BioMed Flashcards
1
Q
Structure of a standard eukaryotic cell
A
> diverse in shape, structure and function
> Plasma membrane
> Nucleus
> Mitochondria
> Internal membrane bound organelles
2
Q
Describe structure and function of cytoskeleton
A
> Helps cells maintain their shape and internal structures
> Provides mechanical support that lets cells carry out division and movement
3
Q
Difference between prokaryotes and eukaryotes
A
> Prokaryotes: no nucleus, contains plasmids, usually unicellular, about 1-10 micrometers
> Eukaryotes: contains nucleus, usually multicellular, 10-100 micrometers
4
Q
Primary structure of protein
A
Sequence of amino acids
5
Q
Secondary structure of protein
A
Folding; alpha helix and beta pleated sheet
6
Q
Tertiary structure of protein
A
3D shape; Defined by the hydrophilic and hydrophobic interactions between R groups of amino acid chains.
di-sulphide bridges
7
Q
quaternary structure of a protein
A
A number of polypeptide chains linked together, and sometimes associated with non-protein groups to form a protein.
8
Q
What is the action of oxidoreductases? Examples?
A
Reduction and oxidation reactions
Examples:
Dehydrogenase
Oxidase
9
Q
What is the action of Transferases? Examples?
A
Transfer of amino, carboxyl, acyl, carbonyl, methyl, phosphate
Examples:
Transaminase
aldolase
10
Q
What is the action of hydrolyses? Examples?
A
Change of bonds coupled with inserting water
Examples:
Esterase
Peptidase
11
Q
What is the action of lyases? Examples?
A
Cleavage of C-C, C-S, C-N but not peptide bonds
Examples:
Decarboxylase
Aldolase
12
Q
What is the action of isomerases? Examples?
A
Rearrangement of bonds
Examples:
Epimerase
Mutase
13
Q
What is the action of ligases? Examples?
A
Formation of bonds between carbon and oxygen, sulphur, and nitrogen
Examples:
Synthetase
Carboxylase
14
Q
What is Km? What does low km mean? high?
A
> the michealis constant
> Enzyme binds to the substrate tightly and works fast even at a low substrate concentration
> Enzyme binds to substrate weakly and requires a high concentration of substrate to work fast
15
Q
What is Vmax?
A
Maximum possible rate of reaction
16
Q
What are allosteric regulators
A
Bind to a regulatory site other than the active site and changes the enzyme activity by altering the proteins tertiary or quaternary structure
17
Q
What are the 6 ways you can regulate enzyme activity
A
> feedback loops (short term)
> Feed forward activation (short term)
> allosteric regulation (short term)
> phosphorylation-dephosphorylation sequence (short term)..aka post-translational modification
> proteolysis (long term)
> Changes in gene expression (long term)
18
Q
What enzyme does phosphorylation require? dephosphorylation?
A
> Kinase
> Phosphotases
19
Q
What do irreversible inhibitors do?
A
Form covalent bonds
20
Q
What happens to km and Vmax in competitive inhibitors
A
Km= increases
Vmax=unchanged
> More substrate required to saturate enzyme
21
Q
What happens to km and Vmax in non-competitive inhibitors
A
km=unchanged
Vmax=decreases
22
Q
What is an isoenzyme
A
Different enzymes the catalyze the same reaction but are subject to different regulatory controls (ex: DAHP synthase for aromatic amino acids)
23
Q
mnemonic to remember classes of enzymes?
A
Over The Hills Live Intelligent Ladies
Oxidoreductases, Transferases, Hydrolyses, Lyases, Isomerases, Ligases
24
Q
3 main uses of lipids
A
> storage of energy
> forming membranes
> signalling between and within cells
25
What are the two essential fatty acids?
linoleic acid and linolenic acid
>must be taken in from the diet
26
What does the delta sign mean when naming fatty acids? Omega sign? What does the first number mean? The second?
