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MISS ESTRUCH FLASHCARDS > TOPIC 2: CELLS > Flashcards

TOPIC 2: CELLS Flashcards

1
Q

Cell membrane
structure

A

Phospholipid bilayer with
embedded intrinsic & extrinsic
proteins

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2
Q

Cell membrane
function

A

Selectively permeable barrier
controls passage of substances
in and out the cell
barrier between internal and
external cell environments

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3
Q

Nucleus
Structure

A

Nuclear pores, nucleolus, DNA
and nuclear envelope

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4
Q

Nucleus
Function

A

Site of transcription & premRNA
splicing - mRNA
production
site of DNA replication
nucleolus makes ribosomes
nuclear pore allows movement
of substances to/from
cytoplasm

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5
Q

Mitochondria
Structure

A

Double membrane with inner
membrane folded into cristae
70S ribosomes in matrix
small, circular DNA
enzymes in matrix

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6
Q

Mitochondria
Function

A

Site of aerobic respiration
produces ATP

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7
Q

Chloroplast
structure

A

Thylakoid membranes stacked
to form grana, linked by
lamellae
stroma contains enzymes
contains starch granules, small
circular DNA and 70S ribosomes

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8
Q

Chloroplast
function

A

Chlorophyll absorbs light for
photosynthesis to produce
organic molecules (glucose)

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9
Q

Organisms
containing
chloroplasts

A

Plants
Algae

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10
Q

Golgi apparatus
stucture

A

Fluid-filled, membrane-bound
sacs (horseshoe shaped)
vesicles at edge

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11
Q

Golgi apparatus
function

A

Modifies proteins received from
RER
packages them into vesicles to
transport to cell membrane for
exocytosis
makes lysosomes

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12
Q

Lysosome
structure

A

Type of Golgi vesicle containing
digestive enzymes

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13
Q

Lysosome
function

A

Contains digestive enzymes
e.g lysozymes to hydrolyse
pathogens/cell waste products

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14
Q

Rough
endoplasmic
reticulum function

A

Site of protein synthesis
folds polypeptides to secondary
& tertiary structures
packaging into vesicles to
transport to Golgi

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15
Q

Smooth
endoplasmic
reticulum function

A

Synthesises and processes
lipids

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16
Q

Cell wall
function

A

Provides structural strength,
rigidity and support to cell
helps resist osmotic pressures

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17
Q

Ribosome
structure

A

Small and large subunit
made of protein and rRNA
free floating in cytoplasm &
bound to RER
70S in prokaryotes,
mitochondria and chloroplasts
80S in eukaryotes

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18
Q

Ribosome
function

A

Site of translation in protein
synthesis

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19
Q

Rough
endoplasmic
reticulum structure

A

System of membranes with
bound ribosomes
continuous with nucleus

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20
Q

Smooth
endoplasmic
reticulum structure

A

System of membranes with no
bound ribosomes

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21
Q

Cell wall
structure

A

In plant, fungal and bacterial
cells
plants - made of microfibrils of
cellulose
fungi - made of chitin
bacteria - murein

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22
Q

Cell vacuole
structure

A

Fluid-filled
surrounded by a single
membrane called a tonoplast

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23
Q

Contrast
prokaryotic &
eukaryotic cells

A

Prokaryotic cells are smaller
prokaryotes have no membrane
bound organelles
prokaryotes have smaller 70S
ribosomes
prokaryotes have no nucleus -
circular DNA not associated with
histones
prokaryotic cell wall made of
murein instead of
cellulose/chitin

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24
Q

Occasional
features of
prokaryotes

A

Plasmids - loops of DNA
capsule surrounding cell wall -
helps agglutination + adds
protection
flagella for movement

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25
Q

Cell vacuole
function

A

Makes cells turgid - structural
support
temporary store of sugars,
amino acids
coloured pigments attract
pollinators

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26
Q

Protein
carriers

A

Bind with a molecule, e.g.
glucose, which causes a change
in the shape of the protein
this change in shape enables
the molecule to be released to
the other side of the membrane

