Patient Semester 1 Flashcards
(122 cards)
1
Q
What is the diameter of a prokaryotic cell?
A
1-5um
2
Q
What is the diameter of a eukaryotic cell?
A
10-100um
3
Q
What is the thickness of a membrane?
A
6-10nm
4
Q
Define amphipathic.
A
Both hydrophilic and hydrophobic
5
Q
What is the glycocalyx?
A
The layer of carbohydrate on a cell membrane
6
Q
What three methods are used to move small molecules?
A
Simple diffusion
Facilitated diffusion
Active transport
7
Q
What is the diameter of an LDL molecule?
A
22nm
8
Q
What is the diameter of an HDL molecule?
A
7-12nm
9
Q
By what method are large molecules transported across membranes?
A
Vesiculation
10
Q
What are the three types of lipid?
A
Simple- made up of glycerol and fatty acids
Complex- other groups such as sugars or phosphates attached
Sterols- heterocyclic
11
Q
What is the width of a DNA alpha helix?
A
2nm
12
Q
What is the length of one turn in a DNA alpha helix?
A
3-4nm
10 base pairs
13
Q
In what direction are nucleic acids written?
A
5’ to 3’
14
Q
What does antiparallel mean?
A
Moving in opposite directions
15
Q
At what rate does DNA replication occur?
A
Occurs at approximately 1000 bases per second
16
Q
What do topoisomerases do?
A
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
17
Q
What is the leading strand?
A
It is the strand of DNA that is made continuously, moving toward the 3’ end and the replication fork
18
Q
What is the lagging strand?
A
The strand of DNA which is made in short fragments which are subsequently joined together
19
Q
What primes DNA synthesis?
A
A short strand of RNA with a free 3’OH group produced by primase
20
Q
When complete, what enzyme removes the RNA primer?
A
DNA polymerase I
21
Q
What antibiotics inhibit bacterial DNA gyrases and topoisomerase IV?
A
Fluoroquinolones
22
Q
Which antibiotic preferentially inhibits bacterial RNA polymerase?
A
Rifampicin
23
Q
Which viruses make DNA from RNA? Using what enzyme?
A
HIV and HSV using reverse transcriptase
24
Q
What is removed from pre mRNA using spliceosomes?
A
Introns
25
What is mRNA used for?
Sends a nucleotide message from the nucleus to the ribosomes
26
What is tRNA used for?
Transferring amino acids to polypeptides during protein synthesis
27
What is rRNA used for?
It forms the major components of the ribosomal subunits
28
What type of ribosomes are present in prokaryotic and eukaryotic cells?
Prokaryotic- 70S (50s + 30S)
| Eukaryotic- 80S (60s + 40s)
29
In what direction does the coding strand run?
5' to 3'
30
In what direction does the template strand run?
3' to 5'
31
What does RNA polymerase do?
Unwinds DNA helices
32
What stops RNA polymerase
When it reaches a downstream termination sequence
33
What is a sequence of 3 bases known as?
A codon
34
How many start and stop codons are there?
1 start codon and 3 stop codons
35
What is the genetic code?
The relationship between the sequence of bases on mRNA and sequence of amino acids in a protein
36
What does degenerate mean?
A single amino acid may have more than one codon
37
Where does protein synthesis occur?
The ribosomes
38
What are ribozymes?
Catalytic RNA
39
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
40
How many sites within a ribosome are occupied at any one time?
Only two
41
What is the A site of a ribosome?
Aminoacyl acceptor site (point of entry)
42
What is the P site of a ribosome?
Peptidyl site (point of bond formation)
43
What is the E site of a ribosome?
The exit site
44
What is translocation?
Peptide chain enters the P site of the ribosome, unloaded tRNA moves to the E site, leaving the A site empty
45
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
46
Which antibiotics preferentially bind to prokaryotic ribosomal RNAs and proteins?
Tetracycline
Chloramphenicol
Erythromycin
47
Define proteomics.
The large scale study of proteins, in particular their structure, function and modifications
48
What is lipidation?
Method of localising proteins in membranes by increasing its hydrophobicity
49
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
50
How does glycosylation affect proteins?
It affects protein folding, distribution, stability and activity
51
What is the purpose of acetylation on histone proteins?
At the amine group of lysine residues, acetylation can help to control gene expression
52
What is a first order reaction?
When the reaction rate is not dependent on the concentration of the reactants
53
What is a second order reaction?
Where the rate is dependent on the concentration of one reactant
54
What is a third order reaction?
