topic one Flashcards
(200 cards)
1
Q
rules of cell theory
A
Living organisms are composed of cells (one or more) – that is, cells are the building blocks of organisms.
Cells are the smallest units of life – that is, a cell is the basic unit capable of carrying out all the functions of a living organism.
Cells come from pre-existing cells (omni cellulae e cellula) – that is, cells do not show spontaneous generation.
2
Q
Striated muscle tissue is composed of repeated units called
A
sarcomeres
3
Q
what sort of pattern do muscle cells show
A
striated/stripy
4
Q
how large is the avergae muscle fibre cell
A
30mm long (very large)
5
Q
what idea do musle cells challenge
A
the idea that the cell has one nucleus, as the muscle cell is multinucleated.
6
Q
how large is acetabularia
A
0.5 to 10cm
7
Q
what are the three parts of acetbaularia
A
the rhizoid (small roots), the stalk and a top umbrella made of branches that may fuse into a cap
8
Q
what notions does acetbabularia challenge
A
that they must be simple in structure and small in size.
9
Q
what are aseptate fungal hyphae
A
long threads (hyphae) with many nuclei. They have no dividing cell walls, called septa (singular: septum). The result of this is shared cytoplasm and multiple nuclei (singular: nucleus).
10
Q
what idea do aspetate fungal hyphae challenge
A
the idea that a cell is a single unit as the fungal hyphae have many nuclei, are very large and possess a continuous, shared cytoplasm.
11
Q
typical size of an animal cell
A
10 to 20 micrometers in diameter
12
Q
calculating magnification
A
magnification = size of drawing / actual size
13
Q
1000nm in micrometers
A
1 micrometer
14
Q
1000 micrometers in mm
A
1 mm
15
Q
how to convert 1mm into micrometers
A
multiply by 1000
16
Q
how to convert 1micrometer to nm
A
multiply by 1000
17
Q
what are the functions of life
A
metabolism
response
growth
reproduction
excretion
homeostasis
nutrition
18
Q
define metabolism
A
The regular set of life-supporting chemical reactions that takes place within the cells of living organisms.
19
Q
define growth
A
an increase in size or shape that occurs over a period of time
20
Q
define response
A
A reaction by the living organism to changes in the external environment.
21
Q
define homeostasis
A
The maintenance of a constant internal environment by regulating internal cell conditions.
22
Q
define nutrition
A
The intake of nutrients, which may take different forms in different organisms. Nutrition in plants involves making organic molecules (during photosynthesis), while nutrition in animals and fungi involves the absorption of organic matter.
23
Q
define reproduction
A
The production of offspring, either sexually or asexually, to pass on genetic information to the next generation.
24
Q
define excretion
A
The removal of waste products of metabolism and other unimportant materials from an organism.
25
exemplar unicellular organism: paramecium
usually less than 0.25mm insize
heterotrophs
have cilia to help them move
26
exemplar unicellular organism: chlamydomonas
10 to 30 µm in diameter
cell wall
chloroplaswt
eyespot
2x flagella
autotrophs
27
what is a heterotroph
A heterotroph is an organism that feeds by taking in organic substances (usually other living things).
28
what is an autotroph
An autotroph is an organism that can produce its own food from inorganic sources.
29
how is the contractile vacuole used
to regulate itnernal water concentration
30
how does a SA:V ratio impact growth
As a cell grows, its volume increases by the power of 3 (cubed), whereas the surface area increases by the power of 2 (squared). Therefore, its surface area to volume ratio decreases.
31
is it better to have a small or large SA:V ratio
small
32
do small organisms have a small or large SA:V ratio
large
33
asa cell increases in size what happens to its SA:V
it decreases
34
why did organisms grow larger
no longer limited by size of one cell
35
what is differentiation
a process in which unspecialised cells develop into cells with a more distinct structure and function
36
what are/ what is the benefit of emergent properties
a complex system possesses properties that its constituent parts do not have – the whole is more than the sum of its parts.
37
genome define
refers to the complete set of genes, chromosomes or genetic material present in a cell or organism.
