cells and control Flashcards
What are cells which possess both pairs of chromosomes called
Diploid
What are cells that only contain one pair of chromosomes called?
Haploid cells (eg. sex cells, gametes)
How do chromosomes divide?
-start as a parent chromosome
-split into 2 identical copies (sister chromatoids) but are still attached together at the centre
-sister chromatoids spilt apart and are now called daughter chromosomes
how is cancer caused
some cells lose control of their cell cycle and keep rapidly dividing, producing masses of undifferentiated cells (tumours).
Tumours may spread and destroy organs
how to treat cancer
-cut out the tumour if possible
-chemotherapy (take drugs which are toxic to rapidly dividing cells)
-radiotherapy
what is a zygote
fertilised egg cell
how does an egg develop into an adult
-egg cell is fertilised
-egg cell goes through mitosis, producing undifferentiated cells (embryo)
-cells in embryo switch in genes to differentiate into specialised cells
what is a plant meristem
-groups of undifferentiated cells at the tips of roots/shoots
-allow the plant to grow until death
where are the xylem and phloem in
vascular bundle (shoot)
what does xylem do
carry water from roots to stem and leaves.
comprised of dead cells
what does phloem do
transport dissolved sugars from leaves to where the plant needs it for growth or other processes
what is a stem cell
an unspecialised cell that produces a different type of specialised cell
what are synapses
junctions where neurones communicate with eachother
Pros and cons of asexual reproduction
No mate needed
Energy efficient
BUT
Offspring are genetically identical and equally susceptible to disease
How are the stomata adapted to help the plant survive
Allow CO2 to diffuse into the leaf
Close at night to save water in the leaf
What two organs form the CNS
Brain
Spinal Chord
What are effectors
Muscles and glands
They respond to electrical impulses from neurones
Define neurones
Cells which carry info around the body as electrical impulses
Define nerves
Clumps of neurones
Define stimuli for nerves
A change in the external environment
How do motor neurones look
A ‘star’ shape on top of a long chain of cells
How do motor neurones look
A large cell protruding out from a chain of smaller cells
What are dendrons/ites
Branches that extend out from motor neurones, allowing electrical signals to be recievef
What are axons in nerves
The long part in the middle of nerve cells
They allow electrical signals to pass through the neurone
What is the purpose is sensory neurones
Detect stimuli and send electrical signals to the rest of the nervous system
What is the purpose of motor neurones
transmit impulses from the spinal cord to muscles and glands
what is the purpose of synapses
The junction between 2 neurones that allows electrical impulses to pass between them
They slow down electrical signals which ensures that they only travel in one direction
What are reflex actions
Involuntary actions that keep us safe
They are automatic and do not rely on the brain
What happens when pain triggers a reflex arc
Pain stimulates pain receptors
Sensory neurones receive signal and send it along CNS
Signal travels from sensory to relay neurone via synapses
Signal travels from relay to motor neurones via synapses
Signal travels from motor neurone to effector
REFLEX ACTION OCCURS
Why are reflex arcs so fast
Signals pass through the relay neurone in the spinal chord rather than having to travel to the brain
What is a plant meristem
regions of unspecialised cells in plants that are capable of cell division
What is cell elongation in plants
PLANT CELLS become longer
Where are meristems in plants
Root tips
Shoot tips
