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biophysics > Exam practise > Flashcards

Exam practise Flashcards

1
Q

the study of control and
connections in nature, science, and
society is…..

A

Cybernetics

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2
Q

Basic concepts:
Organization (systems theory)
Information (information theory)
Control (control theory) relate to….

A

Cybernetics

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3
Q 
the study of systems in
general, with the goal of elucidating principles
that can be applied to:
 all types of systems
 at all nesting levels
 in all fields of research relates to
A

systems theory

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4
Q

Formation of systems is….

A

Organisation

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5
Q

• interacting structures and processes combined
for the execution of a common function
• which function is different from functions of
the separate components relates to….

A

Cybernetics

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6
Q

Which systems have the following properties:
• Interact with the environment and with other
systems — connections
• Have hierarchical structure:
consist of subsystems
are subsystems of other systems
• Preserve their general structure in changing
environmental conditions

A

Cybernetic systems

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7
Q

Which systems can be characterized using these three types of
functions describing the changes of system:
• component states
• structure and connections
• transmitted signals

A

Cybernetic systems

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8
Q

components interact in a predetermined way

and response is predictable

A

Deterministic systems- example machine

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9
Q

response can not be predicted exactly

A

Probabilistic systems- example weahter

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10
Q
  • the components interact with each other only

* no interactions with the environment

A

Closed systems

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11
Q

the components interact with the

environment as well

A

Open systems

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12
Q

What can be used for Perception of signals from other systems using
sensors?

A

Receptors(eyes, ears, ect)

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13
Q

What is used for Transmission of signals to other systems?

A

Effectors(organs of speech, gestures ect)

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14
Q

Which cybernetic systems have the following properties:
• varying complexity
• probabilistic
• multi-level hierarchical organization

A

Biological cybernetic systems

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15
Q

Complexity of biological systems

A

very complex

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16
Q

Determinism of biological systems

A

Probabilistic

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17
Q

Biological systems organisation

A

Complex two way hierarchy

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18
Q
  • Each component can
    be regarded as a system of lower-level components
    • The low level components perform independently
    of the higher level components as long as they are able to process all the important input information
    • The high level components control the lower level
    components
A

Complex two way hierarchy

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19
Q

• Any set of related data
• Any meaningful event, which results in an
action
• The state of a system of interest

A

information

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20
Q

…….. reduces ambiguity, removes the

lack of knowledge

A

Information

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21
Q

The transmitted information

A

Message

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22
Q

The physical carrier of the message

A

Signal

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23
Q

The medium in

which the signal propagates

A

communication channel

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24
Q

a set of simple signals which can be

used to send any message

A

Alphabet

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25
Q

generation (using
an alphabet) of a signal which carries the
message

A

Encoding

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26
Q

altering the alphabet

A

Recoding

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27
Q

extraction of the

message from the signal

A

Decoding

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28
Q

physically different signals

which carry the same message

A

lsomorphic signals

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29
Q

communication system disturbances

which modify the signal

A

Noise

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30
Q

The ability of a system to store and
retain information, and to recall it for use at a
later moment

A

Memory

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31
Q

Ways to memorise information

A

• by changing the states of system components
• by changing the structure of the system (the
connections between its components)

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32
Q

Unit of measurement for information is…

A

The bit

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33
Q

DNA contains …..bases. Any
nucleotide contains only one base. Therefore, the information carried by one nucleotide is 2
bits.

A

4 bases

2 bits

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34
Q

The chromosomal DNA of one human sperm contains ….. nucleotides, i.e. information of 2.109 bits.