38
what is the process of cellular differentiation
When an unspecialised stem cell changes and carries out a specific function in the body, the process is called cellular differentiation. Cells differentiate to form different cell types due to the expression of different genes.
39
How do cells differentiate in multicellular organisms?
They express some of their genes some of the time, but not others.
40
define a stem cell
an undifferentiated cell of a multicellular organism that can form more cells of the same type indefinitely, and from which certain other kinds of cells arise by differentiation.
41
totipotent stem cells
Can differentiate into any type of cell including placental cells.
Can give rise to a complete organism.
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pluripotent stem cells
Can differentiate into all body cells, but cannot give rise to a whole organism.
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multipotent stem cells
Can differentiate into a few closely related types of body cell.
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unipotent stem cells
Can only differentiate into their associated cell type. For example, liver stem cells can only make liver cells.
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pathway of different stem cells, sysstems and embryo
46
potential new uses for stem cells
parkinsons
new transpolant organs
treatment of leukemia
47
describe Stargardts disease
an inherited form of juvenile macular degeneration (affects a small area near the centre of the retina) that causes progressive loss of central vision. It is caused by a recessive genetic mutation in gene ABCA4, which causes an active transport protein on photoreceptor cells to malfunction. This ultimately causes the photoreceptor cells to degenerate.
48
treatment for stargardts
Patients are given retinal cells derived from human embryonic stem cells, which are injected into the retina.
49
treatment for leukemia
Treatment in this case involves harvesting hematopoietic stem cells (HSCs), which are multipotent stem cells. HSCs can be taken from bone marrow, peripheral blood or umbilical cord blood. The HSCs may come from either the patient or from a suitable donor. The patient then undergoes chemotherapy and radiotherapy to get rid of the diseased white blood cells. The next step involves transplanting HSCs back into the bone marrow, where they differentiate to form new healthy white blood cells.
50
pros for embryonic stem cells
Cells may be used in cell therapy (replacing bad cells with good ones) to eliminate serious diseases or disabilities in the human population.
Transplants can be easily obtained without requiring the death of another human or inflicting any kind of pressure on normal body functioning which happens when someone donates an organ.
The stem cells are harvested from the embryo at an early stage when the embryo has not yet developed a nervous system and thus it is not likely to feel any pain.
51
how are embryos created to produce stem cells that correspond to those of the patients
removal of nucleus from donor egg cell
nuclear transfer of host DNA from somatic cells
4 cell stage
morula
blastocyst
52
prokaryotes
simple unicellular organisms with no internal compartmentalisation, no nucleus and no membrane bound organelles.
53
where do metabolic proccesses occur
cytoplasm
54
function of cell wall
Encloses the cell, protecting it and helping to maintain its shape; prevents the cell from bursting in hypotonic (dilute) media.
55
function of plasma membrane
Surrounds the cell, controlling the movement of substances in and out of the cell.
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function of cytoplasm
Medium that fills the cell and is the site of all metabolic reactions.
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function of pili
Protein filaments on the cell wall that help in cell adhesion and in transferring of DNA between two cells.
58
function of flagella
Much longer than pili, these are responsible for the locomotion of the organism. Their whip-like movement propels the cell along.
59
function of 70S ribosomes
Are the sites of protein synthesis.
60
function of nucleoid region
Controls all the activities of the cell, as well as the reproduction of the organism.
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function of plasmids
Small circles of DNA that carry a few genes; often these genes give the cell antibiotic resistance and are used in creating genetically modified bacteria.
62
are 80S ribosomes or 70S ribosomes smaller
70S ribosomes are smaller. they refer to the sedimentation rate of rna subunits
63
what are the steps of binary fission
The chromosome is replicated semi-conservatively, beginning at the point of origin (shown in red in Figure 2).
Beginning with the point of origin, the two copies of DNA move to opposite ends of the cell.
The cell elongates (grows longer).
The plasma membrane grows inward and pinches off to form two separate, genetically identical cells.
