Cells And Control Flashcards
What does mitosis produce
2identical daughter cells
What are the 4 stages of mitosis
Interphase, prophase, metaphase, anaphase, telophase, cytokinesis
What happens at interphase
Before the cell divides it has to grow to increase the number of mitochondria & ribosomes. Then in duplicates it dna - copied dna forms x-shaped chromosomes
What happens at each stage of mitosis
1-prophase) The chromosomes get condense (shorter&fatter). The membrane around the nucleus breaks down and the chromosomes lie free in cytoplasm
2-metaphase) The chromosomes line up at the centre of the cell
3-anaphase) Spindle fibres pull the chromosomes apart. Then the chromatids are pulled to opposite ends of the cell
4-telophase) Membranes form around each of the sets of chromosomes, these become the nuclei of the 2 new cells - nucleus has divided
What happens before telophase ends
Cytokinesis
What is cytokinesis
When cytoplasm and cell membrane divide to form 2 separate cells
How to calculate the number of cells they’ll be after after divisions
2(n) (n=number of divisions by mitosis)
What happens at mitosis and cytokinesis
Once the dna has been copied, it’s ready for mitosis
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.
How is cancer caused
Uncontrolled cell divisor - if there is a change in the gene that controls mitosis the cell could start to divide uncontrollably, which can result in a mass of abnormal cells = tumor, if the tumor invades and destroys surrounding tissues =cancer
What is a diploid cell
A cell with 2 copies of each chromosome
What do organisms use mitosis for
To asexually reproduce
What’s cell differentiation
The process by which a cell changes to become specialised for its job
What is cell elongation
Where a plant cell expands, making the cell bigger -plant grow
What is most cell division used for in adults
Repair - cells divide to replace old or damaged cells
Where does cell division happen in a plant?
I’m the tips of the roots and shoots and meristems
What are stem cells
Undifferentiated cells
How do cells become specialised
They differentiate
Where are stem cells found
Early human embryos
What can embryonic stem cells do
Divide and produce any kind of cells
What are stem cells really important for
Growth and development of organisms
Where are stem cells found in adults
Bone marroe
What are adult stem cells used to do in animals
Replace damaged cells e.g to make new skin or blood cells
In plants, where are the only cells that divide by mitosis found
In plant tissues called meristems
Where are meristem tissues found
In areas of a plant that are growing e.g. tips, roots, shoots
What do meristems produce
Unspecialised cells that act like embryonic stem cells
What do the unspecialised cells in plants go on to form
Xylem, phloem
How is sickle cell anemia cured
With a bone marrow transplant
What are the 3 potential risks about using adult stem cells to cure some diseases
Tumour development, disease transmission, rejection
What is tumour development
When stem cells divide very quickly, if scientists are unable to control the rate at which the transplanted stem cells divide, a tumour may develop inside the patient
What is disease transmission
Viruses live inside cells, if donor cells are infected with a virus and are undetected the virus could be passed on to the patient and make them sicker
What is rejection
If the transplanted cells aren’t grown using the patients own stem cells, the patients body may recognise them as foreign and trigger an immune response to try get rid of them. The patient can take drugs to suppress this, but that can make them susceptible to diseases
What is the ethical issue raised about using embryonic stem cells
Some people argue that using embryonic stem cells shouldn’t be used for experiments because each one is a potential life
What can you use stem cells for
To create specialised cells to replace those which have been damaged by disease or injury
What is the nervous system made up of
Neurones(nerve cells)
What are sensory receptors
Groups of cells that can detect a change in your environment (a stimulus)
What happens when a stimulus is detected by receptors
The info is converted to a nervous(electrical) impulse and sent alone sensory neurones to the CNS (brain and spinal chord)
What does the CNS do
Coordinates the response
How do impulses travel
Through the CNS along relay neurones
What does the cns do
Sends info to an effector (muscle/gland) along a motor neurone
What is reaction time
The time it takes you to respond to a stimulus
What do all neurones have
A cell body with a nucleus
What does the cell body have
Extensions that connect to other neurones
What do dendrites and dendrons do
Carry nerve impulses towards the cell body
What do axons do
Carry nerve impulses away from the cell body
What are some axons surrounded by
Myelin sheath
What does myelin sheath do
Acts as an electrical insulator speeding up the electrical impulse
What is the structure of a sensory neurone
One long dendron, one short axon
What does a sensory neurone (dendron) do
Carried nerve impulses from receptor cells to cell body which is located in the middle of the neurone
What does a sensory neurone (axon) do
Carries nerve impulses from cell body to CNS
What is the structure of a motor neurone
Many short dendrites, one long axon
What is the function of the motor neurone (short dendrites)
Carry nerve impulses from cns to cell body
What is the function of motor neurone (long axon)
Carries nerve impulses from cell body to effector cells
Structure of relay neurone
Short dendrites, axon
Function of relay neurone
Relay neurons are found in the brain and spinal cord and allow sensory and motor neurons to communicate.
What is a synapse
The connection between 2 neurones
What are nerve signals transferred by
Chemical called neurotransmitters which diffuse across the gap
What are reflexes
Automatic responses to stimuli