A

10^9 nucleotides

2.10^9

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35
Q

actions effecting a system and aimed at reaching a specific goal

A

Control

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36
Q

control for maintaining a specific state or process

A

regulation

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37
Q

is self contained in its performance monitoring and

correction capabilities

A

Cybernetic Control System

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38
Q

the set of rules (algorithm) used to

control a system

A

Program

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39
Q

the law describing how the controlled system must behave

A

Reference

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40
Q

processes information, generates and sends control messages (commands)

A

Controlling subsystem

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41
Q

changes according to

the messages received

A

Controlled subsystem

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42
Q

communication subsystems

transferring information between the controlling and controlled subsystems

A

Connections

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43
Q

• The execution of the control messages is not monitored
• Used if noise is missing and the properties of the
controlled system do not
change

A

Open loop control

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44
Q

Forward-coupling connection
—transmits control messages from the controlling to the
controlled subsystem

A

Open loop control

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45
Q

The execution of the control
messages is monitored
• Used if noise is present and/or the properties of the controlled system change

A

Closed Loop control

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46
Q

Back-coupling connection
(feedback)—transmits data
messages from the controlled to
the controlling subsystem

A

Closed loop control

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47
Q

Transform the stimulus into excitation

A

receptors

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48
Q

Back-coupling (feedback) channel

A

Afferent (sensory) neurons

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49
Q

Controlling subsystem (issues commands)

A

Neural centre

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50
Q

Forward-coupling channel

A

Efferent (motor) neurons

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51
Q

Respond to the commands

A

Effectors

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52
Q

the control results in increased divergence of the

controlled subsystem

A

Positive feedback (self-reinforcing loop)

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53
Q

the difference between the

current and preceding states of a system

A

Divergence

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54
Q

The controlled process accelerates until the
limiting constraints of the controlled subsystem
are reached.

A

Positive feedback (self-reinforcing loop)

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55
Q

—amplify vital processes
—provide adaptation - fast response to external factors and transition from the initial state to another, more appropriate state

A

Positive feedback loops

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56
Q

aggravate morbid conditions

A

Positive feedback loops

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57
Q

the control results in

balancing of the controlled subsystem

A 
Negative feedback (self-correcting loop or
balancing loop)
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58
Q

minimizing the difference between the controlled parameter and the reference
(setpoint)

A

Balancing

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59
Q

Ensures the quality and reliability of the control system

A

Negative feedback

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60
Q
  • stability of body functions
  • constant values of vital parameters
  • resistance to external factors
A

Negative feedback loops

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61
Q

Basic mechanism of:
• Homeostasis (the stable condition inside the body)
• the balance of energy and metabolites in the body
• the control of the populations of species etc.

A

Negative feedback loops

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62
Q

— area between the curves of the reference

and actual values of the controlled parameter

A

Control area

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63
Q

a simplified physical or mathematical representation of a system used for its
investigation

A

Model

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64
Q

methods for investigation of systems using their models

A

Modelling

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65
Q 
•Mathematical description of
some aspects of the real system.
• Uses mathematics and
computers to produce
information about the studied
system.
A

Mathematical model

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66
Q

Material object performing

similarly to the real system

A

Physical model

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67
Q

• physically separate the cell from the environment
• divide the cell into many smaller compartments
with diverse functions

A

Barrier functions of bio-membranes

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68
Q

• ensure high speed and efficiency due to their
large total area
• ensure the vectoral (directed) flow of complex
biological processes

A

Metabolic functions of bio-membranes

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69
Q

Each membrane has two surfaces - inner and

outer

A

Asymmetrical membranes

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70
Q

the surfaces have

different composition, structure and functions

A

Asymmetrical membranes

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71
Q

……. are:
•general (e.g. cytosolic)
• specialized (e.g. myelinated)

A

Natural biomembranes

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72
Q

……….. molecule is placed into water and it takes up space between the
water molecules restricting their ability to hydrogen bond with each other

A

Hydrophobic/ non polar

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73
Q

Enthalpy needed to break some of the hydrogen

bonds between the water molecules

A

Hydrophobic/non polar interactions

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74
Q

In hydrophobic reactions the presence of a nonpolar (hydrophobic) molecules ……… the entropy of the water