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eukaryotes
genetic material isolated from cytoplasm via nucleus
one of three domains (bacteria, archae and eukaryote) and four kingdoms (protocista, fungi, plantae and animalia)
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Compartmentalisation refers to
the formation of compartments within the cell by membrane-bound organelles.
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advantages of compartemntalisation
Greater efficiency of metabolism as enzymes and substrates are enclosed, and therefore much more concentrated, in the particular organelles responsible for specific functions.
Internal conditions such as pH can be differentiated in a cell to maintain the optimal conditions for different enzymes.
Isolation of toxic or damaging substances away from the cytoplasm, such as the storage of hydrolytic enzymes in lysosomes.
Flexibility of changing the numbers and position of organelles within the cell based on the cell’s requirements.
67
function of plasma membrane
Controls the movement of substances in and out of the cell.
68
function of cytoplasm
Fills the cell and holds all organelles. It also contains enzymes that catalyse various reactions (such as glycolysis) occurring within the cytoplasm.
69
function of mitochondria
A site of cellular respiration in which ATP is generated.
70
function of 80S ribosomes
The sites of protein synthesis. Free ribosomes produce proteins used inside the cell itself.
71
function of nucleus
Controls all the activities of the cell, as well as the reproduction of unicellular organisms.
72
function of nucleolus
Part of the nucleus which is involved in the production of ribosomes.
73
function of s.e.r
Responsible for producing and storing lipids, including steroids.
74
function of r.e.r.
Transports the protein produced by the ribosomes on its surface to the Golgi apparatus. These proteins are usually for use outside of the cell.
75
function of golgi apparatus
Processes and packages proteins, which are ultimately released in Golgi vesicles.
76
function of vesicle
A small sac that transports and releases substances produced by the cell by fusing with the cell membrane.
77
function of lysosymes
Contain hydrolytic enzymes and play important roles in the destruction of microbes engulfed by white blood cells, as well as in the destruction of old cellular organelles.
78
function of centrioles
Play an important role in the process of nuclear division by helping to establish the microtubules.
79
function of vacuole
Helps in the osmotic balance of the cell and in the storage of substances. It may also have hydrolytic functions similar to lysosomes.
80
function of cell wall
Protects the cell, maintains its shape and prevents it from bursting in hypotonic media.
81
function of chloroplast
These are double-membrane-bound organelles. They contain pigments (in this case mainly chlorophyll) and are responsible for photosynthesis.
82
what eurkaryotic organelles are not found in plants
lysosymes
centrioles
83
what eukaryotic organelles are not found in animals
cell wall
chloroplast
84
Microscope resolution is
the shortest distance between two separate points in a microscope’s field of view that can still be distinguished as distinct objects.
85
comparison of electron and light microscope
200nm compared to 0.1nm
86
the higher the value of resolution,
the lower the resolution
87
when would you use electron / light microscopes
electron for small cellular structures or pathogens and viruses.
light for tissues and living cells
88
who invented the fluid mosiac model
singer and nicholson in 1972. biological membranes consist of phospholipid bilayers with proteins embedded,
89
triglycerides
one glycerol and three fatty acids
90
phospholipid
a lipid where one of the fatty acids has been replaced by a phosphate group
91
which part of phospholipid is hydrophobic and hydrophilic
fatty acids (non polar) are hydrophobic
phosphate heads (polar) are hydrophilic
92
what is an amphipathic molecule
A molecule that has both a hydrophilic and a hydrophobic part
93
membrane proteins
can be categorised as integral or peripheral
94
integral proteins
Integral proteins are amphipathic (they have hydrophobic and hydrophilic properties) and are embedded in the plasma membrane. In most cases, they pass completely through the membrane.
95
peripheral proteins
Peripheral proteins are polar (hydrophilic) and are attached to the outside of the plasma membrane.
96
characteristics of membrane proteins
channels
carriers
recgonition
receptors
enzymes
97
channels in proteins
some proteins have a pore/channel that allows the passive transport (no energy required) of substances between the inside and outside of the cell.
