Topic 2 - Cells and control Flashcards
(89 cards)
1
Q
What are the stages of cell cycle
A
- Stage 1 - Interphase
- Stage 2 - Mitosis
- Stage 3 - Cytokinesis
2
Q
What is interphase
A
Longest stage of cell cycle that involves cell growth, synthesis of new organelles and DNA replication
3
Q
What is mitosis
A
Division of a cell to produce two daughter cells each with identical sets of chromosomes in nucleus to parent cell and results in formation of two genetically identical diploid body cells
4
Q
What is purpose of mitosis in organisms
A
- Growth
- Repair
- Asexual reproduction
5
Q
What are the 4 stages of mitosis
A
- Prophase
- Metaphase
- Anaphase
- Telophase
PMAT
6
Q
What happens in prophase
A
- DNA condenses, chromosomes become visible
- Nuclear membrane disappears
7
Q
What happens in metaphase
A
- Chromosomes line up along cell equator
- Spindle finres attach to chromosomes at centromere
8
Q
What happens in anaphase
A
- Spindle fibres attach to each chromosome
- Chromatids are pulled to edges of cell by spindle fibres
9
Q
What happens in telophase
A
- Nucleus of cell divides
- New membrane forms around each set of chromosomes seperating them from one another
10
Q
What happens in cytokenisis
A
- Division of cell membrane and cytoplasm
- Two genetically identical ‘daughter’ cells produced
11
Q
A cell divides by mitsois once every 2 minutes.
Calculate number of identical cells present after 10 minutes
A
- 10 / 2 = 5
- 5 cell divisions have taken place
- 25 = 32 cells
12
Q
What is cancer
A
Uncontrolled cell division
13
Q
Describe how stages of mitsis result in formation of two diploid cells
A
Prophase
* DNA condenses, chromosomes become visible
* Nuclear membrane disappears
Metaphase
* Chromosomes line up along cell equator
* Spindle finres attach to chromosomes at centromere
Anaphase
* Spindle fibres attach to each chromosome
* Chromatids are pulled to edges of cell by spindle fibres
Telophase
* Nucleus of cell divides
* New membrane forms around each set of chromosomes seperating them from one another
Cytokenisis
* Division of cell membrane and cytoplasm
* Two genetically identical ‘daughter’ cells produced
14
Q
Describe growth in animals
A
- Cell division occurs in all body cells. Occurs at slower rate in adults than in younger animals as growth stops and cell division only required for replacement and repair
- Most cells differentiate at early stage and become specialised. Some adult stem cells retain their ability to differentiate
15
Q
Describe growth in plants
A
- Cell division can only occur in meristematic tissue Rate of cell division remains same throughout plant’s life
- Meristematic stem cells can differentiate into any cell type as long as plant lives
- Cell elongation occurs in all cells. Cells expand and enlarge growth of plant
16
Q
What is meant by ‘differentiation’
A
- Process by which stem cells become specialised (have specific function)
- Some genes switch on or off, determining cell type
17
Q
Why is cell differentiation important
A
Enables formation of specialised tissues with specific functions e.g. muscle tissue
18
Q
What are percentile charts
A
- Charts used to monitor growth
- Measurements (e.g. fetal length or head circumference) can be compared to expected values at certain age
19
Q
What does 95th percentile mean
A
- 95% of measurements will be below the value of 95th percentile
- 5% of measurements will be above value of 95th percentile
20
Q
What are stem cells
A
Cells that are unspecialised and capable of differentiating into range of different cell types
21
Q
What are embryonic stem cells
A
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
22
Q
What is function of embryonic stem cells
A
Enable growth and development of tissues in human embryos
23
Q
What are adult stem cells
A
Stem cells that can differentiate into limited range of cell types e.g. bone marrow stem cells
24
Q
What is primary function of adult stem cells
A
Replacement of dead cells e.g. replacement of red blood cells which only live for 120 days
25
Where are stem cells found in plants
Meristems
26
Where is meristem tissue found
Regions of plant where cells are continuosly dividing e.g. root tips, shoot tips
27
What are meristematic stem cells
Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during life of plant
28
How can stem cells be used in medicine
* Stem cells collected
* Stem cells stimulated to differentiate into specific cell types e.g. heart muscle cells
* Specialised cells transplanted into patient
* Used to treat damage or disease e.g. heart disease
29
Where can embryonic stem cells be collected from
* Donor stem cells removed from embryos grown in vitro
* Patient's own stem cells removed from the umbilical blood after birth
