VETS-111 Cell Biology Flashcards
How is iron stored?
Complex with ferritin in the liver.
What is Transferrin?
Carries iron in blood plasma.
Functions of proteins
1) enzymology catalysts
2) transport and storage
3) movement
4) structural materials
5) immune protection antibodies
6) membranes
7) regulators and receptors
Structure of an amino acid in neutral solution
Zwitterion
Name if pH where amino acid has no net charge
Isoelectric
Two enantiomers of an amino acid
L and D-isomers
Which form of amino acids do proteins contain
L-isomer
Amino acids are joined by…
Peptide bonds
A polypeptide starts at which end?
Amino terminal residue
An amino acid ends at what end?
The carboxyl terminal residue
Is arginine an essential amino acid?
Yes
Is Histidine an essential amino acid?
Yes
Is Isoleucine an essential amino acid?
Yes
Is leucine an essential amino acid?
Yes
Is lycine an essential amino acid?
Yes
Is methionine an essential amino acid?
Yes
Is phenylalanine an essential amino acid?
Yes
Is threonine an essential amino acid?
Yes
Is tryptophan an essential amino acid?
Yes
Is valine an essential amino acid?
Yes
Is alanine an essential amino acid?
No
Is asparagine an essential amino acid?
No
Is aspartic acid an essential amino acid?
No
Is cysteine an essential amino acid?
No
Is glutamic acid an essential amino acid?
No
Is glutamine an essential amino acid?
No
Is glycine an essential amino acid?
No
Is proline an essential amino acid?
No
Is serine an essential amino acid?
No
Is tyrosine an essential amino acid?
No
Which amino acid should be avoided by diabetics as a supplement
Cysteine (interacts with insulin)
Which amino acid is a precursor for serotonin?
Tryptophan
Rigidity In the primary structure of polypeptides
Caused by carbon-nitrogen bond having partial double bond character.
Interactions in the secondary structure of amino acids
Hydrogen bonds:
Beta pleated sheets
Alpha helix
Which amino acid is a helix breaker
Proline
Interactions within the tertiary structure
Disulphide bridges (2 cysteine) Hydrogen bonding Electrostatic/ionic Hydrophobic Polar (OH)
What is the quaternary structure
Multiple chains interacting forming subunits
Types of super secondary structures
BaB unit
Greek key of B-pleats
What is denaturation
Loss of proteins structure and thus function
Causes of denaturation
Changes in pH
Salt conc
Temp
Environmental changes
What aids protein folding
Chaperonins
Ways to determine protein structure
X-Ray crystallography
NMR spectroscopy
Result of protein misfolding
Loss or modification of activity
Aggregation
Cause of sickle cell disease
Amino acid substitution in harmoglobin causes aggregation and fibres. Deformed RBCs
Cause of Cystic fibrosis
Deletion of Phe in CFTR protein which is degraded.
What is p53
Tumour suppression gene. Mutations present in tumour cells
Cause of Alzheimers
B-amyloid cleaved from APP produces aggregations of plaques in the brain
What is PrPc
Native form of prion protein mainly a-helix.
What is PrPSc
Amyloidogenic form. Mix of B-sheets and a-helices. Aggregates form insoluble plaques in brain
What causes huntingdons?
Huntingtin protein is longer than normal and end is cleaved to form aggregates and inclusions.
What causes Parkinson’s?
Inclusions in the cytoplasm called Lewy bodies formed from multiple proteins.
Cause of cataracts
Aggregation of crystallins due to environmental factors (UV or oxidising agents)
Fibrous proteins
Filamentous elongated held by strong bonding
Globular proteins
Compact structures that interact with other molecules e.g enzymes, antibodies
Membrane proteins
Embed in membranes and transmit molecules in and out cell
Structure of collagen
Triple helix. Repeating triplet of glycine, X (often proline) and Y (often hydroxyproline)
Structure of glycerophospholipid
Two hydrophobic fatty acid tails joined to hydrophilic head (glycerol, phosphate and choline)
Define steroid
Lipids with a carbon skeleton consisting of four fused rings
Define ligand
Extra cellular signalling molecules
Define a catalyst
Increases the rate of a chemical reaction without being changed itself. Cannot alter the position of equilibrium but allows equilibrium to be reached quicker.
Define free energy of activation
Equal to the difference in free energy between the transition state and the substrate.
Define induced fit of an enzyme
Frequent binding of substrate induces a conformational change in the active site.
Factors affecting enzyme activity
Substrate concentration Enzyme concentration Temperature Post translational modification (e.g phosphorylation, Proteolytic activation) Coenzymes and cofactors pH
Most coenzymes are related to what structural group
Vitamin B group
What is end product feedback
Inhibits the committed step (first step to produce an intermediate unique to the pathway) earlier in the pathway.
What is allosteric regulation
Molecules that regulate an enzymes activity by binding to a site remote from the active site.
Define cooperativity
Binding of a substrate can trigger the same conformational change in all other subunits of the enzyme
Define isoenzyme
Different forms of an enzyme which catalyse the same reaction
What does LDH stand for
Lactate dehydrogenase
Structure of LDH
2 subunits H and M. 5 different combinations
Where is H4 and H3M found?
Mainly heart and RBCs
Where is H2M2 LDH found?
Brain and kidney
Where is HM3 and M4 LDH found?
Skeletal muscle and liver
What does LDH isoenzymes in the blood indicative of?
Cell death. E.g myocardial infarction, infectious hepatitis and muscle diseases.
What is a multi-enzyme complex
Aggregation of several enzymes/coenzymes into a single functional unit. Usually perform a multi-step transformation