98
carriers in proteins
these proteins bind to substances on one side of the membrane and then change shape to transport them to the other side. Carrier proteins that use energy to change shape are termed protein pumps.
99
recognition in proteins
certain proteins help the cell in differentiating between self and non-self cells (important in triggering an immune response).
100
receptors in proteins
these proteins usually span the whole membrane to relay information from the inside or outside of the cell.
101
enzumes in proteins
these are proteins that enhance the rate of reactions that happen at the membrane level.
102
glycolipids
a phospholipid and a carbohydrate attached togethe
103
purpose of glycolipid
maintaining the structure of the cell membrane and in cells differentiating between self and non-self cells.
104
purpose of cholesterol
a steroid and is only found in animal cell membranes. This is vital in helping to maintain the structure of the cell membrane
105
what to remember when drawing fluid mosiac models
Individual phospholipid molecules are shown by using the symbol of a circle with two parallel lines attached.
A range of membrane proteins is shown, including peripheral and integral.
The following labels are included: phospholipid bilayer, phospholipid molecule, glycoprotein, glycolipid, integral and peripheral proteins and cholesterol.
106
According to the fluid mosaic model of cell membranes, which type of molecule spans the membrane, from its inner to outer surface?
integral proteins
107
is cholesterol in plants or animals
exclusvely in animals
108
purposes of cholesterol
function
some hormones are synthesised from chlesterol
109
what is cholesterol mad eup of
a non-polar part comprising four ring structures, a hydrocarbon tail, and a polar hydroxyl group (hydrophilic) (see Figure 1). Since it has both a hydrophilic and a hydrophobic region, it is considered an amphipathic molecule.
110
which property allows cholesterol to insert itself into cell membranes by interacting with the phospholipids
it is amphipathic
111
role of cholesterol
controlling membrane fludiity and permeability to some solutes.
it restricts the movement of phospholipids and other molecules, thus reducing membrane fluidity.
at low temperatures, it also disrupts the regular packing of the hydrocarbon tails of phospholipid molecules, which prevents the solidification of the membrane.
This enables the membrane to stay more fluid at lower temperatures, allowing the membrane to function properly.
Additionally, it reduces membrane permeability to hydrophilic molecules and ions such as sodium and hydrogen.
112
cholesterol, phospholipids, integral proteins are all
amphipathic
113
davson and danelli model
1935.
suggested that the cell membrane comprises a lipid bilayer where two layers of polar lipid molecules are arranged with their hydrophilic heads outward. The lipid bilayer is itself sandwiched between two protein layers on either side of the membrane
114
evidence for davson daneilli
evidence obtained from electron microscopy which showed the membrane as having three layers (see Figure 2). In high magnification electron micrographs, membranes appeared as two dark parallel lines with a lighter-coloured region in between. Since proteins normally appear dark in electron micrographs and phospholipids appear lighter, it was deduced that membranes comprised two protein layers, one on either side of a phospholipid core.
115
shortcomings of davson danelli
It assumed that all membranes had identical structures, which did not explain how different types of membranes could carry out different functions.
Proteins are amphipathic, though largely non-polar (hydrophobic), which makes it improbable that they would be found in contact with the aqueous environment on either side of the membrane.
116
how did the fluid mosiac model adddress the shortcomings of davson danelli
The new model suggested that proteins are individually embedded in the phospholipid bilayer, rather than coating it on both sides. This allowed the hydrophilic portions of both proteins and phospholipids to be maximally exposed to water, resulting in a stable membrane structure. At the same time, it ensured that hydrophobic portions of proteins and phospholipids were in the non-aqueous environment inside the bilayer
117
how else was the fluid mosiac moel confirmed
freeze fracture techniques. biologists delaminated (separated) membranes along the middle of the bilayer. When viewed with an electron microscope, the fracture revealed an irregular rough surface inside the phospholipid bilayer (Figure 3). The globular structures appearing on the fractured surface were interpreted as trans-membrane proteins (that span the whole membrane) and it was deduced that proteins penetrate into the hydrophobic interior of the membrane.
