Topic 2 - Cells and Control Flashcards
1
Q
what are chromosomes?
A
coiled up lengths of DNA molecules
2
Q
what are cells called when they have two copies of each chromosome?
A
diploid
3
Q
what are cells called when they have one copy of each chromosome?
A
haploid
4
Q
when a cell divides by mitosis what is produced?
A
two cells identical to the original cell, the nucleus of each new cell contains the same number of chromosomes as the original cell
5
Q
what is mitosis?
A
the stage of the cell cycle when the cell divides is mitosis, body cells in multi-cellular organisms divide to produce new cells during the cell cycle
6
Q
why do multi-cellular organisms need mitosis?
A
growth, replacement of worn out cells, repair of damaged tissue, asexual reproduction
7
Q
how do strawberry plants asexually reproduce by mitosis?
A
the strawberry plants form runners by mitosis which become new plants
8
Q
what are the stages of mitosis in order and what is an acronym to remember them by?
A
IPMATC
Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
9
Q
what is asexual reproduction?
A
when a single-celled organism can reproduce without the joining of male and female gametes.
10
Q
what happens interphase in mitosis?
A
the DNA in the nucleus duplicates so that there is one copy of the DNA for each new cell
11
Q
what happens in prophase in mitosis?
A
- the centriole doubles and moves to the poles of the cell - the centriole is represented in diagram as the letter ‘T’,
- the chromosomes condense and get shorter and thicker,
- the nuclear membrane breaks down so the chromosomes lie in the cytoplasm.
12
Q
what happens in metaphase in mitosis?
A
the chromosomes line up on the equator of the cell and the centrioles attach spindle fibres to the centrometres of the chromosomes.
13
Q
what happens in anaphase in mitosis?
A
the spindle fibres pull the chromosomes apart and reel in the chromatids (the different arms of the chromosome) to the centrioles (opposite ends of the cell)
14
Q
what happens in telophase in mitosis?
A
nuclear membranes reform around each new set of chromosomes and these become the nuclei of the two new cells
15
Q
what happens in cytokinesis in mitosis?
A
the cytoplasm and cell membrane divide to form two separate cells. these two cells are called daughter cells which are genetically identical diploid cells and which are genetically identical to the parent cell
16
Q
how can you work out the number of cells there will be after multiple divisions of a cell by mitosis?
A
number of cells = 2^n , where n is the number of divisions by mitosis
17
Q
what is growth?
A
growth is an increase in size or mass
18
Q
what is cell differentiation?
A
the process by which a cell changes to become specialised for its function
19
Q
how do plants grow?
A
by cell elongation
20
Q
what is cell elongation?
A
when a cell elongates which results in growth e.g. a plant cell expands making the cell bigger and so making the plant grow
21
Q
by what process does all growth in animals happen?
A
cell division
22
Q
how does cell division result in growth in animals?
A
animals grow whilst they are young and then they reach full growth and stop growing, when animals are young cells divide at a fast rate but once an adult, cell division is mostly for repair - to replace old or damaged cells. so in most animals cell differentiation is lost at an early stage
23
Q
growth in plants is mainly due to what process?
A
cell elongation
24
Q
where is cell division used for growth in plant cells?
A
in the tips of the roots and shoots in meristems
25
how is plant growth different to animal growth?
plants often grow continuously so they continue to differentiate to develop new parts, but animals stop growing once adults so cell differentiation is lost at an early stage
26
what is the rate at which cells divide by mitosis controlled by?
chemical instructions - genes in an organism's DNA
27
what is cancer?
an uncontrolled cell division
28
what is a tumour?
a mass of abnormal cells
29
when is a tumour considered cancerous?
when the tumour invades and destroys surrounding tissue
30
how does cancer start?
if there's a mutation in one of the genes which controls cell division, the cell may begin dividing uncontrollably
31
what are percentile charts used for?
to monitor growth
32
why are growth charts used to assess a child's growth over time?
so that an overall pattern in development can be seen and any problems such as obesity, malnutrition or dwarfism can be highlighted
33
what three measurements are taken of a baby to monitor its growth after birth to make sure that it is growing normally?
length, mass and head circumference
34
when are doctors likely to investigate a baby's growth after using a percentile growth chart?
if the baby's size is above the top percentile, below the bottom percentile, if the baby's size increases or decreases by two or more percentile lines over time, or if there's an inconsistent pattern (e.g. a small baby with a very large head.)