A

decrease

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75
Q

easily hydrogen bond with water

A

Hydrophilic interactions

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76
Q

Release of water from surface increases its entropy

A

Hydrophilic interactions

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77
Q

are both hydrophobic and

hydrophilic

A

Amphiphilic molecules

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78
Q

water mobile phase freely exchangeable with

water inside or outside of the cell

A

free

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79
Q

Water - mobile phase surrounded by lipids,
which is slowly exchanged with water inside or
outside of the tell

A

captured

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80
Q

immobile water molecules

surrounding the polar parts of lipids and proteins due to solvation

A

Bounded

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81
Q

At physiological temperatures the lipids are in a ……… state

A

mesomorphous (liquid crystalline)

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82
Q
  • ordered structure of the membrane

* sufficient fluidity of the membrane is ensured by…….

A

mesomorphous (liquid crystalline)

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83
Q

…….. proteins are positioned on the surface of the lipid bilayer (surface proteins) or are partially submerged in the bilayer

A

Peripheral

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84
Q

……… proteins - span the entire bilayer

A

Integral

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85
Q

attached to proteins and lipids on the extracellular surface

A

Carbohydrates

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86
Q

Half life of proteins

A

2-140 hours

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87
Q

Half life of Lipids

A

14 to 80 hours

88
Q

Formed on a water-air boundary by a single layer of lipids

A

Flat monolayer membranes

89
Q

Used to investigate:
• the changes of the states of the lipids at different
temperatures,
• the area occupied by a single lipid molecule in
different states,
• the effect of medicinal substances on the lipid
bilayer

A

Flat monolayer membranes

90
Q

Both surfaces of the membrane are in contact with water

A

Flat bilayer membranes

91
Q

Used to study:
• the electrical resistance of membranes,
• the generation of surface electric charge on
membranes,
• the mechanism of action of antibiotics, etc.

A

Flat bilayer membranes

92
Q

Water dispersions of lipids- micelles and liposomes

A

Spherical membranes

93
Q

monolayer spherical membranes (the hydrophobic fatty chains of the lipids are oriented towards the centre)

A

Micelles

94
Q

spherical membranes consisting of one or more lipid bilayers

A

Liposomes

95
Q

• investigation’s of the structure of lipid bilayers
• investigation’s of the permeability of
membranes to various substances
• Delivery of drugs directly into cells

A

Applications of liposomes

96
Q

……..depend on

the proteins-to-lipids mass ratio which varies from 1:4 to 4:1

A

Mechanical properties of membranes

97
Q

Thickness of bio-membranes can be measured by:

A

X-ray scattering: 11 nm

electron microscope: 7 nm

98
Q

the ability of the membrane to support mechanical stress when stretched or bent

A

Elasticity

99
Q

Membrane viscosity n can be measured using

A

Stokes-Einstein equation

100
Q

The diffusion constant D depends on the

A

microscopic structure of the membrane

101
Q

Biomembnanes are: permeable to …..

A

water and neutral lipophilic substances

102
Q

Biomembnanes are:

poorly permeable to …..

A

polar (hydrophilic)

substances

103
Q

Biomembnanes are: practically impermeable to……

A

charged molecules

and small ions

104
Q

Membrane permeability depends on….

A

the relative concentrations of the various types of lipids

105
Q
  • carry one positive and one negative charge on

different atoms but no net charge

A

zwitterions (hybrid ions)

106
Q

phosphatidylserine

A

one negative charge

107
Q

cardiolipin

A

two negative charges

108
Q

ln a membrane lipids are arranged to ……… the potential energy of the interactions between them and the surrounding water molecules:

A

minimize

109
Q
  • lipids are fluid and anisotropic

* stable in a limited temperature range

A

Mesomotphous (liquid crystalline) state

110
Q

Lipids are

A

thermotropic mesomorphs

111
Q

The characteristic temperature at which lipids
melt from solid (gel) to mesomorphous (liquid
crystalline) state

