Patient Semester 1 Flashcards
What is the diameter of a prokaryotic cell?
1-5um
What is the diameter of a eukaryotic cell?
10-100um
What is the thickness of a membrane?
6-10nm
Define amphipathic.
Both hydrophilic and hydrophobic
What is the glycocalyx?
The layer of carbohydrate on a cell membrane
What three methods are used to move small molecules?
Simple diffusion
Facilitated diffusion
Active transport
What is the diameter of an LDL molecule?
22nm
What is the diameter of an HDL molecule?
7-12nm
By what method are large molecules transported across membranes?
Vesiculation
What are the three types of lipid?
Simple- made up of glycerol and fatty acids
Complex- other groups such as sugars or phosphates attached
Sterols- heterocyclic
What is the width of a DNA alpha helix?
2nm
What is the length of one turn in a DNA alpha helix?
3-4nm
10 base pairs
In what direction are nucleic acids written?
5’ to 3’
What does antiparallel mean?
Moving in opposite directions
At what rate does DNA replication occur?
Occurs at approximately 1000 bases per second
What do topoisomerases do?
Type I- cuts one DNA strand, relaxation occurs, the strand is then reattached
Type II- cute both DNA strands, passes another unbroken helix through it and then rejoins the strands
What is the leading strand?
It is the strand of DNA that is made continuously, moving toward the 3’ end and the replication fork
What is the lagging strand?
The strand of DNA which is made in short fragments which are subsequently joined together
What primes DNA synthesis?
A short strand of RNA with a free 3’OH group produced by primase
When complete, what enzyme removes the RNA primer?
DNA polymerase I
What antibiotics inhibit bacterial DNA gyrases and topoisomerase IV?
Fluoroquinolones
Which antibiotic preferentially inhibits bacterial RNA polymerase?
Rifampicin
Which viruses make DNA from RNA? Using what enzyme?
HIV and HSV using reverse transcriptase
What is removed from pre mRNA using spliceosomes?
Introns
What is mRNA used for?
Sends a nucleotide message from the nucleus to the ribosomes
What is tRNA used for?
Transferring amino acids to polypeptides during protein synthesis
What is rRNA used for?
It forms the major components of the ribosomal subunits
What type of ribosomes are present in prokaryotic and eukaryotic cells?
Prokaryotic- 70S (50s + 30S)
Eukaryotic- 80S (60s + 40s)
In what direction does the coding strand run?
5’ to 3’
In what direction does the template strand run?
3’ to 5’
What does RNA polymerase do?
Unwinds DNA helices
What stops RNA polymerase
When it reaches a downstream termination sequence
What is a sequence of 3 bases known as?
A codon
How many start and stop codons are there?
1 start codon and 3 stop codons
What is the genetic code?
The relationship between the sequence of bases on mRNA and sequence of amino acids in a protein
What does degenerate mean?
A single amino acid may have more than one codon
Where does protein synthesis occur?
The ribosomes
What are ribozymes?
Catalytic RNA
How does a ribosomes form in initiation?
The small subunit complexes with initiation factors
Base pairing occurs between rRNA and a special sequence on mRNA
Start codon is positioned in the P site
The large subunit joins, GTP is hydrolysed and initiation factors leave the ribosome
How many sites within a ribosome are occupied at any one time?
Only two
What is the A site of a ribosome?
Aminoacyl acceptor site (point of entry)
What is the P site of a ribosome?
Peptidyl site (point of bond formation)
What is the E site of a ribosome?
The exit site
What is translocation?
Peptide chain enters the P site of the ribosome, unloaded tRNA moves to the E site, leaving the A site empty
How does termination occur?
Synthesis occurs until a stop codon is reached
A release factor binds in the A site
The polypeptide in the P site is hydrolysed from its tRNA and leaves the ribosome
Which antibiotics preferentially bind to prokaryotic ribosomal RNAs and proteins?
Tetracycline
Chloramphenicol
Erythromycin
Define proteomics.