>delta=where double bonds are in relation to the carboxylic end
>Omega= where the double bonds are in relation to the omega end
>1st number=number of carbons
>2nd number=number of double bonds
27
What is the other name for a triglyceride? describe it
>Triacylglycerol
>3 fatty acids join onto a glycerol molecule in the formation of an ester bond
>Main storage form of lipids found in adipose tissue surrounding visceral organs and subcutaneous fat
28
What are the two types of phospholipids? Give an example of each
>Glycerophospholipids
>Example:Phosphatidylserine
>Sphingolipids
>Example:Sphingomyelin
29
What is cholesterol based on and what does it do?
>Based on steroid structure
| >Decreases membrane fluidity as it packs between other lipids
30
Name four lipid derivatives
>Vitamin D
>Steroid hormones
>Bile salts
>Eiosanoids
31
Describe vitamin D
>Synthesised from 7-dehydricholesterol by sunlight
| >Required for calcium absorption and bone formation
32
Describe steroid hormones and give three examples
>derived from cholesterol
| >cortisol, oestrogen, progesterone
33
Describe bile salts
>synthesised from cholesterol in the liver
| >secreted from the duodenum to aid absorption of dietary fats
34
Describe eiosanoids and give two examples
>derived from arachidonic acid
>Involved in inflammation response and vascular contraction
>prostaglandins and thromboxanes
35
3 main uses of a carbohydrate
>energy storage
>structure
>recognition and adhesion
36
What do monosaccharides consist of
aldehyde or ketones and at least two alcohol groups
37
What is the structure of an aldehyde?Ketone?
>double bonded oxygen and a hydrogen and an r group (on end)
| >Double bonded oxygen with two r groups (in the middle)
38
What are the 3 monosaccharides?
glucose, fructose & ribose
39
What is sucrose broken down into? by what enzyme?Lactose?Maltose?
>glucose & fructose by sucrase
>Glucose & galactose by lactase
>glucose & glucose by maltase
40
What are glycosaminoglycans? what is their role
>large negatively charged heteropolysaccharides
| >roles in the extracellular matrix, acting as lubricants and shock absorbers
41
What are the four types of phospholipid movements in the membrane?
>lateral diffusion
>flexion(movement/bending of tail)
>rotation(turning around of tail)
>flip-flop(rarely occurs-only with help of flippase enzyme, its when they swap from top layer to bottom layer/vice versa)
42
Give some examples of small non-polar molecules and how they cross the membrane
>Cross by simple diffusion
| >O2,CO2,N2,steroid hormones
43
Give some examples of small uncharged polar molecules and how they cross the membrane
>Can diffuse but not as easily as small non-polar molecules
| >H2O, ethanol, glycerol
44
Can ions diffuse across the membrane?
no
45
What do transporters allow
Active or passive diffusion
46
What are the two types of active transport and what are they driven by
Primary active transport driven by ATP
| Secondary active transport driven by co-transport of Na+
47
What do channels allow for? What type of gated are they
facilitated diffusion
| ligand-gated or voltage-gated
48
Where are ligand-gated ion channels found? what else are they called
>Found at neuromuscular junctions
| >Ionotropic receptors or ion-channeled coupled receptors
49
What do G-protein coupled receptors include?
```
Receptors for:
adrenaline
glucagon
odour molecules
acetylcholine
rhodopsin (photoreceptor in retina)
```
50
Explain what happens in a g-protein coupled receptor
>Ligand binding site causes activation of associated g protein
>activated G protein stimulates enzymes that produce second messages (cAMP)
>Causes signal amplification
51
What is anabolic? catabolic?
>where the body builds and repairs muscle tissue
| >where the body breaks down the tissue to replenish depleted energy levels
52
When does a reaction occur spontaneously?
when Gibbs free energy is negative
53
What is Gibbs free energy measured in?
in kJ/mol
54
What food molecules are oxidised to release energy?
carbon-based food molecules
55
What are activated carriers
biomolecules that store energy in the form of transferrable chemical groups
56
What is NADP+ usually used in
Anabolic pathways
57
What usually happens to FAD
usually covalently linked to enzymes and acts as a coenzyme
58
What is the net result of glycolysis & what does it require
2 pyruvate, 2 ATP, 2NADH
| requires 2ATP
59
What is the Krebs cycle also known as & where does it occur
TCA or citric acid cycle
| Occurs in the mitochondrial matrix
60
Net result of Krebs cycle
3NADH, 1FADH2, & 1GTP
61
Name some short term ways to control the metabolism
Binding of allosteric inhibitors to alter enzyme activity
| Covalent modification such as phosphorylation
62
Name some long term ways to control the metabolism
Changes in gene expression to alter total amount of enzymes
| Changes in proteolysis to alter total amount of enzymes
63
Percentage of ECF and ICF in the body
20% ECF
| 40%ICF
64
Conc. of sodium ions in mmol/L in the ECF & ICF? potassium? calcium?