Further studies treated the membranes to chemicals that removed almost 70% of the protein membranes. Freeze fracture then showed a smoother lipid bilayer as many of the integral proteins had been removed. The development of the MRI machine, which uses magnetic fields to study molecules, showed that the proteins in the cell membrane could move around. This was only possible with the fluid mosaic model, as the Davson–Danielli model made movement of proteins impossible, as the protein was one layer.
118
When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are:
integral proteins
119
Which of the following statements correctly describe the Davson–Danielli model?
It comprises a lipid bilayer sandwiched between two protein layers on either side of the membrane.
120
define diffusion
the movement of particles from a region of high concentration to a region of low concentration, and is the result of the random motion of particles.
121
simple diffusion
occurs in a gas or liquid medium and only requires a concentration gradient.
122
what affects diffusion
temperature
surface area of membrane
size of particles
concentration gradient of diffusing particles
123
facilitated diffusion
if a particle is too big, it cannot pass through the phospholipid bilayer of the membrane. Similarly, charged particles (ions) are repelled by hydrophobic tails in the membrane. the proteins can aid its movement
124
what is the key difference in simple and facilitated diffusion
facilitated diffusion requires channel or carrier proteins that are specific to the molecules being transported across the plasma membrane
125
types of facilitated diffusion
channel protein opens to let a substance through and then closes.
carrier protein alternates between being open to outside and then inside.
126
application of facilitated diffusion is
the movement of K+ ions in neurons during the generation of an action potential (a key step in the propagation of nerve impulses along neurons). they are voltage gated.
127
define osmosis
the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane.
128
in medical procedures, tissues need to be kept
in a saline solution for storage
129
The solution with the higher concentration of solutes is called the
hypertonic solution
130
the solution with the lower concentration of solutes is called the
hypotonic solution.
131
Water always moves by osmosis from the ??? solution to the ??? solution.
hypotonic to hypertonic
132
what is active transport
the movement of particles across membranes, requiring energy in the form of ATP
low to high concentration
133
when is active transport useful
when some minerals may not be in enough concentration to diffuse into the cells of roots. when a high conc is needed (high conc of glucose in epithelial cells that allows glucose to diffuse into the blood
134
how does active transport in sodium potassium pumps be summarised
When the pump is open to the inside of the axon, three sodium ions (Na+) enter the pump and attach to their binding sites.
ATP donates a phosphate group to the pump.
The previous stage causes the protein to change shape expelling Na+ to the outside.
Two potassium ions (K+) from outside then enter and attach to their binding sites.
The binding of the K+ leads to the release of the phosphate which causes the pump to change shape again so that it is only open to the inside of the axon.
K+ is released inside.
Na+ can now enter and bind to the pump again.
135
endocytosis
when cells take in molecules or substances
136
exocytoiss
ejection of waste products or useful substances
136
endocytosis can be divided into
phagocytosis or pinocytosis
137
pinocytosis
taking in of liquid substances by cells
138
phagocytosis
absorption of solids
139
phago/pino cytosis
140
what can exocytosis be divided into
excretion and secretion.
141
secretion
Proteins synthesised by ribosomes on rough endoplasmic reticulum are first passed to the Golgi apparatus via vesicles, where they are processed and packaged (to give the enzymes or hormones the correct conformations) before being released in vesicles that in turn fuse with the plasma membrane for secretion outside the cell
142
importance of vesicles
enzymes may be made by bound ribosomes in the rough endoplasmic reticulum
exocytosis
143
What is the correct order of destinations of a protein undergoing exocytosis?
Ribosomes on rER, Golgi apparatus, Vesicles fusing with plasma membrane.
144
Osmolarity
refers to the concentration of a solution in terms of moles of solutes per litre of solution.
145
when is the isotonic point
when concentrations inside and outside are equal so the net movement of water is zero
146
In a hypotonic solution, the higher salt concentration is inside the potato cell and water enters the potato,
causing an increase in mass.
147
In a hypertonic solution, the higher salt concentration is outside the potato, so water leaves the potato and causes a
negative change in mass.
