyrimidine
G-C
A-T
A-U
How are DNA/RNA strands labelled?
From 5’ to 3’ where 5’ is the phosphate end (phosphate on carbon 5) and 3’ is the hydroxy end (-OH group on carbon 3)
When labelling drawn out antiparallel DNA strands, which strands is labelled 5’ - 3’ and which strand is 3’- 5’?
When both strands are drawn out like this, it is called a…?
Top strand = 5’ - 3’Lower strand = 3’ - 5’
Duplex structure
What are Histones and how do they relate to DNA?
Histones are proteins that DNA strands wrap around (2 wraps per histone molecule).
What is a DNA/Histone complex called?
Nucleosome
How are nucleosomes further compacted?
Nucleosomes wrapped into a solenoid structure
During mitosis what form do chromosomes take and what can be said about gene function during mitosis?
Chromosomes densely packed in short fat fibres. No gene expression or replication.
During interphase what form do chromosomes take and what can be said about gene function during interphase?
Chromosomes decondensed (beads on a string) and genome will express and replicate.
How are polynucleotide chains linked?
Covalent phosphodiester bonds
Are DNA/RNA chains polar?
Yes
Base pairing is what type of bonding?
Hydrogen bonds
Base pair bonding occurs between what two groups?
Oxygen (electronegative)
Nitrogen/hydrogen (positive)
