Topic 2 - Cells And Control Flashcards
What benefits are there of use of stem cells in medicine? (2)
- Possible to use stem cells to create specialised cells to replace those which have been damaged by disease and injury.
- Possible to find new cures for diseases
Describe growth in plants. (8)
Plants produced by sexual reproduction begin life as a a single cell, a fertilised egg or zygotes. These cells must divide by mitosis to produce a multicellular organism. Mitosis only happens in specific regions of plants. These are called meristems and are found in the tips of roots and shoots. Here new cells are formed. Plant cells are also able to become longer as they grow. This is called cell elongation and occurs throughout the plant. The cells of multicellular plants must also differentiate, so that its cells develop features that enable them to fulfil specific roles. Cells that have differentiated have specialised. Without this specialisation, complex multicellular plantsq wouldn’t exist.
What does the relay neurone do?
Relay neurones carry messages from one part of the CNS (brain and spinal cord) to another.
Describe the medulla oblongata.
Controls unconscious activities such as heart rate and breathing rate.
Describe the importance of mitosis in: Repair
Organisms can repair some of their tissues, using mitosis to regenerate new cells.
What do rod cells do?
They work well in dim light.
Describe the Cerebellum.
This part of the brain is responsible for muscle coordination and balance.
How can cataracts be treated?
Cataracts can be treated by removing the lens and replacing with a plastic lens.
What does the cornea do?
Refracts light - bends it as it enters the eye
Risks of brain surgery (7)
- allergic reaction to anesthesia
- bleeding in the brain
- a blood clot
- brain swelling
- coma
- impaired speech, vision, coordination, or balance
- infection in the brain or at the wound site
Describe the stage of mitosis: Telophase
A new cell membrane forms around the two sets of DNA so the cell has two nuclei in it. A cleavage furrow forms.
Describe the function of embryonic stem cells.
These embryonic stem cells have the potential to divide and produce any kind of cell at all. This makes sense all the different types of cell found in a human have to come from those few cells in the early embryo. This means stem cells are really important for the growth and development of organisms.
Describe the importance of mitosis in: Growth
When a multi cellular organism grows, it makes more cells through mitosis which allows the organism to grow and successfully live.
What does the iris do?
Controls how much light enters the pupil
What does the synapses do?
Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals released by a neurone. The chemical diffuses across the gap makes the next neurone transmit an electrical signal.
Describe the cerebral hemispheres. (4)
The cerebrum’s outer layer, it is split into two hemispheres and is highly folded. These two hemispheres make up the cerebral cortex. This controls most of our senses, intelligence, personality, conscious thought and high-level functions, such as language and verbal memory.
What are receptors?
Receptors are groups of specialised cells. They detect a change in the environment and stimulate electrical impulses in response. Sense organs contain groups of receptors that respond to specific stimuli.
What does uncontrolled cell division lead to?
Sometimes the cells in part of a multicellular organism divide uncontrollably. The result is a large mass of cells called a tumour. If tumour cells successfully invade other tissues in the body the result is cancer
What is mitosis?
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth
Describe the stage of mitosis: Metaphase
Chromosomes line up at the cell’s equator (across the middle), there is double amount of DNA in the cell. Fibres start to form.
What are cataracts?
A cataract is a cloudiness in the lens, caused by a build up of protein inside the lens.
How can long-sightedness be corrected?
It can be corrected by using glasses that have convex lenses.
Describe the stage of mitosis: Cytokinesis
The cell spilts into two genetically identical cells.
Describe the function of stem cells in animals.
In animals, adult stem cells are used to replacing damaged cells. E.g. to make new skin or blood cells.
What is a neurone?
Nerve cells are called neurones. They are adapted to carry electrical impulses from one place to another. A bundle of neurones is called a nerve.
Describe the function of meristems in plants.
Meristems produce unspecialised cells that are able to divide and form an cell type in the plant they act like embryonic stem cells. But unlike human stem cells, these cells can divide and differentiate to generate any type of cell for as long as the plant lives. The unspecialised cells go on to form specialised tissues like xylem and phloem
What do the three main types of neurones have in common? (3)
- A long fibre (axon) which is insulated by a fatty (myelin) sheath. - - They are long so they can carry messages up and down the body.
- Tiny branches (dendrons) which branch further as dendrites at each end. These receive incoming impulses from other neurones.
Describe the stage of mitosis: Interphase
This is when the cell does what it is doing what it usually does. It is not a part of mitosis. But by the end of this phase the cell’s DNA will have replicated.
Describe the importance of mitosis in: Asexual reproduction
Mitosis is important in asexual reproduction as there is only one parent and mitosis divide the one cell into two. The offspring is identical to the parent.
What risks are there of use of stem cells in medicine? (3)
- Tumour development - stem cells divide very quickly. If scientists are unable to control the rate at which the transplanted cells divide inside a patient, a tumour may develop.
- Disease transmission viruses live inside cells. If donor stem cells are infected with a virus and this isn’t picked up, the virus could be passed on to the recipient and so make them sicker.
- Rejection if the transplanted cells aren’t grown using the patient’s own stem cells, the patient’s body may recognise the cells as foreign and trigger an immune response to try to get rid of them The patient can take drugs to suppress this response, but this makes them susceptible to diseases.
What is long-sightedness? (3)
Someone who is long-sighted can see distant objects clearly, but they cannot focus properly on near objects.
Long-sightedness is caused by one of the following:
- the eyeball being too short - so the distance between the lens and retina is too small.
- a loss of elasticity in the lens - meaning it cannot become thick enough to focus (which is often age-related).
Describe the stage of mitosis: Prophase
The DNA has condensed into chromosomes. Nucleus has disappeared so the DNA is free to move in the cytoplasm.
What does the motor neurone do?
Motor neurones carry signals from the CNS to effectors (e.g. muscles, glands) .
Why is CT scanning and PET scanning useful for accessing brain tissue?
We can’t always look inside the brain without performing some form of surgery so we can use CT and PET scans to look at the brain. This is much less invasive for the patient. Also, these scans are much useful for looking for soft tissue than x-rays.
What does the sensory neurone do?
Sensory neurones carry signals from receptors to the CNS (spinal cord and brain).
What are the three main types of neurone?
- Sensory
- Motor
- Relay
What does the lens do?
Further refracts light to focus it onto the retina
Describe growth in animals. (7)
Animals produced by sexual reproduction begin life as a a single cell, a fertilised egg or zygotes. These cells must divide by mitosis to produce a multicellular organism. Mitosis happens throughout the bodies of animals. Cell elongation doesn’t happen in animals. The cells of multicellular animals must also differentiate, so that its cells develop features that enable them to fulfil specific roles. Cells that have differentiated have specialised. Without this specialisation, complex multicellular animals wouldn’t exist.
How can shortsightedness be corrected?
It can be corrected by using glasses that have concave lenses.
What is shortsightedness? (3)
Someone who is short-sighted can see near objects clearly, but cannot focus properly on distant objects.
Short sight is caused by one of the following:
- the eyeball being elongated - so that the distance between the lens and the retina is too great.
- the lens being too thick and curved - so that light is focused in front of the retina.
Describe the stage of mitosis: Anaphase
Spindle fibres pull the chromosomes apart so half the DNA is at one of the cell and the other half is at the other.
What is the myelin sheath?
The axon is surrounded by a fatty layer known as the myelin sheath. This helps to protect the neurone and allow impulses to travel faster.
What do cone cells do?
They are responsible for colour vision and work well in bright light.
