MGD Session 1 Flashcards
What are the main organelles in a mammalian cell?
Golgi Apparatus Cytoplasm Lysosome Mitochondria Endoplasmic Reticulum Nucleus Nucleolus Plasma membrane Ribosome
Briefly outline the function of the golgi apparatus
Glycosylation and Export of proteins
Briefly outline the function of the cytoplasm
Metabolism of cabohydrates, amino acids and nucleotides, fatty acid synthesis
Briefly outline the function of the lysosomes
Cellular digestion
Briefly outline the function of the mitochondria
ATP Synthesis
Briefly outline the function of the endoplasmic reticulum
Export of proteins, membrane synthesis, protein synthesis, detoxificiation
Briefly outline the function of the nucleus
DNA synthesis and repair
Briefly outline the function of the nucleolus
RNA processing and ribosome assembly
Briefly outline the function of the plasma membrane
Cell morphology and movement
Briefly outline the function of the ribosomes
Protein synthesis
List the features that a eukaryotic cell has where a prokaryote does not.
A nucleus Chromosomes Endoplasmic Reticulum Lysosomes Golgi complex The potential to have a vacuole Mitochondria Cytoskeleton
List the features that a prokaryotic cell has where a eukaryote does not.
Cell Wall
Circular DNA/RNA strand
Flagellum
What are the 4 levels of structure of the nucleus in a eukaryotic cell?
Nucleotides
DNA
Chromatin
Nucleusow are monomeric units joined?
How are monomeric units joined together and what do they form when they join?
They are joined by covalent bonds to form macromolecules
How are macromolecules held together?
Non-covalent interaction
What is a hydrogen bond?
A bond that forms between a hydrogen atom bound to an electronegative atom and another electronegative atom.
What is an ionic interaction?
Attraction or repulsion between ions.
What does solubility depend on?
Ability to form hydrogen bonds
What are hydrophobic interactions?
Non polar interactions i.e. they do not interact with water
When do Van der Waals interactions occur?
When two atoms are in close proximity.
Define hydrophobic
When a molecule will not interact with water and can pass through lipid bilayers.
Define hydrophillic
Polar. They interact with water and cannot pass through lipid bilayers unassisted
Define amphipathic
When a molecule has both a hydrophilic (polar) and a hydrophobic (non polar) end
What is an alpha helix?
a type of regular protein secondary structure. It is a right handed helix with 3.6 residues per turn.
What is a beta sheet?
A secondary structure of a protein where the polypeptide chains are in an extended conformation.
What is a micelle?
A sphere of amphipathic molecules with hydrophobic parts are on the inside away from water and the hydrophilic heads face outwards, interacting with water.
Define pH
A measurement of the concentration of H+ ions in a solution.
How does the dissociation of strong acids in water differ to that of weak acids?
Strong acids (and bases) dissociate completely in solution whereas weak ones only partly dissociate.
What is pK
The tendency of an acid to dissociate.
If the pK value is low, what does this mean?
That the acid is more likely to dissociate in solution.
What is a buffer a mixture of?
A weak acid and its conjugate base.
What do buffers do?
Resist pH changes
When pH > pK ….
the deprotonated form dominates
When pH < pK …
the protonated form dominates.
When pH = pK …
There is an equal amount of acid and its conjugate base
How do you calculate pH from pK?
pH = pK + log([A-]/[HA])
What is the structure of a simple amino acid?
alpha-C in centre with 4 groups;
- R group
- H group
- COOH group
- NH2 group
Which group on the C are amino acids classified by?
Their R group
Amino acids are classified on 3 levels. What are these?
- Non polar / polar
- Aromatic / Aliphatic
- Positive / Negative charge
What is a zwitterion?
A neutral molecule that has positive and negative charge
What is pI?
The isoelectric point. The pH at which the protein has no overall charge.
If pI is lower than 7, what does this say about the protein?
It is acidic and it contains many negatively charged amino acids.
Name 4 biological reasons why proteins are important.
Enzymes (catalysts) Transporters Structural support (collagens) Machines (muscle contraction) Immune protection (immunoglobulins) Ion channels Receptors (hormones, neurotransmitters) Ligands in cell signalling (growth factors)
How does a peptide bond form?
Dehydration reaction (condensation)
Bond forms between the Carboxyl group of one amino acid and the Amino group of the second.
- No rotation about the peptide bond
- All atoms in the same plane (horizontally drawn)
- Carbonyl Oxygen and amide hydrogen are in the trans orientation
Name the charged amino acids and note their charge.
Glutamate & Aspartate (positive)
Histidine, Arginine, Lysine (negative)
What are the four levels of protein structure?
Primary
Secondary
Tertiary
Quarternary
What is the primary structure?
The amino acid sequence
What is the secondary structure? Name the two conformations and state the bond type involved.
Local spatial arrangement of the polypeptide backbone (alpha helix or beta sheet). Bonds on either side of the peptide bond can rotate freely and when the angles remain the same, a regular secondary structure is adopted. Hydrogen bonds maintain this structure.
What is the tertiary structure?
The 3D structure of the protein by folding of secondary structure.
What is a domain?
Regions of the polypeptide that have distinct structures and often serve particular roles.
What is a motif?
Folding patterns containing 1 or more secondary structure elements.
What is the quarternary structure?
Interaction between different polypeptide subunits within the same protein.
