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Biology > CB2- Cells And Control > Flashcards

CB2- Cells And Control Flashcards

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1
Q

Why is mitosis needed?

A

Mitosis is required for:
- Growth: mitosis produces new cells
- Repair: to replace damaged or dead cells
- Asexual reproduction: mitosis produces offspring that are genetically identical to the parent

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2
Q

What are the products of mitosis?

A
  • two genetically identical, daughter, diploid cells
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3
Q

What is a diploid cell?

A
  • a cell with 23 pairs of chromosomes (46 all together)
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4
Q

What are the three parts of the cell cycle?

A

Interphase
- dna replicates to form two copies of each chromosome
- cell grows and copies it’s internal structures like mitochondria and ribosomes

Mitosis
- when the chromosomes line up along the centre of the cell where spindle fibres oulll them apart

Cytokineses
- occurs right before telophase ends and the cells cytoplasm and cell membrane divide to form two separate daughter cells, each new cell will have a copy of each of the chromosomes

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5
Q

What are the stages of mitosis?

A
  • prophase
  • metaphase
  • anaphase
  • telophase
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6
Q

What happens during prophase?

A
  • the membrane around the nucleus begins to break down so the chromosomes condense and lie free in the cytoplasm, becoming visible
  • spindle fibres also start to appear
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7
Q

What happens during metaphase?

A
  • chromosomes are lined up on the spindle fibres across the middle of the cell (the equator/ metaphase plate)
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8
Q

What happens during anaphase?

A
  • spindle fibres pull the chromosomes apart to opposite ends of the cell
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9
Q

What happens during telophase?

A
  • new membranes form around each set of chromosomes to form nuclei for both the new cells
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10
Q

How do you calculate the number of cells there will be after multiple division?

A

2^n (n is equal to the number of divisions the cell has undergone)

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11
Q

What is asexual reproduction?

A
  • only involved a single parent
  • a process that relies on mitosis
  • produces offspring that are clones because their cells contain the same chromosomes as the parents are are genetically identical
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12
Q

What are some advantages of asexual reproduction?

A
  • fast as it doesn’t require finding a mate
  • allows populations to grow faster as it is fast
  • isolated plants and animals are able to reproduce and grow their populations
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13
Q

What are some disadvantages of asexual reproduction?

A
  • does not provide any genetic variation so if a disease were to be introduced all the individuals in a population would be affected as they have similar genes that would affect how they react to the disease
  • since there is no variation, the majority of traits that a population may have could only be suited for one environment and no adaptations would be able to occur if there was a change in environment
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14
Q

What causes cancer?

A
  • the rate at which cells divide depends on the genes in an organisms DNA
  • if a change or damage occurs to these genes or there are mutations in the DNA, cells may start dividing rapidly, creating a mass amount of abnormal cells that are known as tumours
  • if the tumour invades or destroys the surrounding tissue it is known as cancer
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15
Q

What is growth?

A
  • an increase in size or mass as a result of the increase in number, or size of the cells (increase in number happens due to mitosis)
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16
Q

What two processes allow animals to grow and develop?

A
  • Cell differentiation
  • cell division
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17
Q

What is cell differentiation?

A
  • The process when an unspecialised, undifferentiated cell is able to differentiate in order to become a specialised one that is adapted for a specific function.
  • cell differentiation allows organisms to work more efficiently
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18
Q

How are red blood cells specialised for their function?

A
  • their function is to carry oxygen around the body from the lungs
  • large surface areas to maximise the rate of diffusion
  • biconcave shape which also enhances the large surface area to absorb oxygen
  • no nucleus which maximises volume, allowing for a larger quantity or oxygen to be held
  • thin membrane so gases can easily diffuse through
  • small, narrow and flexible so they can fit through narrow vessels.
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19
Q

How are fat cells adapted to their functions?

A
  • their cytoplasm is filled with large fat droplets that are stored until they need to be used and the body needs energy
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20
Q

How are nerve cells adapted to their functions?

A
  • they have long fibres creating a large surface area that can carry electrical impulses around the body
  • have long axons that carry the electrical impulses from one part of the body to another
  • these axons are covered with mylelin sheath which insulated the axon and speeds up the transmission of nerve impulses
  • the end of these axons also have synapses which allow the impulse to pass from one nerve cell to another
  • cell body of the nerve cell also has dendrites which increase the overall surface area, so that other nerve cells can connect more easily
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21
Q

How are muscle cells adapted to their functions?