30
What are benefits of using stem cells in medicine
* Treat damage or disease e.g. heart disease, type 1 diabetes
* Treat diseases that would otherwise be untreatable
* Used in scientific research
* Growing organs for transplants
31
What are risks of stem cells use in medicine
* Transplanted stem cells could cause tumours
* Finding suitable stem cell donors is difficult task
* Stem cells may be rejected by body (immunosuppressants taken)
* Potential side effects
* Long term risks of using stem cells unknown
* Stem cells may become contaminated during preparation and when transplanted transmit infections to plany, making them sicker
32
What are ethical issues related to use of stem cells in medicine
* Embryos were used to provide stem cells are destroyed which is seen as unethical and waste of potential human life
* May lead to reproductive cloning of humans
33
Describe the structure of brain
Consists of three main regions:
* Cerebral hemispheres
* Cerebellum
* Medulla oblongata
34
Describe structure of cerebral hemispheres
* Largest region of brain
* Divided into two hemispheres
35
What is function of cerebral hemispheres
* Intelligence
* Thought
* Language
* Memory
* Emotion
* Visual and sensory processes
| Conscious actions
36
What is function of each cererbral hemisphere
* Left hemisphere receives sensory information from right side of body and controls muscle coordination on right
* Right hemisphere receives sensory information from left side of body and controls muscle coordination on left
37
Where is cerebellum located
Lower region of brain
38
What is function of cerebellum
Involved in:
* Coordination of muscles
* Voluntary movement e.g. walking
* Non-voluntary movement e.g. balance
| Movement and coordination
39
What is function of medulla oblongata
Controls automatic processes in body e.g. breathing rate, heart rate
| Unconcscious activities
40
What methods are used by doctors to observe brain
* PET scans
* CT scans
41
What is a CT scan
Procedure that uses X-rays to produce 3D cross-sectional images of brain
42
Describe how CT scans are useful to investigate brain function
* CT scans show damaged regions of brain e.g. areas of swelling, bleeding
* Observations of patient's symptoms can enable scientists to determine function of damaged region
43
What does a PET scan involve
* Radioactive substance injected into patient's bloodstream and taken up by tissues in brain
* Radiation emitted by tissues detected, enabling identification of active and inactive regions of brain
44
Describe how PET scans are useful to investigate brain function
* Show which areas of brain are active and which areas are not
* Comparisons of brain activity in healthy patients and patients with brain damage allow scientists to determine functions of inactive regions
45
Why is it difficult to treat damage to CNS
* Damage to neurones is permenant and can't ne repaired
* Hard to reach some areas of brain
* Risk of further permanent damage to other areas of CNS during surgery
46
What are the parts in central nervous system (CNS)
Brain & Spinal cord
47
What is spinal cord
Long thin structure composed of neurones that extends from medulla oblongata down to spine
48
What is function of spinal cord
Connects peripheral nervous system (nerves outside of CNS) to brain
49
What is the function of nervous system and reflex arc
Allows organism to rapidly react to environmental and internal changes
50
What is function of sensory neurone
Carries impulses from receptors to central nervous system
51
What is the structure of sensory neurone
* Long dendron carries impulses from receptors to cell body
* Cell body found part way along neurone
* Short axon carries impulses from cell body to CNS
52
What is the function of a motor neurone
Carries impulses from CNS to effectors
53
What is the structure of motor neurone
* Short dendrites carry impulses from CNS to cell body
* Cell body found at one end of neurone
* Long axon carries impulses from cell body to effectors
54
What is the function of a relay neurone
Carries impulses from sensory neurones to motor neurones within CNS
55
What is the structure of relay neurone
* Short dendrites carry impulses from sensory neurones to cell body
* Short axon carries impulses from cell body to motor neurones
56
What is the function of axon
* Carries impulse away from cell body
* Enables transmission of nerve impulses over long distances
57
What is function of dendrites and dendrons
* Carry impulse towards cell body
* Dendrites provide large surface area to receive impulses
58
What is role of myelin sheath
* Electrically insulating layer
* Surrounds axon and increases speed of impulses
59
Describe how CNS coordinates response to stimulus