A

Phase transition temperature

112
Q

Phase transition temperature depends on the ……. and the number
of ………. in them

A

length of the fatty chains

double bonds

113
Q

Tp = +44 degrees C to + 86 Degrees C for

A

saturated chains

114
Q

Tp = -49 degrees C to + 13 degrees C for

A

unsaturated chains

115
Q

• Shift in the ratio between the gel, and mesomorphous states which leads to changes of all mechanical properties of the membrane
• Changes of mechanical properties of the
membrane are associated with…

A

Changing the temperature or the degree of unsaturation

116
Q

Longer hydrocarbon tails ………..dispersion
forces making it more difficult to melt the
bilayer

A

increase

117
Q

Unsaturated lipids and lipids with shorter tails

have ……… melting temperatures

A

lower

118
Q

In general, anything that weakens dispersion
forces will ……… the melting temperature,
……… fluidity, and …….. permeability

A

reduce

increase

increase

119
Q

A measure of transport is the

A

flux density

120
Q
  • the amount (of substance)
    that moves through a unit area normal to the
    direction of motion x during a unit time interval
A

Flux density

121
Q

An Exergonic (spontaneous) process is…

A

Passive transport

122
Q

Passive transport

A

reduces the free energy of the system

123
Q 
The gradients move substances from
high to low:
—concentration
—potential
—pressure
A

Passive transport

124
Q

the net transport of solute
molecules through random motion in the bulk of a
solution

A

Simple diffusion

125
Q

Describes the variations of the concentration of the diffusing substance in time and space

A

Fick’s Second Law

126
Q

Concentration falls with the square of distance diffused

A

Fick’s Second Law

127
Q

Diffusion time 𝛕 increases with the square

of distance:

A

Fick’s Second Law

128
Q

passive transport

facilitated by a transport protein (transporter, carrier)

A

Facilitated diffusion

129
Q

the protein transports only one substance or a group of similar substances

A

Specific

130
Q

The diffusion of the solvent (water) across a membrane

separating areas with different concentrations of the solute

A

Osmosis

131
Q

The driving force of osmosis is the

A

osmotic pressure

132
Q

…….solutions have equal osmotic pressures

A

Isotonic

133
Q

……… solutions have higher osmotic pressure

A

hypertonic

134
Q

……… solutions have lower osmotic pressure

A

Hypotonic

135
Q

Passive transport of the solvent across a
membrane due to hydrostatic pressure
gradient

A

Filtration

136
Q

The solvent flux for filtration depends on
the ………. of the solvent and can be
calculated by ……..

A

viscosity

Poiseuille’s law

137
Q

Usually …….. and ……..are most important for the transport of water across
cell membranes

A

osmosis

electroosmosis

138
Q

Dominating type of water transport:

…….. at the arterial end -water leaves the capillaries

A

Filtration

139
Q

Dominating type of water transport:
……… at the venous end - water enters
into the capillaries

A

Osmosis

140
Q

sum of the

chemical, concentration, and electric potentials:

A

Electrochemical potential

141
Q

• Facilitated diffusion
• Diffusion through pores and channels in the
membrane
• Simple non-mediated diffusion through the
lipid bilayer

A

Mechanisms

Of The Passive Transport Of Ions

142
Q

– small hydrophobic molecules (carriers) which shield the charge of the ion
and facilitate its diffusion through the membrane

A

Ionophores

143
Q

Carrier operation is temperature dependent in

A

Ionophores

144
Q

Pore-forming amphiphilic antibiotic

A

Gramicidin

145
Q

—Two gramicidin molecules located head to-head in the lipid bilayer form a ……… pore
• The pore lets through up to 108 cations per
second – much faster transport than by a
…….. molecule

A

cationic

carrier

146
Q

Gramicidin selectivity

A

low

147
Q

Mechanically-gated channels are membrane

……… capable of responding to …….. over a wide dynamic range of external mechanical stimuli

A

proteins

mechanical
stress

148
Q

– substances which selectively

block ion channels

A

Inhibitors

149
Q

Bind to centres inside the channel and

stop the flow of ions

A

Inhibitors

150
Q

Determines the passive flux density of an ion species through a membrane

A

The Electrodiffusion Model

151
Q

The input ion flux density Ji depends only on the ion concentration in the…..

