cells and control Flashcards
Describe mitosis as part of the cell cycle, including the stages
interphase, prophase, metaphase, anaphase and telophase and
cytokinesis
interphase - before cell divides its DNA is spread into long stings, before dividing the cell has to grow and increase amount of subcellular structures. duplicates its DNA copied into Xshaped chromosomes which are duplicates of each other
prophase - chromosomes condense, membrane around nucleus breaks down and chromosomes lie free in cytoplasm
metaphase - chromosomes line up at centre of cell
anaphase - spindle fibres pull chromosomes apart then to opposite end of cell
telophase - membranes form around each sets of chromosomes which become the nuclei of the 2 new cells, the nucleus has divided
cytokinesis - before telophase ends, cytoplasm and cell membrane divide to from 2 separate cells
Describe the importance of mitosis in growth, repair and
asexual reproduction
mitosis is used to grow or replace cells that have been damaged
some organisms use mitosis to reproduce in asexual reproduction
what does the division of a cell by mitosis produce
- produces two identical daughter cells
- these have identical sets of chromosomes in the nucleus to the parent cell
- results in formation of two genetically identical diploid body cells
- these have identical sets of chromosomes in the nucleus to the parent cell
Describe cancer as the result of changes in cells that lead to
uncontrolled cell division
cancer can occur when cells divide uncontrollably,
which could happen if one of the genes that control cell division
when cells divide uncontrollably this can result in a mass of abnormal cells called a tumour,
if the tumour invades and destroys tissue this is called cancer
what is cell differentiation
cell differentiation = the process by which a cell changes to become specialised for its job. so its multicellular organism can work more efficiently
describe growth in animals
happens by cell division.
when animals are young their growing so their cells divide at a fast rate, but mostly when your older cell division is for repair to replace damaged or old cells.
so in most animals cell differentiation is lost at an early stage
describe growth in plants
cell division, elongation and differentiation
growth in height is mainly elongation,
cell division happens in tips of roots (meristems)
plants often grow continuously so they differentiate to develop new parts
what is cell elongation
when plant cells expand making the cell bigger and so making the plant grow
Explain the importance of cell differentiation in the development
of specialised cells
cell differentiation produces specialised cells so the specialised cells can allow multicellular organisms to work more effectively
stem cells can differentiate into specialised cells as stem cells divide by mitosis to become new cells which then differentiate
how do percentile charts monitor growth
- growth charts are used to assess a child’s growth over time so that an overall pattern in development can be seen as well as any problems highlighted
- the chart shows a number of percentiles, ex 50th percentile shows mass that 50 babies will have reached
ex if a babies head is above the top percentile line or below the bottom percentile line or if there is an inconsistent pattern then doctors might investigate
Describe the function of embryonic stem cells, stem cells in
animals and meristems in plants
embryonic - human embryonic stem cells are the most versatile because they can develop into any cells.
stem cells in animals - adults can also have stem cells, ex finding them in bone marrow, these aren’t as versatile as embryonic stem cells . adult stem cells can be used to replace damaged tissue
stem cells in meristems in plants - the only cell in plants that can divide by mitosis are found in the meristem, meristem is found is parts of plant that are growing ex roots and shoots
meristems produce unspecialised cells that are able to form can cell type for as long as the plant lives
Discuss the potential benefits and risks associated with the use
of stem cells in medicine
benefits
- stem cells can create specialised cells to replace cells that have neem damaged by a disease or injury
- stem cells have the potential for new cures as stem cells have already been used to cure some diseases
risks - tumour development - stem cells divide quickly, if at uncontrollable rate this can develop a tumour
- disease transmission - viruses live inside cells, if donor stem cells are infected then the virus could be passed on
- rejection - patients body may recognise these new cells as being foreign and so may trigger an autoimmune response to get rid of them. (the patient can take drugs to supress this which could lead to them being more susceptible to diseases)
- ethical issues - early human embryos used shouldn’t be used for experiments when each one has a potential for a human life
explain the structure and the function of sensory neurones
sensory neurones
- one long dendron that carries nerve impulses from receptor cells to cell body located in middle of neurone
- one short axon that caries nerve impulses from cell body to CNS
explain the structure and the function of motor neurones
motor neurones
- many short dendrites carry nerve impulses from CNS to the cell body
- one long axon that carries nerve impulses from the cell body to effector cells
explain the structure and the function of relay neurones
relay neurones
- many short dendrites carry nerve impulses from sensory neurones to cell body
- an axon that carries nerve impulses from cell body to motor neurones
explain the structure and the function of sensory receptors
groups of cells that can detect a change in you environment (stimulus), a stimulus is detected by receptors and the information is converted to nervous (electrical) impulses and sent to sensory neurones to the CNS.
explain the structure and the function of synapses in the transmission of electrical impulses
- synapse = a connection between two neurones
1. nerve signal is transferred to chemicals called neurotransmitters which diffuse across the gap
2. neurotransmitters set off electrical signals in next neurone
transmission of a nervous impulse is very fast but is slowed down at the synapse because the diffusion of neurotransmitters across the gap takes time
explain the structure and the function of an axon, dendron, myelin sheath
axon = carries nerve impulses away from cell body
dendron = carry nerve impulses towards the cell body
myelin sheath = acts as an electrical insulator speeding up electrical impulses, often surround axons
explain the structure and the function of neurotransmitters
- a chemical that transferrers nerve signals
explain the structure and the function of relay neurones in the CNS
- impulses travel through CNS along relay neurones
Explain the structure and function of a reflex arc including
sensory, relay and motor neurones
reflex arc = passage of information in a reflex (from receptor to effector)
1. stimulus detected by receptors, impulses sent along a sensory neurone to a relay neurone in the CNS
2. when impulses reach a synapse between the sensory and relay neurone they trigger neurotransmitters to be released, these cause impulses to be sent along relay neurone
3. when impulses reach synapse between the relay neurone and the motor neurone, same thing happens. neurotransmitters are releases and cause impulses to be sent along the motor neurone
4. impulses travel along motor neurone to the effector
5. muscle contract
6. you don’t spend time thinking about a response so its quicker than normal responses
what is a synapse
connection between two neurones
prophase - chromosomes condense, membrane around nucleus breaks down and chromosomes lie free in cytoplasm