| REFLEC ARC
* Sensory receptor detects stimulus
* Sensory receptor sends impulses along sensory neurone to CNS
* CNS coordinates response
* CNS sends information to effector along motor neurone
* Effector produces response to stimulus
60
What is a synapse
Small gap between neurones across which nerve impulse transmitted via neurotransmitters
61
How are nerve impulses transmitted across synapse
* Nerve impulse reaches presynaptic neurone
* Triggers release of neurotransmitters
* Neurotransmitters diffuse across synapse
* Bind to receptors on postsynaptic neurone
* Stimulates impulse in postsynaptic neurone
62
Why do synapses slow down transmission of nerve impulses
Takes time for neurotransmitters to diffuse across synapse and bind to receptors on postsynaptic neurone
63
What is a reflec
* Automatic response to a stimulus by body
* Involuntary - does not involce conscious part of brain
* Protective mechanism e.g. withdrawel reflex is initiated when hot object is touched to prevent burns
64
Describe the reflex arc
Stimulus → Sensory receptor → Sensory neurone → Relay neurone → Motor neurone → Effector → Response
65
Outline structure and function of cornea
* Transparent outer covering of eye
* Refracts light entering eye
66
Outline structure and function of iris
* Pigmented ring of circular muscles and radial muscles
* Controls size of pupil to alter how much light enters eye
67
What is pupil
Hole in iris centre that allows light rays to enter eye
68
Outline structure and function of lens
* Transparent, bi-convex structure
* Suspensory ligaments attach lens to ring of ciliary muscle
* Refracts light, focusing it on retina
69
What is function of ciliary muscles and suspensory ligaments
Change shape of lens (accomodation) to focus light onto retina
70
Outline structure and function of retina
* Light sensitive layer composed of rod and cone cells
* Converts light energy into neural signals which are sent to brain via optic nerve
71
What are rod cells
Cells in retina that are sensitive to low light intensity ( dim light)
72
What are cone cells
Cells found in retina that are sensitive to high light intensity (bright light) and can detect different colours
73
What is function of optic nerve
It transmits nerve impulses to brain from retina
74
Describe how dim light affects size of pupil
* Light receptors detect dim light
* Circular muscles relax
* Radial muscles contract
* Pupil dilates
* More light enters pupil
75
Describe how bright light affects size of pupil
* Light receptors detect bright light
* Circular muscles contract
* Radial muslces relax
* Pupil contracts
* Less light enters pupil
76
Why is iris reflex important
Prevents bright light from damaging retina
77
What is accommodation
| In eyes
* Process by which elastic lens changes shape (with aid of ciliary muscles and suspensory ligaments) to focus on near or distant objects
* Light focused onto retina
78
Describe how eye focuses on near objects
* Ciliary muscles contract
* Suspensory ligaments slacken
* Lens becomes more convex (more rounded)
* Light is refracted more
* Light rays focused onto retina
79
How does eye focus on distant objects
* Ciliary muscles relax
* Suspensory ligaments tighten
* Lens becomes less convex (less rounded)
* Light is refracted less
* Light rays focused onto retina
80
What is long-sightedness
* Can focus on distant objects clearly
* Cannot focus on near objects
81
What are causes of long-sightedness
* Eyeball too short
* Lens is less elastic (usually age related)
* Hence light rays not focussed onto retina, instead converging behind retina
82
How is long-sightedness treated
* Using convex lens (causes light rays to converge) in glasses or contact lenses
* Relacement lenses
* Laser eye surgery
83
What is short-sightedness
* Can focus on near objects clearly
* Cannot focus on distand objects
84
What are causes of short-sightedness
* Eyeball too long
* Lens too thick and too rounded
* Light rays not focused onto retina insrtead converging in front of retina
85
How is short-sightedness treated
* Using concave lens (causes light rays to diverge) in glasses or contact lenses
* Replacement lenses
* Laser eye surgery
86
What are cataracts
* Cloudy patch forms on lens of eye which negatively affects vision
* Vision becomes blurry, difficult to see intensity of colours, problems with glare etc
87
How are cataracts treated
Clouded lens is exchanged for synthetic lens during surgery
88
What is colour-blindness
* Defociency of eye that makes it difficult to distinguish between colours
* e.g. individuals with red-green colour blindess have difficulty differentiating between red and green
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