A

extracellular liquid

152
Q

The output ion flux density Je depends only on
the ion concentration ci
in the ……..

A

intracellular liquid

153
Q

The diffusion rate for cations through the
membrane of a nerve cell is about ……. times higher than the
diffusion rate of …….

A

10

anions

154
Q

………is a transient

phenomenon – it gradually decays to zero because the concentrations on both sides becomes equal

A

Diffusion potential

155
Q

…….. is valid for thick membranes and not for the thin lipid bio-membranes

A

Henderson’s equation

156
Q

In cells:
……….. ions are close to equilibrium – the
Nernst equation can be used to calculate the
potential drop on the membrane

A

Potassium

157
Q

In cells: …….. ions are far from equilibrium

A

Sodium

158
Q

The cytoplasm has a ………. electric potential relative to the extracellular fluid

A

negative

159
Q

Sodium ion concentration in the cell is …..

A

much less than outside of the cell

160
Q

Potassium ion concentration in the cell is ………

A

much higher than outside of the cell

161
Q

Chlorine ion concentration in the cell is ,,,,,,,,

A

less than outside of the cell

162
Q

……… move ions from low

to high electrochemical potential

A

Active transport systems

163
Q

The sodium potassium ion pump works in the presence of ………. and
……….

A

Mg2+

ATP

164
Q

The hydrolysis of one adenosine triphosphate
(ATP) molecule provides energy for the active
transport of:

A

-three sodium ions out of the cell, and

—two potassium ions into the cell

165
Q

• Exchange of ions with unequal charges
• Modifies the transmembrane potential
Example: three Na+ exchanged for two K+

A

Electrogenic Ion transport

166
Q 
• Exchange of ions with equal charges
• Does not modify the transmembrane
potential
• Maintains concentration gradients
• Example: one Na+ exchanged for one K+
A

Nonelectrogenic Ion Transport

167
Q

For different types of cells the resting potential varies from ……..

A

–50 mV to –100 mV

168
Q

The strongest contribution to the resting potential is from the ion with the ……… membrane permeability

A

highest

169
Q

The flux of potassium ions across the
membrane increases the absolute value of
the resting potential or …….

A

(makes it more negative)

170
Q

The flux of sodium ions across the membrane
decreases the absolute value of the resting
potential or ……….

A

(makes it less negative)

171
Q

The concentrations of ions in the extracellular

fluid are ………for all human tissues

A

the same

172
Q

The concentrations of ions in the intracellular

fluid are …….. in all human cells

A

almost the same

173
Q

The resting potential of various types of cells
is ………. because their membranes have
different permeabilities

A

different

174
Q

The rapid change in electrical potential that
occurs between the inside and outside of a
cell when it is stimulated by a sufficiently strong stimulus

A

Action potential

175
Q

The action potential is generated when the

membrane potential …….. a threshold

A

rises above

176
Q

– a new action
potential can not be generated, whatever the
strength of the stimulus (lasts 2…5 ms in nerve
fibres)

A

Absolute refractory period

177
Q

a new action
potential can be generated but the threshold is
higher than usual

A

Relative refractory period

178
Q

The sodium-potassium ion pump has ……… effect
on the depolarisation and repolarisation
phases

A

no

179
Q

The function of the sodium-potassium ion
pump is to ……….. the concentration
gradients of the sodium and potassium ions

A

replenish

180
Q

The action potentials generated by different

cells are ………

A

almost identical

181
Q

The impulses propagating down nerve fibres

have……… shapes and peak values

A

identical

182
Q

A ……. stimulus initiates the next impulse
earlier during the relative refractory period
than a ………. stimulus

A

strong

weak

183
Q

The strength of the stimulus is coded by the

………. of the impulses

A

repetition frequency

184
Q

The burst length carries information about the

………..