A
  • contain special contractile proteins that can shorten the cell
  • long so they can contract
  • contain lots of mitochondria for energy needed for contractions
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22
Q

What are some ways that plants undergo growth and repair?

A
  • cell elongation
  • cell differentiation
  • cell division
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23
Q

What is cell elongation?

A
  • when plant cells are able to physically expand, making the plant bigger
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24
Q

How are root hair cells adapted for their functions?

A
  • they are the cells on the surface of plant roots that grow out into hair like structures into the soil, they absorb water and mineral ions
  • each plant root will have millions of these hairs creating a large surface area maximising the rate of absorption
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25
Q

How are xylem cells adapted for their functions?

A
  • xylem tubes lose their end walls allowing a long hollow tube, it also contains no cytoplasm so the vessel is completely empty allowing water to pass through
  • strengthen with lignin and has thick walls to withstand pressure
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26
Q

When does cell division and differentiation occur in animals?

A
  • all growth in animals happens due to cell division but this mainly happens during youth and then once you become fully grown, cell division usually only occurs for repair and to replace damages cells
  • cell differentiation in animals stops at an early stage
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27
Q

When does cell elongation and growth happen in plants?

A
  • plants will remain growing throughout their entire lives and continue to develop and differentiate into different structures.
  • growth in height will happen due to cell elongation and will occur all throughout the plants life
28
Q

How does cell division occur in plants?

A
  • cell division happens in the roots and shoots in areas called the meristem
  • cells in the meristem will divide rapidly by mitosis. These cells that have been produces will either increase the plants length by elongation or differentiate into specialised cells that have a specific function
29
Q

What are stem cells?

A
  • stem cells are undifferentiated cells that are able to differentiate into specialised ones
  • they are able to divide by mitosis to form more
30
Q

How do stem cells work in plants?

A
  • they are found in the meristem/ roots and shoots (areas that are growing) and are known as meristem cells
  • throughout a plants life, these stem cells will be able to differentiate into any kind of specialised cell like root hair cells and xylem cells
  • however these specialised cells will not fully differentiate and will still stay as stem cells, therefore can still be utilised
  • this allows us to replicate rare species that may be going extinct or grow identical things like crops with desirable characteristics
31
Q

How do stem cells work in animals?

A
  • in animals stem cells are found in early stage embryos and are known are embryonic stem cells that can differentiate into any other style of specialised cell, this is why stem cells are very important for growth and development
  • however once the animal is fully developed stem cells can only be found in specific places like bone marrow and can no longer produce any type of cell, just blood cells (blood platelets, white blood cells and red blood cells)
32
Q

How do scientists use stem cells?

A
  • embryonic stem cells will be extracted from an early human embryo and then grown in a lab
  • it will then be stimulated into differentiating into specific kinds of unspecialised cells
33
Q

Pros and cons of using adult stem cells.

A
  • since adult stem cells can only differentiate into blood cells they can cure diseases of the blood, however they would not be able to cure something like diabetes or paralysis
  • do not have as many ethical issues since the stem cells are not being acquired by an embryo
  • adult stem cells may be painful to extract
  • since they usually come from the recipient they will contain the same DNA therefore decreasing the risk of rejection.
34
Q

Drawbacks from using embryonic stem cells.

A
  • rejection- if transplanted cells are not grown using the patients own stem cells, the patients body may recognise it as foreign and trigger an immune response to try and get rid of them
  • tumour development- stem cells divide very quickly and if scientists are unable to control this rapid division, tumours could form
  • disease transmission- if donor cells are infected with a virus, the virus could be passed onto the recipient
  • the core use of embryonic stem cells- limited supply and many ethical issues, some people argue there is a potential for human life but others argue existing life is more important.
35
Q

How could you stop an immune response from using external embryonic stem cells?

A
  • take drugs to prevent this response, however it does not always work.
  • or you could do therapeutic cloning- this is when you make an embryo with the same genetic material as the patient to stop rejection
36
Q

What are some issues with therapeutic cloning?

A
  • embryonic stem cells could catch a disease in the lab and then be put into the patients body
  • LOTS! Of ethical issues. Eg. Embryo could have a potential life
37
Q

What is the CNS?

A
  • the CNS is the central nervous system
  • the CNS is made up of the brain and spinal chord, the rest of the nervous system is made up of neurones (nerve cells)
38
Q

What are the stages of a response being co ordinated?