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27
Q

Protein
channels

A

Tubes filled with water enabling
water-soluble ions to pass
through the membrane
selective
channel proteins only open in
the presence of certain ions
when they bind to the protein

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28
Q

Features of
viruses

A

Non living and acellular
contain genetic material, capsid
and attachment proteins
some (HIV) contain a lipid
envelope + enzymes (reverse
transcriptase)

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29
Q

3 types of
microscopes

A

Optical (light) microscopes
Scanning electron microscopes
(SEM)
Transmission electron
microscopes (TEM)

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30
Q

Magnification

A

How many times larger the
image is compared to the object
calculated by equation:
MAGNIFICATION=IMAGE SIZE/ACTUAL SIZE

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31
Q

Resolution

A

The minimum distance between
two objects in which they can
still be viewed as separate
determined by wavelength of
light (for optical microscopes)
or electrons (for electron
microcopes)

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32
Q

Optical
microscopes

A

Beam of light used to create
image
glass lens used for focusing
2D coloured image produced

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33
Q

Evaluate
optical
microscopes

A

Poorer resolution as long
wavelength of light - small
organelles not visible
lower magnification
can view living samples
simple staining method
vaccum not required

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34
Q

Transmission
electron
microscopes

A

Beam of electrons passes
through the sample used to
create an image
focused using electromagnets
2D, black & white image
produced
can see internal ultrastructure
of cell
structures absorb electrons and
appear dark

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35
Q

Evaluation
TEMs

A

Highest resolving power
high magnification
extremely thin specimens
required
complex staining method
specimen must be dead
vaccum required

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36
Q

Scanning
electron
microscopes

A

Beam of electrons pass across
sample used to create image
focused using electromagnets
3D, black and white image
produced
electrons scattered across
specimen producing image

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37
Q

Evaluation
SEMs

A

High resolving power
high magnification
thick specimens usable
complex staining method
specimen must be dead
vaccum required

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38
Q

Why calibrate
eyepiece
graticule?

A

Calibration of the eyepiece is
required each time the objective
lens is changed
calibrate to work out the
distance between each division
at that magnification
Break

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39
Q

Purpose of cell
fractionation

A

Break open cells & remove cell
debris
so organelles can be studied

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40
Q

Homogenisation

A

Process by which cells are
broken open so organelles are
free to be separated
done using homogeniser
(blender)

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41
Q

Homogenisation
conditions

A

Cold reduces enzyme activity
preventing organelle digestion
Isotonic prevents movement of
water by osmosis - no bursting /
shrivelling of organelles
Buffered resists pH changes
preventing organelle + enzyme
damage

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42
Q

Ultracentrifugation

A

Homogenate solution filtered to
remove cell debris
solution placed in a centrifuge
which spins at a low speed
initially
then increasingly faster speeds
to separate organelles
according to their density

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43
Q

Differential
centrifugation

A

Supernatant first out (spun at
lowest speed) is most dense =
nuclei
spun at higher speeds
chloroplasts -> mitochondria ->
lysosomes -> RER/SER ->
ribosomes (least dense)

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44
Q

Binary Fission

A

Involves circular DNA &
plasmids replicating
cytokinesis creates two
daughter nuclei
each daughter cell has one copy
of circular DNA and a variable
number of plasmids

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45
Q

Cell cycle

A

1) Interphase (G1, S, G2)
2) nuclear division - mitosis or
meiosis
3) cytokinesis

46
Q

Interphase

A

Longest stage in the cell cycle
when DNA replicates (S-phase)
and organelles duplicate while
cell grows (G1&G2-phase)
DNA replicates and appears as
two sister chromatids held by
centromere

47
Q

Mitosis

A

One round of cell division
two diploid, genetically
identical daughter cells
growth and repair (e.g. clonal
expansion)
comprised of prophase,
metaphase, anaphase and
telophase

48
Q

Prophase

A

Chromosomes condense and
become visible
nuclear envelope disintegrates
in animals - centrioles separate
& spindle fibre structure forms