Sodium: ECF:140 ICF:10
Potassium: ECF:4 ICF:120
Calcium: ECF:1.25 ICF:0.0001
65
What are four important internal properties?
>temperature
>pH
>Glucose concentration
>Oxygen levels
66
What is interstitial fluid? Plasma?
>thin layer of fluid which surrounds the bodies cells
| >Colourless fluid part of blood, lymph in which fat globules are suspended
67
Define diffusion and bulk flow
>Net movement down a concentration gradient due to random motion of individual molecules
>Movement of water and solutes together due to a pressure gradient
68
What law describes what happens when gases come into contact with fluids such as blood? Describe it
Henrys law
| >Concentration of a gas in a liquid is directly proportional to the solubility and partial pressure of that gas
69
What are the two equations for pH
pH=-log10[H+]
| pH=pKa+log10[A-]
70
Whats the equation for [H+]
[H+]=10^-pH
71
What is the equation for pKa
pKa=-logKa
72
What are the differences between acids and bases
```
Acids:
Low pH
high conc of H+
release protons
Bases:
High pH
Low conc of H+
Accept protons
```
73
Difference between strong and weak acids
Strong acids almost completely dissociate whereas weak acids only partially dissociate
Strong acids have a low pKa, weak acids have a high pKa
74
What is pKa
The pH at which the acid is half dissociated
75
What does it mean when the pH=pKa
Then [A-]=[HA]
| buffer resists any change (acid or base)
76
What does it mean when pH < pKa
Then [HA]>[A-]
| buffer resists addition of base
77
what does it mean when pH>pKa
Then [HA] < [A-]
78
What is the typical blood pH? when is it considered alkaline? acidosis?
7.4
when it increases above 7.45
when it decreases below 7.35
79
What are osmolyte particles
dissolved particles that determine osmotic pressure
80
What is an osmole
osmole=6 x 10^23 osmolyte particles
81
Define osmolarity & its equation
the number of osmolyte particles per volume of a solution
| osmolarity=sum of molar conc x osmotic coefficient
82
what is the reflection coefficient
degree to which a membrane is permeable to a solute
83
Define hyposmotic, isosmotic, hyperosmotic
>solution contains lower conc. of impermeable solutes than the solution on the other side of the membrane
>solution contains equal conc. of solute either side of the membrane
>solution contains a higher conc. of impermeable solutes than the solution on the other side of the membrane
84
Define tonicity
effect that a solution has on the cell volume
85
what happens in a hypotonic solution? hypertonic?
>results in swelling and haemolysis
| >results in creation or shrinking
86
What is haemolytic
destruction or rupture of red blood cells
87
What does paracrine mean
diffusion of a chemical signal in interstitial fluid to the neighbouring cells
88
what does autocrine mean
cell signals to itself
89
What are the three main types of receptors found on the cell membrane
receptors which are ion channels (ligand-gated)
receptors which are enzymes or directly bound to enzymes
receptors which act via G proteins
90
What does tetrodoxin do
stop action potential
91
What is saltatory conduction
when action potentials jump from one node to the next
| accelerates action potential propagation & save energy
92
What cell is the myelin provided by in the CNS
oligodendrocytes
93
What cell is the myelin provided by in the PNS
Schwann cells
94
What is a resting membrane potential
where ions are distributed asymmetrically across the plasma membrane
95
what does a depolarised membrane mean
allows more cations to enter neurone
| membrane potential decreases (becomes less negative)
96
What is EPSP
excitatory postsynaptic potential
temporary depolarisation of postsynaptic membrane caused by flow of positively charged ions into the postsynaptic cell as a result of opening of ligand-sensitive channels
97
What is IPSP
inhibitory postsynaptic potential
temporary hyperpolarisation of postsynaptic membrane caused by flow of negatively charged ions into the postsynaptic cell
98
What does a hyperpolarised membrane mean
```
allows efflux (flowing out) of cations or influx of anions
membrane potential increases (becomes more negative)
```
99
Four steps in generating an action potential
initiation
upstroke
repolarisation
refractory period
100
What happens in initiation of an action potential
stimulation results in a depolarisation of the membrane potential to a threshold value (between -50 to -60mV)
101
What is summation
the additive effect of several electrical impulses on a neuromuscular junction
102
What is a neuromuscular junction & what happens there
synaptic connection between the terminal end of a motor nerve and a muscle
nerve action potential, calcium entry into the presynaptic terminus, release of Ach quanta, diffusion of Ach across cleft
103
What is the sympathetic nervous system? parasympathetic nervous system?