The large scale study of proteins, in particular their structure, function and modifications
What is lipidation?
Method of localising proteins in membranes by increasing its hydrophobicity
What is phosphorylation? Which three residues does it principally occur on?
Addition of phosphate groups by kinases
Onto serine, threonine and tyrosine (OH side chain) residues
How does glycosylation affect proteins?
It affects protein folding, distribution, stability and activity
What is the purpose of acetylation on histone proteins?
At the amine group of lysine residues, acetylation can help to control gene expression
What is a first order reaction?
When the reaction rate is not dependent on the concentration of the reactants
What is a second order reaction?
Where the rate is dependent on the concentration of one reactant
What is a third order reaction?
Where the rate is dependent on the concentration of two reactants
What sign should Gibbs Free Energy have in order for the product to form?
Negative
What is the Michaelis complex?
Complex formed between enzyme and substrate
What is the Michaelis constant?
Km = (rate of backwards reaction + rate of production of product) / rate of forwards reaction
What is the equation for initial rate of reaction?
Vo= Vmax x [So] / Km + [So]
What is competitive inhibition?
Substrate and inhibitor compete for the active site
What is uncompetitive inhibition?
Inhibitor binds in the active site altering its shape
What is non competitive inhibition?
Inhibitor binds away from the active site, altering its shape
What is the diameter of the nucleus?
6um
What percentage of the cell volume does the nucleus account for?
10%
What does the nuclear envelope do?
Encloses chromatin
How big is a nuclear pore?
120nm diameter
35nm thick
How big is an active nuclear pore?
20nm
How big is a passive pore?
9nm
How many pores are there in a nucleus?
4000
What import and export do nuclear pores allow?
Import of proteins with nuclear import signals- usually basic N-terminal sequence rich in lysine and arginine
Export of RNA molecules and ribosomal sub units
What percentage of nuclear volume does fibrous chromatin occupy?
80-90%
What is nucleoplasm?
Amorphous fluid containing soluble components such as proteins and RNA
What is the nucleolus?
Dark stained region
Where ribosomal sub units are assembled
What is the nuclear matrix?
Insoluble, fibrous structure that retains the shape of the nucleus
What is the nuclear lamina?
The region underneath the inner membrane
From where to where do vesicles travel within a cell?
From the endoplasmic reticulum to the Golgi body
What is the main difference between RER and SER?
RER- covered in ribosomes for protein synthesis
SER- more tubular for lipid and drug metabolism
What is transitional endoplasmic reticulum?
Part way between RER and SER
What organelle deals with detoxification of drugs?
SER
What is required for detoxification of drugs?
Numerous enzymes that deal with foreign substances, in order to render them harmless by oxidation, such as cytochrome P450
What is translocation?
Ribosomes containing mRNA attach to the membrane of RER, and a signal recognition particle allows the translocon channel to open, causing the peptide chain to be translated and enter the lumen of the ER. Where the signal peptides enzyme removes the RNA primer from the peptide chain.
Where does N linked glycosylation occur? And what is it?
It occurs in the endoplasmic reticulum and is the process of adding branched sugar chains to the N group of Asparagine residues.
Where and how does the assembly of lipid bilayers occur?
In the ER, lipid synthesis only adds to the cytosolic side, specific flippase proteins catalyse the flipping of selected lipid molecules
Which organelle is concaved and polar?
The Golgi body
Polarised- direction of flow
What are the Golgi body lumen known as?
Cisternae
Where does O linked glycosylation occurs? And what is it?
Golgi body, sugars attach to the O of the side chains of serine and threonine residues to give proteoglycans
What name is given to a protein with a fatty acid chain attached?
Lipoprotein
How are polypeptide hormones and neurotransmitters formed?
Synthesised in the Golgi body as inactive precursor molecules from which the active form is liberated by proteolysis using endopeptidases
Where does protein sorting occur?
Trans Golgi Network
What are the three compartments in the trans Golgi network?