49
Q

Metaphase

A

Chromosomes align along
equator of cell
spindle fibres released from
poles now attach to centromere
and chromatid

50
Q

Anaphase

A

Spindle fibre contracts (using
ATP) to pull chromatids,
centromere first, towards
opposite poles of cell
centromere divides in two

51
Q

Telophase

A

Chromosomes at each pole
become longer and thinner
again
spindle fibres disintegrate +
nucleus reforms

52
Q

Mitotic index

A

Used to determine proportion of
cells undergoing mitosis
Calculated as a percentage OR
decimal
MITOTIC INDEX=THE NUMBER OF CELLS IN MITOSIS/TOTAL NUMBER OF CELLS
x100 for percentage

53
Q

Fluid mosaic
model

A

Describes the lateral movement
of membranes
with scattered embedded
intrinsic and extrinsic proteins
membrane contains
glycoproteins, glycolipids,
phospholipids and cholesterol

54
Q

Phospholipids
in membranes

A

Phospholipids align as a bilayer
hydrophilic heads are attracted
to water
hydrophobic tails repelled by
water

55
Q

Cholesterol

A

Present in eukaryotic organisms
to restrict lateral movement of
the membranes
adds rigidity to membraneresistant
to high temperatures
& prevents water + dissolved
ions leaking out

56
Q

Selectively
permeable
membrane

A

Molecules must have specific
properties to pass through
plasma membrane
lipid soluble (hormones e.g.
oestrogen)
very small molecules
non-polar molecules (oxygen)

57
Q

Simple
diffusion

A

Net movement of molecules
from an area of higher
concentration to an area of
lower concentration
until equilibrium is reached
passive

58
Q

Facilitated
diffusion

A

Passive process using protein
channels/carriers
down the concentration
gradient
used for ions and polar
molecules e.e sodium ions
and large molecules e.g. glucose

59
Q

Osmosis

A

Net movement of water
from an area of higher water
potential to an area of lower
(more negative) water potential
across a partially permeable
membrane

60
Q

Water
potential

A

The pressure created by water
molecules
measured in kPa and
represented by symbol ψ
pure water has a water potential
of 0kPa
the more negative the water
potential, the more solute must
be dissolved

61
Q

Hypertonic
solution

A

When the water potential of a
solution is more negative than
the cell
water moves out of the cell by
osmosis
both animal and plant cells will
shrink and shrivel

62
Q

Hypotonic
solution

A

When the water potential of a
solution is more positive (closer
to zero) than the cell
water moves into the cell by
osmosis
animal cells will lyse (burst)
plant cells will become turgid

63
Q

Isotonic

A

When the water potential of the
surrounding solution is the
same as the water potential
inside the cell
no net movement in water
cells would remain the same
mass

64
Q

Active
transport

A

The movement of ions and
molecules from an area of lower
concentration to an area of
higher concentration using ATP
and carrier proteins
carrier proteins act as selective
pumps to move substances

65
Q

Role of carrier
protein in active
transport

A

When molecules bind to the
receptor - ATP will bind to
protein on inside of membrane
and is hydrolysed to ATP / Pi
protein changes shape and
opens inside membrane

66
Q

Co-transport

A

The movement of two
substances across a membrane
together, when one is unable to
cross the membrane itself
involves a cotransport protein
involves active transport
e.g. absorption of
glucose/amino acids from
lumen of intestines

67
Q

Molecules
lymphocytes
identify

A

Pathogens (bacteria, fungi,
viruses)
cells from other organisms of
same species (transplants)
abnormal body cells (tumour
cells)
toxins (released from bacteria)

68
Q

Antigens

A

Proteins on the cell-surface
membrane
trigger an immune response
when detected by lymphocytes

69
Q

Antigenic
variability

A

When pathogenic DNA mutates
causing a change in shape of
antigen
previous immunity is no longer
effective as memory cells don’t
recognise new shape of antigen.
specific antibody no longer
binds to new antigen