35
what are undifferentiated cells called?
stem cells
36
where are stem cells found?
in early human embryos and bone marrow.
37
how are embryonic stem cells different to adult stem cells?
* embryonic stem cells have the potential to divide and produce any type of cell because all of the different types of cells found in humans come from these stem cells,
* adult stem cells are only found in certain plaques such as bone marrow and can only produce certain types of cells because adult stem cells are used out replace damaged cells e.g. to make new skin or blood cells.
38
what are stem cells really important for?
the growth and development of organisms
39
what are meristems?
meristems contain plant stem cells and are the only cells which divide by mitosis in plant tissues
40
where are meristems found in plants?
in the areas of a plant that are growing, e.g. the tips of the roots and shoots
41
what are meristems used for in plants?
meristems produce unspecialised cells that are able to divide and form any cell type in plants - they act like embryonic stem cells but they can divide and differentiate to make any type of cell for as long as the plant lives. meristems are used to produce specialised tissues such as the xylem and phloem
42
how are adult stem cells already used to cure some diseases?
sickle cell anaemia can sometimes be cured with a bone marrow transplant because the stem cells produce new blood cells
43
give an example of how could it be possible to use stem cells to replace those damaged by disease or injury
new cardiac muscles could be transplanted into someone with heart disease
44
what are some of the potential risks with stem cells?
tumour development, disease transmission, rejection
45
who is tumour development a risk with stem cells?
stem cells divide very quickly and if scientists are unable to control he rate at which the transplanted cells divide inside a patient then a tumour may develop
46
how is disease transmission a risk with stem cells?
viruses live inside cells and if donor stem cells are infected with a virus and this isn't notices then the virus could be passed on to the recipient and therefore make them more ill
47
how is rejection a risk with stem cells?
if the transplanted cells aren't grown using the patient's own stem cells then the patient's body may recognise the cells as foreign and trigger an immune response to try to remove them, the patient could take drugs to suppress rejection but this makes them susceptible to diseases
48
what ethical issues does research using embryonic stem cells raise?
some people argue that human embryos shouldn't be used for experiments because each one is a potential human life but others think that the aim of curing patients who are suffering should be more important than the potential life of the embryos
49
what does totipotent mean?
a cell can differentiate into any type of cell and eventually produce a whole organism (embryonic stem cells)
50
what does pluripotent mean?
cells can differentiate into any type of tissue but not whole organisms
51
what does multipotent mean?
cells can only form a few types of tissue, e.g. haematopoetic stem cells in bone marrow can form types of blood cells
52
what makes up the central nervous system (CNS)?
the brain and the spinal cord
53
what is the spinal cord?
the spinal cord is a long column of neurones (nerve cells) that run from the base of the brain down to the spine. at several places down the cord, neurones branch off and connect with other parts of the body.
54
what does the spinal cord do?
it relays information between the brain and the rest of the body.
55
what is the brain made up of?
billions of interconnected neurones
56
why are the structures in the brain?
the cerebrum, the cerebellum, the medulla oblongata, the hypothalamus, the pituitary gland
57
what is the function of the cerebrum?
the cerebrum is the largest part of the human brain and is divided into two halves called the cerebral hemispheres. the right hemisphere controls muscles on the left side of the body and the left hemisphere controls muscles on the right side of the body.
the cerebrum is responsible for movement, intelligence, memory, language and vision.
58
what is the function of the cerebellum?
responsible for muscle coordination and balance
59
what is the function of the medulla oblongata?
controls unconscious activities such as breathing and heart rate
60
what is the function of the hypothalamus?
controls most of the body's homeostatic mechanisms. regulates body temperature and regulates the pituitary gland
61
what is the function of the pituitary gland?
releases hormones
62
what are the two ways in which the brain can be visualised without surgery?
CT scanning and PET scanning
63
what is CT scanning and how is it used?
a CT scanner uses x-rays to produce an image of the brain, it shows the main structures of the brain but not the functions of them. However, the function of parts of the brain can be worked out, for example if a CT scan shows a diseased or damaged brain structure and the patient has lost some function then that part of the brain is responsible for that function.