Cis
Medial
Trans
What is the secretory pathway in the Golgi body?
Lysosomes are used for intracellular digestion which contain over 40 different hydrolysis enzymes giving them a pH of 5.
What is consecutive secretion in the Golgi body?
Transport vesicles designed for immediate fusion with the plasma membrane leave the Golgi in a steady stream, carrying proteins, lipids, proteoglycans etc.
The vesicles membranes also carry plasma membrane integral proteins
What is regulated secretion in the Golgi body?
Receptor mediated exocytosis
Where does polysaccharide synthesis occur?
The Golgi body
What are the features of a lysosome?
50-500nm in diameter
High specialised membranes
Contain many acid hydrolases
PH 4.5
What is endocytosis?
Receptor mediated mechanism for engulfing foreign microbes and internalising specific extra cellular molecules
What is autophagy?
Selective destruction and recycling of worn out organelles by wrapping them in smooth ER membrane for digestion
What are the four functions of lysosomes?
Endocytosis
Autophagy
Apoptosis
Extra cellular digestion
What is apoptosis/autolysis?
Self determined destruction of a cell
What is extra cellular digestion?
Lysosomal enzyme release following trauma- localised inflammation
Define catabolic.
Obtaining energy by breaking down nutrients (glucose)
Define anabolic.
Production of new cell components through processes that require energy, producing energy via synthesis processes
What features do mitochondria have?
1 micron in diameter
Double membrane
Highly folded inner membrane
Contains 70s ribosomes
What functions occur in the mitochondria?
ATP generation
Fatty acid oxidation, Krebs cycle, oxidative phosphorylation
What are the features of a mitochondrial outer membrane?
Contains porin, channel forming protein
Permeable to molecules with a molecular weight below 10000
What are the features of the inter membrane space in mitochondria?
Roughly equivalent to cytosol, pH 7
Many enzymes that use the ATP passing out of the matrix
What are the features of the inner membrane of mitochondria?
Large surface area
75% protein
High permeable to ions
What is the main feature of the mitochondrial matrix?
Alkaline pH for removal of protons
Describe glycolysis.
1x glucose -> 2x pyruvate Produces biosynthetically useful intermediates such as folic Occurs in cytosol Net production of 2x ATP Coenzyme production is 2x NADH
How are lipids metabolised?
Lipids are stored as triglycerides and when broken down the glycerol can be used in glycolysis.
Fatty acyl coA chains are broken down using a coA enzyme to produce acetyl coA and another (shorter) fatty acyl coA chains beta oxidation.
What is oxidative phosphorylation?
Occurs in the inner membrane of mitochondria. An NADH Hydrogenase molecule in the membrane removes protons and electrons from the NADH molecules produced. Protons travel down a concentration gradient through an ATP Synthase molecule in the membrane. The enzyme spins, releasing ATP.
Where are actin filaments in a cell and what do they do?
Anchored just below the plasma membrane and are responsible for changing the shape of the cell by contracting or relaxing
What are microtubules responsible for?
Movement of organelles and vesicles
What are the three types of motor protein?
Myosins
Kinesins
Dyneins
What is the diameter of a microtubule?
25nm
What is tubulin?
A dimer made up of alpha and beta units that forms microtubules
How does a microtubule form?
Protofilaments are arranged in a tube with a hollow core, they stick together at an angle of 160 degrees allowing it to curve into a tube.
What are axonemal microtubule structures?
Complex structures formed from microtubule bundles such as flagella
What are the differences between cilia and flagella?
Cilia- 5-10um length Present in large numbers Complex biphasic movement Flagella- up to 150um length Few in number Wave of motion propels cell
What is the diameter of an action filament?
6nm
What are the features of an action filament?
One end is often attached to the plasma membrane
Solid filaments extend throughout the cell
Important in whole cell movement
What is the diameter of an intermediate filament?
10-15um
What are the features of intermediate filaments?
Found only in animal cells
Size varies depending on the protein
Composed of fibrous proteins
Structural/tension bearing role