>fight or flight
| >rest and digest
104
What happens at the extreme in the SNS (sympathetic nervous system)
>heart rate increases
>piloerection (hair stands up)
>salivation in anticipation (Other digestion related things are stopped)
>sweating
>trachea & bronchi dilate (facilitate air flow)
>arterioles redistribute blood for the vital organs
105
What happens at the extreme in the parasympathetic nervous system
>Constriction of pupils
>GI increases
>trachea and bronchi constrict
>decrease in heart rate & force of contraction
106
what are three types of muscle
cardiac
skeletal
smooth
107
Describe cardiac muscle
>generation of blood pressure
>striated structure
>Innervated in the ANS, involuntary
108
Describe skeletal muscle
>voluntary muscle
>striated structure
>Innervated in the PNS, voluntary
109
Describe smooth muscle
>contraction of smooth organs (stomach, blood vessels)
>non-striated structure
>Innervated by ANS, involuntary
110
Function of skeletal muscle
>motor unit=consists of a motor neurone and innervated by muscle fibres
111
How to distinguish if a sample is skeletal muscle
>Has large rod-like fibres
>Has striations
>nuclei at periphery (outer edges)
>Each fibre singly innervated
112
How are fibres activated in the cardiac muscle? How do you measure the force? What is the force per fibre increased by?
>by a spread of action potential
>force=force per fibre x number of fibres
>the sympathetic nervous system (beta 1 receptor) & hormones (thyroxine (T4) works by increasing beta 1 receptor density)
113
How to distinguish if a sample is cardiac muscle
>intercalated discs separate cells
>has one/two nuclei
>has striations
(>cells are connected electrically)
114
What is the force per cell modulated by in smooth muscle?
sympathetic nervous system (alpha or beta)
| parasympathetic nervous system (muscarinic)
115
How to distinguish if a sample is smooth muscle
```
>very small cells
>single nucleus
>no striations
>cells are sometimes connected
>find them in hollow organs
```
116
What is the I band? outer edge of A band? H zone? M line?
>thin (actin) filaments only
>thin (actin) & thick (myosin) filaments overlap
>thick (myosin) filaments only
>thick (myosin) filaments linked by accessory proteins
117
What are EMGs? What are they used for?
Electromyograms
can be used to monitor the levels of activation in the muscle cells in skeletal muscle
(sum of multiple motor unit action potentials (compound action potentials))
118
Whats is the size (amplitude mV) of EMGs dependent on?
>Size of muscle
>Depth of the muscle (distance between skin & muscle)
>resistance between skin and recording electrodes
119
What is the latency (delay) between stimulus and response in EMGs due to?
>Activation time of nerve
>Conduction time in nerve
>Transmission time across the neuromuscular junction
>Conduction time within the muscle fibres
120
Which way should the anode & cathode be placed in an EMG
cathode (negatively charged plate) should be placed nearer the hand than the anode (positively charged plate)
121
define genome
genetic information fo an organism
122
define gene
basic unit of inheritance (region of DNA that encodes for a function)
123
what are the pyrimidines
uracil, thymine, cytosine
124
What are the purines
adenine, guanine
125
What bases pair with 2 bond/3 bonds
2 bonds=adenine & thymine
| 3 bonds=cytosine & guanine
126
define intron
non-coding information
127
define exon
required information(e.g. for protein coding sequence)
128
What is pre-mRNA
introns & exons
129
mRNA
post-splicing only exons
130
What are telomeres
ends of the chromosomes
131
Define pseudogene
a section of a chromosome that is an imperfect copy of a functional gene
132
What is a tandem repeat
occur in DNA when a pattern of one or more nucleotides is repeated and the repetitions are directly adjacent to each other
133
What is an interspersed genome-wide repeat?