64
what is PET scanning and how is it used?
PET scanners use radioactive chemicals to show which parts of the brain are active when the person is inside the scanner. PET scans are very detailed and can investigate the structure and function of the brain in real time. PET scans can also show if areas in the brain are unusually inactive or active so are useful for studying disorders that change the brain's activity.
65
what are some things which can go wrong with the Central nervous system?
injuries to the brain, injuries to the spinal cord, tumours and diseases (e.g. Alzheimer's and Parkinson's disease)
66
why is it difficult to treat problems in the central nervous system?
* it's hard to repair damage to the CNS because neurones in the CNS don't repair themselves and scientists haven't developed a way to repair nervous tissue in the CNS yet
* if a problem occurs in a part of the CNS that's not easy to access it can be hard to treat (e.g. some tumours cant be removed in certain parts of the brain.)
* treatment for problems in the CNS could lead to permanent damage, e.g. surgery on the spinal cord could damage the spinal cord further and lead to permanent damage.
67
what is the nervous system made up of?
neurones
68
what are neurones?
nerve cells which go to all parts of the body
69
what are sensory receptors?
groups of cells that can detect a change in environment (a stimulus)
70
what do receptors in the eyes detect?
light
71
what do receptors in the skin detect ?
touch (pressure) and temperature change
72
what happens when a stimulus is detected by receptor?
- the information is converted to a nervous (electrical) impulse)
and is sent along sensory neurones to a relay neurone in the central nervous system
- the CNS coordinates the response and impulses travel through the CNS along relay neurones
- when the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger neurotransmitters to be released, causing impulses to be sent along the relay neurone
- when the impulses reach a synapse between the relay neurone and motor neurone, they trigger neurotransmitters to be released, causing impulses to be sent along the motor neurone.
- the impulses then travel along the motor neurone to the effector (a muscle or gland)
- the effector then responds (muscle contracts) and moves away from the hazard.
73
what is an example of an effector?
muscle or gland
74
what is the time taken to respond to a stimulus called?
reaction time
75
what do all neurones have?
a cell body, a nucleus, and a cytoplasm and other subcellular structures
76
what is the function of dendrites and dendrons?
carry nerve impulses towards the cell body
77
In neurones what are the extensions from the cell body that connect to other neurones?
Dendrites (the ends of dendrons), dendrons and axons
78
What is the function of axons?
Carry nerve impulses away from the cell body
79
What are some axons surrounded by?
A myelin sheath
80
What is the function of a myelin sheath in neurones?
Acts as an electrical insulator to speed up the electrical impulse.
81
How can neurones be adapted to increase the speed of the electrical impulse?
* axon surrounded by myelin sheath
| * the neurone being very long
82
Why does a neurones being very long increase the speed of the electrical impulse?
Connecting with neurones decreases (slows down) the speed of the electrical impulse so one long neurone carries the electrical impulse more quickly than many short neurones connected together.
83
What is the structure of a sensory neurone?
* Receptor cells are connected to one long dendron, the long dendron carries nerve impulses from the receptor cells to the cell body which is located in the centre (middle) of the neurone.
* One short axon carries nerve impulses from the cell body to the CNS.
84
What is the structure of a motor neurone?
* Many short dendrites carry nerve impulses from the CNS to the cell body, the cell body is at the end of the neurone and is surrounded by the dendrites.
* one long axon carries nerve impulses from the cell body to the effector cells.
85
What is the structure of a relay neurone?
* many short dendrites carry nerve impulses from sensory neurones to the cell body. Dendrons extend from the cell body, ending in the dendrites which connect to the sensory neurones.
* an axon carries nerve impulses from the cell body to motor neurones
86
What is a synapse?
The connection between two neurones
87
How are nerve signals transmitted from one neurone to another by synapses?
* the nerve signal is transferred by neurotransmitters (chemicals), the neurotransmitters diffuse across the gap.
* the neurotransmitters then set off/trigger a new electrical signal in the next neurone
88
Why is the transmission of a nervous impulse slowed down across a synapse?
Because the diffusion of neurotransmitters across the gap takes time
89
What are reflexes?
Automatic, rapid responses to stimuli
90
What is the function of reflexes?