A
  • the body has many sensory receptors that can detect stimuli and convert this information to a nervous electrical impulse and sent along sensory neurones to the CNS
  • the CNS then co ordinates a response to the stimuli and sends the impulse through the CNS along relay neurones
  • going along this relay neurone, information from the CNS will transfer to the motor neurone
  • the information will travel along the motor neurone to the effector
  • the effector will then respond accordingly
39
Q

What are sensory receptors?

A
  • groups of cells that can detect a change in environment
40
Q

What is a stimulus?

A
  • a change in environment that is detected by sensory receptors
41
Q

What is an effector?

A

An effector is a muscle or gland that responds to stimuli by either contracting or secreting a hormone

42
Q

What are dendrites and dendrons?

A
  • dendrites are branched nerve fibres which receive nerve impulses and pass them towards cell bodies
  • dendrons are long nerve fibre extension leading to the cell body
  • dendrites extend out of the cell body of the neurone and at the far end of the axon in order to connect to many other neurones and receive impulses from them, creating an efficient network
43
Q

What processes do plants and animals grow via?

A

Animals and plants:
- Cell division - mitosis
- Cell differentiation - development of specialised features creating specialised cells
Just plants:
- plants also go through cell elongation where cells grow physically longer

44
Q

What is a benign tumour?

A
  • Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane
  • since they do not invade other parts of the body they are not considered cancerous
45
Q

What is a malignant tumour?

A
  • cancerous tumours that invade neighbouring tissues and spread to other parts of the body via the blood and the lymphatic system where secondary tumours can be formed
  • they invade healthy tissue so they can distrust how the organ functions which is extremely dangerous and can cause death
46
Q

What is a totipotent cell?

A
  • a cell that can differentiate into any kind of cell
  • for example embryonic stem cells that help form all of the different tissues and organs needed during development to make up the animal
47
Q

How could stem cells treat paralysis?

A
  • paralysis is caused by damage to the nerve cells in the brain or spinal chord and it prevents signals from the brain reaching muscles in other parts of the body causing a loss of movement
  • stem cells could be differentiated into nerve cells (neurones) which are transplanted into the damaged region of the nervous system
  • these stem cells would come from donors or therapeutic cloning
48
Q

How could stem cells treat type 2 diabetes?

A
  • type 2 diabetes are caused by the inability of the pancreas to produce insulin to control blood sugar levels.
  • stem cells could be differentiated into insulin- producing pancreatic cells which are transplanted into the patients body
  • the stem cells would come from donors or therapeutic cloning
49
Q

What are the benefits of using stem cells?

A
  • can treat a wide range of diseases like diabetes and paralysis
  • embryonic stem cells have the ability to change into many different cell types so they can cure many diseases
  • when the patients uses their own stem cells they reduce the risk of rejection and the long wait for an organ donation
  • adult stem cells have already proven to be very successful in a variety of treatments.
50
Q

What are the risks of using stem cells?

A
  • Stem cells cultured in the lab could become infected with a virus which could be transmitted to the patient
  • There is a risk of cultured stem cells accumulating mutations that can lead to them developing into cancer cells by dividing uncontrollably
  • Low numbers of stem cell donors
51
Q

What are the ethical issues of using stem cells?

A
  • embryonic stem cells can be sourced from unused embryos produced in IVF treatments that were initially going to be disposed of, but some still believe this is unethical as there is a possibility for human life
  • creating embryos specifically for the intention of therapeutic cloning can be argued as immoral
  • some people believe embryos should be treated with human rights
52
Q

What is the peripheral nervous system?

A
  • the PNS is all the nerves in the body
53
Q

How is information sent through the nervous system?

A
  • information is sent in the form of electrical impulses, these are electrical signals that pass along neurones/ nerve cells
54
Q

What are the adaptations of neurones?

A
  • neurones have cell bodies with a nucleus+ other sub cellular structures
  • they also have cytoplasmic extensions from the cell body calls dendrites, dendrons and axons
  • axons are insulated by a fatty myelin sheaths that acts as electrical insulators, speeding up the electrical impulse, they also have gaps in between these which are uninsulated sections known as nodes which causes the impulse to jump along the cell speeding up
  • dendrites extend out of the cell body of the neurone and at the far end of the axon in order to connect to many other neurones and receive impulses from them, creating an efficient network
55
Q

Why are neurones long?