A

duration of the stimulation

185
Q
  • the external surface is charged negatively

* the internal surface is charged positively

A

Excited section of membrane

186
Q

currents on the surfaces of the membrane between the excited and non-excited sections

A

Local currents

187
Q

Direction of The Local Currents On the external surface of the membrane –

A

from the unexcited towards the excited section

188
Q

Direction of The Local Currents on the internal surface of the membrane

A

from the excited towards the unexcited

section

189
Q

•the membrane potential decreases (becomes
less negative)
• reaches the threshold value
• an action potential is generated

A

In the vicinity of the excited section

190
Q

At the initial excited section

A

—Repolarisation takes place

191
Q

Describes the variations of the membrane

potential over time and along the nerve fibre

A

The cable equation

192
Q

The membrane potential ………. exponentially away from the point of excitation

A

decreases

193
Q

The decay rate is determined by the ………

and ……….. resistances

A

membrane

cytoplasm

194
Q

…………grows with increasing the :
—diameter of the nerve fibre D:
—membrane thickness d:
—membrane resistivity 𝛒m

A

The Length Constant

195
Q

……… diminishes with increasing the

—cytoplasm resistivity 𝛒i

A

The Length Constant

196
Q

The action potential impulses propagate without

decay along the membrane

A

Non decremental Conduction

197
Q

A substance composed of:
—lipids (about 80%);
—proteins (about 20%);
—cholesterol.

A

Myelin

198
Q

Depolarisation takes place only at the nodes

of Ranvier

A

Depolarisation

Of Myelinated Fibres

199
Q

• The excitation jumps from node to node –

……….

A

saltatory conduction of the impulse

200
Q

Advantages

Of Saltatory Conduction

A
  • High conduction speed of the impulses

* More efficient conduction

201
Q

—the resistivity of the surrounding fluid
increases
—the diameters of the nerve fibres increase

A

The interactions become stronger

202
Q

The surface of the membrane builds up electric

charge due to…….

A
  • dissociation

- adsorption

203
Q

Adsorption is very ,,,,,,, because of the

hydration of the protein molecules

A

weak

204
Q

In Acidic Solutions:
……….. groups dissociate from the
protein molecule
• Protein ……….. are obtained:

A

Basic OH-

cations

205
Q

In Proteins In Basic Solutions
• ………. dissociates from the protein
molecule
• Protein ,,,,,,,,,, are obtained :

A

Acidic H+

anions

206
Q

• The ions which:
—remain on the cell surface on dissociation
—are attached to the cell surface by
adsorption

A

Potential Determining Ions

207
Q 
The ions which:
• dissolve in the liquid phase on
dissociation
• remain in the liquid phase on
adsorption
A

Counterions

208
Q

The ions of the Stern layer are attached to the surface by …………

A

adsorption forces

209
Q

The ions of the diffuse layer are attracted by ……..

A

Coulomb (electrostatic)

forces

210
Q

counterions are

attracted towards the surface

A

Electrostatic forces

211
Q

counterions diffuse

away from the surface (from high to low concentration)

A

Thermal motion

212
Q

The electrical potential
……… exponentially
away from the surface

A

decays

213
Q

the motion of the dispersed

phase relative to the fluid caused by an external electric field

A

Electrophoresis

214
Q

The fluid pH value at
which the electrophoretic
mobility of the suspended
particles vanishes

A

Isoelectric point

215
Q

Electrophoretic method for separation of proteins with only slightly differing
electrophoretic mobilities:

A

Immunoelectrophoresis

biophysics (9 decks)

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