70
Q

Physical
barriers

A

Anatomical barriers to
pathogens
skin
stomach acid
lysozymes in tears

71
Q

Phagocytes

A

Non-specific immune response
phagocytes become antigen presenting
cells after
destroying pathogen

72
Q

T lymphocytes

A

Made in bone marrow and
mature in thymus gland
involved in cell-mediated
immune response
respond to antigen-presenting
cells

73
Q

Antigen presenting
cells

A

Any cell that presents a non-self
antigen on their surface
infected body cells
macrophage after
phagocytosis
cells of transplanted organ
cancer cells

74
Q

Role of T
helper cells

A

Have receptors on their surface
that attach to antigens on APCs
become activated - clonal
selection

75
Q

Role of cloned
T helper cells

A

Some remain as helper T cells &
activate B lymphocytes
stimulate macrophages for
phagocytosis
become memory cells for that
shaped antigen
become cytotoxic killer T cells

76
Q

Cytotoxic
T cells

A

Destroy abnormal / infected
cells by releasing perforin
so that any substances can
enter or leave the cell and this
causes cell death

77
Q

B lymphocytes

A

Made in bone marrow and
mature in bone marrow
involved in humoral immune
response
involves antibodies

78
Q

Humoral
response

A

APC activates B cell
B cell undergoes clonal
selection and expansion - rapid
division by mitosis.
differentiate into plasma cells /
memory B cells
plasma cells make antibodies

79
Q

B memory cells

A

derived from B lymphocytes
remember specific antibody for
particular antigen
will rapidly divide by mitosis
and differentiate in plasma
cells upon secondary encounter
resulting in large numbers of
antibodies rapidly

80
Q

Antibodies

A

Quaternary structure proteins
made of four polypeptide chains
different shaped binding site =
variable region
complementary to a specific
antigen

81
Q

Agglutination

A

Antibodies have two binding
sites and are flexible - clumps
pathogens together
makes it easier for phagocytes
to locate and destroy pathogen

82
Q

Passive
immunity

A

Antibodies introduced into body
plasma and memory cells not
made as no interaction with
antigen
short-term immunity
fast acting

83
Q

Active
immunity

A

Immunity created by own
immune system - antibodies
made
exposure to antigen
plasma and memory cells made
long term immunity
slower acting

84
Q

Natural active
immunity

A

After direct contact with
pathogen through infection
body creates antibodies and
memory cells

85
Q

Artificial active
immunity

A

Creation of antibodies and
memory cells following
introduction of an attenuated
pathogen or antigens
vaccination

86
Q

Vaccinations

A

Small amounts of dead or
attenuated pathogens injected /
ingested
humoral response activated
memory cells are able to divide
rapidly into plasma cells when
re-infected

87
Q

Primary vs
Secondary
response

A

Primary = first exposure to the
pathogen
longer time for plasma cell
secretion & memory cell
production
for the secondary response,
memory cells divide rapidly into
plasma cells
so a large number of antibodies
made rapidly upon reinfection

88
Q

Herd
immunity

A

When enough of the population
is vaccinated so pathogen is not
transmitted and spread easily
provides protection for those
without vaccine

89
Q

Monoclonal
antibodies

A

A single type of antibody that
can be isolated and cloned
antibodies that are identical -
from one type of B lymphocyte
complementary to only one
antigen

90
Q

Uses of
monoclonal
antibodies

A

Medical treatment - targeting
drugs by attaching antibody
complementary to tumour cell
antigen
medical diagnosis - pregnancy
tests

91
Q

Pregnancy test

A

ELISA test which uses 3
monoclonal antibodies and
enzymes to test for hCG

92
Q

Purpose of
ELISA test

A

Detect the presence and
quantity of an antigen
used for medical diagnosis. Eg.,
HIV

93
Q

Ethical issues
with monoclonal
antibodies

A

Requires mice to produce
antibodies and tumour cells
requires a full cost-benefit
analysis

