SB2 - Cells & control Flashcards
1
Q
What are organisms made up of many cells called?
A
Multicellular organisms
2
Q
What do multicellular organisms need in order to grow?
A
New cells
3
Q
When do cells divide?
A
- When an organism grows
- When an organism becomes damaged & needs new cells for repair
- When organisms reproduce asexually
4
Q
What is the cell cycle?
A
The events that lead to cell division & DNA replication
5
Q
What is Mitosis?
A
A type of cell division which produces daughter cells identical to the parent
6
Q
What are the phases of the cell cycle?
A
- Interphase
- Mitosis
- Cytokinesis
7
Q
What is interphase
A
- The cell grows, organelles (such as ribosome and
mitochondria) grow and increase in number - The synthesis of proteins occurs
- DNA is replicated (forming the characteristic ‘X’ shape) and energy stores are increased
8
Q
What are the substages of mitosis?
A
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
9
Q
What is Prophase?
A
The nucleus starts to break down and spindle fibres appear
10
Q
What is Metaphase?
A
The chromosomes are lined up in the spindle fibres across the middle of the cell
11
Q
What is Anaphase?
A
The chromosome copies are separated and moved to either end of the cell on the spindle fibres
12
Q
What is Telophase?
A
A membrane forms around each set of chromosomes to form nuclei
13
Q
What is Cytokinesis?
A
Two identical daughter cells form when the cytoplasm and cell membranes divide
14
Q
How many daughter cells does mitosis produce?
A
2 genetically identical diploid cells
15
Q
Where is a diploid number of chromosomes found in the body?
A
Body cells (46)
16
Q
Where is a haploid number of chromosomes found in the body?
A
Gametes (23)
17
Q
What is a gene?
A
A short section of DNA that codes for a protein and as a result controls a characteristic- therefore each chromosome carries many genes
18
Q
How does cancer occur?
A
As a result of small changes in cells, that lead to uncontrolled cell division
19
Q
What is a tumour?
A
The group of cells that results from this uncontrolled division
20
Q
How does growth occur in animals?
A
Via cell division and differentiation
21
Q
What is differentiation?
A
The process by which a less specialised cell becomes more specialised for a particular function
22
Q
How does growth occur in plants?
A
Via cell division, differentiation and elongation
23
Q
How can plant cells grow in a specific direction?
A
By absorbing water into their vacuoles
—> Controlled by auxins
24
Q
At what time can plants differentiate?
A
Many types of cells retain the ability to differentiate throughout life
25
What are the *types* of **stem cells**?
* Embryonic
* Adult
* Meristem
26
What can **embryonic stem cells** differentiate into?
Any type of body cell
27
When do **embryonic stem cells** form?
When an egg and sperm cell fuse to form a zygote
28
How can scientists **clone embryonic stem cells**?
By culturing them
29
What can **Adult stem cells** differentiate into?
Many types of cells (including blood cells)
30
What can **meristem cells** differentiate into?
Any type of plant, and have this ability throughout the life of the plant
31
Where are **meristem cells** found?
Root shoot and tips
32
What is **therapeutic cloning**?
Involves an embryo being produced with the same genes as the patient.
33
Describe how **therapeutic cloning** works
The embryo produced could then be harvested to obtain the embryonic stem cells
---> Could be grown into any cells the patient needed
34
What is an *advantage* of **therapeutic cloning**?
They would not be rejected as they would have the exact same genetic make-up as the individual
35
What are the **benefits** with the **use of stem cells** in medicine?
* Can be used to replace damaged or diseased body parts
* Research into the process of differentiation
* Unwanted embryos from fertility clinics
could be used
36
What are the **problems** with the **use of stem cells** in medicine?
* People may have religious or ethical objections
* If growing cells are contaminated w/ virus - can pass onto individual
* Don't completely understand the process of differentiation
* People may have religious or ethical objections
* Removal of stem cells = destruction of the embryo
37
Why may people have **religious or ethical objections** when using **embryonic stem cells**?