148
variables in the estimation of osmolarity of tissues
independent variable: conc of solution
dependent var: percent change in mass
controls: Number of trials
Size of the plant tissue
Time in solution
Age of the plant tissue
Same temperature
149
who disproved spotnaneous generation
louis pasteur
150
how did pasteur disprove spontaneous generation
three swan neck flasks
one neck broken
the broth in the first remained clear the other became cloudy.
in the third, he tilted the broth to expose them to the microbes in the curve of the swan neck.
151
what did miller urey prove
that non living synthesis of simple organic molecules was possible
152
describe the miller urey experiment
Miller and Urey recreated the conditions of early Earth in a closed system (Figure 2) by including a reducing atmosphere (low oxygen) with high radiation levels, high temperatures and electrical storms. After running the experiment for a week, some simple amino acids and complex oily hydrocarbons were found in the reaction mixture.
153
what are the condiitons for the emergence of life
1. Simple organic molecules, such as amino acids, fatty acids and carbohydrates, must be formed.
2. Larger organic molecules, such as phospholipids, RNA and DNA, must be assembled from simpler molecules.
3. Organisms reproduce, so replication of nucleic acids must be possible.
4. Biochemical reactions require set conditions, such as pH. Therefore, self-contained structures, such as membranes, are necessary.
154
evidence for endosymbiotic theory
Have double membranes, as expected for cells taken in by endocytosis. (see Figure 1 below)
Have circular naked DNA, as in prokaryotes.
DNA is formed as single chromosomes.
Have 70S ribosomes, as in prokaryotes.
Divide by binary fission like prokaryotic cells.
Are susceptible to some antibiotics.
155
interphase
is the most active and longest phase of the cell cycle. cells spend most of their life within this stage undergoing common cell processes such as metabolism, endocytosis, exocytosis and using and obtaining nutrients.
156
activities occfuring in G1
The cell grows and functions normally undergoing everyday processes.
Rapid protein synthesis takes place allowing the cell to grow in size.
Proteins required for DNA synthesis (the next phase) are made.
Mitochondria and chloroplasts (in the case of plant cells) are replicated. This also continues in S phase.
157
activites occuring in S phase
The amount of DNA doubles as DNA replication takes place.
The genetic material is duplicated but no chromosomes are formed yet.
158
activites occuring in G2 phase
Protein synthesis occurs to produce the proteins needed for cell division, such as microtubule proteins that will make up a mitotic spindle. The cell is actively preparing for cell division.
159
where does G1 take place
cytoplasm
160
where does S take place
nucleus
161
where does G2 take place
cytoplasm
162
what is mitosis
he division of the nucleus into two genetically identical daughter nuclei. It involves the separation of sister chromatids into individual chromosomes which are then distributed among the daughter nuclei.
163
what is cytookinesis
the cytopplasm of a parental cell divides between the two daughter cells.
164
what are cyclins
a family of proteins that control the progression of cells through the cell cycle
165
how are cells controlled in thier entry to the next stage
Cells cannot progress to the next stage of the cell cycle unless the specific cyclin reaches a certain concentration.
166
what do cyclins do
bind to enzymes called cyclin-dependent kinases (CDKs) and activate them. The activated CDKs then attach phosphate groups (phosphorylation) to other proteins in the cell. The attachment of phosphate triggers the other proteins to become active and carry out tasks; in this case, specific to the phases of the cell cycle.
167
cyclins at G1
During this phase cyclin D (red line) levels gradually increase.
168
cyclins at S
Cyclin E (purple line) is instrumental to DNA replication and also promotes centromere duplication.
169
cyclins at G2
Cyclin A (blue line) helps induce DNA replication.
170
cyclins at mitosis
Cyclin B (yellow line) is essential for the formation of mitotic spindles and the alignment of chromatids.