identical or nearly identical DNA sequences that are scattered throughout the genome
134
What happens during DNA synthesis
>unzipping pf the double helix by helicase (breaks hydrogen bonds between nucleotide bases)
>strand in 3'-5' (from unzipped end) is leading strand
>strand in 5'-3' is lagging strand
Leading strand:
>Primer (short piece of RNA from enzyme primase) bind to end of leading strand
>DNA polymerase binds to leading strand adding nucleotide bases in 5'-3' direction (opposite of the leading strand)
>called continuous replication
Lagging strand:
>Numerous primers bind at various points
>Okazaki fragments added in 5'-3'
>called discontinuous replication
Both strands:
>exonuclease strips away primers
>DNA ligase seals up sequence
135
What are the four types of DNA mutation
>insertion
>deletion
>double-strand breaks
>point mutations
136
What causes DNA mutations?
```
>Uv light exposure
>cellular metabolism
>Ionising radiation
>chemical exposure
>replication errors
```
137
What are the five repair pathways for DNA mutations?
>Base excision repair (recognises, removes and replaces damaged bases)
>nucleotide excision repair (recognises damaged base, removes & replaces entire nucleotide)
>mismatch excision repair (repairs replication errors made by DNA polymerases)
>direct repair (repairs the damage itself)
>double strand break repair
138
What does UV radiation do in DNA damage
causes thymine to become covalently linked (forms a thymine dimer)
139
What is mRNA
messenger RNA
| copy of protein coding sequence
140
What is rRNA
ribosomal RNA
component of ribosome
(when is acts as an enzyme its called a ribozyme)
141
What is tRNA
transfer RNA
| carries amino acids to ribosome
142
What 3 RNA molecules are used for regulation of gene expression
miRNA
siRNA
lncRNA
143
what is sRNA responsible for
splicing
144
What is snoRNA responsible for
nucleotide modification of tRNA, rRNA
145
What does peptidyl transferase do? what is it?
catalyses the formation of peptide bonds in protein synthesis (its an enzyme)
146
What are the three types of RNA polymerase in eukaryotes and what do they do
I synthesises rRNAs
II synthesises mRNAs
III synthesis tRNAs and 1 rRNA
147
What is the genetic code
(it is universal)
| relationship between the sequences of bases in DNA and the sequence of amino acids in proteins
148
What does tRNA do
reads the genetic code
when an amino acid is attached its called aminoacyl tRNA
`
149
What are the five components needed for protein synthesis
```
>Ribosome subunits
>mRNA
>aminoacyl tRNA
>protein factors
>GTP (guanine triphosphate)
```
150
What are the three stages of protein synthesis
initiation
elongation
termination
151
What happens in initiation of protein synthesis
formation of the 80s initiation complex
| AUG is an initiator codon
152
what happens in elongation of protein synthesis
aminoacyl tRNA enters A site
peptide bond formation
translocation (process that advances the mRNA–tRNA moiety on the ribosome, to allow the next codon to move into the decoding center)
153
What happens in termination of protein synthesis
release factor binds
polypeptidyl-tRNA link hydrolysed
dissociation of compounds
154
What is glycosylasation in protein synthesis
reaction in which a carbohydrate is attached to a hydroxyl or other functional group of another molecule
155
What is phosphorylation in protein synthesis
amino acid residue is phosphorylated by a protein kinase by the addition of a covalently bound phosphate group
156
What is proteolytic processing in protein synthesis
when a protease cleaves (splits/severs) one or more bonds in a target protein to modify its activity
157
What is a homozygote? heterozygote?