94
Q

HIV structure

A

Core = RNA and reverse
transcriptase
capsid = protein coat
lipid envelope taken from hosts
cell membrane
attachment proteins so it can
attach to Helper T cells

95
Q

HIV replication

A

Attaches to CD4 receptor on
helper T cells
protein fuses with membrane
allowing RNA + enzymes to enter
reverse transcriptase makes
DNA copy and this is inserted
into nucleus
nucleus synthesises viral
proteins

96
Q

Auto
Immunodeficiency
Syndrome (AIDs)

A

When HIV has destroyed too
many T helper cells, host is
unable to produce adequate
immune response to other
pathogens
host susceptible to
opportunistic infections

97
Q

Role of
antibodies in
ELISA

A

First antibody added is
complementary to antigen in
well - attaches
second antibody with enzyme
added which attaches to first
antibody as complementary.
when substrate solution added
enzyme can produce colour
change

98
Q

Why vaccines
may be unsafe

A

Inactive virus may become
active - viral transformation
non-pathogenic virus can
mutate and harm cells
side effects of immune
response
people may test positive for
disease

99
Q

Why are
antibiotics
ineffective against
viruses?

A

Viruses are inside host cells
where antibiotics cannot reach
antibiotics affect parts of
bacteria that viruses do not
have (e.g the cell wall)

100
Q

Why do you
wash well in
ELISA

A

Removes unbound 2nd
antibodies
otherwise enzyme may be
present → colour change →
false positive

101
Q

Pathogens

A

Microorganisms that cause a
disease
by releasing toxins or killing
cells / tissues

102
Q

Cytokinesis

A

Final stage in the cell cycle
when the cytoplasm splits in
two
creates two new cells

103
Q

Uncontrolled
mitosis

A

Uncontrolled cell division can
lead to the formation of
tumours and of cancers
many cancer treatments are
directed at controlling the rate
of cell division

104
Q

Viral
replication

A

Following injection of their
nucleic acid
the infected host cell replicates
the virus particles

105
Q

Cell adaptations for
rapid transport
across membranes?

A

Increase in surface area or
membrane
increase in the number of
protein channels and carrier
molecules in the membranes

106
Q

Antigenantibody
complex

A

When a complementary
antibody binds to an antigen
this clumps pathogens together
(agglutination)

107
Q

What does HIV cause?

A

AIDS

108
Q

What is the structure of HIV?

A

Lipid envelope which has attachment proteins
Inside the lipid envelope, there is capsid which has 2 single strand of RNA and one reverse transcriptase (catalyses the production of DNA from RNA) ]and an enzyme

109
Q

Why is HIV classed as a retrovirus?

A

Presence of reverse transcriptase and its consequent ability to make DNA from RNA

110
Q

How does HIV replicate?

A

HIV enters the bloodstream and circulates the body
Protein on HIV binds to protein CD4 (most frequently bind to helper T cells)
Protein capsid fuses with the cell surface membrane, RNA and the enzymes of HIV enter the helper T cells
HIV’s reverse transcriptase converts the virus’ RNA to DNA
The new DNA is moved into the helper T cells’s nucleus and its inserted into the cells DNA
The RNA DNA in the nucleus creates mRNA using the cells enzymes
This mRNA contains the instructions for making new viral proteins and the RNA goes into the new HIV
The mRNA passes out of the nucleus through the nuclear pore and uses the cells protein synthesis mechanisms to make HIV particles
HIV particles break away from the helper T cells with a piece of it’s cell membrane, forming a lipid envelope

111
Q

How does HIV cause the symptoms of AIDS

A

HIV cause AIDS by killing or interfering with the normal helper T cells
Without sufficient helper T cells the immune system cannot stimulate B cells to produce antibodies or cytotoxic T cells that kill the infected by a pathogen and memory cells are damaged
As a result, they become susceptible to to other infections and cancers

112
Q

How to prokaryotic cells replicate?

A

Binary fission

MISS ESTRUCH FLASHCARDS (8 decks)

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