171
in eukaryoitc cells, how is the division of the nucleus carried out
dna replicated in s phase is seperated through the formation of chromosomes
172
describe eukaryotic chromosomes
consist of DNA which is tightly wound around proteins called histones
173
what are histones
basic (alkaline) proteins that form part of nucleosomes. many nucleosomes are coiled together in a specific pattern to form a chromoosme
174
show the relationship between a double-stranded DNA molecule (the double helix) and histones
175
dna is is initally packaged by histones to form...
chromatin
176
when is dna chromatin
interphase
177
when is dna sister chromatids
Following prophase, the phase when DNA supercoiling takes place, the DNA is visible as a pair of sister chromatids that are identical to each other connected by a centromere.
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when is dna chromosomes
after sister chromatids are seperated during anaphase
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events in prophase
DNA supercoils causing the chromatin to condense.
Nucleolus disappears.
Nuclear membrane disintegrates.
Spindle fibres (made of microtubules) start to form (and are completely formed by the end of prophase).
Centrioles (absent from plant cells) move to opposite poles.
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events in metaphase
Spindle fibres bind to the centromere of sister chromatids and cause their movement towards the equatorial plate.
Sister chromatids are aligned at the equatorial plate at the end of metaphase.
181
events in anaphase
Sister chromatids are separated (now known as chromosomes) and pulled to opposite poles by the spindle fibres.
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events in telophase
The chromosomes have reached the poles.
A nuclear membrane starts to reform at each pole.
A nucleolus appears in each new nucleus.
The spindle fibres disintegrate.
The cell elongates in preparation for cytokinesis.
In some cases, the invagination of the membrane is also visible (marking the beginning of cytokinesis).
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identification of the different stages of mitosis
184
what is the mitotic index
PMAT / total cells
185
why is the mitotic index important
it indicates how many cells in a tissue are dividing at a given time. We can therefore use the mitotic index to predict how quickly a cancer could spread and the likely outcome in reducing cell proliferation of any treatment, such as chemotherapy.
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What ensures that mitosis produces two genetically identical nuclei?
Sister chromatids are pulled apart and moved to opposite poles by spindle fibres.
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how do animal cells undergo cytokinesis
A ring of protein (microfilaments) located immediately beneath the plasma membrane at the equator pulls the plasma membrane inward.
The inward pull on the plasma membrane produces the characteristic cleavage furrow.
When the cleavage furrow reaches the centre of the cells, it is pinched apart to form two daughter cells.
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how do plant cells undergo cytokiniesis
In plants Golgi apparatus forms vesicles that consist of material to build a new cell wall. Vesicles merge and form the cell plate. The cell plate grows and divides into two daughter cells.
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a benign tumor
usually localised, and does not spread to other parts of the body. Most benign tumors respond well to treatment.
190
a malignant tumour
a cancerous growth that is often resistant to treatment. It may spread to other parts of the body and sometimes recur after it has been removed.
191
when might a tumour form
a mutation in a cyclin, cdk or protein
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what is a mutation
a change in an organism’s genetic code. A change in the base sequence of a certain gene can result in tumour formation (or not)
193
example mutagens
Chemicals that cause mutations that are referred to as carcinogens, such as asbestos or dioxin.
High-energy radiation, such as X-rays.
Short-wave ultraviolet light.
Some viruses such as hepatitis B.
194
what is an oncogene
a gene that has undergone a mutation that will contribute to the development of a tumour.
195
In their normal, non-mutated state, oncogenes are termed what?
proto-oncogenes. These proto-oncogenes then assist in the regulation of cell division.
196
metastatisis
Cancerous cells detach from the primary tumour.
Some cancerous cells gain the ability to penetrate the walls of lymph or blood vessels and so circulate around the body.
The circulating cancerous cells invade tissues at different locations and develop, by uncontrolled cell division, into secondary tumours.
197
define metastatis
the movement of cells from a primary tumour to other parts of the body where they develop into secondary tumours.
198
issues associated with smoking
cancer, asthma, stroke
199
proving cons of smoking
Initially, research established a strong correlation, but this did not prove that smoking was the cause of the cancers. Over many years of study, causal relationships between some of the compounds in cigarette smoke and tumorigenesis were established. Only then did the tobacco industry grudgingly admit that the link existed.
positive correlation