Two identical forms of the particular gene
| Two different forms of the particular gene
158
What is a missense mutation
amino acid substitution
159
What is a nonsense mutation
stop codon
160
what is a silent mutation
substitution occurs but codes for the same amino acid
161
What happens in mutations of promotors?
alters levels of transcription
162
What happens in mutations of splicing?
low/no beta globin
163
What happens in mutations in 5'-CAP site
reduced levels of translation
164
What happens in mutations of Poly-A-tail signals
reduced levels of translation
165
Define epigenetic code
defining code in every eukaryotic cell consisting of the specific epigenetic modification in each cell
166
What is a single nucleotide polymorphism (SNP)
is a variation at a single position in a DNA sequence among individuals
167
What are the stages of the cell cycle
```
interphase
prophase
metaphase
anaphase
telophase
cytokineses
```
168
What are the stages in interphase?
G1: (growth) increase supply of proteins, number of organelles (mitochondria and ribosomes)
S:DNA replication
G2: (growth) protein synthesis and rapid cell growth to prep cell for mitosis
169
What happens in prophase
chromosomes visible condense
centromeres migrate to opposite poles
microtubule spindle forms between centrosome and kinetochore
nuclear membrane breaks down
170
what happens during metaphase
chromosomes align along spindle equator
171
What happens during anaphase
sister chromatids pulled apart to opposite poles
| each daughter cell inherits one chromosome copy
172
What happens during telophase
chromosomes de-condense
| nuclear membrane reforms
173
what happens during cytokinesis
membrane cleavage to form two identical daughter cells
174
What regulates the cell cycle? How?
Cyclins
they bind and activate Cdks (Cyclin dependent kinases)
which directly/indirectly regulate expression or function of key proteins required at each stage of the cycle
175
What are the checkpoints in the cell cycle
G1
G2
mitosis
176
What are the steps in meiosis
```
meiosis I:
prophase I
metaphase I
anaphase I
telophase I
meiosis II:
prophase II
metaphase II
anaphaseII
telophaseII
```
177
What happens in the stages of meiosis
PI-chromosomes condense, nuclear membrane dissolves , homologous chromosomes form bivalents, crossing over occurs
MI-spindle fibres from opposing centromeres connect to bivalents (at centromeres) and align hem along middle of cell
AI-spindle fibres contract and pull bivalents apart, homologous chromosomes move to opposite poles
TI-chromosomes decondense, nuclear membrane may reform, cytokinesis occure
PII-Chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles (perpendicular to before)
MII-Spindle fibres from opposing centrosomes attach to chromosomes (at centromere) and align them along the cell equator
AII-Spindle fibres contract and separate the sister chromatids, chromatids (now called chromosomes) move to opposite poles
TII-Chromosomes decondense, nuclear membrane reforms, cells divide (cytokinesis) to form four haploid daughter cells
178
What is a karyotype
number and appearance of chromosomes of a cell
179
What is heterochromatin? euchromatin?
dark bands
| light bands
180
What is anueploidy
abnormal number of (usually 1) chromosome
181
what is a trisomy and which ones are compatible with life
additional chromosome
+18, +21, +13
can also have a trisomy of X
182
What is a monosomy
loss of a chromosome
| only loss of X is viable
183
What is X-inactivation
called lyonisation in females
| forms Barr bodies
184
what is a Barr body
dark staining region in female cells
| condesned inactive X chromosome
185
What is a polygenic disease, give an example
impact of many genes each having limited individual impact (blood pressure)
186
what is a multifactorial disease, give an example
interplay of environmental factors along with multiple genes (cancer, diabetes)
187
what are totipotent stem cells
cells that can form all of the cell types in the body, plus the extra embryonic and placental cells
188
What are pluripotent cells
can only make cells of the embryo proper, but that is all of the cells of the body
189
what are multipotent cells
can only make cells within a certain germ layer and derivatives
190
what are desmosomes
intercellular junctions that provide strong adhesion between cells and act as signalling centres
191
what are tight junctions
they seal neighbouring cells in epithelial sheets to prevent leakage of molecules between cells
192
What is necrosis
external injury
the cell swells and bursts spilling its contents over its neighbouring cells and invoking an inflammatory response that can be damaging
193
what is apoptosis
programmed physiological cell death which by the cell dies neatly