A
  • neurones are long because having a single passage speeds up the rate the electrical impulse passes through it
  • connecting lots of short neurones would take a long time as the impulse would have to keep diffusing through synapses
56
Q

What are axons?

A
  • a single nerve fibre that carries nerve impulses away from a cell body which is insulated by a fatty myelin sheath that acts as an electrical insulator, speeding up the electrical impulse
  • they also have gaps in between these which are uninsulated sections known as nodes which causes the impulse to jump along the cell speeding up
57
Q

What do sensory neurones do?

A
  • Sensory neurones carry impulses from receptor cells to the CNS (brain or spinal cord)
58
Q

What do motor neurones do?

A
  • Motor neurones carry impulses away from the CNS to effectors (muscles or glands)
59
Q

What do relay neurones do?

A
  • Relay neurones are short and found inside the CNS and connect sensory and motor neurones
60
Q

Describe sensory neurones.

A
  • sensory neurones are long and have a cell body branching off the middle of the axon
  • starting from the left there are dendrites that receive the impulses from receptor cells and then passes through the dendron and axon which contains a cell body in between
  • the axon is connected to axon terminals which branch off and pass impulses to other neurones.
  • the dendron and axon are surrounded with myelin sheath to act as an electrical insulator and there are also gaps between the myelin causing the impulse to jump along the cell, therefore speeding up neurotransmission.
61
Q

Describe motor neurones.

A
  • Motor neurones are long and have a large cell body at one end with short dendrites branching off it
  • lots of dendrites branch off the cell body carrying nerve impulses from the CNS to the cell body
  • one very long axon will transfer this impulse from the cell body to the axon terminals which then pass them onto the effector cells eg. Muscle cells that will contract as a result of the nerve impulses
  • the super long axon can also have myelin sheath acting as an electrical insulator but also can be without it (same with sensory and relay neurones)
62
Q

Describe relay neurones.

A
  • Relay neurones are short and have a small cell body at one end with many dendrites branching off it
  • the cell body has many short dendrites branching off it that carry nerve impulses from the CNS to the cell body
  • attached to this, there is a long axon with carries the impulse from the cell body to motor neurones
  • attached to this, there are many axon terminals
63
Q

What is a synapse and how does an electrical impulse pass through it?

A
  • Where the dendrites of two neurones meet (to make a connection between the neurones) a junction/tiny gap known as a synapse is formed
  • Electrical impulses cannot travel directly from one neurone to the next due to the synaptic gap (electricity cannot ‘jump’ the gap)
  • when an impulse reaches an axon terminal the electrical signal is briefly converted to a chemical signal that can cross the synaptic gap
  • The chemical signalling molecules used to transfer the signal between neurones at a synapse are known as neurotransmitters
  • Once these neurotransmitters cross the synaptic gap and meet the neurone on the opposite side, the signal is converted back into a new electrical impulse, which can then pass along the neurone
  • the transmission of a nervous impulse is very fast but slowed down slightly at the synapse because the diffusion of neurotransmitters across the gap takes time
64
Q

How do neurotransmitters move across synapses?

A

Neurotransmitters move by diffusion- this requires a concentration gradient and is a passive process

65
Q

What is a reflex?

A
  • automatic, rapid responses to stimuli that reduce the chances of injury
66
Q

Describe the reflex arc.

A
  • the neurones in reflex arcs go through either the spinal chord or unconscious parts of the brain
    1. A stimulus will be detected by cell receptors and impulses will be sent along a sensory neurone to a relay neurone in the CNS.
    2. The impulse will reach a synapse between the sensory neurone and relay neurone so neurotransmitters will be triggered to be released and the impulse will be able to be transferred to the relay neurone
    3. Then, the impulse will reach a synapse between the relay neurone and motor neurone, neurotransmitters will be triggered to be released and cause impulses to travel across to the motor neurone
    4. The impulses will travel through the motor neurone, then to the effector (muscle cells or glands) causing them to quickly contract or release a hormone.
67
Q

How do reflexes protect the eye?

A
  • bright lights can damage the eye so there are reflexes to protect it
  • light receptors on the eye will detect very bright lights and can send a message along a sensory neurone to the brain
  • this message then travels along a relay neurone to the motor neurone which tells circular muscles in the iris to contract, making the pupil smaller.

Biology (9 decks)

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