Where the rate is dependent on the concentration of two reactants
55
What sign should Gibbs Free Energy have in order for the product to form?
Negative
56
What is the Michaelis complex?
Complex formed between enzyme and substrate
57
What is the Michaelis constant?
Km = (rate of backwards reaction + rate of production of product) / rate of forwards reaction
58
What is the equation for initial rate of reaction?
Vo= Vmax x [So] / Km + [So]
59
What is competitive inhibition?
Substrate and inhibitor compete for the active site
60
What is uncompetitive inhibition?
Inhibitor binds in the active site altering its shape
61
What is non competitive inhibition?
Inhibitor binds away from the active site, altering its shape
62
What is the diameter of the nucleus?
6um
63
What percentage of the cell volume does the nucleus account for?
10%
64
What does the nuclear envelope do?
Encloses chromatin
65
How big is a nuclear pore?
120nm diameter
| 35nm thick
66
How big is an active nuclear pore?
20nm
67
How big is a passive pore?
9nm
68
How many pores are there in a nucleus?
4000
69
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
70
What percentage of nuclear volume does fibrous chromatin occupy?
80-90%
71
What is nucleoplasm?
Amorphous fluid containing soluble components such as proteins and RNA
72
What is the nucleolus?
Dark stained region
| Where ribosomal sub units are assembled
73
What is the nuclear matrix?
Insoluble, fibrous structure that retains the shape of the nucleus
74
What is the nuclear lamina?
The region underneath the inner membrane
75
From where to where do vesicles travel within a cell?
From the endoplasmic reticulum to the Golgi body
76
What is the main difference between RER and SER?
RER- covered in ribosomes for protein synthesis
| SER- more tubular for lipid and drug metabolism
77
What is transitional endoplasmic reticulum?
Part way between RER and SER
78
What organelle deals with detoxification of drugs?
SER
79
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
80
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.
81
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.
82
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
83
Which organelle is concaved and polar?
The Golgi body
| Polarised- direction of flow
84
What are the Golgi body lumen known as?
Cisternae
85
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
86
What name is given to a protein with a fatty acid chain attached?
Lipoprotein
87
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
88
Where does protein sorting occur?
Trans Golgi Network
89
What are the three compartments in the trans Golgi network?
Cis
Medial
Trans
90
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.
91
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
92
What is regulated secretion in the Golgi body?
Receptor mediated exocytosis
93
Where does polysaccharide synthesis occur?
The Golgi body
94
What are the features of a lysosome?
50-500nm in diameter
High specialised membranes
Contain many acid hydrolases
PH 4.5
95
What is endocytosis?
Receptor mediated mechanism for engulfing foreign microbes and internalising specific extra cellular molecules
96
What is autophagy?
Selective destruction and recycling of worn out organelles by wrapping them in smooth ER membrane for digestion
97
What are the four functions of lysosomes?
Endocytosis
Autophagy
Apoptosis
Extra cellular digestion
98
What is apoptosis/autolysis?
Self determined destruction of a cell
99
What is extra cellular digestion?
Lysosomal enzyme release following trauma- localised inflammation
100
Define catabolic.
Obtaining energy by breaking down nutrients (glucose)
101
Define anabolic.
Production of new cell components through processes that require energy, producing energy via synthesis processes
102
What features do mitochondria have?
1 micron in diameter
Double membrane
Highly folded inner membrane
Contains 70s ribosomes
103
What functions occur in the mitochondria?
ATP generation
| Fatty acid oxidation, Krebs cycle, oxidative phosphorylation
104
What are the features of a mitochondrial outer membrane?
Contains porin, channel forming protein
| Permeable to molecules with a molecular weight below 10000
105
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
106
What are the features of the inner membrane of mitochondria?
Large surface area
75% protein
High permeable to ions
107
What is the main feature of the mitochondrial matrix?
Alkaline pH for removal of protons
108
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
```
109
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.
110
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.
111
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
112
What are microtubules responsible for?
Movement of organelles and vesicles
113
What are the three types of motor protein?
Myosins
Kinesins
Dyneins
114
What is the diameter of a microtubule?
25nm
115
What is tubulin?
A dimer made up of alpha and beta units that forms microtubules
116
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.
117
What are axonemal microtubule structures?
Complex structures formed from microtubule bundles such as flagella
118
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
```
119
What is the diameter of an action filament?
6nm
120
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
121
What is the diameter of an intermediate filament?
10-15um
122
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