As it is seen as interference with
the natural process of reproduction
38
Why might **not understanding the process of differentiation** be a problem when using **embryonic stem cells**?
It is hard to control stem cells to form the cells we desire
39
What makes up our **CNS**?
* The brain
* Spinal cord
40
What is the **CNS** responsible for?
Controlling consciousness, movements thoughts and emotions, among other things
41
Where is the **cerebral hemispheres** located?
On the left & right hand sides
42
What are the *functions* of the **cerebral hemispheres**?
* Consciousness
* Memory
* Intelligence
* Visual & sensory processing
43
Where is the **cerebellum** located?
Bottom of the brain, on the rear side
44
What are the *functions* of the **cerebellum**?
Fine movements of muscles
---> Ensuring movements are smooth
45
Where is the **medulla oblongata** located?
In the brainstem, at the base of the brain
46
What are the *functions* of the **medulla oblongata**?
* Breathing
* Digestion
* Swallowing
* Sneezing
47
What *scans* can we use to **look inside the brain**?
* PET
* CT
48
What are **CT** scans?
Fire X-Ray radiation at the brain from several different angles to generate a 3D image of the brain
49
What are **CT scans** useful for?
* Examining bleeding
* Damage to brain structures
50
Why are **CT scans** not recommended for **pregnant women and children**?
As it exposes the patient to higher doses of radiation than a normal X-ray
51
How do **PET** scans work?
A radioactive ‘tracer’ is injected into the blood before the scan.
---> Scan itself is sensitive to the tracer - areas where the tracer builds up will be highlighted more brightly on the resulting scan.
52
Why will the **tracer** in a **PET scan** build up in *certain areas*?
As they will also be areas with greater blood flow
53
What are **PET scans** useful for?
Identifying cancerous tumours
54
Why is *Investigating brain function and treating brain damage* **difficult**?
* It is complex and delicate
* It is easily damaged
* Drugs given to treat diseases cannot always reach the brain
* It is not fully understood which part of the brain does what.
55
Why can't **certain drugs reach the brain** when treating diseases?
Because of the membranes that surround it
56
Why might **brain tumours** be **difficult to remove**?
* Can push against other structures and blood vessels in the brain
* Can be buried deep in the brain or spinal cord - difficult to remove
57
What is **the eye**?
A sense organ containing receptors sensitive to light intensity and colour
58
Name some *structures* in the **eye**
* Retina
* Cornea
* Iris
* Ciliary muscles
* Lens
* Suspensory ligaments
59
What is the **Retina**?
Layer of light sensitive cells found at the back of the eye
60
What does the **Retina** contain?
* Rod cells
* Cone cells
61
What are **cone cells** sensitive to?
Colour
62
What are **rod cells** sensitive to?
Light
63
What is the **Cornea**?
The see-through layer at the front of the eye
64
What is the *purpose* of the **cornea**?
*Allows light through* Curved surface bends and focuses light onto the retina
65
What is the **Iris**?
Muscles that surrounds the pupil.
66
What is the *purpose* of the **iris**?
Contracts or relaxes to alter the size of the pupil
67
How does the **Iris** react to **bright light**?
The circular muscles contract and radial muscles relax
---> To make the pupil smaller- avoiding damage to the retina
68
How does the **Iris** react to **dim light**?
The circular muscles relax and the radial muscles contract
---> To make the pupil larger- so more light can enter to create a better image
69
What is the **ciliary muscle** and the **suspensory ligaments**?
Hold the lens in place
70
What is the **ROLE** of the **ciliary muscle** and the **suspensory ligaments**?
They control its shape and allow us to focus on objects nearer or further away
71
What is the **Lens**?
Transparent, curved surface on the front of the eye
72
What is the **purpose** of the **Lens**?
Reflects light onto the retina
73
What is **accommodation**?
The process of changing the shape of the lens to focus on near or distant objects
74
Describe how **eyes** focus on a **near object**?