To reduce the chances of being injured
91
What is the passage of information in a reflex from receptor to effector called?
A reflex arc
92
In reflex arcs where do the neurones go through?
The spinal cord or an unconscious part of the brain
93
Why is a response in the reflex arc quicker than normal responses?
Time isn't spent thinking about the response - reaction time isn't a factor
94
How is a reflex used to protect eyes from bright light?
* light receptors in the eye detect very bright light and send a message along a sensory neurone to the brain.
* the message then travels along a relay neurone to a motor neurone, telling the circular muscles in the iris to contract, making the pupil smaller.
95
What is the function of the cornea?
Refraction (bending) light into the eye
96
What is the function of the iris?
Controlling how much light enters the pupil
97
What is the pupil?
The hole in the middle of the eye
98
What is the function of the lens?
Refracting light to focus light onto the retina
99
What is the retina?
The light sensitive part of the eye
100
What is the function of the retina?
To detect light (covered in rods and cones which detect light)
101
What is the function of rods in the eye?
Sensitive in dim light but can't sense colour
102
What is the function of cones in the eye?
Sensitive to different colours but not good in dim light
103
What is the function of the optic nerve?
Carrying the electrical impulses (information from light is converted into electrical impulses) from the receptors to the brain.
104
Why is the lens elastic?
So the eye can focus light onto the retina by changing there shape of the lens
105
How does the eye adapt to look at distant objects?
* the ciliary muscle relaxes, allowing the suspenseful ligaments to pull tight.
* this pulls the lens into a less rounded shape so light is refracted less
106
How does the eye adapt to look at close objects?
* the ciliary muscle contracts, slackening the suspensory ligaments
* the lens then becomes a more rounded shape so light is refracted more
107
What are long-sighted people unable to focus on?
Near objects
108
When does long-sightedness occur?
When the lens is the wrong shape and doesn't refract the light enough or when the eyeball is too short.
109
Where is light brought into focus in long-sighted people?
Behind the retina
110
What type of lens can correct long-sightedness?
A convex lens
111
What are short-sighted people unable to focus on?
Distant objects
112
When does short-sightedness occur?
When the lens is the wrong shape and refracts light too much or when the eyeball is too long
113
Where is light from distant objects brought into focus in short-sighted people?
In front of the retina
114
What type of lens can correct short-sightedness?
A concave lens
115
What is the issue with colour blind people?
They can't tell the difference between certain colours
116
What is the most common form of colour blindness?
Red-green colour blindness
117
How is red-green colour blindness caused?
When red or green cones in the retina don't work properly
118
Is there a cure for colour blindness? Why/how?
No, because the cone cells can't be replaced
119
What is a cataract?
A cloudy patch on the lens, which stops light from being able to enter the eye normally.
120
What are people with cataracts likely to experience?
Blurred vision, colours looking less vivid, difficulty seeing in bright light.
121
Can a cataract be treated? Why/how?
Yes, by replacing the faulty lens with an artificial lens
122
What is the cell cycle?
When body cells in multicellular organisms divide to produce new cells, this process is the cell cycle
123
In a cell that is not dividing, how is the DNA spread out?
In long strings of chromosomes
124
Before a cell divides by mitosis, what does it have to do?
Grow and increase the amount of subcellular structures, e.g. mitochondria and ribosomes. The cell also has to duplicate the DNA so there is one copy for each new cell.
125
When the DNA is copied in interphase, what does the DNA form?
X-shaped chromosomes, each arm (chromatid) of the chromosome is an exact duplicate of the other
126
What is a mutation?
A random change in a gene
127
What are some diseases which can affect the CNS?
Alzheimer's and Parkinson's disease
128
What does totipotent mean?
Can differentiate into any type of cell and eventually produce a whole organism (embryonic stem cells)
129
What does pluripotent mean?
Can differentiate into any type of tissue but not whole organisms (in early embryos)
130
What does multipotent mean?
Can only form a few types of tissue, stem cells in bone marrow
131
What is the name of the stem cells in bone marrow that can form types of blood cells?
Haematopoetic stem cells
132
What is the peripheral nervous system (PNS)?
Consists of motor and sensory neurones, the nervous systems outside the CNS (brain and spinal cord)