● The ciliary muscles contract
● The suspensory ligaments loosen
● The lens is then thicker and more curved- this refracts the light more
75
Describe how **eyes** focus on a **distant object**?
● The ciliary muscles relax
● The suspensory ligaments tighten
● The lens then becomes thinner - light is refracted less
76
Name some *eye defects*
* Myopia
* Hyperopia
* Cataracts
* Colour blindness
77
What is **Myopia**?
| And why might people have this?
Short-sightedness
---> lens is too curved, so distant objects appear blurry
78
What is **Hyperopia**?
| And why might people have this?
Long sightedness
---> Lens is too flat, so it cannot refract light enough
79
How can **myopia** and **hyperopia** be *treated*?
* Spectacle lenses
* Contact lenses
* Laser eye surgery
* Replacement lens
80
How can **spectacle lenses** be used to treat **myopia**?
Concave lenses = spreads out the light to treat myopia
81
How can **spectacle lenses** be used to treat **hyperopia**?
Convex lenses = brings the rays together to treat hyperopia
82
How can **laser eye surgery** be used to treat **myopia or hyperopia**?
Lasers can be used to either reduce the thickness of the cornea or change its curvature
83
How can a **replacement lens** be used to treat **hyperopia**?
Either by:
* Replacing the lens with an artificial one made of clear plastic
* Adding the plastic on top of the natural lens
84
What are the **risks** of **replacement lens**?
* Damage to retina
* Cataracts developing
85
What are **cataracts**?
Clouding of the lens of the eye
86
How are **cataracts** fixed?
By replacing the lens of the eye in surgery w/ a plastic one
87
What is **colour blindness**?
The inability to see certain colours
88
Why does **colour blindness** occur?
As people with the condition do not have enough cone cells in their retina
---> Usually genetic
89
Can **colour blindness** be corrected?
No
90
What is are **reflexes**?
Automatic responses which take place before you have time to think
91
Why are **reflexes** important?
They prevent the individual from getting hurt
92
What are **synapses**?
Gaps between two neurons
93
What are **motor neurones**?
A type of neuron that carries impulses to effectors
94
What are **relay neurones**?
A short type of neurone found in the spinal chord and brain
---> Relay neurones link sensory, motor & other relay neurones together
95
What are **sensory neurones**?
A neurone that carries impulses from receptor cells towards the CNS
96
What is a **reflex arc**?
A neurone pathway consisting of a sensory neurone passing impulses to a motor neurone which allows reflexes to occur
97
Describe the **reflex arc**?
1. A stimulus is detected by receptors
2. Impulses are sent along a sensory neuron
3. In the CNS the impulse passes to a relay neuron
4. Impulses are sent along a motor neuron
5. The impulse reaches an effector resulting in the appropriate response
98
What happens when an **impulse reaches the end of the 1st neuron**?
A neurotransmitter is released into the synapse
99
Describe how **impulses** are **transmitted between synapses**
● When the impulse reaches the end of the first neuron -
neurotransmitter is released into the synapse
● This neurotransmitter diffuses across the synapse
● When the neurotransmitter reaches the second neuron, it triggers the impulse to begin again in the next neuron
100
Why are there **different speeds & frequencies** of impulses?
Different neurotransmitters have different effects on the frequency and speed of the impulse in the second neuron
101
Why are **synapses** useful?
* As neurotransmitters are released from axon terminals so impulses only flow in one direction
* Allow fresh impulses to be generated - original impulse will not lose 'strength'
102
What is **myelin sheath**?
A fatty substance which surrounds and insulates neuron axons
103
What is a **benefit** of **myelin sheath**?
Nerve transmission will travel faster
104
What is **Myelin sheath** produced by?
Schwann cells
105
How does the **nervous system** coordinate actions **in response to stimuli**?
1. Receptor cells convert a stimulus into an electrical impulse
2. This electrical impulse travels along sensory neurons to the CNS
3. The information is processed & the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors
4. The effectors carry out the response
